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Collapse of the 1889' High TV Antenna Tower inRaymond, Mississippi

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Collapse of the 1889' High TV Antenna Tower inRaymond, Mississippi

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1. The collapse of the tower occurred because a diagonal member of the tower was removed before the incident which overstressed the tower members. The overstressing resulted in the buckling of the tower legs and the collapse of the tower.

2. The tower legs were constructed with high strength steel of 95,000 psi and their bending stiffness were relatively low. All diagonal members were therefore critical to the structural integrity of the tower and the removal of a diagonal member could substantially decrease the load carrying capacity of the tower legs.

3. The tower contractor did not follow the general industry practice to install a temporary special frame or a come-along cable before disconnecting any member. If a come-along or a special frame was used, this incident would have been avoided.

4. The structural consultant did not caution the contractor in its report about the sensitivity of the tower in regard to the diagonal removals. The structural consultant considered the use of a come-along or a special frame before removing any member of the tower as a standard practice of the contractor. The documents prepared by the tower contractor did not specifically mention that the come-along or special frame must be used by the workers before attempting to remove any members.

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Claiborne Avenue Bridge is a vertical lift bridge in New Orleans, Lousiana over the industrial canal. It was built by the Louisiana Department of Highways.

On May 28, 1993 the tugboat Chris was pushing an empty barge through the canal toward the Mississipi River Lock. As was common at the time, the tugboat captain would have to wait to enter the locks, and he was directed to the side of the canal to ground his barge to keep the waterway clear. However, at 3:30 p. m., the barge collided with a support pier of the bridge, causing a 145-foot (44 m) section of the bridge to collapse onto the western canal bank and onto the barge. Two automobiles plummeted off of the bridge, killing one person and severely injuring two others. The waterway was closed to navigation for 2 days, and the bridge was closed for 2 months while the collapsed span was rebuilt. The concrete debris from the collapsed span was used to protect the new support pier from future collisions.

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Parking Garage #1 with Steel Braces:

The 2-story parking garage has eccentrically braced frames in both loading directions as its primary lateral resisting system. The steel braces are HSS sections with gusset plate connections. These braces were designed in a way that they were not allowed to buckle during an earthquake. However, plastic deformation was concentrated in the gusset plates in the short distance between the end of the brace and the overlap with the gusset plate from the columns

Parking garage #1 with steel braces

Gusset plate yielding (Parking garage #1)

At the interior brace foundations there was foundation uplift due to the unbalanced load that was delivered to the foundation due to gusset plate local buckling

Gusset plate buckling

Parking Garage #2 with Steel Braces:

Parking garage #2 with steel braces

The parking garage was designed in 1991. In the EW loading directions all the top gusset plates fractured due to low cycle fatigue.

Fracture of top gusset plate (Parking Garage #2)

Fracture of both top gusset plates in EW loading direction (Parking Garage #2)

Note that none of these gusset plate details included any stiffener to prevent the out-of-plane movement of the gusset. Fracture initiated at the tow of the weld in the heat affected zone and propagated along the length of the gusset plate.

Fracture initiation at the tow of the weld (Parking Garage #2)

Due to gusset plate fracture outside the separation between the concrete slab and the top of the beam indicated unbalanced loading that was successfully delivered to the columns. Note that in the NS loading direction the primary damage was local buckling of the top gusset plates. However, none of them fractured because the ground motion component in this loading direction was not as strong as the one in the EW direction.

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1967 Silver Bridge

Locale | Point Pleasant, Mason County, West Virginia, United States
Kanauga, Gallia County, Ohio, United States
Material | Steel
Total length | 681.2 m
Longest span | 213.5 m
Design life | 39 years
Opened | 1928
Collapsed | December 15, 1967

The Silver Bridge was an eyebar-chainsuspension bridge built in 1928 and named for the color of its aluminum paint. The bridge carried U.S. Route 35 over the Ohio River, connecting Point Pleasant, West Virginia, andGallipolis, Ohio,

On December 15, 1967, the Silver Bridge collapsed while it was full of rush-hour traffic, resulting in the deaths of 46 people. Two of the victims were never found. Investigation of the wreckage pointed to the cause of the collapse being the failure of a single eyebar in a suspension chain, due to a small defect 0.1 inch (2.5 mm) deep. Analysis showed that the bridge was carrying much heavier loads than it had originally been designed for and had been poorly maintained.

The collapsed bridge was replaced by theSilver Memorial Bridge, which was completed in 1969.

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Failure: Minaret
Location: Meknes, Morocco
Year: 2010
Type: Collapse
Deaths: 41

Bab Berdieyinne Mosque suffered tragedy when the ceiling as well as part of the structural walls of its minaret collapsed into the courtyard on February 19, 2010 [a].

Officials blamed a series of heavy rains for weakening the structure just before the collapse [b], but further analysis revealed several characteristics that contributed to the minaret’s ultimate demise. The 400 year old mosque was composed of rammed earth, or man-made sedimentary rock, making it particularly sensitive to prolonged moisture exposure [c]. The foundation of the site lacked proper drainage, subjecting the structural walls to constant damp conditions—weakening their overall stability [d]. As seen in Figure 2 above, proof of further foundation instability could be seen by the slight tilt of the minaret [f]. In addition, the foundation had been described as insufficiently proportioned [e].

Officials had been criticized prior to the collapse for their negligence of the mosque; multiple cracks were visible in the exterior, one of which was estimated to be 10 meters long [e]. The Imam, or worship leader, of the mosque had requested the mosque be closed for a week for structural investigation but was denied.

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Thai toy factory fire: 10 years after the world’s worst industrial inferno

By Peter Symonds
16 May 2003

On May 10, ten years ago, the worst factory fire in history took place at the Kader Industrial toy factory on the outskirts of the Thai capital of Bangkok. Officially 188 workers, most of them young women from impoverished rural families, died in the blaze. Another 469 were injured; many seriously and permanently, after they were forced to leap from second, third and fourth floors of the buildings to avoid being burnt to death.

Hundreds of workers were packed into each of the three buildings that collapsed. There were no fire extinguishers, no alarms, no sprinkler systems and the elevated walkways between the buildings were either locked or used as storage areas. The buildings themselves were death traps, constructed from un-insulated steel girders that buckled and gave way in less than 15 minutes. Those who attempted to flee through the narrow ground floor exits found them jammed shut.

There were many reactions to this terrible tragedy. The international media barely mentioned the fire. Inside Thailand, however, there was widespread anger. The toy factory, owned by Thai, Hong Kong and Taiwanese investors, was symbolic of the exploitation associated with globalised production. Major toy corporations such as Tyco, Kenner and Arco faxed their orders to Kader, complete with the detailed specifications required to market the goods in the US and Europe. None of them had the slightest interest, however, in the safety standards, wages or conditions for the factory workers who produced the plastic-moulded toys.

The International Committee of the Fourth International (ICFI) recognised the significance of the disaster and dispatched a reporting team to Thailand to investigate. A series of articles, which initially appeared in the newspapers of the ICFI and was later published as a book Industrial Inferno: The story of the Thai Toy Factory Fire, detailed the immediate causes of the fire, allowed survivors and the victims’ families to speak, and exposed the official cover-up and the inaction of various trade union leaders.

