1. In more than one paragraph but less than a page, discuss some of the failure modes experienced in the collapse of the World Trade Center and how they might have been prevented.
2. A truss ABC supports a load W at joint B as shown. The length L1 of member AB is fixed, but the length of strut BC varies as the angle θ is changed. Strut BC has a solid circular cross section. Assuming that collapse occurs by buckling of the strut, determine the angle θ for minimum weight of the strut.
