Seismic risk and resilience assessment of composite bridges using hybrid fragility

By comparison of the traditional seismic risk theory and the 2nd-generation Performance-Based Earthquake Engineering (PBEE) method, the two seismic risk assessment methods are unified in a new theoretical framework by expounding the meaning of seismic vulnerability and the definition of forward and backward analysis of PBEE. By use of both experimental and analytical fragility data, a hybrid fragility approach is proposed for continuous damage states of bridges under the 2nd-generation PBEE framework, and the theoretical framework is applied to seismic risk assessment of steel-concrete composite girder bridges commonly used in highway systems. The seismic functionality loss estimation model for bridges based on the vertical carrying capacity and a theoretical framework for seismic risk assessment based on functionality loss are further proposed. Considering the ability of functional recovery for bridges after earthquake events, a method for evaluating the seismic resilience of composite girder bridges considering functional loss is put forward. The framework and the method are applied to a bridge in Italy as a case study.