Failure Mode of Isolated Beam Bridge by Weighted Rank Sum Ratio Method

To estimate the failure modes of seismically isolated continuous girder bridges, a practical engineering with six spans was analyzed considering the uncertainty of seismic ground motions. Sixteen ground motion records were selected to be used in IDA method, which could provide sufficient accuracy of seismic analysis demands, and the PGA of these records were distributed in a wide range. Bearings and the bottom of piers were the most vulnerable parts of the bridge, of which failure criteria were estimated by displacement and modified Park-Ang damage theory, respectively. And weighted rank sum ratio method was adopted to analyze evaluation information of the bridge under sixteen ground motion records, then the statistically significant failure modes and the weakest failure mode of the bridge were identified. The results show that the final failure mode of the isolation continuous girder bridge arises at the isolation bearings of the middle piers, at the isolation bearings of the transition piers, and at the bottom of side piers and bearings. The weakest failure mode of this bridge happens with all isolation bearings cease to be effective first, then it comes to the bottom of the side piers and the middle piers, and finally the transitional piers.