宜宾临港长江大桥抗震设计研究

Study of Seismic Technique for Yibin-Lingang Changjiang River Rail-road Bridge

宜宾临港长江大桥为主跨522 m公铁合建斜拉桥,桥宽63.9 m。该桥采用国内首创公铁平层设计,建成后将成为世界上宽度及跨度第一的公铁两用钢箱梁斜拉桥。为保证该桥的抗震安全性,依据现有规范和国内外多座大桥经验,制定了抗震设防标准和性能目标。基于抗震及车致振动影响,提出结构减震率作为评价指标,并通过建立全桥有限元模型进行非线性时程分析,总结阻尼系数、阻尼指数等参数对结构响应的作用规律。结果表明,黏滞阻尼器的阻尼系数和速度指数均对桥体抗震性能有较大影响,结构减震率可良好的反映减隔震装置减震效果。最终采用参数优化后的黏滞阻尼器,同时考虑固定支座熔断的纵向约束体系,以兼顾正常使用和抗震设防需要,可为今后公铁合建桥梁抗震设计提供参考。

The main bridge of Yibin Lingang Changjiang River rail-road bridge is a cable-stayed bridge with a main span of 522 m and 63.9 m in width.The flat layer rail-road bridge is the first of its kind in China,which will be the largest span and width rail-road steel box girder cable-stayed bridge in the world after it is finished.To ensure seismic safety of the bridge,special seismic fortification criteria and seismic performance target are established based on current codes and experiences of domestic and foreign bridges.Considering seismic and train induced vibration control,the seismic-reduction rate is recommended as the assessment indicator.The finite element model is established to conduct nonlinear time-history analysis and identify the impact of damping coefficient and nonlinear exponent of dampers on seismic responses.The results show that the damping coefficient and nonlinear exponent of the viscous damper have a great influence on seismic performance of this bridge and the seismic-reduction rate can reflect satisfactorily the damping effect of seismic isolation devices.Eventually,parameter-optimized viscous dampers with fusing bearings are adopted in constrained system to meet the demand of normal use and earthquake fortification,which can provide reference for aseismic design of rail-road bridges.