【作者】 赵密；

【导师】 杜修力；

【作者基本信息】 北京工业大学 ， 结构工程， 2004， 硕士

【摘要】 摘 要在高层、高坝和核电站等重大复杂结构的动力反应分析中，波动能量向无限域地基的逸散影响是重要的。由于这类问题的求解规模巨大，且可能包含多种介质耦合、介质材料非线性及界面动接触非线性等因素影响，需要发展高效的数值分析方法才能用于这些实际问题的解决。显式有限元结合局部人工边界的方法由于其时空解耦的特点，很适宜于上述复杂的近场波动问题的求解，因而获得学术界和工程界的重视。文中针对两种局部人工边界，粘弹性边界和透射边界，进行了研究，获得了一些有参考意义的认识。提出了一种改进的粘弹性人工边界，它与现有的粘弹性边界相比具有以下优点：（1）物理模型简单，不含附加质量；（2）表达式与全部介质参数相关，物理意义更加合理；（3）模拟精度高。透射边界稳定性的算例分析表明：现有透射人工边界的稳定实施方法是经验性的，缺乏可供参考的客观的参数选取依据，不便于工程人员操作；在某些情况下会对计算精度产生不利影响。精度比较分析表明：本文提出的广义粘弹性边界具有与二阶透射人工边界相当的精度。有限元模型影响分析表明：（1）在满足波动有限元分析要求的前提下，采用不同时空离散步距的有限元模型分析同一问题时，粘弹性边界结果稳定，透射边界结果受不同模型影响较明显。（2）外源波动问题分析较相应的内源波动问题需要更大的人工边界尺寸。半球谷局部地形对入射地震动的影响问题和流-固介质分层耦合问题的分析表明，显式有限元结合粘弹性人工边界的解耦时域波动分析方法是有效的近场波动数值模拟方法。更多还原

【Abstract】 For the dynamic analysis of some important complex structures such as high-rise,high dam, nuclear power station and so on, the wave propagation from structure intoinfinite foundation should be considered. The problem is huge for solution, and mayinclude mediums coupling, medium material nonlinearity and dynamic contactinterfaces etc. Therefore, an effective numerical method must be provided for thedynamic analysis of this large complex system. The combination method of theexplicit finite element method and the local artificial boundary is applicable to solutethe above complicated problem because of its uncoupling characteristic. In thedissertation, the studies on the viscous-spring boundary and the transmitting boundaryare carried out and some useful conclusions are achieved. In the dissertation, a kind of new calculation formulation of viscous-springboundary is proposed. Comparing with the existing viscous-spring boundaries, it hasadvantage as flowing: (1) the boundary model is simple and doesn’t include the addedmass. (2) The boundary expressions include all medium material constant. (3) Themethod’s accuracy is high. The numerical analysis of stability for transmitting boundary indicates that theexisting methods of control instability are experiential, be short of the objective basisof parameter choosen and affect the accuracy in some conditions. The analysis of accuracy indicates that the accuracy of viscous-spring boundaryin the dissertation correspond to that of second-order transmitting boundary. Theanalysis of effect of finite element model indicate: (1) when the different finiteelement models are used to analyze the same problem on the premise that theaccuracy of wave finite element is satisfied, the result of viscous-spring boundary fordifferent model is stabler than that of the transmitting boundary. (2) The analysis onwave problem with load outside finite field needs bigger boundary size than that withload inside finite field. The analysis of the local landform problem of hemisphere canyon and thecoupling problem of layered medium of fluid and solid indicate that the combination II<WP=6>Abstractmethod of the explicit finite element method and the viscous-spring boundary iseffective.更多还原