# data[].attributes.attachment_link.readable_text
La madera maciza (o Mass Timber) está siendo aclamada como la solución al urgente problema de la sostenibilidad en la arquitectura: que los edificios representen casi el 40% del gasto energético global es un dato conocido. Pero la madera no es el único material renovable del mundo, y los arquitectos e ingenieros han comenzado a buscar en otros lugares posibles reemplazos del acero y el concreto. Una de las opciones que ha salido a la luz recientemente es el bambú laminado o de ingeniería, un material altamente sostenible y estructuralmente impresionante. A continuación, investigamos cómo se fabrica, cuáles son sus cualidades principales y cómo se compara con la madera.

+ 10

Habitualmente llamado Laminated Bamboo Lumber o LBL, este material compuesto se considera como una alternativa estructural viable debido a las cualidades naturales del bambú. Con una tasa de crecimiento más rápida y un ciclo de cosecha más corto que la madera, se dice que los bosques de bambú presentan hasta cuatro veces la densidad de carbono por hectárea de los bosques de abetos. Además, generalmente el bambú crece en partes del mundo con recursos madereros más limitados, lo que lo convierte en una mejor opción para ciertas áreas que, en consecuencia, evitan los problemas del transporte de la madera y, por lo tanto, reducen sus costos y su uso energético.

Como material estructural, las propiedades del LBL varían según la forma en que se procesa. En general, el material está diseñado mediante la combinación de caña de bambú en bruto con un compuesto laminado. Sin embargo, existen tres métodos principales de fabricar el LBL. El primero utiliza trituradoras de rodillos para aplanar y suavizar el culmo hasta formar esteras más planas. Estas se apilan y se adhieren entre sí para crear un panel. Otro método procesa los tallos de bambú a través de una máquina divisora, creando hebras que luego se juntan y pegan, mientras que un tercer métido consiste en cortar cada culmo por la mitad, para luego aplanarlos y pegarlos. Todas estas opciones fueron probadas y comparadas en una investigación de 2011 para el Journal of Materials in Civil Engineering, concluyendo que el tercer métido es el más rentable y la opción más eficiente para aplicaciones estructurales. Esta conclusión deriva de la mayor estabilidad dimensional y resistencia flexional (o módulo de ruptura) del material resultante, aunque se consideraron varias propiedades diferentes.

En comparación con la madera, el bambú estructural es sorprendentemente fuerte, con una capacidad estructural hasta tres veces mayor que la madera común. A pesar de esto, siguen existiendo algunas preocupaciones sobre su resistencia, ya que se descompone más rápidamente que la madera si no es tratado con los conservantes adecuados.

Además, el costo del LBL puede variar mucho según su ubicación. Para áreas con bosques locales de bambú, los beneficios económicos son inmensos. Sin embargo, en lugares como los Estados Unidos, los costos de envío asociados con el transporte del bambú aumentan su costo hasta cuatro veces más que la madera convencional. Además, los beneficios de sostenibilidad disminuyen significativamente cuando se necesita mover grandes cargas de bambú por todo el mundo.

Si bien la literatura sobre el bambú estructural sigue siendo escasa, parece una alternativa prometedora frente los materiales de construcción convencionales, altamente contaminantes. Y aunque esperamos el surgimiento de nuevas y más investigaciones sobre el tema, los estudios existentes parecen sugerir que cuando se considera la ubicación, la producción y la preservación, el bambú laminado puede ser un fuerte contendiente para la madera maciza actualmente en desarrollo.
Artículos Relacionados

# data[].attributes.attachment_link.title
¿Qué tan efectivo es el bambú laminado en aplicaciones estructurales?

# data[].attributes.attachment_link.description
La madera maciza (o Mass Timber) está siendo aclamada como la solución al urgente problema de la sostenibilidad en la arquitectura: que los edificios representen casi el 40% del gasto energético global es un dato conocido.

# data[].attributes.attachment_link.readable_text
Structural engineers have built a new bridge using an unfolding, umbrella-like technique.

The engineers say the process is ideal for unusual terrain and reduces time and cost.

Hollow steel girders are lowered slowly and steadily into place by a hydraulic lift.

A new kind of bridge construction opens and unfolds like an umbrella, creators say. Structural engineers at the TU Wien, or Vienna University of Technology, have built a prototype bridge mechanism with a central umbrella handle and two opposite spokes controlled by a slider. The example bridge spans a river in Austria.

The umbrella method is a completely new way to construct a static final bridge. This TU Wien team first worked on the idea in 2006, and it's been experimenting and fine tuning since then. Instead of traditional kinds of bridge building-i.e. putting up long-term scaffolding as rebar is laid and concrete is filled into structures-this mechanism is built like a "closed" umbrella and then unfolded into its final position. From there, its hollow girders are filled with concrete and the rest of the structural elements are completed.

"Erecting bridges using scaffolding usually takes months," designer Johann Kollegger said in a statement. "The elements for the balanced lowering method, on the other hand, can be set up in two to three days, and the lowering process takes around three hours." But this process, he says, is less invasive for bridges through protected or uneven terrain. The team's sample bridge over the Lafnitz River touches a nature preserve.

The resulting bridge section has a span of 72 meters (about 236 feet)-enough to span many rivers and highways. Sections can also be daisy-chained and connected into longer bridges. Each girder weighs over 50 tons, and they're lowered carefully and symmetrically over a pretty long time. Traditionally constructed bridges are also often built out symmetrically, because even small imbalances can break the foundations that have been constructed.

Using hydraulics ensures the heavy girders are lowered at a totally even and steady rate, and once the girders are nestled in place, the hollow steel construction is filled with concrete. Kollegger says the bridges that result from this process are as strong or even stronger than traditional bridges.

It makes intuitive sense, too. Construction with fewer, longer pieces leaves less to chance in the form of joins and other added labor.

There's one more "horizontal" traditional approach with a similar kind of outcome. Some bridges are constructed by building the vertical supports and then slowly scooting an almost-completed deck across the top. In that case, the surface is made of just one piece that can be fully assembled off to the side or assembled in situ as portions pass through a construction zone before being scooted.

The TU Wien statement doesn't say this explicitly, but this technique seems like it could improve construction on some of the scariest bridges, like those that go a short distance across an extremely deep ravine, for example. (Think: in the narrow gauge railroads of the high Himalayan Mountains, or the rapidly expanding railroads and highways of southern China.) The perilous-looking, partly completed bridge in Wulong County in Chongqing shows the symmetrical construction method in progress.

Imagine if the only moving part here was an autonomous hydraulic lift, after which you'd already have a basically safe and completed bridge ready to fill in and finish. If the science, well, holds up, these projects could take much less time and money and be much safer for workers.

# data[].attributes.attachment_link.title
This Is a Completely New, Possibly Perfect Way to Build Bridges

# data[].attributes.attachment_link.description
Structural engineers have built a new bridge using an unfolding, umbrella-like technique. The engineers say the process is ideal for unusual terrain and reduces time and cost. Hollow steel girders are lowered slowly and steadily into place by a hydraulic lift. A new kind of bridge construction opens and unfolds like an umbrella, creators say.

# data[].attributes.attachment_link.readable_text
La crisis climática global no sólo nos está obligando a repensar los diseños arquitectónicos y la forma en qué vivimos, sino también los materiales y productos que le dan forma, desde su fabricación y sus orígenes. En esta dirección, la madera se ha transformado en una alternativa eficiente frente al acero y el hormigón -materiales de alto nivel de carbono incorporado -, surgiendo interesantes innovaciones que podrían continuar potenciando su uso masivo.

Inspirados por la eficiencia de la naturaleza, Strong By Form ha desarrollado Woodflow, una tecnología que permite generar piezas de madera de alta performance estructural, "combinando la optimización de su forma, la orientación de sus fibras en relación a la dirección de los esfuerzos, y variando su densidad para resistir mejor compresión o tracción", como explican sus creadores. Además, todos estos productos son desarrollados en un proceso controlado a través de software paramétricos, integrados a plataformas BIM y sistemas de fabricación CNC.

Conversamos con Jorge Christie, CTO de Strong By Form, para profundizar en esta nueva tecnología.
¿Qué es Strong by Form y de donde nace la inspiración para su desarrollo?
Strong by Form es una empresa enfocada en producir materiales y productos estructurales sustentables de alta performance, que ofrezcan una alternativa real de reemplazo a materiales altamente contaminantes como aluminio, acero u hormigón. Hoy en día la industria de la construcción es responsable de cerca de un 40% de las emisiones de CO2 y de un 40% del consumo de materias primas a nivel global. Nuestra meta es contribuir a disminuir al máximo esas cifras y al mismo tiempo aumentar la productividad de la industria. La inspiración de nuestros desarrollos se encuentra en los patrones de eficiencia que se pueden observar en la naturaleza.

En el caso particular de la tecnología Woodflow, nuestro referente son los propios árboles. Estas estructuras naturales, logran su alta performance estructural combinando la optimización de su forma, la orientación de sus fibras en relación a la dirección de los esfuerzos, y a la variación de su densidad para resistir mejor compresión o tracción. Gran parte de esa inteligencia natural se pierde cuando se aserra o procesa el árbol para la producción de productos madereros. Nuestra intención es traer de vuelta esta eficiencia a la madera de ingeniería y así conseguir máxima performance con mínimo material.

¿Cuáles son los componentes desarrollados hasta el momento y cómo funcionan?
Hoy nos encontramos en un proceso de desarrollo de productos que permitan incorporar madera donde hoy no se utiliza o donde -gracias a las características freeform de nuestra tecnología- podamos producir ahorros de material significativos.

Actualmente, estamos desarrollando junto a una constructora alemana, una losa compuesta Woodflow-hormigón, que utiliza la madera, al mismo tiempo, como moldaje del hormigón y como elemento de refuerzo a tracción. Esto, estimamos, permitirá ahorrar hasta un 70% en volumen de madera y 30% en volumen de hormigón, comparado con losas compuestas madera-hormigón tradicionales. Esta reducción significativa de su peso, permite su prefabricación y la reducción de los costos en transporte, ensamblaje y fundaciones del edificio. Todos estos beneficios apuntan a traducirse en un impacto positivo en el costo de la vivienda.

Otros productos en los que estamos trabajando son, por ejemplo, nudos rígidos en madera; que permiten realizar uniones mecánicamente más consistentes (100% madera), más livianas y menos susceptibles a rasgaduras; moldajes freeform y aplicaciones para cáscaras estructurales ultraligeras.
¿Porqué es posible considerar a Woodflow como un material/producto sostenible?
Strong by Form es una empresa que nace con el objetivo de desarrollar tecnologías que nos permitan desarrollarnos "con" el medio ambiente y no "a pesar" de este. Nuestra apuesta por productos sostenibles tiene varios frentes. Primero, utilizamos materias primas renovables. Si bien ahora estamos trabajando con madera -cuyas ventajas de captura de CO2 son conocidas- nuestro objetivo es ampliarnos a otras fibras vegetales. Esta versatilidad, nos permitirá desarrollar productos basados en materias primas locales, que activen sinergias económicas y sociales.

Segundo, creemos que la madera, el hormigón o cualquier otro material de construcción, son bienes preciosos y escasos que hay que utilizar de forma ultra eficiente. Por ello, al igual que la naturaleza, utilizamos formas complejas y materiales personalizados para lograr máxima performance con el mínimo material. Como ejemplo, recientemente desarrollamos un prototipo tipo puente, que con solo 4 mm de espesor y 854 gramos de peso, resistió más de 300 kg de carga con mínima deflexión.

Por último, nuestra tecnología se basa en manufactura aditiva en base a refuerzos discretos, lo que permite, por una parte, minimizar producción de desechos y, por otra, incorporar gran parte de material reciclado.
¿Qué posibilidades nuevas entregan a los arquitectos y cómo podrían sumarse al resurgimiento de la madera para la construcción masiva y en altura, liderada por los productos 'Mass Timber'?
Una particularidad de nuestra tecnología es que se basa en una plataforma Design-to-manufacturing. Esto quiere decir que controlamos el proceso desde el diseño del componente hasta la producción, pasando por la definición de la arquitectura de las fibras del material. Este software "paramétrico", permite su integración con plataformas de diseño BIM y con cualquier sistema productivo CNC. Nuestra visión es que a través del desarrollo de plugins BIM, los arquitectos podrán explorar la aplicación de nuestros productos en sus diseños y que vía cloud puedan conectarse a nuestros servidores para obtener la memoria estructural, costos o eventualmente realizar la orden de compra-fabricación de forma directa.

Estamos convencidos que el futuro de la construcción va hacia la integración de la cadena completa de diseño, ingeniería, fabricación y construcción, y donde las tecnologías computacionales -hoy emergentes- nos permitirán construir de forma más eficiente, más sustentable y con mejor productividad.

Encuentra más detalles aquí.

# data[].attributes.attachment_link.title
Piezas estructurales y ligeras de madera basadas en la inteligencia natural de los árboles

# data[].attributes.attachment_link.description
La crisis climática global no sólo nos está obligando a repensar los diseños arquitectónicos y la forma en qué vivimos, sino también los materiales y productos que le dan forma, desde su fabricación y sus orígenes.

# data[].attributes.attachment_link.provider_name
designboom | architecture & design magazine

# data[].attributes.attachment_link.title
zaha hadid architects' timber stadium receives planning permission

# data[].attributes.attachment_link.description
zaha hadid architects (ZHA) plans for the 'eco-park' development have been approved, including a timber stadium to be made almost entirely out of wood.

# data[].attributes.attachment_link.readable_text
Bridges are designed for connection. Spanning two worlds, they have been created as both symbolic and utilitarian artifacts throughout history. By definition, a bridge is designed to provide passage over an obstacle, though they can also be made for purely experiential reasons. Formed from natural or manmade materials, they have been built since modern civilizations started rising in Mesopotamia. As a balance between engineering and art, bridges echo the process of architectural design.

Looking at bridges through the lens of architectural practice, the following section drawings are rooted in a spatial understanding. Formed as a series of moments, the bridges are considered in sequence and how they will be experienced by people. Made with a range of forms, programs and structural approaches, the designs bring space and function together in built form. In turn, they showcase the universal adoption of bridges across the world.

Tanderrum Pedestrian Bridge by NADAAA, Inc. and John Wardle Architects, Melbourne, Australia

The new Tanderrum Pedestrian Bridge linking Birrarung Marr with the Melbourne Park sports precinct creates a new arrival address for Melbourne Park. A ramping pathway through Birrarung Marr leads to the bridge proper and its alignment respects the established bridges and landscape topography of the park. The bridge design is slender, a flat steel girder structure that tapers at its edges to achieve the required span across Batman Avenue. The bridge undercroft follows the slope of the existing landscape thus eliminating low forming spaces and settles the bridge into the landscape. The lightweight filigree character of the steel structure provides the framework for a journey which branches into a connective path to Middle Terrace and provides views through toward the Yarra River, Birrarung Marr and the city.

The pedestrian bridge between the Metro station and the Bois de Sauvabelin creates a connection between the urban plateau and the artificial natural landscape of le Vallon. The duality of different geometries at the location, the quadrangular construction on the square compared to the so-called "natural" character of le Vallon, becomes a leitmotif for the bridge construction. Depending on the perception from the different perspectives, the design presents its play of criss-crossing lines between the square and the street, thereby shifting them together into a characteristic form.

Designed to be constructed without the use of mechanical fasteners, "Wind and Rain Bridge" is a reciprocal interlocking timber structure which draws on the long tradition of wooden buildings native to the region. Each of the bridges' 265 elements is unique and integral, assembled under the supervision of traditional carpenters - some of the few remaining of their craft. The bridge creates a community space in the heart of the village's fertile farmland, where local people can socialize and exchange.

The Bridge of Aspiration provides the dancers of the Royal Ballet School with a direct link to the Grade I listed Royal Opera House. The design addresses a series of complex contextual issues, and is legible both as a fully integrated component of the buildings it links and as an independent architectural element. The skewed alignment and different levels of the landing points dictate the form of the crossing, which is geometrically and structurally simple. A concertina of 23 square portals with glazed intervals are supported from an aluminium spine beam. These rotate in sequence for the skew in alignment, performing a quarter-turn overall along the length of the bridge.

La Passerelle de la Paix is a new bridge for pedestrians and cyclists over the Rhone in Lyon, and it reveals the landscape and urban changes in the region. This portion of the river is part of the development of the city to the north. The footbridge links the conference center "Cité Internationale" and the district of St. Clair as well as two major parks on each side of the river, forming a landmark that is first seen from the high-speed rail track entering Lyon. The bridge crosses the river with a span of just over 500 feet. Two cantilevers built from a three-dimensional asymmetric tube structure join in the middle of the river.

This bridge combines a foot and cycle bridge, with three decks connecting different banks. When both doors are open at the same time, they form a butterfly. The link across Christianshavns Kanal and Trangraven is designed as three linear bridge spans that meet above the water's surface in a star shape. The canal bridge design is adapted to the individual canal scenario. Two of the spans can be opened independently of each other. When the moving spans are up they serve as barriers which means that the bridge always functions to and from Islands Plads. The main structure of the steel bridge consists of a single-web, continuous T-beam. The beam web, which extends over the entire bridge, is trapezoidal, and the bridge deck is composed of an orthogonal anisotropic plate construction.

Located in the Menteng Tenggulun village, this brige is part of the modernization of Indonesia's capital city, Jakarta. The bridge has a span of 30 meters connecting the Menteng Tenggulun village with Sultan Agung street separated by Ciliwung river in the Manggarai area. The area was first connected by "eretan" boats since 1965, functioning as villagers' access for crossing to Sultan Agung street. The form of this bridge's architecture was created through the fusion of lines on the outer appearance of the bridge with steel pipes.

This project was designed to link two public buildings with a bridge-type facility, which had been long separated by the road in between. The museum bridges communications in this area. It functions not only as a passage between the two facilities but also as an accommodation and workshop, an ideal location for artist-in-residence programs. In this project, the team challenged a structural system which composes of small parts, referring to cantilever structure often employed in traditional architecture in Japan and China.
Architects: Showcase your next project through Architizer and sign up for our inspirational newsletter.

# data[].attributes.attachment_link.title
8 Section Drawings That Demonstrate the Structural Ingenuity of Modern Bridges - Architizer Journal

# data[].attributes.attachment_link.description
Bridges are designed for connection. Spanning two worlds, they have been created as both symbolic and utilitarian artifacts throughout history. By definition, a bridge is designed to provide passage over an obstacle, though they can also be made for purely experiential reasons.

# data[].attributes.headline
UNIONES METALICAS PARA ESTRUCTURAS DE MADERA, IMPRESAS EN 3D

# data[].attributes.subject
UNIONES METALICAS PARA ESTRUCTURAS DE MADERA, IMPRESAS EN 3D

# data[].attributes.attachment_link.provider_name
designboom | architecture & design magazine

# data[].attributes.attachment_link.title
MX3D + takenaka utilize robotic 3D printing to build a structural steel connector

# data[].attributes.attachment_link.description
the joint has a hollow structure that is then filled with concrete post-print by takenaka engineers, providing a more economical solution.

# data[].attributes.attachment_link.readable_text
The National Transportation Safety Board determined, during a public board meeting held Tuesday, that load and capacity calculation errors made by FIGG Bridge Engineers, Inc., are the probable cause of the fatal, March 15, 2018, Florida International University pedestrian bridge collapse in Miami.

Contributing to the collapse was Louis Berger's inadequate peer review, which failed to detect FIGG's calculation errors in its design of the main span truss member 11/12 nodal region and connection to the bridge deck. The FIGG engineer of record's failure to identify the significance of structural cracking observed in this node before the collapse, and failure to obtain an independent peer review of the remedial plan to address the cracking, further contributed to the collapse.

Six people died and 10 others were injured when the partially constructed FIU pedestrian bridge catastrophically failed, sending the 174-foot-long, 950-ton, bridge span onto SW 8th Street 18.5 feet below, crushing eight vehicles that were under the bridge. Six of the eight lanes of the roadway traveling under the bridge were open at the time of the collapse.

The failure of FIGG, MCM, Bolton Perez and Associates Consulting Engineers, FIU and the Florida Department of Transportation to cease bridge work and close SW 8th Street to protect public safety contributed to the severity of the collapse outcome, said the NTSB during the meeting.

"Errors in bridge design, inadequate peer review and poor engineering judgment led to the collapse of this bridge," said NTSB Chairman Robert Sumwalt. "The failure of all concerned parties, to recognize and take action on the threat to public safety presented by the significant observed bridge structure distress prior to the collapse, led to the tragic loss of life in this preventable accident."

Through its investigation the NTSB made 30 findings including:

Concrete and steel materials used during construction of the bridge were not a factor in its collapse and the hydraulic jack used to post-tension the steel rods in member 11 was operating as expected at the time of the collapse.

The restressing of member 11 was a manipulation of loads to address structural cracking of unknown origination constituting a change to the FIGG design and should have been independently reviewed by a professional engineer before being implemented.

FIGG's bridge design was nonredundant because it provided only a singular load path.

FIGG's construction plans inconsistently identified when intentionally roughened surfaces were needed to fulfill assumptions of the bridge design.

Even if the cold joint surface of nodal region 11/12 had been roughened to a 0.25-inch amplitude, node 11/12 would not have had sufficient capacity to counteract the demand load for interface shear - and the bridge would still have been under-designed and could have failed.

The rate of premature concrete distress was clear evidence the structure was progressing toward failure and should have alerted FIGG and MCM to the origin of the distress.

Louis Berger was not qualified by the Florida Department of Transportation to conduct an independent peer review.

Florida Department of Transportation should have verified Louis Berger's qualifications as an independent peer review firm as part of FDOT's oversight of local agency program projects.

Based on its investigation of the bridge collapse, the NTSB issued 11 safety recommendations in total, with one issued to the Federal Highway Administration, five issued to the Florida Department of Transportation, three issued to the American Association of State Highway and Transportation Officials, and two issued to FIGG Bridge Engineers, Inc.

An abstract of the NTSB's report containing the probable cause, findings and recommendations from its investigation of the FIU pedestrian bridge collapse is available online at https://go.usa.gov/xp3uB. The full final report will publish in the next few weeks.

Previously released information about the NTSB's investigation of the FIU pedestrian bridge collapse is available at http://go.usa.gov/xVRrv.

# data[].attributes.attachment_link.title
NTSB announces probable cause of Florida International University pedestrian bridge collapse | Civil + Structural Engineer magazine

# data[].attributes.attachment_link.description
The National Transportation Safety Board determined, during a public board meeting held Tuesday, that load and capacity calculation errors made by FIGG Bridge Engineers, Inc., are the probable cause of the fatal, March 15, 2018, Florida International University pedestrian bridge collapse in Miam ...

# data[].attributes.attachment_link.readable_text
In the early 1500s, Leonardo da Vinci designed a hypothetical bridge for the Sultan of the Ottoman Empire. It was rejected.

Over 500 years later, an MIT team has recreated the design with a model and have showed that it would have worked.

Da Vinci's design incorporates architectural techniques that would have not been seen for another 300 years.

Researchers at MIT have proven Leonardo da Vinci correct yet again, this time involving his design for what would have been at the time a revolutionary bridge design. Although clients rejected da Vinci's work at the time, over 500 years later, the researchers have proven that his bridge would have worked.

The famed Renaissance Man made his living working with wealthy patrons-people like Ludovico Sforza, the Duke of Milan, who commissioned his painting "The Last Supper." But da Vinci did not want to limit himself to Italian patrons. When Sultan Bayezid II of the Ottoman Empire put out a request for proposals for a bridge connecting capital city Constantinople (now Istanbul) with its neighbor city Galata, da Vinci was eager for the chance to win the contract.

Da Vinci's proposal was radically different than the standard bridge at the time. As described by the MIT group, it was approximately 918 feet long (218 meters, though neither system of measurement had been developed yet) and would have consisted of a flattened arch "tall enough to allow a sailboat to pass underneath with its mast in place...but that would cross the wide span with a single enormous arch," according to an MIT press statement. It would have been the longest bridge in the world at the time by a significant measure, using an unheard of style of design.

It wasn't just length or style that set da Vinci's bridge apart. It also had safety features unheard of at the time. One of the biggest challenges facing any bridge design is that it has to exist in nature no matter the conditions, including wind.

Strong winds have forced many bridge, including relatively modern bridges from the 20th century, into lateral oscillations leading to collapse. Da Vinci would have added what are known as wing walls, abutments out to the side of the bridge, steadying it during harsh conditions. They are now common design elements of modern bridges.

"It's incredibly ambitious," says recent graduate student Karly Bast, who worked on the project with professor of architecture and of civil and environmental engineering John Ochsendorf and undergraduate Michelle Xie on the project. "It was about 10 times longer than typical bridges of that time."

Bast, Oschsendorf, and Xie analyzed available documents regarding the bridge, the possible materials and construction methods of the period, and the geographic conditions of the river estuary then known as the Golden Horn, now called Haliç, where the Sultan wanted the bridge.

Da Vinci's sketches and letters to the Sultan regarding the bridge can be found in what's known as Manuscript L, a small Codex stored in the Institut de France in Paris. Da Vinci wrote that

I, your faithful servant, understand that it has been your intention to erect a bridge from Galata (Pera) to Stambul... across the Golden Horn ('Haliç"), but this has not been done because there were no experts available. I, your subject, have determined how to build the bridge. It will be a masonry bridge as high as a building, and even tall ships will be able to sail under it.

He does not specify what materials he would need, but the team assumed that da Vinci was talking about stone-neither wood or brick would have been able to sustain a bridge of that size at the time. The word "masonry" also tipped off the team to a design strategy. Like the classic masonry bridges of ancient Rome, with which da Vinci would have been familiar, it would stand solely through the forces of physics and gravity with no need for fasteners or mortar.

Since building a full-scale bridge would have been unwieldily, the team resorted to building a model. Using 126 blocks, they built the bridge at a scale of 1 to 500, making it around three feet long.

"It was time-consuming, but 3-D printing allowed us to accurately recreate this very complex geometry," Bast says. Da Vinci's design is well-known among historians, and has even inspired a modern bridge in Norway. But being inspired is different than proving the original design correct.

"It's the power of geometry."

"That was not a test to see if his design would work with the technology from his time," Bast says. The model is "held together by compression only. We wanted to really show that the forces are all being transferred within the structure."

The crucial moment came, as it does in projects like these, with the adding of the keystone.

"When we put it in, we had to squeeze it in. That was the critical moment when we first put the bridge together. I had a lot of doubts," Bast recalls. But "when I put the keystone in, I thought, 'this is going to work.' And after that, we took the scaffolding out, and it stood up."

"It's the power of geometry" that makes it work, she says. "This is a strong concept. It was well thought out." Further tests showed that the bridge could have even stood its own against earthquakes to an extent far beyond other bridges at the time.

There are still mysteries surrounding the project. "Was this sketch just freehanded, something he did in 50 seconds, or is it something he really sat down and thought deeply about? It's difficult to know."

While it's difficult to know da Vinci's intentions, one thing is now relatively certain: the bridge would have worked.

# data[].attributes.attachment_link.title
500 Years Later, MIT Proves That Da Vinci's Bridge Design Works

# data[].attributes.attachment_link.description
In the early 1500s, Leonardo da Vinci designed a hypothetical bridge for the Sultan of the Ottoman Empire. It was rejected. Over 500 years later, an MIT team has recreated the design with a model and have showed that it would have worked.

# data[].attributes.attachment_link.readable_text
When the Los Alamos researchers probed those inner workings of their algorithm, what they learned surprised them. The statistical feature the algorithm leaned on most heavily for its predictions was unrelated to the precursor events just before a laboratory quake. Rather, it was the variance - a measure of how the signal fluctuates about the mean - and it was broadcast throughout the stick-slip cycle, not just in the moments immediately before failure. The variance would start off small and then gradually climb during the run-up to a quake, presumably as the grains between the blocks increasingly jostled one another under the mounting shear stress. Just by knowing this variance, the algorithm could make a decent guess at when a slip would occur; information about precursor events helped refine those guesses.

The finding had big potential implications. For decades, would-be earthquake prognosticators had keyed in on foreshocks and other isolated seismic events. The Los Alamos result suggested that everyone had been looking in the wrong place - that the key to prediction lay instead in the more subtle information broadcast during the relatively calm periods between the big seismic events.

To be sure, sliding blocks don't begin to capture the chemical, thermal and morphological complexity of true geological faults. To show that machine learning could predict real earthquakes, Johnson needed to test it out on a real fault. What better place to do that, he figured, than in the Pacific Northwest?

Out of the Lab

Most if not all of the places on Earth that can experience a magnitude 9 earthquake are subduction zones, where one tectonic plate dives beneath another. A subduction zone just east of Japan was responsible for the Tohoku earthquake and the subsequent tsunami that devastated the country's coastline in 2011. One day, the Cascadia subduction zone, where the Juan de Fuca plate dives beneath the North American plate, will similarly devastate Puget Sound, Vancouver Island and the surrounding Pacific Northwest.

The Cascadia subduction zone stretches along roughly 1,000 kilometers of the Pacific coastline from Cape Mendocino in Northern California to Vancouver Island. The last time it breached, in January 1700, it begot a magnitude 9 temblor and a tsunami that reached the coast of Japan. Geological records suggest that throughout the Holocene, the fault has produced such megaquakes roughly once every half-millennium, give or take a few hundred years. Statistically speaking, the next big one is due any century now.

That's one reason seismologists have paid such close attention to the region's slow slip earthquakes. The slow slips in the lower reaches of a subduction-zone fault are thought to transmit small amounts of stress to the brittle crust above, where fast, catastrophic quakes occur. With each slow slip in the Puget Sound-Vancouver Island area, the chances of a Pacific Northwest megaquake ratchet up ever so slightly. Indeed, a slow slip was observed in Japan in the month leading up to the Tohoku quake.

For Johnson, however, there's another reason to pay attention to slow slip earthquakes: They produce lots and lots of data. For comparison, there have been no major fast earthquakes on the stretch of fault between Puget Sound and Vancouver Island in the past 12 years. In the same time span, the fault has produced a dozen slow slips, each one recorded in a detailed seismic catalog.

That seismic catalog is the real-world counterpart to the acoustic recordings from Johnson's laboratory earthquake experiment. Just as they did with the acoustic recordings, Johnson and his co-workers chopped the seismic data into small segments, characterizing each segment with a suite of statistical features. They then fed that training data, along with information about the timing of past slow slip events, to their machine learning algorithm.

After being trained on data from 2007 to 2013, the algorithm was able to make predictions about slow slips that occurred between 2013 and 2018, based on the data logged in the months before each event. The key feature was the seismic energy, a quantity closely related to the variance of the acoustic signal in the laboratory experiments. Like the variance, the seismic energy climbed in a characteristic fashion in the run-up to each slow slip.

The Cascadia forecasts weren't quite as accurate as the ones for laboratory quakes. The correlation coefficients characterizing how well the predictions fit observations were substantially lower in the new results than they were in the laboratory study. Still, the algorithm was able to predict all but one of the five slow slips that occurred between 2013 and 2018, pinpointing the start times, Johnson says, to within a matter of days. (A slow slip that occurred in August 2019 wasn't included in the study.)

For de Hoop, the big takeaway is that "machine learning techniques have given us a corridor, an entry into searching in data to look for things that we have never identified or seen before." But he cautions that there's more work to be done. "An important step has been taken - an extremely important step. But it is like a tiny little step in the right direction."

Sobering Truths

The goal of earthquake forecasting has never been to predict slow slips. Rather, it's to predict sudden, catastrophic quakes that pose danger to life and limb. For the machine learning approach, this presents a seeming paradox: The biggest earthquakes, the ones that seismologists would most like to be able to foretell, are also the rarest. How will a machine learning algorithm ever get enough training data to predict them with confidence?

The Los Alamos group is betting that their algorithms won't actually need to train on catastrophic earthquakes to predict them. Recent studies suggest that the seismic patterns before small earthquakes are statistically similar to those of their larger counterparts, and on any given day, dozens of small earthquakes may occur on a single fault. A computer trained on thousands of those small temblors might be versatile enough to predict the big ones. Machine learning algorithms might also be able to train on computer simulations of fast earthquakes that could one day serve as proxies for real data.

But even so, scientists will confront this sobering truth: Although the physical processes that drive a fault to the brink of an earthquake may be predictable, the actual triggering of a quake - the growth of a small seismic disturbance into full-blown fault rupture - is believed by most scientists to contain at least an element of randomness. Assuming that's so, no matter how well machines are trained, they may never be able to predict earthquakes as well as scientists predict other natural disasters.

"We don't know what forecasting in regards to timing means yet," Johnson said. "Would it be like a hurricane? No, I don't think so."

In the best-case scenario, predictions of big earthquakes will probably have time bounds of weeks, months or years. Such forecasts probably couldn't be used, say, to coordinate a mass evacuation on the eve of a temblor. But they could increase public preparedness, help public officials target their efforts to retrofit unsafe buildings, and otherwise mitigate hazards of catastrophic earthquakes.

Johnson sees that as a goal worth striving for. Ever the realist, however, he knows it will take time. "I'm not saying we're going to predict earthquakes in my lifetime," he said, "but ... we're going to make a hell of a lot of progress."

# data[].attributes.attachment_link.title
Artificial Intelligence Takes On Earthquake Prediction | Quanta Magazine

# data[].attributes.attachment_link.description
When the Los Alamos researchers probed those inner workings of their algorithm, what they learned surprised them. The statistical feature the algorithm leaned on most heavily for its predictions was unrelated to the precursor events just before a laboratory quake.

# data[].attributes.attachment_link.readable_text
El hormigón, material de construcción por excelencia, nos ha ofrecido por décadas la posibilidad de dar forma a nuestras ciudades de forma rápida y efectiva, extendiéndose rápidamente hacia las periferias urbanas o alcanzando alturas antes impensadas por la humanidad. En la actualidad, las nuevas tecnologías en madera están comenzando a entregar oportunidades similares -e incluso superiores- a las proporcionadas por el concreto, entre ellas, la madera laminada cruzada (también llamada madera contralaminada o CLT).

Con el objetivo de profundizar en sus propiedades y beneficios, conversamos con Jorge Calderón, Diseñador Industrial de la Pontificia Universidad Católica de Valparaíso y Gerente de CRULAMM, quién nos revela algunas de las prometedoras oportunidades que podría entregar el CLT a la arquitectura en el futuro.

+ 21

¿Cuál es la diferencia entre la madera laminada y el CLT?

La madera laminada es el resultado de la unión de tablas o láminas para conformar una sola unidad estructural, generando elementos lineales, curvos o rectos, pero siempre lineales. Con el CLT, en cambio, la unión de tablas en capas perpendiculares permite la fabricación de placas, planchas, o superficies, es decir, muros. Es un contrachapado hecho de tablas que permite alcanzar enormes dimensiones; de entre 2.40 m y 4.00 m de altura, y de hasta 12.00 metros de largo, o incluso más si se requiere.

Debido a la orientación en cruz de cada una de sus capas longitudinales y transversales, se reducen a un mínimo irrelevante los grados de contracción y dilatación de la madera a nivel de los tableros, mientras que la carga estática y estabilidad de la forma mejoran considerablemente. [1]

Para su traslado, las planchas son cortadas en piezas que permitan su desplazamiento por carretera, en contenedores o camiones de plataforma baja.

¿Cuál es el impacto ambiental del CLT?

El CLT comenzó a fabricarse en Austria, con el objetivo de reutilizar la madera de menor valor. En la actualidad, sin embargo, el uso de la madera, en general, está volviendo a ser un factor relevante dentro de la industria de la construcción por su impacto ambiental.

Generalmente diseñamos y construimos con hormigón, y la huella del hormigón es enorme en comparación con la madera. Por cada m3 de hormigón se emite a la atmósfera una tonelada de CO2. Cuando se construye con CLT, se utiliza "carbón secuestrado", ya que el árbol mientras crece, se alimenta de carbono. Por lo tanto, a pesar de toda la energía utilizada en el proceso de extracción y fabricación, la madera nunca llegará a igualar la cantidad de carbono que mantiene "secuestrado".

Comparación de los diversos soluciones constructivas en términos de consumo energético (GJ/m2) para su elaboración y producción [Holzbau, Rubner. Universidad de Trento, Italia]:

¿Cómo se comporta estructuralmente el CLT, en comparación con otros materiales?

Al CLT se le ha llamado "el hormigón del futuro" y en cierto sentido es cierto, ya que entrega -al menos- la misma resistencia estructural que el hormigón armado. Es un material con un alto grado de flexibilidad y que tiene que sufrir grandes deformaciones para romperse y colapsar, al contrario del hormigón. Por otro lado, 1 m3 de hormigón pesa aproximadamente 2.7 toneladas, mientras que 1 m3 de CLT pesa 400 kg, entregando la misma resistencia. Lo mismo ocurre con el acero.

En cuanto a sus propiedades físicas, para lograr el mismo grado de aislamiento que tiene un muro de CLT de 100 mm de espesor, por ejemplo, necesitaríamos construir un muro de hormigón de 1.80 m de espesor (relación de 1/18).

¿Cómo se comporta el CLT ante el fuego?

El fuego en la madera avanza a una razón de 0.7 a 0.8 milímetros por minuto. Si un muro de CLT tiene 100 mm, terminaría de consumirse luego de más de 2 horas, incluso si hablamos de madera no tratada. Este proceso de carbonización es la reacción natural del árbol para protegerse a sí mismo.

En relación al humo, principal causante de la muerte de personas en un incendio, este se mueve de una habitación a otras por todas las rendijas o espacios libres que resulten del encuentro de los distintos materiales. Construido correctamente, el CLT puede llegar a ser completamente hermético, por lo que es muy relevante la selección y manejo de todos aquellos elementos que conformen la estructura final, como herrajes, sellos, uniones, y otros. En relación a la resistencia de una construcción con CLT, podríamos atribuir un 90% de la responsabilidad a los herrajes y uniones, y un 10% a la madera misma.

¿Cómo proteger el CLT frente a las condiciones ambientales?

La humedad y la intemperie son algunos de los enemigos más importantes de la madera. La madera al exterior sufre, y como el CLT es un componente estructural, debemos protegerla para evitar su desgaste, corrosión, y colapso. Por un lado, podemos agregar nuevas capas de revestimiento sobre la madera, como fibrocemento, ladrillo, piedra, u otros, pero si se quiere dejar el CLT expuesto, existen una serie de protecciones y acabados que la protegen efectivamente.

Aceites vegetales y pinturas minerales pueden cumplir estos objetivos, aplicándose en una única pasada cada 5 años, garantizando incluso 25 años de protección sin desprendimiento ni decoloración.

Los aceites vegetales son recomendados para su uso en interiores, mientras que las pinturas minerales funcionan de mejor manera en exteriores, principalmente sobre muros. Estos productos, inoloros y de alto rendimiento, pueden ser aplicados por cualquier persona, siguiendo instrucciones básicas y tomando los cuidados necesarios.

Los paneles de CLT funcionan como piezas perfectas, con un alto nivel de precisión

Cuando comienza a fabricarse una obra en CLT, en la fábrica todo está completamente decidido y predeterminado, y no es posible realizar ajustes en obra. Entonces, más que constructores, las personas que trabajan en una obra en CLT son montajistas, que deben articular piezas virtualmente perfectas. El CLT se comporta con la precisión de un mueble, trabajando con márgenes de error de 2 milímetros.

Mientras la etapa de proyecto puede demorar un poco más, el montaje es de una velocidad sorprendente: en el caso de una casa de 200 m2, el montaje puede demorar 5 días y ocupar una mano de obra mínima (al rededor de 4 personas instruidas).

En relación a la normativa, existen en el mundo regulaciones que guían el trabajo de diseño y construcción con CLT, pero son la suma de diferentes aspectos presentes en las normas utilizadas habitualmente en obras de hormigón y madera laminada. En 2017, se publicó la norma actualmente utilizada en los Estados Unidos, que es simplemente un resumen de las normas europeas.

Recomendaciones de diseño y construcción

Como hemos dicho, es fundamental entender que todo el proceso previo a la construcción con CLT debe ser cuidadosamente desarrollado. El diseño, la planificación, y la colaboración permanente entre los distintos actores es fundamental, ya que la construcción misma será llevada a cabo tal como fue definida en las etapas anteriores.

Durante su fabricación, el CLT debe elaborarse con madera estructural -conociendo el grado estructural de cada tabla-, ya que la calidad del panel será el resultado de la calidad de las maderas utilizadas. Además, es necesario considerar que la alta precisión del CLT debe poder conjugarse con los cimientos que lo recibirán, evitando, por ejemplo, losas de hormigón que presenten imperfecciones. Incluso variaciones milimétricas podrían generar enormes dolores de cabeza durante su instalación.

Los paneles de CLT están permitiendo actualmente la construcción de edificios de hasta 30 pisos, en Canadá, y de hasta 40 pisos en Finlandia. El futuro es prometedor y seguiremos atentos a sus avances. Quizás en algunos años nuestras ciudades se vean inundadas por la calidez y la textura de la madera, cambiando además la manera en que se concibe el diseño y la construcción de nuestras obras.

[1] Exposición de Jorge Calderón dictada en el seminario inaugural del programa de difusión tecnológica "Proyectar, manufacturar y construir de forma sostenible con sistema de madera contralaminada (CLT)" | 07.11.2017. Disponible en Youtube.

# data[].attributes.attachment_link.title
¿Es la madera laminada cruzada (CLT) el hormigón del futuro?

# data[].attributes.attachment_link.description
El hormigón, material de construcción por excelencia, nos ha ofrecido por décadas la posibilidad de dar forma a nuestras ciudades de forma rápida y efectiva, extendiéndose rápidamente hacia las periferias urbanas o alcanzando alturas antes impensadas por la humanidad.

# data[].attributes.attachment_link.readable_text
Something Old and Something New

Mass timber is not a new idea, just a new name. Many people have heard the term "mass timber" batted around in the last few years, but not everyone has a clear understanding of what it means. Mass timber used to be referred to as "heavy timber" and the International Building Code (IBC) classifies it as Type IV construction.

Mass timber is a type of structure made up of big, fat pieces of wood that, unlike light wood frame construction, burn slowly. Because mass timber structures maintain their integrity during a fire without the need for layers of fire-resistant materials, they are suitable for larger buildings and the IBC recognizes that.

Timber buildings have been built for over 4,000 years - since bronze-age man developed the technology to forge sharp tools that could hew trees into square timbers and fashion mortise and tenon joints. Timber structures were the dominant construction type in Europe, Asia, and North America until 1850 when balloon-frame wood structures began to displace timber construction. By the turn of the 20 th century, timber construction was nearly extinct and structural iron construction was becoming commonplace for larger structures.

Following World War II, glulam timber construction became popular for long-span and architecturally exposed applications such as church roofs. At the time, if you wanted a structure that looked like timber, glulam construction was your only choice. That is no longer true.

In the 1970s, traditional timber frame construction experienced a revival. A small, core group of timber craftsmen, mostly located in northern New England, rediscovered and mastered the lost art of crafting timber structures with intricate joints. By the 1990s, timber frame construction had re-entered mainstream construction and was displacing glulam construction for architecturally exposed structures.

So, What's New?

Timber panels are new - Cross-Laminated Timber (CLT) and Dowel Laminated Timber (DLT). CLT has been used in Europe since the 1990s but has only been available in North America for a little more than a decade. Today, there are five major manufacturers of CLT in North America and one producer of DLT. The availability of timber panels has stimulated interest and excitement in the architectural community for building with mass timber.

Modern mass timber structures typically consist of a glulam timber frame supporting CLT or DLT floor and roof panels, often with CLT shear walls. This type of construction is extremely versatile and is suitable for both large and small structures - anywhere that an architecturally exposed structure is desired. It does not make much sense to build with timber and then cover it up with sheetrock and hung ceilings. By the way, industry experts continue to express that mass timber construction is also very sustainable, sequesters carbon, and is cost-effective.

