考虑土—结构动力相互作用的高台基木结构古建筑地震反应分析

发布时间：2018-06-16 12:00

本文选题：木结构古建筑 + 土—结构动力相互作用　；参考：《西安建筑科技大学》2017年硕士论文

【摘要】：中国木结构古建筑在世界古建筑体系中占有非常重要的地位,对其抗震性能进行分析和研究具有重大的历史与现实价值。长久以来,对于木结构古建筑的结构抗震分析采用的都是刚性地基假定,在进行计算时仅仅考虑了上部结构,将自由场地表反应作为地震动输入结构。虽然这种方法易于处理,模型简单,计算方便,但是这种模型计算出的地震反应与实际结构的地震反应有一定的差别。本文以西安东门箭楼为背景,采用ANSYS的APDL语言建立四种不同的计算分析模型,并对四种模型进行了模态分析及动力时程分析,总结土—结构动力相互作用对上部木结构的动力特性、变形特性及结构内力反应的影响。介绍了土—结构动力相互作用的概念,对近年来土—结构动力相互作用的研究成果进行了总结。建立了均匀半空间水平成层土壤的一维理想化模型,在一维重复波动理论的基础上,利用SHAKE91程序进行自由场地震动反演分析,得到了下部土体各层的加速度、应力、应变时程,结果表明基岩处的地震动传播到地表时其波型变化不大但是幅值有较大的增加,地震波的高频成分减少而低频成分变得更加丰富,说明土体对地震波具有滤波和放大作用。通常情况下对加速度波形进行连续积分即可得到速度时程和位移时程,但事实上在直接积分时会出现位移基线漂移的现象,根据最小二乘速度时域校正法基本原理编制Fortran程序对速度和位移时程曲线进行调整,得到了比较满意的结果。建立了西安东门箭楼的四种计算分析模型,并对模型进行模态分析、反应谱分析及动力时程分析。模态分析结果表明,考虑土—结构动力相互作用后,结构的自振频率和振型与刚性地基假定的情况下相比都发生了很大的改变,结构的自振频率出现了不同程度的降低,结构某些振型的出现顺序也发生了一定的改变。反应谱分析及动力时程分析结果表明,考虑土—结构动力相互作用后,刚性基底整体模型得到的上部结构各层的绝对加速度、相对柱脚位移及各层的剪力都较刚性地基情况下有较大的增大;考虑基底的柔性后,上部结构的加速度较刚性基底情况下略有下降,且在Taft波和Lanzhou波激励下其依然大于刚性地基模型,而相对柱脚位移和各层剪力均在刚性基底模型的基础上又有所增大。分析及计算的结果表明,对于高台基木结构古建筑,上部木结构、台基、台基下部土体是一个统一的整体,三者之间相互影响。在进行地震反应分析时,必须考虑土—结构动力相互作用的影响,并选择合适的地震动输入方式,以确保分析结果的正确性。
[Abstract]:The ancient Chinese wooden architecture plays an important role in the world ancient building system. It is of great historical and practical value to analyze and study its seismic performance. For a long time, the structural seismic analysis of wooden structures is based on the assumption of rigid foundation. In the calculation, only the superstructure is considered, and the surface response of the free site is regarded as the input structure of the ground motion. Although this method is easy to deal with, the model is simple and the calculation is convenient, the seismic response calculated by this model is different from that of the actual structure. In this paper, taking the Dongmen Arrow House of Xi'an as the background, the APDL language of ANSYS is used to establish four different calculation and analysis models, and the modal analysis and dynamic time history analysis of the four models are carried out. The influence of soil-structure dynamic interaction on the dynamic characteristics, deformation characteristics and internal force response of upper wood structures is summarized. This paper introduces the concept of soil-structure dynamic interaction and summarizes the research results of soil-structure dynamic interaction in recent years. A one-dimensional idealized model of horizontal stratified soil in homogeneous half-space is established. Based on the one-dimensional repeated wave theory, the free site vibration inversion analysis is carried out by using SHAKE91 program, and the acceleration, stress and strain time history of each layer of the lower soil is obtained. The results show that the wave pattern of the ground motion propagates to the ground surface is not changed much, but the amplitude is increased, the high frequency component of the seismic wave decreases and the low frequency component becomes more abundant, which indicates that the soil has the function of filtering and amplifying the seismic wave. In general, velocity time history and displacement time history can be obtained by continuous integration of acceleration waveform, but in fact displacement baseline drift will occur in direct integration. According to the basic principle of the least square velocity time domain correction method, Fortran program is compiled to adjust the velocity and displacement time history curves, and satisfactory results are obtained. Four kinds of calculation and analysis models of Dongmen Arrow in Xi'an are established, and modal analysis, response spectrum analysis and dynamic time history analysis are carried out. The modal analysis results show that the natural vibration frequency and vibration mode of the structure have changed greatly compared with the assumption of rigid foundation after considering the soil-structure dynamic interaction, and the natural vibration frequency of the structure has been reduced in varying degrees. The appearance sequence of some vibration modes of the structure has also changed to a certain extent. The results of response spectrum analysis and dynamic time history analysis show that considering the soil-structure dynamic interaction, the absolute acceleration of each layer of the superstructure can be obtained by the rigid basement integral model. The relative displacement of column foot and shear force of each layer are larger than that of rigid foundation, and the acceleration of superstructure decreases slightly when considering the flexibility of base. Under the excitation of Taft wave and Lanzhou wave, it is still larger than the rigid foundation model, and the relative displacement of column foot and shear force of each layer are increased on the basis of rigid foundation model. The results of analysis and calculation show that the upper wood structure and the lower soil mass of the platform foundation are a unified whole for the ancient building with high platform foundation and the three factors interact with each other. In seismic response analysis, the influence of soil-structure dynamic interaction must be taken into account, and the appropriate input mode of ground motion should be chosen to ensure the correctness of the analysis results.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU366.2

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