【作者】 李静；

【导师】 周晶；

【作者基本信息】 大连理工大学 ， 水工结构工程， 2007， 博士

【摘要】 我国目前正规划建设一批世界级的混凝土大坝，其抗震安全性成为设计中的关键技术问题之一。本文针对目前混凝土坝在非线性分析中涉及的若干问题开展了研究，主要包括地震动输入机制、考虑应变率影响的材料非线性模型、结构-地基动力相互作用的无质量地基模型研究以及同时考虑横缝作用和材料非线性分析的混凝土坝安全评价。具体如下：将时间信号时-频联合分析的自适应谱方法用于研究地震地面运动的频率非平稳特征、提取频率非平稳信息，统计得到各个频段地震动成分的强度变化过程。在此基础上，应用均匀调制随机过程模型和演变随机过程模型合成人工地震波，以此为输入对高拱坝进行了考虑地震动时-频非平稳性的动力响应分析。结果表明，在地震力作用较小时，影响不大，但对地震力作用较大的高拱坝，地震动的非平稳性对拱坝非线性地震响应的影响不可忽略。根据已有试验结果，通过引入损伤张量随应变率的变化建立了应变率相关的砼非线性损伤模型，对300米级的高拱坝的地震响应进行了计算，并分析了拱坝应变率和拉、压损伤的分布规律。结果表明，由于地震荷载引起的应变率在坝面的分布不同，坝面各处的动态性能变化并不一致，由此引起的混凝土强度和刚度的变化对于高混凝土拱坝的动力响应和安全性评价有重要影响。针对当前无质量地基和粘性边界地基计算处理中的一些问题，本文通过结构-地基的动力相互作用分析公式的推导，详细阐明了当前考虑地基影响的动力分析中无质量地基和粘性边界地基的概念和应用范围，对当前部分研究中的这两种地基应用中存在的问题进行了分析，并通过算例进行了说明。采用应变率相关的混凝土非线性损伤模型以及基于Lagrange乘子的点-点接触直接刚度法，进行了同时考虑混凝土材料非线性以及拱坝横缝接触非线性的高拱坝地震响应分析。研究表明，由于在地震过程中的混凝土非线性软化以及局部损伤开裂的影响，非线性拱坝横缝的开度及分布与采用线弹性砼本构关系计算结果有明显的不同，这对于横缝止水的设置具有重要影响。另外本文采用应变率相关的混凝土非线性损伤模型，研究了采用混凝土非线性本构情况下整体拱坝与考虑分缝拱坝的应力响应和损伤开裂的特点和差别。通过对实际拱坝的地震响应分析表明，基于非线性混凝土模型的整体拱坝模型动力响应分析可以基本反映拱坝的实际应力分布情况。更多还原

【Abstract】 Several large concrete dams are going to be build in china, the seismic safety evaluation is a very importment factor. In this paper, several problems about nonlinear analysis of concrete dams are discussed:Adaptive Spectrogram Method of Joint Time-Frequency Analysis is used to study the non-stationary properties of seismic ground motions. The parameters of frequency-dependent modulating function are obtained statistically based on the adaptive spectrogram analysis of seismic records of San Femado earthquake. Both mathematical models of uniform modulation random process and evolutionary random process are used to generate artificial seismic acceleration. The dynamic response analysis of a 300 meters high arch dam subjected to the artificial seismic excitations is studied and compared to predict the effect of non-stationary seismic motion. The calculation results show that the non-stationary frequency property of seismic ground motion has great effects on the dynamic response of nonlinear structure.A strain-driven formalism is adopted, improving the algorithmic efficiency as much as required for the analysis of large scale problems to become feasible. The non-linear seismic response of 300 meters high arch dam is presented using the proposed damage model and the distribution of strain-rate, tensile damage and compressive damage are analyzed and compared. And it is shown that the strain rates caused by seismic loading are different on the dam and have significant effects on the dynamic response of arch damsThe mass-less base model and viscous boundary base model are still the most wildly applied approximate methods for easiness though many approaches have been proposed for the seismic response analysis of soil-structure system. But there are some problems in the application of mass-less base model. In this paper, detailed formula for the soil-structure dynamic interaction analysis is derived, the concept and the application criteria of mass-less base model and viscous boundary base model is clarified and numerical examples are used to testify the correctness.The dynamic response analysis of high arch dam are intensely affected by the computational model, concrete strain-stress relationship and seismic input mechanism. In this paper, the seismic response analysis of a high arch dam is performed, in which the nonlinear concrete material is modeled by strain rate-dependant damage constitutive relationship and the nonlinear contact of joints is simulated by Direct Stiffness method based on the Lagrange Multiplier. The studies show that the nonlinear concrete model has great effects on the dynamic open displacement of contraction joints subjected to intense earthquake because of the nonlinear softening and local damage and cracking. This is very important to the performance of the water-tight in contraction joints. Based on the strain rate-dependant damage constitutive model, the dynamic response and damage characteristics are studied for arch dam model with and without simulating the opening-closing effects of joints. The analysis show that arch dam model without modeling contraction joints can give reasonable dynamic response results based on the nonlinear concrete model.更多还原