Numerical and analytical investigation on progressive collapse resistance of prestressed precast concrete frame structures

In this paper, a high-fidelity finite element (FE) model was established to numerically investigate the progressive collapse resistance of prestressed precast concrete (PC) frame structures. In particular, discrete beams are applied in the models to consider the contact between transverse bars and energy-dissipated segment of longitudinal bars, which could accurately simulate the damage mode at beam ends of the frames under column removal scenarios. The FE model was validated by simulating a quasi-static pushdown test on two prestressed PC sub-frames with two stories and two spans under the middle column removal scenario in the first floor. The load transfer mechanism of structural component and stress distribution of steel bars and strands in the beams are investigated. Afterwards, parametric studies are carried out to investigate the effects of the length of bonded segment of steel strands, span-depth ratio of beam, longitudinal reinforcement ratio of beam, and construction of shear bars of beam ends on the vertical resistance of the beams in the failed span. The results show that increasing the top reinforcement ratio of beams or setting additional shear reinforcement at joint regions can effectively increase the vertical resistance of the beam at both the compressive arch action (CAA) and tensile catenary action (TCA) stages. Decreasing the length of bonded segment of steel strands could improve the structural ductility in the process of progressive collapse, but cannot influence the variation of vertical resistance of the beams at both CAA and TCA stages. Finally, an analytical method is proposed to calculate the collapse resistant capacity of the prestressed PC frame structure at CAA stage. The method is validated by the results of previous parametric studies.