基于地震动预测模型的桥梁结构易损性分析

Seismic Fragility Analysis of Bridge Structure Based on Ground Motion Prediction Equation

利用修正的地震动预测模型(GMPE)分别计算特定矩震级M_w、断层距R_(JB)和场地条件(以地下30,m平均剪切波速v_(s30)为代表)时近断层脉冲地震动和非脉冲地震动谱加速度的超越概率.以某两跨连续梁桥为例,利用地震易损性曲线计算特定震级、断层距和场地条件时近断层脉冲地震动和非脉冲地震动作用下桥墩、桥台、支座以及桥梁系统不同损伤水平的超越概率.结果表明,不同矩震级条件下,近断层脉冲型地震动作用下桥梁构件和桥梁系统不同损伤水平的超越概率明显大于非脉冲地震动作用下相应的超越概率,如M_w=6.5、R_(JB)=10,km、v_(s30)=300,m/s时,桥梁系统轻微、中等、严重、完全破坏对应的损伤概率扩大系数(有脉冲与无脉冲条件下结构损伤概率的比值)分别为1.191、1.816、3.464、8.412;而近断层区的桥梁构件及系统的损伤概率扩大系数,随矩震级的增大而减小,随断层距和v_(s30)的增大而增大.

The ground motion acceleration spectrum exceeding probabilities of near-fault pulse-like and non-pulse-like ground motions were calculated separately using the modified ground motion prediction equation（GMPE）for the given moment magnitude Mw,fault distance RJB,and site condition（characterized by the mean value of shear-wave veloc-ity within 30,m underground vs30）. Taking a two-span continuous girder bridge as an example,the probabilities of bridge pier,abutment,bearing and the bridge system exceeding different damage levels under near-fault pulse-like and non-pulse-like ground motions for the given magnitude,fault distance and field condition were calculated based on the fragility curves. Results show that the probabilities of bridge pier,abutment,bearing and the bridge system exceeding different damage levels under near-fault pulse-like ground motion are significantly greater than those under near-fault non-pulse-like ground motions. For example,when Mw=6.5,RJB=10,km and vs30=300,m/s,the expand coefficients（the ratio of damage probability under pulse-like and non-pulse-like ground motions）of slight,medium,serious and complete damage probabilities of the bridge system are separately 1.191,1.816,3.464,and 8.412. And the expand coefficients of damage probability decrease with the increase of moment magnitude but increase with the increase of fault distance and vs30.