Structural response and resilience of posttensioned steel frames under column loss

The structural resilience of a steel frame with posttensioned (PT) connections under a column-removal scenario is numerically investigated. Four high-fidelity PT connections finite element (FE) models are developed and compared with the experimental results in the literature, and the developed models describe the behavior of the connections accurately. A method to evaluate middle column removal scenario in a one-story, two-bay frame with PT connections is proposed. The corresponding resisting mechanisms are quantitatively evaluated, which consists of beam mechanism contributed mainly by beam arching action and strand catenary mechanism. A three-dimensional FE model of beam-column substructure with PT connections are developed considering the effect of increasing vertical displacement. Vertical responses associated with different working cases are assessed and the influences of strands, beams and top-seat angles are investigated. In addition, a quantitative evaluation index of the structural resilience under a column-removal scenario for a PT steel frame is proposed based on vertical response displacement. A resilience-based design approach is proposed for the practical engineering design.