More fundamentally, the articles pointed to the underlying changes in world capitalist economy that made such tragedies inevitable. The previous worst industrial fire—at the Triangle Shirtwaist factory in New York in 1911—became the focus for struggles by working people that succeeded in placing limited restraints on the operations of capital. But under conditions where globally mobile investors were not tied to a particular country, let alone to one factory, the prospects for such piecemeal reform had become nil.

“Companies such as Kader Holdings need to move their operations rapidly to take advantage of the newest areas of low-cost labour. That it why the Kader factory outside Bangkok was never intended to be a permanent structure. Cheap shoddy buildings, which failed to meet even the minimal Thai construction requirements, were simply packed to overflowing with workers and machines. Elementary safety precautions were deemed to be unnecessary overheads.

“Thailand’s limited building and safety codes, minimal wage levels and factory regulations are not enforced. Indeed, the government in Thailand attracts foreign capital to its shores by openly advertising the lack of restrictions on the exploitation of workers. The Kader factory was no aberration. All the horrors of nineteenth century European capitalism—child labour, dirty and unsafe working conditions, shanty housing—are on display everywhere in Bangkok.” (1)

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2010: Metrodome

[1,2,3]

The Metrodome was built in 1980 in Minneapolis, Minnesota and is home to the Minnesota Vikings, United FC, and the Golden Gophers.[a] The building will be demolished this year.[a] Hubert H. Humphrey Metrodome has been no stranger to failures involving its inflatable roof structure. “In fact, the December 12, 2010 roof collapse marks the fifth time in the Metrodome’s history the domed roof has failed. Three of the four previous roof collapses, in 1981, 1982, and 1983, have been attributed to snow, while the fourth failure, in 1986, was due to strong winds.” [b] A severe winter storm moved into the Minneapolis region on Saturday, December 11. The storm dumped more than seventeen inches of snow in the Minneapolis area. [b] Anticipating the approaching storm, maintenance crews at the Metrodome took preventative measures by heating the internal temperature of the dome to around 80 degrees while pumping warm air into the cavity separating the inner and outer layers of the roof structure.[c]

At approximately 5:03 A.M. on Sunday December 12, 2010, a sliding mass of snow and ice broke free and slid down the roof, slicing a gaping hole in fabric panel number 104, seen in Figure 3. Although the internal pressurization system of the Metrodome was designed to compensate for minor tears, a hole of this magnitude resulted in the depressurization of the space and ultimately the collapse of the dome. Upon impact with roof equipment, the sliding mass caused tears in fabric panel numbers 43 and 44, directly over midfield.[b]

“On December 12th, a series of firms were contacted to assess the damage that had been done to the Metrodome roof structure.According to the Metropolitan Sports Facilities Commission, it was unanimously accepted that the deflation of the dome was caused by sliding snow and ice impacting the ring beam along the perimeter of the roof structure, rupturing the roof fabric at panel number 104. The tear in this panel caused the loss of internal building pressure resulting in the deflation of the air supported fabric.”[b] Birdair Inc., reported numerous minor tears and abrasions in the fabric. Their examination revealed the loss of the Polytetrafluoroethylene (PTFE) protective coating on the fabric membrane and the formation of cavities at the intersection of glass yarns within the inner fabric. If these depressions reached the depth of the inner woven glass yarns they would have been exposed to the elements, and the infiltration of moisture would ultimately weaken them. The ring beam and columns, and cables were inspected and deemed useable for future use. [b]

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Location: Enschede, the Netherlands
Failure: Roof collapse during extension work at the De Grolsch Veste stadium of FC Twente
Date: July 7, 2011
Deaths: 2

Architecture Firm: IAA Architecten
Structural Engineering Firm: VolkerWessels

July 7, 2011, during work to extend the De Grolsch Veste stadium, the roof of the extension collapsed. FC Twente wanted to increase stadium capacity by further extending the L-shaped extension completed in 2008 into a U-shaped one [a].

The investigation conducted by the Dutch Safety Board revealed that the roof structure’s insufficient stability, and therefore the risk of collapse, was caused by several factors. The main factor was the absence of essential coupling pipes at the back ends of the roof beams and stabilizing connections in the roof structure. During assembly of the roof beams, steel cables were used as a temporary stabilizing measure. The last stabilizing cable was removed on the day of the incident. In addition, the roof structure was already being subjected to additional loading by a video wall, suspension bridges, piles of roofing sheets and the workers present. The investigation also revealed that the roof structure was being subjected to additional loading as a result of dimensional differences between the concrete beams of the stand, the foundation of the steel structure and the steel structure itself. These dimensional deviations in combination with insufficient adjustment options mean that parts of the roof structure could only be inserted by exerting deforming forces. The deformation caused additional tension that reduced the load-bearing capacity. The combination of tensions in the structure as a result of its own weight, dimensional deviations, the load already present and the absence of stabilizing measures caused one of the roof beams to fail as a result of the forces to which it was subjected, which initiated a total collapse [a].

As a result of this accident, twelve workers fell from a great height. Two workers were killed and nine injured, a few of them critically. One worker escaped with bodily injury [a].

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Wolftrap Performing Arts Center - Weld Failure

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Wolftrap Performing Arts Center - Weld Failure

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Wolftrap Performing Arts Center - Weld Failure
Fairfax, VA - January 1985
Christopher Barlow, MAE/BAE, The Pennsylvania State University Class of 2017

Through the peaceful countryside, over grassy hills and tall forests, the sound of music resonates through Vienna in summertime. But this is not Vienna, Austria. This is Vienna, Virginia, a small town thirty miles west of Washington, DC. And of course this is not Julie Andrews and the beloved Von Trapp Family. This is the Wolftrap Performing Arts Center. For nearly fifty years, the Wolftrap Performing Arts center has dazzled its patrons with hundreds of musical guests including legendary world-renowned musicians of every genre as well as today's pop stars. Central to this cultural hub is the Filene Center, a large wooden indoor and outdoor auditorium with seating for 7,000. Truly, the experience offered by this venue is unique and inspiring.

Figure 1. Animation of the crack in girder G-1
However, this peaceful sanctuary was also once the source of a tremendous amount of panic and turmoil for those involved in its construction. Not long after its completion and totally without warning, a monstrous 8-foot crack appeared in a major steel roof girder above the Filene Center, resulting in a 9.5 inch deflection (Figure 1) (Feld & Carper 1996). The park was immediately closed and a lengthy investigation commenced to determine the source of the failure. The drama intensified as the architects, engineers, steel suppliers, fabricators, and contractors involved in the project waited anxiously to read the report that would determine who was at fault and who would pay the hefty cost for repairs. This wiki will summarize various theories regarding the cause of the failure, the final conclusion of the official report, subsequent legal ramifications, as well as lessons learned for future construction of large-scale outdoor venues such as this.

Weld Failure

Figure 2. Types of weld cracks (Credit: Wikimedia Commons)Welding is a complex procedure requiring a high level of skill that many designers often take for granted. The figure to the left shows the many different types of cracks that can occur as a result of insufficient welding (Figure 2). In the case of girder G-1, the initial defect was determined to be a fusion-line edge-type crack in the weld between the web plate of the box member and the backing bar (Kaminetzky 1993). The welding type was designed to be a full penetration weld; however, the backing bar used to create the full penetration weld was not itself continuously welded to the inside of the box, which likely introduced the flaw into the member.