CLT, NLT, and DLT

Cross-Laminated Timber has often been described as plywood on steroids. It is made up of alternating plies of dimension lumber that has been planed to approximately 1 3⁄8-inch thickness. Like plywood, each ply is oriented perpendicular to its adjacent plies. Common CLT layups are 3-ply (41⁄8-inch), 5-ply (6 7⁄8-inch), and 7-ply (9 5⁄8-inch). CLT panels are typically 8 feet or 10 feet wide and up to 60 feet long.

The structural design of CLT panels is covered in Chapter 10 of the National Design Specification® (NDS®) for Wood Construction. Effective section properties and reference design values can be found in ANSI/APA PRG 320-2018, Standard for Performance-Rated Cross-Laminated Timber.

Nail-Laminated Timber (NLT) panels are made up of dimension lumber (typically 2x6s) laid side-by-side and spiked together with nails. NLT is not a new thing and has been used infrequently for over a century. The advantage of NLT construction is that it does not require specialized fabricating equipment to manufacture, and it can even be built on-site. The disadvantage is that NLT panels require a significant number of nails that are labor intensive to install and make it impossible to cut the panels with Computer Numerical Control (CNC) equipment without the embedded nails destroying the cutter-head.

Dowel-Laminated Timber panels are the newest alternative. DLT is similar to NLT, except that it contains no nails. Transverse hardwood dowels are used instead of nails to bond the panels. Unlike NLT, DLT panels lend themselves to CNC fabrication.

Reaching for the Sky

High-rise construction has long been the exclusive domain of structural steel and reinforced concrete, but that is starting to change. Mass timber is now a player in the high-rise market. Brock Commons in Vancouver is currently the tallest mass timber building in North America, topping out at 18 stories. In the world of tall buildings, 18 stories may not sound all that impressive, but, for wood construction, it is a big deal.

It is unlikely that mass timber is going to displace structural steel and reinforced concrete for high-rise construction completely, but we will see more tall, mass timber projects and will probably be seeing a lot more mass timber and structural steel hybrids, especially with anticipated changes coming in the 2021 IBC. The 2021 IBC will permit buildings up to 18 stories to be constructed of mass timber.

Getting Connected

Timber engineering is all about the connections. Sizing the timbers and panels is the easy part. Designing timber connections is the challenging part. It has been said that a structure is essentially an assembly of connections that happen to be separated by beams and columns, and that is especially true of timber structures.

Many engineers that are inexperienced with timber engineering will attempt to connect timbers in a fashion similar to structural steel construction, with bulky side plates and lots of bolts. While this approach sometimes works, it is seldom the most practical or efficient way to make a timber connection, and it is rarely the most aesthetically pleasing solution for an exposed structure.

It is smarter to configure connections and connection hardware so that structural loads are transferred primarily in bearing and bolts are only relied on to resist incidental loads.

Timber is an organic material that shrinks and swells seasonally with changes in humidity. Failure to consider timber dimension changes associated with moisture content when designing connections can lead to disappointing (or dangerous) results. Steel gusset plates can restrain dimension change movements resulting in the splitting of the timbers (for more on this, see the February 2004 issue of STRUCTURE).

Fired Up

It is a common misconception that because wood is combustible, wood buildings perform poorly in a fire. While that may be true of light wood frame construction, it is not at all true of mass timber.

Timbers will develop a char layer on the surface when exposed to a flame. The char layer progresses slowly and insulates the wood beneath it from the heat of the fire, permitting the timbers to continue to carry load. When timber structures do eventually fail during a fire, they do not fail suddenly. They typically give firefighters ample warning prior to a collapse by making loud cracking and hissing noises. The exception is, when steel connection hardware is exposed to the fire, the connections will fail suddenly. It is important to protect steel connection hardware either with an intumescent coating or preferably by having all steel hardware embedded inside the timbers where the wood can protect the steel from the fire.

Unlike most other structural systems, the fire-resistance rating of mass timber assemblies or elements is based on a structural analysis rather than on the listed results of an ASTM E119 fire test. Chapter 16 of the NDS has a procedure for calculating the fire-resistance rating. The thickness of the char layer on the timber is stipulated for different time intervals. For instance, if a 1-hour fire rating is required, the NDS stipulates that the char layer on a timber is 1.8-inch-thick after 1 hour of fire exposure. It is then a simple matter of calculating the remaining section properties of a timber with 1.8 inches of wood removed from the exposed perimeter and determining if the reduced section is capable of supporting the applied dead loads with a stress increase to convert allowable stress to ultimate stress. The fire-resistance calculation for a CLT panel is similar, except the stipulated char thicknesses are a little different. A 5-ply CLT is needed if a fire rating is required since there is not much left of a 3-ply CLT if the bottom ply burns away.

Serviceability Considerations

The design of mass timber floor systems is typically not controlled by strength, but by serviceability - principally sound transmission and vibration.

Bare timber floors will readily transmit sound, particularly impact sound associated with footfalls. It is common to install an acoustic mat over the timber floor with a non-composite concrete topping slab or gypcrete topping to address sound transmission.

Floor vibration associated with foot traffic must be evaluated. Designing to an arbitrary static deflection limit such as L/360 or L/480 will not ensure that a floor structure does not feel bouncy, particularly if the floor structure has a period of vibration less than 9.0 Hertz.

Hybridization

Mass timber plays well with other structural materials. Often the right structural solution for a project is not a pure mass timber structure, but a hybrid solution. CLT floor and roof panels with glulam joists, structural steel girders and columns, and a concrete topping slab often make for a very efficient structure. The structural steel elements often require an intumescent coating to achieve a fire resistance comparable to the timber elements.

For the 18-story Brock Commons project, reinforced concrete shear walls resist wind and seismic loads. Mass timber shear walls could have done the job, but for a variety of reasons, it just made more sense to use concrete. There is no shame in not being a purist.

Design or Delegate

It is not uncommon for a Structural Engineer of Record to delegate design responsibility to a specialty timber engineer engaged by the contractor. Sometimes, responsibility for engineering just the timber connections is delegated, but occasionally an engineer will delegate responsibility for engineering the entire timber structure. In such cases, it is best to engage the specialty timber engineer during the design phase of the project. Otherwise, the bidding process can turn into a circus.

So how much of the timber engineering should be performed by the Engineer of Record and how much should be delegated? The answer depends on how much prior experience the engineer has with timber structures. The best advice is for the Engineer of Record to do as much as he is competent to do and delegate only what he is inexperienced at.

Resources

So, where can an engineer turn to get more information on mass timber engineering? The Timber Frame Engineering Council (TFEC) is an organization of structural engineers who specialize in timber. The TFEC has produced a library of documents that offer design guidance, including a Standard for Design of Timber Frame Structures, Code of Standard Practice, master specifications, and technical bulletins, all of which are available free of charge at https://bit.ly/2S7H7fp.

The CLT Handbook produced by FPInnovations offers a wealth of practical information.

The WoodWorks team is also always willing to offer design assistance and to point engineers and architects in the right direction.■

Mass Timber Floor Vibration

By Lucas Epp, P.Eng.

The maximum span of many floor systems is often controlled by limiting occupant perception of vibrations rather than strength or deflection. This is the case for long span concrete and steel floor framing, high-performance, light frame floors, and mass timber floors. The unsettling performance of a bouncy floor is typically caused by resonance between human walking frequencies (1.6-2.0 Hz) and the floor's natural frequency. If the walking pace is a multiple of floor frequency (e.g., walking at 2.0 Hz causing a floor at 6.0 Hz to vibrate), resonance can occur and the resulting accelerations can be disconcerting, particularly in longer-span structures with low damping.

For mass timber floors, rule-of-thumb guidance such as limiting the floor's fundamental frequency to above 8.0 Hz, or limiting the deflection under a unit point load, has been used in an attempt to avoid floors which perform poorly. However, simply limiting the natural frequency of the floor does not guarantee good performance. A better estimate of floor performance is the accelerations, which result from walking activities. These accelerations depend not only on the natural frequency, but also the amount of floor mass being mobilized, the damping in the system, the length of the walking path, and the frequency of occurrence. Human sensitivity to accelerations is a grey area and recommended limits on permissible accelerations for various use cases vary significantly between different guidelines. ( See Figure)

Guides such as AISC Design Guide 11 ( Vibrations of Steel-Framed Structural Systems Due to Human Activity, 2016) provide detailed approaches to calculate accelerations on floor plates. There are also several European guides which provide similar guidelines with different calculation approaches.

Calculating accelerations on a given floor plate can be done using finite element software, but this is an involved analysis and simpler guidance is needed to assist in early stage design and scheming.

Current Design Guidance

For mass timber floors, there are various guidelines in North America and Europe which have been developed to determine allowable vibration-controlled spans.

The CLT Handbook (FPInnovations, 2013) presents a formula which limits the span based on a combination of deflection under a unit point load and natural frequency. This criterion, however, ignores the contribution of different damping levels, the weight of any superimposed mass (such as concrete topping), and any added flexibility of supporting structure, all significant factors in vibration performance. The CLT Handbook formula results in the following maximum spans for typical CLT layups (ANSI/APA PRG 320, 2018):

4 1⁄8-inch-thick, 3-ply CLT - 11 feet to 12 feet

6 7⁄8-inch-thick, 5-ply CLT - 16 feet to 17 feet

9 5⁄8-inch-thick, 7-ply CLT - 20 feet to 21 feet

Concrete topping is often required on mass timber floors to generate sufficient acoustical separation between floors. This topping increases the modal mass (i.e., participating mass that needs to be excited by footfall), directly affecting the accelerations which would be felt on the floor plate.

In Europe, the guidance for mass timber floors in Eurocode 5 (EN 1995-1-1) states that, for floors with a natural frequency (f) > 8.0 Hz, the deflection under a 225-pound point load should be limited to less than 1⁄16 to 1⁄32 of an inch. For floors with f < 8.0 Hz, the Eurocode recommends calculating accelerations and limiting these to 0.5 to 1.5% gravity.

For early-stage design with panels supported on bearing walls, the CLT Handbook formula can be used only as an initial estimate of the maximum vibration-controlled span. For panels spanning onto beams, this formula is unconservative and more detailed acceleration analysis should be undertaken, as the beams contribute significantly to the flexibility of the system.

Currently, there is ongoing research to develop more accurate simplified criteria, as well as a robust guidance document for vibration design of mass timber floors. The US Mass Timber Floor Vibration Design Guide will be published by WoodWorks in 2020 and will contain more details on both analysis methods and acceptance criteria.

For further information and design guidance, refer to TFEC Bulletin 2019-14, Vibration Design of Mass Timber Floor Systems.

# data[].attributes.attachment_link.description
Mass timber is not a new idea, just a new name. Many people have heard the term "mass timber" batted around in the last few years, but not everyone has a clear understanding of what it means. Mass timber used to be referred to as "heavy timber" and the International Building Code (IBC) classifies it as Type IV construction.

# data[].attributes.attachment_link.readable_text
En caso de incendio, proteger las vidas de las personas es lo más importante. Todos los ocupantes del edificio deben tener la oportunidad de evacuar a tiempo, y el tiempo disponible depende en gran parte de los materiales escogidos y su comportamiento frente al fuego.

Con el fin de facilitar y optimizar este proceso, la Unión Europea ha adoptado la Norma EN 13501, introducida en la década del 2000, donde se especifican una serie de 'clases' que determinarán las propiedades anti-incendio de los distintos materiales de una solución arquitectónica. Sus clasificaciones se unifican y comparan con base en los mismos métodos de prueba, y actualmente se toman como referencia en muchos países del mundo.

Hemos recopilado sus nomenclaturas más importantes, para comprender de mejor manera el nivel de 'seguridad' de nuestro entorno construido, y la protección que entregamos como arquitectos al elegir los materiales de nuestros proyectos.

Reacción al Fuego

Los materiales y productos se pueden clasificar en 7 'Euroclases' distintas, según la manera en que reaccionan al fuego. Para entender esta clasificación, es importante considerar la combustión súbita generalizada o Flashover, que es el momento en que los materiales combustibles -no involucrados en el incendio original- comienzan a arder, acrecentando la temperatura en la habitación y aumentando su velocidad de propagación. [1]

A1

No combustible y no contribuye al fuego. Entre ellos podemos encontrar materiales y/o productos de concreto, vidrio, acero, piedra natural, ladrillos, y cerámicos.

A2

Poco combustible y muy baja contribución al fuego, sin causar Flashover. Entre ellos podemos encontrar materiales y/o productos similares a los Euroclase A1, pero con un pequeño porcentaje de componentes orgánicos.

B

Poco combustible y muy baja contribución al fuego, pero si causan Flashover. Entre ellos podemos encontrar materiales y/o productos como las placas de yeso y algunas maderas con protección al fuego.

C

Combustible, causa Flashover a los 10 minutos. Entre ellos podemos encontrar materiales y/o productos como la espuma fenólica, o placas de yeso con revestimientos superficiales más gruesos.

D

Combustible, causa Flashover antes de 10 minutos. Entre ellos podemos encontrar materiales y/o productos de madera sin protección, variando su reacción según su espesor y su densidad.

E

Combustible, causa Flashover antes de 2 minutos. Entre ellos podemos encontrar materiales y/o productos como tableros de fibra de baja densidad, o sistemas de aislamiento compuestos de plástico.

F

Comportamiento indeterminado. Materiales y/o productos no testeados.

S

Opacidad del Humo. Capacidad del elemento de no producir humos. Se divide en:

S1. Baja opacidad y producción de humos.

S2. Mediana opacidad y producción de humos.

S3. Alta opacidad y producción de humos.

D

Caída de Gotas. Capacidad del elemento de no producir ni gotas ni partículas inflamadas. Se divide en:

D0. No produce gotas ni partículas.

D1.Produce gotas y/o partículas no inflamadas.

D2. Produce gotas y/o partículas inflamadas.

Resistencia al Fuego

Cada elemento constructivo se comporta de manera distinta al entrar en contacto con el fuego, y su resistencia se mide en base a los siguientes parámetros (o sus combinaciones). Esta clasificación es acompañada habitualmente por un número (en minutos: 15, 30, 45, 60, 90, 120, 180, 240 o 360) que indica el tiempo en que estos parámetros se cumplen. [2] A modo de ejemplo, un REI 90 indica que un elemento constructivo mantiene su estabilidad (R), integridad (E) y su aislamiento térmico (I) durante 90 minutos.

R

Capacidad Portante. Capacidad del elemento constructivo de resistir mecánicamente, sin perder sus propiedades estructurales. Aunque los criterios de rendimiento varían según la solución constructiva, y las cargas que reciben -axiales (como muros o pilares) o en flexión (como pisos o vigas)-, en los dos casos se mide su tasa de deformación y su deformación máxima.

E

Integridad. Capacidad del elemento constructivo de impedir el paso de fuego y gases calientes hacia un recinto no afectado por el incendio.

I

Aislamiento. Capacidad del elemento constructivo de impedir el aumento de temperatura en la cara no expuesta directamente al fuego.

W - M - C - K

Otros parámetros importantes a considerar:

W (Radiación).Capacidad del elemento de evitar la transmisión del fuego hacia un recinto no afectado, a causa del exceso de calor irradiado a través del elemento.

M (Acción mecánica). Capacidad del elemento de resistir el impacto por la falla estructural de otro elemento cercano.

C (Cierre automático).Capacidad de puertas y ventanas de cerrarse completamente sin intervención humana.

K (Protección contra incendios de revestimientos). Capacidad de los revestimientos de muros y techos de entregar protección a los componentes que se encuentran detrás de ellos.

La intención de este artículo es acercarnos de manera sencilla a la protección anti incendios, a través de una de las normas más referidas al rededor del mundo. Es importante aclarar que este es un tema serio, que debe ser siempre evaluado por expertos, considerando las normativas locales y las especifícaciones técnicas de cada material y producto utilizado.

[1] Referencia ejemplos: InnoFireWood. (2019). EUROCLASS System. April, 2019, by Virtual.vtt.fi. Website: http://virtual.vtt.fi/virtual/innofirewood/stateoftheart/database/euroclass/euroclass.html
[2] Referencia: Fire resistance classes. April, 2019, by RISE Research Institutes of Sweden. Website: https://www.sp.se/en/index/services/fire_classes/sidor/default.aspx

# data[].attributes.attachment_link.title
Cómo se clasifican los materiales ante un incendio: reacción y resistencia al fuego

# data[].attributes.attachment_link.description
En caso de incendio, proteger las vidas de las personas es lo más importante. Todos los ocupantes del edificio deben tener la oportunidad de evacuar a tiempo, y el tiempo disponible depende en gran parte de los materiales escogidos y su comportamiento frente al fuego.

# data[].attributes.attachment_link.readable_text
Brian Lemay, Research Assistant Intern, National Ready Mixed Concrete Association Credit: 1 LU/HSW Course Number: ZG082019CS Sponsored by: Course Overview:
Concrete is the material of choice for the tallest buildings in the world and infrastructure designed to last centuries. To meet demands for these cutting-edge projects, concrete must be stronger, more durable and more workable than ever before. This article explores how new products, manufacturing methods and research are developing innovative concretes to meet these new challenges. Bendable concrete, smog eating concrete and carbon capture are just a few examples of new technologies enhancing a product that is nearly 5,000 years in development.
Learning Objectives:
1. Understand new technologies used in concrete manufacturing
2. Discover how innovative concrete products can improve project performance 3. Learn how to implement the latest concrete innovations in building and infrastructure projects 4. Demonstrate the importance of incorporating new technologies to enhance resilience and sustainability in the built environment Introduction
What do the Jubilee Church and the Pantheon have in common? They are both places of worship in Rome. But besides that, they are both built with innovative concrete. The Romans mastered the use of concrete 2,000 years ago to build some of the most iconic structures ever built. Although different than today's concrete, Roman concrete used the same principals, combining aggregate with a hydraulic binder. The aggregate included pieces of rock, ceramic tile and brick rubble often recycled from demolished buildings. Volcanic ash, called pozzolana, was the favored binder where it was available. Gypsum and quicklime were used as binders also. And even 3,000 years before, the Egyptians used a form of concrete made with mud and straw to build the pyramids. Today of course, most concrete is made with portland cement, invented in 1824, and combined with high quality quarried aggregate. Most modern concrete is augmented with innovative products and additives to enhance both plastic and hardened properties.

Innovative supplementary cementitious materials (SCMs) such as fly ash, slag cement and silica fume are used to increase strength, durability and workability. Chemical admixtures affect set time, freeze thaw resistance and flowability. Tiny fibers are added to increase ductility and control cracking. Carbon dioxide is injected into concrete to improve strength and capture greenhouse gasses. Some enhancements actually scrub pollutants from the surface of concrete and from the surrounding atmosphere which is what makes the concrete on the Jubilee Church so innovative. The exterior curved surfaces are coated with titanium dioxide (TiO ₂) cement which eats smog, helping to keep the surface clean.

Concrete is the most widely used building product in the world. It's mostly made locally with local materials. It's cost effective, available everywhere, strong and durable. Although conventional concrete can tackle most jobs, it is also the material of choice for the tallest buildings in the world and infrastructure designed to last centuries. Although concrete is not always synonymous with innovation, new products and manufacturing methods are enhancing concretes performance to tackle modern challenges. This article explores some of these latest innovations.
Self-cleaning Concrete
Imagine concrete that can clean itself and even the surrounding air of harmful pollutants. That's what concrete made with titanium dioxide (TiO ₂) can do. The function of TiO ₂ cement is to break down harmful pollutants in the air via a reaction catalyzed by light, or photocatalysis due to titanium dioxide which is added to the cement during its production. This capability of TiO ₂ cements was inspired by the ability of certain microbes to break down harmful chemicals by modifying their oxidation state, also through photocatalysis. However, in photocatylitic cements the reaction is carried out by the titanium whereas microbes rely on natural enzymes. The cement breaks down organic as well as inorganic pollutants, and it is intended to be used for projects in urban centers where air pollution and poor air quality are most pronounced.

An example of how TiO ₂ cements break down pollutants can be seen in its conversion of nitrogen dioxide (NO ₂), a harmful compound mostly produced by burning fuels in cars and trucks. Nitrogen dioxide is one of the compounds responsible for acid rain, smog, respiratory problems and staining of buildings and pavements. The reaction with sunlight produces hydroxyl radicals which react with NO ₂ to produce NO ₃ which is dissolved by water after reacting with the cement surface.

Research data of TX Active®, a TiO ₂ cement marketed by Lehigh Hanson (a division of HeidelbergCement Group) in the US, indicates that "up to 50% of these atmospheric pollutants could be reduced in some cities if only 15% of the buildings and roads were resurfaced with TX Active® cement." TX Active® was first used for the curved panels on the Jubilee church (also known as Dives in Misericordia Church) in Rome, which used the photocatalytic cement panels for its stylistic shells. Since then, Italcementi (a division of HeidelbergCement Group) has dedicated decades of research to photocatalytic cement products. This cement is promising in its potential to greatly improve urban life and the environment.
Case Study: Jubilee Church, Rome, Italy
According to architects Richard Meier and partners, the Jubilee Church in Rome was "conceived as part of Pope John Paul II's millennium initiative to rejuvenate parish life within Italy." The project consists of the church itself as well as both secular housing and housing for the clergy. The church is most easily distinguished by the three large concrete shells which are meant to represent the Holy Trinity. Given the symbolic importance of the shells, their appearance is an absolute priority. Thus, due to the fact that the shells need to remain in pristine condition, it was only natural that "self-cleaning" TX Active® photocatalytic concrete was used to ensure that the shells would not accumulate stains due to smog. Completed in 2003, the photocatalytic shells have notably remained clean and white, performing constant self-maintenance.
Bendable Concrete
Bendable concrete presents an efficient alternative primarily in the construction and maintenance of infrastructure, where concrete is subject to harsh weather conditions and extreme loading. The design which gives bendable concrete, or engineered cementitious composite (ECC), its impressive ductility is based off nacre, the substance that coats the inside of abalone shells. Nacre is composed of small aragonite platelets that are held together by natural polymers, allowing it to be both hard and flexible as platelets are free to slide side to side under stress. This effect is mimicked in bendable concrete by dispersing tiny fibers throughout. Victor C. Li of the University of Michigan, where ECC was first researched and invented, states that bendable concrete "can deform up to 3 to 5 percent in tension before it fails, which gives it 300 to 500 times more tensile strain capacity than normal concrete". It is of course this incredible ability to tolerate tensile strain that makes bendable concrete unique.

This enormous increase in ductility suggests various potential applications. Firstly, in roads as well as other paved surfaces which must bear repeated loading of heavy vehicles, bendable concrete would crack less often, preventing further weathering primarily from road salts which corrodes steel reinforcement. Further, due to ECC's capacity to absorb greater quantities of energy without being damaged, it can be used to make reinforcing elements such as the dampers on the Seisho Bypass Viaduct in Japan, which is roughly 28 kilometers long. Dr. Li also states that ECC has been employed as earthquake resistance in tall buildings in Tokyo and Osaka and further suggests that ECC would be useful in underground construction as well as the construction of water infrastructure.

However, before it can be more widely commercialized for such large-scale projects, bendable concrete must become more readily available. To be economically viable, it must be supplied efficiently and not overused on projects. But, it is paramount that design professionals be made aware of the product and its potential as they might otherwise overlook a promising concrete option for structures that require the ability to deal with considerable tensile strain.

Bendable concrete also has self-healing capabilities. Because bendable concrete keeps cracks relatively small, natural reactions within the hardened concrete generate "healing" products through carbon mineralization and continuous hydration which repairs the cracks and restores the durability of the concrete. Bendable concrete is a promising technology that already has proven itself through commercialization by several companies.

In fact, fiber reinforced concrete is not new. Many companies supply fibers for use in concrete with the objective of improving strength and durability of concrete in some way. Fiber reinforced concrete accomplishes this by incorporating fibers made of steel, glass or organic polymers (plastics). Sometimes naturally occurring fibers such as sisal and jute have been used as well. These fibers are primarily used to combat plastic shrinkage and drying shrinkage which can otherwise crack and damage the concrete. This resistance to shrinkage and subsequent cracking is the key to extending the lifespan of concrete, decreasing the frequency of costly repairs. Fibers also keep existing cracks from widening and further damaging the concrete when they do appear. And more recently, steel fibers are being used in structural applications to reduce the amount of traditional steel reinforcing bars, saving time and labor.
Case Study: 42 Broad, Fleetwood, New York
42 Broad is a 16-story mixed-use development near New York City being built with Insulating Concrete Form (ICF). ICF construction is becoming more mainstream with thousands of projects built in the US, but still considered innovative by many. ICFs sandwich a reinforced concrete wall between forms made of rigid polystyrene insulation that stay in place after the concrete hardens. There are several taller ICF buildings in Canada, but at 16 stories, 42 Broad will be the tallest in the US.

The real innovation on this project is panelizing the Amvic ICF blocks and using HelixTM steel fiber reinforcement. The ICFs are assembled off-site in a nearby plant and arrive at the jobsite as custom panels up to 50 feet long which results in labor and time savings on the job site, meaning the owner can occupy the building earlier. Part of what makes this process possible is the use of steel fibers in the ready mixed concrete to replace the horizontal reinforcing steel which eliminates costly horizontal rebar slices.

LafargeHolcim is one of the first companies to commercialize bendable concrete with a product called Ductal®. Ductal® is an ultra-high-performance concrete (UHPC) that incorporates fibers into the concrete mixture in order to improve strength and ductility along with a host of other benefits. LafargeHolcim distributes the premix powder, fibers and admixtures necessary to produce Ductal® to their partners, who then mix it into concrete. LafargeHolcim states that they use "high carbon metallic fibers, stainless fibers, poly-vinyl alcohol (PVA) fibers or glass fibers" to increase the concrete's ability to withstand tensile loads and deformation.

Ductal® is also less porous than conventional concrete, making it more resistant to chlorides, acids, and sulfates. It is also generally much more impermeable to water, making it ideal for roofing as well. In addition, Ductal® has self-healing properties. This bendable concrete has been thoroughly researched and is commercialized.
Case Study: Perez Art Museum, Miami, Florida
The Perez Art Museum in downtown Miami is notable largely for its application of Ductal® ultra-high-performance concrete (UHPC). The museum houses roughly 200,000 square feet of indoor and outdoor space for the presentation of modern and contemporary art. However, the property comes with one significant challenge. The museum is built on Biscayne Bay, where it is subject to sea air and salt. Additionally, it is at risk of tropical storms and hurricanes and thus must withstand the forces associated with these extreme weather events. Ductal® was used to produce roughly 100 16-foot-long mullions to support the world's largest impact resistant window at the time of its construction in 2013. The concrete mullions were made to be thin, maximizing visibility, while also meeting the Florida building code for hurricane resistance.

Graphene concrete is concrete reinforced by graphene. Graphene is a single layer of carbon atoms, tightly bound in a hexagonal honeycomb lattice. Layers of graphene stacked on top of each other form graphite, a naturally occurring, crystalline form of carbon most commonly used in pencils and lubricants. The separate layers of graphene in graphite can be separated into sheets only one atom thick. Graphene is the thinnest compound known to man, the lightest material known and the strongest compound discovered, over 100 times stronger than steel. Graphene concrete is made by suspending flakes of graphene in water, then mixing that water with traditional concrete ingredients such as cement and aggregate.

This technology's strength largely lies with its accessibility given that it is inexpensive, and compatible with modern, large scale manufacturing requirements. According to a research paper published in the Advanced Functional Materials journal, entitled "Ultrahigh Performance Nanoengineered Graphene-Concrete Composites for Multifunctional Applications," graphene concrete impressively shows a "146-percent increase in compressive strength as compared to regular concrete, a 79.5-percent increase in flexural strength, and a decrease in water permeability of almost 400 percent." In addition to its increased strength, graphene concrete is also more environmentally friendly, since it requires less cement than is typically required to produce concrete at a specified strength. Alternatively, higher strength graphene concrete could be used to produce smaller structural elements, thus reducing the amount of material used.
Carbon Capture
Like most manmade materials, concrete is considered a carbon dioxide (CO ₂) emitter, mainly due to the cement manufacturing process. But what if you could reverse that process and capture or sequester CO ₂ in concrete through natural processes or carbon capture technologies.

Carbonation is a naturally occurring process by which carbon dioxide (CO ₂) penetrates the surface of hardened concrete and chemically reacts with cement hydration products to form carbonates. For in-service concrete, carbonation is a slow process with many dependent variables. The rate decreases over time. This is because carbonation decreases permeability and carbonation occurs from the surface inward, creating a tighter matrix at the surface making it more difficult for CO ₂ to diffuse further into the concrete. While slow, the carbonation process does result in an uptake of some of the CO ₂ emitted from cement manufacturing, a chemical process called calcination. Theoretically, given enough time and ideal conditions, all of the CO ₂ emitted from calcination could be sequestered via carbonation. However, real world conditions are usually far from ideal.

The rate of CO ₂ uptake depends on exposure to air, surface orientation, surface-to-volume ratio, binder constituents, surface treatment, porosity, strength, humidity, temperature, and ambient CO ₂ concentration. Predicting how much CO ₂ is absorbed by in situ concrete is difficult. What is known is that rates of CO ₂ uptake are greatest when the surface-to-volume ratio is high, such as when concrete has been crushed and exposed to air.

In one of the most comprehensive studies, Xi, et al, published a summary of their research in the article "Substantial Global Carbon Uptake by Cement Carbonation," in the journal Nature Geoscience, November 2016. The research quantifies the natural reversal of the calcination process-carbonation. Using analytical modeling of carbonation chemistry, they were able to estimate the regional and global CO ₂ uptake between 1930 and 2013. They estimate that the cumulative amount of CO ₂ sequestered in concrete is 4.5 Gt in that period. This offsets 43% of the CO ₂ emissions from production of cement caused by the calcination process. They conclude that carbonation of cement products represents a substantial carbon sink.

Two areas of research and commercialization offer considerable enhancements to this CO ₂ uptake process. The most basic approach is enhanced carbonation at end-of-life and second-life conditions of concrete. This might not be considered innovative, since it would simply mean changing the way demolished concrete is collected and treated before re-use. If conditions are right, and particle size is small, crushed concrete can potentially absorb significant amounts of CO ₂ over a small period, such as one year or two and thus leaving crushed concrete exposed to air before re-use would be beneficial.

The other commercially viable technologies accelerate carbonation. This is accomplished either by injecting CO ₂ into concrete, curing concrete in CO ₂ or creating artificial limestone aggregates using CO ₂.

A company called CarbonCure uses CO ₂ captured from industrial emissions, which is then purified, liquefied and delivered to partner concrete plants in pressurized tanks. This is then injected into concrete while the concrete is being mixed which converts the CO ₂ into a solid-state mineral within the concrete. The minerals formed enhances compressive strength.

The process reduces CO ₂ emissions in two ways-through direct sequestration of CO ₂ injected into the concrete mixture and by reducing cement demand since CarbonCure concrete requires less cement to produce concrete at a specified strength.

The economic viability of this concrete also makes it a particularly attractive innovation. The cost of the equipment and licensing is offset by the reduction in cement. CarbonCure has installed their technology in over 100 plants across North America which have supplied over two million cubic yards of concrete. This product is sufficiently available to be used now and has already been used to great effect in numerous projects.
Case Study: 725 Ponce, Atlanta, Georgia
Completed in 2018, the office building at 725 Ponce De Leon Avenue was constructed using 48,000 cubic yards of CarbonCure concrete. Through their cooperation, structural engineer Uzun+Case and concrete supplier Thomas Concrete were able to greatly reduce the carbon footprint of this project. CarbonCure concrete sequestered 680 metric tons, or 1.5 million pounds, of CO ₂ which is roughly the amount of CO ₂ absorbed by 800 acres of US forest each year. The fact that emissions harmful to the environment could be reduced by such a significant factor on this large project, which provides 360,000 square feet of office space, is a perfect example of the viability of carbon capture and sequestration as a sustainable option for concrete construction.

Solidia Technologies offers another carbon capture technology. It combines a specially formulated cement with CO ₂ curing to produce concrete, primarily in the precast concrete products industry. Solidia cement is about the same cost as portland cement but significantly reduces CO ₂ emissions through reduced production energy. This is primarily because Solidia cement uses all of the same materials that are used to produce portland cement but in a different ratio.

Solidia cement uses less limestone than portland cement, which allows it to be fired at lower temperatures in the same rotary kilns in which ordinary portland cement is currently produced. These lower firing temperatures consume less energy and also produce 30% less greenhouse gases and other pollutants. Additionally, instead of curing in water like conventional concrete, Solidia concrete cures in contact with a CO ₂-containing atmosphere. Not only does this allow more precision during the curing process, but during curing, Solidia concrete sequesters CO ₂ equal to 5% of its weight. Between the combined factors of lower material costs, lower fuel costs, and the CO ₂ sequestered during curing, Solidia claims concrete's carbon footprint is reduced by 70%.

Solidia concrete also offers other practical benefits beyond being environmentally friendly. For example, Solidia states that their concrete experiences reduced efflorescence, meaning that salt staining will appear less severely and less frequently on the surface when it is exposed to water. Additionally, the concrete's water absorption is reduced, being less than 2%. It has a compressive strength of about 10,000 psi. It takes less pigment to color. And finally, Solidia Concrete is compatible with non-conventional aggregates and recycled glass. This allows further reduction of material cost and environmental benefits.

Another company using carbon capture technology is Blue Planet Ltd. They offer a product which "combines unpurified CO ₂ absorbed directly from power plant flue gas or other industrial CO ₂ emission sources with metal oxides to make limestone used to coat a substrate, making CO ₂-sequestered construction aggregate. The limestone coating is 44 percent by mass permanently sequestered CO ₂ waste." The substrate is usually small rock particles or even recycled concrete.

Blue Planet states that carbon-negative concrete is achievable by using their artificial limestone in concrete. They estimate that by replacing the conventional aggregate in one cubic yard of concrete, typically 3,000 pounds worth, 44% of its weight would be comprised of sequestered CO ₂, roughly 1,320 pounds. This would offset more than the amount of CO ₂ generally produced by the same amount of conventional concrete made with portland cement, which is roughly 600 pounds per cubic yard. Blue Planet's limestone-coated light-weight aggregate was specified for the Interim Boarding Area B at San Francisco International Airport in 2016. Concrete testing showed that Blue Planet's concrete met all necessary specifications.

Carbon capture and sequestration technology is a promising solution to reducing the carbon footprint of cement and concrete while improving performance. The possibility of vastly reducing CO ₂ emissions associated with the production of concrete or even going beyond by sequestering more CO ₂ than are produced during the cement manufacturing process is enticing. Many carbon capture and sequestration technologies are already commercially viable and are currently being used for construction since they can be conveniently produced by existing equipment or by retrofitting existing factories. Overall, carbon capture offers a simple but highly promising solution to reducing the environmental footprint of concrete.
Self-Consolidating Concrete
Self-consolidating concrete (SCC) is highly flowable, non-segregating concrete that can flow into place, fill formwork and encapsulate reinforcement without any mechanical vibration. SCC relies upon a combination of a high proportion of fine aggregate and admixtures called superplasticizers and viscosity-modifiers to achieve a stable and highly flowable concrete.

The increased ease of use and efficiency of SCC during construction is the basis for many of its principal benefits. First, it can be placed faster than regular concrete while requiring less finishing and no mechanical vibration. It also improves the uniformity of in-place concrete as well as the uniformity of surfaces, reducing or eliminating the need for surface work.

Additionally, using SCC allows for labor savings as well as increased jobsite safety as it does not require workers to travel the surface of slabs or the tops of walls to mechanically vibrate the concrete. SCC saves time during construction, resulting in cost savings, as well as improving the pumpability of the concrete and the turn-around times of concrete trucks.

SCC was first developed in 1986 by Prof. Okamura at Ouchi University, Japan, to address shortages in skilled labor. At first, SCC was used in highly specialized projects such as repair work or in areas difficult to reach due to its high cost of production and need for high quality control. The first high production use of SCC was in precast applications where concrete is produced and placed in controlled conditions. In ready mixed concrete applications, SCC was used primarily for heavily reinforced sections and where mechanical vibration was difficult. More recently, SCC is being used in architectural concrete since it results in a surface finish superior to that of conventional concrete. SCC still has a relatively high cost but is gaining popularity where labor is in short supply or where smooth exposed concrete is desired.

One of the highest profile uses of SCC is in high-rise building projects, proving its commercial viability and success in practical applications. Some considerations to take into account regarding this concrete stem from the fact that it is dependent upon flowability, which may be reduced by hot weather, long haul distances, or jobsite delays. Specifications required for a given job such as flowability and spread can vary, but mixtures can be tested via methods including the slump flow test to determine the extent of the concrete's plastic properties to ensure that the concrete arriving at a jobsite matches the standards specific to the project itself. SCC is fully commercialized and is used all over the world.
Case Study: 432 Park Avenue, New York
432 Park Avenue in New York City is currently the tallest residential structure in the US. It is an aesthetically simple building that features exposed white concrete columns that structurally reinforce the building in addition to providing the building its most distinctive stylistic attributes. The building is very thin for its height, having a width and length of 93.5 feet and a height of 1,396 feet. Multiple innovative structural methods were used to achieve "minimal displacement, accelerations, and vibrations to meet the most stringent standard" according to an article in STRUCTURE magazine, July 2018. These include, "five outriggers, each spanning over two stories, were devised throughout the height of the tower to serve as positive linkages between the interior core and the perimeter framing, which enhanced the overall performance of the structure".

Stiffer concrete with higher compressive strength was used on floors above the 38th to further increase resistance to movement in the upper stories. Further, all concrete cast for 432 Park Avenue was designed for enhanced durability by minimizing the ratio of water to cementitious materials to as low as 0.25 and the concrete was required to be pumpable, self-consolidating, and have a low heat of hydration to facilitate construction and appearance of the exposed structural elements.
From Waste to Worth
Supplementary Cementitious Materials (SCMs) such as fly ash, slag cement and silica fume are the keys to high performance concretes. What makes these materials so innovative is that most are derived from a waste-byproducts of a manufacturing process that would otherwise end up in landfills. But when these waste materials are combined with portland cement in concrete, they react with certain chemical compounds to produce more binder. As a result, these materials are extremely valuable as SCMs.
Case Study: Trump Tower Chicago
Chicago Trump Tower and Hotel stands at a stunning 92 stories, made entirely out of reinforced concrete. A total of 194,000 cubic yards of concrete was used on the project. Architect/engineer Skidmore, Owings & Merrill specified high-performance concrete and concrete supplier Prairie Materials designed the mixes. Columns and walls required 12,000 psi at 90 days up to level 51 with some lateral resisting elements up to 16,000 psi. SCC was specified for many of structural elements because of reinforcement congestion. To reduce heat of hydration, high volumes of SCMs were specified for the mat foundation which included a combination of slag cement, fly ash and silica fume. At time of construction, the 5,000-cubic-yard mat foundation was the largest single SCC placement in North America.

The high-performance reinforced concrete system helped minimize floor thickness creating higher ceilings. Residential floors also feature open spans up to 30 feet without requiring perimeter spandrel beams permitting panoramic vistas of Chicago and Lake Michigan. Combining several innovative concrete technologies allowed for quick, efficient construction as well as new opportunities that are not available with conventional concrete.

Silica fume is a waste byproduct of processing quartz into silicon or ferro-silicon metals in an electric arc furnace. Silica fume consists of superfine, spherical particles that when combined with cement significantly increases strength and durability of concrete. Of the three main SCMs, silica fume has the lowest supply and has the highest cost, usually at least three times that of portland cement. It's used in applications where extremely high strength is needed, such as columns in high-rise buildings or where extremely low permeability is desired for durability such as bridge decks and parking decks. It's typically combined with other SCMs to optimize performance and cost.

Blast furnace slag is the waste byproduct of iron manufacture. After quenching and grinding, the blast furnace slag takes on much higher value as an SCM for concrete. Blast furnace slag is used as a partial replacement for cement to impart added strength and durability to concrete. Some slag is used to make lightweight aggregate for concrete. About 16 million tons of slag were produced in the U.S. but less than half that was used in concrete as an SCM. Slag cement costs about the same or slightly more than cement depending on quality and location.

Coal ash is the waste byproduct of burning coal in electric power plants. Fly ash, a common SCM used in concrete, is one component of coal ash. According to the American Coal Ash Association (ACAA), in 2017, 111.4 million tons of coal ash were produced, of which 38.2 million tons was fly ash. Coal ash and fly ash have many uses, ranging from use in concrete as an SCM to synthetic gypsum for wallboard to mining applications. Of the 38.2 million tons of fly ash produced, only 14.1 million tons are used in concrete.

Fly ash is the most plentiful of all SCMs and is roughly half the cost of portland cement. However, because of increased emissions regulations on coal-fired power plants, not nearly as much high-quality fly ash is produced as in the past. In addition, with a move towards renewables and natural gas, coal-fired power plants are closing and thus many cost-effective supplies are diminishing.
Case Study: 102 Rivonia, Johannesburg, South Africa
102 Rivonia Road consists of two main buildings with connected walkways in-between to create a sense of connectedness and encourage collaboration between different areas of the office. It was designed with sustainability in mind, being 50% more sustainable than the average office building with a 4-star Green Star SA (South Africa) rating. Air cooled chillers and fire system that recycles used water also contributed to the project's energy efficiency. Notably, the use of fly ash in the concrete reduced the overall material use of the project by 30%, which also heavily contributed to the project having a lower carbon footprint.

Because coal power generation started in the early 1900s in the US, but the use of fly ash in concrete was only started to any significant volume in the late 1,900s, it is estimated that about 1.5 billion tons of coal ash has been placed in landfills, of which some is fly ash. And that's where the innovation comes in. Several companies, understanding the demand for fly ash in concrete is likely to increase have begun to recover fly ash from landfills and treat it using a process called beneficiation.

Beneficiation simply means taking coal ash from landfills and processing it so it meets the necessary standards for beneficial use. For fly ash, that typically means reducing the amount of unburned carbon in the ash. Carbon tends to have an absorptive quality which inhibits air entraining and water reducing admixtures. There are also other chemicals such as ammonia in some coal ash deposits which must be reduced before use in concrete.

Several companies have developed processes for harvesting ash from landfills and reducing the unburned carbon and ammonia, calcium, sulfur and other impurities. The simplest process is to burn off the excess carbon. Still other methods use chemical treatment to mitigate the effects of carbon and ammonia and one company uses low-frequency sound to reduce particle size to make them more uniform, a desired characteristic of fly ash. Companies include Boral Resources, Waste Management/Fly Ash Direct, SEFA Group, SonoAsh LLC, and Charah Solutions according an article "Digging Through the Past: Harvesting Legacy Ash Deposits to Meet Future Demand," authored by Rafik Minkara and published in Issue 1 2019 of Ash at Work magazine.

Minkara concludes "While the variety of technologies now exist to beneficiate land-filled and ponded ash, the cost and complexity of doing so can be challenging." He goes on to say "Beneficiation processes can be as simple as using off-the-shelf equipment or as involved as developing customized solutions with high capex requirements." In the end, it will depend on demand for fly ash. As low-cost supplies diminish over time, the demand is likely to be filled by harvesting and beneficiating the vast supply of coal ash in landfills.
Cementless Concrete
Although we are likely years away from widespread commercialization, one of the more interesting areas of research and development is on geopolymer concrete which uses fly ash and/or slag and chemical activators as the binder in place of portland cement. Geopolymer concrete is made by using a source of silicon and aluminum, usually fly ash or slag, and combining it with an alkaline activating solution which polymerizes these materials into molecular chains to create a hardened binder. The more common activating solutions include sodium hydroxide or potassium hydroxide which liberates the silicon and aluminum.

