黄冈公铁两用长江大桥抗震技术研究

Study of Seismic Techniques for Huanggang Changjiang River Rail-cum-Road Bridge

黄冈公铁两用长江大桥主桥为主跨567m的斜拉桥,为确保该桥的抗震安全性,通过分析已有规范抗震设防标准的不足,建立特殊的抗震设防标准及性能目标;借助有限元软件通过动力时程法计算半飘浮、不对称、弹性索、STU锁定及液体粘滞阻尼器等5种结构抗震支承体系的结构地震响应;运用能量法原理,以桥塔弯矩最小为目标值,推导并建立阻尼器参数的优化设计方法。研究结果表明:该桥采用100年设计基准期作为抗震使用年限,提高抗震设防标准是合适的;液体粘滞阻尼器体系可作为该桥优选的结构抗震支承体系;阻尼器参数中的非线性指数可通过取小值以兼顾地震与列车制动的要求;阻尼系数取4 000kN/(m/s)0.25、非线性指数取0.25、动力行程取550mm的阻尼器能够满足该桥抗震设计要求。

The main bridge of Huanggang Changjiang River Rail-cum-Road Bridge is a cable- stayed bridge with a main span 567 m. To ensure the seismic safety of the bridge, the special seismic fortification criteria and seismic performance target were established after analysis of the deficiencies of the seismic fortification criteria in the existing codes. The seismic responses of 5 types of the structural seismic support systems of the semi-floating, asymmetric arrangement, e- lastic cable, STU lock and fluid viscous damper were calculated by the dynamic time-history method by the aid of the finite element method. The minimum bending moment of the tower of the bridge was taken as the target value and the principle of the energy method was used to derive and establish the optimal design method for the parameters of the fluid viscous damper. The results of the study indicate that if the service years of the bridge are based on the 100-year designed datum period, it will be appropriate to improve the seismic fortification criteria of the bridge. For the structural seismic support system of the bridge, priority should be given to the utilization of the fluid viscous damper. By choosing the small values for the nonlinear exponents in the parame- ters of the damper, the damper will satisfy both the seismic and train braking requirements and a damper having the damping coefficient of 4 000 kN/（m/s）^0.25 , the nonlinear exponent of 0.25 and the dynamic stroke of 550 mm can satisfy the seismic design requirement of the bridge.