Seismic Vulnerability Analysis of Sea-Crossing Cable-Stayed Bridge Systems Based on Vine Copula Function

The field of bridge earthquake engineering has extensively utilized the theory of seismic vulnerability in recent years. Conventional system-level seismic vulnerability assessment methodologies sometimes fail to accurately represent many interdependencies among structural components. This paper presents an effective Vine Copula-based framework for the seismic vulnerability analysis of sea-crossing cable-stayed bridge systems to overcome this restriction. The seismic vulnerabilities of essential bridge components are regarded as stochastic variables in a Vine Copula framework. An ideal first-tree dependence structure is established by the shortest Hamiltonian path approach utilizing ranked Kendall correlation distances, thus circumventing heuristic variable ordering and redundant trial computations. For each variable pair, the ideal Pair Copula family and parameters are determined by maximum likelihood estimation, utilizing AIC and BIC criteria. The evaluation of system-level seismic vulnerability is conducted using the joint probability density function (PDF) of the complement of component fragilities, thereby enhancing computational efficiency considerably. The numerical findings indicate that the system exceedance probabilities derived from the proposed method are within the limits of the first-order boundary method and are typically nearer to its lower bound. The findings indicate significant interdependencies across essential elements of the bridge system, underscoring the importance of explicitly including these correlations in system-level seismic vulnerability evaluations. The proposed framework offers superior flexibility, resilience, and efficiency for evaluating the seismic susceptibility of complex cable-stayed bridge systems compared to existing copula-based methods.