Analytical Assessment of Reinforced Concrete Beams under Large Displacements due to Progressive Collapse

During the progressive collapse of structures, reinforced concrete (RC) beams must sustain large displacements which are not considered in usual design procedures. Regarding the extensive studies during the recent years, compressive arching and catenary actions are introduced as the main resistance mechanisms against progressive collapse. Despite the extensive studies, there is still a running debate on reliable estimation of the capacities and ultimate resistance of RC members against progressive collapse. Thus, in the present study, a simple and practical analytical method is developed to estimate the ultimate compressive arching capacity of RC beams under large displacements due to progressive collapse. The proposed method is developed based on the membrane action in RC slabs and analytical calculation of lateral stiffness of the structural system. Despite the available methods in the literature, the ultimate arching capacity of RC beams is obtained based on a single-stage procedure. The capability of the introduced method is evaluated utilizing a comprehensive laboratory database, including 99 experimental studies in the technical literature. According to the performed evaluations, the proposed method provides a reliable framework to estimate the arching capacity of reinforced concrete beams in large displacements. Any change in failure mode from flexural action to shear mechanism and increasing the rigidity of the connections leading to an improvement in lateral stiffness could reduce the accuracy of the proposed method.