震源路径效应的地下二维多点地震动模拟理论与方法研究

Numerical results of structures under earthquake excitations are related to and even depend on the seismic motions, especially for large-span structure subjected to multi-support seismic excitations. Currently, relevant studies on multi-support seismic excitations are almost confined to one-dimensional earthquake ground motions in essence, and the earthquake resource and propagation path effects are not considered in these seismic excitations. Therefore, in the strict sense, it is difficult to satisfy the requirement of large-span spatial structure including foundation, which is characterized by considering foundation and bi-dimensionality (i.e. sizes of both planar dimensions are commensurate with each other). This project focuses on the studies of theory and implementation method for simulating the bi-dimensional multi-input earthquake underground excitations considering the source and path effects, including the following：(1) Establishing the transfer function considering filtering effect of multi-layers, and then deriving underground power spectrum model considering the filtering effect of multi-layer soil; (2) Generalizing planar bi-dimensional coherence function of multi-support earthquake underground excitations; (3) Proposing a method for simulating the bi-dimensional multi-support earthquake underground excitations incorporating the resource and path effects, and further developing a visual program based on the proposed theory and method. The study is of theoretical and practical, and aims at providing an effective method and feasible technical support for the simulation of bi-dimensional multi-support earthquake underground excitations considering the source and path effects.

地震作用下，结构的数值分析结果依赖于甚至取决于输入的地震动，大跨结构的多点地震反应对地震动更为敏感。对于考虑地基影响的大跨空间结构体系而言，通常采用的多点地震动由于仅限于地表且大多在本质上只考虑了一维相干性，而在严格意义上无法满足地基-大跨空间结构体系同时具有的两个特点：“考虑地基”和“二维性，即平面内两个维度尺寸相当”，而且也未能直接体现震源路径的传递效应。该项目同时考虑震源路径的传递因素，研究地下二维多点地震动的模拟理论和方法：（1）建立考虑地基多土层过滤效应的传递函数，推导考虑多土层过滤效应的地下地震动目标功率谱模型；（2）研究并建立地下多点地震动平面二维相干函数；（3）最后，提出引入震源路径效应的地下二维多点地震动的模拟理论和实现方法，并进行可视化程序开发。该申请项目兼有理论性与实用性，旨在为考虑震源路径效应的地下二维多点地震动的模拟提供切实有效的理论方法和技术支持。

对结构在地震作用下的反应进行数值模拟分析，是评估结构抗震性能的一种有效途径。在合理确定结构和研究方法的前提下，结构在地震激励下的动力反应与地震动输入密切相关，甚至取决于地震动的输入。对于大跨结构（如大跨度桥梁、大坝和地下隧道等）抗震分析而言，地震动的空间变异性需要加以考虑。因而，对多点地震动进行研究具有重要的现实意义。然而，当前关于多点地震动的研究存在局限性，主要体现在：（1）局限于平坦场地的地表地震动研究；（2）大多研究仅考虑了地震动的地表的相干性；（3）当前普遍采用的多点地震动模拟理论和方法未尚未直接纳入地形相干和路径传递效应的影响。本项目针对以往研究中的不足，对地下多点地震动进行了研究，研究的主要工作及成果如下：（1）提出并建立了地表和地下相干函数关系，并适用于平面二维相干模型；（2）提出了考虑路径传递效应的地下多点地震动模拟理论，并基于上述理论开发了地下多点地震动模拟的可视化程序；（3）提出了考虑地形效应的分层峡谷场地地下多点地震动模拟理论，并基于上述理论开发了分层峡谷场地地下多点地震动模拟的可视化程序。