Progressive collapse resistance of post-tensioned concrete beam-column assemblies under a middle column removal scenario

Post-tensioning technology is widely used in engineering practice. Recent researches showed that post-tensioned (PT) beam-column assemblies are able to enhance the structural capacity against progressive collapse triggered by a column removal scenario (CRS), but the influence of various parameters of post-tensioning on progressive collapse resistance is not fully illustrated. To fill this gap, high-fidelity numerical models are built using LS-DYNA to analyze structural behaviour of a reinforced concrete (RC) beam-column assembly and a PT concrete counterpart under middle CRS based on a referenced experimental program. Each assembly consists of a two single-bay beams, a middle joint and two enlarged side column stubs. The referenced RC assembly is mainly used to calibrate the boundary conditions to the assemblies. The model of PT assembly is validated through the comparisons of global resistance, failure pattern as well as the stress development of post-tensioning tendons with experimental data. Thereafter, the PT model is further used to investigate the effects of magnitude of prestressing and tendon profile on the overall response of PT specimens under middle CRS. Results indicate that the ability of PT tendons to enhance structural resistance is mainly because the total area of reinforcement is increased regardless of the prestressing magnitude, and straight and parabolic tendon profiles result in similar structural resistance but different failure modes.