Progressive collapse mechanisms of post-tensioned reinforced concrete frames considering effect of infill walls

This study numerically investigates progressive collapse mechanisms of post-tensioned RC frames under column removal scenarios by using the finite element method. The primary objective of this study is to investigate the influences of infill walls on mechanical behavior of post-tensioned (PT) frames against progressive collapse. Three experimental conventional reinforced concrete (RC) frames are modified into PT reinforced concrete frames: PT bare frame, PT full infilled frame and PT partial infilled frame. The numerical study was performed and the applied vertical load, horizontal displacement, failure process, load redistribution mechanisms, and re-centering capacity of PT frames are investigated under middle column pushdown scenario. Parametric analyses are conducted to study influences of material properties, arrangement of PT tendons, and magnitude of PT forces. The results show that masonry infill walls enhance the resisting capacity; however, change the failure modes and reduce the re-centering capacity of the PT frames against progressive collapse. The presence of the opening reduces the contribution of the infill walls. The PT bare frame have better resilience performance compared with the conventional bare frame. The bed joints, strength of masonry bricks, arrangement of PT tendons and magnitude of PT force greatly influence the progressive collapse resisting capacity of PT frames. Finally, a preliminary design method is proposed to predict the progressive collapse resisting capacity of PT frames with good accuracy and efficiency.