Seismic Fragility of Irregular Continuous Rigid Frame Bridge

To investigate the seismic performances of irregular bridges, a seismic vulnerability model for a typical irregular highway bridge was created. By considering the uncertainties of an earthquake and bridge parameters, a model sample database was generated by adopting the sampling method to carry out the seismic vulnerability analysis of a bridge. To obtain the structural dynamic responses, a nonlinear time-history analysis was carried out for the sample database by using the software OpenSees. On the basis of the research on the distribution characteristics of time-history curves of inflection point and the curvature envelope of each pier, pier and bearing damage indexes were determined. The fragility curves of dangerous bridge members were generated by using the probabilistic seismic demand analysis approach, and the first-order reliability theory was employed to generate the fragility curve of a bridge system. The research results show that bearings are easy to damage to an irregular bridge subject to an earthquake action. Compared with its members, an irregular bridge system has a high failure probability. The fragility curves obtained can be used to evaluate the seismic performances of an irregular bridge and provide an evidence for post-earthquake damage identification.