Rapid Time-Varying Seismic Fragility Evaluation with Bounded Uncertainty for a Novel Prestressed Cable-Stayed Steel Frame Based on Multi-Scale Modeling

To overcome the problem of insufficient lateral stiffness in traditional steel frame (TSF) composed of rectangular basic load-bearing elements, prestressed cables are introduced into a novel type of prestressed cable-stayed steel frame (PCSF) formed by TSF, transforming the basic load-bearing elements from rectangles to more stable triangles, to achieve excellent performance of low-cost and significant improvement in lateral stiffness. Given this, the paper studies the seismic fragility of PCSFs and compares them with TSFs. At first, a multi-scale finite element (FE) model for PCSF is established, taking into account both computational accuracy and cost. Then, considering the bounded uncertainty parameters of structures and live loads, combined with the linear regression method (LRM) and sampling method based on the Latin hypercube, the structural material performance reduced according to the corrosion situation at different service times, a rapid time-varying fragility analysis method for PCSFs is established, and verified through fragility analysis method based on incremental dynamic analysis (IDA) method. Finally, the rapid time-varying seismic fragility analysis of TSFs and PCSFs has been developed and implemented. The analysis results present that compared with TSFs, the failure probability of PCSFs is significantly reduced at each damage limit value; with the increase of service time, the failure probability of PCSFs is reduced by 34.4%, 46.3%, 49.4%, and 64.1% compared to TSFs, respectively. In addition, the impact of different prestress levels on seismic fragility is analyzed. The research achievements could provide analytical methods and technical references for seismic loss assessment and engineering applications of PCSFs with different service times.