Seismic Fragility Of Reinforced Concrete Continuous Girder Bridge

ABSTRACT:The bridges, are one of the most important structures in highway systems, and are vulnerable suffering earthquakes. Therefore, it is necessary to analysis the damage of the main members, including piers, bearings and the superstructure of the bridge under the earthquakes. Considering the basic characteristics of the continuous beam bridge structure, the paper has analyzed the fragility of the piers, bearings and main girder. Based on Bayesian theory, the failure probability of the bearings under two conditions, considering elastic deformation of piers and deformation of damaged piers, is analyzed. And the go-through capacity of the whole bridge is calculated. The main contents in this paper are as follows:1. The theory fragility method has been used in the analytical fragility of the bearings under the earthquakes. And we make the relative displacement ductility ratio as the damage parameter of the bearings. The bearing behavior under earthquakes has been calculated by nonlinear time history analysis, considering the elastic displacement of the piers and displacement of damaged piers, respectively, and failure probabilities of the bearings are obtained.2. Based on Bayesian theory, considering the failure probabilities of the piers and the bearings, as well as the interaction between them, the failure probabilities of the bearings considering the damage in piers have been reached. Then, the fragility curves of the bearings have been gotten.3. Combining the analytical results of the piers and the bearings, take the angle of rotation of the main girder as the damage parameter. The main girder has been analyzed by nonlinear time history analysis, and then the failure probabilities of the main girder have been conducted. Further, the fragility curves of the main girder have been obtained.4. Based on Bayesian theory, a comprehensive analysis of vulnerability of the whole bridge under earthquakes has been analyzed, and the fragility curves of the whole bridge under different failure modes are presented. Combined with fragility curves of the whole bridge, the go-through capacity of the bridge after the earthquake is evaluated.