结构底面积对地基土—高层建筑相互作用地震反应影响分析

发布时间：2018-07-12 13:13

本文选题：土－结构相互作用 + 有限元方法　；参考：《天津大学》2013年博士论文

【摘要】：近年来随着施工技术的进步，新型建筑材料的出现，以及机械及计算机技术在建筑行业的广泛应用，高层建筑的发展具备了良好的物质基础和建设条件，建筑规模和建筑高度一直在不断增加。在建筑结构的设计中，结构抗震分析是一个重要的课题。然而将结构与基础分别独立设计的刚性基础假设方法，已经不能满足实际工程需要，随着现代抗震设计理论的逐步完善，地基土－高层结构动力相互作用的分析方法越来越多的应用到工程抗震分析中。在土－结构相互作用问题的研究中，地基的特性、结构的平面尺寸以及结构的基础埋深等，都对建筑地震反应有着不同程度的影响，可以通过对比分析，找出每种考虑因素对地震反应分析的影响规律，进一步完善土－结构相互作用理论成果。针对这一课题，论文运用数值方法进行了一系列的分析，主要的创新工作与成果有：（1）基于有限元分析方法建立了土－结构相互作用计算模型，选取15层框架结构为计算算例，设定三种不同底面积但周期相近的框架结构，进行地震反应时程分析，为了在三维模型中提高计算效率，使用超单元方法以节省计算时间。通过二维模型和三维弹塑性带桩基模型计算，取得了较为一致的结论，结果表明：由于结构的自振周期与结构的刚度和质量有关，当结构跨度、梁柱尺寸及单位质量相同时，不同底面积结构的自振周期基本相近；考虑相互作用之后，结构自振周期明显增大，此时体系的地震反应不仅与体系本身性质有关，还与土体对结构的约束力大小密切相关。（2）考虑土体与结构相互作用后，在同一种地震波作用下，结构顶层总位移较刚性基础顶层位移有所增大，且随着结构底面积的增大而减小，由基础转动引起的位移随着结构底面积的增大而明显减小，上部结构自身位移，在总位移中所占比例以及平均基底剪力随着底面积的增加而增大。三种不同底面积相互作用体系上部结构的层间位移曲线则有较大差别，上部结构的层间位移峰值小于刚性基础结构的层间位移峰值。土体刚度越大，相互作用影响效果越小，上部结构顶层的位移反应峰值也越小，结构的转动位移和平动位移数值减小。比较不同特性的地震波，不同底面积结构顶层总位移、基础转动、基础平动、结构自身位移和内力的变化规律趋势相同。（3）同一种平面尺寸，结构顶层总位移随着基础埋深的增大而减小，上部结构位移在总位移中所占比例以及平均基底剪力均随着基础埋深的增加而增大。与增加底面积的模型相比较，增加结构基础埋深，对减小结构顶层总位移，，特别是减小基础转动的效果更为显著。在不同的地震波作用下，考虑相互作用之后，不同埋置深度结构的最大层间位移变化曲线形状基本一致。层间位移峰值均发生在结构第三、四层附近，且基础埋深最大的结构层间位移峰值最大，但均小于刚性基础时的最大层间位移角值。（4）为了进一步考察在一般情况下改变底面积对土－结构相互作用地震反应的影响，基于抗震设计中反应谱理论，探讨底面积对土－结构相互作用地震反应谱的影响。针对不同场地条件选取一定数量的地震波，建立土－结构整体弹性体系三维数值分析模型进行动力分析，求得上部结构与土体之间交界面上的耦合作用，将此耦合作用与原地震波叠加后，得到上部结构实际受到的考虑了相互作用之后的地震波作用，即为修正地震波，并绘出此修正地震波的反应谱曲线并求得平均值。对影响修正地震波反应谱曲线变化的各种因素进行定性的分析，得出一些规律性结论：由于原地震波特性不同，场地土对原地震波的吸收与放大程度均不相同，但所得修正地震波加速度峰值均有不同程度的减小，且修正地震波平均反应谱曲线峰值也较原地震波减小；结构底面积越大，结构受到土体的约束力越大，修正地震波反应谱曲线峰值越小；同一底面积结构，土体越软，土－结构相互作用效果越显著，修正地震波反应谱曲线的峰值越小。
[Abstract]:In recent years, with the progress of construction technology, the emergence of new building materials, and the extensive application of mechanical and computer technology in the construction industry, the development of high building has a good material base and construction conditions. The scale and height of the building have been increasing continuously. In the design of the building structure, the seismic analysis of the structure is a However, the rigid foundation hypothesis method, which separately designs the structure and foundation separately, is unable to meet the actual engineering needs. With the gradual improvement of the modern seismic design theory, the analysis method of the dynamic interaction of the foundation soil and the high-rise structure is more and more applied to the seismic analysis of the engineering. The soil structure interaction is used. In the study of the problem, the characteristics of the foundation, the plane size of the structure and the foundation depth of the structure have different influence on the seismic response of the building. Through the comparative analysis, we can find out the influence laws of each factor on the seismic response analysis, and further improve the theoretical results of the soil structure interaction. A series of analyses have been carried out by using numerical methods. The main innovations and achievements are as follows:
(1) a calculation model of soil structure interaction is set up based on the finite element method. The 15 story frame structure is selected as the calculation example, and three kinds of frame structures with different bottom area but similar period are set, and the seismic response time history analysis is carried out. In order to improve the calculation efficiency in the three-dimensional model, the superelement method is used to save the calculation time. Through two, the calculation time is saved. The dimensional model and the three-dimensional elastoplastic belt pile foundation model are calculated. The results show that the vibration period of the structure is related to the stiffness and the mass of the structure. When the structure span, the beam column size and the unit mass are the same, the self vibration period of the different bottom area structure is almost similar. After considering the interaction, the structure is self excited. The cycle is obviously increased, and the seismic response of the system is not only related to the nature of the system itself, but also closely related to the binding force of the soil on the structure.
