【作者】 刘方成；

【导师】 尚守平；

【作者基本信息】 湖南大学 ， 结构工程， 2008， 博士

【摘要】 随着社会的发展、社会财富和人口的高度集中,地震灾害对人类社会所造成的损失越来越大。因此,基于性能的抗震设计日益得到重视,而这首先就要求对于结构的地震反应分析更为精确。正因为如此,广大研究者和工程技术人员在实践中越来越意识到将上部结构和基础考虑作为一相互作用的整体来进行设计的必要性和优越性。在土—结构动力相互作用问题中,土体的强烈非线性特性及其影响是其中的核心之一。而基于相互作用的机理进行上部结构的隔振研究是这个研究方向上的创新性思路,也是又一项具有工程实践意义的研究课题。本文围绕地基土体的非线性动力特性及其合适的本构模型构建这一问题开展工作,着重考察了地基土体非线性动力特性的变化规律及影响因素、土体非线性对于自由场和土—结构体系地震动力反应的影响及其机理。同时,在这其中通过试验研究了土—结构界面接触非线性特性、土—结构体系上下部刚度比变化对SSI效应的影响等问题,为相互作用问题的理论分析和实践应用提供参考。最后,根据相互作用机理分析的启示,提出了坚硬场地上刚性结构基底软土夹层隔震思路。全文的主要工作和创新如下:1.广泛阅读本领域的相关文献,总结了国内外开展土—结构动力相互作用研究的现状及其发展水平,评述了已有研究工作成果的局限性及优缺点,提出了本文针对土—结构动力相互作用问题研究的思路。2.对地基土体的非线性动力特性进行试验研究。通过对粉质黏土的循环单剪试验,研究了土体的应变累积特性以及土体加载历史、场地固结压力对于土非线性动剪模量和阻尼比的影响。试验验证了由小到大的分级循环加载试验方法的可行性,同时,在试验现象机理分析的基础上提出了能够考虑加载历史和固结压力影响的黏土动力特性模型。3.提出了基于阻尼的土体真非线性滞回模型,并且将这一模型推广至弹塑性领域,建立了基于阻尼的土体边界面模型。通过循环单剪试验,验证了所提本构模型的可行性与优越性。4.开发了自由场地震反应非线性分析程序。该程序应用自主提出的土动力特性模型和土体动力滞回本构模型,对自由场的非线性地震反应问题进行了深入分析,考察了自由场地底部边界条件、土体本构模型、土动力特性以及软弱夹层等因素对自由场非线性反应的影响。5.对粉质黏土与混凝土界面的界面接触力学性能进行试验研究,考查了界面粗糙度、界面法向压力、薄层单元厚度、加载形式等因素对界面单元应力应变关系的影响。根据试验结果,提出了改进的薄层界面接触单元本构模型。6.针对上下部结构刚度比对土—结构动力相互作用效应的影响这一问题进行了大比例模型试验,根据试验结果,对规范中关于考虑SSI效应的结构附加周期的确定提出了有益的建议。7.在通用有限元软件MSC.Marc中建立整体有限元模型,应用自主提出的基于阻尼的边界面本构模型和改进的土—结构界面本构模型,深入分析了土体非线性对结构地震反应的影响及其机理。针对一具体场地,考察了土体非线性对结构地震反应谱的影响。8.提出了较坚硬场地上刚性结构的基底软土夹层隔震思想,通过实例研究了软土夹层隔震的效果及其影响因素。最后,对人工软土材料的研究提出了建议与展望。更多还原

