Damage indices and fragility assessment of coupled low-yield-point steel plate shear walls

Abstract A new multiple lateral force resisting system consisting of coupled low-yield-point steel plate shear walls (C-LSPSW) was proposed as a promising alternative to improve the ductility, energy-dissipation capacity, architectural flexibility, and economic efficiency of steel plate shear walls (SPSWs). To investigate its seismic performance and damage behavior, eight C-LSPSW specimens with different configuration parameters, including two different stories and four different section sizes of coupling beams (CBs), were designed and the corresponding numerical models were established by verified modeling approach. The incremental dynamic analyses (IDA) were conducted on these specimens, and the multi-stage damage indices of the C-LSPSW system were proposed based on different damage states. The design suggestions for the C-LSPSW system were proposed in terms of the fragility analyses. The analytical results demonstrated that the ductile damage mechanism with the sequence of “infill plates to CBs or horizontal boundary elements (HBEs) to vertical boundary elements (VBEs) was achieved more easily in the C-LSPSW system, which gave full play to the superiority of multiple seismic defense lines. Under high seismic excitation, the failure probability of the C-LSPSW system was smaller than that of the LSPSW system, and the coupling superiority was more obvious in higher structures. The optimum performance of C-LSPSW system was observed when the plastic moment capacity ratio of CBs to HBEs ( MpCB/MpHBE) was 2.0. As a result, an optimal solution with MpCB/MpHBE = 2.0 was suggested as a good compromise between the architectural requirements, material efficiency, and seismic performance.