竖向地震动对斜交连续梁桥的影响研究

Study on the effect of vertical ground motion on skew continuous girder bridges

为充分了解竖向地震动对斜交连续梁桥的影响,以某3×30m斜交连续梁桥为背景,利用OpenSees软件建立考虑碰撞效应的计算模型,采用时程分析法对比研究了在两种地震动(水平双向地震动和三向地震动)输入工况下对桥梁支座、碰撞效应,以及桥面位移、桥面转角的影响。分析结果显示:考虑竖向地震动后,全桥支座的纵、横向剪切力均有增长,各支座竖向力的变化幅度均很明显,尤其以桥台处支座最为显著;桥台处支座更容易出现剪切、挤压破坏或脱空;由于竖向地震动作用,支座的临界剪切力增大,使其约束作用增强,导致桥面纵、横向位移减小,主梁与桥台、挡块之间的碰撞效应明显减弱,桥面的旋转程度呈现较大降低。

In order to fully understand the influence of considering vertical ground motion or not on a skew continuous beam bridge,taking a three-span skew continuous beam bridge as the engineering background,the bridge calculation model considering longitudinal and transverse pounding effect is established by using software OpenSees.The influence of skew bridge on bearings,pounding effect,deck displacement and deck rotation under two kinds of ground motions(horizontal bidirectional ground motions and three-directional ground motions)input conditions is compared and studied by using time history analysis method.The analysis results show that considering the vertical ground motion,the longitudinal and transverse shear forces of the whole bridge bearings increase,and the vertical force of all bearings changes obviously,especially the abutment bearings.The bearings at the abutment is more prone to shear failure,crushing failure or bearing disengagement.Due to the vertical seismic action,the critical shearing force of the bearings increases,which enhances its restraining effect,the longitudinal and transverse displacement of deck is reduced,the longitudinal pounding effect between girder and abutment,and the transverse pounding effect between girder and shear keys are significantly weakened,and the rotation degree of deck is also greatly reduced.