近海桥梁桩基础抗震性能理论和试验研究

With a synergy of experiences accumulated from offshore structural engineering and river bridge engineering, and by considering specific offshore environments， site conditions and corrosion due to soil environments applied to offshore China, this project aims to systematically study the design optimization, modeling, seismic analysis as well as the geotechnical site specific response analysis methods toward seismic design of pile foundation for supporting offshore bridges. With the objective of minimizing the computation efforts without degrading necessary calculation accuracy, the project will present an efficient method to model and calculate the nonlinear seismic response of pile-soil systems, by accounting for the effects of both scour and hydrodynamic structure-water interactions. New V/H spectra will be proposed and their influence on the seismic response of offshore bridge foundations will be studied. Through a series of 3D shaking table tests using multidirectional laminar container (shear model box), validations of the numerical calculation will be performed and the strain distribution and failure modes will be investigated. The project will also study the sensitivity of modal parameters influenced by the foundation failure occurrences and the characteristics of the possible failure modes, thus facilitating the relevant practice of vibration based structural health monitoring. The project will also summarize the research and engineering practice for mitigating the negative influence due to corrosion on steel piles. The project will efficiently contribute to the engineering practice of offshore bridge structural engineering in China.

本项目充分借鉴国内外发展相对成熟的海洋结构工程和江河桥梁工程的经验，结合我国近海复杂的地质条件、海洋环境和土壤腐蚀的影响，系统研究近海桥梁结构桩基础的优化设计、建模、抗震分析、计算不同土层深度处地震动的场地分析方法。通过考虑地基冲刷和水动力效应，同时满足计算精度和计算代价的要求，提出有效的地震和海洋环境影响下桩基础建模和非线性动响应的计算方法。提出适合我国近海桥梁采用的V/H谱计算公式,并总结和现行规范相比新的V/H谱对基础抗震性能的影响。采用层状多向剪切模型箱开展三维振动台试验，对数值计算结果进行校核并进一步研究桩的应变分布和破坏形式。项目将研究桩基础和简化的桥墩结构整体振动模态参数对不同部位破坏和不同失效模式的敏感度，为基于振动的桩基础健康监测提供建议。项目将总结国内外近海结构物钢桩基础抗腐蚀的设计和工程实践经验;研究成果可直接指导工程设计，从而有助于加快我国近海桥梁工程发展的步伐。

在本项目的资助下，针对近海桥梁桩基础的抗震问题，开展了以下研究内容：.（1）考虑地基冲刷和地震水动力效应，建立了地震和海洋环境影响下桩-土建模和数值计算方法；（2）采用层状多向剪切模型箱开展三维振动台缩尺试验，结合数值计算分析，研究了桩基础对场地土动力特性的影响；3）结合我国近海桥梁采用的V/H谱计算公式，提出了采用海域反应谱作为目标谱拟合海域空间变化地震动的方法；4）提出了适应于我国近海地形和地质的场地分析的高效方法。项目总结了国内外近海结构物钢桩基础抗腐蚀的设计和工程实践经验;研究成果可直接指导工程设计，从而有助于加快我国近海桥梁工程发展的步伐。