地震作用下深水高墩桥梁水动力模型与流固耦合效应研究

The fluid-structure interaction between high piers, pile group foundations and flow field around subjected to earthquake has been an important factor that affects the seismic performance of the bridge with high piers in deep water. Therefore,the hydrodynamic force model and effects of fluid-structure interaction on seismic response of the bridge with high piers in deep water subjected to earthquake are studyed in this project．By employing numerical simulation method and shaking table experiments, the mechanism of fluid-structure interaction between high piers , pile group foundations with high pile cap of the bridge in deep water and flow field around subjected to earthquake are investigatived. And the hydrodynamic force model and analytic model of seismic response of the bridge are established. The regularities of seismic response and seismic performance of the bridge are summarized that are the theoretical basis for the amendment to the domestic seismic design criteria of the bridge with high piers in deep water. The main contents are as follows：(1)The motion regularities of flow field in deep water subjected to earthquake will be studyed; (2)The mechanisms of fluid-structure interaction between high piers and flow field around subjected to earthquake will be researched and the regularities and influence factors of high piers' hydrodynamic force will be investigated. The high piers'hydrodynamic force model of the bridge in deep water subjected to earthquake will be established; (3)The mechanisms of fluid-structure interaction between high-cap pile group foundations and flow field around subjected to earthquake will be researched and the regularities and influence factors of high-cap pile group foundations' hydrodynamic force will be investigated. The high-cap pile group foundations' hydrodynamic force model of the bridge in deep water subjected to earthquake will be established; (4)The influence regularities of fluid-structure interaction on seismic response of the bridge with high piers in deep water will be analysed. And the proposals for amending to the domestic seismic design criteria of the bridge with high piers in deep water will be put forward.

地震作用下深水桥墩、群桩基础与周围流体相互作用是影响深水高墩桥梁抗震性能的重要因素，本项目拟进行地震作用下深水高墩桥梁水动力模型与流固耦合效应研究，采用数值仿真与模型振动台试验相结合的方法，探索地震作用下深水高墩桥梁墩身、高桩承台群桩基础-水体流固耦合作用机理与规律，建立深水高墩桥梁地震水动力模型，总结深水高墩桥梁地震响应规律与抗震性能特点，为深水高墩桥梁抗震设计提供理论依据。主要研究内容为：（1）地震作用下深水流场的运动变化规律；（2）地震作用下深水高墩桥梁墩身-水体流固耦合作用机理、墩身水动力作用规律、影响参数与墩身水动力模型；（3）地震作用下深水高墩桥梁高桩承台群桩基础-水体流固耦合作用机理、高桩承台群桩基础水动力作用规律、影响参数与高桩承台群桩基础水动力模型；（4）深水高墩桥梁地震反应规律与抗震性能特点；针对国内桥梁抗震规范不足，提出深水高墩桥梁抗震设计的改进方法与建议。

近年来，在我国西部山区以及东部沿海等地震高烈度区修建了许多跨江（河）、跨海高墩桥梁，地震发生时这些桥梁的墩柱和基础将遭受地震动水压力的作用，威胁桥梁的抗震安全。然而目前对这些深水高墩桥梁的抗震性能规律还缺乏深刻认识，国内外的研究成果还不能满足实际工程的抗震需求。本项目的主要研究目标是通过揭示地震作用下深水高墩桥梁群桩基础、墩身与水体流固耦合作用机理与规律，建立深水高墩桥梁地震响应数值分析模型，总结深水高墩桥梁抗震性能特点与规律。为此，项目组采用模型试验以及数值模拟的方法开展了如下研究：首先，完成了群桩基础-承台结构、实体桥墩、低桩承台群桩基础-实体高墩、低桩承台群桩基础-空心高墩以及群桩基础-T型刚构水下结构流固耦合模态动力响应模型试验；在试验分析基础上，建立了深水结构流固耦合模态动力响应数值模拟方法，总结出了深水群桩基础-承台、实体桥墩以及空心高墩结构模态响应规律，特别是高阶振动、墩顶附加质量以及空心墩墩身内水的影响规律。接着，分别基于粘性流体的N-S方程以及基于势流体理论建立了地震作用下深水高墩结构流固耦合数值分析模型，通过比较总结出了地震作用下深水桥墩结构流固耦合动力效应数值模拟方法，在此基础上，探讨了简谐地震以及随机地震作用下深水群桩基础、高墩与水体流固耦合作用机理、动水压力作用规律、影响参数及其墩身附加质量分布模型。而后，建立了同时考虑主-引桥耦联作用、碰撞效应以及流固耦合效应的深水高墩桥梁地震响应分析模型，总结出了深水高墩桥梁的地震响应规律，探索出了主-引桥碰撞效应对深水桥梁抗震性能的影响。最后，依托实际工程，建立了能够考虑桥墩屈服的深水高墩以及深水高墩桥梁非线性地震响应分析模型，研究深水环境下深水高墩以及深水桥梁地震响应特点与地震损伤规律，数值模拟结果与实际桥梁震害相吻合。本项目的研究成果可为深水高墩桥梁的抗震设计提供理论与方法指导，提升深水高墩桥梁的防震减灾能力。