Compressive strength of geopolymer concrete is comparable to portland cement concrete or higher and strength gain is generally faster with strengths of 3,500 psi or higher at 24 hours. Compressive strengths at 28 days have shown to be 8,000 to 10,000 psi. Research shows that geopolymer concrete has lower drying shrinkage, lower heat of hydration, improved chloride permeability, and is more resistant to acids. And its fire resistance is considerably better than portland cement concrete, which is already highly fire resistant, making geopolymer concretes ideal for special high temperature applications.

To date, most of these products have not developed beyond the research and development stage. One company, Ceratech launched geopolymer concrete in in 2002 but later closed. A product called Pyrament® was launched in the 1980s but was not successfully commercialized. Some of the drawbacks include the high cost and energy to produce the chemical activator, the difficulty and safety concerns in handling a highly alkaline solution and the need to control temperature during the curing process. In addition, building code approvals are always a hurdle. Currently the most promising applications are in severe environment applications such as precast concrete bridges or other specialty applications such as high acid or high temperature environments or for rapid repair.
Case Study: Global Change Institute, Brisbane, Australia
As Australia's first carbon neutral building, the Global Change Institute at the University of Queensland was designed to meet the highest level of sustainability. It is one of the first buildings to be registered for The Living Building Challenge. Some of the green building features include operable sun-shading, bio-retention basin, onsite greywater system, solar energy and thermal chimney. And it is the first building to include structural geopolymer precast concrete, significantly reducing the carbon footprint of construction materials.

The key to geopolymer concrete commercialization will be to develop low cost, easy to use activators. One promising development is at Rice University where engineers have developed a geopolymer concrete that requires only a small fraction of the sodium-based activation chemicals used in other geopolymer concretes. According to the researchers, they used sophisticated statistical methods to optimize the mixing strategies for ingredients. This resulted in an optimal balance of calcium-rich fly ash, nanosilica and calcium oxide with less than 5% of the traditional sodium-based activator.
Conclusion
More than 20 billion tons of concrete are produced around the world each year. As a result, concrete construction contributes about 5% of global CO ₂ emissions primarily due to the cement manufacturing process. The demand for concrete will likely continue to grow as population grows. In addition, the demands on strength, durability and workability will continue to increase. A combination of traditional and advanced technologies will help meet these new demands. Technologies such as TiO ₂ cements, SCC, SCMs and fibers are being used now to varying degrees with outstanding results. Carbon capture and sequestration are in their infancy but show great promise. Fly ash beneficiation will help meet the demand for affordable, high performance concretes and geopolymer concretes may one day help make concrete carbon neutral without sacrificing performance.
Take the quiz and earn your certificate.

# data[].attributes.attachment_link.title
Concrete Innovations | Civil + Structural Engineer magazine

# data[].attributes.attachment_link.description
By Lionel Lemay, PE, SE, LEED AP. Executive Vice President, Structures and Sustainability, National Ready Mixed Concrete Association Brian Lemay, Research Assistant Intern, National Ready Mixed Concrete Association Credit: 1 LU/HSW Course Number: ZG082019CS Sponsored by: Build with Strength, a c ...

# data[].attributes.attachment_link.readable_text
Al desarrollar un proyecto arquitectónico, independientemente de su escala o programa, los arquitectos deben tomar una serie de decisiones en relación al proceso constructivo a adoptar. En esta elección influyen diversos aspectos que deben ser tenidos en cuenta para buscar la solución más óptima. Desde cuestiones estructurales, aspectos económicos, relacionados a la mano de obra disponible, cuestiones estéticas, entre otros.

Debido a que es muy frecuente que surjan dudas y preguntas en el desarrollo de proyectos en cuanto a la elección de los sistemas constructivos, elaboramos una guía práctica sobre los principales tipos de losas de hormigón tanto moldeadas in situ como prefabricadas que el proyectista debe conocer, junto con las ventajas y desventajas de cada una de ellas.

Para conocer más al respecto, continúe leyendo este artículo:

Losas moldeadas in situ

Ejecutadas directamente en la obra, las losas moldeadas in situ involucran procesos de producción de plazos intermedios dado el tiempo de curado que requiere el hormigón; no requieren de mano de obra especializada; y pueden adquirir formas muy diversas según el encofrado.

1. Losa Maciza

Totalmente conformada en el proceso de construcción, con espesores que normalmente varían entre 7 y 15 cm, su ejecución se realiza a partir de un enconfrado que constituirá el molde en el cual se vierte el hormigón sobre una armadura metálica.
Ventajas
Comúnmente utilizados en construcciones de tamaño pequeño a mediano - residenciales y comerciales -, los moldes se rellenan integralmente con hormigón funcionando en conjunto con la armadura metálica, de acuerdo a las alturas definidas por el cálculo estructural realizado previamente. Este sistema permite, además de diseños tradicionales, formatos tridimensionales y formas fluidas. También tiene un alto grado de resistencia a las grietas y fisuras.
Desventajas
Debido a la gran cantidad de material utilizado en el encofrado, que posteriormente se desecha, hay un alto coste en el valor total de la obra y una mayor generación de residuos. También cabe destacar que al requerirse un mayor volumen de hormigón y, en consecuencia, un mayor peso, los demás elementos de la estructura también deben ser reforzados, acarreando un aumento del material utilizado en la estructura.

2. Losa sin vigas

Las losas sin vigas son aquellas que apoyan directamente sobre columnas. Pueden ser macizas, de hormigón armado o pretensado, o incorporar otro material para formar losas nervadas. Pueden tener capiteles de diversas formas, cuadrados o circulares, para evitar el punzonamiento.
Ventajas
A pesar de no ser utilizado con tanta frecuencia, en comparación con otros sistemas presenta una gran ventaja pues permite cubrir grandes luces. Debido a la ausencia de vigas, que generan discontinuidad en la ejecución de los encofrados, permite una ejecución más sencilla, sobre todo en comparación a las otras losas moldeadas in situ, tales como la losa nervada.
Desventajas
A pesar de permitir cubrir grandes luces, el principal inconveniente de este sistema es el costo de la obra, ya que las losas aquí requieren de un mayor espesor y, en consecuencia, de un alto consumo de materiales tanto de hormigón como de acero, lo que en muchos casos puede hacer inviable su aplicación en el proyecto en términos económicos. Además, este sistema requiere de mano de obra especializada para su ejecución.

Estructuralmente, al no tener vigas, las losas están sometidas a un alto riesgo de punzonamiento donde, según el nivel de esfuerzo que exista entre el soporte y el plano de la losa, el pilar puede perforarla. Ante este peligro, además de aumentar el espesor de la losa, se pueden adoptar dos posibles soluciones: aumentar la dimensión de la columna, lo que también genera un aumento del material y en algunos casos una desproporción respecto al proyecto; o incluso, la ejecución de un capitel. Generalmente esta última solución es la más adoptada por constructores y arquitectos

3. Losa Nervada

En este tipo de losa se compone por una zona traccionada, conformada por nervios o costillas y una capa de hormigón que toma la compresión. El espacio entre los nervios puede quedar vacío o se pueden colocar elementos tales como bloques cerámicos, de hormigón celular o EPS (espuma de poliestireno), que no signifiquen un aporte en las cargas finales. La función principal de estos elementos es la de alivianar el peso de la estructura mediante la eliminación del hormigón en la zona traccionada, mejorando la eficiencia del sistema. La losa tiene una sección en forma de "T", con una capa de hormigón que recibe las fuerzas de compresión y nervios en los cuales, junto con la armadura metálica insertada en ellos, reciben las fuerzas de tracción.

Si la distancia entre los nervios fuera superior a un metro, el sistema sería un emparillado
Ventajas
En comparación con la losa maciza, este sistema presenta una mayor economía, permitiendo cubrir luces mayores y proporcionando una mayor libertad de diseño en su superficie. Para luces superiores a 7 metros, vale la pena invertir en la posibilidad de utilizar este sistema. En el caso de plantas de proporciones cuadradas, se utilizan costillas en ambas direcciones. En el caso de plantas muy rectangulares, el uso de los nervios se indica únicamente en una dirección, estando esta siempre dispuesta en el sentido de la luz más pequeña.
Desventajas
Debido a la necesidad de precisión en la elaboración de las nervaduras y la colocación de la armadura, este sistema requiere mano de obra especializada. También, requiere un mayor volumen de material para la ejecución del encofrado. Estructuralmente, aumentan la altura de las construcciones, y debido a su diseño, presentan una mayor dificultad en la compatibilidad con otros elementos arquitectónicos tales como las instalaciones del edificio, tanto eléctricas como hidráulicas.

En el proceso de la obra, involucra un gran cuidado y atención en el hormigonado, requiriendo de una máxima atención en el proceso de vibrado del hormigón.

Losas prefabricadas / premoldeadas

Producidas a través de procesos industriales, este tipo de losas están cuidadosamente diseñadas ser resistentes y ligeras. El cálculo estructural es muy preciso e involucran un estricto control de calidad para los materiales utilizados. Como se puede ver a continuación, si mayor resistencia y regularidad dimensional hace que sean excelentes opciones para varios tipos de construcciones.

1. Losa con Viguetas de hormigón armado y Bloques cerámicos

Estructuralmente funcionan en una sola dirección, siendo equivalente a las losas nervadas unidireccionales. La sección de las viguetas tiene forma de "T" invertida, con una altura que varía entre los 8 y 9 cm. La altura de la losa se corresponde a la suma de las alturas de los bloques junto con la carpeta de compresión.
Ventajas
Gracias a su sencillo sistema de montaje, su construcción no requiere mano de obra especializada. El sistema consiste en una sumatoria de elementos: las viguetas prefabricadas de hormigón, cuya función será la de absorber las fuerzas de tracción, bloques cerámicos y una capa superior de hormigón de 3 a 5 cm que tomará las fuerzas de compresión. Es una opción eficiente y de bajo coste en comparación con otros tipos de losas.

De uso frecuente en proyectos residenciales de bajo coste, presenta numerosas ventajas constructivas, potenciando el ahorro de materiales y permitiendo un proceso de ejecución veloz.

Su principal ventaja económica es que, al prescindir del uso de encofrados de madera durante el proceso constructivo, garantiza un bajo desperdicio de material y una ejecución rápida que reduce el coste de mano de obra.
Desventajas
Dado a que este sistema está dimensionado para cubrir pisos o techos, no debe recibir sobrecargas no previstas en la etapa proyectual tales como muros u otros elementos arquitectónicos, por lo que no permite una gran libertad de diseño. Si se producen sobrecargas, existe una gran posibilidad de que aparezcan fisuras, grietas u otros daños estructurales.

2. Losa con viguetas armadas

Se trata de un sistema formado por una losa unidireccional, en el que las viguetas armadas se intercalan con elementos no estructurales (Bloques cerámicos o de EPS) junto con una capa de hormigón.

Estas losas tienen una gran resistencia y pueden cubrir luces relativamente grandes (entre 10 y 15 m). El modelo estructural está compuesto por una armadura en celosía hiperestática, con barras paralelas y nudos rígidos que le confiere rigidez y actúan a modo de refuerzo ante las solicitaciones tangenciales.
Ventajas
Entre las ventajas de este sistema se encuentra el bajo valor de comercialización de sus elementos, la rapidez constructiva, su ligereza y que no requiere de mano de obra especializada.

La adopción de este tipo de losa también ayuda a optimizar la aislación térmica, sin absorber calor y proporcionando equilibrio en la temperatura interna.

Desventajas
Debido al tipo de material utilizado, es difícil realizar perforaciones o aberturas en su parte inferior y es necesario aplicar materiales tales como yeso para darle una terminación en el interior.

3. Prelosas armadas

Este tipo de losa prefabricada es muy similar al sistema anterior conformado por viguetas armadas y bloques cerámicos o de espuma de poliestireno, salvo que, en este caso, se utilizan prelosas (Placas prefabricadas) de hormigón reforzadas de mayor tamaño, que luego se instalarán una al lado de la otra.
Vantajas
Este sistema presenta una mayor resistencia que los dos casos anteriores y también una mayor velocidad de ejecución. Esto se debe a que presenta un menor número de elementos. También, el proceso constructivo requiere una menor cantidad de apuntalamientos para su ejecución.
Desventajas
A pesar de las ventajas mencionadas este sistema es más costoso pues involucra la utilización de un 30% más de hormigón.

4. Losas alveolares

Compuestos por grandes placas pretensadas, este sistema permite cubrir grandes luces siendo muy adecuado para proyectos de gran escala.
Ventajas
Debido a que sus elementos son pretensados, encontrándose reforzados mediante cables de acero de alta resistencia, este sistema es ampliamente utilizado en proyectos de carácter comercial e institucional. Las alturas pueden variar entre 10 y 30 centímetros. Estos elementos incorporan un refuerzo complementario para el bloqueo de las placas, dispuesto en sentido transversal y una capa de hormigón que regulariza el conjunto. Tienen una gran resistencia y pueden cubrir luces relativamente grandes de hasta 20 metros.

Desventajas
Debido a su peso, el transporte desde la fábrica hasta la obra y, posteriormente, hasta el lugar de instalación, se realiza íntegramente con grúas, involucrando un gasto complementario en equipos.

# data[].attributes.attachment_link.title
Tipos de losas de Hormigón: Ventajas y Desventajas

# data[].attributes.attachment_link.description
Al desarrollar un proyecto arquitectónico, independientemente de su escala o programa, los arquitectos deben tomar una serie de decisiones en relación al proceso constructivo a adoptar. En esta elección influyen diversos aspectos que deben ser tenidos en cuenta para buscar la solución más óptima.

# data[].attributes.attachment_link.readable_text
Con 300 metros de altura, Torre Costanera desafía el subsuelo chileno, donde e han registrado los temblores más potentes de la historia. (Jue, 11 Abr 2019)

Esta obra de más de 110,000 metros cuadrados es obra de César Pelli, uno de los más afamados expertos en estructuras altas.

Entre sus obras destacan las Torres Petornas de Kuala Lumpur y el International Finance Center en Hong Kong.

El reto no fue menor para este edificio ubicado en el distrito de Providencia, el centro financiero y cultural de Santiago

Con 300 metros de altura, la Torre Costanera es el edificio más alto de Santiago, y de América Latina.

De 64 niveles, el rascacielos cuenta con un sistema estructural que le otorga un nivel de protección sin precedentes en caso de un terremoto.

Además del uso de tecnologías verdes, la Gran Torre Santiago o Torre Costanera cuenta con un muro cortina de alto rendimiento y sistemas mecánicos de alta eficiencia.

Entre sus características, es el primer edificio en Latinoamérica que cuenta con ascensores de dos pisos controlados por computadora, la forma más eficiente de hacer circular a las personas a través de un edificio alto.

Cuenta con el centro comercial más grande de América Latina, dos hoteles y dos torres de oficinas adicionales.

La Torre cuenta con 6 niveles subterráneos de estacionamientos.

El diseño de la torre es una composición contemporánea de paredes de vidrio facetado.

Disminuyendo a medida que se elevan hacia el cielo, las paredes se separan en las esquinas de la torre, revelando su perfil delgado y reduciendo el volumen del edificio.

Cada pared se dobla ligeramente en su línea central, creando una cresta que se extiende hasta la parte superior de la torre.

Según César Pelli, Torre Costanera es "una versión moderna de la forma del obelisco, repleta de bordes nítidos y líneas largas".

En la parte superior, las cuatro paredes de la torre se proyectan hacia el cielo y rodean una corona enrejada: cuando se enciende por la noche, se convierte en un faro que ilumina todo Santiago.

La torre está diseñada para oscilar hasta 35 centímetros en su parte más alta, gracias a los trabajos estructurales de la firma chilena Rene Lagos Engineering.

Para tener una idea del trabajo, se produjeron 1,200 planos arquitectónicos y otros 1,000 de ingeniería, así como 2,500 de especialidades.

Debido a las características sísmicas de Chile, el edificio se diseñó con un proporción de 1 a 6, para darle mucho equilibrio en caso de un sismo.

La planta del edificio mide exactamente 50 por 50 metros, en relación con sus 300 metros de alto.

Mientras estaba en construcción, el edificio resistió el temblor del 27 de febrero de 2010, de 8.8 grados, sin que se registraran daños.

Así, la ingeniaría chilena ha creado un edificio que será referente para futuras construcciones, no sólo en este país sino en otros donde existe el riesgo de temblores.

Agregar un comentario

<< Artículo Anterior Siguiente Artículo >>

# data[].attributes.attachment_link.title
El edificio más alto de Latinoamérica está en Chile, zona de alta sismicidad

# data[].attributes.attachment_link.description
Con 300 metros de altura, Torre Costanera desafía el subsuelo chileno, donde e han registrado los temblores más potentes de la historia. (Jue, 11 Abr 2019) Esta obra de más de 110,000 metros cuadrados es obra de César Pelli , uno de los más afamados expertos en estructuras altas.

# data[].attributes.attachment_link.readable_text
Mjøstårnet by Voll Arkitekter in Brumunddal, Norway, has been verified as the world's tallest timber building by the Council on Tall Buildings and Urban Habitat.

The 85.4-metre-high tower was built using cross-laminated timber (CLT), a pioneering material that allows architects to build tall buildings from sustainable wood.

It has taken the title of world's tallest timber building from the 53-metre-high Brock Commons Tallwood House in Vancouver, which has a hybrid wood and concrete structure. Treet in Bergen, Norway, which is 49 metres high, used to be the tallest all timber building until Mjøstårnet completed in March 2019.

Mjøstårnet, the third-tallest building in the country, was designed by Norwegian practice Voll Arkitekter for AB Invest. The 18-storey mixed-use building contains apartments, the Wood Hotel, swimming pool, office space, and a restaurant

Timber specialist Moelven Limitre installed the building's timber structure, including elevator shafts made entirely from CLT, and columns made from glued laminated timber (glulam). Glulam is made from wood that is planed then glued together to form columns or beams, and can be used in the place of concrete or steel elements.

Mjøstårnet was built four storeys at a time in five construction stages. An internal scaffolding and a large crane was used to hoist the pre-fabricated sections and floor slabs into place.

As Brumunddal is an area of Norway with a major forestry and wood processing industry the materials were sourced locally.

"If urban densification is inevitable, then let it be done with a material that makes us happy"

CLT and glulam are strong enough to support large loads, and using timber means the carbon absorbed from the atmosphere by the trees is locked into the structure permanently.

The Council on Tall Buildings and Urban Habitat (CTBUH) recently revised its guidelines to recognise timber as structural material in response to what it described as an "uptick" in the number of tall timber buildings around the world.

As urban areas grow denser than ever and the number of tall buildings being built globally continues to rise, many architects have turned to CLT and other engineered timbers as a more sustainable building material.

Penda has designed a concept for a residential tower and vertical farm hybrid, and Anders Berensson Architects has developed a proposal for a city of 31 wooden skyscrapers for Stockholm.

In the UK, architects have called upon the government to make CLT exempt from the ban on combustable cladding materials. Not only is the material more environmentally friendly than steel, it also claims to be slow-burning and self-extinguishing without releasing toxic fumes.

Photos courtesy of Moelven.

# data[].attributes.attachment_link.title
Mjøstårnet in Norway becomes world's tallest timber tower

# data[].attributes.attachment_link.description
Mjøstårnet by Voll Arkitekter in Brumunddal, Norway, has been verified as the world's tallest timber building by the Council on Tall Buildings and Urban Habitat. The 85.4-metre-high tower was built using cross-laminated timber (CLT), a pioneering material that allows architects to build tall buildings from sustainable wood.

# data[].attributes.wish_content.attachment_props.text
Edificios sin y con sistemas de protección (aislantes) sísmica.

# data[].attributes.wish_content.attachment_props.original_text
Edificios sin y con sistemas de protección (aislantes) sísmica. https://t.co/D1csv3s8GP

# data[].attributes.attachment_link.embed_code
Edificios sin y con sistemas de protección (aislantes) sísmica. pic.twitter.com/D1csv3s8GP
— GeotechTips (@GeotechTips) January 10, 2019

# data[].attributes.attachment_link.metadata.attachment_props_source.data.text
Edificios sin y con sistemas de protección (aislantes) sísmica. https://t.co/D1csv3s8GP

# data[].attributes.attachment_link.metadata.attachment_props.original_text
Edificios sin y con sistemas de protección (aislantes) sísmica. https://t.co/D1csv3s8GP

# data[].attributes.attachment_link.metadata.attachment_props.text
Edificios sin y con sistemas de protección (aislantes) sísmica.

# data[].attributes.attachment_link.readable_text
Fusionando la realidad aumentada con el espacio físico, Fologram busca facilitar la construcción de diseños complejos -por ejemplo, diseños paramétricos que requieren de una serie de mediciones, verificaciones y cuidados específicos-, a través de instrucciones digitales que se superponen virtualmente sobre el espacio de trabajo, dirigiendo paso a paso a los albañiles durante el proceso constructivo.

'Los centros de investigación y las grandes empresas están trabajando con robots industriales para automatizar estas difíciles tareas de construcción. Sin embargo, los robots no se adaptan bien a los entornos impredecibles, e incluso los algoritmos más sofisticados de visión no pueden igualar la intuición y la habilidad de un albañil entrenado', comentan sus creadores.

+ 9

Fologram espera que la realidad aumentada elimine gradualmente los planos en obra, evitando errores y malinterpretaciones y aumentando la rapidez y la precisión de los procesos de construcción.

Revisa más detalles del proceso en el siguiente video.

# data[].attributes.attachment_link.title
Así se construye un muro de ladrillos utilizando realidad aumentada

# data[].attributes.attachment_link.description
Fusionando la realidad aumentada con el espacio físico, Fologram busca facilitar la construcción de diseños complejos -por ejemplo, diseños paramétricos que requieren de una serie de mediciones, verificaciones y cuidados específicos-, a través de instrucciones digitales que se superponen virtualmente sobre el espacio de trabajo, dirigiendo paso a paso a los albañiles durante el proceso constructivo.

# data[].attributes.attachment_link.readable_text
Recién terminado de construir, Noruega sorprende al mundo con la torre de madera más lata del mundo. Es respetuosa con el medio ambiente y resistente al fuego. (Vie, 23 Nov 2018)

Ubicada a 100 kilómetros la oeste de Oslo, la Torre Mjos tiene 18 pisos y una altura de 85.4 metros.

El objetivo, además de demostrar las posibilidades de la madera, es ofrecer un edificio que reduzca las emisiones de dióxido de carbono (CO2) en comparación con el concreto, que es el material principal de los edificios residenciales en las ciudades.

La torre se inaugurará oficialmente en marzo de 2019, convirtiéndose en la estructura de madera más alta, superando a la Torre Treet, de 49 metros, también edificada en Noruega.

Mjos Tower es un edificio residencial que, entre sus comodidades, ofrece una piscina cubierta, hotel, oficinas, restaurante y áreas comunes.

El proyecto corresponde a Voll Arkitekter, oficina local, que enfatiza que construir en madera ofrece más ventajas que con materiales tradicionales.

Por ejemplo, la construcción se hace en menor tiempo, casi a la mitad, por su ligereza y fácil manejo. Otra ventaja es su resistencia al fuego.

Estructuralmente hablando, para evitar que el viento balancee la torre, ésta cuenta con algunos elementos de concreto en los pisos superiores a fin de estabilizarla. Los arquitectos afirman que ninguno de estos elementos es estructural.

Este edificio se construyó con una madera llamada Glulam, madera laminada encolada. Según sus es más fuerte que el acero y tiene mayor resistencia y rigidez que la madera normal.

Para garantizar la capacidad de carga, para el piso se utilizaron paneles de chapa de unión cruzada, llamados Kerto-Q LVL.

Un video en noruego sobre la construcción de un edificio que abre nuevas posibilidades a la arquitectura construida con madera:

Agregar un comentario

Siguiente Artículo >>

# data[].attributes.attachment_link.description
Recién terminado de construir, Noruega sorprende al mundo con la torre de madera más lata del mundo. Es respetuosa con el medio ambiente y resistente al fuego. (Vie, 23 Nov 2018) Ubicada a 100 kilómetros la oeste de Oslo, la Torre Mjos tiene 18 pisos y una altura de 85.4 metros.

# data[].attributes.attachment_link.readable_text
Civil and structural engineers have significant continuing education options for elevating their careers.
By Bob Drake
Opportunities to elevate your professional skills and knowledge while working fulltime as a civil or structural engineer have never been greater - if you can find the time and money. Civil + Structural Engineer's annual directory has expanded to include 82 schools that confer master's degrees through online study in a range of relevant disciplines such as civil, structural, geotechnical, environmental, or sustainable engineering; project, construction, or engineering management; geospatial technologies; and even unmanned systems (i.e., drones).

In addition, many of the schools listed here offer online certificate programs in specialized fields of study that, in many cases, can later be applied toward a master's degree.
Arizona State University http://asuonline.asu.edu/online-degree-programs/graduate
* Master of Science, Construction Management

* Master of Science, Engineering, Sustainable Engineering

* Master of Sustainability Leadership
Auburn University http://eng.auburn.edu/online/graduate-programs/index.html
* Master of Civil Engineering

* Master of Engineering

* Master of Engineering Management
California State University, Fresno www.fresnostate.edu/cge/water
* Master of Science, Water Resource Management
Clarkson University https://www.clarkson.edu/graduate/civil-environmental-engineering
* Master of Engineering, Civil & Environmental Engineering

* Master of Science, Civil & Environmental Engineering
Clemson University https://www.clemson.edu/graduate/academics/program-details.html?m_id=Construction-Science-Management
* Master of Construction Science and Management
Colorado State University https://www.online.colostate.edu/degrees/graduate-degrees.dot
* Master of Engineering, Civil Engineering

* Master of Engineering, Engineering Management

* Master of Science, Civil Engineering
Columbia University www.cvn.columbia.edu
* Master of Science, Civil Engineering

* Master of Science, Construction Engineering and Management

* Master of Science, Earth and Environmental Engineering
Delta State University http://www.deltastate.edu/artsandsciences/mathematics-and-sciences/mas-git
* Master of Applied Science, Geospatial Information Technologies
Drexel University www.drexel.com/online-degrees/masterdegrees.aspx
* Master of Science, Construction Management,

* Master of Science, Engineering Management

* Master of Science, Project Management
Embry-Riddle Aeronautical University https://erau.edu/degrees/?degree-level=master&campus=worldwide
* Master of Science, Engineering Management

* Master of Science, Project Management

* Master of Science, Unmanned Systems
Florida International University http://fiuonline.fiu.edu/programs/online-graduate-degrees
* Master of Science, Construction Management

* Master of Science, Engineering Management
Harvard University www.extension.harvard.edu/academics/graduate-degrees/sustainability-degree
* Master of Liberal Arts, Sustainability (requires at least one, three-week course taken on campus)
Iowa State University www.distance.iastate.edu/programs/degrees
* Master of Engineering, Civil Engineering (construction engineering and management focus)

* Master of Engineering, Engineering Management
Johns Hopkins University https://ep.jhu.edu/programs-and-courses/programs
* Master of Civil Engineering

* Master of Environmental Engineering

* Master of Engineering Management

* Master of Science, Environmental Engineering and Science

* Master of Science, Environmental Planning and Management
Kansas State University http://global.k-state.edu/courses/degrees
* Master of Engineering Management

* Master of Science, Civil Engineering

* Master of Science, Community Development
Kennesaw State University http://learnonline.kennesaw.edu/graduate-programs
* Master of Science, Civil Engineering

* Master of Science, Engineering Management
Lawrence Technological University http://onlinedegrees.ltu.edu/colleges/college-of-engineering
* Master of Construction Engineering Management

* Master of Engineering Management

* Master of Science, Civil Engineering
Louisiana State University http://lsuonline.lsu.edu/programs/master-science-construction-management.aspx
* Master of Science, Construction Management
Michigan Technological University www.mtu.edu/gradschool/programs/degrees/geospatial
* Master of Science, Civil Engineering

* Master of Science, Integrated Geospatial Technology
Mississippi State University http://www.bagley.msstate.edu/distance/programs
* Master of Engineering

* Master of Science, Civil Engineering
Missouri University of Science and Technology http://dce.mst.edu/credit/degrees
* Master of Engineering, Geotechnics

* Master of Science, Civil Engineering (environmental, structural, geotechnical, water resources, or construction engineering focus)

* Master of Science, Environmental Engineering

* Master of Science, Engineering Management
Montana Tech https://www.mtech.edu/gradschool/distancelearning/pem.html
* Master of Project Engineering and Management
New England Institute of Technology https://www.neit.edu/Programs/Online-and-Hybrid-Degree-Programs
* Master of Science, Construction Management

* Master of Science, Engineering Management
New Jersey Institute of Technology http://www5.njit.edu/online/programs
* Master of Science, Civil Engineering

* Master of Science, Engineering Management

* Master of Science, Transportation
NewSchool of Architecture & Design https://newschoolarch.edu/academics/school-of-architecture/cm-programs/master-of-construction-management
* Master of Construction Management
North Carolina State University http://engineeringonline.ncsu.edu
* Master of Civil Engineering

* Master of Engineering

* Master of Environmental Engineering
https://online-distance.ncsu.edu/program/master-of-geospatial-information-science-and-technology
* Master of Geospatial Information Science and Technology
North Dakota State University www.ndsu.edu/dce/degrees/graduate
* Master of Construction Management

* Master of Science, Community Development

* Master of Science, Transportation and Urban Systems

* Master of Transportation and Urban Systems
Northern Arizona University https://nau.edu/online-paths-to-a-better-future
* Master of Science, Applied Geospatial Sciences
Norwich University http://civilengineering.norwich.edu
* Master of Civil Engineering (structural, environmental/water resources, geotechnical, or construction management focus)
Ohio University http://onlinemasters.ohio.edu
* Master of Science, Civil Engineering (construction engineering and management, environmental engineering, structural engineering, or transportation engineering focus)

* Master of Engineering Management
Old Dominion University https://online.odu.edu/academics/degree/masters-degree
* Master of Engineering Management

* Master of Engineering, Environmental Engineering

* Master of Science, Civil Engineering (coastal engineering focus)

* Master of Science, Environmental Engineering
Pennsylvania State University www.worldcampus.psu.edu
* Master of Engineering Management

* Master of Geographic Information Systems

* Master of Professional Studies, Community and Economic Development

* Master of Professional Studies in Geodesign

* Master of Professional Studies, Renewable Energy and Sustainability Systems

* Master of Project Management
Purdue University https://engineering.purdue.edu/ProEd
* Master of Science, Engineering Management and Leadership
Rowan University https://rowanu.com/programs/master-of-engineering-management
* Master of Engineering Management
Salisbury University www.salisbury.edu/geography/msgism
* Master of Science, GIS Management
South Dakota School of Mines & Technology www.sdsmt.edu/DistanceEducation
* Master of Science, Construction Engineering and Management

* Master of Science, Engineering Management

* Master of Science, Mining Engineering and Management
Southern Methodist University www.smu.edu/Lyle/Graduate/ProspectiveStudents/Lyle%20Distance%20Education%20Program/Programs
* Master of Arts, Sustainability and Development

* Master of Science, Civil Engineering,

* Master of Science, Engineering Management

* Master of Science, Environmental Engineering
Southern New Hampshire University www.snhu.edu/online-degrees/masters
* Master of Business Administration, Engineering Management

* Master of Business Administration, Project Management

* Master of Science, Construction Management
StanfordUniversity (Stanford Center for http://scpd.stanford.edu/certificates/mastersDegrees.jsp Professional Development)Stevens Institute of Technology https://www.stevens.edu/academics/stevens-online/available-programs/schaefer-school-engineering-science
* Master of Science, Civil and Environmental Engineering
Texas A&M University Corpus Christi http://gisc.tamucc.edu/graduate/graduate.html
* Master of Science, Construction Management
Texas Tech University www.depts.ttu.edu/elearning/programs/index.php
* Master of Science, Geospatial Surveying Engineering

* Master of Civil Engineering
The George Washington University http://onlineemse.seas.gwu.edu/online-programs/ms-in-engineering-management
* Master of Engineering

* Master of Engineering, Climate Change Engineering and Policy
The Ohio State University https://mgel.osu.edu/tracks
* Master of Science, Engineering Management
Thomas Jefferson University https://online.jefferson.edu/online-degrees
* Master of Global Engineering Leadership, Civil and Environmental Engineering technical track

* Master of Science, Construction Management
Trine University https://www.trine.edu/adult-studies/academics/graduate/ms-engineering-management.aspx
* Master of Science, Sustainable Design
University of Alabama - Birmingham www.uab.edu/elearning/degrees-certificates/graduate/master-degrees
* Master of Science, Engineering Management

* Master of Engineering, Advanced Safety Engineering and Management

* Master of Engineering, Structural Engineering

* Master of Engineering, Construction Engineering and Management
University of Alabama - Huntsville www.uah.edu/online-learning/online-programs
* Master of Engineering, Sustainable Smart Cities

* Master of Science, Civil Engineering (hybrid program, primarily online)
University of Arizona http://online.engineering.arizona.edu/online-programs
* Master of Science, Engineering Management

* Master of Engineering, Mining, Geological and Geophysical Engineering
University of Arkansas https://online.uark.edu/programs/master-science-engineering.php
* Master of Science, Engineering Management

* Master of Science, Engineering
University of California - Los Angeles www.msol.ucla.edu/sustainable-water-engineering
* Master of Science, Engineering Management

* Master of Science, Engineering (with Certificate of Specialization in Engineering Management or Mechanics of Structures)
University of Central Florida https://www.ucf.edu/online/masters
* Master of Science, Engineering (with Certificate of Sustainable Water Engineering)
University of Colorado - Colorado Springs www.uccs.edu/easonline/degree-programs/engineering-management-degree.html
* Master of Science, Engineering Management
University of Colorado - Denver www.cuonline.edu/GIS
* Master of Engineering, Engineering Management
University of Dayton www.udayton.edu/engineering/learn/graduate/engineering-management-ms.php
* Master of Engineering, Geographic Information Systems
University of Florida www.distance.ufl.edu/masters
* Master of Science, Engineering Management

* Master of Engineering, Environmental Engineering Sciences

* Master of International Construction Management

* Master of Science, Civil Engineering

* Master of Science, Environmental Engineering Sciences

* Master of Sustainable Design
University of Houston http://www.uh.edu/academics
* Master of Urban and Regional Planning

* Master of Science, Civil Engineering
University of Idaho www.uidaho.edu/cogs/programs-offered/online-programs/list
* Master of Science, Construction Management

* Master of Engineering, Civil Engineering

* Master of Engineering, Engineering Management

* Master of Science, Environmental Science
University of Illinois at Chicago http://meng.uic.edu
* Master of Science, Geological Engineering
University of Illinois at Urbana-Champaign http://cee.illinois.edu/academics/graduate-programs
* Master of Engineering

* Master of Science, Civil Engineering (construction management, infrastructure, transportation engineering, or structural engineering focus)
University of Louisville Online http://louisville.edu/online
* Master of Science, Environmental Engineering

* Master of Science, Civil Engineering

* Master of Science, Computer Science

* Master of Engineering, Engineering Management

* Graduate Certificate, Structural Engineering

* Graduate Certificate, Transportation Engineering

* Graduate Certificate, Cyber Security

* Graduate Certificate, Data Science
University of Maine https://online.umaine.edu/grad
The University of Louisville's J.B. Speed School of Engineering, ranked by U.S. News and World Report as one the Best Engineering Schools, offers a 100% online Master's in Civil Engineering. This degree, intended for professionals who already have a bachelor's degree in civil engineering, will help equip students with the technological knowledge for advancement in an aggressive employment marketplace. The online curriculum is taught by award-winning faculty who can provide students with an educational experience they can't find anywhere else. For more information visit http://uofl.me/civilstructural .

* Master of Science, Spatial Informatics
University of Maryland www.advancedengineering.umd.edu/programs
* Professional Science Master, Engineering and Business (Surveying Engineering concentration
University of Massachusetts - Lowell https://continuinged.uml.edu/degrees/grad/online-masters-engineering-management.cfm
* Master of Engineering, Project Management
University of Nebraska - Lincoln http://online.unl.edu/programs-and-courses/graduate-doctorate-programs/engineering-management.aspx
* Master of Science, Engineering Management
University of New Haven http://online.newhaven.edu/masters-in-environmental-engineering
* Master of Engineering Management
University of New Mexico http://unmonline.unm.edu/programs/masters/construction-management.html
* Master of Science, Environmental Engineering
University of South Carolina https://sc.edu/study/academic_overview/online_education/courses/degree_programs/online_graduate_degree_programs/index.php
* Master of Construction Management

* Master of Engineering, Civil Engineering
University of South Florida www.usf.edu/engineering/imse/graduate/msem.aspx
* Master of Science, Engineering Management
University of Southern California http://gapp.usc.edu/den/programs
* Master of Science, Engineering Management

* Master of Construction Management

* Master of Science, Civil Engineering (construction or structural engineering focus)

* Master of Science, Green Technologies
University of Tennessee - Knoxville http://volsonline.utk.edu/online-programs/graduate-programs
* Master of Science, Systems Architecting and Engineering

* Master of Science, Civil Engineering (public works or transportation concentration)
University of Texas - Arlington www.uta.edu/engineering/future-students/engineering-online/index.php
* Master of Science, Environmental Engineering

* Master of Construction Management

* Master of Science, Civil Engineering
University of Texas at Tyler http://www.uttyler.edu/academics/graduate/civil-engineering-degree.php
* Master of Science, Engineering Management
University of Virginia http://cgep.virginia.edu/civil-and-environmental-engineering
* Master of Science, Civil Engineering
University of Washington www.pce.uw.edu/online/masters-degrees
* Master of Engineering, Civil and Environmental Engineering (infrastructure systems focus)

* Master of Infrastructure Planning and Management

* Master of Science, Civil Engineering: Construction Engineering

* Master of Science, Construction Management
University of Wisconsin - Madison https://epd.wisc.edu/online-degrees
* Master of Sustainable Transportation

* Master of Engineering Management
University of Wisconsin - Platteville www.uwplatt.edu/distance-education/online-programs
* Master of Engineering, Sustainable Systems Engineering

* Master of Science, Engineering (structural/geotechnical engineering focus)
Your best career move
* Master of Science, Project Management

The University of Wisconsin-Platteville, a regionally accredited university, offers a 100% online master's in Engineering. Select an area of interest in Engineering Design, Applications in Engineering Management, Control (Electrical) Systems, or Structural/Geotechnical Engineering to round out your degree. Not ready for a full degree? Expand your skill set with an engineering certificate.
Villanova University http://www1.villanova.edu/main/online-programs.html
$10,000 scholarships, funded by the National Science Foundation, are available! The University of Wisconsin-Platteville has educated engineers for over 150 years and has earned a national reputation as a prestigious engineering institution.

* Master of Science, Civil Engineering

* Master of Science, Sustainable Engineering
Virginia Tech www.vto.vt.edu/?view=programs&show=masters
* Master of Science, Water Resources and Environmental Engineering

* Master of Natural Resources
Western Carolina University https://www.wcu.edu/learn/programs/index.aspx
* Master of Urban and Regional Planning

* Master of Construction Management
Western New England University https://www1.wne.edu/academics/graduate/engineering-management-mba.cfm
* Master of Project Management
Worcester Polytechnic Institute https://www.wpi.edu/academics/online/study
* Master of Science, Engineering Management/MBA

* Master of Science, Construction Project Management
Youngstown State University https://ysu.edu/academics/williamson-college-business-administration/online-engineering-management-mse
* Master of Science, Environmental Engineering

* Master of Science, Engineering Management

# data[].attributes.attachment_link.title
Online master's degree programs - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.description
Civil and structural engineers have significant continuing education options for elevating their careers. By Bob Drake Opportunities to elevate your professional skills and knowledge while working fulltime as a civil or structural engineer have never been greater - if you can find the time and money.

# data[].attributes.wish_content.attachment_props.text
(vía @Btamaroni + @joseyupanqui71) Fenómeno de resonancia por la presencia de vórtices de Von Karman. Combinación de vientos uniformes y geometría uniforme del obstáculo propiciaron un efecto resonante en el segundo modo de vibración del arco

# data[].attributes.wish_content.attachment_props.original_text
(vía @Btamaroni + @joseyupanqui71) Fenómeno de resonancia por la presencia de vórtices de Von Karman. Combinación de vientos uniformes y geometría uniforme del obstáculo propiciaron un efecto resonante en el segundo modo de vibración del arco https://t.co/0zbg4M07Gf

# data[].attributes.attachment_link.embed_code
(vía @Btamaroni + @joseyupanqui71) Fenómeno de resonancia por la presencia de vórtices de Von Karman. Combinación de vientos uniformes y geometría uniforme del obstáculo propiciaron un efecto resonante en el segundo modo de vibración del arco pic.twitter.com/0zbg4M07Gf
— Ingeniería en la Red (@ingenieriared) October 28, 2018

# data[].attributes.attachment_link.metadata.attachment_props_source.data.text
(vía @Btamaroni + @joseyupanqui71) Fenómeno de resonancia por la presencia de vórtices de Von Karman. Combinación de vientos uniformes y geometría uniforme del obstáculo propiciaron un efecto resonante en el segundo modo de vibración del arco https://t.co/0zbg4M07Gf

# data[].attributes.attachment_link.metadata.attachment_props.original_text
(vía @Btamaroni + @joseyupanqui71) Fenómeno de resonancia por la presencia de vórtices de Von Karman. Combinación de vientos uniformes y geometría uniforme del obstáculo propiciaron un efecto resonante en el segundo modo de vibración del arco https://t.co/0zbg4M07Gf

# data[].attributes.attachment_link.metadata.attachment_props.text
(vía @Btamaroni + @joseyupanqui71) Fenómeno de resonancia por la presencia de vórtices de Von Karman. Combinación de vientos uniformes y geometría uniforme del obstáculo propiciaron un efecto resonante en el segundo modo de vibración del arco

# data[].attributes.attachment_link.readable_text
San Diego, Calif. - The world's largest outdoor earthquake simulator, operated by structural engineers at the University of California San Diego, received a $16.3 million grant from the National Science Foundation (NSF) to upgrade the facility to expand its testing capabilities. The facility is one of nine experimental facilities in the NSF-funded Natural Hazards Engineering Earthquake Research Infrastructure (NHERI) program ( https://www.designsafe-ci.org).

The funds will enable the simulator, also commonly known as a shake table, to more realistically recreate the motion of the ground during strong earthquakes. After the upgrade, the facility will be able to test the heaviest test specimens in the world, from multi-story buildings, to bridge columns, bridge bents, wind turbines, with a full range of ground motions that can occur during an earthquake.

Until now, the shake table had only been able to move back and forth in one direction. The upgrade will allow the table to move in all directions (back and forth, up and down, left to right, yaw, pitch and roll).

"We will be able to reproduce earthquake motions with the most accuracy of any shake table in the world," said Professor Joel Conte, in the Department of structural engineering at UC San Diego, and principal investigator for the NSF upgrade grant.

Being able to reproduce a complete earthquake motion is important because during a temblor, the ground doesn't just shake horizontally. For example, during the Northridge earthquake in the Los Angeles area in 1994, bridge columns punched through bridge decks, hinting a strong vertical motion of the ground. Similarly, during the 1971 San Fernando earthquake, the buildings twisted and swayed hinting that the ground was probably rotating.

If engineers were to repeat, after the upgrade, the more than 30 structural and geo-structural tests performed on the shake table since its inauguration in 2004, they would find different levels of damage and different failure modes, Conte explained.

"This upgrade will have a huge impact on earthquake engineering," he said. "It will accelerate the discovery of knowledge engineers need to build new structures (buildings, bridges, power plants, dams, levees, telecommunication towers, wind turbines, retaining walls, tunnels and more) and retrofit older structures. It will enhance the resiliency of our communities."

