Seismic fragility analysis of long-span bridges based on explicit time-domain method

Structural seismic fragility analysis is an effective means of assessing the seismic capacity of structures. The cloud method is one of the widely used seismic fragility analysis methods. This method requires tens to hundreds of nonlinear time-history analyses to build the relationship between statistical values of structural seismic demands and seismic intensity measures, which is time consuming for long-span bridge structures. To that end, the explicit time-domain dimension-reduced iteration method is incorporated with the cloud method. With the merit of dimension-reduced representation of time-domain explicit expressions for the structural dynamic responses, only those degrees of freedom associated with the nonlinear elements are involved in the iterative calculation, thus hundreds of nonlinear time history analyses can be conducted on large-scale structures with high efficiency. Then an efficient way to calculate the seismic vulnerability of long-span bridges is achieved. A long-span suspension bridge is taken as the engineering example, and the seismic fragility curves of the bridge corresponding to four damage states are obtained. The results show that the combination of the explicit time-domain dimension-reduced iteration method and the cloud method can effectively improve the efficiency of the structural seismic fragility analysis, especially for assessing the seismic vulnerability of large complex structures such as long-span bridges. © 2020, Nanjing Univ. of Aeronautics an Astronautics. All right reserved.