Seismic Fragility Analysis of a Reinforced Concrete Frame Structure with a High Aspect Ratio Plane Based on Double-Index Limit States

The finite element models are established for a reinforced concrete frame structure with a high aspect ratio plane. This building is the podium of a complex commercial project located in Jinan, China. By inputting three-way seismic waves, the structural fragility research is carried out based on comparing the fragility curves with consideration on the inter-story drift and the inter-story torsion angle separately (single-index) and comprehensively (double-index with translation-torsion coupling effect). After adding buckling-restrained braces (BRB) into the structure, seismic fragility analyses are done by the same method. The improvements in the structural seismic performance are investigated, and the contributions from BRBs to reducing the structural seismic fragility are quantified. The results show that the translation-torsion coupling effect should be seriously considered in the fragility assessment of reinforced concrete frame structures with a high aspect ratio plane. In addition, the contributions from the BRBs in controlling the translation-torsion coupling effect and improving the structural seismic performance and collapse resistance are very significant.