Question 1. If the number of members, M = (2 x J) - 3 , where J is the number of joints then the frame is determinate

Question 2. to help you calculate the beam reactions, you can redraw the frame as a single beam with the vertical loads all on the line of the beam.

Question 2: Ra = 82.5kN and Rb = 97.5kN

Question 3.

• you cannot work out F1, F2, F3 F4, F5 and F6 all in one go. you can only find out F1, F2, F3 or F4, F5 and F6 by 'cutting through the lines of the members.

• when you do your cut and redraw the frame make sure you include the forces and reactions that are part of that frame

• you then need to go one by one through the members and find their force and direction. to find the force and direction of force in a member you have to pick a joint and take moments about that joint. to do this ensure that the other member forces have either been calculated or that their value will be zero by picking a joint in which an unknown member force will go through that chosen joint.

• if you don't know the direction of the force of the member that you are calculating, assume that it is going clockwise around the joint. If the answer is negative that that means that the direction of the force is just the opposite of what you had chosen and you can rewrite as a positive as long as you change the direction of the arrow.

• if you know the force in the member and its direction then its important that that you use the arrow direction to determine whether it will be going clockwise or anticlockwise around the joint you have chosen. this also applies to the external forces acting on the beam and reactions that you have calculated.