Investigation & Cause of Failure

As is the case with most building failures, there was not one definite cause but a number of mistakes or oversights made throughout the design and delivery process that ultimately triggered the failure. The official report of this failure cited three main causes: "weld flaws, extremely cold temperatures, and poor metallurgy (steel with insufficient fracture toughness," (Feld & Carper 1996). For a thorough discussion of the welding flaws, see above. Unusually low, sub-zero temperatures also played a role in the failure. The theater, used exclusively during the summer, was designed to be open to the elements and unheated. Investigators found that this factor was not taken into account by designers of the girder as the weld material used was not capable of maintaining its required toughness in this environment (ENR Mar. 1985).

Fracture toughness is an important property to be considered when designing any steel structure. A higher fracture toughness means a higher resistance to brittle fracture. Unfortunately, higher strength steel tends to have a lower fracture toughness. Therefore, designers must be careful with balancing these two properties. Simply designing a steel structural element using the highest strength steel available is never a good idea, especially when designing in cold environments. Unfortunately, in the case of the Wolftrap roof girder, there was no minimum requirement set for the fracture toughness of the material (Maranian 2010). This slight omission in the design process, in tandem with the weld flaws and cold temperatures, ultimately caused a failure.

Corrective Actions & Cost

Figure 3. Original design and corrective actions of girder G-1
The crack was first discovered during an inspection after a piece of copper flashing had fallen off the end of the girder (ENR Feb., 1985). Immediately following the discovery of the crack, scaffolding was placed around the structure to hold up the roof until a proper fix could be installed. According to the original designers of the building, the roof was in no danger of collapsing (ENR Feb., 1985). This is because the structure had a sufficient level of redundancy, allowing for the load to take alternate paths to the foundation (Maranian 2010).

The first fix introduced to the structure appointed the removal of all the plates which had been compromised by the crack. Next, new plates were added with more careful welding of the back up bars. Finally, to provide ultimate peace of mind, the entire girder was post-tensioned with cables (Feld & Carper 1996). The image to the left first shows the original design of the member followed by the fixes made after the failure (Figure 3). It is important to note the shop note provided, which states that the back-up bars must also be welded and continuous along the entire length of the beam.

Investigators also recommended that corrective work be applied to the remaining roof structure (ENR Mar. 1985). The roof structure consisted of two large inner girders, each carrying a third of the load, and two outer girders, each carrying a sixth of the load (ENR Feb. 1985). According to the firm coordinating the repairs, "There are many possibilities for similar flaws on the outside of the roof girders," (ENR Mar. 1985).

The final cost of repairs came to a staggering $1.5 million (Los Angeles Times 1985). The companies involved in the original construction include: Dewberry & Davis, the architect and engineers; Bethlehem Steel of Bethlehem, PA, the steel supplier; Globe Iron Construction of Norfolk, the beam fabricator; and G&C Construction of Vienna, the chief contractor. All four firms agreed to hire one forensic engineer, John W. Fisher, to determine the cause of the failure. Although Fisher did not explicitly place blame in his report, he did often gravitate toward the poor workmanship of the beam (Hockstader 1985).

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Magic Mart Roof CollapseBolivar, TN, July 2, 1983

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Magic Mart Roof CollapseBolivar, TN, July 2, 1983

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Collapse

At 6:45 pm on July 2, 1983, a single story retail store, Magic Mart, was subject to a high amount of water from a surprise storm that occurred in the area. This retail store is part of a line of shops along the side of the road in Bolivar, Tennessee. The building was designed with steel wide flange girders and the roof consists of typical steel bar joists. The columns in the building that supported the girders were steel pipe columns. Through investigation, it was shown that the building was constructed differently than it was designed. Smaller, weaker members were used and oriented 90 degrees in comparison to the construction drawings, and the bar joists did not have sufficient bottom chord extensions and stiffener plates to create sufficient strength in the roof structure.

To make matters worst, the construction drawings were not stamped by an architect or engineer, but were prepared by an architectural firm. These drawings, like any drawings used, need to be stamped by a registered professional. While the investigators did not find any issues with the structural designs holding the design loads, there was no designer or structural design representative in the field at the time of construction, and this caused the construction to be sequenced in correctly and fabricated incorrectly and with the wrong sizes. These incorrect construction methods led to a structure that could not hold the design loads, and the roof work done added load and caused the ponding to be more severe, which initiated the collapse. The structure then progressively collapsed, a direct cause of the poor construction methods and incorrect structural members used in the building. The two figures below show the difference between the as designed, and as built contruction.
After the collapse on July 2, 1983 Simpson, Gumpertz & Heger, Inc. arrived on site about a month later, on August 4th, 1983. It was noted that even though a rescue attempt had occurred, the collapse site was still relatively undisturbed. After doing a survey of the collapsed building, SGH attempted to recreate the slope of the building and found that because of the incorrect beam size, the building was not sloped to drain to the rear correctly. There was a low spot towards the back of the building, but it allowed about 3 inches of rain to pond on the roof. It was determined through investigation of the materials that the roof had been patched and re roofed without properly removing the under layers. This only added to the dead load on the roof and the eminent collapse. This low point in the roof was the point where the collapse started. After the rain overloaded the roof, the improperly braced and structurally weak girders and joists progressively collapsed. The welds and connections were sufficiently strong, which helped with pulling the rest of the roof down once the collapse was initiated. (Bell and Parker, 1987)

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[1, 2, 3]

Failure: Rana Plaza Garment Factory Collapse
Location: Savar, near Dhaka, Bangladesh
Date: April 24, 2013
Type: 8-story Progressive Collapse

Architect & Structural Design: Massood Reza of Vastukalpa Consultants
Site Developer: Sohel Rana (currently in prison)

1,129 Dead
2,515 Rescued
*Deadliest accidental structural failure in history [e]

Major cracking shook the building the day before the collapse, alarming workers inside. A consultant structural engineer deemed the building unsafe and urged evacuation, along with local police. Garment factory owners forced employees to work anyway on April 24 by threatening to dock pay. [a] The building—already lacking structural integrity—was shaken to final collapse when generators and heavy machinery restarted after a power outage around 9:00AM. Cracks seen on the 7th floor propagated, causing collapse of the uppermost floor. A domino effect ensued, killing and entrapping thousands of workers in the rubble. [b]

After formal investigation, authorities concluded that the major contributing factors of failure were:      (i) a lot unfit for a multistory building, (ii) shoddy construction and poor materials, (iii) illegal expansion and use, and (iv) a lack of safety regulations or regular inspections.

(i) Investigators claim the building footprint is partially on what once was a swampy landfill, causing uneven settling of the foundation and unstable support of heavy loads. The owner bribed officials for construction permits and to avoid inspections. [b]

(ii) As is a common issue in developing countries, the construction was completed with very cheap materials. The high cost and unavailability of steel led to use of smooth reinforcement bars. After the collapse, officials cited underuse of proper steel rebar (to achieve redundancy) and bad cement in the reinforced concrete construction. Had there been more reinforcement, the collapse may have been localized rather than progressive. [c]

(iii) Though initially designed to be a 5 story building used for office spaces, the final occupation of the building was as an 8-story industrial garment factory. At the time of collapse, the building appeared to be undergoing even further expansion. [a] The heavy machinery and crowded conditions of the garment factories created extreme, uneven loading that surpassed the strength of the structure. There was blatant disregard for building codes by the owner.

