Blast and Impact Loading and Response of Structures
Full Session with Abstracts
Progressive collapse is a nonlinear dynamic behavior of a structural system. The simplified method to evaluate the dynamic effects on the collapse resistance is a key issue in practical engineering designs. The empirical expression of the dynamic amplification factors (DAF) in DoD and GSA guidelines were given by fitting the numerical results of a large number of the linear and nonlinear dynamic analyses of a 3-storey and a 10-storey models. However, the effects of the high strain rate of materials and the stress concentration developed in structural members under the dynamic condition were not considered in the numerical models, which may lead to discrepancies between the predicted and actual DAFs. Specially, the regulated DAFs have not been confirmed by the experimental results, hence in-depth experimental and theoretical studies on the dynamic effects associated with progressive collapse are necessary. To investigate the dynamic progressive collapse mechanism and the dynamic effects of reinforced concrete substructures, one static and four dynamic experiments were conducted on four specimens, with identical dimensions and material properties. The test 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, cracks developed intensively at the beam ends and the concrete spalling area caused by compression was relatively smaller in the dynamic tests. The overall dynamic resistance, in which the effects of dynamic damage and high strain rate to the structural resistance were inherently considered, was able to precisely 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 DAFs were larger than the predicted values due to the conventional theory.