The first structure to undergo tests on the shake table after the upgrade will be a full-scale 10-story building made from cross-laminated timber. The goal of these tests, led by Shiling Pei, a professor at the Colorado School of Mines, will be to gather critical fundamental data to design wood buildings as tall as 20 stories that do not suffer significant damage during large earthquakes. That is, not only can occupants leave the building unharmed, but they can also return and resume living in the building shortly after an earthquake.

Today, more and more big cities such as Los Angeles, San Francisco and Seattle, are looking to retrofit old concrete buildings for seismic safety. This will require large-scale tests of retrofitting systems, which can only be done on a shake table like the one being upgraded here at UC San Diego. The shake table also will be able to test large industrial systems, such as heating and air conditioning units for hospitals, and large electrical transformers for utility companies and the grid.

The operation and maintenance of the UC San Diego shake table is currently funded through a five-year grant from NSF's Natural Hazards Engineering Research Infrastructure (NHERI) Program.
Shake table's impact on society
In the past 14 years, research at UC San Diego's shake table, which is housed at the university's Englekirk Structural Engineering Center, has led to important changes in design codes for commercial and residential structures and new insights into the seismic performance of geotechnical systems, such as foundations, tunnels and retaining walls. It also has helped validate the use of innovative technologies to make buildings more likely to withstand earthquakes.

For example, in San Francisco, approximately 6,000 soft-story wood-frame buildings are being retrofitted to make them safer in strong earthquakes. Full-scale testing of retrofit systems for these "soft-story" wood frame buildings on the UC San Diego shake table, led by Professor John van de Lindt from Colorado State University, was critical to make this possible.

Research by Professor Jose Restrepo at UC San Diego, co-principal investigator for the NSF upgrade grant, and Professor Robert Fleischman at the University of Arizona, led to new design standards for so-called floor diaphragms, which transfer seismic forces from building floors to columns, walls and eventually foundations.
The upgrade
The shake table was originally designed in 2001-02 to reproduce all the directions of ground motion in an earthquake, but it was built with the capability of only one horizontal direction of motion due to budget constraints. In 2009, the Jacobs School of Engineering at UC San Diego received $2 million from the Department of Energy to add vertical actuators enabling the table to move up and down. But they did not have the hydraulic power needed to reproduce a vertical ground motion, until now.

This NSF grant will put in place the necessary power infrastructure, adding new hydraulic pumps, a cooling tower and very large accumulator banks for the facility's hydraulic-powered system. It will cover the costs of reconfiguring the existing two horizontal actuators, adding another two horizontal actuators, and powering the six vertical actuators to generate table motion in all three directions (longitudinal, transverse and vertical), and all three rotations (yaw, pitch and roll) as well.

"The upgraded shake table facility will also provide an unprecedented and exceptional tool to educate graduate, undergraduate, and K-12 students, as well as the news media, policy makers, infrastructure owners, insurance providers and the public, about natural disasters and the national need to develop effective technologies and policies to prevent these events from becoming societal disasters," said Lelli Van Den Einde, teaching professor at UC San Diego and co-principal investigator for the NSF upgrade grant.

The shake table facility will be closed from February 2020 to July 2021 to perform the upgrades.

# data[].attributes.attachment_link.title
World's largest outdoor shake table receives $16.3 million from NSF for upgrades - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.description
San Diego, Calif. - The world's largest outdoor earthquake simulator, operated by structural engineers at the University of California San Diego, received a $16.3 million grant from the National Science Foundation (NSF) to upgrade the facility to expand its testing capabilities.

# data[].attributes.attachment_link.title
East versus West Coast earthquakes - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.description
Damage at the Sherman Building in Washington, D.C., caused by the magnitude 5.8 earthquake in August 2011 in Mineral, Va. Photo: EHT Traceries Fewer quakes occur but with bigger stakes in the East. Why was an earthquake in Virginia felt at more than twice the distance than a similar-sized earthquake in California?

# data[].attributes.wish_content.attachment_props.text
Muy completa infografía de la Torre Inclinada de Pisa, que incluye detalles de la reparación que se le practicó desde 1990 para evitar su colapso.

# data[].attributes.wish_content.attachment_props.original_text
Muy completa infografía de la Torre Inclinada de Pisa, que incluye detalles de la reparación que se le practicó desde 1990 para evitar su colapso. https://t.co/X5w47hwl5y

# data[].attributes.attachment_link.embed_code
Muy completa infografía de la Torre Inclinada de Pisa, que incluye detalles de la reparación que se le practicó desde 1990 para evitar su colapso. pic.twitter.com/X5w47hwl5y
— GeotechTips (@GeotechTips) October 16, 2018

# data[].attributes.attachment_link.metadata.attachment_props_source.data.text
Muy completa infografía de la Torre Inclinada de Pisa, que incluye detalles de la reparación que se le practicó desde 1990 para evitar su colapso. https://t.co/X5w47hwl5y

# data[].attributes.attachment_link.metadata.attachment_props.original_text
Muy completa infografía de la Torre Inclinada de Pisa, que incluye detalles de la reparación que se le practicó desde 1990 para evitar su colapso. https://t.co/X5w47hwl5y

# data[].attributes.attachment_link.metadata.attachment_props.text
Muy completa infografía de la Torre Inclinada de Pisa, que incluye detalles de la reparación que se le practicó desde 1990 para evitar su colapso.

# data[].attributes.body
¿Por qué la Torre Eiffel tiene la forma que tiene? - Estructurando

# data[].attributes.attachment_link.readable_text
Construida para la Exposición Universal de 1889 en conmemoración del centenario de la Revolución Francesa, la Torre Eiffel se proyectó como un ejemplo de progreso y un logro de la ciencia y la tecnología del siglo XIX.

Su silueta estructural quizás sea una de las más fácilmente reconocibles del mundo. Pero, ¿sabes por qué tiene la forma que tiene?

En este blog hemos hablado más de una vez cómo factores externos pueden determinar la forma nuestra estructura. Ya hablamos como las turbulencias de un flujo podían hacerlo (en Jukovski, una curva interesante para usar en una estructura), o cómo, para evitar una erosión excesiva, podíamos optar por formas específicas (en Creager, otra curva interesante para usar en una estructura). También hablamos de las estructuras isotensionales que nos ahorran material ( Gaudí, el funicular de cargas y un software para calcular en 3d), o incluso vimos como nuestro astro rey podía tener mucho que decir en la forma de nuestra estructura (en ¿Puede el Sol condicionar la forma de una estructura?)

En este post te explicaremos cuál fue el motivo que llevó, en junio 1884, a los dos ingenieros principales de la empresa Eiffel, Émile Nouguier y Maurice Koechlin, a elegir la forma actual de la Torre Eiffel.

Nouguier y Koechlin tenían experiencia en el cálculo de puentes ferroviarios. Eran ingenieros civiles de gran prestigio en su tiempo y ya habían conseguido puentes con pilas muy altas para la época. Como por ejemplo, el Puente Garavit (Francia) o el Puente María Pía (Portugal).

Gracias a su experiencia, sabían que había tres grandes acciones a considerar para el cálculo de las pilas de un puente: las acciones provenientes del tablero del puente, el viento sobre la pila y el propio peso de esta. En el concurso de la gran torre para la exposición universal, solo tuvieron que utilizar sus conocimientos en pilas de puentes, a sabiendas que para la torre solo tendría dos acciones determinantes: el viento y el peso propio.

De hecho, la solución ya casi la tenían antes de empezar. Miremos por ejemplo, desde Google Maps, la pila del puente María Pía realizada por ellos 10 años antes que la majestuosa torre:

¿Lo veis? Os daré una pista 😉 :

¡Si! ¡Ahí está! Pero ¿por qué esa forma?

Como hemos dicho, las acciones a considerar en la una torre prácticamente son dos: el viento y el peso propio. Analicemos estas acciones detalladamente:

Pensemos primero en el peso propio: si la torre fuera de forma cilíndrica, está claro que las secciones inferiores del cilindro estarían sometidas a mas tensión (rojo) que las secciones superiores (azul) debido a que a igualdad de área de la sección, abajo hay mas peso soportado que en la parte de arriba:

Así pues, lo ideal para para optimizar el material, es reducir sección donde sobra (en la parte de arriba) y aumentar donde falta (en la parte de abajo) para llevar la estructura a una tensión constante en toda su altura. Algo parecido a esto:

Y eso se parece mucho a la Torre Eiffel. Este sólido se llama sólido isotensional y tiene la propiedad de que cada sección del sólido está sometida a la misma tensión (el peso aumenta en la misma medida que aumenta su sección).

Para los que quieran deducir la ecuación del borde de dicho sólido, os la planteo aquí:

Si el volumen de la parte de la torre que está por encima de de la sección a altura x es el volumen de revolución generado por la curva y = f(t):

Y el área de la sección es el círculo de radio f(x):

Entonces, la condición de que la presión a cualquier altura de la torre sea constante queda:

Siendo k una constante. Expresión que nos lleva a la siguiente ecuación funcional:

Que si resolvemos, nos deja la siguiente ecuación diferencial de variables separables:

Cuya solución son funciones de la forma:

Como veis, una función exponencial. Muy al rollo de la forma que tiene la Torre Eiffel.

Pero siento deciros que esta expresión solo vale para explicar una parte de la torre: de la segunda planta para arriba. No está mal, por que es prácticamente 2/3 partes de la torre.

Sin embargo, hay otra condición que define satisfactoriamente la totalidad de la torre. Y esta nace de la segunda acción importante en la estructura: el viento.

Nouguier y Koechlin diseñaron la estructura de modo que, para cada cota, el máximo momento generado por el viento fuese compensado por el momento del peso de la Torre.

Para lograr este equilibrio, el diseño tiene las patas curvadas, de tal modo que las tangentes a ellas, dibujadas en puntos a la misma altura, se corten siempre en el punto por el que pasa la resultante de los esfuerzos del viento sobre la parte que está encima de los puntos en cuestión. O dicho de otra manera mas sencilla: el momento debido al viento en cualquier parte de la Torre, desde una altura dada hasta la cima es igual al momento del peso de esa misma parte:

De esta igualdad de momentos, se puede calcular la curvatura de los bordes de la torre consiguiendo que la estructura resista el empuje del viento de la manera mas eficiente: por su propio peso.

Para el que quiera sacar la ecuación le dejo el planteamiento:

La rebanada de Torre a altura x con grosor dx tiene un peso proporcional a su volumen:

donde ρ es la densidad de la Torre y g es la aceleración debida a la gravedad. El brazo del peso es f0, la mitad de la anchura de la Torre en la base. La fuerza ejercida por el viento sobre cada rebanada es proporcional al área:

donde P es la máxima presión que la Torre puede soportar a altura x sin derrumbarse. La condición de igualdad de momentos nos lleva a la siguiente ecuación integral:

Pero para definir esta curvatura resolviendo la ecuación anterior, Nouguier y Koechlin tenían que conocer de manera precisa como cambia la ley de empujes del viento a lo largo la altura de la torre, w(x). ¡He aquí la proeza de estos ingenieros, quienes ya en 1870 sabían estimar, sin mucho error, la ley de presiones del viento para estructuras de 300 m de altura nunca construidas con anterioridad!

Por último, para hacer el proyecto más aceptable de cara a la opinión pública, Nouguier y Koechlin pidieron al arquitecto Stephen Sauvestre trabajara en la apariencia del proyecto.

Sauvestre propuso pedestales en las patas recubiertos con mampostería, arcos monumentales para unir las columnas y el primer nivel, grandes salas acristaladas en cada planta, un diseño en forma de bulbo para la cima y otros ornamentos para adornar la estructura en su conjunto.
El diseño propuesto final fue seleccionado por unanimidad entre mas de 700 propuestas. Una vez ejecutada, en marzo de 1889, fue la construcción más alta del mundo, permaneciendo así hasta mayo de 1930 (41 años) cuando el Edificio Chrysler, en New York, con 319 m de altura, le quitó el récord. ¿Quieres ser el primero en leer nuestros artículos?
Déjanos tu nombre y un email válido, y nosotros te avisaremos cuando hayan novedades en Estructurando

The following two tabs change content below.

# data[].attributes.attachment_link.title
¿Por qué la Torre Eiffel tiene la forma que tiene? - Estructurando

# data[].attributes.attachment_link.description
Construida para la Exposición Universal de 1889 en conmemoración del centenario de la Revolución Francesa, la Torre Eiffel se proyectó como un ejemplo de progreso y un logro de la ciencia y la tecnología del siglo XIX. Su silueta estructural quizás sea una de las más fácilmente reconocibles del mundo.

# data[].attributes.wish_content.attachment_props.text
Ilustración de alguno de los usos del gavión.

https://t.co/bKqdTdxiwj

# data[].attributes.wish_content.attachment_props.original_text
Ilustración de alguno de los usos del gavión.

https://t.co/bKqdTdxiwj https://t.co/MYEJfAldrh

# data[].attributes.attachment_link.embed_code
Ilustración de alguno de los usos del gavión.https://t.co/bKqdTdxiwj pic.twitter.com/MYEJfAldrh
— Ingeniería Real (@IngenieriaReal) October 7, 2018

# data[].attributes.attachment_link.metadata.attachment_props_source.data.text
Ilustración de alguno de los usos del gavión.

https://t.co/bKqdTdxiwj https://t.co/MYEJfAldrh

# data[].attributes.attachment_link.metadata.attachment_props.original_text
Ilustración de alguno de los usos del gavión.

https://t.co/bKqdTdxiwj https://t.co/MYEJfAldrh

# data[].attributes.attachment_link.metadata.attachment_props.text
Ilustración de alguno de los usos del gavión.

https://t.co/bKqdTdxiwj

# data[].attributes.attachment_link.readable_text
Devastation (left image) following the 1906 earthquake that dramatically impacted the economic and social growth of San Francisco compared with the "West Coast's most resilient skyscraper," the 181 Fremont tower (right image, center), designed to withstand a 475-year seismic event with minimal disruption. Ironically, the tower stands one block from the corner seen in the 1906 photo. Credit: (left image) California State Library; (right image) Jay Paul Company
NIST details steps to keep buildings functioning after natural hazards.

After an earthquake, hurricane, tornado, or other natural hazard, it's considered a win if no one gets hurt and buildings stay standing. But an even bigger victory is possible: keeping those structures operational. This outcome could become more likely with improved standards and codes for the construction of residential and commercial buildings, according to a new report recently delivered to the U.S. Congress by the National Institute of Standards and Technology (NIST).

"Current standards and codes focus on preserving lives by reducing the likelihood of significant building damage or structural collapse from hazards," said Steven McCabe, director of the NIST-led, multiagency National Earthquake Hazards Reduction Program (NEHRP) and one of the authors of the new publication. "But they generally don't address the additional need to preserve quality of life by keeping buildings habitable and functioning as normally as possible, what we call 'immediate occupancy.' The goal of our report is to put the nation on track to achieve this performance outcome."

The impact of a natural hazard on a community is usually most evident in the lives lost and physical destruction, but the accompanying economic shock, social disruptions, and reduced quality of life can often be devastating as well. "Cities and towns can be rebuilt, but lifestyles are damaged, sometimes permanently, if businesses, schools, utilities, transportation, and other essential operations are out of service for an extended period," said Therese McAllister, manager of NIST's Community Resilience Program and another report author.

The infamous 1906 San Francisco earthquake provides a dramatic example of that impact. In the half-century following the 1840s Gold Rush in California, San Francisco was the fastest growing metropolitan area in the region. That all changed on April 18, 1906, when the quake and resulting fires destroyed 80 percent of the city, killed about 3,000 residents and left nearly 300,000 people - three-fourths of the population - homeless, out of work, and without essential services. Though San Francisco rebuilt quickly, the disaster diverted trade, industry, and people south to Los Angeles, which then supplanted the "City by the Bay" as the largest, most important urban center in the western United States.

Even with modern building codes and standards in place, there is still room for improvement, as evidenced by the massive damage from the May 2011 tornado in Joplin, Mo., and the three major 2017 hurricanes striking Texas, Florida, and Puerto Rico.

"Immediate occupancy performance measures would help avoid catastrophes because they could build up a community's resiliency against natural hazards so that people still can live at home, still can go to work, and still can have the supporting infrastructure providing them services such as water and electricity," McCabe said.

In 2017, Congress tasked NIST to define what it would take to achieve immediate occupancy performance codes and standards for all buildings in all types of natural hazards, specifically in terms of fundamental research needs, possible technological applications based on that research, and key strategies that could be used to implement any resulting regulations.

The result of that effort is the new NIST report, Research needs to support immediate occupancy building performance objective following natural hazard events (NIST Special Publication 1224). The publication identifies a large portfolio of research and implementation activities that target enhanced performance objectives for residential and commercial buildings.

"The report provides valuable information about steps that could be taken to achieve immediate occupancy in the future," McAllister said.

The potential research activities presented in the report to Congress were developed with the assistance of a steering committee of recognized experts and stakeholder input obtained during a national workshop hosted by NIST in January 2018. Workshop participants identified four key areas that they believe must be considered when developing plans to achieve immediate occupancy performance: building design, community needs, economic and social impacts, and fostering acceptance and use of new practices.

For example, the report states that immediate occupancy performance measures must be developed, established, and implemented with a sensitivity to how they will economically affect building owners, business operators, occupants, and even whole communities. "You have to make sure that the cost of keeping buildings functional after natural hazards remains reasonable enough that everyone will be able to afford them," McCabe said.

The report also discusses key challenges facing the effort to make buildings functional in the wake of natural hazards, such as motivating communities to make the investment, managing how costs and benefits are balanced, and garnering public support.

Finally, the report concludes by recognizing that "increasing the performance goals for buildings would not be easily achieved, but the advantages may be substantial" and that making such objectives a reality "would entail a significant shift in practice for development, construction, and maintenance or retrofit of buildings." The report, its authors state, is the first step toward creating an action plan to achieve immediate occupancy across the nation with coordinated and detailed research goals and implementation activities.

"Our report outlines the steps that could be taken for a big raise of the bar - perhaps the biggest change in building standards and codes in 50 years - but one we believe is possible," McCabe said.

NIST Special Publication 1224 is available at https://dx.doi.org/10.6028/NIST.SP.1224.

Information provided by the National Institute of Standards and Technology ( www.nist.gov ).

# data[].attributes.attachment_link.title
Immediate occupancy performance codes - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.description
Devastation (left image) following the 1906 earthquake that dramatically impacted the economic and social growth of San Francisco compared with the "West Coast's most resilient skyscraper," the 181 Fremont tower (right image, center), designed to withstand a 475-year seismic event with minimal disruption. Ironically, the tower stands one block from the corner seen in the ...

# data[].attributes.attachment_link.readable_text
The Design Building brings the University of Massachusetts design programs - Architecture, Landscape Architecture and Regional Planning, and Building and Construction Technology - together in one creatively designed and sustainable building. Photo: Albert Vecerka/Esto
The UMass Design Building is the first public mass-timber building employing cross-laminated timber on the East Coast.

The University of Massachusetts (UMass) wanted to bring its design programs - Architecture, Landscape Architecture and Regional Planning, and Building and Construction Technology - together in one creatively designed building exemplifying sustainable construction practices. While a steel- or concrete-framed structure would be conventional for this building's size and use, the new John W. Olver Design Building features a timber-framed superstructure with an innovative composite floor system. The exposed wood structure emphasizes the potential of engineered wood elements while complementing and influencing the aesthetics inside and out.
Creative solution
Simpson Gumpertz & Heger Inc. (SGH) worked closely with Equilibrium Consulting, Inc. to design an 87,000-square-foot attractive, functional, and innovative structure. One challenge was designing open floor plates, originally conceived as a steel structure, with a mass-timber system. Historically, heavy timber buildings were constructed with large, closely spaced beams spanning 25 feet or less. Steel and concrete structures are commonly arranged in 30-foot bays, but easily allow engineers and architects to achieve longer spans. For the Design Building, the gravity system was changed to glue-laminated (glulam) beams and columns with an innovative approach for the floor system to construct the reimagined structure.

The solution was a composite cross-laminated timber (CLT) and concrete floor system. CLT, developed in the early 1990s, is a wood technology where sawn lumber from smaller trees are glued together in perpendicular layers to form large, mass-timber panels. Although CLT has been popular in Europe for longer than 20 years, it is a relatively new product for the United States. Taking this innovation one step further, perforated steel plate shear connectors were embedded into both the CLT panels and glulam beams and bonded with epoxy resin. A 4-inch-thick concrete slab was then placed on top of the CLT, which bonded to the steel plates and allowed the wood elements to act compositely with the concrete slab. This composite action greatly increases the strength and stiffness of the floor system, allowing the design team to achieve the required spans of up to 26 feet, typically reserved for concrete and steel construction.

The wood-concrete composite floors have excellent acoustics and dynamic damping properties. They also experience smaller deflections and limited potential for long-term creep effects as compared with a non-composite CLT floor. The steel reinforcement contained in the concrete topping helps mitigate concrete cracking and also facilitates transferring shear forces at diaphragm connections. Aesthetics were another important consideration in the development of the composite floor system. The underside of the CLT floor decks are mostly exposed, offering a warm and attractive ceiling, while the concrete slab is polished, providing a modern-looking and durable floor finish.
Dramatic design details
A defining feature of the Design Building and the showcase for its use of mass timber is the multi-story atrium. The atrium roof spans up to 56 feet to create a wide-open space below and an outdoor classroom/green roof above, complete with large pyramid skylights. A system of 3D "spider trusses" - consisting of composite concrete-glulam top chords, round glulam struts, and steel tension rods - creates a visually striking perspective from inside the space. The structural elements are left exposed as a visual demonstration of the efficient use of wood in compression and steel in tension. While one end of the spider trusses bears on typical glulam and steel columns, the other end bears on a story-deep steel truss that is visible from the atrium roof through the glass façade.

A suspended CLT stair complements the exposed structural elements in the atrium. In a hybrid use of materials, the CLT stair is suspended via steel rods from the steel story-deep truss that is in turn supported by two large glulam columns.

The structure's lateral system is composed of CLT shear walls and exposed glulam braced frames. The vertical CLT panels compose the walls of the building's stair towers, elevator core, and mechanical shafts. They presented an additional design challenge with their tall, narrow layout and relatively small gravity loads, which resulted in significant uplift forces from wind and seismic forces. Similar to the composite slab connectors, the shear wall hold downs are composed of steel plates embedded into the CLT panels, secured to the wood with epoxy, and welded to a conventional steel connection plate anchored to the concrete foundation.

The glulam braces are connected to the glulam columns by a series of embedded knife plates and tight-fit steel pins. The steel plates come together to form a true pin connection that is left exposed to provide unique aesthetic that honors the connection's structural function.
Secrets to success
As part of the design effort, SGH vetted production quality of the epoxy CLT connections by load testing one-fourth-scale mockups of the shear wall hold downs to confirm their strength and ductility. Additionally, SGH demonstrated to Massachusetts Department of Public Safety (DPS), the authority having jurisdiction, that this structural design meets the current building code's general intent. The design team developed a design basis with supporting standards, testing data, and proposed future code language for DPS's review.

Creative systems integration and willingness to try something new drove this project's success. With an exposed structure, the layout directly affects the building's aesthetics. Successful implementation required close coordination with architecture, and creative detailing of the wood connections to accentuate the visual appearance of the exposed wood framing. The design and fabrication team developed a variety of connections using embedded steel plates and dowels, tight-fit pins, screws, shear keys, and specialty cast steel clevises. These unique connections allowed the design team to cleverly hide some elements, such as beam-to-column connections, and emphasize others, such as the center hub of the spider trusses.

Engineered mass-timber structures employing CLT and glulam components allow for precision fabrication in a controlled factory environment. Computer numeric control (CNC) machining decreases wasted material volumes while increasing productivity and precision. This type of controlled fabrication ensures components fit together when delivered onsite and reduces field equipment needs and labor. Even with a moderate learning curve facing the small crew of timber erectors, construction schedules realized approximately 10,000 square feet of floor installation per week.

Several of the structural elements composing the large atrium space required additional onsite assembly and coordination. The steel truss was shipped to the site in pieces, assembled in the staging area, and lifted into place in two crane picks. The atrium roof was shored while the spider truss elements were connected to the center hub and the concrete topping was placed. Once the concrete topping achieved sufficient strength, the shoring was carefully removed. The stair was shipped to the site in large sections and erected by first suspending it from the steel rods and then field-connecting the pieces together with steel plates and epoxy in a carefully monitored procedure.

Factory fabrication also facilitated the use of the shear connectors for the composite slabs and hold downs for the shear walls, which both rely on epoxy to anchor embedded connections. The epoxy required strict conformance with environmental temperature, humidity, and volume tracking to ensure fabrication consistency and engagement within fabricated grooves - all of which were able to be carefully monitored and controlled in the factory. Most of these anchors were embedded during the shop fabrication process, with the CLT stair being the one exception.

The exposed structure required collaboration among the mechanical, electrical, plumbing, and fire protection (MEP/FP) systems. CLT shaft walls provide attractive enclosures for the MEP/FP chases, serve as bearing walls to support the floor and roof decks, and contribute to the structure's lateral force-resisting system. Openings in the CLT walls and decks were designed and detailed to allow MEP/FP systems to pass through the structure as needed. Electrical conduit buried within the composite CLT decks required additional coordination to maneuver the runs around the composite CLT-concrete shear connectors but allowed for a cleaner-looking ceiling in the end.
A striking example
As one of the larger modern mass timber buildings in the United States, and a first of its kind in Massachusetts, the Design Building uses wood products in new and creative ways to serve as a positive example for future work and provides a collaborative learning space for UMass's design programs. The Design Building offers a striking, first-of-its-kind example of many uses for mass construction methods and successfully provides an inspiring space for students, faculty, and visitors.

Watch videos about design and construction of the UMass John W. Olver Design Building at http://bct.eco.umass.edu/about-us/the-design-building-at-umass-amherst/design-building-videos.

Greggrey Cohen is senior principal, Jeffrey Langlois is senior project manager, and Nancy Varney is senior staff I with Simpson Gumpertz & Heger Inc. ().

# data[].attributes.attachment_link.title
An education in mass timber - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.description
The Design Building brings the University of Massachusetts design programs - Architecture, Landscape Architecture and Regional Planning, and Building and Construction Technology - together in one creatively designed and sustainable building. Photo: Albert Vecerka/Esto The UMass Design Building is the first public mass-timber building employing cross-laminated timber on the East Coast.

# data[].attributes.attachment_link.readable_text
London - Newly identified bridge forms could enable significantly longer bridge spans to be achieved in the future, potentially making a crossing over the Strait of Gibraltar, from the Iberian Peninsula to Morocco, feasible.

The new bridge forms - identified by a team of researchers from the University of Sheffield and Brunel University London, working with long span bridge expert Ian Firth of engineering consultants COWI - use a new mathematical modeling technique to identify optimal forms for very long-span bridges. The research is published on Sept. 19, 2018 in the Proceedings of the Royal Society.

A bridge's span is the distance of suspended roadway between towers, with the current world record standing at just under 2km. The most popular form for long spans is the suspension bridge form, as used for the Humber Bridge, though the cable-stayed bridge form, where cables directly connect the tower to the roadway - such as used in the recently constructed Queensferry Crossing in Scotland - is becoming increasingly popular.

As bridge spans become longer, a rapidly growing proportion of the structure is needed just to carry the bridge's own weight, rather than the traffic crossing it. This can create a vicious cycle: a relatively small increase in span requires use of significantly more material, leading to a heavier structure that requires yet more material to support it. This also sets a limit on how long a bridge span can be; beyond this limit a bridge simply cannot carry its own weight.

One option is to use stronger, lighter materials. However, steel remains the preferred choice because it is tough, readily available and relatively cheap. So the only other way to increase span is change the bridge's design.

Professor Matthew Gilbert from the University of Sheffield, who led the research, said: "The suspension bridge has been around for hundreds of years and while we've been able to build longer spans through incremental improvements, we've never stopped to look to see if it's actually the best form to use. Our research has shown that more structurally efficient forms do exist, which might open the door to significantly longer bridge spans in the future."

The technique devised by the team draws on theory developed by Professor Gilbert's namesake, Davies Gilbert, who in the early 19th Century used mathematical theory to persuade Thomas Telford that the suspension cables in his original design for the Menai Strait bridge in North Wales followed too shallow a curve. He also proposed a 'catenary of equal stress' showing the optimal shape of a cable accounting for the presence of gravity loads.

By incorporating this early 19th century theory into a modern mathematical optimization model, the team have identified bridge concepts that require the minimum possible volume of material, potentially making significantly longer spans feasible.

The mathematically optimal designs contain regions which resemble a bicycle wheel, with multiple 'spokes' in place of a single tower. But these would be very difficult to build in practice at large scale. The team therefore replaced these with split towers comprising just two or three 'spokes' as a compromise that retains most of the benefit of the optimal designs, while being a little easier to construct.

For a 5km span, which is likely to be required to build the 14km Strait of Gibraltar crossing, a traditional suspension bridge design would require far more material, making it at least 73 per cent heavier than the optimal design. In contrast, the proposed two- and three-spoke designs would be just 12 and 6 percent heavier, making them potentially much more economical to build.

The new bridge forms require less material principally because the forces from the deck are transmitted more efficiently through the bridge superstructure to the foundations. This is achieved by keeping the load paths short and avoiding sharp corners between tensile and compressive elements.

The team emphasize that their research is just the first step, and that the ideas cannot be developed immediately for construction of a mega span bridge. The current model considers only gravity loads and does not yet consider dynamic forces arising from traffic or wind loading. Further work is also required to address construction and maintenance issues.

Co-author, Ian Firth, from COWI, said: "This is an interesting development in the search for greater material efficiency in the design of super-long span bridges. There is much more work to do, notably in devising effective and economic construction methods, but maybe one day we will see these new forms taking shape across some wide estuary or sea crossing."

The research, funded by the Engineering and Physical Sciences Research Council (EPSRC), is also being presented today (19 September 2018) at 'Tomorrow's Megastructures', a symposium organized by the International Association for Bridge and Structural Engineering.

# data[].attributes.attachment_link.title
Researchers propose new bridge forms that can span further - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.description
London - Newly identified bridge forms could enable significantly longer bridge spans to be achieved in the future, potentially making a crossing over the Strait of Gibraltar, from the Iberian Peninsula to Morocco, feasible.

# data[].attributes.wish_content.attachment_props.text
Efecto de la instalación de aislantes sísmicos.

# data[].attributes.wish_content.attachment_props.original_text
Efecto de la instalación de aislantes sísmicos. https://t.co/WFuyNTyQkN

# data[].attributes.attachment_link.embed_code
Efecto de la instalación de aislantes sísmicos. pic.twitter.com/WFuyNTyQkN
— GeotechTips (@GeotechTips) September 27, 2018

# data[].attributes.attachment_link.metadata.attachment_props_source.data.text
Efecto de la instalación de aislantes sísmicos. https://t.co/WFuyNTyQkN

# data[].attributes.attachment_link.metadata.attachment_props.original_text
Efecto de la instalación de aislantes sísmicos. https://t.co/WFuyNTyQkN

# data[].attributes.attachment_link.metadata.attachment_props.text
Efecto de la instalación de aislantes sísmicos.

# data[].attributes.body
Breve resumen del Coeficiente de Balasto - Estructurando

# data[].attributes.attachment_link.readable_text
Uno se cree que un tema está más que trillado, como puede ser el coeficiente de balasto, cuando todavía me sorprende encontrar proyectos donde está mal aplicado o simplemente no se molestan en hacerlo correctamente.

Con el fin de dejar mi granito de arena para que el uso de este concepto esté mejor aplicado en los proyectos, dejo el post de hoy: un pequeño compendio sobre lo que es el Coeficiente de balasto, cómo se deduce de los ensayos el valor del K30 y cómo manejar ese valor para utilizarlo en nuestros cálculos estructurales. Además, recopilo varias formulaciones que creo que os pueden ser interesantes para los que el tema ya lo domináis.

El coeficiente de balasto Ks es un parámetro que se define como la relación entre la presión que actúa en un punto, p, y el asiento que se produce, y, es decir Ks=p/y. Este parámetro tiene dimensión de peso específico y, aunque depende de las propiedades del terreno (esto no se le escapa a nadie) no es una constante del mismo ya que también depende de las dimensiones del área que carga contra el terreno (esto es lo no toda la gente no tiene tan claro).

Veamos cómo podemos estimar el valor del coeficiente de balasto. Existen dos maneras para poder realizar dicha estimación:

1. Mediante el Ensayo de Placa de Carga

En España, el ensayo de placa de carga se rige según la normativa del Laboratorio de Transportes NLT-357/98 (viales) o la UNE 7391:1975 (cimentaciones). En la foto anterior podemos ver una placa circular que carga al terreno. De la placa salen unos comparadores que nos permiten medir el asiento que sufre el terreno al cargar la placa.

El cociente de la carga entre el asiento nos proporciona el coeficiente de balasto asociado a las dimensiones de la placa. Existen varios tipos de placas, las cuadradas de 30×30 cm o las circulares de 30, 60 o 76,2 cm de diámetro. Por tanto, el coeficiente viene generalmente respresentado por una K y el correspondiente subíndice que identifica a la placa con la que se realizó el ensayo.

Lo usual es que los laboratorios proporcionen el coeficiente de balasto de la placa cuadrada de 30 cm de lado, el K30. Existen muchos autores que han proporcionado varios valores del K30 para diferentes clases de suelos. Os dejo algunas de las tablas más interesantes que conviene tener:

Pero claro, una cosa es tener el coeficiente de balasto de una placa cuadrada de 30 cm de lado y otra muy distinta es tenerla para el tamaño real cimentación. Aunque sea el mismo terreno, el valor debe ser corregido por las dimensiones de nuestra cimentación. Para ello, fue Terzaghi (1955) quien propuso las siguientes formulaciones:

Para una zapata cuadrada de lado B(m) el coeficiente de balasto valdrá:

Para suelos cohesivos:

Para suelos arenosos

Para suelos de transición (entre arenas y arcillas)
%cohesivo es el porcentaje del suelo que se puede suponer cohesivo y %arenoso el porcentaje que se supone arenoso. (%cohesivo+%arenoso=100)

Si lo que tenemos es una losa rectangular de lados B(m) y L(m) (L>B):

2. En función de otras características del terreno.
Estamos hablando de correlaciones del coeficiente de balasto con otros parámetros del terreno como pueden ser:

En función del módulo de deformación:

Fórmula de Vogt:

Fórmula de Vesic:

Fórmula de Klepikov:
Siendo A el área de la cimentación y ω un coeficiente de forma que viene dado por:

Fórmula de la Universidad de Buenos Aires:

En función de la tensión admisible de la cimentación:

Siendo FS el factor de seguridad empleado para minorar la tensión admisible (entre 2 y 3)

Se puede usar la siguiente gráfica que relaciona el índice portante de California (CBR) con el coeficiente de balasto de una placa de 30'' de diámetro.

En función de la resistencia a compresión simple qu (suelos cohesivos):

En función del ensayo SPT:

En suelos cohesivos:

En arenas secas:

Y por tanto para una cimentación de BxL:

En arenas sumergidas Y por tanto para una cimentación de BxL:

Todo lo anterior queda dicho para el coeficiente de balasto vertical, es decir, el utilizable a zapatas y losas. Para el caso de pantallas o pilotes se debe considerar el coeficiente de balasto horizontal. Para ello ya hicimos un post hablando de una forma de estimarlo: " La verdadera historia del Ábaco de Chadeisson ". Pronto haremos otro post recopilando varias formulaciones para su estimación.

Espero que os resulte útil.
¿Quieres ser el primero en leer nuestros artículos?
Déjanos tu nombre y un email válido, y nosotros te avisaremos cuando hayan novedades en Estructurando

The following two tabs change content below.

# data[].attributes.attachment_link.title
Breve resumen del Coeficiente de Balasto - Estructurando

# data[].attributes.attachment_link.description
Uno se cree que un tema está más que trillado, como puede ser el coeficiente de balasto, cuando todavía me sorprende encontrar proyectos donde está mal aplicado o simplemente no se molestan en hacerlo correctamente.

# data[].attributes.wish_content.attachment_props.text
Simulación del colapso del puente Morandi por Kostack Studio
https://t.co/HsMLiUxch0

# data[].attributes.wish_content.attachment_props.original_text
Simulación del colapso del puente Morandi por Kostack Studio
https://t.co/HsMLiUxch0

# data[].attributes.attachment_link.embed_code
Simulación del colapso del puente Morandi por Kostack Studiohttps://t.co/HsMLiUxch0
— Manuel F. Herrador (@manuelfherrador) September 5, 2018

# data[].attributes.attachment_link.metadata.attachment_props_source.data.text
Simulación del colapso del puente Morandi por Kostack Studio
https://t.co/HsMLiUxch0

# data[].attributes.attachment_link.metadata.attachment_props.original_text
Simulación del colapso del puente Morandi por Kostack Studio
https://t.co/HsMLiUxch0

# data[].attributes.attachment_link.metadata.attachment_props.text
Simulación del colapso del puente Morandi por Kostack Studio
https://t.co/HsMLiUxch0

# data[].attributes.attachment_link.readable_text
A lightweight concrete ceiling with formwork 3D-printed from sand is among the innovations to feature in an experimental robot-made house built by university ETH Zurich.

The DFAB House, currently under construction in Dübendorf, Switzerland, showcases five digital building methods that have never before been seen in architecture, and the concrete Smart Slab is the latest addition.

The structure has been computationally designed to use only the minimal amount of material necessary to make it load-bearing, and is less than half the weight of usual concrete slabs.

The light weight form was enabled by using 3D sand printing to make the slab's underlying formwork. With 3D printing, highly complex structures are as easy to produce as a solid block - meaning extraneous material can be cut out of a design before it is sent to the printer.

ETH Zurich hopes the innovation will draw the construction industry away from producing "the same solid ceilings over and over again".

"The disadvantage [of traditional formwork production] is excessive material consumption and implicitly, a big carbon footprint," said ETH Zurich. "Digital fabrication methods can make a key contribution here: components can be optimised, enabling the necessary stability with far less material."

"The geometric complexity of a component does not matter in 3D printing, nor does it cause any additional costs - the printer simply prints what it is told to."

The Smart Slab covers 80 square metres between the ground and first floors of the DFAB House. In total it weighs 15 tonnes, and its ornamental, undulating design is just 20 millimetres at its thinnest point.

It was developed by a research group led by architect Benjamin Dillenburger, an assistant professor in Digital Building Technologies at ETH Zurich.

Working together with industry partners, the group used a 3D sand printer to produce the folding, dune-like formwork. The material is like an artificial sandstone, with fibre-reinforced concrete sprayed over the top.

While concrete can be directly 3D printed - and has been in structures like BAM Infra and Eindhoven University of Technology's cycling bridge - a key advantage of the hybrid process is that it allows for the use of this high-performance fibre-reinforced concrete.

ETH Zurich describes the slab as combining "the structural strength of concrete with the design freedom of 3D printing".

A secondary formwork made using a more traditional mould of CNC-cut timber created an overarching grid for the structure.

The research group designed both formworks using a custom software that not only adapted the shape to be as thin as possible but also coordinated the best size and positioning for lighting and sprinkler systems.

ETH Zurich casts intricate metal facade in a 3D-printed mould

"We didn't draw the slab; we programmed it," said architect Mania Aghaei Meibodi, a Smart Slab project lead. "It would not have been possible to coordinate all these aspects with analogue planning, particularly with such precision."

While ETH Zurich said this saves only a few centimetres in the DFAB House, it speculates that in a high-rise, it could mean fitting in a few extra floors.

The DFAB House has been in the works since 2017, when ETH Zurich announced it would design and build the three-storey residence at NEST - a modular research and innovation building operated by the Empa institute for material science and technology development and the Eawag aquatic research organisation.

It is part of the National Centre of Competence in Research (NCCR) Digital Fabrication project.

Another technology used at the site is Spatial Timber Assemblies, where wood house frames are assembled by robots that can work fast without colliding.
Project credits:
Project lead: Benjamin Dillenburger
Leading investigators: Benjamin Dillenburger, Robert Flatt, Joseph Schwartz
Contributing researchers: Mania Aghaei Meibodi (Project lead), Mathias Bernhard, Andrei Jipa, Demetris Shammas, Rena Giesecke, Jesus Medina, Melina Mezari, Matthias Leschok, Timothy Wangler, Nicolas Ruffray, Marco Bahr
Support: Ana Anton, Patrick Bedarf, Philippe Steiner, Ioanis Fousekis, Lorenz Brunner, Leander Peper, Xijie Ma, Michael Lyrenmann, Philippe Fleischmann, Andreas Reusser, Heinz Richner, Eleni Chatzi, Vasileios Ntertimanis, Harmanci Yunus Emre, Andreas Wieser, Robert Presl, Eugenio Serantoni, Valens Frangez, Adi Grüninger
Industry partners: Bürgin Creations, Frutiger, Voxeljet, Georg Ackermann, Stahlton, Christenguss, Fischer Rista, Rudolf Glauser, Gom International

More images

# data[].attributes.attachment_link.title
ETH Zurich makes lightweight concrete ceiling using 3D sand-printing

# data[].attributes.attachment_link.description
A lightweight concrete ceiling with formwork 3D-printed from sand is among the innovations to feature in an experimental robot-made house built by university ETH Zurich. The DFAB House, currently under construction in Dübendorf, Switzerland, showcases five digital building methods that have never before been seen in architecture, and the concrete Smart Slab is the latest addition.

# data[].attributes.attachment_link.readable_text
+ 13

Arquitecto de registro

Ingeniero estructural de registro

MKA (Magnusson Klemencic Associates)

Paisaje

DF/Damon Farber Landscape Architects

Contratista

Kraus-Anderson Construction Company

Diseño de madera y construcción
Más información Menos información

Descripción enviada por el equipo del proyecto. Cuando se requirió a Michael Green Architecture este emocionante proyecto, visualizó T3 como un modelo único de edificio de oficinas nuevas; una oportunidad para ofrecer una interpretación moderna del carácter robusto de edificios históricos de madera, ladrillo, piedra y acero, con los beneficios adicionales de comodidades de vanguardia, desempeño ambiental y capacidad técnica.

El proyecto es una inversión tanto en el pasado como en el futuro de Minneapolis y en la rica historia del Distrito Warehouse. El objetivo de diseño para T3 era construir sobre el carácter del pasado con una perspectiva moderna. A medida que las empresas buscan nuevos modelos competitivos para atraer al personal, el objetivo de T3 es proporcionar un ambiente cálido y acogedor atrayendo a los empleadores y empleados.

T3, que significa 'Timber, Technology, Transit', ofrece 224.000 pies cuadrados de oficinas y espacio comercial. Más de 3.600 metros cúbicos de columnas de madera maciza expuestas, vigas y losas de piso recuerdan la pesada construcción de madera de los antecesores del edificio.

El enfoque tecnológico moderno de T3 utiliza componentes de madera diseñados (principalmente madera laminada encolada) para techos, pisos, columnas, vigas y muebles. Una cantidad significativa de la madera utilizada en la fabricación proviene de árboles de pino matados por el escarabajo de montaña. Estos materiales modernos aportan la calidez y belleza de la madera al interior y promueven un ambiente interior saludable para los ocupantes.

Como resultado de la estructura de madera, T3 se erigió a una velocidad superior que la de los edificios con armazón de acero o de hormigón convencional. En menos de 10 semanas, se erigieron 180.000 pies cuadrados de armazón de madera, con un promedio de 30.000 pies cuadrados de superficie instalada por semana. También es más ligero que las estructuras de acero o concreto comparables, lo que reduce la profundidad y el alcance de la excavación y los cimientos. Además, el carbono incorporado en el sistema estructural de madera del edificio es más bajo que el encontrado en los edificios convencionales que se encuentran en la mayor parte del centro de Minneapolis y North Loop.

