近断层城市建筑群地震响应研究的一体化方法

This project aims at presenting an integration method for studying numerically the earthquake process and damage of a city near the causative fault, such as Beichuan Town during Wenchuan earthquake and so on. The project will resolve the problem of lack of the research methodology on earthquake response of a near-fault city with building clusters to which close attention should be paid. First, using the series multi-degree-of-freedom model of shear-bending type for 3D building structure, an investigated lump method of shear-bending wave propagation is presented for analyzing the elastic and Elasto-plastic earthquake response of the 3D building structure. It provides a wave-based simulation tool for the study on the earthquake response and damage of a 3D building structure. Second, using mesh grading approach for the interface of earth medium and adopting the same sized investigated lumps as many as possible within the calculating domain of the bedrock, an investigated lump method of saving both time and memory is presented for seismic wave propagation inside 3D earth medium. Third, the mutual conversion is implemented between the body wave in earth medium and the shear-bending wave or shear wave of the 3D building structure by using the connecting investigated lump for the connection of wave propagation. Fourth, the rupture process of the causative fault is implemented by using a finite fault source model in the calculating domain of earth medium. Finally, integrating the research works mentioned above, an integration method is presented for studying the earthquake responses and damages of building clusters in a city near the causative fault. This project provides a wave-based computational method and its related simulation software for reproducing and explaining the earthquake damages，having occurred，of building clusters in the city near the causative fault or for predicting the probable earthquake hazards of building clusters in a near-fault city.

本项目旨在为研究类似汶川地震时的北川县城等近发震断层的城市地震过程及震害问题提出一种数值计算的一体化方法。针对以建筑群为重点关注对象的近断层城市地震研究，本项目解决缺乏研究方法的问题。首先，基于弯剪型多自由度体系模型提出三维建筑结构的弹性和弹塑性波动分析的被研究块体方法，为三维建筑结构的地震响应及破坏研究提供模拟工具；其次，地球介质内部交界面处采用网格分级方法，基岩区域尽可能采用尺寸相同的被研究块体，提出计算量小且省内存的三维非均匀地球介质中地震波传播的被研究块体方法；然后，提出实现地球介质中体波与三维建筑结构弯剪波和剪切波之间波动相互转换与传播的被研究块体连接方法；再引入有限断层震源模型，实现发震断层的破裂过程；最后，系统集成上述研究工作，提出近发震断层的城市建筑群地震响应与震害研究的一体化方法。本项目为再现和解释已发生或预测未来可能发生的近断层城市建筑群的震害提供了计算方法和模拟软件。

通过数值方法研究，针对近断层城市结构群地震响应的一体化方法、非均匀地球介质中波动传播的网格分级技术和结构地震响应波动分析方法进行了深入的研究，取得了有意义的成果研究。通过理论分析方法，针对短跨框架结构的行波效应进行了较为深入的研究，获得了新的认知。.在近断层城市结构群地震响应一体化方法研究与应用方面，发展了近断层城市结构群地震响应的一体化方法并应用于近断层山区城市地震响应的分析。一方面，该方法将线弹性地球介质模型升级为粘弹性地球介质模型；另一方面，该方法将基于剪切模型的多层结构地震响应的波动分析方法升级为基于空间模型的框架结构地震响应的波动分析方法。该新方法具有可研究地震波在框架结构中传播以及可考虑地球介质粘弹性的特点。.在非均匀地球介质中波动传播的网格分级技术和结构地震响应波动分析方法研究方面，针对相邻介质波速差别很大的非均匀粘弹性地球介质，提出了一种能够显著降低计算量和内存需求的网格分级技术并开发了计算程序，针对高耸结构地震响应提出了波动分析方法并开发了计算程序，上述研究工作为位于存在盆地等复杂非均匀地球介质之上的近断层城市结构群地震响应一体化分析提供了有利工具。.在短跨框架结构行波效应研究方面，获得了新的认知：行波效应不仅包括相位偏移效应也包括频率效应。频率效应是短跨框架结构产生行波效应的机理，激励频率越低，行波效应越显著。此外，基于无约束模型提出了一种新的直接求解多点激励下框架结构响应的解析方法。该方法无需将结构响应的绝对位移分成拟静力位移和动力位移，初步揭示了相对运动法中的拟静力位移来自刚体模态位移这一机理。