二维复杂场地土介质中阻尼的选取方法

发布时间：2017-12-30 20:33

本文关键词：二维复杂场地土介质中阻尼的选取方法　出处：《苏州科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：伴随着日益加快的城市现代化进程,地震这种突发性自然灾害带来的损失也日益增加,因此,基于最大限度地减轻地震灾害带给人们的损失的目的,大力进行地震工程方面的研究显得尤为必要。大量的震害研究表明,场地条件对土层地震反应有着重大的影响。理论上而言,我们应该避免这些不利地形,然而鉴于我国的基本国情(国家人口众多,土地资源有限)的原因,现实中很难完全避免这些不利位置,所以对于复杂场地地震反应的研究显得很重要。本文根据土层地震反应相关理论研究方法,借助于日本小田原试验场地相关参数模型和强震记录,文中提出一种复杂场地中地震波的输入和土介质中阻尼的选取方法,以日本小田原试验场地为算例,进行了一维模型和二维模型地震动响应分析,并与强震记录对比。本文得到以下研究结果:(1)对于地表强震记录,根据实际地形建立一维土柱模型,采用频域内的有限元方法弹性反演得到基岩基底地震动输入,并与较为常用的输入(1/2露头基岩记录)相比较,两者结果差别比较大。一定程度说明了小田原试验场地的非线性特征较为明显。(2)对于地表强震记录,根据实际地形建立一维土柱模型,采用国内外通用的程序进行等效线性化反演得到基岩基底地震动输入,并与理论输入(1/2露头基岩记录)相比较,两者还是存在差别,但是效果较之于弹性反演而言理想,影响计算结果的因素很多,如模型的建立,土介质动参数的选取,计算方法等。(3)在一维线性模型时域计算时,本文模型选取保持不变,土介质动力参数选取为等效线性化反演最终迭代结果,计算得出地震动响应(加速度时程曲线、加速度峰值、有效持时和加速度反应谱),并与地表测量记录相比较,结果都吻合的很好。说明这种土介质动力参数(阻尼比和剪切模量比)的选取,充分考虑到了土体的非线性特征,选取方法是行之有效的。(4)在二维模型计算时,本文同时建立三个二维模型,地震波的输入分别选取为1/2露头基岩记录(理论值),小田原试验场地KS1点等效线性化反演基岩基底地震波,KS2点等效线性化反演基岩基底地震波。土介质动力参数(剪切模量比和阻尼比)输入分别为线性土体本身,两个点各自等效线性化迭代后的最终土动力参数。经过模拟计算,得出本文提出的这种二维修正线性模型相较于二维线性模型更加贴近实际记录,也说明了本文这种阻尼比选取方法的正确性以及准确性。
[Abstract]:With the accelerating process of urban modernization, the loss caused by the sudden natural disaster of earthquake is also increasing day by day. Therefore, based on the purpose of minimizing the loss caused by earthquake disaster. It is particularly necessary to make great efforts in seismic engineering. A large number of earthquake damage studies show that site conditions have a significant impact on soil seismic response. Theoretically speaking, we should avoid these adverse terrain. However, in view of the basic situation of our country (the country has a large population, limited land resources), it is difficult to completely avoid these disadvantages in reality. Therefore, it is very important to study the seismic response of complex sites. According to the theoretical research method of soil seismic response, this paper makes use of the relevant parameter model and strong earthquake record of the Ota test site in Japan. In this paper, a method of selecting earthquake wave input and damping in soil media in complex site is proposed. The one-dimensional and two-dimensional model ground motion response analysis is carried out with the example of Ota test site in Japan. Compared with the strong earthquake records, the following results are obtained: 1: 1) for the surface strong earthquake records, a one-dimensional soil column model is established according to the actual topography. Using the finite element method in frequency domain, the ground motion input of bedrock basement is obtained by elastic inversion, and compared with the more commonly used input 1 / 2 outcrop bedrock record. The difference between the two results is quite big. To a certain extent, it shows that the nonlinear characteristics of the field are obvious. (2) for the surface strong earthquake records, a one-dimensional soil-column model is established according to the actual terrain. The equivalent linearization inversion program is used to obtain the ground motion input of bedrock basement, and compared with the theoretical input 1 / 2 outcrop bedrock record, there is still a difference between them. However, the effect is better than that of elastic inversion, and there are many factors that affect the calculation results, such as the establishment of model, the selection of dynamic parameters of soil media, the calculation method, etc.) in the time domain calculation of one-dimensional linear model. In this paper, the model selection remains unchanged, the soil dynamic parameters are selected as equivalent linearization inversion of the final iterative results, and the ground motion response (acceleration time history curve, acceleration peak value) is calculated. The effective duration and acceleration response spectrum are in good agreement with the surface measurements. The results show that the dynamic parameters (damping ratio and shear modulus ratio) of the soil are selected. Taking fully into account the nonlinear characteristics of soil, the selection method is effective. 4) in the two-dimensional model calculation, this paper establishes three two-dimensional models at the same time. The input of seismic wave is selected as 1/2 outcrop bedrock record (theoretical value) and equivalent linearization of KS1 point in Ota original test site for inversion of bedrock basement seismic wave. The equivalent linearization of KS2 point is used to invert the seismic waves of bedrock basement. The input of soil dynamic parameters (shear modulus ratio and damping ratio) is linear soil itself. The final soil dynamic parameters of the two points are equivalent linearization iteration. Through simulation and calculation, it is concluded that the two-dimensional modified linear model proposed in this paper is closer to the actual record than the two-dimensional linear model. It also shows the correctness and accuracy of the damping ratio selection method in this paper.
【学位授予单位】：苏州科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU435

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