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大跨径桥梁塔高、跨径大、自振周期长,深厚、软弱场地的长周期地震动对桥体结构影响较大。我国《公路工程抗震设计规范(JT J004-89)》也只适用主跨不超过150 m的梁桥和拱桥,国内长期以来没有一个适用于大跨径桥梁的抗震设计规范或指南。本文结合大跨径桥梁工程实例,根据场地土层静、动力性能参数的原位测试和动三轴试验结果,进行厚软场地土层地震反应分析,研究厚软场地的地震动效应,讨论了不同地震动强度时厚软场地的设计反应谱特征,分析了现行规范设计反应谱应用的局限性,成果对相关工程有重要指导意义,对大跨径桥梁抗震设计规范的制定也有借鉴作用。
Long-span ground motions of large-span bridges with high tower height, large span, long period of spontaneous oscillation, and deep and weak sites have a great influence on the bridge structure. China’s “code for seismic design of highway engineering (JT J004-89)” only applies to girders and arch bridges with main span not exceeding 150 m. There is no long-term domestic standard for seismic design or guidance applicable to long-span bridges. According to the engineering examples of long-span bridges, according to the static and dynamic parameters of the site in situ test and dynamic triaxial test results, the seismic response analysis of thick soft ground layer is carried out and the ground motion effect of thick soft ground is studied. The design response spectrum characteristics of thick and soft ground under different ground motions are analyzed. The limitations of the application of the current normative design response spectrum are analyzed. The results have important guiding significance for related projects and also serve as references for the formulation of seismic design codes for long span bridges.