1. The problem statement, all variables and given/known data Determine the failure mechanism and plastic moment for the following structure, using either the upper bound or lower bound theorem for plastic analysis. Picture (There is a physical hinge in the middle of the structure) 2. Relevant equations Internal Work = External Work Euler-Bernoulli Beam Theory 3. The attempt at a solution The structure is a mechanism from the word go. My question is the conceptual question; namely, why? Solving the structure via equilibrium confirms the problem, but its the concept that I can not grasp. Any help would be appreciated.