考虑变墩高效应的小半径曲线梁桥地震易损性研究

Influence of Pier Heights on Seismic Vulnerability of Sharp-Radius Curved Girder Bridge

为分析墩高变化形式对小半径曲线梁桥地震易损性的影响,以某互通式立交匝道桥第2联为背景,设计渐变型、凹岛型、凸岛型3种墩高变化形式曲线梁桥进行地震易损性研究。在提出的压弯剪扭耦合作用破坏的基础上,采用集中铰-纤维模型的桥墩建模方法,通过SeismoStruct有限元软件建立3种墩高变化形式曲线梁桥模型;选取符合Ⅲ类场地特性的50条地震波,利用能力需求比法,以位移延性比为损伤指标,研究不同变墩高形式下桥墩与支座的地震易损性。结果表明:当小半径曲线梁桥采用3种墩高变化形式时,以弯曲受力为主的中、高墩在地震作用下发生完全破坏概率较低,以弯剪或剪切受力为主的矮墩在强震作用下发生完全破坏概率较大,变墩高曲线梁桥可以适当提高矮墩的抗震能力;凹岛型墩高变化形式会增加矮墩的损伤概率,在抗震设计中应避免选择该墩高变化形式或尽可能优化墩梁连接方式;墩高变化形式对于支座的易损性影响小于对桥墩的影响。

This study investigates the influence of the arrangement of piers with different heights on the seismic vulnerability of the sharp-radius curved girder bridge.For the second continuous unit of a ramp of an interchange,there are five piers with different heights,with the height of the two end piers kept constant,the three intermediate piers are varying in heights.Three ways of arranging the three intermediate piers were compared,including arranging the three piers in the sequence of heights,arranging the highest pier in the center,and arranging the lowest pier in the center.Concentrated hinge-fiber models of the piers of the curved bridge with intentional damages induced by the flexure-shear-torsion interactions were built in SeismoStruct,considering the three different pier arrangements.To accommodate the geological conditions of the bridge site,50 seismic waves that match the characteristics of terrainⅢwere input to study the seismic vulnerability of the piers and bearings.It is concluded that when the piers are arranged in three different ways,the complete damage probabilities of the medium pier and high pier primarily subjected to the flexural forces are relatively low in an earthquake event,while the complete damage probabilities of low piers subjected to the interaction of flexural and shear forces are higher under strong earthquake.It is suggested to enhance the seismic performance of the low piers with a degree.Arranging the lowest pier in the center would increase the damage probability of the pier.It is better not to select this way of pier arrangement in the seismic design,but to optimize the pier-girder connection is justified.Piers are more likely to be damaged than the bearings,considering the pier height variation.