【作者】 王艳；

【导师】 辛全才；

【作者基本信息】 西北农林科技大学 ， 水利水电工程， 2010， 硕士

【摘要】 混凝土重力坝是一种应用极为广泛的重要坝型,其横缝的存在削弱了混凝土重力坝的整体刚度,在地震载荷作用下,其常会导致在大坝上部出现贯穿性的裂缝。强震作用下有横缝混凝土重力坝的动力响应是一个复杂的非线性过程,受到很多因素的影响,比如地震波、边界条件、库水动水压力等。为了全面系统地了解地震作用下混凝土重力坝的动力响应规律,为工程设计提供一定的参考,论文以存在多条横缝的三维整体坝体为对象,应用有限元软件ABAQUS在时域内以显式有限元方法对动力方程进行求解,进行了地震响应仿真计算方法的研究,分析了横缝对重力坝自振特性和地震响应的影响,探索了高效率和高精度的混凝土重力坝模态分析与地震响应分析的仿真方法。本文主要开展了以下几个方面的工作：(1)设计了六种计算模型,就横缝、库水以及坝体与坝基山岩之间交互作用方式对混凝土重力坝自振特性的影响进行了研究。计算结果表明：横缝削弱了坝体的刚度,表现为固有频率增大,其中基频增幅最为明显；考虑库水影响时系统的质量增大,坝体自振频率较空库模型有所降低,而其对基频的影响最为显著；按照接触考虑大坝与地基及两侧山岩的相互作用时,刚度降低,导致自振频率较按固连考虑时小。(2)按照是否考虑横缝以及模拟横缝的不同仿真方法设计了四种算法,分别对混凝土重力坝进行了地震响应分析,研究了采用不同的仿真算法时重力坝动位移、横缝法向张开度、动应力以及加速度响应的变化规律,探索了更符合现实的混凝土重力坝地震响应仿真计算方法。研究表明：分缝模型的动力响应明显大于不考虑横缝影响的整体模型,尤以横河向的动力响应增幅最为明显,表明横缝在混凝土重力坝地震响应仿真计算中的影响不容忽视；而对考虑横缝时的几种不同的仿真方法进行比较后,发现：按照单一坝段进行地震分析时的动力计算结果偏大；对于分别以接触与Cohesive单元模拟坝段之间的相互作用的模型,发现前者的计算结果大于后者,而后者由于模拟了真实的横缝材料,并考虑了法向拉应力,更符合现实情况。(3)应用ABAQUS中的子模型有限单元技术,对混凝土重力坝进行了在重力作用下的静力分析,改进了仿真方法,实现了高效和高精度的目的。并尝试将此方法运用于混凝土重力坝的地震响应分析中,虽然大大地节约了计算CPU时间,但误差较大,相信采用子程序或与其他第二方软件的相结合,可以实现子模型技术在重力坝地震响应分析中的应用。更多还原

【Abstract】 Concrete gravity dam is an important dam type which is widely used. However, the existence of transverse joints weaken the overall stiffness of the concrete gravity dam, which often causes penetrating cracks in the upper section of the dam under earthquake action. The dynamic response of concrete gravity dam with transverse joints under severe earthquake is a complex nonlinear process, which is influenced by many factors, such as seismic waves, boundary conditions, hydrodynamic pressure and so on. In orde to understand the dynamic response law of concrete gravity dam under seismic loads comprehensively and systematically, and provide some reference for the engineering design, this paper uses the 3D whole dam model with more than one transverse joint as research object and uses the explicit finite element method in the time domain to solve the dynamic equations based on finite element software ABAQUS, studies on the simulation technology of the seismic response, analysis the effect of transverse joints on natural vibration properties and dynamic response of the gravity dam, and probes into the simulation method of high accuracy and high efficiency which can be applied in the modal analysis and seismic response analysis of ctoncrete gravity dam.The major work done in this paper is listed as following:(1)Six calculation models are designed for the study on the influence of the transverse joints, the reservoir water and the interaction with dam and dam foundation rock to the vibration performance of concrete gravity dam. The calculation results show that the transverse joints weaken the stiffness of the dam, which appears as the increase of the natural frequency, particularly the fundamental frequency; Compare with the reservoir empty model, it leads to increase the system quality and reduce the natural frequency of dam, especially the base frequency when considering the impact of the reservoir water. It will reduce the stiffness when the interaction between dam and foundation is studied as mutual contact, which makes the natural frequency of concrete gravity dam is relatively small compared to tie constraints.(2)Four algorithms are designed according to whether to consider the influence of transverse joints and the various simulation methods respectively to analysis the seismic response of the concrete gravity dam, study the change law of the dynamic displacements, the transverse joints aperture, the dynamic stress and the acceleration when using different simulation methods, explore the simulation method for the seismic performance analysis of concrete gravity dam which is more practical. The research indicates that the dynamic response of the model with transverse joints is significantly greater than that of integrated model, particularly the seismic response along transverse, which shows that the transverse joints can not be ignored in the analysis for the seismic responses of the concrete gravity dam; Conclusion from comparing betwween various simulation methods shows that the dynamic calculation results of single dam are too large; Besides, it is founded that the calculation results of the contact method are greater than the cohesive algorithm, which is reality-oriented because of the simulation of the true cross joint material and the consideration of the normal pulling stress.(3)The simulation method for static analysis of the concrete gravity dam is improved which realized for high efficiency and accuracy by the application of the sub-model technology in ABAQUS. It also gives a trial discussion of the application for this technology in the seismic response analysis of the concrete gravity dam. It saves the computing CPU time greatly, however, it also bring great errors. It is believed that it will come true for the application of the sub-model technology in the seismic response analysis of the concrete gravity dam when the subprograms or the combine with other software are applied.更多还原