ESTIMATION OF DYNAMIC IMPACT FACTORS FOR SEISMIC DEBRIS LOADS ON BUILDINGS

An important task in the design of buildings against progressive collapse is to account for the dynamic impact effect of falling debris loads caused by extreme abnormal loading conditions. . Design against progressive collapse requires that the building be proportioned such that it has the capacity to limit the local failure to its immediate surrounding area. This implies that the structure should be locally resistant against the dynamic impact effect of debris loads. This paper employs linear-elastic dynamic analysis and contact mechanics to determine dynamic impact load factors for a variety of debris loading scenarios possible for beam members in buildings. Because dynamic-load analysis of building structures can be very complex and time consuming, in some instances it is appropriate to use a static-load approach that applies socalled ‘dynamic impact factors’ to falling debris loads to account for dynamic impact effects. Parametric studies are performed to investigate the effect of different parameters on dynamic load factor values, and some graphs are proposed as design aids for estimating such factors for engineering applications. The effect of nonlinear inelastic material behaviour on impact factor values is discussed through numerical examples.