(iv) Bangladesh has the lowest wages in the world for garment workers, with over 5,000 factories manufacturing for retailers worldwide paying its over 4 million workers an average of $38 USD per month. [b] Building codes are ignored and inspections are irregular—a consequence of bribery and the political clout of factory owners. Hundreds of others were also killed in factory fires or collapses that year. [d]

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I-35W Bridge Collapse: Some Explanations and Thoughts

Written by Nathan Holth. Copyright 2011. All Rights Reserved.

The media, and even occasionally highway agencies, have done a poor job of reporting exactly why the I-35W Bridge collapsed. This has led to additional misunderstanding about whether other truss bridges, whether or not similar to the I-35W Bridge, pose a collapse risk. Some explanations and thoughts about the I-35W Bridge collapse follow.

The I-35W Bridge collapsed because the gusset plates that formed the connections for the truss bridge members were not thick enough and as a result lacked the proper strength to bear the load the bridge was designed to bear. This problem was not detected when the bridge was first designed because the engineers failed to perform the calculations needed to check whether the gusset plates were the correct size.

The overall design of the I-35W Bridge was safe, reliable, and effective. Had the gusset plates been the correct thickness, the I-35W Bridge collapse would not have occurred. The gusset plates were the only problem with the bridge.

Sverdrup and Parcel, the designers of the I-35W Bridge, were experienced engineers who knew how to properly design a bridge and check the design calculations. While they failed to check the design calculations of the I-35W Bridge, they built many other truss bridges without making this mistake, and those bridges have proven to be safe and reliable bridges.

There is nothing about a "deck cantilever truss" type of bridge that is less safe or less reliable than other types of cantilever truss bridges.

Most truss bridges are considered "fracture critical" meaning that if one part of the bridge fails the entire bridge might collapse. While that sounds scary, the reality is that fracture critical bridges are safe and reliable as long as they are inspected routinely as required by law. A proper bridge inspection will detect problems with truss members long before they even come close to complete failure.

Bridge inspectors and highway agencies are now required to check truss bridges for the type of design errors that were present on the I-35W Bridge. As a result, truss bridges standing today and still open to traffic have been checked to make sure a similar problem does not exist.

The fact that a truss bridge is fracture critical should not be used to justify demolishing and replacing a truss bridge. If a truss bridge is to be replaced, additional reasoning should be present (deterioration, width of roadway, etc) to justify a replacement.

The fact that a bridge "looks like" the I-35W Bridge should not justify a demolition and replacement project. Unless the similar-looking bridge was found to have gusset plates that are too thin, such a bridge would not be at risk for an I-35W type of failure and subsequent collapse.

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University of Virginia Historic Balcony Collapse

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University of Virginia Historic Balcony Collapse

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After the collapse, Whitlock Dalyrumple & Associates were hired to determine the cause of the failure. In their preliminary report, they stated that there was “clear evidence of corrosion” in one of the four tension rods supporting the balcony.

The tension rod was one of two supporting a heart pine beam that spanned 16 feet. There were no signs of deterioration on the wooden beam, or corrosion stains on the wood indicating that the rod was in need of repair. Because of the graduation ceremony, there was a large number of people on the balcony, although it was determined that the balcony was not overloaded (Allen 1997).

There were no visible signs of corrosion on the rod before the collapse. Figure 5 below shows that the corrosion in the rod was concealed within the wooden beam, making it impossible to detect through visual inspection. The most recent inspection of the structure, by Anadac Inc. in 1994, was a routine visual inspection that declared the the building was in good condition, mentioning nothing about the balcony (ENR 1997)

Lawsuits were filed against the Commonwealth of Virginia, the facilities engineering firm hired to do the inspections for the Lawn facilities, the architect and curator for the Academical Village, and three employees at the Universities facilities assessment division. The suits claimed negligence in their duties to protect the public. The suits against the Commonwealth and the university employees were eventually settled outside of court (Dillman, Robert P, PE 2002).

Following the collapse, all suspended balconies on the Lawn had their tension rods removed for inspection, and temporarily supported by scaffolding. Of the nineteen tension rods that support that are used to support six similar balconies on the Pavilions, only one showed any signs of corrosion. The report published by Whitlock Dalyrmple Poston & Associates Inc stated that "Although the overall structural system without the presence of corrosion damage would not meet current building code requirements, the design of the structure was clearly rational and had supported the loads imposed by its typical use over the last 175 years." The replacement rods are stainless steel utilizing steel plates at the connections. These replacement rods are designed to look identical to the original design, maintaining the aesthetic that Jefferson wanted (Allen 1997).

The main cause of the collapse was the failure of one corroded tension rod. The collapse could have been prevented had structural redundancies been implemented in the design. When the tension rod failed, their was nothing to sustain the load safely, resulting in the sudden failure of the balcony. The facility managers had been conducting routine visual inspections of the building, but perhaps visual inspections are not enough on historic structures.

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Installation of the steel frame began in mid-June 1958. By September 5, nearly all of the welding was finished except for the top two floors. Temporary bracing was put in that Friday to hold the unfinished sections in place for the weekend, with all signs pointing to the welding being completed at the start of the new work week. But Mother Nature had other ideas. A severe thunderstorm hit Toronto on September 6, which brought along winds that local weather stations reported were gusting up to 90 km/h. Around 6:20 p.m., due to the wind and possibly a lightning strike, the frame of the building swayed, then collapsed in a scene that newspaper accounts compared to a falling house of sticks and a folding accordion. The roar of over 1,850 tons of falling steel was described in ways ranging from the sound of a jet squadron to a tornado.

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On June 10, 2000, the Millennium Bridge opened as the first pedestrian bridge in London in over 100 years. Designed by Foster and Partners and engineered by Arup, the Millennium Bridge was proclaimed as an engineering feat in its slender profile and expressed structure. On the day of it’s opening, nearly 100,000 people passed over the bridge, spanning across the River Thames from the Tate Modern to St. Paul’s cathedral.

Almost immediately the bridge began to wobble from side to side. The oscillations increased to a magnitude of nearly 70 mm near the middle, large enough to force people to cling to the banisters. The engineers were immediately notified and attempted to mitigate the bridge sway by controlling the number of pedestrians. However, even smaller crowds, well under the bridge’s 2,000 person operational capacity induced lateral movement in the bridge. The Millennium Bridge was closed 2 days later in order to diagnose and remedy the failure.

Several factors played into the unforeseen behavior of the bridge under pedestrian load. Arup engineers understood that the normal gait of humans generates a small lateral force for balancing purposes. However, engineers expected the random step of the pedestrians to largely offset this lateral force, and focused more on the vertical force caused by walking that has been understood and documented in design code and specifications.

What caused this underestimation to manifest itself in the Millennium Bridge more so than many other pedestrian bridges around the world had to do with the natural frequency of the bridge itself. Due to the sleek design of the bridge, the suspension cables run along side instead of well above the bridge as in the Golden Gate Bridge and other traditional suspension bridges. These suspension cables, therefore, were pulled more tightly between supports, increasing their tension and decreasing their length. These properties of the suspension cables along with the relatively light aluminum decking of the walkway, acted to raise the natural frequency of the bridge to very closely match the frequency of the human walk.

