可液化河谷场地不同形式梁式桥的地震反应

Seismic Response of Girder Bridges in Liquefiable River Valleys with Different Structural Configurations

摘要:

场地液化对河谷场地中不同结构体系、不同基础形式的梁式桥的地震反应可能具有不同程度的影响.针对该问题，以典型可液化河谷场地三跨梁式桥为背景，建立了二维场地桥梁结构一体化有限元模型，包括群桩基础简支梁桥、群桩基础连续梁桥和桩柱式基础简支梁桥3种桥型，并进行非线性地震反应分析.从场地和桥梁震后变形、桩基础变形分布、桥墩漂移率、滑动支座位移和桥台伸缩缝位移等方面，探究不同形式梁桥的地震反应规律，重点揭示场地液化对不同形式梁式桥地震反应的影响规律.结果表明：场地液化会显著增大群桩基础简支梁桥的落梁风险，群桩基础连续梁桥受场地液化的影响次之，桥台处的落梁、台梁碰撞风险也较大，而桩柱式基础简支梁桥受场地液化的影响较小.

关键词:桥梁工程; 液化; 地震反应规律; 有限元方法; 中小跨径梁桥

Abstract:

Seismic responses of girder bridges may vary due to different structural systems and foundation types. In this regard, based on typical threespan girder bridges in liquefiable river valleys, three 2dimensional finite element models considering soilstructure interaction were built, including simply supported girder bridge with pile group foundations, continuous girder bridge with pile group foundations, and simply supported girder bridge with pileshaft foundations. Nonlinear time history analyses were performed to investigate the seismic response properties of these bridges. Postearthquake deformations of the soil and bridge, pile deformations, column drift ratios, bearing displacements, and expansion joint deformations were investigated to reveal the impact of soil liquefaction on seismic responses of these three types of bridges. The numerical results show that soil liquefaction significantly increases the unseating potential of the simply supported girder bridge with pile group foundations. For abutments of continuous girder bridge, unseating or abutmentdeck collision potentials are generally increased. In contrast, seismic responses of the simply supported girder bridge with pileshaft foundations are rarely influenced by soil liquefaction.

Key words:bridge engineering; liquefaction; seismic demand property; finite element model; small and medium span girder bridge