【作者】 田景元；

【导师】 刘汉龙；

【作者基本信息】 河海大学 ， 岩土工程， 2003， 博士

【摘要】 对于大尺度的土石坝等结构物由于其与外部围岩的接触面上各点的运动不同步而需进行多点输入地震反应分析的研究，1969年M.Dibaj和J.Penzien最早开始对此课题研究。由于土石坝在地震作用下的失效形式包括累积损伤破坏和过大的永久位移，本文从累积损伤和永久位移两方面研究土石坝多点输入相对单点输入地震反应有何不同，即多点效应如何，因此与多点输入分析相关的损伤值和永久位移的计算方法也在研究之列。本文的多点输入为顺河向和竖向的双向输入，附带研究了单点输入时双向地震动相关程度对反应的影响。本文在总结回顾过去工作的基础上，主要开展了如下6个方面的工作。 1、提出了基于动剪应力极值的土体损伤值计算方法。以往计算土体在不规则的动剪应力作用下的损伤值根据的是动剪应力的峰值，在时域内多点输入分析中，由于差动力的的存在，使得时程后段动剪应力不穿零而在一侧做幅度不大的波动，基于峰值的损伤值计算特别过高地估计了这段剪应力的破坏作用，过高的程度还随延时增加而增加。新方法克服了这一缺点，使得评价多点输入地震破坏作用更加合理。 2、提出了对人工合成地震动进行速度归零化的观点和方法。以往人工合成的地震波在地震结束时即地震加速度恒为零时速度不为零，这与合成地震动是“模拟输入点从静止到运动再到静止的运动过程”这一要求不一致，同时导致时域内多点输入分析时差动力过大以至算出的损伤值过大，于是本文提出了简易的地震动速度归零化方法并分析了其合理性。 3、完善了计算地震作用下土石坝的永久位移的等价节点力法中等价节点力的计算方法。本文认为多点输入的永久位移包括两部分，一是由累积损伤引起的，二是由地基永久位移附带的。经计算，第二部分相对较小可以忽略。而多点输入由累积损伤引起的永久位移可采用等价节点力法，水平面和最大静剪应力面两种等价节点力法中等价节点力的计算方法都在本文得到完善。 4、研究了时域内地震动的多点效应。若同时进行了多点地震动速度归零化和采用基于极值的损伤值计算方法，对于100米高的土石坝，多点输入与单点输入反应十分接近。对于240米高的超大型土石坝，坝体内永久位移和损伤值较大的部位多点输入的反应量较小，这是多点输入反应的特点或说多点效应。另外，多点效应也包括坝基部位的最大动剪应力和损伤值偏大这一效应。多点地震动的同步性越差，如地震波视波速越小，多点效应就越明显。用内差法合成的地震动输入情况下多点效应弱一些，但仍能体现多点效应。 5、研究了频域内地震动的多点效应，并对计算过程进行了一定程度的简化，即只需要计算输入地震动功率谱矩阵从大到小排列的前4个特征值所对应的地震动的动力反应。频域内多点效应与时域内有不一致的地方，即对于240米高的超大型坝，摘要对于竖向永久位移最大的坝顶部位和损伤值原本就比较高的坝顶及斜坡部位，频域内多点输入比单点输入的永久位移和损伤值反应要大些。不一致的原因在于频域内多点作用是通过拟静应力实现的。拟静力法假设了地基位移引起坝体内节点产生位移的过程是不需要时间的，‘这不符合实际。因此建议多点效应以时域内的为准。 6、研究了单点输入时水平和竖向的相关程度与反应的关系。对于240米高的超大型土石坝，相关程度越小，坝顶竖向永久位移和易破坏单元的损伤值越大，当竖向与水平向地震动强度接近时，这一规律更明显。时域和频域内这一规律是一致的。 本文的多点输入地震反应的结论可供土石坝抗震设计时参考，提出的新方法以及进一步完善后的原方法可应用到岩土工程相关领域，基于不规则动应力极值的损伤值计算方法有应用到机械等其它领域的前景。更多还原

【Abstract】 Multi-Point Input Method is necessary in Seismic Response Analysis of large scale earth dam, because the points move unsynchronously on the interface between the structure and surrounding rock, and the researching task was initiated by M. Dibaj and J. Penzien in 1969. Whether the earth dam lapses in Seismic Response Analysis is mainly judged by two criterion, the Damage Value and the permanent displacement, so the difference of response between Multi-Point Input and One-Point Input, that is the Multi-Point Effect, is also checked by this two criterion. Therewith the method to calculate Damage Value and permanent displacement is studied too. The Multi-Point Input is two directional, one direction is along river, and another is vertical. By way of parenthesis, In One-Point Input Method the relation is studied between the response and the correlative coefficient of horizontal and vertical earthquake wave. After reviewing the past work, 6 aspects of researching is developed as following:1. A more reasonable method to calculate soil’s Damage Value is advanced, which bases on extrema of irregular dynamic shear stress. Previously it bases on peaks of shearstress to calculate Damage Value, but by this method the destructive action of Multi-Point Inputted earthquake is overestimated, especially in the second half section of responding shear stress’ time history the shear stress caused mainly by differential force undulate slightly on one side of its zero line. Moreover the overestimated Damage Value increases along with the Delayed Time. The new method overcomes the old methods’ shortcoming.2. The idea and method to velocity-zeroize artifical accelerations is put forward. The precious method to simulate earthquake accelerations is not perfect because the points on the interface still move according to the simulated acceleration when the points’ motion ends, which is obviously a paradox. If the points’ velocity is not zeroized, soil’s Damage Value based on shear stress’s peaks or extrema is overestimated in Multi-Point Input Analysis. The new method’s rationality is analyzed.3. The way to calculate the Equivalent Joint-force is consummated in the Equivalent Joint-force Method to calculate dam’s permanent displacement caused by earthquake. It’s thought that dam’s permanent displacement by Multi-Point Input includes two parts, the first is caused by the Accumulated Damage, while the second is incidental to the basement’s permanent displacement. Based on computation, the second part can be neglected because it is relatively small. The permanent displacement caused by Accumulated Damage is calculated in Equivalent Joint-force Method, while the way to calculate the Equivalent Joint-force is consummated, both in the Equivalent Joint-forceMethod of Horizontal Face and Maximal Static Shear Stress Face.4. The Multi-Point Effect in time domain is studied. If the inputted accelerations are velocity-zeroized and the Damage Value is calculated according to shear stress’ extrema, as to 100-meter-high earth dam, Multi-Point Effect is not distinct; But as to 240-meter-high earth dam, in the part where permanent displacement and Damage Value is originally bigger the response is less tenser than that by One-Point Input, and in the part near basement the maximal shear stress and Damage Value is bigger, that is the Multi-Point Effect in time domain. Weaker the synchronicity of inputted accelerations is, for example, smaller the velocity of earthquake wave is, stronger the Multi-Point Effect is. The Multi-Point Effect with input of the artificial earthquake acceleration simulated by Interpolation Method is weaker than that of the directly simulated acceleration.5. The Multi-Point Effect in frequency domain is studied, and the analytical procedure is simplified to some extent, that is, the responding data is accurate enough only with the input according to the first four degressively arranged eigenvalue of earthquake power spectrum matrix. There are disaccordant conclusions of Multi-Point Input Analys更多还原