Structural Robustness Analysis and the Fast Fracture Analogy

Progressive collapse of building structures is analogous in terms of energy to the theory of unstable fast fracture. When a structure deflects due to damage of a member, progressive collapse will occur if the work done by gravity is greater than the energy absorbed by the destroyed member and other damaged members. The main difference between fast fracture in a cracked plate and progressive collapse of a building is that the latter is dynamic and it is possible to evaluate the kinetic energy of the structure as it collapses. By consideration of all of the energy components, the mechanism of progressive collapse may be studied in terms of energy. The fast fracture analogy has been incorporated in a procedure that searches systematically for damage scenarios leading to collapse of a structure. The most critical scenario is the one that requires the least amount of damage energy. This minimum damage energy is proposed as a measure for the robustness of the structure.