【作者】 王汝恒；

【导师】 邓安福；

【作者基本信息】 重庆大学 ， 岩土工程， 2009， 博士

【摘要】 巨型框架结构-筏基-砂卵石地基作为一种新型的大型结构体系随着经济与城市化建设的发展而逐渐开始应用。巨型框架建筑体系复杂,上部结构、基础及地基是统一的整体,三者相互联系、相互影响,共同作用,若仍沿用传统的刚性基础假定设计巨型框架结构,而不考虑建筑物共同作用影响则不甚合理,且将与实际结构的力学特性有较大的出入,其共同作用己是许多重大实际工程中一个不可回避的关键科学问题。鉴于此,本论文针对某典型巨型框架结构体系开展深入、细致分析,对其进行静、动荷载作用下的共同作用特性研究。本文基于国内外目前共同作用研究发展的趋势,在充分借鉴并发挥前人研究的基础上,采用理论分析、土工试验、数值模拟相结合的方法,围绕巨型框架上部结构-筏基-砂卵石地基共同作用的机理、影响因素及计算模型展开了系统研究。本文主要研究内容及创新点如下:(1)进行砂卵石土静动力特性研究和砂卵石土地基计算模型的研究。通过砂卵石土三轴固结排水剪切试验,分析砂卵石土的体变规律,通过砂卵石土动三轴试验,分析固结压力、固结应力比、振动频率对动本构关系、动弹性模量与动阻尼比的影响规律。其中,进行邓肯-张模型对砂卵石土的适用性分析,建议采用双线型关系表达泊松比;建立了砂卵石土最大动弹性模量与最大阻尼比计算的数值方程;对文克尔地基模型进行改进,确定了砂卵石土地基模型计算的数值参数。(2)进行砂卵石土地基上的筏基计算研究。分析了薄板小挠度理论建立的地基上的板的基本方程与文克尔地基上正交各向异性板的有限元法,针对薄板理论、中厚板理论、空间弹性理论,建立三种筏板计算数值模型并进行共同作用数值计算,对比分析不同计算理论对筏板变形与内力的影响,提出采用各计算理论的应用条件。(3)进行砂卵石土地基与筏基共同作用的非线性研究。对砂卵石土地基、筏板的钢筋混凝土材料及两者接触的非线性进行了理论分析,通过ANSYS算例数值分析,对比各部位采用非线性计算的结果特征,表明在共同作用分析中最好同时考虑地基与基础两者的非线性,而简化分析过程,应首先考虑地基土的非线性。(4)巨型框架结构-筏基-砂卵石地基的静力共同作用数值分析。建立了在竖向静力荷载下的共同作用数值模型,分析共同作用中的巨型框架结构响应特性,以地基条件、筏板厚度、筏板计算理论、次框架结构等方面进行静力共同作用影响分析。其中,提出底部次框架结构可改善基础不均匀沉降的作用机理;提出共同作用中的筏板基础存在一个最佳厚度;阐述了地基刚度增加使得共同作用效果愈加不显著的结论,而且地基整体变形决定基础的沉降,局部变形决定筏板的应力分布。(5)巨型框架结构-筏基-砂卵石地基的动力相互作用数值分析。对地基地震波的有限元计算范围及边界截取进行分析,依据人工边界的数值模拟,确定粘弹性边界计算精度与计算区域,同时进行上部巨型框架结构计算简化模型研究,通过地震作用上部结构数值计算分析了次框架对巨型框架结构动态响应的影响。通过地震作用下巨型框架结构-筏基-砂卵石地基的相互作用数值计算,进行结构动力相互共同机理分析。其中,提出次框架的刚度增大效应与相互作用中的上部结构刚度减小效果相当的结论;提出相互作用中薄基础对上部结构顶层不利,而结构底部的动态响应受地基或基础的影响比较大的结论。更多还原

【Abstract】 Mega-frame structure is a new type of large-scale structure, and gradually begins to be widely used as the urbanization and economic development. For Mega-frame structure has the character of complex system, if it is built depended on the hypothesis of rigid foundation without regard to the interaction of superstructure and base, the result will be unreasonable and cause a big discrepancy between calculation and reality. Superstructure, base and foundation are an organic whole which connect and influence each other. And the interaction of Mega-frame structure becomes an unavoidable key scientific question in some important real projects. So, the paper’s aim at only one kind of mega-frame structure and research on static and dynamic interaction carefully.Based on the developing trends of the interaction research,the paper used theoretical analysis, soil tests and numerical simulation to study the interaction of the mega frame structure - based raft - sand gravel foundation. The main works and conclusions in this paper are as follows:(1) Static and dynamic characteristics of sand gravel are analyzed and the numerical model of foundation is researched. Based on the results of consolidated and drained triaxial shear tests, the transmogrification of sand gravel is studied. Based on the dynamic triaxial tests, the rule about the dynamic characters of sandy gravel soil under different confining pressure, solidify ratio and vibration frequency are analyzed. Among these work, the conclusion that the strength and elastic modulus of sand gravel can use Duncan-Chang Model to calculate, but the transmutation and poisson ratio need crewel model to determine are innovative. The numerical equation about the maximum dynamic modulus and the maximum poisson ratio are also innovative. Finally, the soil medel of Wrinkler are improved and the numerical parameters are gained.(2) The calculated method about raft foundation on sand gravel is investigated. The equation of raft based on the theory about elastic thin plate and the finite element method of orthotropic plate for Wrinkler is analyzed. Base on the thin plate theory, the moderately-thick plate theory and the space elastic theory, three numerical models about raft are calculated. After the deformation and internal force of raft under different theory are compared and analyzed, the conditions for the application of theoretical calculations are innovative.(3) The nonlinear analysis about raft foundation and sand gravel interaction are researched. The elastic-plastic characteristic of sand gravel, reinforced concrete raft foundation and the contact nonlinear are analyzed. The nonlinear numerical calculation are performed, the nonlinear characteristic about three parts will change the result of calculation. So the analysis about raft foundation and sand gravel interaction would adopt nonlinear calculation, and the priority is given to the nonlinear characteristic of sand gravel in the simplify process.(4) The static interaction of Mega frame-raft foundation-sand gravel soil is analyzed by numerical calculation. After the numerical model about the mega-frame structure considering the vertical static load under interaction are calculated, the response about mega-frame under interaction are analyzed, and the characteristic of interaction are researched by soil foundation, thickness of raft, theoretical calculation about raft, hypo-frame and others. Among these work, the innovative conclusions in this paper are as follows: the hypo-frame at the bottom of mega-frame structure adjust the uneven settlement of foundation; the raft foundation has a best thickness to be felicitous; the stiffness soil will weaken interaction when the foundation increase its thickness; the whole deformation of foundation aroused the settlement of raft and the local deformation determined the stress distribution of raft.(5) The dynamic interaction of mega frame-raft foundation-sand gravel soil is analyzed by numerical calculation. The area and boundary truncation of foundation under earthquake waves are researched by the finite element method. The calculation model about the upper part of the mega-frame structure is researched, and the hypo-frame can change the dynamic response of mega-frame structure based on the numerical calculation of mega-frame structure under earthquake. Finally the dynamic interaction are analyzed by numerical calculation. Among these work, the innovative conclusions in this paper are as follows: the increasing stiffness by hypo-frame is quite to the reducing stiffness by interaction; the raft foundation which are thin will be disadvantage to the top parts of structures; the soil foundation and raft foundation has nonnegligible influences on the dynamic response about the bottom of structures.更多还原