The Arup engineers were correct in their assumption that people walk in a random fashion, but failed to understand that even in a random model, a portion of the people are destined to “match step.” In the case of the Millennium Bridge, the unintentional matching of step by a fraction of the crowd was able to induce lateral motion in the bridge. As the motion manifested itself, more and more people began to match step with the motion in order to balance themselves, therefore, magnifying the oscillation of the bridge.

There were two options available to correct the failure. One option was to stiffen the bridge considerably to move the frequency outside of the excitation zone. The other option was to add a system of dampers to absorb and dissipate the lateral energy applied by the pedestrians. It was decided that stiffening the bridge would cause too serious a change to its physical appearance, and therefore, an extensive dampening system was designed. Arup underwent a $8.9 million dollar renovation installing 91 dampers in the bridge in order to disrupt the natural frequency and absorb the energy of the lateral movement. The Millennium Bridge reopened 18 months later.

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Katowice Trade Hall, Silesia, Poland

Image Source

On January 28, 2006, in the midst of a frigid Polish winter, the Katowice Trade Hall was hosting the 56th National Exhibition of Carrier Pigeons. What the 700 people attending didn’t know was that the managers of the building had not had the snow and ice removed from the roof. Damningly, the roof had buckled under the winter snow four years earlier and been rebuilt without being properly inspected or tested.

On this fateful day, the accumulation of snow overloaded the roof of the building by 100 percent, and the roof smashed down on the exhibition, trapping hundreds of people beneath its weight, and exposing them to dangerous sub-zero temperatures.

Rescue teams poured in from the surrounding areas, braving the terrible weather. The building, however, was still unstable, and a second section of the roof collapsed during the rescue effort.

The lacerated metal acted like a freezer, further endangering survivors. Still, rescuers couldn’t heat the air under the ruins because parts of the building were supported by nothing more than piles of snow.

In the end, 65 people died and more than 170 were injured. The architects and managers of the building all faced criminal charges.

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Structural Collapse at the Olympic Swimming VenueAtlanta, Georgia 1996

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Structural Collapse at the Olympic Swimming VenueAtlanta, Georgia 1996

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The structure was near the beginning of the steel erection process when it failed. Just prior to the failure, the steel erection crew had erected a steel frame and a pair of steel joists. The steel joists spanned approximately 176 ft. from an existing structure to the erected steel frame. At the time of failure, lateral support for the steel joists was being provided by the diagonal bridgings between the two joists placed at approximate 20 ft. intervals along the span. The purpose of the new construction is to provide a temporary roof over a grandstand area which is being built specifically for the Olympic Games. The crane's hoist line was released from the rigging and the crane was moved to a position to provide additional temporary support to the structure overnight as per the witness. The crane was rigged to the steel frame at column 11 C.

After the crane was rigged to the steel frame, the workday ended.  Two ironworkers, who were exiting the job trailer, observed the structure fail. The failure occurred approximately 15 to 30 minutes after the crane was released from the paired joists.

The following assumption were made for the analyses:

Though the joists were interconnected with the bolted diagonal bridging at eight locations, the bridging lines were not anchored to any terminus point where the bridging forces could be transferred. In the absence of any viable load path for the bridging forces to be transferred and resisted, the bridging lines were considered inadequate to provide any effective translational restraint to the top chords of the joists and thus could not effectively brace the top chord. If the unbraced length is considered to be the entire span length of the joist as discussed above, the maximum capacity was determined to be minimal

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The Citicorp centre, Manhattan, New York

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The Citicorp centre, Manhattan, New York

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A fifty nine-storey tower designed by William J. Le Meassurier, would have faced a major disaster if a serious error in its design had not been detected in time.

The Citicorp centre was the seventh tallest building in the world at that time. The tower had twenty five thousand individual steel jointed elements. It was supported on four massive columns, which were positioned at the centre of each side allowing the building corners. Its wind bracing system consisted of forty-eight braces, arrayed like giant chevrons. A tuned mass damper was also provided to dampen the wind-induced vibrations.

The bracing system was sensitive to diagonal winds, so the joints must be strong enough to resist the moment, which was the difference between the overturning moment caused by wind forces, and the resisting moment provided by the weight of the building. In the Citicorp tower, stress produced by diagonal winds caused a hundred and sixty percent increase in stress on the bolts at some levels of the building. The weakest joint was discovered at the thirtieth floor,failure of the whole structure would have resulted.

Since the bolted joints were readily accessible, the new proposal was to strengthen the joints, which were weak. All the weak joints were reinforced by welding heavy steel plates over them.

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The Highland Towers collapse was an apartment building collapse that occurred on 11 Dec 1993 in Taman Hillview, Ulu Klang, Selangor, Malaysia.
The collapse of Block 1 of the apartments caused the deaths of 48 people and led to the complete evacuation of the remaining two blocks due to safety concerns. On 11 December 2010, coinciding with the 17th anniversary of the incident,  AETN's History Channel  showed an hour-long documentary on the tragedy, with accounts from the victims, their families and former residents of the Hingland Tower.

Behind the Highland Towers was a small stream of water known as East Creek. East Creek flowed into the site of the Highland Towers before the construction of Highland Towers ,so a pipe system was built to divert the stream to bypass the Highland Towers.

In 1991, a new housing development project, known as Bukit Antarabangsa Development Project, commenced construction on the hilltop located behind the Highland Towers. The hill was cleared of trees and other land-covering plants, exposing the soil to land erosion that is the leading factor of causing landslides.

The water from the new construction site was diverted into the existing pipe system used to divert the flow of East Creek. This overloaded the pipe system and water, sand and silt from both East Creek and the construction site of Bukit Antarabangsa. infiltrated the pipes. The pipes burst at several locations on the hill, and the surrounding soil (behind Block 1) had to absorb the excessive water. The monsoon rainfall in Dec 1993 further worsened the situation.

The water content in the soil became over-saturated to the extent that the soil had turned viscous, in effect becoming mud. By the end of Nov 1993, the hill slope had been saturated with water, and water was seen flowing down the hill slopes and the constructed retaining walls.

Shortly thereafter, a landslide took place and destroyed the constructed retaining walls. The landslide contained an estimated 100,000 square metres of mud – a mass equivalent to 200 Boeing 747  jets. The soil rammed onto the foundation of Block 1, incrementally pushing it forward. After of that constant pressure, the foundations of Block 1 snapped and in December 1993, residents began to see cracks forming and widening on the road around the Highland Towers  a forewarning of collapse. Unfortunately, there was no further investigation before Block 1 collapsed on 11 December 1993.

