地震作用下复合地基-筏板-上部结构相互作用体系的动力弹塑性分析

基于复合地基-上部结构相互作用的静力分析已取得一定的研究成果，但其在动力荷载作用下，特别是地震作用下的动力响应却相当匮乏。首先借助有关试验通过ABAQUS和EERA的模拟分析，验证了基于Drucker-Prager屈服准则的弹塑性模型能较好地反映土体非线性动力特性以及采用有限元与无限元耦合的方法对土体无限边界的模拟。在此基础上，针对实际问题建立了刚性桩复合地基-筏板-上部结构体系整体有限元模型，对其进行动力弹塑性时程分析，并讨论了该复合地基与桩基对地震响应的差异。深入研究了不同强度地震作用下，刚性桩复合地基的工作机制，包括桩体、褥垫层、筏板的动力响应以及上部结构的地震反应和抗震性能。结果表明，小震时褥垫层基本没有减震效果，大震时复合地基的抗震性能优于桩基。地震越强烈，减震效果越明显，但作用有限，减震系数一般在0.8以上，可为工程实践提供参考。

Dynamic elastoplastic analysis of interaction system of composite foundation-raft-superstructure under earthquake action

Some results of static analysis considering the interaction between superstructure and composite foundation are obtained. However, the research on the response under dynamic loading, especially under earthquake loading, is very inadequate. Via relevant tests, ABAQUS are verified by comparison with EERA. The results show that the elastoplastic constitutive model based on Drucker-Prager yield criterion and the method of finite element and infinite element coupling can adequately simulate the nonlinear dynamic characteristics of soil and the infinite boundary. To the actual problem，the whole finite element model of rigid pile composite foundation-raft-superstructure system is established. And dynamic elastoplastic time-history analysis is made; the differences between rigid pile composite foundation and pile foundation in seismic response are analyzed. The seismic mechanism of rigid pile composite foundation, including the dynamic responses of piles, cushion and raft, is studied under different earthquake intensities; and the earthquake response and seismic performance of superstructure are analyzed deeply. It is shown that cushion has no damping effect almost under minor earthquake; rigid pile composite foundation is superior in seismic performance to pile foundation under major earthquake. The stronger earthquake is, the better damping effect is. But it is limited, the damping coefficient is over 0.8 generally. The results can provide references to engineering practice.