(2) under the interaction of soil and structure, under the action of the same seismic wave, the total displacement of the top layer of the structure is larger than that of the rigid base, and decreases with the increase of the bottom area of the structure. The displacement caused by the rotation of the foundation decreases with the increase of the base area of the structure, and the displacement of the superstructure is accounted for in the total displacement. The ratio and the average base shear increase with the increase of the bottom area. The interlayer displacement curves of the upper structure of the three different floor area interaction systems are different. The peak interlayer displacement of the superstructure is smaller than the peak displacement peak of the rigid base structure. The greater the soil stiffness, the smaller the effect of interaction, the top structure top. The displacement response peak of the layer is also smaller, the rotational displacement and the translational displacement of the structure decrease, and the different characteristics of the seismic waves, the total displacement of the top floor of different bottom area structure, the foundation rotation, the basic translational movement, the change of the structural self displacement and internal force are the same.
(3) in the same plane size, the total displacement of the top layer decreases with the increase of the foundation depth, the proportion of the displacement of the superstructure in the total displacement and the average base shear increase with the increase of the foundation buried depth. The effect of small foundation rotation is more remarkable. Under the action of different seismic waves, the maximum interlayer displacement curve shape of different buried depth structure is basically the same after considering the interaction. The peak value of interlayer displacement occurs near the third, fourth layer of structure, and the maximum interlayer displacement peak of the most basic buried depth is maximum, but all less than the rigidity. The maximum interlayer displacement angle of the base.
(4) in order to further investigate the influence of the bottom area on the seismic response of soil structure interaction in general conditions, based on the response spectrum theory in the seismic design, the effect of the bottom area on the seismic response spectrum of soil structure interaction is discussed. A certain number of seismic waves are selected for different site conditions, and the earth structure integral elastomer is established. A three-dimensional numerical analysis model is used to analyze the coupling effect on the interface between the superstructure and the soil. After the coupling action is superposed with the original seismic wave, the superstructure is actually subjected to the interaction of seismic waves, that is, to modify the seismic wave and to draw the response spectrum curve of the modified seismic wave. According to the qualitative analysis of various factors affecting the variation of the response spectrum curve of the seismic wave, some regular conclusions are obtained: the original seismic wave absorption and magnification degree are different because of the different characteristics of the original seismic waves, but the corrected seismic wave addition velocity peaks are reduced in varying degrees and modified. The peak of seismic wave average response spectrum curve is also smaller than that of the original seismic wave. The larger the structure bottom area is, the larger the structure is, the greater the binding force of the soil, the smaller the peak of the response spectrum curve of the corrected seismic wave. The more soft the soil body is, the more significant the soil structure interaction effect is, the smaller the peak of the correction of the response spectrum curve of the seismic wave.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU435;TU973.31

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