桥台对连续梁桥纵向地震响应的影响

Effect of Abutment on the Longitudinal Seismic Response of a Continuous Girder Bridge

摘要:

以一座带桩基础U形座式桥台的连续梁桥为背景，采用非线性时程方法，研究主梁、桥台和台后填土相互作用对桥梁结构纵向地震响应的影响，探索地震作用下容许桥台背墙进入弯曲屈服或背墙底剪断对桥梁支座位移、桥墩延性需求和桥台单桩弯矩地震响应的影响，并以桥台背墙的屈服弯矩、台梁之间间隙和墩高为参数进行参数分析.结果表明，与容许桥台背墙进入弯曲屈服相比，容许桥台背墙底部被剪断工况中的支座纵向位移、桥墩位移延性需求和桥台单桩弯矩明显减小；增大桥台背墙屈服弯矩可减小支座位移，桥墩位移延性需求随桥台背墙屈服弯矩增加呈现先逐渐增加再趋于稳定的趋势，桥台单桩弯矩呈现逐渐增加的趋势；减小伸缩缝间隙的大小可减小支座纵向位移，但可能会增大桥墩位移延性需求.

关键词:连续梁桥; 桥台; 背墙; 台后填土; 纵向地震响应

Abstract:

Based on the prototype of a continuous girder bridge with Ushaped seat abutment with pile foundation, effect of girderabutmentbackfill interaction on longitudinal seismic response of a continuous girder bridge was studied by nonlinear time history method. The effects of abutment backwall in flexural yield mode or abutment backwall bottom in shear failure mode on longitudinal seismic responses such as the longitudinal displacement of bearing, the displacement ductility demand of pier and bending moment of abutment pile were investigated. Furthermore, parameter analyses on the yield moment of abutment backwall, the expansion joint clearance at the abutment and height of pier were carried out. Results show that the longitudinal displacement of bearing, the displacement ductility demand of pier and the bending moment of abutment pile in the case of abutment backwall bottom in shear failure mode are less than those in the case of abutment backwall in flexural yield mode obviously. As the yield moment of abutment backwall increases, the longitudinal displacement of bearing decreases and the displacement ductility demand of pier increases gradually and becomes stable while the moment of abutment pile increases gradually. As expansion joint clearance decreases, the longitudinal displacement of bearing decreases, while the displacement ductility demand of pier might increase.

Key words:continuous girder bridge; abutment;backwall; backfill; longitudinal seismic response