Seismic collapse performance assessment of high‐strength steel framed‐tube structures with shear links fabricated using low‐yield‐point steel

Abstract

A high‐strength steel framed‐tube structure with shear links fabricated using low‐yield‐point steel (HSSFTS‐LYPSL) was developed in this study to improve the seismic performance and resilience of the conventional steel framed‐tube structure. When this HSSFTS‐LYPSL is subjected to strong earthquake excitation, its shear links undergo significant plastic deformation to dissipate seismic energy while critical components such as the spandrel beams and columns maintain their elasticity. Furthermore, the replacement of damaged links was facilitated by the use of bolted end‐plate connections. This study designed three typical HSSFTS‐LYPSL examples with 20, 30, and 40 stories to investigate the seismic collapse performances of HSSFTS‐LYPSLs at different seismic intensity levels. Three‐dimensional nonlinear finite element analysis models of these example structures were developed using the OpenSEES software, and the accuracy and effectiveness of the modeling approach was validated by comparing its results with those of quasi‐static tests on sub‐structure assemblies. Next, 40 records each of far‐field and pulse‐type near‐field ground motions were selected and applied with an incremental dynamic analysis (IDA) to obtain response curves for the example structures and calculate their collapse fragility curves and collapse margin ratios (CMRs) utilizing a modified collapse fragility model. Finally, based on the collapse fragility and seismic hazard curves, the seismic collapse risk probability curves of the HSSFTS‐LYPSLs were obtained under far‐ and near‐field earthquakes, revealing that at the maximum considered earthquake level, the CMR values ranged from 5.74 to 7.25 and from 4.85 to 6.67, respectively; at the very rare earthquake (VRE) level, the CMR values ranged from 3.83 to 4.85 and from 3.24 to 4.46, respectively. These results demonstrate that HSSFTS‐LYPSLs exhibit sufficient potential for seismic collapse resistance. As pulse‐type near‐field earthquakes had more significant and adverse impacts on the seismic collapse performances of the HSSFTS‐LYPSLs than far‐field earthquakes, the seismic collapse design of an HSSFTS‐LYPSL should particularly consider the influence of near‐field effects. In addition, the seismic hazard function had a greater effect on the structural seismic collapse risk curves than the collapse fragility function, suggesting that seismic collapse risk curves could provide a comprehensive assessment of HSSFTS‐LYPSL seismic collapse performance. Under far‐ and near‐field earthquakes, the annual collapse risk probabilities of the HSSFTS‐LYPSL examples at the VRE level were within 1.18 × 10−5–4.53 × 10−5, which is below the seismic collapse risk threshold recommended by others, indicating that HSSFTS‐LYPSLs can meet the fourth‐level performance objective of “no collapse failure at the VRE level.” However, this study only conducted seismic collapse and risk assessments using example HSSFTS‐LYPSLs; future research will focus on determining the seismic recovery capacities of and developing post‐earthquake repairability methodologies for HSSFTS‐LYPSLs.