【作者】 袁景；

【导师】 刘海卿；

【作者基本信息】 辽宁工程技术大学 ， 岩土工程， 2013， 博士

【摘要】 钢筋混凝土框架结构的抗震研究大多采用刚性地基假定，没有充分考虑土层对地震波的过滤和放大效应，同时对上部结构的地震反应分析主要集中在弹塑性变形阶段，真正实现对结构发生破坏以后的研究较少，因此进行考虑土-结构相互作用的钢筋混凝土框架结构倒塌破坏分析和研究具有一定的重要性和实际意义。本文通过对大量相关文献的概括总结，评述了国内外对钢筋混凝土框架结构倒塌研究的现状与发展水平，对结构地震反应分析的数值方法进行归纳总结，基于结构抗震理论确定了动力相互作用体系的分析模型。在研究土体材料和钢筋混凝土材料本构模型的基础上，确定适合土-结构动力相互作用体系地震倒塌分析的材料本构模型，特别是在钢筋混凝土材料模型中引入损伤破坏限值，利用LS-DYNA软件中的Mat_Concrete_Damage材料模型及Erosion算法，以综合考虑混凝土材料的损伤软化、应变率效应、断裂失效等多种特性，模拟钢筋混凝土材料在地震作用下的破坏情况。通过阅读大量文献，确定出适合于倒塌破坏研究的各种材料模型参数。建立土-结构动力相互作用体系的有限元分析方案。通过合理的选取单元，输入地震动参数及考虑重力等因素的影响，建立了刚性地基及考虑土-结构动力相互作用的钢筋混凝土框架结构三维动力有限元分析模型。利用仿真程序模拟得到的裂缝分布及破坏过程与振动台试验的结果十分吻合，证明用LS-DYNA软件对钢筋混凝土框架结构进行倒塌破坏研究是可行的。通过对刚性地基条件与考虑土-结构相互作用两种情况下框架结构从变形、开裂直至最终倒塌的全过程进行对比分析，得出如下主要结论：（1）刚性地基条件下五层、十层、十五层框架结构的各个楼层加速度峰值在不同刚度条件下沿高度的变化趋势大致相同。顶层加速度峰值随结构刚度的增大而增大，结构的层数越多，顶层加速度峰值相对地面的放大系数越大；（2）刚性地基条件下结构首个破坏点出现的时间随刚度的增大有所延迟。在相同刚度条件下，层数越多结构破坏越快。五层框架结构的初始破坏点均出现在底层边框架的梁底柱边，十层和十五层框架结构的首个破坏点则出现在结构的上部楼层，这主要是由于结构高振型的影响；（3）土-结构动力相互作用体系的自振频率低于刚性地基时结构的自振频率，且硬土地基时体系的自振频率高于软土地基。相对于刚性地基条件，水平加速度峰值沿楼层的变化更加均匀，加速度峰值在大多数楼层有所折减，但在十层和十五层框架结构中个别楼层也出现了折减系数大于1的情况，因而刚性地基假定下结构的抗震设计并不一定安全；（4）土-结构相互作用体系相比刚性地基出现破坏点的时间有所延迟，同时硬土地基条件下的多数结构破坏点出现的时间早于软土地基，说明软土地基时相互作用的效果比较明显。上部结构的初始破坏位置均出现在框架底层的梁底柱边，与刚性地基的情况不完全一致。裂缝情况与刚性地基时相比发展的要少一些，同时体系在输入地震波后，发生了整体沉降的现象，在软土地基条件下沉降更为严重；（5）在地震作用下所有模型结构的各层梁柱交替发生破坏，属于混合倒塌机制。下部楼层破坏较为严重，这主要是由于下部结构承受了相对较大的重力荷载。同时随着刚度的增大，结构底部的破坏范围向上层逐渐扩大。这是因为强震作用下刚度较小的结构下部楼层发生破坏的时刻较早，而结构下部的破坏消耗了一部分地震能，减缓了地震对上部结构的作用。更多还原

【Abstract】 Rigid foundation assumption is adopted usually in current structural collapse damage study,which ignores the impact of filter and amplification effect by soil to the seismic responsecharacteristics and collapse process of superstructure. And seismic response analysis of framestructures direct at elastic-plastic deformation stage, the research of structure collapse damage isless. So the study of reinforced concrete frame structure collapse considering soil-structureinteraction is importance and practical significance.Through describing lots of related literatures, present situation of reinforcedconcrete frame structure collapse research and its developing level at home and abroadhave been elaborated. Summarizing numerical methods of structural seismic responseanalysis and basing on seismic theory, analytical mode of soil-structure interactionsystem is determined. The constitutive models of soils and structure material aredetermined and damage limit is introduced in reinforced concrete material model. TheMat_Concrete_Damage model and erosion technique which incorporate most of concretedynamic characteristics such as strain rate effect, damage accumulation, fracture failure,etc., are suitable to simulate the damage state of reinforced concrete under earthquake.And the precise parameters are obtained based on the test results of other researchersthrough reading related references.The finite element analysis solution is modified for the soil-structure dynamic interactionsystem. Three-dimensional dynamic finite element analysis model of frame structures on rigidfoundation and soil-structure interaction system are established by selecting the type of the finiteelement, the means of input of the earthquake wave and the gravity load of system. Thesimulation analysis of frame structural’s crack distribution and failure state is similar to the testresults of vibration table. It shows that the LS-DYNA software is viable to study the damage ofreinforced concrete frame structures. Based on comparative analysis of the process fromdeformation, crack until collapse on rigid foundation and considering soil-structure interaction,the main conclusions are obtained as follows:(1) The variation tendency of floor peak acceleration of five layer, ten layer and fifteenlayer frame structures on rigid foundation are similar. The top peak acceleration increases with the increase of structure stiffness. The more the number of layer, the greater the amplificationfactor of top peak acceleration to the ground acceleration.(2) The first breakdown point of frame on rigid foundation appears later with increase ofstructure stiffness. The more the number of layer, the earlier the first breakdown point of frameappears. The first breakdown point of five layer frame appears at beam bottom and post edge ofbottom edge framework, while that of ten and fifteen layer frames appear at the upper floor offrame. The reason is the influence of the structure of high vibration mode.(3) Natural frequency of vibration of soil-structure dynamic interaction system is lower thanthat of frame on rigid foundation, and which on hard soil is higher than on soft soil. The floorpeak acceleration is more even than that on rigid foundation. The floor peak acceleration is lesserthan which on rigid foundation at most frames, but reduction coefficients are greater than1atindividual floors of ten and fifteen layer frames. It indicates that structure seismic design basedon rigid foundation assumption is not always safe.(4) The first breakdown point of frame considering soil-structure dynamic interactionappears later than which on rigid foundation. The first breakdown point of frame on hard soilappears earlier than which on soft soil. It means that the effect of soil-structure dynamicinteraction on soft soil is more obvious. The first breakdown point of frame appears at beambottom and post edge of bottom framework considering soil-structure dynamic interaction. It isdifferent from frame on rigid foundation. And the cracks of superstructure are lesser than whichon rigid foundation. The whole settlement occurred in soil-structure dynamic interaction system,and the settlement in soft soil foundation is more serious than which in hard soil.(5) That beam and column on each layer of the model structures are destroyed alternately ismixed collapse mechanism. Damage of the lower floors is more serious, that is mainly due to thelower floors bear a relatively large gravity load. The damage range at the bottom of the structureexpands gradually when the rigidity of structure increases. The reason is that damage of thelower floors occurs earlier when rigidity of structure is low and seismic energy is consumed toreduce the affect of earthquake to the upper structure.更多还原