断层场地效应对桥梁地震反应的影响

The statistical, theoretical analysis and simulation methods are used to study the ground motion effect at the near-fault site, also its effect on the earthquake response of bridge structure is analyzed. The main contents are as follows: (1) Based on the theoretical analysis of strong motion records, velocity model of fault and wave propagation theory, the isolation effect of non-causative-fault site and the amplification effect of fault fracture zone are studied, including its formation mechanism, and the relationship between the effect mentioned above and the geometric and physical characteristics, input angle and frequency contents of ground motion is discussed. The frequency dependent characteristics of ground motion at the fault site is analyzed. (2)Improve the convenient preprocessing and postprocessing, effective and accurate finite element program, with the combination of artificial multi-transmitting boundary, the modeling and calculation method is carried out to simulate the ground motion field at the large and complex site. Develop the universal numerical analysis method on the base of transmitting boundary.(3)The earthquake response characteristics of bridge across the fault is studied in order to explain the typical bridge damage in the recent large earthquakes. Propose a method to predict the bridge damage across the fault fast and effectively. The scientific evidence is afforded to evaluate the fault effect objectively, and also for the designation and seismic checking of bridge across the fault.

运用统计、理论分析及仿真手段探究断层场地地震动效应及其对上部桥梁结构地震反应分析的影响。主要研究内容包含：（1）基于强震动记录及断层速度模型与波传播理论分析，研究非发震断层场地的隔震效应、断层破碎带的放大效应，研究其形成机制，并探讨其与断层几何物理特征、地震动入射角度及频谱成分之间的关系，考察断层场地地震动效应的频率相关性特性；（2）完善前后处理方便且高效精确的通用有限元程序与多次透射人工边界相结合的模拟大型复杂场地地震动场的建模与计算方法，发展一种普适的基于透射边界的整体数值分析方法体系；（3）研究跨断层场地桥梁地震反应特征，用来解释近年来几次大地震中的典型桥梁震害，并提出一种快速有效的进行跨断层桥梁地震震害预测的方法。通过研究，为客观评价断层效应提供科学依据，并为跨断层桥梁的设计与抗震验算提供依据。

断层场地效应问题是近年来工程地震学界的研究热点，这种效应包含发震断层的永久位移效应和非发震断层的局部介质不均匀效应；如何考虑这两种场地效应对桥梁地震反应的影响，受到国内外地震工程学界的广泛关注。我们围绕这一问题，运用统计及数值模拟的手段，开展了如下几个方面的研究：（1）基于汶川地震鲜水河断裂、安宁河断裂、渭河断裂周边及集集地震中车笼埔断裂、彰化断裂获取的高质量强震动记录的处理和分析，获取了非发震断层的隔震效应及破碎带场地地震动效应，并依据断层速度模型与波传播理论，对其形成机制进行了解释；并就不同规模、不同特性断层对不同特性地震动输入下场地地震反应进行研究，获取了断层场地地震动效应的频率相关性特性。（2）对传统大质量法产生误差的原因进行探讨，并通过在ANSYS中改进的大质量法，来考虑非发震断层场地效应对桥梁地震反应的影响，成功考虑了桥梁结构与土层的相互作用；与此同时将粘弹性边界融入ANSYS中开展结构整体建模。（3）对集集地震、伊兹米特地震、汶川地震中跨断层和近断层典型桥梁的震害机理进行了详细的分析，并通过MIDAS软件对跨断层桥梁震害进行了数值模拟。（4）修改了传统震害预测方法中的震害影响因子及权重，使之能适应高烈度、平原地区桥梁震害预测，并将其成功应用于大庆市交通系统震害预测。我们还开展了工程场地、桥梁结构现场原位振动测试和数据分析，为后续试验研究打下了基础。