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July 17th, 1981 :

Kansas City Hyatt Regency Walkway Collapse

The Hyatt Regency Hotel walkway collapse did not occur as a result of innovative design, construction or material use, but rather as a product of numerous management errors. It was these fatal management errors that resulted in the flawed construction detail to be used in the support system of the walkways of the Hotel Atrium (Moncarz, Fellow, and Taylor 2000). Various events and disputed communications between G.C.E. engineers and Havens Steel Company resulted in the design change from a single to a double hanger rod box beam connection on the fourth floor walkways (Texas A&M University 2009). The original design detail of continuous threading of the nut through two stories of the building appeared to be impractical to the contractor and as such he changed the design drawings (Shop Drawing 30 and Erection Drawing E-3) and replaced the original single hanger rod design with a two rod system. In the two rod system, one rod goes from the lower to the upper bridge and the other goes from the upper bridge to the roof truss (Moncarz, Fellow, and Taylor 2000). This change in the hanger rod more or less doubled the load to be transferred on the 4th floor box beam-hanger rod connection (Marshall 1982). The design load for the fourth floor walkway was 20.3 kips (90 kN) when under the new design system the connection should have had a design load of double that, 40.7 kips (181 kN) (Texas A&M University 2009). The original hanger rod design would have been able to hold the load at the time of the collapse (Marshall 1982). Within a year, the box beams resting on the supporting rod nuts and washers were deformed, so that the box beam resting on the nuts and washers on the rods could no longer hold up the load, thus the box beams detached from the ceiling rods and the fourth and second floor walkways of the Hotel. Had this change in the hanger rod design not been made, the maximum capacity of the design connection would have been far short of Kansas City building code requirements which require a minimum value of 33.9 kips (151 kN). The value for the original connection would have been approximately 20.5 kips (91 kN) meaning that the original connection capacity would have been only 60% of what was expected by building codes (Texas A&M University 2009). Apart from the design change, poor management and decisions on the part of the construction firm and engineering firm, and the failure of the connection to meet building codes, other factors resulted in the collapse of the hotel. Quality of workmanship, improper welding and connections, inadequate building material, failure on the part of the hotel to hire building inspectors as well as failure of the building inspectors to allow the building to be occupied despite its hazards were also factors in the collapse (Kieckhafer, Moses, and Warta 2010).

As a result of the fatal miscommunication, the American Society of Civil Engineers has now set the precedent that responsibility lies with the engineer's seal. That is, that whoever places their seal of approval upon a set of plans carries the responsibility for the building and the outcome. It is now also required that all load bearing calculations must be checked by a city appointed engineer and that checks be formal and not “spot checks” (Luth 2000). As an industry, it is important for all responsible parties (architects, engineers, fabricators, etc.) to understand the challenge learned as a result of this fatality. Design presents the industry with a challenge to anticipate any failed detail and to correct it within the design process

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12 December 2010:Hubert H. Humphrey Metrodome Roof Snow Collapse 

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12 December 2010:Hubert H. Humphrey Metrodome Roof Snow Collapse 

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In the early morning hours on December 12, 2010, the air-supported domed roof of the Hubert H. Humphrey Metrodome in Minneapolis, Minnesota collapsed in the midst of a heavy snow storm. Opened in 1982, the Metrodome, as it is commonly referred to, has been host to numerous venues, and currently serves as the home to the University of Minnesota Golden Gophers' baseball team as well as the National Football League's Minnesota Vikings. Notable former occupants include the University of Minnesota Golden Gophers football team (1982-2008) and Major League Baseball's Minnesota Twins (1982-2009). A severe winter storm coupled with high winds dumped more than seventeen inches of wet snow in the Minneapolis region over the weekend of December 10 - 12. The resulting loading caused the fiberglass fabric roof to sag, tear, and deflate, inverting the structure in upon itself.

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August 2014: Investigation of the March 25, 2014 Failure of Gin Pole Rigging, and Collapse of Cellular Towers at Blaine, KS

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August 2014: Investigation of the March 25, 2014 Failure of Gin Pole Rigging, and Collapse of Cellular Towers at Blaine, KS

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On March 25, 2014, two communication towers owned by Union Pacific Railroad (Railroad) collapsed in Blaine, KS, killing two workers. The project consisted of dismantling an older communication tower with all its appurtenances (e.g., antennas, dishes, coaxial cables, etc.). The older tower was located next to a recently constructed tower. At the time of the incident, a gin pole was being raised on the older tower to lower a 10 ft. diameter dish when the rigging of the gin pole suddenly failed causing the 60 ft. tall gin pole to plummet down, resulting in the collapse of both the towers. One employee was situated approximately 20 ft. below the top on the older 250 ft. high tower and was engaged in disconnecting the 10 ft. diameter dish and another employee was on the same tower approximately 80 ft. from the top. One worker died at the scene and the other was pronounced dead at the hospital. There were two additional employees at the site who were not injured.

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Supermarket Roof Collapse - Save-On-Foods, Station Square, Burnaby, B. C., Canada ,1988

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Supermarket Roof Collapse - Save-On-Foods, Station Square, Burnaby, B. C., Canada ,1988

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On April 23, 1988 the rooftop parking deck of a supermarket collapsed at Station Square in Burnaby, British Columbia, Canada. Five minuts after the opening ceremony, four bays of the roof structure came plummeting to the ground. Despite there being an estimated 600 customers and 370 employees in the building when signs of failure started to occur, no one was killed, but 21 people were injured (Closkey 1988, pp.1).
Causes of Failure:

1.Undersized Steel Beam

The report states that a beam of inadequate strength was shown on the design drawings due to a miscalculation in the office of the structural engineer. Summarized in the report are a number of non-conservative design decisions, assumptions, judgments or errors made by the design engineer that reduced the margin of safety.

The report discusses three dead load calculation errors made by the design engineer, that when combined, resulted in a dead load 55% higher than that designed for (Closkey 1988, pp. 23). Firstly, the thickness of the top-slab was initially assumed to be 2 inches (51mm), however, it was later increased to 3 inches (76mm); the beam design did not account for this increase in concrete. Secondly, during construction, extra concrete was placed in order to keep a plane-sloping top-surface under the deflection of the supporting elements. Finally, a walkway was widened using concrete instead of foam-type insulation, as specified in the drawings. Therefore, there was an additional three foot - ten inches of solid concrete of dead load on the beams.

Other errors included miscalculating live loads, unconservative selection of plane at which the critical moment in the beam was calculated and incorrectly assuming an upgrade in yield strength of the steel members based on mill certificates (Closkey 1988, pp.23-25).

On top of all this, for reasons not fully known, the beam that failed was reduced from a W24x104 to a W24x76. Throughout the design process, a number of revisions were made, during which the beam was reduced in size. The Commissioners' report states that they were unable to obtain the supporting calculations made by the design engineer (Closkey, pp.24). However, it was likely due to a design or drafting mistake (Jones et. al, 1990 pp.159).

2.Inadequate Buckling Resistance

The Commissioner's report also attributed the collapse to a second mode of failure which was inadequate buckling resistance of the compression flange. The design engineers had not at any point analyzed stability of the beam column assembly (Jones et. al. pp.159). Research conducted by Essa and Kennedy revisit the failure analysis using distortional buckling finite element software. Findings from this research reveal that "even with improved restraint details at the critical beam-column location, the beam would have been inadequate to support the factored load".

