基于真非线性分析的软弱层场地地震效应研究

发布时间：2018-05-03 13:24

本文选题：软弱层 + 土层特性　；参考：《湖南工业大学》2017年硕士论文

【摘要】：含有软弱层的场地是我国沿海地区常见的一种场地类型,其作为一种特殊场地一直是地震工程学领域研究的重点,已有的地震灾害调查及场地分析均表明土体结构中软弱层的存在对场地地震效应有着不可忽略的影响,所以对含软弱层的场地进行地震效应分析,无疑对结构抗震设计具有重要意义。本文采用尚守平等提出的基于阻尼的滞回模型,应用一维真非线性场地反应分析方法,对含有软弱层的场地展开分析,主要研究了软弱层的埋深、厚度、剪切波速、阻尼比和动剪模量比这5种因素变化对场地峰值加速度和场地反应谱的影响规律。研究结果表明:1、软弱层的存在使得场地加速度峰值发生突变,随着软弱层埋深、厚度、剪切波速、阻尼比和动剪模量比的不同,这种突变可能使得地面峰值加速度增大或减小。对于给定的软弱层埋深、厚度、剪切波速、阻尼比和动剪模量比,随输入地震动幅值的增大,地面峰值加速度增大,加速度效应系数没有明显规律;对于给定的地震动,地面峰值加速度随软弱层埋深、厚度的增大而减小,随剪切波速的增大而增大,随阻尼比和动剪模量比的依次变化在增大,由此表明深厚的软弱层对场地具有显著的减震作用,其埋深越深,厚度越大,剪切波速越小,减震效果越明显。2、软弱层的存在使得场地反应谱特征周期延长,长周期段曲线升高并出现多峰值现象,有无软弱层的场地反应谱差值比远大于工程可接受的误差范围20%,且在本文算例中,最大反应谱差值比已达到18.0倍;软弱层所引起的场地反应谱差值比曲线随结构周期的增大先升高后降低,存在一个对应着最大反应谱差值比的特征周期;软弱层的埋深、厚度、剪切波速、阻尼比和动剪模量比是决定软弱层对场地反应谱强烈程度的主要因素,而输入的地震波特性与地震动幅值对含软弱层场地的反应谱的影响规律则不明显。
[Abstract]:The site containing weak layer is a common site type in coastal areas of China. As a special site, it has always been the focus of research in the field of seismic engineering. The existing seismic disaster investigation and site analysis show that the existence of weak layer in soil structure has an important influence on site seismic effect, so the seismic effect of site with weak layer is analyzed. Undoubtedly, it is of great significance to the seismic design of structures. In this paper, the hysteretic model based on damping proposed by Shang Shouping and the method of one-dimensional true nonlinear site response analysis are used to analyze the site with weak layer. The buried depth, thickness and shear wave velocity of weak layer are studied. The effects of damping ratio and dynamic shear modulus ratio on the peak acceleration and site response spectrum are investigated. The results show that the existence of weak layer makes the ground acceleration peak change. With the difference of buried depth, thickness, shear wave velocity, damping ratio and dynamic shear modulus ratio, this sudden change may increase or decrease the peak acceleration of the ground. For a given depth, thickness, shear wave velocity, damping ratio and dynamic shear modulus ratio, the peak acceleration of the ground increases with the increase of the amplitude of the input ground motion, and the acceleration effect coefficient is not obvious. The peak acceleration decreases with the depth and thickness of the soft layer, increases with the increase of shear wave velocity, and increases with the change of damping ratio and dynamic shear modulus ratio. The deeper the depth, the greater the thickness, the smaller the velocity of shear wave, the more obvious the seismic absorption effect is. The existence of weak layer makes the characteristic period of site response spectrum longer, the curve of long period increases and the phenomenon of multi-peak value appears. The difference ratio of site response spectrum with or without weak layer is much larger than that of engineering acceptable error range of 20, and the maximum response spectrum difference ratio has reached 18.0 times in the example in this paper. The difference ratio curve of site response spectrum caused by weak layer increases first and then decreases with the increase of structural period, and there exists a characteristic period corresponding to the maximum difference ratio of response spectrum, the buried depth, thickness, shear wave velocity of weak layer, The damping ratio and the dynamic shear modulus ratio are the main factors that determine the strong degree of the response spectrum of the weak layer to the site, but the influence of the input seismic wave characteristics and the amplitude of the ground motion on the response spectrum of the site containing the weak layer is not obvious.
【学位授予单位】：湖南工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU435

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