EXPERIMENTAL STUDY ON THE DYNAMIC EFFECTS IN PROGRESSIVE COLLAPSE OF BEAM-COLUMN CONCRETE SUBSTRUCTURES

Progressive collapse is a nonlinear dynamic behavior of structure systems. The key issue in establishing the simplified method for the practical engineering design is to evaluate the dynamic effect accurately. To investigate the dynamic progressive collapse mechanism and the dynamic effect of reinforced concrete substructures, one static and four dynamic experiments were conducted on four specimens, which had the identical dimensions and material properties. The results indicated that the stress concentration and asymmetric deformation in the dynamic tests were severer than those in the static test due to the high strain rate effect. Thus, the cracks developed intensively at the beam ends and the concrete spalling area caused by compression was relatively small in dynamic tests. The general dynamic resistance, in which the effects of dynamic damage and high strain rate to the structural resistance were inherently considered, was able to accurately predict the resistance demand in the real progressive collapse process. In addition, the dynamic amplification effect was enhanced by the effect of dynamic damage and high strain rate, thus the practical dynamic amplification factors were larger than the predicted values of the conventional theory.