V形河谷(场地)条件下刚构桥地震动响应研究

Study on Seismic Response of Rigid Frame Bridge in V-shaped Valley(Site)

以(81+150+81)m刚构桥为工程背景,引入黏弹性人工边界的地震动输入方法,采用动力有限元法对三维蜿蜒河谷与桥梁结构的相互作用进行研究,对比分析了一致激励、二维河谷与三维蜿蜒河谷作用下桥梁的多种结构地震动响应。结果表明:1)由于受场地空间的变化,三维蜿蜒河谷对结构墩高变化区域响应更为敏感;2)桥梁结构墩高与桥跨高度(长度)突变处,场地效应会对大多数桥墩、梁跨的位移和内力有着明显的增大作用,与一致激励相比增幅均在40%以上;3)相较二维场地效应,三维蜿蜒地形对蜿蜒河谷谷底附近处的桥梁结构地震动放大效应更为明显,增幅在60%以上。研究表明位于蜿蜒河谷地形中的大跨度建筑结构,若仅考虑一致激励与二维场地效应,不能准确反映结构地震响应,该研究对蜿蜒河谷场地的抗震设计具有一定的指导作用。

Taking(81+150+81)m rigid frame bridge as the engineering background,the dynamic finite element method was introduced to study the interaction between three dimensional winding river valley and bridge structure,with round motion input method of viscoelastic artificial boundary being introduced.The ground motion response of various bridge structures under uniform excitation,two dimensional and three dimensional winding river valley was compared and analyzed.The results show that the 3D meandering river valley is more sensitive to the change of pier height due to the change of site space.When pier height and span height(length)of bridge structure change dramatically,the displacement and internal force of most piers and beam spans increase significantly by more than 40%compared with uniform excitation.Compared with the two-dimensional site effect,three-dimensional meandering terrain has more obvious seismic amplification effect on bridge structures near the bottom of meandering valley,with an increase of more than 60%.The seismic response of long-span building structures located in meandering river valley cannot be accurately reflected if only the uniform excitation and two-dimensional site effect are considered.This study has a certain guiding role for the seismic design of meandering river valley site.