地震作用下近海桥梁的水-结构动力相互作用研究

The dynamic response behavior of offshore bridges is influenced by the surrounding water under earthquake action. Interaction with water causes additional hydrodynamic forces on the structure, which also modifies its dynamic properties. Therefore, the research on the water-structure interaction for offshore bridges has an important theoretical and engineering significance. The substructure method for analyzing the hydrodynamic pressure on uniform vertical cylinder surrounding by water is presented. The modal dynamic-stiffness relationship between displacement of the structure and hydrodynamic pressure is obtained by analytical method and numerical method, which is transformed into an accurate and efficient method in time domain by using the convolution algorithm consisting of the frequency-domain rational function approximation and time-domain auxiliary variable realization. The full finite element analysis model and method is established for simulating the dynamic interaction between the cylinder with arbitrary cross section or complex structure with water, which includes presenting the high-accuracy artificial boundary condition in time domain, establishing the dynamic finite element equation for water-structure interaction with displacement-pressure format, and developing a numerical computation method with high efficiency. The simplified formula for earthquake-induced hydrodynamic pressure on circular cylinder, elliptical cylinder, round-ended cylinder, and rectangular cylinder is developed by parameter analysis, numerical fitting methods. Based on the presented methods, the dynamic properties and seismic responses of the typical coastal bridges are analyzed, and the force characters and the law of the offshore bridge caused by the hydrodynamic pressure are revealed.

地震作用下水-结构的动力相互作用会对近海桥梁结构产生动水压力作用，该动水压力会改变结构的动力特性，影响结构的动力响应。开展地震作用下近海桥梁的水-结构动力相互作用研究具有重大理论和工程意义。针对竖向等截面结构，采用解析方法或数值计算程序获得桥墩位移和动水力之间的动力刚度关系，并通过时间卷积快速计算方法建立近海桥梁的水-结构动力相互作用时域子结构分析方法；针对任意截面和复杂结构，提出无限域水体的三维圆柱应力型高精度时域人工边界条件，构建流-固耦合系统位移-压力格式的动力有限元方程及其高效率数值计算方法，并通过集成建立近海桥梁的水-结构动力相互作用时域整体分析方法；通过参数分析、数值拟合等方式得到圆形、椭圆形、圆端形和矩形桥墩动水压力表达式的简化公式；利用建立的分析方法对典型近海桥梁进行动力特性与地震响应分析，揭示地震动水压力引起的近海桥梁结构的受力特点和规律。

地震作用下水-结构的动力相互作用会对近海桥梁结构产生动水压力作用，该动水压力会改变结构的动力特性，影响结构的动力响应。本项目针对任意截面柱体、轴对称柱体和竖向等截面柱体结构与水体的动力相互作用问题，提出了水-结构相互作用的三维和2.5维时域整体分析模型；进一步为了提高计算效率，针对圆柱结构，提出了水-柱体结构相互作用的时域子结构模型，并通过二次开发技术将该模型嵌入到了ABAQUS中；为了方便工程应用，假定水体不可压缩并通过对刚性和柔性柱体动水力解析解和数值解的拟合，提出了圆形、椭圆形、圆端形、矩形柱体以及倾斜圆柱和群桩基础附加质量的简化计算公式；最后，利用提出的附加质量简化公式对港珠澳跨海大桥连续梁桥段在地震和波浪作用下的动力响应进行了分析。本项目研究成果为地震作用下水-柱体结构相互作用提供了高效率、高精度的分析模型以及方便工程应用的附加质量简化公式。