El éxito estético del edificio también se puede atribuir a la construcción masiva de madera. Candice Nichol, MGA Associate y el líder del proyecto T3, dicen que

la textura del NLT expuesto es bastante hermosa. Las pequeñas imperfecciones en la madera y la leve variación en el color de la madera solo aumentan la calidez y el carácter del nuevo espacio.

Un amplio acristalamiento exterior en todos los niveles, así como vistas al espacio social de la planta baja con muebles de madera, cabinas y una característica escalera, permiten que el público experimente el edificio.

El uso de la madera se celebra en todo el edificio dice Nichol:

Toda la estructura de madera de T3 se dejó expuesta intencionalmente y se iluminó con luz interior dirigida hacia el techo. Por la noche, la madera iluminada brillará a través de las aberturas exteriores

actualmente T3 es el edificio de madera más grande en masa de Estados Unidos. Con los cambiantes códigos de construcción en toda Norteamérica, los edificios altos de madera se volverán más comunes. T3 es un pionero en este tipo de construcción, pues ha abierto nuevos caminos y es quizás un prototipo para futuros edificios comerciales de madera.

Descripción del producto. Los ensambles laminados se han usado por más de un siglo, particularmente en almacenes donde se requerían pisos sólidos y resistentes. Ahora se está reconociendo nuevamente como una alternativa válida a la losa de concreto y acero en edificios comerciales e institucionales, y en edificios residenciales a los que a menudo está expuesto para crear una estética única.

# data[].attributes.attachment_link.description
13 Arquitecto de registro MKA (Magnusson Klemencic Associates) DF/Damon Farber Landscape Architects Kraus-Anderson Construction Company Diseño de madera y construcción Más información Menos información Descripción enviada por el equipo del proyecto.

# data[].attributes.wish_content.attachment_props.text
— ¿Y no le hicieron estudio geotécnico?
— ¡No, que va! Salía muy caro. El estructurista mejor le puso 1 kg/cm2 a las zapatas, y listo. Me ahorré esa plata.
— ¿Seguro?
— ¡Claro! No pasará nada.
— ...

# data[].attributes.wish_content.attachment_props.original_text
— ¿Y no le hicieron estudio geotécnico?
— ¡No, que va! Salía muy caro. El estructurista mejor le puso 1 kg/cm2 a las zapatas, y listo. Me ahorré esa plata.
— ¿Seguro?
— ¡Claro! No pasará nada.
— ... https://t.co/Sw0x3Ofh08

# data[].attributes.attachment_link.embed_code
— ¿Y no le hicieron estudio geotécnico?
— ¡No, que va! Salía muy caro. El estructurista mejor le puso 1 kg/cm2 a las zapatas, y listo. Me ahorré esa plata.
— ¿Seguro?
— ¡Claro! No pasará nada.
— ... pic.twitter.com/Sw0x3Ofh08
— GeotechTips (@GeotechTips) July 25, 2018

# data[].attributes.attachment_link.metadata.attachment_props_source.data.text
— ¿Y no le hicieron estudio geotécnico?
— ¡No, que va! Salía muy caro. El estructurista mejor le puso 1 kg/cm2 a las zapatas, y listo. Me ahorré esa plata.
— ¿Seguro?
— ¡Claro! No pasará nada.
— ... https://t.co/Sw0x3Ofh08

# data[].attributes.attachment_link.metadata.attachment_props.original_text
— ¿Y no le hicieron estudio geotécnico?
— ¡No, que va! Salía muy caro. El estructurista mejor le puso 1 kg/cm2 a las zapatas, y listo. Me ahorré esa plata.
— ¿Seguro?
— ¡Claro! No pasará nada.
— ... https://t.co/Sw0x3Ofh08

# data[].attributes.attachment_link.metadata.attachment_props.text
— ¿Y no le hicieron estudio geotécnico?
— ¡No, que va! Salía muy caro. El estructurista mejor le puso 1 kg/cm2 a las zapatas, y listo. Me ahorré esa plata.
— ¿Seguro?
— ¡Claro! No pasará nada.
— ...

# data[].attributes.wish_content.attachment_props.text
Distribución de cortante y momento en una escalera. Muy impresionante.

# data[].attributes.wish_content.attachment_props.original_text
Distribución de cortante y momento en una escalera. Muy impresionante. https://t.co/poXco0Kypa

# data[].attributes.attachment_link.embed_code
Distribución de cortante y momento en una escalera. Muy impresionante. pic.twitter.com/poXco0Kypa
— GeotechTips (@GeotechTips) July 16, 2018

# data[].attributes.attachment_link.metadata.attachment_props_source.data.text
Distribución de cortante y momento en una escalera. Muy impresionante. https://t.co/poXco0Kypa

# data[].attributes.attachment_link.metadata.attachment_props.original_text
Distribución de cortante y momento en una escalera. Muy impresionante. https://t.co/poXco0Kypa

# data[].attributes.attachment_link.metadata.attachment_props.text
Distribución de cortante y momento en una escalera. Muy impresionante.

# data[].attributes.wish_content.attachment_props.text
Allí es cuando tus alumnos te dicen: «¿Profe, y por qué me quita toda la calificación si solo me equivoqué en un signo? Tengo el procedimiento bueno». 🙄

Lugar: Plaza Artz Pedregal, Ciudad de México 🇲🇽

# data[].attributes.wish_content.attachment_props.original_text
Allí es cuando tus alumnos te dicen: «¿Profe, y por qué me quita toda la calificación si solo me equivoqué en un signo? Tengo el procedimiento bueno». 🙄

Lugar: Plaza Artz Pedregal, Ciudad de México 🇲🇽 https://t.co/sBSloPzWpo

# data[].attributes.attachment_link.embed_code
Allí es cuando tus alumnos te dicen: «¿Profe, y por qué me quita toda la calificación si solo me equivoqué en un signo? Tengo el procedimiento bueno». 🙄

Lugar: Plaza Artz Pedregal, Ciudad de México 🇲🇽 pic.twitter.com/sBSloPzWpo
— GeotechTips (@GeotechTips) July 13, 2018

# data[].attributes.attachment_link.metadata.attachment_props_source.data.text
Allí es cuando tus alumnos te dicen: «¿Profe, y por qué me quita toda la calificación si solo me equivoqué en un signo? Tengo el procedimiento bueno». 🙄

Lugar: Plaza Artz Pedregal, Ciudad de México 🇲🇽 https://t.co/sBSloPzWpo

# data[].attributes.attachment_link.metadata.attachment_props.original_text
Allí es cuando tus alumnos te dicen: «¿Profe, y por qué me quita toda la calificación si solo me equivoqué en un signo? Tengo el procedimiento bueno». 🙄

Lugar: Plaza Artz Pedregal, Ciudad de México 🇲🇽 https://t.co/sBSloPzWpo

# data[].attributes.attachment_link.metadata.attachment_props.text
Allí es cuando tus alumnos te dicen: «¿Profe, y por qué me quita toda la calificación si solo me equivoqué en un signo? Tengo el procedimiento bueno». 🙄

Lugar: Plaza Artz Pedregal, Ciudad de México 🇲🇽

# data[].attributes.attachment_link.readable_text
Aisladores y disipadores sísmicos

En este post veremos dos tipos de sistemas que permiten mejorar la respuesta sísmica de las estructura: los Aisladores y los Disipadores sísmicos. Podréis ver como actúan en unos vídeos muy ilustrativos.

Estos sistemas se colocan entre la subestructura y la superestructura de edificios, puentes y también en algunos casos, en la misma superestructura de edificios, y permiten mejorar la respuesta sísmica aumentando los periodos y proporcionando amortiguamiento y absorción de energía adicional, reduciendo sus deformaciones según sea el caso.

Sin embargo, desde el punto de vista estructural, ambos sistema trabajan de forma muy diferente. Veamos las diferencias:

Los aisladores sísmicos consiguen desacoplar la estructura del terreno colocándose estratégicamente en partes especificas de la estructura, los cuales, en un evento sísmico, proveen a la estructura la suficiente flexibilidad para diferenciar la mayor cantidad posible el periodo natural de la estructura con el periodo natural del sismo, evitando que se produzca resonancia, lo cual podría provocar daños severos o el colapso de la estructura.

Es decir, la idea es separar una estructura de los movimientos del suelo mediante la introducción de elementos flexibles entre la estructura y su cimentación. Los aisladores reducen notablemente la rigidez del sistema estructural, haciendo que el periodo fundamental de la estructura aislada sea mucho mayor que el de la misma estructura con base fija. Como una imagen vale mas que mil palabras, os pongo un vídeo donde se puede ver la diferencia entre una estructura sin aislador y otra con aislador.

Los disipadores sísmicos tienen como función disipar las acumulaciones de energía asegurándose que otros elementos de la estructuras no sean sobresolicitados, evitando daños a la estructura. Es decir, los disipadores sísmicos ofrecen un incremento de la amortiguación a la estructura.

En el siguiente vídeo podemos ver como se comporta una estructura con y sin disipadores sísmicos:

Los japoneses usan estos sistemas en sus edificios con regularidad. En el siguiente vídeo se puede observar como se mueven unos rascacielos de Japón con estos sistemas sísmicos,sin sufrir daños, durante el terremoto de marzo de 2011:

En futuros post os pondré unas pinceladas de cómo se calculan las estructuras con estos sistemas. Pero ya podéis imaginaros que estas estructuras no son lineales por lo que no se puede realizar un cálculo espectral y por tanto hay que recurrir a acelerogramas sintéticos. En el post anterior ( Descárgate un programa para generar Acelerómetros Sintéticos. Otra forma de calcular una estructura ante el sismo) os expliqué como generar estos acelerómetros. Os recomiendo que leáis ese post.

Espero que os haya gustado.
¿Quieres ser el primero en leer nuestros artículos?
Déjanos tu nombre y un email válido, y nosotros te avisaremos cuando hayan novedades en Estructurando

The following two tabs change content below.

# data[].attributes.attachment_link.title
Aisladores y disipadores sísmicos - Estructurando

# data[].attributes.attachment_link.description
En este post veremos dos tipos de sistemas que permiten mejorar la respuesta sísmica de las estructura: los Aisladores y los Disipadores sísmicos. Podréis ver como actúan en unos vídeos muy ilustrativos.

# data[].attributes.attachment_link.readable_text
This year's National AIA Conference on Architecture, hosted in the impressive glass atrium of the Javits Center in New York, was all about looking forwards. Technological innovation was a common thread throughout the Expo floor, as manufacturers showcased pioneering products that will form the future of construction. But as materials and building-products are made increasingly complex, it has never been more crucial for architectural workflow tools to stay up to the task for designers.

As a result, the technology zone at AIA 2018 was buzzing with activity. Thousands of architects were attracted to exhibits by the most renowned players in BIM and architectural visualization, including Autodesk, Vectorworks, Graphisoft, SketchUp and more. Here, we run through some of the tech highlights at this year's Architecture Expo to give a glimpse of what will appear on architects' screens in 2018 and beyond.

Autodesk launched BIM 360 Design, a collaborative platform that aims to realize the company's long-term vision of a single, holistic suite of design and project management tools for the construction industry. Unveiled in April this year, the software is designed to make project delivery smoother and more transparent than ever.

"BIM 360 Design fully connects the design and construction sides of Autodesk for the first time," explained Angi Izzi, Autodesk's Global Industry Strategy & Business Manager. The program effectively brings together the company's full suite of tools, placing the project at the center of the organizational matrix. Multidisciplinary teams can then track and coordinate deliverables with great transparency, collaborating in real time via the cloud.

The BIM 360 Design service builds upon a platform that is already proving popular with large-scale international firms such as AECOM. "The use of BIM allows on-going, real-time collaboration for digital design coordination reviews - saving many hours of time for all stakeholders, keeping teams focused on critical design challenges, and setting up contractors and owners for success," said Russ Dalton, Americas director of building information modeling at AECOM. "Autodesk's BIM 360 is a game-changer for AECOM and the industry."

Autodesk took its technological showcase into the real world at the Expo with a unique photoelastic pavilion, designed by Autodesk graduate interns in collaboration with Foster + Partners. The Pavilion was constructed from cross laminated layers of polarized film and plastic and designed with Dynamo with the HowickMaker plugin, illustrating the ways in which Autodesk's newest software can push the limits of material and structural innovation.

Vectorworks' latest software is Vectorworks 2018, a platform also built to harness the collaborative potential of the cloud. The software is geared towards improved efficiency for architects, Upgrades on Vectorworks' previous iterations allow uses to develop detailed 3D models "with SketchUp-like ease or Rhino-like complexity." The manipulation of complex geometries in real time is possible with the help of integrated technologies such as the Siemens Parasolid modeling kernel and Pixar's OpenSubdiv modeling library.

Highly realistic visualizations are possible thanks to the fully-integrated Maxon CineRender engine, while models can be shared and viewed with ease via the cloud and the improved Vectorworks Remote App. Vectorworks 2018 also boasts greater compatibility with augmented and virtual reality applications, as well as photogrammetry, the process of creating 3D models directly from photographs taken on site.

Not to be outdone, Graphisoft used AIA 2018 to demonstrate ARCHICAD 22, complete with expression defined property values, additional workflow improvements, parametric profiles and CineRender engine enhancements. On the big screen at Graphisoft's booth, photorealistic architectural renderings were manipulated in real time with powerful weather and lighting effects.

"Laser focus on the architect's day-to-day experience as they design drives this new version of ARCHICAD forward," explained Tracey Gatland, General Manager for GRAPHISOFT North America. "We have enhanced the Façade Design workflow so that each step an architect takes on a project, from concept through design development to documentation supporting local standards, is 100% BIM and never interferes with creativity."

AIA 2018 reinforced the fact that the driving trend for industry leaders in BIM is that of integration and collaboration. Each company appears to be working towards a holistic, one-stop-shop solution that architects can use for conceptual design, visualization, construction documentation and project management. Each piece of software becomes more multifaceted, and there is an increased focused on cross-disciplinary work - architects, engineers, environmental consultants and even contractors now expect to be able to work together seamlessly, and these programs have the potential to facilitate this like never before.

What these developments mean for companies that offer dedicated drafting and 3D modeling packages remains to be seen. Either way, continued competition between the major players in the BIM space is undoubtedly healthy, and the move towards more holistic solutions is something that architects will welcome. For more developments on architectural technology, stay tuned to Architizer during the coming months.

# data[].attributes.attachment_link.title
Autodesk, Vectorworks and Graphisoft Showcase the Latest Tech for Architects - Architizer Journal

# data[].attributes.attachment_link.description
This year's National AIA Conference on Architecture, hosted in the impressive glass atrium of the Javits Center in New York, was all about looking forwards. Technological innovation was a common thread throughout the Expo floor, as manufacturers showcased pioneering products that will form the future of construction.

# data[].attributes.attachment_link.embed_code
Disipador sísmico en edificaciones. pic.twitter.com/AMOtQyRxVA
— GeotechTips (@GeotechTips) July 4, 2018

# data[].attributes.headline
Structural steel innovations - Civil + Structural Engineer magazine

# data[].attributes.subject
Structural steel innovations - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.readable_text
Twelve building projects win AISC's top steel design awards.

In April, the American Institute of Steel Construction (AISC) recognized 12 structural steel projects in its 2018 Innovative Design in Engineering and Architecture with Structural Steel (IDEAS ²) awards program. Conducted annually, the IDEAS 2 award is the highest honor bestowed on building projects by the U.S. structural steel industry and recognizes excellence and innovation in the use of structural steel on building projects across the country.

The 12 IDEAS ² winners were selected from nearly 100 submissions received from architectural, engineering, and construction firms throughout the U.S. Each project was judged on its use of structural steel from both an architectural and structural engineering perspective, with an emphasis on creative solutions to the project's program requirements; applications of innovative design approaches in areas such as connections, gravity systems, lateral load resisting systems, fire protection, and blast; aesthetic and visual impact of the project; innovative use of architecturally exposed structural steel (AESS); technical or architectural advances in the use of the steel; and the use of innovative design and construction methods.

A panel of design and construction industry professionals identified National and Merit winners in three categories based on total constructed value: projects greater than $75 million; projects $15 million to $75 million; and projects less than $15 million. In addition, the panel awarded a Presidential Award of Excellence in Engineering to two projects for structural engineering accomplishment.

The IDEAS ² program also recognizes the importance of teamwork, coordination, and collaboration in fostering successful construction projects. Awards for each winning project are presented to the project team members involved in the design and construction of the structural framing system, including the architect, structural engineer of record, general contractor, owner, and AISC member fabricator, erector, detailer, and bender-roller. The awards are presented to the team members at ceremonies held at each of the winning projects during the year.

"We celebrate these projects and appreciate the savvy, creative people behind them for showcasing the beauty and usefulness of structural steel," said Charles J. Carter, Ph.D., S.E., P.E., president of AISC. "Our hearty congratulations to the award-winning teams for a great compilation of excellent solutions!"

Following are the 2018 award-winning projects in each category.
Projects greater than $75 million
National Award: 150 North Riverside, Chicago - The new 54-story, 1.25 million-square-foot, Class A office, pre-certified LEED Gold tower spans across seven active Amtrak lines, was constructed using cranes balanced on barges, and used lifts of the largest steel sections in the world. The tower features a narrow structure at its base and a compact footprint, which opens up to column-free floors above. Just 85 feet at its widest, the site is hemmed by the river and a 30-foot setback to the east, active Amtrak lines to the west, and Lake and Randolph Streets to the north and south. Above Level 8 (the first full floor positioned more than 100 feet above the plaza), the concrete core-supported tower looks like a typical 46-story steel-framed office building. From Levels 4 to 8, a four-story transfer truss with sloping columns "funnels" the tower out of Amtrak air-rights space on the west and onto the developer's land in a footprint equal to just 30 percent of the tower's floor area. Although not similarly restricted, the building's east side was also designed to slope inward to balance forces and provide open access to the expanding Chicago Riverwalk. All 16 sloping columns along the east and west building faces are 65-ksi W36x925 - the largest and strongest rolled steel shapes in the world. At the furthest north and south column lines, the sloping columns are part of a four-story steel truss. Each truss is supported by two mega-columns, each comprised of two W36x925 sections joined together to create an economical and compact super-column carrying 13,500 tons. Between the north and south column lines, the base of each sloping column bears on the central concrete core. Structural engineer for 150 North Riverside is Magnusson Klemencic Associates, Inc., Seattle.

National Award: World Trade Center Transportation Hub (The Oculus), New York City - The main transit hall in the new multi-billion dollar transit station at the tip of Manhattan Island will serve more than 200,000 travelers each day. The Oculus consists of two parallel arches spanning across a 300-foot-long oval-shaped opening in the transit hall roof slab, and reaches a crown height of more than 100 feet. The arches are supported by columns spaced approximately 7 feet apart - the same distance that the columns of the twin towers were spaced. The spaces between the columns and the gap between the arches are covered in glass, which allows natural light to illuminate the 90,000-square-foot main hall. The "wings" of the dove consist of variable-length rafters that extend from the arches to form a roof-like structure, the largest of which is 197 feet long (equivalent to an 18-story building). The entire structure used a total of 11,500 tons of large steelwork pieces. A sequential erection, rather than shoring, allowed the geometry and load paths to be measured throughout construction. Essential to the segmental erection process was the staged construction computer analysis model created for the project. Erection tolerances for the structural steel were exceedingly tight. In order to allow the glazing to fit properly, the steel in the arch and the columns had to be within 1/2 inch of the theoretical design location. The project team used the model to determine the cambered shape of each individual steel segment, the stresses in the structure, and the position of the geometry control points during each stage of the erection. Design architect and structural engineer is Santiago Calatrava. Managing engineer, engineer of record, managing architect, and architect of record are the Downtown Design Partnership, an STV/AECOM joint venture, in association with Parsons Transportation Group.

Merit Award: 111 Main, Salt Lake City - 111 Main suspends the entire perimeter of a 387-foot-tall, 24-story tower above an adjacent five-story theater. An air rights agreement allows the tower to extend above the theater starting at Level 5. Located in a region of high seismicity, a balanced two-way, 3D steel hat truss system at the penthouse roof level balances load and supports 18 perimeter columns and long-span steel floor framing. Six articulated structural steel bearings (typically located at a building's base for seismic isolation) support the steel hat truss system and direct the compressive gravity and lateral forces from the hat truss to the tower's high-strength concrete core walls, and accommodate temperature changes of the exposed hat truss. The hanging perimeter steel columns create open office lease spaces free of interior columns as well as a completely column-free lobby with no perimeter columns meeting the ground level. Measuring 28 feet, 1-1/2 inches deep and weighing 1,870 tons, the structural steel hat truss system extends 40 to 45 feet from the core walls. The building is tuned with longer clear spans for the 20 suspended south-side levels to balance the load of the shorter spans in the 23 suspended north-side levels. The central reinforced concrete core walls provide the tower's only connection to its complex foundation and resist all gravity loads, as well as wind and seismic vertical and lateral loads. Structural engineers are Skidmore, Owings & Merrill LLP, San Francisco, and Dunn Associates, Inc., Salt Lake City.

Merit Award: U.S. Bank Stadium, Minneapolis - Structural engineer Thornton Tomasetti teamed with Dallas-based architect HKS to make the $825 million, 66,200-seat, Minnesota Sports Facility Authority's vision of a climate-controlled, amenity-rich, multi-purpose venue a reality. Comprising more than 240,000 square feet, with some panels measuring more than 420 feet in length, the three-layer Texlon ETFE (ethylene-tetra-fluoro-ethylene) polymer film, air-pressure-stabilized pillow system covering the south-sloping roof of U.S. Bank Stadium is the largest transparent ETFE roof in North America. The stadium features five, 55-foot-wide by 75- to 95-foot-high, curtain wall-clad structural steel hydraulic mechanized pivoting wall panels. The lightweight ETFE enabled structural engineers to provide primary roof support with a single, 970-foot steel ridge truss, resulting in cost savings and a striking visual lightness. Orchestration of such a large and complex structure required the use of the software Rhino with the parametric plugin Grasshopper. The design team used Grasshopper to optimize the roof pitch and slope to minimize snow accumulation and reduce roof snow loads. Thornton Tomasetti's Advanced Project Delivery approach employs specialized connection design engineers and steel detailers working side-by-side with the structural engineering design team to conceptualize the connections early in the design phase once member geometry is set and initial force magnitudes are available. Transfer of connection design information was validated for constructability by Thornton Tomasetti's modeling the connections in the 3D fabrication software, Tekla Structures. Coordination items were addressed real-time through the use of a shared live Tekla model utilizing a Panzura system that allowed Thornton Tomasetti's engineers to work side-by-side with the fabricator's detailer.
Projects $15 million to $75 million
National Award: U.S. Air Force Academy Center for Character and Leadership Development (CCLD), Colorado Springs, Colo. - The CCLD, serving as an education and research center, features a cantilevering 105-foot Skylight consisting of diagonal steel plates composed in a triangular grid and precisely calibrated to resist lateral forces due to wind loading. This calibration was achieved by considering the deflected shape of the Skylight geometry under an inward pressure. When combined with the original geometry, this deflected shape became the inner boundary of the Skylight's steel plates, providing a varying depth across each face. The product is a triangulated system of plates of varying depth, which creates a normalized stiffness profile across each face to provide a stable base for attachment of the glazed cladding units forming the outer skin of the Skylight and allows for the optimized glass joint dimension. The AESS is devoid of all embellishment or ornamentation. Through the use of an iterative analysis and design method, structural steel was added only at locations where it was required by the performance of the structure, resulting in maximized material efficiency. Analysis of the Skylight also included consideration of both global and local buckling analyses for geometric and material non-linearity, as well as a check of stresses in the plate members to highlight the flow of loads through the structure and areas of stress concentration. Architect and structural engineer is Skidmore, Owings & Merrill LLP, New York City.

Merit Award: University of California, Davis Jan Shrem and Maria Manetti Shrem Museum of Art, Davis, Calif. - The project's signature feature is the 50,000-square-foot undulating "Grand Canopy" that covers the building and most of the remaining site. The varying angles and porosity of the canopy infill members filter and reflect sunlight. Structural steel was the best material to meet this architectural challenge. A set of irregularly shaped one- and two-story pavilions - providing gallery, studio, community, administrative, and service space - have concrete fill on metal deck diaphragms supported by steel beams and girders, with steel columns bearing on spread footings and grade beams. Steel framing efficiently supported the long-span roofs over large galleries and could be manipulated to address complicated skewed conditions, sloping and intersecting roofs, and various cantilevered regions. Buckling-restrained braced frames (BRBFs) serve as the lateral force-resisting system in the pavilions. The canopy is supported by round hollow structural sections (HSS) of varying diameters ranging in height from 15 feet to 35 feet, all supporting HSS14x10 girders and beams. They, in turn, support triangular, perforated aluminum infill beams of varying spacing, orientations, and perforations. The canopy columns are each founded on a concrete drilled pier, creating a "flag pole" system of cantilevered columns. The canopy is tied to the building pavilions, so lateral forces are shared by the cantilever columns and the BRBFs, and the canopy girders function as seismic collectors. Structural analysis used RAM Structural System for gravity design of the composite framing of the building and a SAP 2000 model that included both the building and the canopy for dynamic analyses of wind and seismic loading. Structural engineer is Rutherford + Chekene, San Francisco. Consultants include Degenkolb Engineers, San Francisco; Front, Inc., Brooklyn, N.Y.; and WSP | Parsons Brinckerhoff, San Francisco.

Merit Award: Apple Union Square, San Francisco - The addition of a new structure over a functioning below-ground ballroom and loading dock that serve the neighboring hotel required creative solutions for the existing building alterations as well as for the new structure. The new alterations are intricately woven into the existing structural fabric. The project comprises three volumes above ground - the store, the bar building, and the plaza. The unique features of the store - including tall sliding doors, a bridge-scale transfer truss, a grand cantilevered floor, a voluminous interior space, and ductile seismic bracing - were all made possible because of structural steel. A significant portion of the steel frame was constructed of wide-flange shapes, HSS, and built-up sections. The south façade has a pair of tall sliding steel-and-glass doors - some of the largest ever built - each measuring 42 feet tall by 20.5 feet wide. Special concentrically braced steel frames comprise the seismic lateral force resisting system in both directions. The braced spine is built on a substantial steel transfer truss that spans over the below-ground ballroom. The second-floor cantilever is constructed of tapered built-up steel beams, with tuned mass dampers to reduce the vibration response. Lightweight tapered steel trusses support the roof and enclose the generous interior volume. Structural engineers are Foster + Partners, London (also architect) and Simpson Gumpertz & Heger, San Francisco.

Merit Award: Daily's Place, Jacksonville, Fla. - This 5,500-seat performance venue connects a new, 94,000-square-foot indoor football training facility to EverBank Stadium, home of the Jacksonville Jaguars. Both the performance venue and training facility are covered by a fabric roof that is suspended from an exposed steel roof structure that features exposed articulated steel trusses atop a single-layer membrane hung below. Exposed V-columns around the perimeter serve as vertical load-bearing members while economically resisting hurricane-force winds. Fifty-foot-tall rolling doors make the spaces flexible, enabling the facility to host a wide variety of events. The cost-efficient marriage of exposed structural steel with a specialized, shimmering fabric membrane allows the structure to appear opaque during the day and become translucently alive at night via distinct lighting from within. To meet an accelerated timetable, the integrated project team implemented a fully digital delivery process that eliminated sequential handoffs of documents. A central information database (CID) created from the architect's Rhino model was crucial to this process. Every participant drew data from the CID, which defined the complex workpoint geometry for the entire project, feeding structural and documentation software platforms including Rhino, Revit, SAP 2000, and Tekla to seamlessly develop the raw architectural form into a fully connected Tekla model that was delivered to the successful steel bidder. Structural engineer and connection designer is Walter P Moore, Kansas City, Mo.
Projects less than $15 million
National Award: North Transfer Station Rebuild, Seattle - The station's new $12 million, 67,000-square-foot Tipping and Transfer Building superstructure was designed by a structural engineering partnership between Integrated Design Engineers and CDM Smith. The building is used to collect and sort waste destined for landfill using the flat-floor unloading and sorting method, and is equipped with noise and odor reducers and a mist sprayer that reduces dust. A 150kW solar array and a green roof covers 80 percent of the building's roof area. The building's lower-level southwest corner had to be clear of columns and walls to allow truck entrance into the building after driving down the ramp from the street. In addition, the upper-level of the building had to be column-free for its full 200-foot span. A solution called the "floating corner" comprises a 50-foot cantilever truss and a 120-foot main transfer truss system that supports the weight of the entire building at its southwest corner. The main transfer truss at the south face is supported by a double W30 beam embedded in the concrete slab on the east, and a full-story cantilever truss on the west. The full-story truss depth was selected to optimize the structural weight and allow top and bottom chord stabilization. The complexity of these trusses lies in the multiple-stage camber that ensures the trusses are at the correct elevations when the building is completed and loadings applied, as any unpredicted deflection would impact the building's tri-chorded roof trusses. The upper level of the building had to allow for a 200-foot span of open space without exceeding a roof structure depth of 7 feet (a span-to-depth ratio of L/28).

Merit Award: Riggs CAT Headquarters, Little Rock, Ark. - The new headquarters' most defining feature is a large western-facing porch. Its cantilevered tapered ends are capped with a standard galvanized steel grate cornice that lightens the edge, filters sunlight, and emulates a shovel blade lifted in the air. The new building's 163-ton steel structure acts as a large open shed, sheltering key programmatic elements while creating two distinct display (public) and activity (private) lawns. A southern roof overhang and galvanized grate balcony shield direct sunlight but allow indirect light, a key sustainable strategy. Structural engineer is Bernhard TME, Little Rock, Ark.
Presidential Award of Excellence in Engineering
Promedica Corporate Headquarters, Toledo, Ohio - ProMedica Headquarters is an adaptive reuse of two buildings: the historic Daniel Burnham-designed steam plant constructed in 1896 as well as a Brutalist bank building, both of which are sited adjacent to Promenade Park on the Maumee River at the heart of downtown Toledo. Transformation of the historic steam plant to a 124,000-square-foot office building posed numerous challenges. Inside the steam plant shell, a new four-story office space was created that utilized the existing roof and existing north, south, and west masonry walls to enclose the space.The footprint of the office building, however, extends outside the original steam plant walls toward the Maumee River on the east. Structural steel was utilized for the architectural desired openness of the headquarters, with most of this steel being exposed. The floor plan inside and outside the steam plant walls consists of large bays (50 feet by 32 feet) to maximize column-free office space. These bays were only possible using wide-flange steel composite beams with up to 2 inches of camber. These beam cambers were closely monitored while pouring the composite floor slabs (3-1/2-inch normal-weight concrete on 3-inch composite deck). Three-inch composite deck was utilized to reduce the quantity of steel pieces, reduce tonnage, and to create the minimalist industrial feel to match the history of the site. Floor-to-floor heights were also limited by the existing steam plant height, thus the majority of the floors utilize beam depths of 24 inches or less. The existing steam plant utilizes pairs of steel lattice columns at roughly 16 feet on center, which support steel roof trusses that span approximately 71 feet, 8 inches between the east and west walls. The lattice columns are set inside the existing masonry walls. Structural engineer is HKS, Inc., Dallas.

Hard Rock Stadium Shade Canopy Erection Plan, Miami Gardens, Fla. - Erecting a 14-acre structural steel shade canopy weighing more than 17,000 tons over an existing NFL stadium presented unique challenges to the project team. Structural engineers Ruby+Associates, Bingham Farms, Mich., provided full erection engineering services to fabricator/erector Hillsdale Fabricators. The canopy, designed by architect HOK and structural engineer Thornton Tomasetti, Washington, D.C., was part of a $500 million renovation of the 65,000-seat stadium. The canopy is supported by eight supercolumns. Transfer trusses spanning between pairs of supercolumns support a 350-foot-tall spire near each corner of the structure. Sixty-four structural cables, up to 5 inches in diameter and up to 300 feet long, extend from the top of the masts to suspend portions of the canopy. Ruby developed a steel erection plan requiring minimal shoring and no alterations to the existing stadium. A temporary falsework system was shoehorned into each corner of the stadium. The falsework system allowed for installation of the lower mast section and cross transfer truss. After these members were installed, the falsework was removed. To predict the construction stresses and deformations, as well as cable loading/deformation at each stage of erection, a sophisticated analytical model was prepared using SAP 2000. The SAP model accurately predicted the behavior of the extremely indeterminate structure, minimizing the number of costly and cumbersome cable readjustments.

For more information about the IDEAS ² awards and the winning projects, visit www.aisc.org/ideas2 .

Information provided by the American Institute of Steel Construction( www.aisc.org ).

# data[].attributes.attachment_link.title
Structural steel innovations - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.description
Twelve building projects win AISC's top steel design awards. In April, the American Institute of Steel Construction (AISC) recognized 12 structural steel projects in its 2018 Innovative Design in Engineering and Architecture with Structural Steel (IDEAS2) awards program. Conducted annually, the IDEAS2 award is the highest honor bestowed on building projects by the U.S.

# data[].attributes.wish_content.attachment_props.text
Recomiendo estos dos minutos y poco de mi admirado @jc_arroyo a propósito de una entrevista para @ingenioxyz donde reflexiona sobre la ingeniería estructural

# data[].attributes.wish_content.attachment_props.original_text
Recomiendo estos dos minutos y poco de mi admirado @jc_arroyo a propósito de una entrevista para @ingenioxyz donde reflexiona sobre la ingeniería estructural https://t.co/1lC0ySWXYg

# data[].attributes.attachment_link.embed_code
Recomiendo estos dos minutos y poco de mi admirado @jc_arroyo a propósito de una entrevista para @ingenioxyz donde reflexiona sobre la ingeniería estructural pic.twitter.com/1lC0ySWXYg
— Ingeniería en la Red (@ingenieriared) May 24, 2018

# data[].attributes.attachment_link.metadata.attachment_props_source.data.text
Recomiendo estos dos minutos y poco de mi admirado @jc_arroyo a propósito de una entrevista para @ingenioxyz donde reflexiona sobre la ingeniería estructural https://t.co/1lC0ySWXYg

# data[].attributes.attachment_link.metadata.attachment_props.original_text
Recomiendo estos dos minutos y poco de mi admirado @jc_arroyo a propósito de una entrevista para @ingenioxyz donde reflexiona sobre la ingeniería estructural https://t.co/1lC0ySWXYg

# data[].attributes.attachment_link.metadata.attachment_props.text
Recomiendo estos dos minutos y poco de mi admirado @jc_arroyo a propósito de una entrevista para @ingenioxyz donde reflexiona sobre la ingeniería estructural

# data[].attributes.headline
Guest blog: Importance of structural loads - Civil + Structural Engineer magazine

# data[].attributes.subject
Guest blog: Importance of structural loads - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.readable_text
By Steve Wright

In the simplest terms, the purpose of a building is to protect the occupants and contents, not only from the elements but also from the structural failure of the building. Structural failure directly impacts the safety of the occupants and contents, the converse of the building's purpose. Therefore, structural loads are important to buildings because they directly impact safety.

Unfortunately, the dueling priorities of maximum safety and economy create a fine line to balance. Most of the time, building designs meet the challenge. Sometimes, they do not because cost savings are driving the project. Designers and architects are the first line of defense for safety and should have impenetrable arguments against cost-cutting and for a complete analysis of any changes to the structural drawings.
Design load failures
The following examples of design load failures ( www.complex.com/style/2011/12/the-50-worst-architecture-fails) are extreme, but total structural failure can be caused by seemingly minimal errors as well as the stubbornness of a builder or owner.

Hotel New World, Singapore (1986) - The Lain Yak Building, also known as Hotel New World, collapsed in 1986. Upon investigation, it was discovered that, while the structural engineer calculated and designed for the building's live load, he neglected entirely to consider the dead load. This error led to the rapid collapse of a six-story building housing a hotel, bank, and nightclub. The collapse killed 33 people and entrapped 17 others.

C.W. Post College Dome Auditorium, Brookville, N.Y. (1978) - The domed coliseum collapsed under a snow load during a blizzard. The dome was compliant with all existing building codes, but the engineer only considered uniform loads, thus creating a minimally designed structure that was unable to hold the type of unequal loads of snow and ice deposited by the storm. Fortunately, there were no people in the building at the time of the collapse.

Versaille Wedding Hall, Jerusalem, Israel (2001) - The Versailles Wedding Hall originally was designed to have one, three-story side and one, two-story side. However, the owners made a change in the plans late in the construction phase. They decided to add another floor to the two-story side, exposing the former roof to greater loads than it was designed to handle.

Although partitions were added to help support the extra weight, they were removed for reasons unknown. The floor began to sag, and the owners responded by adding grout and fill, adding more weight to the unstable structure. The floor failed underneath a wedding party that was in progress, killing 23 people and injuring 380 others.
LRFD versus ASD for safely calculating loads
Jim Collins, Ph.D., P.E., at MiTek USA, Inc., provided a comparison of load and resistance factor design (LRFD) with allowable stress (or strength) design (ASD) ( www.uspconnectors.com/resources/icc-code-asd-vs-lrfd-design).

Allowable (Available) Stress Design:

ASD says that the required strength must be equal to or less than the allowable (available) strength.

The required strength is the applied load, determined by the building code or standard. Required strength represents actual loads that are expected to be applied to the structure.

The allowable (available) strength reflects the force the keeps the material stress below a predefined maximum allowable stress.

Allowable strength is the calculated nominal strength divided by a factor of safety (Ω) and represents the actual strength based on engineering principles and the appropriate design specification for the material in question.

Load Resistance Factor Design:

LRFD also states that required strength must be less than or equal to available strength; however, there is no safety factor term as there is with ASD.

The nominal strength is instead reduced by a resistance factor (ø), representing the specific material type under a specific load type. Resistance factor is often used for a specific type of failure mode or limit state.

The resistance factor considers known variations in design assumptions and fabrication or installation factors that are known to have the potential to impact the available strength negatively.

Also, the required strength is determined by increasing the applied loads based on how they are combined, which increases the expected applied loads and their effects that closely balances the LRFD available strength.

The increased loads increase the expected applied loads and acknowledge uncertainties about dynamic, time-variable transient loads, using individual load factors to increase them when combined with other loads.

Load factors also reflect the possibility of overload and probability of maximum transient peaks that may be different when acting in combination with other loads.

In Collins's opinion, because LRFD uses load factors that increase the "required strength" on the left of the equation, this method of load determination contains a dynamic safety factor and results in a stronger structure for more highly dynamic loads than ASD.
Importance of continuous education in structural engineering
Understanding and designing for structural loads are critical to constructing a building that meets its primary purpose - safety. Not only must a building maintain a safe environment for the occupants, but it must keep the surrounding community safe from the release of toxic or explosive contents.

Essential facilities must withstand structural loads to continue to perform a service, such as protecting standby power generation equipment or government operations.

Local building codes are modified to include typical conditions within the geographic area and act as a reminder to designers of the typical loads expected. However, failures still occur.

According to M. Kevin Parfitt ( www.mdpi.com/2075-5309/2/3/326/buildings-02-00326.pdf), interim department head of Architectural Engineering at Pennsylvania State University, following the building codes may not be enough. He feels that continuous education (as opposed to continuing education) is the answer to the historical loss of institutional memory.

Each designer increases his or her knowledge throughout a career, but that knowledge is not always passed along to others. Continuing education impacts a single person, but that education must be learned anew by the next designer through making similar mistakes.

Unfortunately, passing knowledge down to the next generation of designers is made difficult by the fear of exposing errors to the public and through the action of non-disclosure agreements.

Parfitt stresses that the industry must determine a method of sharing information, if only generically, through comprehensive failure dissemination and must develop educational repositories. Progress is being made in the form of the NIST Disaster and Failure Events Data Repository, but more work is needed. Individual diligence in self-education about failure causes and things that go wrong on a project is necessary. Experienced designers must mentor younger designers so they can learn from prior experiences and mistakes.

Structural loads are at the heart of structural safety calculations. A building that is designed without safety in mind is at risk of failing to fulfill its essential purpose.
Steve Wright works for Whirlwind Steel (www.whirlwindsteel.com), a manufacturer of pre-engineered metal building and steel building components.

# data[].attributes.attachment_link.title
Guest blog: Importance of structural loads - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.description
By Steve Wright In the simplest terms, the purpose of a building is to protect the occupants and contents, not only from the elements but also from the structural failure of the building. Structural failure directly impacts the safety of the occupants and contents, the converse of the building's purpose.

# data[].attributes.headline
Madera Laminada Cruzada (CLT): qué es y cómo usarla | Plataforma Arquitectura

# data[].attributes.subject
Madera Laminada Cruzada (CLT): qué es y cómo usarla | Plataforma Arquitectura

# data[].attributes.headline
Así se cortan los troncos para obtener distintas apariencias y utilidades en la madera | Plataforma Arquitectura

# data[].attributes.subject
Así se cortan los troncos para obtener distintas apariencias y utilidades en la madera | Plataforma Arquitectura

# data[].attributes.headline
¿Por qué la torre de Pisa sigue en pie (inclinada) tras más de 600 años y cuatro fuertes terremotos? - BBC Mundo

# data[].attributes.subject
¿Por qué la torre de Pisa sigue en pie (inclinada) tras más de 600 años y cuatro fuertes terremotos? - BBC Mundo

# data[].attributes.attachment_link.readable_text
Un misterio tenía desde hace años intrigados a los ingenieros: ¿cómo es capaz de resistir los terremotos la torre de Pisa, inclinada como está?

Teniendo en cuenta que se inclina en un ángulo de cinco grados, lo que resulta en una desviación más que perceptible desde cinco metros y que tiene 58 metros, la pregunta parece lógica.

La Toscana, además, donde se sitúa la famosa torre, es una región altamente sísmica, al igual que gran parte de Italia, por la colisión de dos de las grandes placas tectónicas de nuestro planeta: la africana y la euroasiática.

Viaje en 3D al interior de la Torre de Pisa

"La mitad del pueblo ya no está": al menos 250 muertos por terremoto de magnitud 6,2 en el centro de Italia

Un segundo terremoto sacude a Italia en menos de dos horas

Desde los inicios de su construcción, en el siglo XII, ha resistido al menos cuatro grandes terremotos pero, al contrario que muchos otros edificios modernos en la zona, sigue en pie.

Un equipo de 16 ingenieros de la Universidad Roma Tre y de la Universidad de Bristol, en Inglaterra, se propusieron desvelar el misterio y lo han encontrado: la culpa (y la salvación) está en el suelo.

Un suelo blando

Tras estudiar la información sismológica, geotécnica y estructural de todos estos siglos que han encontrado disponible, los investigadores aseguran que se debe a un fenómeno conocido como "interacción dinámica entre suelo y estructura" (DSSI, por sus siglas en inglés).

Es decir, se trata de una combinación entre las características del terreno en el que se erige la torre y la estructura y altura de la misma. Por un lado el terreno sobre el que se levanta es blando, y por otro la estructura alta y rígida. Todo esto hace que la resonancia de los movimientos sísmicos sea mucho menor.

Esta ha sido, según un comunicado emitido por la Universidad de Bristol, la clave de su supervivencia. La torre inclinada de Pisa tiene un récord mundial de efectos DSSI, dice este equipo de ingenieros.

"Irónicamente, el mismo suelo que causó la inclinación de la torre y la llevó al borde del colapso, puede decirse ahora que le ha ayudado a superar los episodios sísmicos", dijo el profesor Mylonaki, experto en ingeniería sísmica y geotécnica de la Universidad de Bristol.

La Torre no está libre del colapso a causa de su inclinación pero esta investigación sí arroja algo de luz a por qué, a pesar de su desvío, el edificio no sucumbió a los terremotos.

