考虑冲刷效应的大跨桥梁地震-风-车-桥耦合振动分析

Coupled Vibration Analysis of Earthquake-Wind-Vehicle-Bridge for Long-Span Bridges Considering Scouring Effect

为研究冲刷效应对地震与风联合作用下大跨桥梁动力响应的影响,在已建立的地震-风-车-桥耦合振动分析模型基础上,利用p-y曲线(p为土阻力,y为变形)折减法考虑不同冲刷深度的桩土荷载-位移关系,根据桩土荷载-位移关系和冲刷深度更新桩基的侧向支撑刚度和长度,从而考虑了冲刷效应对大跨桥梁动力响应的影响,并将模型应用到江顺大桥冲刷效应的分析研究中.研究结果表明:基础冲刷减弱了地基土对结构的侧向约束,从而降低结构的自振频率,侧向振型的自振频率最大降低6.01%;在运营车辆和风荷载作用下,基础冲刷对结构的振动响应影响很小;在地震发生后,基础冲刷会增大结构的横向振动,结构的横向位移响应极值最大增大9.1%,横向位移响应谱也相应增大,而对结构的竖向振动影响很小;基础冲刷可能减小车辆横向加速度的响应,车辆的横向加速度响应极值最大降低7.7%,对车辆的竖向振动影响很小.

In order to study the influence of the scouring effect on the dynamic response of long-span bridges under the combined action of earthquake and wind,based on the established coupled vibration analysis model of earthquake-wind-vehicle-bridge,the p-y curve(p is the soil resistance and y is the pile displacement)reduction method was used to consider the load-displacement relationship between the piles and soil with different scour depths,and the lateral support stiffness and length of pile foundation were updated according to the load-displacement relationship and scour depth.Thus,the influence of the scouring effect on the dynamic response of long-span bridges was considered,and the model was applied to analyze the scouring effect of Jiangshun Bridge.The results show that the foundation scour weakens the lateral constraint of the foundation soil on the structure,thus reducing the natural vibration frequency of the structure,and the maximum reduction of the natural vibration frequency of lateral vibration mode is 6.01%;under the action of the operational vehicle and wind load,foundation scour has little effect on the vibration response of the structure;after the earthquake,the foundation scour increases the lateral vibration of the structure,and the maximum increase in the extreme value of the lateral displacement response of the structure is 9.1%;the lateral displacement response spectrum increases accordingly,but it has little effect on the vertical vibration of the structure;foundation scour may reduce the response of lateral acceleration of vehicles,and the maximum reduction of the extreme value of the lateral vehicle acceleration response is 7.7%,but it has little effect on the vertical vibration of vehicles.