Progressive collapse resistance and uncertainty analysis of post-tensioned steel frames

Post-tensioned (PT) steel frames with prestressed strands and replaceable energy dissipation angles demonstrate enhanced resilience during earthquakes compared to traditional steel frames. This study aimed to investigate the collapse resistance of PT steel frames in the different column removal scenarios. A macro model of a typical PT connection was developed using OpenSeesPy, a python library for the OpenSees finite element software framework. The model was validated by experimental results and applied to a six-story, four-bay office building. The collapse resistance mechanism of the building was analyzed in detail through a static pushdown nonlinear analysis, considering the edge column and middle column removal scenarios on the ground floor. A probabilistic analysis was conducted, incorporating uncertainty modeling and sensitivity analysis, to determine the effect of parameters on the collapse resistance of the structure. The collapse fragility functions corresponding to different structural performance levels were developed by the Latin hypercube sampling method with random pushdown analysis under the edge column removal and middle column removal scenarios, respectively. The uncertainty analysis results indicated that the PT steel frame investigated in this work has good collapse resistance.