Los resultados serán presentados formalmente en la Conferencia Europea de Ingeniería de Terremotos que se celebra el próximo mes de junio en Tesalónica, Grecia.
Ahora puedes recibir notificaciones de BBC Mundo. Descarga la nueva versión de nuestra app y actívalas para no perderte nuestro mejor contenido.

# data[].attributes.attachment_link.title
¿Por qué la torre de Pisa sigue en pie (inclinada) tras más de 600 años y cuatro fuertes terremotos?

# data[].attributes.attachment_link.description
Una torre de 58 metros del siglo XII y apreciablemente desviada no tenía muchas expectativas de sobrevivir los movimientos sísmicos que han asolado la península itálica desde el año 1280, pero ahí sigue. Y ahora han descubierto el por qué.

# data[].attributes.headline
New York ‘Super Slender’ - Civil + Structural Engineer magazine

# data[].attributes.subject
New York ‘Super Slender’ - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.readable_text
Designed by architectural firm RB Systems ( www.rb-systems.us ), founded in 2016 by Rustem Baishev, 265 West 45th Street proposes a tower typology that has recently emerged in New York City - the "Super Slender." To be located on a small, currently vacant site on West 45th St., the building's footprint would measure approximately 98 feet by 98 feet, with the tower rising to more than 1,300 feet tall, and provide modern, ergonomic, sustainable office spaces for multi-floor corporate tenants. The project is another take on a path that skyscraper design will likely be following in the coming years to meet challenges of constrained and dense city centers with their shortage of large vacant lots, yet ever-growing demand for new properties.

The tower's structural system solely determines its appearance. Because of the constrained site, the choice was made to eliminate perimeter columns and substitute them with a set of steel cables that run and twist along the height of the tower, allowing for an ultralight, yet sturdy structural assembly. The cables are anchored in a deep foundation, MEP zones, and tied back to the core at the upper structural ring. According to the architect, the spiral arrangement of the cables - the "twist" - creates a force of surface tension, resulting in a "corset" holding the insides contained, similar to a candy that is held inside a wrapper because its ends are twisted.

Architecturally, it becomes an expression of the building's structure - a sleek, minimal, and futuristic volume of reflective glass, a cylindrical tube that is also one of the most efficient shapes for wind resistance. It is also abstract, and aligns with technology-oriented aesthetics. Solutions such as circulating elevators and a multi-story lobby with automatic visitors' dispatch systems connected to their mobile devices allow higher occupancy rates than typical office buildings.

Due to extremely dense spatial arrangement of the tower, a solution for locating a multi-ton tuned mass damper had to be non-trivial. The idea was to design a toroidal damper, which will not take up space directly on top of the core, to leave it free to locate elevator overruns and to provide continuity of evacuation paths such as stairs inside the core. Thus, the damper circles the core with even distribution of mass, and is software controlled to counteract sways caused by high-velocity winds.
Redefining the street
One of the most distinctive features of the design is the "Halo" canopy - a toroid volume above the entrance plaza. Clad in reflective glass on the sides and in bead-blasted chrome panels at the front and back, it subtly reflects the surroundings.

The entrance lobby, which greets visitors with an austere multi-story space, is a first glimpse into the tower's modern, technology-driven interiors. Surrounded by the dark canyon of Midtown, it still relies heavily on artificial lighting. In double-deck elevators, visitors reach an observation deck at level 96, which provides 360-degree unobstructed views of the city.
High-performance façade
A distinctive feature of the tower, the façade was scripted in parametric software to wrap the smooth and curvilinear shape of the building, and panelize it into flat panels comprised of paired triangles. The slim (only 500 mm in height) spandrel extends from the glazing panel above to allow for continuity of glass reflections and prevention of leakage. Each panel is tilted 1 degree toward the inside of the building. The boxes in which the cables run are capped by aluminum stamped panels with integrated and software-controlled rotating vents for natural ventilation/conditioning. Tapered slab ends allow for more daylight penetration, yet high-performance glass coating blocks excessive thermal gain.
Ergonomic workplace
As part of the tower's integrated design approach, the furniture was also engineered to fit the space precisely. Due to the recently formulated risks that prolonged sitting poses on worker health, the space is equipped with ergonomic, sit-stand transformable furniture. The desks hang from the ceiling on gas-lift arms, which allow for easy individual adjustment of their height and rotation/position, as well as quick office layout reconfiguration based on tenant needs. Digital communication systems and video conference equipment allow a multi-floor tenant to cooperate effectively, freeing the staff from frequent travels between the floors.

Information provided by v2com ( www.v2com-newswire.com ), an international newswire specializing in design, architecture, and lifestyle. See additional renderings at www.rb-systems.us/projects#/265-w-45-st .

# data[].attributes.attachment_link.title
New York 'Super Slender' - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.description
Designed by architectural firm RB Systems (www.rb-systems.us), founded in 2016 by Rustem Baishev, 265 West 45th Street proposes a tower typology that has recently emerged in New York City - the "Super Slender." To be located on a small, currently vacant site on West 45th St., the building's footprint would measure approximately 98 feet by ...

# data[].attributes.headline
La torre de madera más alta del mundo se construye en Noruega | Plataforma Arquitectura

# data[].attributes.subject
La torre de madera más alta del mundo se construye en Noruega | Plataforma Arquitectura

# data[].attributes.attachment_link.readable_text
En los últimos meses, hemos visto un aumento en las grandes estructuras de madera que se están construyendo en todo el mundo, afirmando ser las más grandes, las más altas o las primeras de su clase -por ejemplo, los planes para Dutch Mountains, el edificio de madera más grande del mundo, ha sido revelado recientemente.

Uno de los impulsores clave de este cambio es Moelven Limtre, quienes han vuelto común la percepción de la madera como material de carga. Su director, Rune Abrahamsen, es responsable de uno de los solicitantes actuales del récord mundial del edificio de madera más alto, "Treet" en Bergen, a 51 metros de altura. Sin embargo, el último proyecto del contratista Mjøstårnet está configurado para alcanzar una altura aún más alta de 81 metros.

+ 11

La construcción de Mjøstårnet en Brumundal, una pequeña ciudad en Noruega, comenzó a principios de septiembre y se completará en marzo de 2019.

Diseñado por Voll Arkitekter, el edificio de 18 pisos incluirá más de 11.300 metros cuadrados de espacio que contiene departamentos, un hotel, un restaurante, oficinas y áreas comunes con una sala de natación de 4.700 metros cuadrados. Mjøstårnet tiene un ancho de base de 16 metros, pero Abrahamsen cree que es posible construir más alto si esto se incrementa:

Es principalmente el ancho lo que determina qué tan alto podemos construir un edificio de madera, pues esto significa que la estructura se balancea menos. Un edificio más amplio no generaría problemas para construir a más de 100 metros, e incluso 150 metros o más

La capacidad de crear rascacielos sin madera es un punto de referencia para la construcción sostenible. Como iniciador del proyecto, Arthur Buchardt explica en el primer video de la serie Nordic Heights, que el abastecimiento del abeto a nivel local ha reducido drásticamente la huella de carbono del edificio, así como la simple producción de columnas y vigas laminadas que requieren poca energía para formar la principal estructura del edificio.

La madera a menudo ha sido cuestionada debido a conceptos erróneos pero comunes sobre su capacidad para resistir el fuego. Sin embargo, es posible localizar los haces de la madera laminada para que no se afecten mutuamente, según Abrahamsen:

El problema principal en la construcción es la propiedad ligera del marco de madera que puede oscilar hasta 140 milímetros en la parte superior cuando se enfrenta a los fuertes vientos de la región. Para eliminar este problema, las losas de piso de concreto se usarán en los siete pisos superiores para aumentar el peso hacia la parte superior y ralentizar el balanceo. El edificio también estará anclado en el suelo con pilas de hasta 50 metros de profundidad.

Pero a medida que asciende la competencia por la estructura de madera más alta, las nuevas reglas sugeridas para el Consejo de Edificios Altos y Hábitat Urbano (CTBUH) parecen ser adoptadas pronto, indicando que los edificios de madera con núcleos de concreto se definen como híbridos de madera-hormigón. Si se ponen en práctica estas nuevas reglas, descartarán HoHo Tower en Viena y Brock Commons en Vancouver como rascacielos de madera, dejando abierta la oportunidad para que Mjøstårnet establezca el récord mundial, hasta que llegue el siguiente competidor.

# data[].attributes.attachment_link.title
La torre de madera más alta del mundo se construye en Noruega

# data[].attributes.attachment_link.description
En los últimos meses, hemos visto un aumento en las grandes estructuras de madera que se están construyendo en todo el mundo, afirmando ser las más grandes, las más altas o las primeras de su clase -por ejemplo, los planes para Dutch Mountains, el edificio de madera más grande del mundo, ha sido revelado recientemente.

# data[].attributes.headline
2018 ENGINEERING DRONE VIDEO OF THE YEAR AWARD - Civil + Structural Engineer magazine

# data[].attributes.subject
2018 ENGINEERING DRONE VIDEO OF THE YEAR AWARD - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.readable_text
Here at Civil + Structural Engineer magazine it has been amazing to witness how quickly UAV and drone applications have become integrated into the AEC industry, with many firms either hiring or partnering with FAA-certified pilots and video production teams to produce dynamic marketing materials, document project phases, andcreate 3D models. The amount of interest and content related to UAV has grown so fast that we created a focused section of our website and print magazine on the topic ( www.csengineermag.com/category/uav-surveying/ ).

A drone video contest was the perfect excuse for us to get a look at some of the work that our industry is doing. So we created the Engineering Drone Video of the Year Award (EDVY). The stakes were high with a $500.00 prize for the winner of the award. And it came as no surprise the level of quality of all the submissions.

Aerial Buzz, a division of Spiracle Media ( www.spiraclebuzz.com ) based out of Charlotte, N.C., claimed the award with their dynamically produced video packed with a variety of aerial angles overlooking the features of the Atherton Mill site. Aerial Buzz worked with Engineering Consulting Services (ECS) to document and produce the video.

"It is unique to work with a firm that is trying to maintain the character of the property while adding to a vibrant part of the city. I thoroughly enjoyed flying around the tall brick South End chimney and classic railroad line. My favorite part has been watching the property grow from the bare ground, to columns and structures in place, to finally a completed six-level parking deck, completed stores, and living spaces," said Thomas Wilson, director of Drone Operations and creative specialist for Aerial Buzz and the UAV pilot for the winning video.
The changes I've seen
We had a chance to ask Wilson and the other finalists how the industry has changed since they first became involved and where they think it will be in the next five years.

"I started in April 2012 with a Phantom 2 with a three-axis gimbal and a Go Pro camera. Fast forward eight versions later and I'm flying a Phantom 4 Pro. Since 2014, DJI has manufactured three types of Inspires, three types of Mavics, two types of Matrices, the Spark, and most recently, the Mavic Air. The drone field is certainly saturated when it comes to drones available for purchase," said Wilson.

ERO Architects began using aerial drone videos over three years ago. "We bought the equipment to highlight the construction status of our buildings as they go through each phase of their progress until they are completed for the final owner to move in. We have seen more videos produced now with aerial drone shot perspectives. They are becoming as common as a shot with a camera on a tripod," said Brian Godinez, principal and chief marketing officer for ERO Architects.

The next five years

There is agreement among the finalists that Federal Aviation Administration (FAA) regulations will be changing. "There is a big push to get the FAA to be less strict on flights over people and to allow flights beyond visual line of sight (VLOS). You could accomplish so much from an inspection/mapping/search and rescue standpoint if VLOS was loosened. If future drones are built to be more efficient and the potential risk of injury from a crash is lessened, then I can see the FAA giving out more waivers to certified pilots. This would change the game when it comes to expansive capabilities," said Wilson. He also sees the number of pilots decreasing over the coming years.

"I think you'll see more and more drone pilots being downsized by two things.

"First, I think autonomous drones are the future. It might be two to three years from now or it could be 10 years from now. As drone technology evolves, the pilot is going to be minimized to just maintaining flight safety. You can already see it in some of our current applications. When I go to map a construction site, I build a flight path in an application such as DroneDeploy. Once I arrive on scene, I set up the drone, go through my pre-flight checklist and then hit one button. The drone flies the mission without me touching a single control. The key to being successful in the future comes down to experience and knowing how to capture the data using an array of tools.

"Secondly, the barrier to entry is low right now to fly legally. To get your drone license, you pay $150 for the test. If you pass, you have to purchase a drone and get basic liability insurance. All in all, that isn't very much. If and when the FAA starts to enforce illegal drone flying, that will only benefit the people currently in the field doing it the right way. Fines are pretty hefty if you don't follow the proper rules and laws. When the FAA starts to come down on people flying over 400 feet, or commercial operators posing as hobbyists, then you will see a number of people give up because it's not worth the risk. A lot of people considering this field decide against it because of the complexities of drone technology, understanding the waiver/authorization process, the complicity of airspace knowledge, etc. The people who get in early and establish a reputation of operating properly will be standing in a great spot in the future."

It is clear that this is a fast moving industry and I think we can expect future submissions to the EDVY award contest to continue to become more and more impressive. Congratulations to Aerial Buzz, ERO Architects, and CCA Techos. Be on the lookout for information on next year's contest.

DONOVAN BRIGHAM is the art director of Civil + Structural Engineer magazine ( www.csengineermag.com ). He can be contacted at dbrigham@zweiggroup.com .
Aerial Buzz
Charlotte, North Carolina

Website: www.spiraclebuzz.com
ERO Architects
McAllen, Texas

Website: www.goero.com
CCA Techos
Guadalajara, Mexico

Website: www.ccatechos.com/

# data[].attributes.attachment_link.title
2018 ENGINEERING DRONE VIDEO OF THE YEAR AWARD - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.description
Here at Civil + Structural Engineer magazine it has been amazing to witness how quickly UAV and drone applications have become integrated into the AEC industry, with many firms either hiring or partnering with FAA-certified pilots and video production teams to produce dynamic marketing materials, document project phases, and create 3D models.

# data[].attributes.headline
Robots cooperate in timber construction - Civil + Structural Engineer magazine

# data[].attributes.subject
Robots cooperate in timber construction - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.readable_text
At Spatial Timber Assemblies, man and machine work together both in the planning and in the manufacturing process. Photo: NFS Digital Fabrikation / Roman Keller
Researchers from ETH Zurich are using a new method for digital timber construction in a real project for the first time. The load-bearing timber modules, which are prefabricated by robots, will be assembled on the top two floors at the DFAB HOUSE construction site.
The range of possibilities for traditional timber construction is extended by the new process for digital timber construction. Video: NCCR Digital Fabrication
Digitalization has found its way into timber construction, with entire elements already being fabricated by computer-aided systems. The raw material is cut to size by the machines, but in most cases it still has to be manually assembled to create a plane frame. In the past, this fabrication process came with many geometric restrictions.

Under the auspices of the National Centre of Competence in Research (NCCR) Digital Fabrication, researchers from ETH Zurich's Chair of Architecture and Digital Fabrication have developed a new, digital timber construction method that expands the range of possibilities for traditional timber frame construction by enabling the efficient construction and assembly of geometrically complex timber modules. Spatial Timber Assemblies evolved from a close collaboration with Erne AG Holzbau and will be used for the first time in the DFAB HOUSE project at the Empa and Eawag NEST research and innovation construction site in Dübendorf. It is also the first large-scale architectural project to use the construction robots developed by ETH Zurich's new Robotic Fabrication Laboratory.
Robotic precision
The robot first takes a timber beam and guides it while it is sawed to size. After an automatic tool change, a second robot drills the required holes for connecting the beams. In the final step, the two robots work together and position the beams in the precise spatial arrangement based on the computer layout. To prevent collisions when positioning the individual timber beams, the researchers have developed an algorithm that constantly recalculates the path of motion for the robots according to the current state of construction. Workers then manually bolt the beams together.

Unlike traditional timber frame construction, Spatial Timber Assemblies can manage without reinforcement plates because the required rigidity and load-bearing result from the geometric structure. Not only does this save material; it also opens up new creative possibilities. A total of six spatial, geometrically unique timber modules will be prefabricated in this way for the first time. Lorries will then transport them to the DFAB HOUSE construction site at the NEST in Dübendorf, where they will be joined to build a two-story residential unit with more than 100 square meters of floor space. The complex geometry of the timber construction will remain visible behind a transparent membrane façade.
Integrated digital architecture
The robots use information from a computer-aided design model to cut and arrange the timber beams. This method was specially developed during the project and uses various input parameters to create a geometry consisting of 487 timber beams in total.

The fact that Spatial Timber Assemblies is being used for digital fabrication and also in design and planning offers a major advantage according to Matthias Kohler, Professor of Architecture and Digital Fabrication at ETH Zurich and the man spearheading the DFAB HOUSE project: "If any change is made to the project overall, the computer model can be constantly adjusted to meet the new requirements. This kind of integrated digital architecture is closing the gap between design, planning and execution."

ETH Zurich has already completed a successful collaboration with Erne AG Holzbau on the robot-built timber roof of the Arch_Tech_Lab at the Hönggerberg campus. Thanks to Spatial Timber Assemblies, the company's expertise in timber construction will make yet another contribution to ETH research.

Kohler believes in the synergy effect brought about by the partnership: "Digital fabrication depends on the tremendous expertise required for craftsmanship. Conversely, digitalization can improve craftsmanship and open up new opportunities." Kohler also says the fact that scientific disciplines go hand in hand with industry is essential if technologies are to be used in real architectural projects after such a brief time.
DFAB HOUSE - Digitally designed, planned and built
Eight ETH Zurich professors are working together with industrial partners to build DFAB HOUSE, a three-story residential unit that is part of Empa and Eawag's NEST research and innovation platform in Dübendorf. The fabrication of the mesh mould wall in May 2017 was the starting shot for the world's first building to combine multiple innovative digital construction processes under a single roof.

Since then, two other digitally designed and fabricated building components were made ready for production and coordinated digitally within the overall project. The automated Smart Dynamic Casting coordination system has already been used at ETH to prefabricate concrete façade posts designed specifically for the loading conditions of the building's glass façade.

A so-called "smart slab," a statically optimized concrete floor slab, is currently in pre-production. Researchers are using large-format 3D sand printing for its formwork. By bringing these elements together with Spatial Timber Assemblies, a unique combination will be materialising at DFAB HOUSE - which will open in autumn 2018.

# data[].attributes.attachment_link.title
Robots cooperate in timber construction - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.description
Researchers from ETH Zurich are using a new method for digital timber construction in a real project for the first time. The load-bearing timber modules, which are prefabricated by robots, will be assembled on the top two floors at the DFAB HOUSE construction site.

# data[].attributes.headline
MX3D completes the world's first 3D-printed steel bridge | Inhabitat - Green Design, Innovation, Architecture, Green Building

# data[].attributes.subject
MX3D completes the world's first 3D-printed steel bridge | Inhabitat - Green Design, Innovation, Architecture, Green Building

# data[].attributes.attachment_link.readable_text
View Slideshow

Dutch technology company MX3D just officially unveiled the world's first 3D-printed stainless steel bridge. It took four robots, nearly 10,000 pounds of stainless steel, about 684 miles of wire, and six months of printing to build the sinuous, undulating structure, which looks like it's straight out of a science-fiction movie.

The MX3D Bridge, designed by Joris Laarman Lab, is around 41 feet by 20 feet, and it's made from a new kind of steel. 3D-printing created a ribbed surface as robots added layers upon layers; Gizmodo said it could be buffed out, but MX3D plans to keep the unique, rough look.
Related: World's first 3D-printed bridge opens in the Netherlands
Laarman told Gizmodo it's strange to glimpse the bridge in their workshop: "It's a little bit like being in a science fiction story because it looks so different than everything else around. We work in a highly industrial shipyard where everything is geometric in shape, but this bridge doesn't have a single straight line."

MX3D's goal for the bridge project is "to showcase the potential applications of our multi-axis 3D-printing technology," according to their website. They say they serve architecture, maritime and offshore, and heavy duty industry markets. There's that spark of sci-fi on their About page too: their ultimate vision is robots creating lightweight constructions - not just bridges, or buildings, but Mars colonies as well.

The company credits Arup for structural engineering, Heijmans as their construction expert, and AcelorMittal for metallurgical expertise, to name a few; several other companies and universities have been involved in the bridge project.

MX3D's bridge is to be installed over the Oudezijds Achterburgwal canal in Amsterdam, possibly in 2019. Before that, the bridge will undergo load tests. Co-founder Gijs van der Velden told Gizmodo they recently tested it with 30 people, and it behaved as it should. He told Gizmodo, "[Amsterdam city officials] have collaborated with us, Arup, and Imperial College London to define a method for evaluating the safety of the bridge as, of course for a novel production like this, there is no standard code. Their open attitude towards such a new and unconventional project was essential to make this project a success."

Via Gizmodo
Images courtesy of MX3D, Joris Laarman Lab, Adriaan de Groot, Thijs Wolzak, and Olivier de Gruijter

# data[].attributes.attachment_link.title
The world's first 3D-printed steel bridge looks like it came from another planet

# data[].attributes.attachment_link.description
View Slideshow Dutch technology company MX3D just officially unveiled the world's first 3D-printed stainless steel bridge. It took four robots, nearly 10,000 pounds of stainless steel, about 684 miles of wire, and six months of printing to build the sinuous, undulating structure, which looks like it's straight out of a science-fiction movie.

# data[].attributes.attachment_link.readable_text
Llevamos unos meses publicando cada día, en nuestra cuenta de Twitter, @Estructurando, los datos básicos y foto formal de algún puente singular con el hashtag "#Puentedeldía ". La acogida de esta iniciativa ha sido muy positiva y me ha permitido ponerme al día en puentes singulares.

Una de las sorpresas al realizar este divertimento ha sido encontrarme con estructuras realmente curiosas y, a veces, gratamente deliciosas. En este post os describo una de estas estructuras que me tiene fascinado por su singularidad, belleza y, sobretodo, por su forma de concepción. Se trata del Puente sobre el río Basento, en Potenza (Italia) del Ingeniero Sergio Musmeci.

Sergio Musmeci (1926-1981) fue un ingeniero civil e ingeniero aeronáutico italiano que para este puente utilizó un nuevo paradigma en la concepción estructural. Normalmente, el proceso de concepción estructural de un puente consiste en, más o menos, las siguientes fases:

Adopción de una tipología estructural tipificada a partir de las condiciones de la obra

Aportación de una geometría estimada de los elementos de la obra (lo que llamamos predimensionamiento) .

Proceso iterativo que consiste en realizar el cálculo de la estructura y comprobar la viabilidad de la geometría propuesta (grado de seguridad), cambiando la geometría de los elementos que no cumplan. El modelo inicialmente propuesto sufre una serie de trasformaciones geométricas en este proceso iterativo hasta llegar a una forma válida y óptima.

Se podría decir que según esta vía, el cálculo es una herramienta más del proceso de diseño.

Sin embargo, Sergio Musmeci pensó en otro proceso. Le dio la vuelta a la tortilla e ideó un método en el que el cálculo era el que diseñaba la estructura, es decir, un método que obtiene una estructura específica, no tipologizada, a partir de las cargas y sin conocer inicialmente el resultado final. De esta manera, la forma estructural resultante explicaría visualmente la manera de trabajar de ella misma. Es decir, su proceso que tendría las siguientes fases:

Partir de las acciones sobre la estructura y condicionantes especiales de la obra

Búsqueda geométrica de la estructura que asuma unas tensiones límites (definidas por el material y que define en sí el grado de seguridad estructural) y que cumplan unas restricciones prefijadas del tipo:

Menor cantidad de material

Criterios de minimización del coste constructivo

La obra así concebida es este Puente sobre el río Basento construido entre 1972 y 1974 en Potenza (Italia):

Se trata de dos estructuras superpuestas, la primera es la losa superior, condicionada por el paso de vehículos y formada por una losa plana que descansa sobre la segunda estructura en 32 apoyos puntuales. Esta segunda estructura es una superficie de doble curvatura de 0,30 m de espesor formando cuatro arcos de 69,20 m de luz y apoyada en bases cuadradas de 10,38 m de lado. La longitud total del puente es de 280 m.

Para el diseño de la estructura, Musmeci resolvió una ecuación diferencial de superficie que minimizaba la cantidad de material imponiendo las tensiones máximas en el hormigón. Decidió usar superficies con la condición de que las curvaturas principales que definían en cada punto la geometría de esta fueran iguales y de signo contrario.

De manera paralela al cálculo, construyó varias maquetas para la validación del modelo. Una de ellas, de neopreno, podemos verla aquí:

Otra, de metacrilato, a escala 1:100 :

Y otra algo más grande, escala 1:10 y de microcemento podemos verla aquí:

En esta se pudo comprobar (en el Instituto Experimental para los modelos y Estructuras de Bérgamo) que las tensiones registradas en todos los puntos de la estructura eran similares.

Inicialmente se pensó aprovechar el espacio resultante entre el tablero y la estructura para el paso de una pasarela, pero finalmente no se llevo a cabo. Hubiera quedado algo así:

Por último, recalcar que el coste final del puente fue similar al de otras tipologías mas convencionales.

Os dejo varias fotografías que he encontrado de este puente y el Street View de su ubicación donde podéis hacer un recorrido por sus alrededores.

-Un puente de Musmeci sobre el río Basento: una obra singular en el panorama arquitectónico del siglo XX. Agustín Lacort.

- Wikipedia y Wikiarquitectura

Espero os haya gustado tanto como a mi.

¿Quieres ser el primero en leer nuestros artículos?
Déjanos tu nombre y un email válido, y nosotros te avisaremos cuando hayan novedades en Estructurando

The following two tabs change content below.

# data[].attributes.attachment_link.title
Cuando el Cálculo es la herramienta del Diseño: el Puente sobre el Basento de Sergio Musmeci - Estructurando

# data[].attributes.attachment_link.description
Llevamos unos meses publicando cada día, en nuestra cuenta de Twitter, @Estructurando, los datos básicos y foto formal de algún puente singular con el hashtag "#Puentedeldía ". La acogida de esta iniciativa ha sido muy positiva y me ha permitido ponerme al día en puentes singulares.

# data[].attributes.wish_content.attachment_props.text
Cuando calculeis, no olvideis el viento 😲🤤😨

# data[].attributes.wish_content.attachment_props.original_text
Cuando calculeis, no olvideis el viento 😲🤤😨 https://t.co/NpxVdAoKIb

# data[].attributes.attachment_link.embed_code
Cuando calculeis, no olvideis el viento 😲🤤😨 pic.twitter.com/NpxVdAoKIb
— Estructurando (@Estructurando) May 31, 2017

# data[].attributes.attachment_link.metadata.attachment_props_source.data.text
Cuando calculeis, no olvideis el viento 😲🤤😨 https://t.co/NpxVdAoKIb

# data[].attributes.attachment_link.metadata.attachment_props.original_text
Cuando calculeis, no olvideis el viento 😲🤤😨 https://t.co/NpxVdAoKIb

# data[].attributes.attachment_link.metadata.attachment_props.text
Cuando calculeis, no olvideis el viento 😲🤤😨

# data[].attributes.headline
How This Tiny Tank Could Help Keep Construction on Track

# data[].attributes.subject
How This Tiny Tank Could Help Keep Construction on Track

# data[].attributes.attachment_link.readable_text
The larger the construction project, the more ways there are for it to go wrong. To make matters worse, even a small mistake can lead to serious delays and other problems down the line, which is why it's super important to be able to identify those mistakes early.

A new startup called Doxel hopes to solve this problem, by combining artificial intelligence with robots and LIDAR to scan construction sites and identify problems. Doxel uses a combination of aerial drones and ground robots, equipped with HD cameras and LIDAR that can see through walls, to comb over every inch of a construction site every day.

Then, that data is analyzed by an AI and compared to plans, blueprints, and schedules to see whether everything is going smoothly. If something is built or installed wrong, or if the workers are behind schedule, the AI can detect and highlight it.

The CEO of Doxel, Saurabh Ladha, hopes that this technology can be used to save time and money during large construction projects, which are often subject to overruns. With Doxel's tech, however, even the biggest projects should be able to stay on track.

Source: Engineering.com

# data[].attributes.attachment_link.title
How This Tiny Tank Could Help Keep Construction on Track

# data[].attributes.attachment_link.description
The larger the construction project, the more ways there are for it to go wrong. To make matters worse, even a small mistake can lead to serious delays and other problems down the line, which is why it's super important to be able to identify those mistakes early.

# data[].attributes.headline
USGS issues report on seismic hazard, risk, and design for South America - Civil + Structural Engineer magazine

# data[].attributes.subject
USGS issues report on seismic hazard, risk, and design for South America - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.readable_text
Reston, Va. - South America is one of the most earthquake-prone regions of the world and has witnessed tremendous losses throughout recorded history. A recently released U.S. Geological Survey (USGS) report provides probabilistic tools to help engineers assess seismic hazards, risk, and building code requirements, potentially saving lives and dollars.

During the last century, earthquakes have caused billions of dollars of damage and tens of thousands of casualties across the northern and western part of the South American continent. The seismic activity in this continent is driven by the South American Subduction Zone and other complex fault interactions. Future human and financial losses can be mitigated through making informed decisions based on where future earthquakes may occur, how often they might occur, and how strong the ground will shake. Such information is the purpose of probabilistic (i.e., based on a mathematical forecast) seismic hazard models that are applied in building codes, insurance models, and public policy.
New data provides new opportunities
For the past couple of decades, the USGS has been collaborating with South American colleagues to develop models and maps to support nationwide emergency planning efforts. While there are a number of in-country studies that have evaluated earthquake shaking hazard and risk, the coverage is hardly uniform or complete across the South American continent. This report is the first to apply standardized methodologies and tools for hazard and risk assessments, to reduce discrepancies at national borders, and to identify areas of high hazard and risk within each country. The study relies on five important datasets and methodologies:

(1) an updated USGS earthquake catalog (ComCat),

(2) models of known and mapped faults generated by USGS over the past 30 years in collaboration with scientists from South America,

(3) the latest seismic ground motion models applied in the USGS hazard maps,

(4) USGS PAGER vulnerability models ("PAGER" stands for the Prompt Assessment of Global Earthquakes for Response, and it is a system that provides fatality and economic loss impact estimates following significant earthquakes worldwide), and

(5) methods applied in U.S. building codes. This information can be used to identify areas of high hazard and to develop strategies to strengthen vulnerable buildings.

The new results indicate that over 160 million people (or about a third of the total population of South America) live in areas with significantly elevated seismic hazard, primarily within the northern and western portions of the continent where earthquakes associated with subduction and crustal faulting are most common. The risk is not uniform or limited to only coastal areas. Countries such as Venezuela, Colombia, Ecuador, and Peru face high hazard and risk; Chile also faces high hazard, but the vulnerability of buildings is much lower compared with the northern countries due to modern and stringent building codes.
A cornerstone of international collaboration
About a decade ago, scientists in South America from the Centro Regional Seismological para América del Sur requested that USGS scientists collaborate in developing shaking hazard, risk, and design maps for South America. Over the past decade several workshops and discussions with South American colleagues were held to discuss the input data and evaluate the assessments. In June 2016, the USGS and the University of Chile jointly hosted a seismic hazard planning workshop in Costa Rica in which 24 scientists from 17 countries across Latin America participated. This effort was funded by the United States Agency for International Developments Office of U.S. Foreign Disaster Assistance program which is devoted to mitigating risk in this region. The report describing the results was recently published in the journal "Bulletin of the Seismological Society of America."
Start with science
The USGS provides science which is critical for understanding earthquake risk because communities cannot plan for earthquakes if they do not know the expected earthquake occurrence and potential shaking. These USGS models reflect the best and most current understanding of earthquake science and engineering.

Earthquakes are a global concern; in the last decade alone, seismic events have claimed tens of thousands of lives and caused hundreds of billion dollars of economic impact. These international collaborations are an important part in making sure that everyone can benefit from the best available science. For instance, USGS scientists take the scientific expertise and experience they gain working with collaborators in South America and apply it to similar situations here in the United States. In return, scientists in other countries can benefit from the lessons learned by USGS scientists responding to domestic earthquakes.

In the United States, earthquake risk continues to grow with increased exposure of population and development in hazard-prone regions of the country. Understanding earthquake hazards is critical for informed policies, priorities, strategies, and funding decisions to protect the most at-risk communities.

Datasets and models presented in this study and the results are publicly available at https://www.sciencebase.gov/catalog/item/59aeeedee4b0e9bde133ea59.

# data[].attributes.attachment_link.title
USGS issues report on seismic hazard, risk, and design for South America - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.description
South America is one of the most earthquake-prone regions of the world and has witnessed tremendous losses throughout recorded history. A recently released U.S. Geological Survey (USGS) report provides probabilistic tools to help engineers assess seismic hazards, risk, and building code requirements, potentially saving lives and dollars.

# data[].attributes.attachment_link.readable_text
El pasado jueves 15 de marzo de 2018 será tristemente recordado por el impactante colapso -durante la construcción - del puente peatonal de la Florida International University (FIU), en Southwest Eighth Street en Miami, Florida. Hasta el día de hoy, 6 víctimas han sido confirmadas y hay varios heridos. Esta terrible situación tiene que hacernos pensar y aprender.

Cuando ocurre un evento terrible como este, la comunidad técnica tiene la obligación de analizar qué causó el fallo, explicar las conclusiones a la comunidad y proponer acciones destinadas a prevenir cualquier otra catástrofe similar en el futuro. Las lecciones deben ser aprendidas y ampliamente comunicadas para que los ingenieros y los profesionales de la construcción las puedan tener en cuenta a partir de ahora, es nuestro deber con la sociedad y con las víctimas y sus familias. Esto también se debe hacer de manera adecuada, rigurosa, técnica, metódica y sin demora, evitando juicios o evaluaciones precipitadas o prematuras que puedan distorsionar la imagen de los eventos y causar confusión. Qué tarea más difícil de lograr en la sociedad actual del conocimiento "fast food" donde lo inmediato tiene que ser contado, no importa cuán inexactos, vagos o meramente especulativos sean los hechos presentados.

Apenas unos momentos después que ocurriese el doloroso colapso, comenzamos a recibir "información" al respecto, y las personas en las redes sociales comenzaron a reaccionar. Nos quedamos asombrados por la insensatez de algunos de los comentarios que se publicaron, algunos de ellos incluso de supuestos ingenieros y expertos, sin mencionar la campaña casi inmediata de "señalar con el dedo" que comenzó en las redes. En ese ambiente, en Estructurando.net sentimos que era nuestro deber tratar de investigar sobre lo que sabemos a ciencia cierta, tratar de separarlo de las opiniones, las conjeturas y las apuestas y exponerlos a nuestra red, para que podamos tener una idea más clara. Toda la información que hemos recopilado está disponible públicamente en internet, y hay una gran cantidad. No esperéis descubrir las razones por las que sucedió en este post, porque es simplemente imposible llegar a conclusiones definitivas para personas que no están directamente involucradas en el proyecto y desde la distancia. Todo lo que queremos es exponer los hechos y refutar algunos de los comentarios que se han difundido hasta ahora. Citaremos las declaraciones y la información recopilada de las fuentes de los participantes en el Proyecto, e identificaremos nuestros comentarios al respecto utilizando cursivas.

DESCRIPCIÓN DEL PROYECTO.
Objetivo del Promotor (La FIU)
La pasarela es el elemento principal del proyecto "UniversityCity Prosperity Project", promovido por la FIU para dotar a su campus principal de un acceso más seguro para peatones y ciclistas, queriendo crear además con él un nuevo emblema de la Universidad, tal y como se describe en el documento base para la presentación de propuestas de diseño y construcción: "FIU busca a los mejores diseñadores y constructores de Estados Unidos como miembros de un equipo de diseño y construcción para diseñar y construir un innovador puente singular que se convertirá en un hito de diseño respetado y valioso en Miami. Servirá como el elemento fundamental de un corredor de uso compartido orientado a los peatones entre FIU y Sweetwater, lo que promoverá el desarrollo de UniversityCity. Visualizamos un ancho puente peatonal (20 'de ancho mínimo hasta tal vez incluso más de 30') que serviría no solo como un medio para cruzar de un lado a otro, sino que se convertiría en un destino por derecho propio donde los miembros de la comunidad podrían quedarse, reunir y crear un espacio social urbano, un parque lineal. Esperamos que el puente incluso se use como sede de eventos". "Innovación: se debe lograr un equilibrio entre el deseo de un diseño innovador y las realidades de prácticas comprobadas de operación y mantenimiento. Se fomenta el compromiso con la innovación y la excelencia en el diseño, así como con la durabilidad, la facilidad de mantenimiento y la innovación de materiales." [1] (traducción de Estructurando.net).

Nos parece también interesante reflejar un extracto de las condiciones que el promotor estableció para la interferencia con el tráfico rodado durante la construcción:

"J. Secuencia de construcción:

La Firma de Diseño-Construcción debe construir el trabajo de una manera lógica y con los siguientes objetivos como guías:

1. Mantener o mejorar, en la mayor medida posible, la calidad de las operaciones de tráfico existentes, tanto en términos de velocidad de flujo como de seguridad, durante la duración del Proyecto.

2. Minimizar el número de diferentes fases del Plan de control de tráfico (TCP), es decir, el número y tipo de desvíos para un movimiento de tráfico dado ".

"3. Restricciones de control de tráfico:

Los cierres de carriles ocurrirán solo durante las horas valle en las noches sin eventos. Las horas valle son de 9:00 p.m. a 5:30 a.m. de domingo a jueves y de 11:00 p.m. a 7:00 a.m. los viernes y sábados por la noche. Un carril solo se puede cerrar durante períodos de trabajo activos".[2] (traducción de Estructurando.net).
Criterios de Diseño para las propuestas de Diseño y Construcción.
La FIU encarga a la prestigiosa empresa de ingeniería estadounidense TY Lin la redacción de los criterios de diseño que han de fundamentar las propuestas de los licitadores que se presenten al posterior concurso de Diseño y Construcción. En dichos criterios de diseño, ya se dejan claras las preferencias en cuanto a la tipología de la estructura: "Se ha llevado a cabo un estudio exhaustivo que analizó la factibilidad de múltiples tipologías estructurales, incluyendo atirantado, arco, banda tesa, estructura tensigrítica, celosías, vigas cajón típicas y varias otras. Al final, se determinó que una celosía o una solución híbrida entre varios tipos era la mejor tipología para el sitio dado el presupuesto, las limitaciones del sitio y el nivel estético deseado. Uno de los principales parámetros que rigen la selección de una tipología de celosía fue la capacidad de integrar a la perfección la valla de protección de 8 pies requerida sobre la carretera en la estructura y el revestimiento del puente. La valla no debe ser un componente discreto, sino que debe contribuir como una característica que se entrelaza en el diseño holístico y, como tal, funciona proporcionando sombra, seguridad, reforzando la geometría, etc. "[3] (traducción de Estructurando.net).

En dicho documento, se menciona explícitamente la posibilidad de que el adjudicatario plantee estrategias constructivas de las denominadas ABC (Accelerated Bridge Construction): "5.18 Construcción de puente acelerado (ABC). Para los puentes construidos en un área de ensamblaje y lanzados, deslizados o transportados a su ubicación final, proporcione los siguientes artículos al PROPIETARIO, sellados por un ingeniero profesional con licencia para ejercer en el Estado de Florida: ... "(traducción de Estructurando.net).
La Propuesta ganadora del concurso de Diseño y Construcción.
El concurso de diseño y construcción es adjudicado a las firmas MCM (Munilla Construction Management, LLC ) y Figg, como empresa de Ingeniería. Las adjudicatarias entregan una detallada propuesta, de la que extraemos las siguientes figuras[4]:

Propuesta de procedimiento constructivo.
En el documento anteriormente mencionado[5], se recoge una descripción del procedimiento constructivo propuesto:

Traslado del tablero del vano principal con unidades multirrueda (SPMT).

First-of-its-kind pedestrian bridge "swings" into place. "FIU is about building bridges and student safety. This project accomplishes our mission beautifully," -President Mark B. Rosenberg. https://t.co/x8gPM9A4DG #worldsahead pic.twitter.com/mPEMeh2zmw

- FIU (@FIU) March 10, 2018

De acuerdo con el procedimiento constructivo contenido en la propuesta, el contratista procedió a la ejecución del tablero del vano principal en la zona aledaña a la ubicación definitiva, y una vez concluida esta fase, el tablero se izó haciendo uso de equipamiento de heavy-lifting tipo multirrueda (o SPMT, Self-Propelled Modular Transportation), se giró 90º y se apoyó en las pilas definitivas. La operación se realizó en horario nocturno y en fin de semana, de acuerdo con las prescripciones de afección al tráfico del promotor.

De acuerdo con el díptico informativo de la FIU[6], "Se trata del mayor desplazamiento de un puente peatonal usando SPMTs en la historia de los Estados Unidos" "La longitud del tramo desplazado es de 174 pies (53 m) y su peso, de 950 toneladas" (traducción de Estructurando.net).

DETECCIÓN DE FISURACIÓN EN EL HORMIGÓN.

Según información publicada por el Departamento de Transporte de Florida (FDOT)[7], el martes 13 de marzo uno de los ingenieros de Figg llamó a los representantes de FDOT para el proyecto dejando un mensaje de voz que describía "algunas fisuras que se observaron en el extremo norte del tramo, el extremo del pilón de ese tramo que se trasladó este fin de semana" el mensaje continuó "obviamente se requerirán algunas reparaciones o lo que sea necesario hacer, pero desde una perspectiva de seguridad no vemos que haya ningún problema, así que no estamos preocupados desde esa perspectiva, aunque obviamente la fisuración no es buena y algo se tiene que hacer para repararla". (traducción de Estructurando.net).

EL COLAPSO.

La sucesión de acontecimientos puede ser resumida como sigue:

* El jueves 15 de febrero de 2018 (aproximadamente a las 12:50 h hora de la Costa Este), se estaban llevando a cabo algunos trabajos en el tablero del vano principal. Algunos carriles de tráfico de la calle SW 8 estaban cerrados (los más cercanos a Pila 2 - el pilono). Los trabajadores de la empresa Structural Technologies (diseñadora y fabricante de los sistemas VSL de postensado y construcción en los Estados Unidos) estaban participando en los trabajos llevados a cabo.

* Al menos 5 carriles de tráfico estaban ocupados en ese momento por vehículos detenidos debajo del área de construcción, a causa de un semáforo en rojo.

* De repente, el tablero de hormigón se derrumba y cae al suelo, atrapando varios vehículos debajo y arrastrando a algunos de los trabajadores. Las primeras secciones afectadas por el colapso son los dos nudos de la celosía más cercanos a Pila 2 (el futuro pilono). Como se puede observar en las imágenes que a continuación se acompañan, a simple vista se detectan fácilmente 2 quiebros en la geometría de los cordones superior e inferior de la celosía en el mismo momento del colapso, en los nudos de unión de las diagonales más cercanas al pilono. Los nudos extremos del cordón superior e inferior de la celosía, que se ubican justo en la vertical del apoyo sobre Pila 2, también colapsan. Se da la circunstancia de que el montante (elemento vertical) que une esos 2 nudos no estaba aún hormigonado a sección completa, dado que se pretendía unir monolíticamente con la celosía del vano de compensación y con el pilono, tal y como se concibió el proceso constructivo.

* Marco Rubio, gobernador de la Florida, tuiteó después del colapso de que "los cables que suspendían el puente #Miami se habían aflojado y la empresa de ingeniería ordenó que se apretaran. Estaban siendo apretados cuando colapsó hoy." Más tarde, agregó "Más detalles sobre mi tweet de anoche. Los equipos de construcción estaban trabajando en el extremo norte del puente aplicando una "fuerza de post-tensado" cuando ocurrió #MiamiBridgeCollapse. La investigación de seguridad de @NTSB ya está en marcha". Finalmente, publicó "Nuevo video publicado de @FIU #miamibridgecollapse desde la vista del tablero de un conductor que fue testigo de ello. En el momento del colapso, los equipos de construcción estaban trabajando en una diagonal en el extremo norte del puente aplicando fuerza de post-tensión para fortalecerlo". (traducción de Estructurando.net).

