大跨公轨合建斜拉桥主‒引桥地震相对位移响应与控制

Response and Control of Seismic Relative Displacement Between the Long-Span Rail-Cum-Road Cable-Stayed Bridge and the Approach Bridge

摘要:

基于巴拿马运河四桥研究了公轨合建斜拉桥在地震下的主?引桥相对位移响应与控制问题，分别建立了漂浮抗震设计方案、仅塔梁固结方案和固结方案有限元分析模型，分析了三种约束方案的相对位移响应。基于单自由度振子研究了相邻结构周期比和阻尼特性对结构相邻位移的影响。结合理论与参数分析，研究了主?引桥相对位移的控制方法。结果显示：主、引桥纵向首阶振型周期比、等效阻尼比之比以及阻尼机制对相邻结构的相对位移影响显著，其中周期比对相对位移的影响最为显著。不同粘滞阻尼器布置方案对主?引桥梁端相对位移的减震效果不同，直接在主、引桥梁?梁之间设置粘滞阻尼器有助于改善主桥与引桥梁端位移的同步性，控制效果最好；同时在主桥各墩位处和主、引桥梁?梁之间设置阻尼器的减震效果次之，但易于设计和安装，适应性好。

Abstract:

Based on the fourth Panama Canal Bridge， the seismic relative displacement responses and control of the main-approach bridge of the rail-cum-road cable-stayed bridge were studied. Finite element analysis models of floating aseismic design， tower-girder consolidation aseismic design and consolidation aseismic design were developed， and the relative displacement responses of the three design schemes were computed. The effects of the differences in nature periods and damping characteristics of two adjacent single-degree-of-freedom systems on their relative displacements were analyzed. In combination with theoretical and parameter analyses， the control method on the relative displacement of the main-approach bridge was investigated. The results show that period ratios of the first longitudinal modes， the equivalent damping ratios and the damping mechanism of the main bridge and the approach bridge have significant influences on the relative displacement of adjacent structures， and the period ratio is the most influential factor. Different arrangements of the viscous dampers have different controlling effects on the relative displacement of the main-approach bridge. Fixing all viscous dampers between the girder ends of the main-approach bridges could enhance the synchronicity of the motion of the two adjacent structures and consequently obtain the best controlling effects. Simultaneously using some dampers on the main bridge piers and the others at the connection of the girders could benefit the configuration design and installation of the system， although the reduction of the relative displacement is a little lower.