不同桩基模拟方法对液化场地桥梁地震响应的影响

祝兵+王冲冲+王晶

摘要：为了考察桩土相互作用以及桩基土液化对桥梁结构地震响应的影响，针对处于可液化场地的某座铁路三跨预应力连续梁拱组合桥，利用ANSYS有限元计算软件建立墩底固结模型Ⅰ及基于m值法和PY曲线法的全桩模型Ⅱ和模型Ⅲ，并对各模型进行振动特性计算分析和时程计算分析。结果表明：3个有限元模型的基本振型相同，均为面外横向侧弯；全桩模型Ⅱ和模型Ⅲ前5阶振型分布特点一致，验证了模型对比分析方式和PY曲线法的合理性；模型Ⅰ，Ⅱ，Ⅲ的一阶频率分别为0.836 69，0.518 95，0.502 78 Hz，拱顶横向位移时程计算值分别为0.005 13，0.020 3，0.022 1 m；考虑桩土相互作用及液化土非线性后，结构关键位置位移响应值进一步增大；所得结论可为今后可液化场地的桥梁进行抗震分析提供参考。

关键词：桥梁抗震；地震响应；PY曲线法；梁拱组合桥；时程计算；液化场地

中图分类号：U441文献标志码：A

Abstract： In order to investigate the influence of pilesoil interaction and pile foundation soil liquefaction on seismic response of bridge structure， model Ⅰ for the bottom of pier consolidation，whole pile model Ⅱ and model Ⅲ based on mvalue method and PY curve method for a railway bridge with threespan prestressed and continuous beamarch combination structure in liquefiable site were established by finite element analysis software ANSYS. The vibration characteristics and time history of models were calculated. The results show that the basic modes of the three finite element models are same， and lateral bending is the basic mode of the bridge. The whole pile model Ⅱ and model Ⅲ have the same first 5 modes， which shows that the model analysis of contrast method and application of PY curve method were reasonable. The first order frequencies of model Ⅰ， Ⅱ and Ⅲ were 0.836 69， 0.518 95， 0.502 78 Hz. The calculation values of lateral displacement of vault were 0.005 13， 0.020 3， 0.022 1 m. The displacement response values of key locations of structure increase while considering the pileliquefied soil interaction and liquefied soil nonlinear. The method can provide a reference for the analysis of bridge seismic liquefiable ground in the future.

Key words： bridge seismic； seismic response； PY curve method； beamarch composite bridge； time history calculation； liquefied site

0引言

震害调查数据表明，场地液化是桥梁及房屋等建筑物震害的主要原因之一[13]。因此，如何准确模拟液化场地桩土相互作用、液化土的本构关系及液化土强度弱化是桥梁地震响应分析计算的难点和重点。现在人们针对处在非液化场地桥梁抗震已做了大量的分析和研究工作，但对于处在液化场地的大跨度桥梁的抗震分析还未形成统一的认识。针对这一问题，各国普遍采用的方法是m值法和PY曲线法[410]。为了考察桩土相互作用及桩基土液化对结构地震响应的影响，本文针对处于可液化……