More details about my tweet last night. Construction crews were working at north end of bridge applying a "posttensioning force" when #MiamiBridgeCollapse occurred. The @NTSB safety investigation is now fully underway

- Marco Rubio (@marcorubio) March 17, 2018

Algunas imágenes tomadas tras el colapso muestran en efecto un gato de postesado aplicado a una barra en uno de los elementos de la celosía:

Algunas consideraciones (personales y subjetivas) sobre lo ocurrido.
* Figg, la Compañía de Ingeniería de Diseño para el Proyecto, ha diseñado numerosos puentes singulares en los EE. UU., Como el Puente Leonard P. Zakim en Boston, MA. http://www.figgbridge.com/portfolio.html. Están involucrados en varios proyectos importantes en curso, como el New Harbour Bridge en Corpus Christi, TX, construido por Dragados USA y Flatiron. * Se han formulado preguntas sobre el sistema de atirantamiento del tablero (no presente en el momento del colapso). Al analizar la propuesta del Design-Builder, está claro que se siguieron las fases de construcción propuestas, y que el tramo principal se diseñó para ser transportado utilizando SPMT y luego se izó sin el sistema de atirantado. La propuesta de D & B también deja en claro que "el tamaño de los tirantes y su separación se diseñaron para proporcionar rigidez adicional. La estructura cumple con los criterios de diseño de resistencia sin los tirantes; son una característica estructural adicional provista para cumplir con los requisitos de frecuencia de vibración"[8] (traducción de Estructurando.net). De hecho, los tirantes se diseñaron como tubos de acero huecos, en lugar de usar los haces de cordones o las barras de acero activo usuales, como se puede ver en el siguiente detalle:
* Con respecto a la tipología del puente, está claro que los Criterios de diseño designaron la celosía como la opción preferible. El material que se habría de utilizar no estaba sin embargo claramente definido, pero se mencionan las soluciones de secciones compuestas de acero y hormigón. "La superestructura del puente debe ser principalmente de acero estructural con superficie del tablero de hormigón"[9]. Sin embargo, la selección de la solución de hormigón postesado está ampliamente justificada por el D & B en su propuesta. Es una solución más pesada (el tramo principal de 174 pies - 53 m - de largo pesaba 950 toneladas, que es un peso propio significativo para un puente peatonal), pero tiene algunas ventajas tales como las propiedades antivibratorias mejoradas o el aislamiento del ruido.
* Algunos comentarios también se han planteado con respecto a los materiales utilizados para el proyecto y su origen. La única información que tenemos es que el Proyecto estaba bajo las regulaciones Buy-America, "Los materiales deben cumplir con la" Buy America Act ", 49 U.S. code Section 5323", y por lo tanto, todos los materiales deben haber sido producidos y fabricados dentro de los Estados Unidos. * Obviamente, se debe investigar la aparición de fisuras en el área cercana al pilono, pero la fisuración es un fenómeno consustancial al hormigón, debido a sus propiedades reológicas y mecánicas, y puede permitirse, sujeto a ciertas restricciones. La información disponible no ofrece detalles sobre el alcance, las dimensiones y la ubicación de la fisuración y, por lo tanto, no se puede extraer ninguna conclusión. * Los tweets de Marco Rubio aparentemente apuntan a la post-tensión de una diagonal. De acuerdo con los Dibujos Preliminares de Diseño, los miembros de la celosía tienen el siguiente sistema de postesado: En las estructuras de hormigón postesado, los ajustes de tensión de los tendones son habituales. En este caso, además, el sistema de apoyos de la celosía del vano principal cambia durante el izado: los soportes temporales del SPMT se ubicaron debajo de los nudos interiores inferiores de la celosía, y cuando se erigió, la celosía se dejó apoyada en los nudos extremos, sobre las pilas permanentes. Tal cambio en las condiciones de soporte tiene impacto en las fuerzas soportadas por las diagonales extremas, y en ellas incluso la fuerza axial externa puede haber cambiado de la tracción (cuando es soportada por el SPMT) a la compresión (cuando es soportada por los pilares permanentes). Las fuerzas externas deben ser soportadas por el hormigón y su sistema de postensado, por lo que un ajuste en este último no resulta extraño en primera aproximación. * Con todo lo dicho, y asumiendo que las afirmaciones de Marco Rubio son ciertas, debemos plantear preguntas básicas: si se está actuando de algún modo sobre un elemento crítico en la estabilidad de la estructura (como la diagonal de una celosía plana simplemente apoyada en sus extremos, que es una estructura isostática), ¿por qué no se corta el tráfico debajo de la estructura? ¿Por qué los apoyos provisionales del tablero se eliminaron completamente si se habían de realizar ajustes en algunos de los elementos estructurales críticos? Confiemos en conocer algún día las respuestas.
[1] Florida International University. DESIGN-BUILD MAXIMUM PRICE REQUEST FOR PROPOSAL For UniversityCity Prosperity Project Miami-Dade County, Florida. June 2014. Published on https://facilities.fiu.edu/projects/BT-904.htm
[2] Florida International University. DESIGN-BUILD MAXIMUM PRICE REQUEST FOR PROPOSAL For UniversityCity Prosperity Project Miami-Dade County, Florida. June 2014. Published on https://facilities.fiu.edu/projects/BT-904.htm
[3] TY Lin International FIU-UniversityCity Prosperity Project - Pedestrian Bridge Design Criteria. April 2015. Published on https://facilities.fiu.edu/projects/BT-904.htm
[4] MCM+FIGG Design Build Team. Proposal for the BT-904. FIU UniversityCity Prosperity Project. September 2015. Published on https://facilities.fiu.edu/projects/BT-904.htm
[5] MCM+FIGG Design Build Team. Proposal for the BT-904. FIU UniversityCity Prosperity Project. September 2015. Published on https://facilities.fiu.edu/projects/BT-904.htm
[6] FIU. https://news.fiu.edu/wp-content/uploads/17703_EXT_FIU_Bridge_Move_Fact_Sheet_030918_DIGITAL.pdf
[7] http://www.miamiherald.com/news/local/community/miami-dade/article205627294.html
[8] MCM+FIGG Design Build Team. Proposal for the BT-904. FIU UniversityCity Prosperity Project. September 2015. Published on https://facilities.fiu.edu/projects/BT-904.htm
[9] TY Lin International FIU-UniversityCity Prosperity Project - Pedestrian Bridge Design Criteria. April 2015. Published on https://facilities.fiu.edu/projects/BT-904.htm
¿Quieres ser el primero en leer nuestros artículos?
Déjanos tu nombre y un email válido, y nosotros te avisaremos cuando hayan novedades en Estructurando

The following two tabs change content below.

# data[].attributes.attachment_link.title
Colapso de la pasarela de la Universidad de Florida - Estructurando

# data[].attributes.attachment_link.description
El pasado jueves 15 de marzo de 2018 será tristemente recordado por el impactante colapso -durante la construcción - del puente peatonal de la Florida International University (FIU), en Southwest Eighth Street en Miami, Florida. Hasta el día de hoy, 6 víctimas han sido confirmadas y hay varios heridos.

# data[].attributes.headline
Construnario - Estructurando: Smart Seismic Concrete Connection: un elemento que permite a los edificios recuperar su forma tras un terremoto

# data[].attributes.subject
Construnario - Estructurando: Smart Seismic Concrete Connection: un elemento que permite a los edificios recuperar su forma tras un terremoto

# data[].attributes.attachment_link.readable_text
Los investigadores del Instituto de Ciencia y Tecnología del Hormigón (ICITECH) de la Universitat Politècnica de València (UPV) José Luis Bonet Senach, Javier Pereiro Barceló y Alberto Navarro Gómez hemos desarrollado un nuevo elemento constructivo, el Smart Seismic Concrete Connection, que permite a los edificios recuperar su forma original tras sufrir un terremoto.

En este post os contamos en qué consiste, y compartiremos con vosotros algunos resultados experimentales, fotos y vídeos de los elementos ensayados en laboratorio.

El problema

A diferencia de lo que hacemos frente a otras acciones, cuando diseñamos estructuras frente a terremotos normalmente no las dimensionamos para que resistan el valor total de las fuerzas que podrían llegar a causar. Calcular las estructuras para que resistieran en régimen lineal frente a un eventual seísmo sería antieconómico. Por ello, las normativas sismorresistentes actuales nos permiten reducir el valor de esas fuerzas teóricas a través de dotar a los miembros de ductilidad, es decir, capacidad de deformarse sin producir mecanismos de fallo frágiles. Aprovechar esta ductilidad permite a las estructuras absorber grandes cantidades de energía y evitar el riesgo de colapso en los terremotos más severos.

Sin embargo, esto no sale gratis. En construcciones de hormigón, esta disipación de energía se logra a través de plastificaciones en las armaduras de acero, fisuras y roturas en el hormigón, salto del recubrimiento, etc. Esto significa que en las normas sismorresistentes actuales existe un trade-off entre seguridad y daños: evitamos que las estructuras colapsen, pero asumimos un cierto de nivel de deformaciones residuales sobre las mismas que obligarán a reparaciones o demoliciones posteriores. Entonces nos preguntamos: ¿es posible conseguir un material capaz de "plastificar" para absorber los movimientos del terremoto pero que a su vez tenga bajas deformaciones residuales?

La solución

El dispositivo de conexión Smart Seismic Concrete Connection (SSCC) está compuesto por dos materiales que actúan simbióticamente frente a un terremoto. En primer lugar, unas barras de aleaciones con memoria de forma (SMA) que pueden desarrollar la llamada superelasticidad, que es la capacidad de estos metales de recuperar su forma tras estirarse o doblarse, algo que no pueden hacer las armaduras de acero de las estructuras de hormigón. En la siguiente figura se aporta un ejemplo de carga cíclica de barras de acero y de SMA para ilustrar la gran diferencia de comportamiento entre en cuanto a deformaciones residuales.

Otras propiedades que hacen conveniente el uso de SMA en construcciones en zona sísmica son:

Capacidad de disipación de energía: el SMA tiene una capacidad de disipación de energía similar a la del acero, originada a lo largo de los ciclos histeréticos que se producen en las barras durante el terremoto.

Capacidad de amortiguamiento de impactos: en caso de cargas de impacto como son los movimientos bruscos que impone un terremoto, los SMA responden con una gran inercia, ya que absorben una parte de la energía de impacto en forma de calor. Esto contribuye a disminuir las aceleraciones de planta, y por tanto los daños sobre equipos, mobiliario, etc.

Rigidez de emergencia: en caso de grandes deformaciones, las barras de SMA, tras aparentemente plastificar, aumentan de nuevo su rigidez, limitando de nuevo las deformaciones.

Corrosión: al contrario que las armaduras de acero, estas barras de SMA no sufren corrosión.

A estas alturas os estaréis preguntando por qué no hemos oído hablar más del SMA en construcción sismorresistente. Pues bien, además de por ser un material de caracterización mecánica compleja, no ha sido hasta tiempo reciente que se han podido producir barras de SMA de los diámetros habituales en construcción a un coste competitivo. Esto ha sido gracias a la cada vez mayor atención que recibe desde diversos sectores, incluido el de la construcción.

El segundo elemento clave para la solución es un hormigón de muy altas prestaciones, conocido como VHPC. Las altas deformaciones que sufren las barras de SMA serían imposibles de conseguir si el hormigón que lo envuelve no fuera capaz de acompañarle, cosa que el hormigón convencional no puede hacer. Sin embargo, el VHPC sí es capaz ya que se trata de un hormigón muy dúctil que además resiste cuatro veces más que el hormigón convencional.

El hecho de que se hable de un hormigón de "muy altas prestaciones" y no simplemente de un hormigón de "muy alta resistencia" proviene de su comportamiento totalmente diferente al hormigón convencional, tanto en tracción como en compresión. En la parte de compresión, en el VHPC no se produce una caída brusca de la resistencia a compresión como sería el caso de un hormigón normal. En la parte de tracción, aparte de mostrar una mayor resistencia a tracción, una vez alcanzada ésta no se produce la formación de una única fisura como en el hormigón convencional. Por el contrario, se genera un fenómeno de microfisuración distribuida que tiene como resultado un efecto strain-hardening en el que la resistencia a tracción aumenta paulatinamente antes de que se genere la localización de la fisuración. Todo ello significa una reducción de los daños ya no se concentran tanto como en el hormigón normal, ni en el tiempo ni en el espacio.

Posicionamiento del elemento

Una de las novedades principales del Smart Seismic Concrete Connection es que, a diferencia de otros sistemas antisísmicos -como los aislamientos de base o los amortiguadores de masa -, no implica la adición de elementos adicionales a la estructura que supongan necesidades de espacio, inspección o mantenimiento. El elemento se integra perfectamente en la estructura, simplemente sustituyendo el hormigón y armaduras convencionales por VHPC y barras de SMA en las zonas más susceptibles de producirse daños. En el caso de puentes en las zonas de unión pila-cimentación y pila-tablero, y en edificación en soportes de planta baja y en las uniones viga-soporte.

Los resultados

Hemos realizado en el ICITECH ensayos experimentales sobre elementos unión viga-soporte y soporte-cimentación para evaluar la efectividad del Smart Seismic Concrete Connection en la mitigación de daños frente a cargas cíclicas. Los resultados experimentales han arrojado una reducción de las derivas residuales de hasta un 86% respecto al elemento construido con materiales convencionales, además de aumentos de la carga y deriva máximas de un 250% y 66% respectivamente.

Asimismo, los elementos modificados mediante Smart Seismic Concrete Connection también mostraron menores niveles de daño en la zona de rótula plástica, fácilmente reparables.

Tras el estudio a nivel elemento, el siguiente hito ha sido pasar a nivel estructura. Mediante simulaciones numéricas en régimen no-lineal de edificios sometidos a un conjunto de terremotos históricos, se ha comprobado la capacidad de los diseños modificados con el Smart Seismic Concrete Connection de reducir las derivas máximas residuales entre plantas en un 90%. Además se incrementa el periodo fundamental de la estructura, reduciendo las acciones sísmicas que nos proporciona el espectro de respuesta en la mayor parte de los casos, y se incrementa el valor del factor de comportamiento, lo que supondría reducir aún más los esfuerzos de diseño.

En conclusión, esta reducción de los daños supondrá un ahorro de costes muy significativo a lo largo del ciclo de vida para estructuras construidas en zonas sísmicas, gracias a la reducción de las pérdidas económicas y al mantenimiento de su nivel de operación normal en caso de terremoto.

VÍDEOS DE LOS ENSAYOS:

Ensayo de Unión Soporte Cimentación Tipo Cáliz ICITECH UPV:

Unión Soporte Cimentación Tipo Vainas ICITECH UPV:

Unión Soporte Viga ICITECH UPV:

¿Quieres ser el primero en leer nuestros artículos?
Déjanos tu nombre y un email válido, y nosotros te avisaremos cuando hayan novedades en Estructurando

The following two tabs change content below.

# data[].attributes.attachment_link.title
Smart Seismic Concrete Connection: un elemento que permite a los edificios recuperar su forma tras un terremoto - Estructurando

# data[].attributes.attachment_link.description
Los investigadores del Instituto de Ciencia y Tecnología del Hormigón (ICITECH) de la Universitat Politècnica de València (UPV) José Luis Bonet Senach, Javier Pereiro Barceló y Alberto Navarro Gómez hemos desarrollado un nuevo elemento constructivo, el Smart Seismic Concrete Connection, que permite a los edificios recuperar su forma original tras sufrir un terremoto.

# data[].attributes.headline
El rascacielos de madera más alto del mundo será ecológico y llegará el 2041 | N+1: artículos científicos, noticias de ciencia, cosmos, gadgets, tecnología

# data[].attributes.subject
El rascacielos de madera más alto del mundo será ecológico y llegará el 2041 | N+1: artículos científicos, noticias de ciencia, cosmos, gadgets, tecnología

# data[].attributes.attachment_link.keywords[]
revistas de revista de ciencia y tecnología

# data[].attributes.attachment_link.title
El rascacielos de madera más alto del mundo será ecológico y llegará el 2041

# data[].attributes.attachment_link.description
Ciencia y tecnología que suman | NMAS1.ORG

# data[].attributes.headline
Mass timber milestone - Civil + Structural Engineer magazine

# data[].attributes.subject
Mass timber milestone - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.readable_text
Oregon rightfully earned its place as one of the greenest regions in the world years ago. A leader in architectural innovation and sustainability, Portland has the second highest number of LEED-accredited buildings in the United States and is recognized for its mix of groundbreaking and influential modern design and sustainable, eco-friendly architecture.

Perhaps most of all, Portland and its neighboring cities are known more recently for their use of mass timber as an alternative to steel and concrete. Known for its lighter environmental footprint and as an environmentally responsible building material, mass timber sequesters carbon dioxide from the atmosphere by storing carbon in the structure during the entire life of the building. It also promotes sustainable forest management practices.

The headquarters of the non-profit First Tech Federal Credit Union in Hillsboro is the latest groundbreaking project to join Oregon's architecturally renowned landscape. Weeks ago, the final cross-laminated timber (CLT) panel was placed, completing the building's structure and marking a significant milestone in mass timber architecture. At 156,000 square feet, the First Tech headquarters will be the largest CLT structure in the country, adding to a growing list of commercial buildings in Oregon to join the mass timber movement of recent years.

The decision to build such a large structure out of timber was born out of First Tech's "people first" ethic. When doors open this summer, the building will support and promote the health, happiness, and comfort of the employees located there.
The research
Swinerton Builders were brought onto the First Tech project by Portland-based architect, HACKER, who saw mass timber as a crucial part of the overall development strategy for the First Tech project. Emphasizing energy efficiency, indoor air quality, equal access to natural light, and the value of connecting people with nature, HACKER recognized the benefits of the building material from the beginning.

However, HACKER needed to optimize ways to integrate mass timber as the structural solution for this particular structure. To better understand how to leverage the value and strength of mass timber in this project, Swinerton committed to researching alternative structural scenarios that compared structural steel and nail-laminated timber (NLT) to CLT. Swinerton and HACKER were able to recommend CLT to the client for this project by unlocking several strengths of the CLT panels.

Running in both directions, Structurlam's CrossLam CLT panels simplified the edge details of the building, were incorporated as the structural diaphragm of the building for earthquake stability, and provided a lighter overall structural system, obviating the need for costly ground improvements or deep foundations. Because of the precision with which the CLT panels can be fabricated, virtual design and construction could be leveraged to produce more than 4,500 mechanical/electrical/plumbing (MEP) penetrations in the factory, reducing field time for follow-on trades.

After an in-depth research period, Swinerton's core team took a trip to Canada, where more CLT projects had been completed. Their purpose was to gain a better understanding of constructability aspects and considerations for CLT and its installation. Swinerton focused its visit to Kelowna, Penticton, and Okanagan Falls on not only Structurlam's facilities and detailing group, but also by visiting construction sites and meeting with general contractors familiar with CLT installation.
The design
Following the research period, the Swinerton team partnered with Structurlam Products to harness the benefits of a glulam and CLT structure through a holistic approach to design and construction. Structurlam provided the design of concealed glulam connections and CLT horizontal diaphragms, as well as a fully fabricated mass timber package for the First Tech project.

With the First Tech project, Swinerton Builders identified and capitalized on the ripple effects of optimizing the building's structure. Swinerton employed CrossLam CLT not only as a structural solution, but also as a path toward simplifying other building systems, such as the foundation and envelope. Through pre-planning and coordination, Structurlam implemented a shift toward a more "systems-oriented" construction process.

Swinerton managed and coordinated project partners through a fully integrated, virtual design and construction BIM model, which included the timber structure, the steel lateral systems, and the MEP services. At the Structurlam facility, glulam and CrossLam CLT were prefabricated for First Tech by CNC machines based on a fabrication-level 3D model. Like Lincoln Logs or Legos, the materials are pre-constructed to an exact fit, giving way for smarter utilization during the construction period.
The installation
Upon completion of the design, 3D modeling, and shop drawings, the first glulam columns were delivered and installed on July 27. In total, 626+ CrossLam panels and 988+ glulam columns and beams were delivered in 64 truckloads. On Nov. 16, the final CrossLam panel was installed, completing the timber and steel frame of a 156,000-square-foot structure in 15 weeks. How did we manage to construct such a large structure in just 15 weeks? Through self-performing the construction process and using optimizable materials.

CrossLam CLT is manufactured to span in two directions, with strength in both major and minor axis directions. By optimizing the frame to be as efficient and light as possible, this allows us to cut down on heavier transport and installation time and costs. Detailed preconstruction planning also helped to ensure that the installation of CrossLam CLT was easy and efficient, simplifying the foundation system and making ground improvements in the foundation unnecessary.

A milestone project, First Tech Federal Credit Union is a shining example of the possibilities of building with mass timber and the associated benefits. In a time when eco-friendly buildings are not a luxury but a necessity, mass timber structures have drawn the world's attention for their strength, light environmental footprint, and cutting-edge prefabrication technology.

Erica Spiritos, is a mass timber specialist with Structurlam( www.structurlam.com ), and William P. Silva is preconstruction manager with Swinerton ( www.swinerton.com ).

# data[].attributes.attachment_link.title
Mass timber milestone - Civil + Structural Engineer magazine

# data[].attributes.attachment_link.description
Oregon rightfully earned its place as one of the greenest regions in the world years ago. A leader in architectural innovation and sustainability, Portland has the second highest number of LEED-accredited buildings in the United States and is recognized for its mix of groundbreaking and influential modern design and sustainable, eco-friendly architecture.

# data[].attributes.attachment_link.readable_text
Uno se cree que un tema está más que trillado, como puede ser el coeficiente de balasto, cuando todavía me sorprende encontrar proyectos donde está mal aplicado o simplemente no se molestan en hacerlo correctamente.

Con el fin de dejar mi granito de arena para que el uso de este concepto esté mejor aplicado en los proyectos, dejo el post de hoy: un pequeño compendio sobre lo que es el Coeficiente de balasto, cómo se deduce de los ensayos el valor del K30 y cómo manejar ese valor para utilizarlo en nuestros cálculos estructurales. Además, recopilo varias formulaciones que creo que os pueden ser interesantes para los que el tema ya lo domináis.

El coeficiente de balasto Ks es un parámetro que se define como la relación entre la presión que actúa en un punto, p, y el asiento que se produce, y, es decir Ks=p/y. Este parámetro tiene dimensión de peso específico y, aunque depende de las propiedades del terreno (esto no se le escapa a nadie) no es una constante del mismo ya que también depende de las dimensiones del área que carga contra el terreno (esto es lo no toda la gente no tiene tan claro).

Veamos cómo podemos estimar el valor del coeficiente de balasto. Existen dos maneras para poder realizar dicha estimación:

1. Mediante el Ensayo de Placa de Carga

En España, el ensayo de placa de carga se rige según la normativa del Laboratorio de Transportes NLT-357/98 (viales) o la UNE 7391:1975 (cimentaciones). En la foto anterior podemos ver una placa circular que carga al terreno. De la placa salen unos comparadores que nos permiten medir el asiento que sufre el terreno al cargar la placa.

El cociente de la carga entre el asiento nos proporciona el coeficiente de balasto asociado a las dimensiones de la placa. Existen varios tipos de placas, las cuadradas de 30×30 cm o las circulares de 30, 60 o 76,2 cm de diámetro. Por tanto, el coeficiente viene generalmente respresentado por una K y el correspondiente subíndice que identifica a la placa con la que se realizó el ensayo.

Lo usual es que los laboratorios proporcionen el coeficiente de balasto de la placa cuadrada de 30 cm de lado, el K30. Existen muchos autores que han proporcionado varios valores del K30 para diferentes clases de suelos. Os dejo algunas de las tablas más interesantes que conviene tener:

Pero claro, una cosa es tener el coeficiente de balasto de una placa cuadrada de 30 cm de lado y otra muy distinta es tenerla para el tamaño real cimentación. Aunque sea el mismo terreno, el valor debe ser corregido por las dimensiones de nuestra cimentación. Para ello, fue Terzaghi (1955) quien propuso las siguientes formulaciones:

Para una zapata cuadrada de lado B(m) el coeficiente de balasto valdrá:

Para suelos cohesivos:

Para suelos arenosos

Para suelos de transición (entre arenas y arcillas)
%cohesivo es el porcentaje del suelo que se puede suponer cohesivo y %arenoso el porcentaje que se supone arenoso. (%cohesivo+%arenoso=100)

Si lo que tenemos es una losa rectangular de lados B(m) y L(m) (L>B):

2. En función de otras características del terreno.
Estamos hablando de correlaciones del coeficiente de balasto con otros parámetros del terreno como pueden ser:

En función del módulo de deformación:

Fórmula de Vogt:

Fórmula de Vesic:

Fórmula de Klepikov:
Siendo A el área de la cimentación y ω un coeficiente de forma que viene dado por:

Fórmula de la Universidad de Buenos Aires:

En función de la tensión admisible de la cimentación:

Siendo FS el factor de seguridad empleado para minorar la tensión admisible (entre 2 y 3)

Se puede usar la siguiente gráfica que relaciona el índice portante de California (CBR) con el coeficiente de balasto de una placa de 30'' de diámetro.

En función de la resistencia a compresión simple qu (suelos cohesivos):

En función del ensayo SPT:

En suelos cohesivos:

En arenas secas:

Y por tanto para una cimentación de BxL:

En arenas sumergidas Y por tanto para una cimentación de BxL:

Todo lo anterior queda dicho para el coeficiente de balasto vertical, es decir, el utilizable a zapatas y losas. Para el caso de pantallas o pilotes se debe considerar el coeficiente de balasto horizontal. Para ello ya hicimos un post hablando de una forma de estimarlo: " La verdadera historia del Ábaco de Chadeisson ". Pronto haremos otro post recopilando varias formulaciones para su estimación.

Espero que os resulte útil.
¿Quieres ser el primero en leer nuestros artículos?
Déjanos tu nombre y un email válido, y nosotros te avisaremos cuando hayan novedades en Estructurando

The following two tabs change content below.

# data[].attributes.attachment_link.title
Breve resumen del Coeficiente de Balasto - Estructurando

# data[].attributes.attachment_link.description
Uno se cree que un tema está más que trillado, como puede ser el coeficiente de balasto, cuando todavía me sorprende encontrar proyectos donde está mal aplicado o simplemente no se molestan en hacerlo correctamente.

# data[].attributes.headline
El rascacielos de madera más alto del mundo será ecológico y llegará el 2041 | N+1: artículos científicos, noticias de ciencia, cosmos, gadgets, tecnología

# data[].attributes.subject
El rascacielos de madera más alto del mundo será ecológico y llegará el 2041 | N+1: artículos científicos, noticias de ciencia, cosmos, gadgets, tecnología

# data[].attributes.attachment_link.keywords[]
revistas de revista de ciencia y tecnología

# data[].attributes.attachment_link.title
El rascacielos de madera más alto del mundo será ecológico y llegará el 2041

# data[].attributes.attachment_link.description
Ciencia y tecnología que suman | NMAS1.ORG

# data[].attributes.wish_content.attachment_props.text
Explicación de como funcionan los aisladores sísmicos en una edificación.

# data[].attributes.wish_content.attachment_props.original_text
Explicación de como funcionan los aisladores sísmicos en una edificación. https://t.co/ebXaX7a7Tf

# data[].attributes.attachment_link.embed_code
Explicación de como funcionan los aisladores sísmicos en una edificación. pic.twitter.com/ebXaX7a7Tf
— Mundo del Hormigón (@Mundo_Hormigon) February 21, 2018

# data[].attributes.attachment_link.metadata.attachment_props_source.data.text
Explicación de como funcionan los aisladores sísmicos en una edificación. https://t.co/ebXaX7a7Tf

# data[].attributes.attachment_link.metadata.attachment_props.original_text
Explicación de como funcionan los aisladores sísmicos en una edificación. https://t.co/ebXaX7a7Tf

# data[].attributes.attachment_link.metadata.attachment_props.text
Explicación de como funcionan los aisladores sísmicos en una edificación.

# data[].attributes.attachment_link.readable_text
Santiago Huerta Fernández en su artículo " MECÁNICA DE LAS BÓVEDAS DE LA CATEDRAL DE GERONA " nos cuenta, de manera ejemplar, lo sucedido en la catedral de Girona como introducción a la mecánica de las catedrales.

Nos cuenta cómo en 1370 se empezó la construcción de una gran nave única que llegaría ser la Catedral de Girona. Sin embargo, esta gran empresa, pues no había precedentes por aquel entonces de ninguna nave que salvara una luz tan grande, originó una gran polémica sobre la viabilidad de la obra.

En 1416, con la obra ya arrancada, el Cabildo de la Catedral convoca una comisión de expertos, un Congreso de Arquitectos, para zanjar la polémica y decidir si seguir con la construcción de la nave o no.

El resultado del Congreso fue claro: los 12 arquitectos consultados afirmaron unánimemente que la obra sería segura y que los estribos ya empezados serían suficientes.

Por tanto, se adoptó la solución de la gran nave, completándose los dos primeros tramos en el siglo XV y los dos últimos en el siglo XVI. Y la gran obra, ahí sigue (la catedral gótica con la nave mas ancha del mundo):

Santiago, en su artículo, se hace las siguientes preguntas: " ¿Cómo es posible que tuvieran esa seguridad a falta de un ejemplo de dimensiones similares? ¿Qué sustrato común de conocimiento les permitía emitir un juicio tan categórico? En definitiva, ¿cómo calculaban los arquitectos góticos sus estructuras?"

Los constructores del gótico disponían de reglas basadas en su experiencia e intuición que nos han llegado en algunos tratados de arquitectura. Una de esas reglas, unas de las más difundidas, es la " Regla de Blondel " llamada así porque está recogida en el tratado de arquitectura de Blondel de 1698 aunque se sabe que dicha regla es mucho más antigua.

Dicha regla proporciona las dimensiones de los estribos en función del arco. Su construcción geométrica consiste en dividir el arco (ya sea un arco de medio punto, apuntado...etc.) en tres partes iguales obteniendo los puntos C y D. Luego se traza una recta que una uno de estos puntos con su arranque más cercano. Finalmente, sobre esta recta, se lleva la distancia DB=AC desde el punto de arranque obteniéndose el espesor del estribo necesario. Esta regla da estribos mayores para arcos rebajados y menores para arcos apuntados.

Desarrollando la regla para un arco semielíptico de semiejes a y b (luz del arco L=2*a y flecha del arco f=b) llegamos a estribos de espesores L/(3+β²) siendo β=b/a. Así, para un arco de medio punto β=1, el estribo tendrá un ancho de L/4. Si el arco se peralta, el estribo se estrecha y si se rebaja, el estribo se ensancha hasta un límite de L/3.

Si utilizamos dicha regla en la Catedral de Girona:

Vemos que la regla se cumple, aunque este hecho no ratifica la utilización de dicha regla para el cálculo de esta nave. Podemos afirmar, sin embargo, que los arquitectos del Congreso, disponían de esta regla o similares para llegar a su unánime conclusión.

Recomiendo francamente la lectura del artículo de Santiago Huerta de donde he sacado esta información y donde podéis ver un análisis científico de estabilidad de obras de fábrica. De verdad que no tiene desperdicio.

Y si os sigue interesando el tema, os dejo otro link del libro " Arcos, bóvedas y cúpulas. Geometría y equilibrio en el cálculo tradicional de estructuras de fábrica " también de Santiago Huerta donde se pueden ver otras reglas a aplicar, no solo en catedrales si no también en puentes.
¿Quieres ser el primero en leer nuestros artículos?
Déjanos tu nombre y un email válido, y nosotros te avisaremos cuando hayan novedades en Estructurando

The following two tabs change content below.

# data[].attributes.attachment_link.title
La Regla de Blondel o por qué las catedrales góticas no se caen - Estructurando

# data[].attributes.attachment_link.description
Santiago Huerta Fernández en su artículo " MECÁNICA DE LAS BÓVEDAS DE LA CATEDRAL DE GERONA " nos cuenta, de manera ejemplar, lo sucedido en la catedral de Girona como introducción a la mecánica de las catedrales. Nos cuenta cómo en 1370 se empezó la construcción de una gran nave única que llegaría ser la Catedral de Girona.

# data[].attributes.attachment_link.readable_text
Feb 7, 2018 11:25 am
Publicado en: Actualidad, Internacionales

Socorristas en Taiwán removían el miércoles los escombros de edificios derrumbados en busca de unas 60 personas desaparecidas, después de un fuerte sismo que dejó al menos cinco muertos durante la madrugada cerca de la ciudad turística de Hualien.

El temblor de magnitud 6,4, que se produjo a poca distancia de la ciudad costera justo antes de la medianoche (1600 GMT) del martes, también dejó heridas a 243 personas y provocó el colapso de cuatro edificios, dijeron funcionarios.

Otros cinco edificios, entre ellos un hospital, se vieron afectados por el sismo, que dejó carreteras llenas de escombros y grietas y cerca de 2.000 casas sin electricidad.

De acuerdo con un balance oficial, 214 personas resultaron heridas, 117 fueron rescatadas entre los edificios dañados y unas 830 personas estaban protegidas en refugios.

La agencia nacional de bomberos indicó que en la ciudad habían muerto seis personas.

Muchos habitantes no querían regresar a sus hogares por temor a las réplicas. Según las autoridades.

Un vecino de la ciudad, Blue Hsu, vio derrumbarse los pisos inferiores del hotel Marshal. "Se hundieron en el suelo y vi cómo rescataban a turistas aterrados", dijo.

# data[].attributes.attachment_link.description
Feb 7, 2018 11:25 am Publicado en: Actualidad, Internacionales Socorristas en Taiwán removían el miércoles los escombros de edificios derrumbados en busca de unas 60 personas desaparecidas, después de un fuerte sismo que dejó al menos cinco muertos durante la madrugada cerca de la ciudad turística de Hualien.

# data[].attributes.headline
2017 Wood Design & Building Award Winners Announced | ArchDaily

# data[].attributes.subject
2017 Wood Design & Building Award Winners Announced | ArchDaily

# data[].attributes.attachment_link.readable_text
Jurors looked for submissions which were not only aesthetic but also pushed the perceived limitations of wood construction.

The Wood Design & Building Awards program has been in existence for over 30 years, said the Vice-President of Market Development for the Canadian Wood Council, Etienne Lalonde. We've been continually impressed with the quality of submissions each year, and it's a testament to the sophistication of wood products, due to improvements in technology and advancements in applications.

Revered architectural jurors included Principal Alan Organschi, Principal Betsy Williamson, and Design Principal Richard Bonnin. For the first time in this annual competition, the jurors selected awarded one project for technical innovation and one for public art education.

The 2017 Wood Design & Building Awards go to...

Honor
Audain Art Museum (Whistler, British Columbia) / Patkau Architects Washington Fruit & Produce Company (Yakima, Washington) / Graham Baba Architects Georgica Cove (East Hampton, New York) / Bates Masi + Architects Casa Curved (Basel, Switzerland) / Daluz Gonzalez Architekten Collège Jean Monnet Broons (Broons, Bretagne, France) / Dietrich | Untertrifaller Architekten and Colas Durand Architectes Haus B, Stuttgart (Stuttgart, Germany) / Yonder - Architektur und Design Elementary School Unterdorf Höchst (Höchst ,Vorarlberg, Austria) / Dietrich | Untertrifaller Architekten
Merit
Pause (Vancouver, British Columbia) / DBR / Design Build Research, Alsu Sadrieva Bloomberg Tech Hub (San Francisco, California) / IwamotoScott Architecture Discovery & Services Center (Îles-de-Boucherville National Park SÉPAQ, Québec) / Smith Vigeant Architectes Inc. The Owsley Brown II History Center (Louisville, Kentucky) / de Leon & Primmer Architecture Workshop National Arts Centre Rejuvenation (Ottawa, Ontario) / Diamond Schmitt Architects Wooden Ventilation Towers (Stockholm, Sweden) / Rundquist Architects Multi-functional Sports Hall Alice Milliat (Lyon, France) / Dietrich | Untertrifaller Architekten and Tekhnê Architectes Valley Villa (Vilnius, Lithuania) / Arches
Citation
Story Pod (Newmarket, Ontario) / Atelier Kastelic Buffey Inc. Trois-Soeurs Bridge (Québec, Quebec) / ABCP Architecture Pinterest NY (New York, New York) / IwamotoScott Architecture and Spector Group (Architect of Record)Orillia Waterfront Centre (Orillia, Ontario) / Brook McIlroy Inc. Lazaridis Hall (Waterloo, Ontario) / Diamond Schmitt Architects UC Architecture School Building (Santiago , Chile) / Gonzalo Claro Organic Farm (Tangshan, Hebei , China) / ARCHSTUDIO
Special Jury Award - Technical Innovation
Brock Commons Tallwood House (Vancouver, British Columbia) / Acton Ostry Architects Inc.
Special Jury Award - Public Art Education
Ways of Wood (Boston, Massachusetts) / Margen-Lab
Canadian Wood Council Awards
Tanguay Trois-Rivières (Trois-Rivières, Québec) / Coarchitecutre Courtyard House on a River (Greenwater, Washington) / Robert Hutchison Architecture
Sustainable Forestry Initiative - Sponsorship Award
Solana (Whistler, British Columbia) / Murdoch & Company Architecture + Planning Ltd.
Western Red Cedar - Sponsorship Award
Skyline House (Oakland, California) / Terry & Terry Architecture
Sansin - Sponsorship Award
Grange Park Playground (Toronto, Ontario) / PFS Studio
More information about the Wood Design Awards can be found here.

News via: Wood Design & Building Awards.

The 2016 winning submissions of Wood Design & Building magazine's annual Wood Design Awards have been announced, each project demonstrates innovative approaches to and excellence in wood construction within architecture and design. "For architecture to truly be successful, it must transcend buildings and fulfill the structural, functional and aesthetic needs of a community," said Vice-President of Market Development for the Canadian Wood Council, Etienne Lalonde.

# data[].attributes.attachment_link.keywords[]
de leon & primmer architecture workshop

# data[].attributes.attachment_link.title
2017 Wood Design & Building Award Winners Announced

# data[].attributes.attachment_link.description
Jurors looked for submissions which were not only aesthetic but also pushed the perceived limitations of wood construction. The Wood Design & Building Awards program has been in existence for over 30 years, said the Vice-President of Market Development for the Canadian Wood Council, Etienne Lalonde.

# data[].attributes.headline
Why wood is back at the top of the tree for architects | Art and design | The Guardian

# data[].attributes.subject
Why wood is back at the top of the tree for architects | Art and design | The Guardian

# data[].attributes.attachment_link.readable_text
Strong, clean and versatile, engineered timber is the 'new concrete'. With wooden skyscrapers in the offing, could it be the answer to the global housing crisis?

here is a miracle building material - one so environmentally friendly that it extracts carbon from the atmosphere rather than adding to it; a stuff with which structures can go up at lightning speeds, that reduces the noise and disruption of building sites, that can be as strong as steel and much lighter, that makes both construction workers and a building's users happier, and that, with the help of technology, is getting ever more efficient and adaptable. "It's the material of the future," an architect tells me. Its most ardent proselytisers think it could fix the overcrowding of the world's cities. At the same time, this stuff - wood - is so ancient that 18th-century theorists believed that Adam built the first house out of it in the Garden of Eden. Mild-mannered, unassuming timber has gone into a phone box and come out as a super-substance.

Its glamour has unglamorous origins. They go back some time. In the 1990s, because digital technology was already causing the world to use less paper than expected, the Austrian government funded a search for alternative uses for the timber grown in its forests. Gerhard Schickhofer, a professor of engineering, came up with an idea, which was to build up layers of planks, each one at right angles to its neighbours, bond them with glue and press them. This makes a sort of ultra-plywood, called cross-laminated timber (CLT). It's strong, rigid and durable, insulates both heat and sound, and can be prefabricated in factories to high levels of quality and precision. You can make floors, walls, stairs and lift shafts out of it, stacking up panels like an unusually stable tower of dominos.

Although CLT gets the most attention, it is one of several products that go under the name of "engineered timber", which have in common the use of new technology to make a natural material perform like an industrial one. One British early adopter, Alex de Rijke of dRMM architects, who won the 2017 Stirling prize with the company's part-CLT rebuilding of Hastings Pier, called engineered timber the "new concrete". He means that it's a material where the surface you see is also the stuff that holds a building up, which is the stuff that keeps out the weather too. "There can be something very visceral about that," De Rijke says. "We all like stone cathedrals for that reason."

Another enthusiast, Andrew Waugh of Waugh Thistleton, points out the ways in which it is better than concrete. You can put up the structure of a nine-storey block, as he did in Murray Grove, north London, with a team of four carpenters in 27 working days. Engineered timber makes for quieter, calmer, cleaner building sites, without the noise and dust of hammer drills and grinders. It requires a fifth of the deliveries by truck that concrete does. It creates minimal waste (which, as a high percentage of the rubbish that goes to landfill comes from construction, is no small matter).

Whereas a tonne of cement emits nearly a tonne of carbon in its making, a tonne of timber will, through the trees from which it is made, remove up to two tonnes of carbon from the atmosphere. "If you had to invent a machine," says Waugh, "which gives you a renewable supply of building materials while also reducing carbon levels, it would be a tree." Of course, to achieve these gains, building timber has to come from trees that are replaced, but here too it can be beneficent. It can create a demand that encourages the growing of new woodland and care of the existing. Waugh says he has met foresters in the American north-west who are thrilled by the renaissance of timber construction, as it could revive their woods.

Wooden buildings reduce stress, lower heart rates, calm children in classrooms

The environmental benefits aside, the practical arguments are still strong - both Waugh and De Rijke have hard-headed commercial clients who use engineered timber because its speed of construction saves them money. For all these compelling reasons, the world is expected to use a million cubic metres of CLT this year, compared with 2,000 cubic metres in 2003. Its existence is hardly news in the architectural world, but it is now at the point where it's going mainstream.

There will also be wooden skyscrapers, which are the subject of Timber Rising, a forthcoming exhibition at the Roca London Gallery. Michael Green, an architect based in Vancouver, has proposed a 35-storey tower, called Baobab, that would straddle the Périphérique in Paris. With the engineer Eric Karsh, he has worked out that it would now be possible, if not very sensible, to build the Empire State Building out of wood. Green has given a TED talk proclaiming that, as billions of people are moving from countryside to cities, wooden towers could provide the homes they need. Timber, he says, is "the most technologically advanced" form of construction, offering "the first new way to build a skyscraper in 100 years", but one to which "mother nature holds the patent".

Facebook Twitter Pinterest

An illustration of Michael Green's Baobab, a 35-storey tower in Paris. Photograph: Michael Green Architecture

As TED talks often are, Green's is a little preacherly and simplistic, but he can back his enthusiasm with substantial commercial buildings - there is one called T3 in Minneapolis, for example - made out of wood. He is "having conversations", he says, about 30 more. The main obstacle, he believes, to the conquest of the building world by engineered timber is "education". There are not enough professionals who understand it, and those who do are too busy to explain it to others. Building regulations in many cities are still wary of it. Timber, he says, needs "its Eiffel Tower moment" that will make everyone realise its possibilities.

Others are sceptical about the preoccupation with height. De Rijke believes there's a limit to how high a timber structure can sensibly go, and that there are other architectural problems to solve in building tall. And he thinks that, in all the preoccupation with the technical wonders of timber, it's possible to lose sight of the fact that "it is a much better material to live with than any other". It has, he says, "built-in texture, a sense of scale, grain, scent. It affects the air quality about it. You could shut your eyes and still notice the difference."

