高桩基础双薄壁墩连续刚构桥的地震响应研究

Research on Seismic Response of Double Thin-walled Pier Continuous Rigid-frame Bridge with High-pile Foundation

摘要:

为探究高桩基础的双薄壁墩连续刚构桥的地震响应机理，基于OpenSees平台建立一座四跨双薄壁墩连续刚构桥有限元模型，进行非线性动力时程分析，通过与未考虑高桩基础桥墩的模型进行对比，可得到高桩基础桥墩对桥梁抗震性能的影响；再通过对比Xtract程序计算桩基截面弯矩曲率的结果，得到高桩基础的桥梁破坏模式。结果表明：（1）考虑采用高桩基础的桥梁各阶周期值均有不同程度的增大，结构柔性显著增强；（2）在地震作用下，桥梁上部结构的纵横向位移较大且幅度接近，墩底弯矩则大幅减小，承台纵向位移明显大于横向位移；（3）桥梁边墩内肢的地震内力响应最大，中墩次之，边墩外肢最小；（4）采用群桩形式的高桩基础在地震作用下不易发生轴压破坏，但在大震作用下角桩桩顶可能出现塑性铰，影响基础正常功能的使用。

Abstract:

To explore the seismic response mechanism of double thin-walled pier continuous rigid-frame bridge with high-pile foundation, a finite element model of a four-span double thin-walled pier continuous rigid-frame bridge is established on the OpenSees platform to carry out the nonlinear dynamic time-history analysis. By comparing with the model without considering the high-pile foundation pier, the influence of the high-pile foundation pier on the seismic performance of the bridge is obtained. By comparing the results of calculating the bending moment curvature of pile foundation section with the Xtract program, the failure mode of the bridge with high-pile foundation is obtained. The results show that: (1) The period value of each stage of the bridge with high-pile foundation is increased to different degrees, and the structural flexibility is increased significantly. (2) Under the action of earthquakes, the longitudinal and lateral displacements of the bridge superstructure are large and close in amplitude, and the bending moment at the base of the pier is greatly reduced. The longitudinal displacement of the base slab is obviously greater than the lateral displacement.(3) The seismic internal force response of the inner leg of the bridge side pier is the largest, followed by the middle pier, and the outer leg of the side pier is the smallest. (4) The high-pile foundation with pile group is not prone to axial compression failure under earthquake action. However, the plastic hinge may appear at the top of corner pile under the action of large earthquake, which affects the normal operation function of foundation.