考虑海水-海床-斜拉桥相互作用下纵桥向设置BRB的减震作用与优化设计

Seismic reduction effect and optimal design of BRB in longitudinal bridge direction under seawater-seabed-cable stayed bridge interaction

由于海洋场地存在深厚的海水层,其对海底地震动特性以及海洋结构物的地震反应存在较大影响,在跨海桥梁等海洋结构物抗震分析时不容忽视。因此,研究基于地震波动理论建立海水-海床-斜拉桥耦合的地震波动分析模型,确定海水层对结构地震反应的影响。考虑海洋环境可能对减震构件的耐久性造成威胁,提出一种应用耐久性能优良的防屈曲支撑(Bulking Restrained Brace,BRB)作为纵桥向减震构件的斜拉桥减震体系,并且以青州航道桥为工程背景,通过其与漂浮体系斜拉桥模型的地震反应对比,验证了考虑海洋环境影响下该减震体系的可行性。研究对BRB的布设位置与设备参数等进行优化分析,进一步确定BRB作为斜拉桥纵桥向减震构件的设计方法。研究发现地震作用下海水产生的动水效应会放大斜拉桥上部结构的地震反应。通过对比不同工况下结构的地震反应,发现在桥墩与桥塔位置同时设置BRB时,桥梁整体减震效果最佳。另外,BRB的屈服承载力等参数对斜拉桥的抗震性能亦产生较大影响。

Due to the existence of a deep seawater layer in marine sites,its influence on the seabed ground vibration characteristics and the seismic response of marine structures is significant and should not be ignored in the seismic analysis of marine structures such as cross-sea bridges.Therefore,to determine the influence of the seawater layer on the seismic response of the structure,the study establishes the seismic fluctuation analysis model based on the seismic fluctuation theory for the coupled seawater-seabedstayed bridge.In addition,considering that the marine environment may pose a threat to the durability of the damping members,the study proposes a new type of cable-stayed bridge damping system using Bulking Restrained Brace(BRB)with excellent durability as the longitudinal damping member,and takes the Qingzhou Channel Bridge as the engineering background to verify the seismic response by comparing it with the floating system cable-stayed bridge model.The feasibility of the new type of seismic damping system considering the influence of the marine environment is verified.The study optimizes the location and equipment parameters of the BRB.The design method of BRB as a longitudinal damping member for cable-stayed bridge is further determined.It is found that the hydrodynamic effect generated by seawater under the seismic action will amplify the seismic response of the super-structure of the cable-stayed bridge.By comparing the seismic response of the structure under different working conditions,it is confirmed that the best overall seismic damping effect of the bridge is achieved when the BRB is installed at the pier and tower locations simultaneously.Besides,the parameters such as yield bearing capacity of BRB also have a great influence on the seismic performance of cable-stayed bridges.