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On July 7, 2011, during work to extend the De Grolsch Veste stadium, the roof of the extension collapsed. FC Twente wanted to increase stadium capacity by further extending the L-shaped extension completed in 2008 into a U-shaped one

The investigation conducted by the Dutch Safety Board revealed that the roof structure’s insufficient stability, and therefore the risk of collapse, was caused by several factors. The main factor was the absence of essential coupling pipes at the back ends of the roof beams and stabilizing connections in the roof structure. During assembly of the roof beams, steel cables were used as a temporary stabilizing measure. The last stabilizing cable was removed on the day of the incident. In addition, the roof structure was already being subjected to additional loading by a video wall, suspension bridges, piles of roofing sheets and the workers present. The investigation also revealed that the roof structure was being subjected to additional loading as a result of dimensional differences between the concrete beams of the stand, the foundation of the steel structure and the steel structure itself. These dimensional deviations in combination with insufficient adjustment options mean that parts of the roof structure could only be inserted by exerting deforming forces. The deformation caused additional tension that reduced the load-bearing capacity. The combination of tensions in the structure as a result of its own weight, dimensional deviations, the load already present and the absence of stabilizing measures caused one of the roof beams to fail as a result of the forces to which it was subjected, which initiated a total collapse

As a result of this accident, twelve workers fell from a great height. Two workers were killed and nine injured, a few of them critically. One worker escaped with bodily injury

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ARLY on May 23rd, a 30-metre section of the glass-and-steel roof at terminal 2E of Paris Charles de Gaulle airport collapsed, crushing everything beneath it. Four people were killed; more would have been had it happened at a busier time, or if policemen had not evacuated some 80 people when cracks appeared. The disaster has shaken France. “How was this possible?” asked Le Parisien, above a full-page photo of the collapsed structure. The terminal was opened less than a year ago. Its dashing architecture, like a giant curved earthworm lined with a concrete honeycomb, was widely seen as a showpiece of French engineering and design flair. Airports, said Le Monde, are not just buildings but “shop windows, ambassadors designed to give the whole world the best impression of French savoir-faire.” The collapse was an “earthquake for France's image”.

Until an official inquiry is completed, the precise cause of the collapse will be unclear. Theories range from design faults and construction errors to a rush to finish the job and budget constraints. Paul Andreu, the architect who designed the terminal for Aéroports de Paris (ADP), the state-owned airport company, and Hubert Fontanel, the chief engineer, each confirmed that there had been cracks early on, but insisted that the problems had been resolved. Mr Andreu said candidly that he “didn't think that he'd made a mistake” in the design, and added that the project had been under cost constraints. The possibility that the entire terminal might have to be pulled down has not been ruled out.

This is bad news for ADP. The company has been trying to build up Charles de Gaulle, the world's eighth-biggest airport, as a rival to London's Heathrow and to Frankfurt. The new terminal, with another satellite under construction, is due to serve the Airbus 380, the giant 555-seater aircraft scheduled to begin flying in 2006. ADP has also been winning lucrative design work for airports abroad, including new terminals at Abu Dhabi and Shanghai. Such ambitions may now be open to question, as will government plans to start privatising ADP next year. For Air France, too, the collapse is a setback. The terminal is critical to the airline's efforts to create a hub for its flights and for those of its partner airlines in the Sky Team alliance.

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August 3, 2005 Collapse of Roof TrussesAt Natatorio de, San Juan, PR

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August 3, 2005 Collapse of Roof TrussesAt Natatorio de, San Juan, PR

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An incident occurred on August 3, 2005 at about 11:30 AM at the construction site of "Natatorio de San Juan" (swimming and diving pool) at San Juan central park, San Juan, PR. The project was owned by the San Juan Municipality. The incident involved the collapse of three long span steel roof trusses and several steel bar joists that fell some fifty feet to the ground, killing two workers and injuring two others. San Juan PR OSHA Area Office's compliance officer arrived at the scene of the incident within an hour and took photographs, and discussed the structural integrity of the remaining structure with the construction personnel. Local police and fire departments immediately responded and engaged in rescue and retrieval of bodies. Bodies were retrieved that same afternoon and the injured were sent to hospitals. The Compliance and Safety Health Officer (CSHO) obtained necessary construction documents to initiate the investigation of the incident to determine whether any OSHA or nationally recognized standards were violated.

The Puerto Rico OSHA, thru Region II, requested the Directorate of Construction to provide engineering assistance for causal determination and to identify potential OSHA standard violations. A structural engineer from the Office of Engineering, Directorate of Construction, visited the incident site on November 8, 2005. At the time of his visit, all failed structural members were already removed from the site as per the demolition plan. Construction in the failed area was not renewed.

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A five storey building which was topped out last week dramatically collapsed yesterday in Ilford, east London.

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A five storey building which was topped out last week dramatically collapsed yesterday in Ilford, east London.

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The steel frame of the new £6.1m City Gates Christian Centre partially came down but all 22 workers on the site escaped unharmed.

It is believed the site team had clocked off for the day just minutes before the collapse.

HSE investigators have still to determine what caused the steel frame structure on the Ashe Construction site to collapse, despite eyewitness speculation.

Ashe confirmed to the Enquirer that the steelwork contractor on the job is Norfolk based DGT Structures.
It is believed steel beams spanning the building’s main auditorium failed bringing down surrounding steel work.

A statement by Ashe said: “An Ashe rapid response team visited the scene and assisted the emergency services in securing the site last night.  A 60m exclusion zone has been put into place.
“The site has now been handed back to us by members of the emergency services, and the Health and Safety Executive and forensic experts will start investigations into how and why the collapse occurred.

“Ashe Construction is doing all it can to assist the HSE and other appropriate parties.”
Eye witness Mick Pandher told the Ilford Recorder: “I looked towards the building and I thought it was a thunder storm at first.

“Seconds later, I saw the whole building going to the floor.

“It was very sudden. It was like when you see a building being demolished. It came down in a straight line.”

A Fire Brigade statement said: “Our specialist urban search and rescue (USAR) crews were called to a collapsed building on Clements Road in Ilford. Six fire engines and four fire rescue units were also at the scene.

“The five storey building was under construction.

“The steel frame surrounding it collapsed and scaffolding from the construction site also fell into a nearby car park, damaging six cars.All 22 construction workers on the site escaped uninjured.
“USAR crews used specially trained dogs to complete a systematic search of the area and were able to confirm that no-one else was involved in the incident, although one passer by was treated for shock by London Ambulance Service.

“A crane on the site was left in a precarious position after the building collapsed and a 60 metre safety cordon was established.”

Work on the site started last June with construction due to last 16 months.

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Sultan Mizan Zainal Abidin Stadium Roof Collapse
Gong Badak, Terengganu - June 2, 2009
An investigation of the failure was performed after the collapse by the government of Malaysia.

First looking at the design process, it was found that the support conditions for the roof were incorrectly analyzed. If supports were modeled as fixed but in reality were constructed as pins or only partially fixed the correct amount of load may not be able to be transmitted to the support. This will cause a large issue with the load path of the roof. The initial design also neglected to analyze for second order effects resulting from deflections in the multiple long spans present in the roof structure. The deflections caused by the self-weight of the roof and resulting second order effects may have been enough to cause a failure even without all the other causes.

The erection of the steel space frame was done incorrectly resulting in improper geometry in the frame. This would have major consequences on the load path of the structure. If the members were not aligned properly they could not transmit all the load they were meant to into the adjacent members. This would result in increased stresses in individual members in which they were not designed to withstand. This caused buckling failures in the tubes along with connection failures in the frame. These small failures are most likely what was observed prior to the collapse that they were going to fix, but in reality were only a symptom of a much bigger issue of extreme negligence on the part of the contractor and workers.

