Seismic fragility analysis considering multidimensional performance limit states and vector-valued seismic intensity measures

To comprehensive quantify seismic intensity, mitigate the dispersion of structural dynamic responses under seismic excitations, and more precisely evaluate the structural seismic fragility, this study proposes a seismic fragility analysis method that concurrently accounts for multidimensional performance limit states and a vector-valued seismic intensity measure (IM). In this study, an optimal selection method for vector-valued IMs is first developed by evaluating 36 individual scalar IMs and conducting correlation analysis via maximal information coefficient (MIC) and multicollinearity diagnosis on the superior ones. Subsequently, marginal distributions of two distinct engineering demand parameters (EDPs) are analyzed, leading to a method for determining the optimal copula function that can account for capture the complex dependence among varying EDPs. Based on the determined optimal vector-valued IM and copula function, the formulation of seismic fragility functions incorporating multidimensional performance limit states and vector-valued IM is established. A five-story steel frame is employed as the case study to validate the proposed methodology. Comparisons with traditional method based on a single EDP demonstrate that the proposed approach provides a more comprehensive evaluation of structural seismic performance.