Facebook Twitter Pinterest

T3, Minneapolis. Photograph: Ema Peter/MGA

Everyone I talk to about timber tells me that, although more research on the subject is needed, wooden buildings make people feel better. They reduce stress, lower heart rates, calm children in classrooms, improve recovery in hospitals - all of which seems intuitively likely. Healthy atmospherics could, of course, be engendered by all kinds of timber, old-fashioned or engineered, but the attraction of the latter would be that it could achieve such qualities in large and efficient new structures.

The only thing is, there are not yet that many buildings made of CLT, or one of its cousins, that fully realise the transformative powers with which it is credited. Quite a lot look much like steel or concrete buildings that happen to be made of wood. They tend to be a bit boxy. Often the timber gets covered with other materials. If engineered timber is truly the material of the future, its architectural possibilities are only just beginning to be discovered.

When you're told that something is wondrous and world-changing, a touch of scepticism is a natural reaction, and the revolution promised by the believers in timber may yet not happen. But the case for it looks compelling - at the very least, it is a good way to build to go with several others. Lastly, in case you are worried, engineered timber buildings don't burn easily. At high temperatures concrete explodes and steel buckles, but wood, if it is thick enough, chars, which forms a self-protective layer. It takes a while for fire to consume it.

Timber Rising: Vertical Visions for the Cities of Tomorrow is at Roca London Gallery, London SW6, 9 Feb-19 May; admission free

Topics

# data[].attributes.attachment_link.title
Why wood is back at the top of the tree for architects

# data[].attributes.attachment_link.description
Strong, clean and versatile, engineered timber is the 'new concrete'. With wooden skyscrapers in the offing, could it be the answer to the global housing crisis?

# data[].attributes.wish_content.attachment_props.text
Construcción de la Torre Eiffel (28 de enero de 1887 - 31 de marzo de 1889)
Fotografía vía @HistoricoPics

# data[].attributes.wish_content.attachment_props.original_text
Construcción de la Torre Eiffel (28 de enero de 1887 - 31 de marzo de 1889)
Fotografía vía @HistoricoPics https://t.co/2EqfaNgn8T

# data[].attributes.attachment_link.embed_code
Construcción de la Torre Eiffel (28 de enero de 1887 - 31 de marzo de 1889)
Fotografía vía @HistoricoPics pic.twitter.com/2EqfaNgn8T
— Incosuma (@IncosumaIng) January 29, 2018

# data[].attributes.attachment_link.metadata.attachment_props_source.data.text
Construcción de la Torre Eiffel (28 de enero de 1887 - 31 de marzo de 1889)
Fotografía vía @HistoricoPics https://t.co/2EqfaNgn8T

# data[].attributes.attachment_link.metadata.attachment_props.original_text
Construcción de la Torre Eiffel (28 de enero de 1887 - 31 de marzo de 1889)
Fotografía vía @HistoricoPics https://t.co/2EqfaNgn8T

# data[].attributes.attachment_link.metadata.attachment_props.text
Construcción de la Torre Eiffel (28 de enero de 1887 - 31 de marzo de 1889)
Fotografía vía @HistoricoPics

# data[].attributes.wish_content.attachment_props.text
RT @BlocIngenieria: Efecto de la resonancia por influencia del viento en el puente Arcos de Alconetar, rio Tajo A-66
vía @emarevaloh 
@Prontubeam @Estructurando

# data[].attributes.wish_content.attachment_props.original_text
RT @BlocIngenieria: Efecto de la resonancia por influencia del viento en el puente Arcos de Alconetar, rio Tajo A-66
vía @emarevaloh 
@Prontubeam @Estructurando https://t.co/mEZeeqHjve

# data[].attributes.attachment_link.embed_code
RT @BlocIngenieria: Efecto de la resonancia por influencia del viento en el puente Arcos de Alconetar, rio Tajo A-66
vía @emarevaloh @Prontubeam @Estructurando pic.twitter.com/mEZeeqHjve
— Euroden (@Euroden_Ing) January 23, 2018

# data[].attributes.attachment_link.metadata.attachment_props_source.data.text
RT @BlocIngenieria: Efecto de la resonancia por influencia del viento en el puente Arcos de Alconetar, rio Tajo A-66
vía @emarevaloh 
@Prontubeam @Estructurando https://t.co/mEZeeqHjve

# data[].attributes.attachment_link.metadata.attachment_props.original_text
RT @BlocIngenieria: Efecto de la resonancia por influencia del viento en el puente Arcos de Alconetar, rio Tajo A-66
vía @emarevaloh 
@Prontubeam @Estructurando https://t.co/mEZeeqHjve

# data[].attributes.attachment_link.metadata.attachment_props.text
RT @BlocIngenieria: Efecto de la resonancia por influencia del viento en el puente Arcos de Alconetar, rio Tajo A-66
vía @emarevaloh 
@Prontubeam @Estructurando

# data[].attributes.attachment_link.readable_text
El lunes de la semana pasada fue un día negro para la ingeniería estructural. Dos colapsos estructurales fueron noticia a nivel mundial. El primero provocaba al menos 75 personas heridas en Indonesia al hundirse el techo del vestíbulo de uno de los edificios de dos torres que acoge la Bolsa de Valores de Yakarta. El segundo, aún peor, dejaba al menos 9 muertos en el colapso del Puente Chirajara, un atirantado en construcción en Colombia.

Ambos colapsos fueron registrados por cámaras y sus imágenes han dado la vuelta al mundo incendiando las redes sociales.

Viendo la cantidad de comentarios que han suscitado estos hechos, en Estructurando se nos ha ocurrido hacer un pequeño análisis de las imágenes aportando algunas ideas de lo que ha podido ocurrir en ambos casos.

En el siguiente video hemos ralentizado al máximo los colapsos para poder apreciar lo que sucedió:

Es obvio que pretender dar una conclusión de lo que ha podido pasar viendo unas imágenes que duran apenas unos segundos es toda una temeridad. El objetivo de este post no es deducir lo que pasó, sino dejar sobre la mesa algunas ideas que se desprenden de las imágenes captadas. Creemos que puede ser interesante, a nivel divulgativo, hablar de lo sucedido y sobretodo, el disponer, con este post, de un lugar donde podáis dejar vuestros comentarios y así enriquecernos con más puntos de vista. De hecho, en el post que publicamos ya hace algún tiempo llamado " Colapsa pasarela atirantada en Bogotá durante la prueba de carga " se ha convertido en todo una colección de opiniones muy enriquecedoras de lo que pasó con aquella pasarela gracias a vuestros comentarios.

Dicho esto, analicemos lo sucedido.

Colapso del Puente Chirajara.

El puente Chirajara es un puente atirantado en construcción en la autopista al Llano, parte de la Ruta Nacional 40 de Colombia, que conecta a las ciudades de Bogotá y Villavicencio.

Lo primero que podemos apreciar en el vídeo del colapso es que los tirantes más cercanos de la pila, tanto en el lado del voladizo como en el de aproximación, pierden tensión.

Justo después de que los cables perdieran tensión, la pila, en el lado más alejado de la cámara, desciende mientras que el otro lado permanece inmóvil. En este punto realmente la estructura tiene un fallo total pues esta pila tipo diamante tenía, como puede apreciarse en la siguiente fotografía, macizado el fuste por debajo del tablero (tímpano):

Otro tipos de pilas diamante para puentes atirantados pueden tener la pila abierta (sin tímpano) debajo del tablero, como por ejemplo:

Sin embargo, el Puente Chirajara tenía un tímpano que realmente no cumplió con su objetivo, mantener los dos fustes de la pila, unidos. En los siguientes fotogramas se puede observar que los fustes de la pila se abren, sin descender lo que puede indicar que el cimiento de la pila no cedió, si no que la unión que ofrecía el tímpano a los dos fustes o no fue suficiente o no fue correctamente ejecutada. De hecho, se puede apreciar un surco en uno de los fustes donde debería estar la unión con el tímpano:

Por tanto, nuestra opinión es que debido a unos esfuerzos descompensados (ya sea por el viento pegando a todo el tablero en voladizo, descompensación lateral de los tiros de los tirantes o algún giro en la cimentación) se produjeron unas tracciones importantes intentando abrir los fustes inferiores que el tímpano no fue capaz de resistir.

Una vez los fustes se "despegaron" del tímpano, el colapso era inevitable. Se abrieron dejando caer toda la pila.

Por último, sólo comentar el buen comportamiento del cimbrado del vano de aproximación que aguanta hasta el último momento:

Colapso de forjado en la Bolsa de Valores de Jakarta (Indonesia).

El forjado involucrado en el accidente de la Bolsa de Valores, estaba compuesto por vigas metálicas aligeradas Boyd y sustentadas por tirantes metálicos a un nivel superior.

En el vídeo a cámara lenta vemos como una aglomeración de personas (alumnos de un instituto que estaban de visita), se concentra para entrar en una de salas del edificio.

En un momento dado, parece que uno de los tirantes, el señalado con la letra A, deja de funcionar cediendo su carga al tirante mas cercano, el señalado con la letra B. Este último, no es capaz de resistir su carga mas la que le llega al no funcionar el tirante A y falla también, cediendo toda su carga al tirante C. De igual manera, el tirante C ahora empieza a soportar su carga mas la que le viene de B que a su vez llevaba carga de A.... como veis, un colapso progresivo o efecto cremallera.

¿Donde vino el primer fallo? Si observamos el vídeo, parece que la mayoría de los tirantes fallaron por el anclaje en nivel superior. De hecho, se puede observar la placa de anclaje de los tirantes en todos ellos (menos en el D, que en ese caso parece fallar en la unión con el forjado):

Pero si observamos el vídeo desde otro ángulo:

Podemos observar que los primeros tirantes en fallar lo hacen por la unión entre el forjado y el propio tirante.

Por tanto, nuestra opinión es que un primer tirante falló en su unión con el forjado y eso originó un colapso en cadena de los demás tirantes que no parecían estar tampoco muy sobrados tanto en su unión con el forjado como su unión con el nivel superior. El que los tirantes fallaran tanto en la unión con el forjado como en su unión con el nivel superior me hace sospechar que las cargas en el cálculo estaban infravaloradas.

Por cierto, este caso me recuerda horrores al caso del " Colapso y derrumbe de las pasarelas del hotel Hyatt Regency " del que ya hablamos hace tiempo y donde explicamos el origen del fallo en base a los resultados de las investigaciones y un análisis mediante elementos finitos.

Espero que con este post hayamos arrojado unas pinceladas de lo que pudo ocurrir en ambos accidentes y lo que, con pericia, se puede llegar a ver en los vídeos.

Finalmente serán las investigaciones de las autoridades, que tendrán mil datos más de lo ocurrido, las que darán una conclusión fiable de lo sucedido. Hasta entonces dejamos abierto este post a vuestros comentarios para todo lo que queráis aportar. Estaremos atentos para ampliar el post con las conclusiones oficiales en cuando aparezcan.
¿Quieres ser el primero en leer nuestros artículos?
Déjanos tu nombre y un email válido, y nosotros te avisaremos cuando hayan novedades en Estructurando

The following two tabs change content below.

# data[].attributes.attachment_link.title
Un lunes negro para la ingeniería estructural: colapso del Puente Chirajara y de un forjado en la Bolsa de Valores de Yakarta. - Estructurando

# data[].attributes.attachment_link.description
El lunes de la semana pasada fue un día negro para la ingeniería estructural. Dos colapsos estructurales fueron noticia a nivel mundial. El primero provocaba al menos 75 personas heridas en Indonesia al hundirse el techo del vestíbulo de uno de los edificios de dos torres que acoge la Bolsa de Valores de Yakarta.

# data[].attributes.attachment_link.readable_text
Construida para la Exposición Universal de 1889 en conmemoración del centenario de la Revolución Francesa, la Torre Eiffel se proyectó como un ejemplo de progreso y un logro de la ciencia y la tecnología del siglo XIX.

Su silueta estructural quizás sea una de las más fácilmente reconocibles del mundo. Pero, ¿sabes por qué tiene la forma que tiene?

En este blog hemos hablado más de una vez cómo factores externos pueden determinar la forma nuestra estructura. Ya hablamos como las turbulencias de un flujo podían hacerlo (en Jukovski, una curva interesante para usar en una estructura), o cómo, para evitar una erosión excesiva, podíamos optar por formas específicas (en Creager, otra curva interesante para usar en una estructura). También hablamos de las estructuras isotensionales que nos ahorran material ( Gaudí, el funicular de cargas y un software para calcular en 3d), o incluso vimos como nuestro astro rey podía tener mucho que decir en la forma de nuestra estructura (en ¿Puede el Sol condicionar la forma de una estructura?)

En este post te explicaremos cuál fue el motivo que llevó, en junio 1884, a los dos ingenieros principales de la empresa Eiffel, Émile Nouguier y Maurice Koechlin, a elegir la forma actual de la Torre Eiffel.

Nouguier y Koechlin tenían experiencia en el cálculo de puentes ferroviarios. Eran ingenieros civiles de gran prestigio en su tiempo y ya habían conseguido puentes con pilas muy altas para la época. Como por ejemplo, el Puente Garavit (Francia) o el Puente María Pía (Portugal).

Gracias a su experiencia, sabían que había tres grandes acciones a considerar para el cálculo de las pilas de un puente: las acciones provenientes del tablero del puente, el viento sobre la pila y el propio peso de esta. En el concurso de la gran torre para la exposición universal, solo tuvieron que utilizar sus conocimientos en pilas de puentes, a sabiendas que para la torre solo tendría dos acciones determinantes: el viento y el peso propio.

De hecho, la solución ya casi la tenían antes de empezar. Miremos por ejemplo, desde Google Maps, la pila del puente María Pía realizada por ellos 10 años antes que la majestuosa torre:

¿Lo veis? Os daré una pista 😉 :

¡Si! ¡Ahí está! Pero ¿por qué esa forma?

Como hemos dicho, las acciones a considerar en la una torre prácticamente son dos: el viento y el peso propio. Analicemos estas acciones detalladamente:

Pensemos primero en el peso propio: si la torre fuera de forma cilíndrica, está claro que las secciones inferiores del cilindro estarían sometidas a mas tensión (rojo) que las secciones superiores (azul) debido a que a igualdad de área de la sección, abajo hay mas peso soportado que en la parte de arriba:

Así pues, lo ideal para para optimizar el material, es reducir sección donde sobra (en la parte de arriba) y aumentar donde falta (en la parte de abajo) para llevar la estructura a una tensión constante en toda su altura. Algo parecido a esto:

Y eso se parece mucho a la Torre Eiffel. Este sólido se llama sólido isotensional y tiene la propiedad de que cada sección del sólido está sometida a la misma tensión (el peso aumenta en la misma medida que aumenta su sección).

Para los que quieran deducir la ecuación del borde de dicho sólido, os la planteo aquí:

Si el volumen de la parte de la torre que está por encima de de la sección a altura x es el volumen de revolución generado por la curva y = f(t):

Y el área de la sección es el círculo de radio f(x):

Entonces, la condición de que la presión a cualquier altura de la torre sea constante queda:

Siendo k una constante. Expresión que nos lleva a la siguiente ecuación funcional:

Que si resolvemos, nos deja la siguiente ecuación diferencial de variables separables:

Cuya solución son funciones de la forma:

Como veis, una función exponencial. Muy al rollo de la forma que tiene la Torre Eiffel.

Pero siento deciros que esta expresión solo vale para explicar una parte de la torre: de la segunda planta para arriba. No está mal, por que es prácticamente 2/3 partes de la torre.

Sin embargo, hay otra condición que define satisfactoriamente la totalidad de la torre. Y esta nace de la segunda acción importante en la estructura: el viento.

Nouguier y Koechlin diseñaron la estructura de modo que, para cada cota, el máximo momento generado por el viento fuese compensado por el momento del peso de la Torre.

Para lograr este equilibrio, el diseño tiene las patas curvadas, de tal modo que las tangentes a ellas, dibujadas en puntos a la misma altura, se corten siempre en el punto por el que pasa la resultante de los esfuerzos del viento sobre la parte que está encima de los puntos en cuestión. O dicho de otra manera mas sencilla: el momento debido al viento en cualquier parte de la Torre, desde una altura dada hasta la cima es igual al momento del peso de esa misma parte:

De esta igualdad de momentos, se puede calcular la curvatura de los bordes de la torre consiguiendo que la estructura resista el empuje del viento de la manera mas eficiente: por su propio peso.

Para el que quiera sacar la ecuación le dejo el planteamiento:

La rebanada de Torre a altura x con grosor dx tiene un peso proporcional a su volumen:

donde ρ es la densidad de la Torre y g es la aceleración debida a la gravedad. El brazo del peso es f0, la mitad de la anchura de la Torre en la base. La fuerza ejercida por el viento sobre cada rebanada es proporcional al área:

donde P es la máxima presión que la Torre puede soportar a altura x sin derrumbarse. La condición de igualdad de momentos nos lleva a la siguiente ecuación integral:

Pero para definir esta curvatura resolviendo la ecuación anterior, Nouguier y Koechlin tenían que conocer de manera precisa como cambia la ley de empujes del viento a lo largo la altura de la torre, w(x). ¡He aquí la proeza de estos ingenieros, quienes ya en 1870 sabían estimar, sin mucho error, la ley de presiones del viento para estructuras de 300 m de altura nunca construidas con anterioridad!

Por último, para hacer el proyecto más aceptable de cara a la opinión pública, Nouguier y Koechlin pidieron al arquitecto Stephen Sauvestre trabajara en la apariencia del proyecto.

Sauvestre propuso pedestales en las patas recubiertos con mampostería, arcos monumentales para unir las columnas y el primer nivel, grandes salas acristaladas en cada planta, un diseño en forma de bulbo para la cima y otros ornamentos para adornar la estructura en su conjunto.
El diseño propuesto final fue seleccionado por unanimidad entre mas de 700 propuestas. Una vez ejecutada, en marzo de 1889, fue la construcción más alta del mundo, permaneciendo así hasta mayo de 1930 (41 años) cuando el Edificio Chrysler, en New York, con 319 m de altura, le quitó el récord. ¿Quieres ser el primero en leer nuestros artículos?
Déjanos tu nombre y un email válido, y nosotros te avisaremos cuando hayan novedades en Estructurando

The following two tabs change content below.

# data[].attributes.attachment_link.title
¿Por qué la Torre Eiffel tiene la forma que tiene? - Estructurando

# data[].attributes.attachment_link.description
Construida para la Exposición Universal de 1889 en conmemoración del centenario de la Revolución Francesa, la Torre Eiffel se proyectó como un ejemplo de progreso y un logro de la ciencia y la tecnología del siglo XIX. Su silueta estructural quizás sea una de las más fácilmente reconocibles del mundo.

# data[].attributes.wish_content.attachment_props.text
Vídeo del colapso de puente en construcción ubicado en el Km 64 de la 3ra fase de la doble calzada de la vía Bogotá-Villavicencio (Colombia) a la altura del sector de Chirajara el 15.01.2018. Diez personas muertas, múltiples heridos y USD$25M al suelo

# data[].attributes.wish_content.attachment_props.original_text
Vídeo del colapso de puente en construcción ubicado en el Km 64 de la 3ra fase de la doble calzada de la vía Bogotá-Villavicencio (Colombia) a la altura del sector de Chirajara el 15.01.2018. Diez personas muertas, múltiples heridos y USD$25M al suelo https://t.co/K93W0pNftn

# data[].attributes.attachment_link.embed_code
Vídeo del colapso de puente en construcción ubicado en el Km 64 de la 3ra fase de la doble calzada de la vía Bogotá-Villavicencio (Colombia) a la altura del sector de Chirajara el 15.01.2018. Diez personas muertas, múltiples heridos y USD$25M al suelo pic.twitter.com/K93W0pNftn
— Estructurando (@Estructurando) January 18, 2018

# data[].attributes.attachment_link.metadata.attachment_props_source.data.text
Vídeo del colapso de puente en construcción ubicado en el Km 64 de la 3ra fase de la doble calzada de la vía Bogotá-Villavicencio (Colombia) a la altura del sector de Chirajara el 15.01.2018. Diez personas muertas, múltiples heridos y USD$25M al suelo https://t.co/K93W0pNftn

# data[].attributes.attachment_link.metadata.attachment_props.original_text
Vídeo del colapso de puente en construcción ubicado en el Km 64 de la 3ra fase de la doble calzada de la vía Bogotá-Villavicencio (Colombia) a la altura del sector de Chirajara el 15.01.2018. Diez personas muertas, múltiples heridos y USD$25M al suelo https://t.co/K93W0pNftn

# data[].attributes.attachment_link.metadata.attachment_props.text
Vídeo del colapso de puente en construcción ubicado en el Km 64 de la 3ra fase de la doble calzada de la vía Bogotá-Villavicencio (Colombia) a la altura del sector de Chirajara el 15.01.2018. Diez personas muertas, múltiples heridos y USD$25M al suelo

# data[].attributes.attachment_link.readable_text
Hace unos años llegó a nuestra oficina un curioso caso que ocurrió en Syldavia: Un elemento ornamental de hormigón armado con importantes problemas de flecha, que había sido bien calculado utilizando las fórmulas normativas pero que tenía una flecha instantánea excesiva, incluso antes de que se desarrollase la flecha diferida.

Se buscaron razones en el proceso constructivo, se realizaron diversos estudios con la norma española EHE, con el Eurocódigo ...

La razón, una laguna en la formulación de la EHE, un ángulo muerto, una zona en la que no funciona. Una situación que, por suerte, casi nunca se da.

FLECHA EN HORMIGÓN ARMADO

Aunque entender el fenómeno de las flechas en hormigón es sencillo, calcularlas de forma precisa es difícil.

La flecha sería fácil de calcular si se cumplieran las siguientes condiciones:

Viga de un solo material: Se puede solucionar homogeneizando el acero a hormigón equivalente. Incluso puede despreciarse el acero a efectos de rigidez, (Número Gordo publicado por muchas normativas.

Material lineal (elástico): Tampoco es problema porque el material no es elástico en Rotura pero sí en Servicio, que es donde se calculan flechas.

Sección constante en la viga: Este es la condición más difícil de salvar. Las fisuras rompen la monotonía de la sección constante, pasando de secciones fisuradas a secciones sin fisurar en unos pocos centímetros.

A lo largo de la historia ha habido diversas expresiones de cálculo de flechas mediante fórmulas que simplifican el quid de la cuestión, la inercia de la viga, a una inercia equivalente constante a lo largo de la viga. Como todas las simplificaciones, funcionan mejor en unos casos y peor en otros. Y lo deseable sería que en su peor situación, estén "del lado de la seguridad". En este vídeo podéis ver una buena explicación de esta estrategia.

FLECHA DE UNAS LAMAS DE FACHADA

Os voy a contar un caso que ocurrió en Syldavia.

Las lamas de fachada de un edificio en Syldavia (donde se aplica la EHE) se han proyectado de hormigón, tiene un ancho de un metro, apoyan cada cinco metros y medio, y el canto se elige cuidadosamente no sólo por su capacidad resistente sino, sobre todo, por su estética, es decir se elige un canto mínimo, de quince cm.

Las lamas se construyen, se izan y se colocan en situación definitiva y ya desde los primeros días comienzan a aparecer flechas excesivas, muy por encima de las flechas calculadas, del orden del doble.

La flecha excesiva suele ser causa de problemas estéticos considerados muchas veces problemas secundarios pero en este caso, por ser un elemento ornamental, la flecha excesiva atenta directamente contra su propia naturaleza.

La Propiedad acudió a nosotros preocupada por esa flecha excesiva generalizada y porque si en la flecha instantánea había ya tal desviación, la flecha a tiempo infinito sería aún mayor.

Inicialmente nos interesamos por el proceso de construcción de las lamas, dosificación del hormigón, tiempo de curado, edad y procedimiento de desmoldeo, transporte, y manipulación.

Siempre que hay un problema de flechas hacemos unas comprobaciones rutinarias porque sabemos donde suelen estar los puntos débiles de ese fenómeno:

Hormigón mal dosificado, excesiva agua de amasado.

Curado deficiente (flecha instantánea alta)

Desmoldeo temprano (flecha diferida alta)

Flecha mal calculada (es más habitual de lo que podría parecer usar un programa de calculo que solo calcula flechas elásticas y no hacer las posteriores correcciones a mano para calcular la flecha fisurada y la flecha diferida, que pueden alcanzar valores entre 3 y 8 veces los elásticos)

En este caso los Agentes de la construcción de la fachada (propiedad, proyectista y constructor) habían tenido una actitud experta y correcta. En el proyecto se había aplicado adecuadamente la EHE y la Prefabricación de las lamas se había hecho de forma exquisita. Todo completamente inusual.

NOS DISPUSIMOS A CALCULAR LAS FLECHAS

Todos los métodos simplificados de cálculo de flechas consisten en interpolar el valor para la inercia bruta (Estado I) y para la inercia fisurada (Estado II). Esta interpolación difiere en cada norma y depende de la relación [Momento de fisuración / Momento actuante en centro de vano]

Comenzamos por la EHE.

La comprobación de la flecha en este elemento es sencilla puesto que toda la carga es permanente. Recordemos los pasos:

1. Flecha elástica, como si el hormigón no fisura: Con una inercia bruta de 22.800 cm4

2. Flecha fisurada como si todo el hormigón fisurase: Con una inercia fisurada de 3.380 cm4

3. Flecha instantánea, considerando la fisuración Con un momento de fisuración = 12,2 mkN y un momento actuante de 13,2 mkN, se obtiene una inercia equivalente de 18.600 cm4

1. Flecha diferida: La flecha diferida cuando no hay armadura de compresión es función única de las edades de puesta en carga y de cálculo y se obtiene una flecha diferida 1,5 veces mayor que la instantánea,

2. Flecha total. La suma de la flecha diferida y la instantánea es finalmente 20 cm

3. Flecha admisible: Se consideró como admisible una flecha L/250 , en este caso, 22 mm.

Con nuestros cálculos pudimos corroborar que según la EHE, las lamas proyectadas cumplían de forma ajustada las limitaciones de flecha (20mm < 22mm).

Sin embargo, de forma generalizada las decenas de lamas construidas tenían flechas instantáneas del orden de 20 mm y en el momento en que reestudiamos las flechas (un año después) éstas tenían ya valores cercanos a los 40 mm.

El siguiente paso que dimos fue calcular con la fórmula simplificada del Eurocódigo. Sabíamos, porque lo habíamos hecho en varias ocasiones, que la EHE y el EC2 arrojan valores de flecha parecidos en estructuras habituales. Pero también sabíamos que si se calculan adecuadamente las flechas lo lógico es que no haya problemas de flechas excesivas, y estaba pasando lo contrario...

Llegados a este punto nos entra la sorpresa en el cuerpo pues la diferencia de evaluación de la flecha con EHE y EC2 es de un 300%. Esto atentaba contra nuestra experiencia previa: Entre EHE y EC2 siempre habíamos encontrado diferencias en torno al 10-20%.

Para entender lo que estaba pasando con el cálculo decidimos encaminar nuestras pesquisas por el cálculo de la flecha y para ello, para estar más seguros de los cálculos, decidimos emprender dos caminos:

Comprobar el gráfico flecha-carga para una carga creciente con los dos métodos en liza EHE y EC-2 simplificado.

Abordar el método más general propuesto en el Eurocódigo, que también nos había dado resultados parecidos en otros casos previos.

El resumen de la investigación numérica llevada a cabo es la siguiente. Os muestro uno de los varios gráficos [carga-flecha] que construimos durante el estudio, y que explica claramente el problema.

Hay una circunstancia que hacía que este problema fuera muy diferente a otros: Al ser un elemento ornamental, la carga es pequeña. Nos pasó desapercibido, pero el hecho de que el momento de Servicio sea muy cercano al de Fisuración es la clave del problema.

Fijaos en la gráfica:
Para valores habituales del momento, varias veces mayor que el de fisuración (parte alta de la gráfica), los valores de las flechas por los diferentes métodos son muy similares. Por ejemplo, para q=8 kN/m hay diferencias de un 20% entre fórmulas. Sin embargo, para cargas cercanas a fisuración (parte baja de la gráfica), (q =3,5 kn/m, que es nuestro caso) hay diferencias de un 400% según qué método se elija.
Ante la disparidad de resultados de los métodos simplificados decidimos utilizar la formulación general del Eurocódigo: interpolar los Estados I y II (bruto y fisurado) pero no en términos de elemento estructural (flechas en el EC2 o inercias en la EHE) sino en términos de parámetro seccional (curvaturas) y luego proceder a calcular la flecha por integración de esas curvaturas.

Aplicar el método general del EC2 al caso de Syldavia dió la razón a la sospecha: El método de la EHE para momentos cercanos al momento de fisuración ajusta muy mal los resultados y del lado de la inseguridad.

La mejor forma de obtener una flecha creíble para cualquier estado de cargas, es el método general del Eurocódigo que requiere calcular las flechas mediante integración de las curvaturas.

Aunque las palabras integración de curvaturas suele poner los pelos de punta a los proyectistas no habituados, os aseguro que es un método sencillo. Si queréis aprender con detalle esta forma de calcular la flecha os lo explicaremos en un próximo post pero para el que no pueda esperar lo puede ver en la próxima MasterClass de ingenio.xyz.
¿Quieres ser el primero en leer nuestros artículos?
Déjanos tu nombre y un email válido, y nosotros te avisaremos cuando hayan novedades en Estructurando

The following two tabs change content below.

# data[].attributes.attachment_link.description
Hace unos años llegó a nuestra oficina un curioso caso que ocurrió en Syldavia: Un elemento ornamental de hormigón armado con importantes problemas de flecha, que había sido bien calculado utilizando las fórmulas normativas pero que tenía una flecha instantánea excesiva, incluso antes de que se desarrollase la flecha diferida.

# data[].attributes.attachment_link.readable_text
Dada la profunda crisis económica sufrida a nivel mundial en los últimos años, es recurrente acudir, por parte de las administraciones, a la rehabilitación de estructuras en lugar de la construcción de obra nueva. Hoy te explicaremos 5 técnicas que podrás tener en cuenta a la hora de reforzar una viga.

En los años previos a la citada crisis económica se produjo, a nivel global, un "boom" en la construcción de vivienda e infraestructuras que ha propiciado un rico abanico de estructuras que mantener.

En pleno proceso de recuperación, y teniendo en cuenta lo anterior, cabe esperar que las inversiones en rehabilitación y mantenimiento crezcan de manera exponencial.

Junto con los pilares o pilas, las vigas son los elementos estructurales más utilizados en edificación y obra pública, no estando exentos de sufrir sus propias patologías casi siempre relacionadas con un exceso de flexión, por lo que en muchas ocasiones han de ser reforzadas y reparadas.

Te presentamos, a continuación, 5 formas de reforzar una viga que todo ingeniero debe conocer.

Recrecido de la sección

Si físicamente es posible, el recrecido de la sección se antoja una solución inmediata y evidente que puede solucionar un problema ocasionado por la insuficiencia de cuantía de acero calculada en el proyecto o puesta en obra.

Ventajas:

Permite añadir armadura a flexión.

Bajo coste.

Desventajas:

No siempre es posible físicamente.

Exige la preparación de la superficie de adherencia y la correcta soldadura de la nueva armadura a los cercos existentes.

Refuerzo con láminas

Constituye otra de las soluciones inmediatas que reforzará externamente nuestro elemento en el caso de que presente problemas provocados por un déficit de capacidad a flexión. Las láminas adheridas funcionarán como un exoesqueleto que absorberá el exceso de deformación al que no pueda hacer frente la viga por sí misma.

Esta técnica se ha realizado usualmente con láminas metálicas, aunque en los últimos tiempos, es común recurrir a la fibra de carbono para realizar dicha tarea, con el que se obtienen unos resultados mejorados.

Ventajas:
Sencillez y rapidez de la operación.
Desventajas:
Obliga a realizar una perfecta adherencia del elemento de refuerzo con la viga, para que éste sea efectivo. Para ello, es inevitable recurrir a las resinas epoxídicas especiales.

Refuerzo con perfiles metálicos

Si los dos métodos anteriores son insuficientes para reforzar nuestro elemento estructural, deberemos recurrir a técnicas más costosas.

Al igual que en los casos anteriores, añadir nuevos perfiles metálicos a una viga de hormigón ya existente requerirá una correcta adherencia para que su acoplamiento sea óptimo.

En el caso concreto de que la viga a reforzar tenga sección en T, podremos emplear una celosía metálica que sustente las alas, técnica muy utilizada en la rehabilitación de puentes.

Ventajas:
Refuerzo de mayor envergadura.
Desventajas:

Coste superior a las alternativas anteriores.

Correcta adherencia con la viga, lo que obliga a utilizar resinas epoxídicas especiales.

Pretensado exterior

Otra opción muy efectiva es la utilización de armadura pretensada exterior. Con ello se consigue dotar a la viga de la contraflecha necesaria para combatir el exceso de flexión producido.

Este sistema es el más indicado para reforzar grandes vigas de puentes, ya que es en ellas donde se presentan las solicitaciones más elevadas.

Ventajas:
No necesita la aplicación de materiales adherentes, con lo que su aplicación resulta mucho más óptima.
Desventajas:
Elevado coste y dificultad de operación.

Cambio del esquema estructural

Por último y aunque en la mayoría de las situaciones no es posible, se presenta la opción de modificar el esquema estructural.

El objetivo principal será disminuir los momentos flectores actuantes en la zona a rehabilitar, consiguiendo así una menor solicitación en la citada sección.

Ante la posibilidad de poder aplicar este método, encontramos 3 formas distintas de modificar estructuralmente la viga:

1. Mediante la eliminación de cargas permanentes: materializado a través de un fresado del recubrimiento superior, si este es excesivo o eliminando cualquier elemento susceptible situado sobre la viga.

2. Reduciendo las luces existentes, con la utilización de jabalcones para la generación de voladizos (cantiléver).

3. Cambiando el esquema estático. Destinado a puentes con juntas con posibilidad de eliminarlas, adoptando un tablero continuo o incluso, porticado.

Ventajas:
Soluciona de manera tajante un problema de cálculo en proyecto.

Desventajas:
No suele ser posible físicamente y si lo es, presenta dificultades que elevan su coste.
Si quieres aprender más sobre Rehabilitación de Estructuras, no dudes en consultar nuestro próximo posgrado:
Como habrás podido comprobar tras leer este artículo, la mayoría de soluciones implican una correcta adherencia entre el refuerzo y el elemento estructural, ya que la elección del adhesivo correcto y su óptima colocación repercutirán en la eficacia de la solución establecida.

Especialízate con:

Máster en Rehabilitación y Ahorro Energético en Edificación.

Elige tu zona geográfica
España Latam México

# data[].attributes.attachment_link.title
5 formas de reforzar una viga que todo ingeniero debe conocer

# data[].attributes.attachment_link.description
Dada la profunda crisis económica sufrida a nivel mundial en los últimos años, es recurrente acudir, por parte de las administraciones, a la rehabilitación de estructuras en lugar de la construcción de obra nueva. Hoy te explicaremos 5 técnicas que podrás tener en cuenta a la hora de reforzar una vi...

# data[].attributes.attachment_link.title
Con calma y con tiempo, he podido ver este vídeo, en el que inequívocamente, aluden a una serie de explosiones programadas, para la caída de las Torres Gemelas el 11 S. Os invito a que lo veáis. Más allá de que recuerda un hecho, verdaderamente deleznable, desde un punto de vista estructural. El asunto no hay por donde cogerlo. Aunque es largo, os invito a que lo veáis. Para los que no domináis mucho el inglés, esta subtitulado, pero sobre todo, muy bien explicado

# data[].attributes.attachment_link.description
Con calma y con tiempo, he podido ver este vídeo, en el que inequívocamente, aluden a una serie de explosiones programadas, para la caída de las Torres Gemelas el 11 S. Os invito a que lo veáis. Más allá de que recuerda un hecho, verdaderamente deleznable, desde un punto de vista estructural.

# data[].attributes.attachment_link.readable_text
Vamos a dedicar este post a repasar un tema que, aunque muchos conocen, es posible que ponga de relieve alguna consideración que en ocasiones se quede en el tintero.

Cuando se calcula una estructura de contención de tierras, existen distintos empujes a considerar dependiendo de la movilidad relativa entre la estructura y las partículas del suelo.

Básicamente podemos hablar de tres tipos de empujes:

Estos empujes tienen un valor creciente según bajamos en la lista, es decir, el activo es el menor de ellos, luego vendría el empuje al reposo y finalmente, el de mayor valor sería el pasivo. Es fundamental, por lo tanto, aplicarlos correctamente.

La idea de aplicación de cada uno es muy sencilla. Si nos fijamos en la gráfica siguiente, solo hay que tener en cuenta:

El empuje activo, se produce cuando la estructura de contención se mueve una magnitud "x", de forma que el terreno se descomprime. Por tanto emplearemos este empuje en el cálculo de muros de contención o muros en ménsula que son libres de moverse en cabeza.

El empuje al reposo, se produce cuando la estructura de contención prácticamente no sufre desplazamientos. Esto se dará cuando la estructura esté convenientemente arriostrada. Un caso típico es el de los muros de sótano en edificación, en los cuales el o los forjados que arriostran al muro, impiden su desplazamiento en cabeza al hacer de diafragma indeformable.

El empuje pasivo, se produce cuando la estructura de contención es la que empuja contra el terreno (en la gráfica se mueve una magnitud "x", en sentido inverso al que lo hacía el activo). Este empuje lo emplearemos, por ejemplo, para equilibrar estructuras contra el deslizamiento que se encuentren empujando contra el terreno.

No entraremos en cómo se evalúan numéricamente estos empujes debido a la extensísima profusión de fórmulas en normativa y bibliografía. El empleo de dichas fórmulas es muy sencillo conociendo ciertos parámetros del terreno.

Después de este repaso básico, pero creo que bastante intuitivo, pondremos un ejemplo que puede conllevar todos los empujes.

Imaginemos, por ejemplo, un depósito rectangular enterrado que se encuentra vacío en su interior (sin fluido) y cuyo movimiento está libre en cabeza. Imaginemos, también, un estribo de un puente con aleta en vuelta sobre el cual el tablero del puente apoye sobre un neopreno y permita el movimiento en cabeza del estribo.
¿Qué tienen en común estas estructuras?
A priori, calcularíamos las dos estructuras con el empuje activo, ya que se pueden mover libremente en cabeza, pero podríamos estar cometiendo un error.

Las dos estructuras tienen en común que poseen muros ortogonales que limitan los desplazamientos en cabeza. En la siguiente figura podemos ver un ejemplo donde se grafican los desplazamientos horizontales del muro (como se puede apreciar en la deformada, el empuje actuaría "hacia fuera" del muro).

Podemos comprobar que, cuando el muro del fondo se encuentra con los ortogonales, el movimiento es nulo, sin embargo, conforme nos alejamos del empotramiento, el muro comienza a comportarse como un muro en ménsula.

Esto significa que en la zona cercana a los muros ortogonales al no producirse movimiento, el terreno no se descomprime y por lo tanto no se movilizará el empuje activo.
El terreno empujará más que el previsto empuje activo, ya lo hará con el empuje al reposo. Por tanto estaríamos del lado de la inseguridad.

¿Cómo podemos acotar la zona de actuación de uno u otro empuje? Precisamente con la gráfica anterior que nos relaciona el movimiento x que sufre el muro en cabeza con su altura H.

Finalmente, para equilibrar la cimentación del muro, si la zapata se encuentra suficientemente enterrada en un terreno que tenga cierta compacidad (no sea un relleno suelto), se podría considerar el empuje pasivo para equilibrar los anteriores.

Vemos por tanto en el ejemplo anterior que en ocasiones no se trata de seleccionar únicamente un tipo de empuje, sino que los tres pueden actuar simultáneamente sobre nuestra estructura de contención.
¿Quieres ser el primero en leer nuestros artículos?
Déjanos tu nombre y un email válido, y nosotros te avisaremos cuando hayan novedades en Estructurando

The following two tabs change content below.

# data[].attributes.attachment_link.title
Tipos de empujes a considerar sobre una estructura de contención - Estructurando

# data[].attributes.attachment_link.description
Vamos a dedicar este post a repasar un tema que, aunque muchos conocen, es posible que ponga de relieve alguna consideración que en ocasiones se quede en el tintero. Cuando se calcula una estructura de contención de tierras, existen distintos empujes a considerar dependiendo de la movilidad relativa entre la estructura y las partículas del suelo.

# data[].attributes.headline
Seattle's second tallest tower rises on steel plates, without rebar - Archpaper.com

# data[].attributes.subject
Seattle's second tallest tower rises on steel plates, without rebar - Archpaper.com

# data[].attributes.body
Substituto de muros de concreto armado por muros con planchas de acero

# data[].attributes.attachment_link.readable_text
Studies are underway for the eventual construction of the Rainier Square Tower in Seattle, which will eschew a traditional concrete-and-rebar core in favor of a new steel plate system. The mixed-use Rainier Square development's tower will be Seattle's second tallest, and the building's modular core will be a proof-of-concept in the earthquake-prone city.

When AN first wrote about the NBBJ-designed and Wright Runstad & Company-developed Rainier Square Tower after its initial unveiling in 2015, comparisons were drawn between the building's kinked shape and a high-heeled boot. The tower has grown from 795 feet tall to 850, but the distinctive massing and glassy facade have remained the same; the building's slope is meant to preserve the view of the adjacent Rainier Tower, designed by Minoru Yamasaki.

The $570 million Rainier Square Tower will forgo a typical high-rise core, which wraps a steel frame around a concrete core that has been reinforced with steel rebar, and will instead use a modular system of steel plates sandwiched with concrete. A boundary system is set up to shape the core, and the cross-tied plates are moved into place, and then filled onsite.

While the construction of a full-scale core mock-up began in October, the general contractor, Lease Crutcher Lewis, has estimated that this alternate method would mean that the superstructure, set to begin work this August, would only take a year to complete. If these claims are true, that's nearly nine months sooner than a comparable tower of this size. And, as the construction schedule is shortened, Wright Runstad is expected to save 2 percent of its original $370 million building costs.

Structural engineer Ron Klemencic, CEO of Magnusson Klemencic Associates (MKA) is the system's mastermind, and says that even with the increased construction speed and 58-story height, he's confident that the tower will be able to withstand stress from wind sheering as well as seismic loads.

The Rainier Square development will not only include the tower, but also a cubic glass-clad hotel wedged between Rainier Tower and Rainier Square Tower. Yamasaki's concrete tower, affectionately named "The Beaver" by Seattle locals for the way the building balloons up from a narrow base akin to a chewed log, is the only original building on the block that will remain.

If the engineering claims bear out and the new core system proves as easy to install as the contractors are expecting, Rainier Square Tower should be complete by April 2020.

# data[].attributes.attachment_link.title
Seattle's second tallest tower rises on steel plates, without rebar

# data[].attributes.attachment_link.description
Studies are underway for the eventual construction of the Rainier Square Tower in Seattle, which will eschew a traditional concrete-and-rebar core in favor of a new steel plate system. The mixed-use Rainier Square development's tower will be Seattle's second tallest, and the building's modular core will be a proof-of-concept in the earthquake-prone city.

# data[].attributes.attachment_link.description
Documental sobre la construcción del Edificio SEI por MAT Latinamerica. Conversamos sobre el diseño y ejecución de un proyecto que aprovecha al máximo todas las ventajas que ofrece el agregado liviano Aliven®.

# data[].attributes.attachment_link.embed_code
View this post on Instagram

A post shared by MAT-LATINAMERICA (@mat_latinamerica)

# data[].attributes.attachment_link.embed_code
View this post on Instagram

A post shared by MAT-LATINAMERICA (@mat_latinamerica)