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Union Carbide Building: September 6, 1958

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Union Carbide Building: September 6, 1958

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The Union Carbide Building, designed by Shore and Moffat, was to be a state of the art building that would house the management of Union Carbide's Canadian operations and some of its various subsidiaries (Bradburn 2011). The building was a 180,000 square foot, 215' x 65' wide steel framed structure with columns at 20' centers. One feature of this building was the lack of interior columns to allow for maximum space.

Erection of the steel frame began in mid-June of 1958 at 123 Eglington Avenue in Toronto. On Friday September 5, 1958 all of the connections were welded completely up to the 9th floor by the end of the work day Friday. To stabilize the top two floors of the building temporary bracing was put in place, and the top two floors would be welded at the beginning of the following week. But the events of September 6, 1958 would halt construction and turn a quiet street in Toronto upside down. At approximately 6:20 PM a lightning storm hit Toronto with wind gusts reportedly reaching speeds greater than 90 kph (Bradburn 2011). With the strong winds and a possible lightning strike, the southwest corner of the steel frame began to sway and then the entire 1850 tons of structural steel came crashing to the ground

Investigations done by the city, insurance companies, and consultants proved that the original building design was sufficient. The investigations proved the temporary bracing used on the upper two floors was not sufficient enough to resist the extreme conditions of the September 6th storm (Bradburn 2011). Once the temporary bracing failed the southwest corner of the building collapsed down onto the lower nine floors and the weight plus the force of the impact exceeded the rest of the frame's load capacity, resulting in the pancaking of the entire structure. The original design called for girder to column moment connections with deep concrete spandrel beams in the longitudinal direction, but erection of the concrete beams was not started by the time of the building collapse. Without the concrete beams, the only bracing the 11-story columns had were the very light longitudinal tie beams at each floor in the face of the walls that did not provide nearly enough rigidity to brace the structure against the wind forces that evening .

After the investigations were completed, the building design was deemed sufficient, but to ensure another collapse would not happen again the consultants recommended the addition of deep horizontal trusses between columns the columns of each floor to add more lateral stability during construction and occupancy (Bradburn 2011). The designers took these recommendations into consideration, and rebuilt the structure with the newly added trusses, and the Union Carbide Building was completed and opened by July 1960. After opening in 1960, the Union Carbide operated without incident until 1990 when it was demolished to make room for new construction.

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Systems-engineered Metal Building Collapse, San Marcos, TX            July 27, 2011

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Systems-engineered Metal Building Collapse, San Marcos, TX            July 27, 2011

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A structural failure investigation was carried out on the systems-engineered metal building that collapsed on July 27, 2010 at 209 Thermon Dr., San Marcos, TX. The building was under construction during the collapse which killed one worker and injured another.

The engineer's field observations at the incident site revealed that neither temporary bracings necessary for the safe erection of systems-engineered metal buildings nor permanent wall bracings required to resist lateral loads as shown in the manufacturer's drawings were installed.

the subcontractor responsible for the erection of the systems-engineered metal building did not follow the guidelines indicated in the manufacturer's drawings and the procedures specified in the installation manual developed by the manufacturer to safely erect and maintain the structural stability of systems-engineered metal buildings during construction.

Had the erector followed the procedures specified in the installation manual developed by the Metallic Building Company with respect to temporary and permanent bracings and had the erector complied with the OSHA regulations pertaining to the erection of systems-engineered metal buildings, he would have avoided the collapse of the systems-engineered metal building and thereby prevented the resulting loss of life and injuries.

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February 25, 1987

In 1987 the University of Washington hoped to add to their football team's home, Husky Stadium. This addition was to be a 17,000 seat addition to the North side of their stadium completed in time for the next season's opening game against Stanford on September 5th, but the events of February 25, 1987 would make that goal seem very unreasonable (Griffin). That morning was a sunny clear day at the University of Washington, but something unusual was noticed by some of the construction workers on site, a large crack in the steel frame had begun to form. At 10:07 AM a loud bang was heard all across the UW campus followed by the entire collapse of the North Stands Addition (Griffin). The entire 12 second collapse was documented in the time lapse photos shown below.

After an extensive investigation, the overall design of the structure was deemed sufficient and  collapse was caused by insufficient lateral bracing during the construction process. The roof structure included guy wires which kept the roof structure from experiencing unusual torsional forces on the structure, and the demolition process required cutting of these guy wires. This had to be done in a very controlled and methodical sequence. Unfortunately some of these wires were cut out of order. This resulted in the twisting of the structure which caused the original crack in the roof truss support beams mentioned earlier (Griffin).

One contributing factor to the cause of the collapse was how the tubular guy wires were originally designed. Generally when tubular sections are designed it is assumed the section stays circular when subjected to deformations (Chen 1988 p. 1088). A report done on local and post-buckling behavior of tubular beam-columns shows that tubular sections with walls significantly thinner than the diameter of the section subjected to significant deformations can experience local buckling and distortion of the cross section. The local buckling and distortion of the cross section causes a reduction in the load carrying capacity and the energy absorption section of the guy wire (Chen 1988 p.1088). When the workers cut the guy wires out of order, they subjected the remaining guy wires to loads well above the original design loads. This could have caused large deformations which reduced the roof structure’s ability to resist the wind loads experienced on site.

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Each tower contains about 100,000 tons of steel and concrete. Assuming the aircraft damaged the north tower structure at about 80% of the total height, then roughly about 20,000 tons would be borne by the structure that survived. The reduced structural capacity was the first ingredient in the failure. The second was the heating effect brought on by the burning jet fuel. As temperatures approach 1500 F, structural steel looses its ability to support weight and begins to deform (thermal creep).
The beams are often found severely deformed and twisted in pretzel like fashion with little load carrying capacity. Several have commented that the columns in the Twin Towers melted, causing the failure. It is more likely that the remaining columns and connections failed as a result of the softening of the steel from the heat, rather than melting. Melting takes time and a lot of energy input from the fire. The steel softens first, resulting in a collapse before melting has occurred. When the columns or floor connections failed, structural loading was no longer static, but dynamic. The release of the load, by whichever floor columns failed, allowed about 20,000 tons of building material to impact on the next floor. Even if all the building structure below had been intact, the sudden impact of such a weight could not be sustained by the lower portion of the building that had been designed for static (steady, weight bearing) loads. As the upper portion of the building began to descend with considerable increase in momentum, each floor failed, in succession, terminating in a pile of building debris at the foundation area. This phenomenon is nothing new. Demolition companies use the same principle in destroying buildings by weakening the support structure, using explosives to cause critical columns to fail, and relying on the building mass to do the rest. This failure mode has also been seen in other structures, but to a lesser degree. The upper slab fell onto the floor below, causing failure of the large beam (which, in this case, had not been affected by heating), attesting to the severity of dynamic loading. The south tower failed in a similar fashion as the north tower, although not as uniformly. There was a degree of leaning of the upper structure, before collapse. This is most likely a result of the asymmetry of the direct structural damage from the impact and induced structural damage from heating.