【Abstract】 Along with the development of the human society, and with the centralizing of fortune and population ,the damage caused by earthquake disaster to our society goes up greatly, and so, the importance of performance based seismic design has been more widely recognized. Performance based design requires, however, more accurate analyses, including all potential important factors, in order to predict the expected level of damage associated with a given level of earthquake. Just because of this, the majority of researchers and technical staff working in practice have recongnized the the necessity and advantages to design the structures based on the analysis with the soil-foundation-upper structure considered in an overall system. In the soil-structure interaction system, the strong non-linear soil characteristics and their impact on SSI is one of the core problems. And in further, the idea of isolating the upper structures based on the SSI mechanism is an innovative idea, which deserves significant practical studying.This article focuses on the nonlinear dynamic characteristics of field soils as well as its suitable constitutive model. Keystones of the research are soil nonlinear dynamic properties and its impact factors, impact of non-linear soil behavior on both free field seismic reponse and the soil - structure system dynamic response during earthquakes and the mechanism of these impacts. Around these focuses, experiments are adopted to study the features of the soil-structure interface behavior and the impact of relative rigidity of the upper structure and the foundation on the SSI effect of soil-structure system, for the purpose of providing reference for both further theory research and practical applications. Finally, according to the inspiration of SSI analysis, the idea of isolating the upper structure with artifical soft interlayer between the shallow foundation of the rigid upper structure and the relative rigid field is advanced. The main work and innovation of this text are as follows:1. With the summarization of lots of interrelated references, the studying actuality and developing level which about soil-structure interaction are presented. The limitations、advantages and disadvantages existing in present researches are discussed too. Then the basic theory way and analyzing frame route related to soil structure interaction in this paper is introduced.2. With the use of cyclic simple shear testing, the nonlinear dynamic properties of a certain kind of silty clay are probed. The feasibility of graded cyclic loading test method with the loading amplitude increase gradully on a soil specimen to get the dynamic properties of soil is validated by the experimental research. Also the effect of accumulated volume strains which caused by the cyclic loading history on the dynamic properties of soil and the effects of consolidation pressure which usually caused by the deadweight of the field soil on the dynamic properties of soil are researched respectively, and accordingly an accumulative strain strengthened dynamic model and an consolidation pressure relative dynamic model are brought out in the further study.3. A new damping based real nonlinear hysteretic model is advised, and further this model is extended into the elasto-plastic domain so that a damping based boundary model is constituted. With the Comparation of the model numerical realization and the cyclic simple shear testing results of a real soil, it is proved that the soil nonlinear model carried out in this paper is ascendant and proper.4. A new free field seimic reponse analysis program is build up, and then with the application of the dynamic property model and constitutive model advised previously, the effect of soil nonlinear behavior on the free field seismic response is researched, in which the influence of a series factors such as the bottom boundary condition, soil constitutive model, and the existing of soft interlayer, etc, on the free field seismic reponse is dicussed.5. A series cyclic simple shear tests aimed to discuss the nonlinear shear stress-strain relations of the interface between a silty clay and concrete are carried out. In these tests, several factors which may have effects on the interface behavior are investigated, such as the roughness of the interface, the vertical pressure on the interface, the thickness of the soil specimen beside the interface, and the shearing with unilateral or bidirectional loading. Based on the test result, a modified constitutive model for the finit thickness thin intereface element is suggested.6. Large scale model experiments are carried out in order to survey the effects of rigidity ratio between the upper structure and the foundational structure on the soil-structure interaction effects for the fisrt time. Based on the experimental reslults, benificial suggestion is brought forward for the code on how to decide the additional period of structure as the SSI effects taking in considerated.7. With proper finit element model of the SSI system builded up in the general software MSC.Marc, and with the use of the damping based boundary soil contstitutive model and the modified finit thickness thin interface elemental constitutive model, the effects of soil nonlinear behavior on the structural seismic response as well as the mechanisms of these effects are analized to a deep extend, and the structural response spectrum with the soil nonlinearity in consideration is carried out for the purpose of practical application.8. An innovate idea that using the soft interlayer between the rigid field and rigid shallow foundation as the base isolation material is brought out, and analysis case is carried out to validate the isolation effects of soft interlayer as well as the impact of some factors on the isolation effects. Lastly, advice and prospect on the artifical soft soil research is given.更多还原