大跨度高低塔公铁平层合建斜拉桥结构体系研究

Research on Structural Systems for Long-Span Cable-Stayed Road/Rail Bridge with Unequal Height Pylons

甬舟铁路富翅门公铁两用跨海大桥采用主跨388 m高低塔公铁平层挑臂式钢箱梁斜拉桥,为世界上最大跨度的高低塔公铁平层合建斜拉桥。为研究适用于大跨度高低塔公铁平层合建斜拉桥最优结构体系,结合富翅门公铁大桥结构不对称的特点,对5种不同类型半飘浮体系、塔梁约束体系进行比选研究。通过对5种约束体系在静、动力荷载作用下的桥塔弯矩、桥塔位移、主梁位移对比分析,推荐采用高塔侧设置固定支座、矮塔侧采用活动支座的约束体系,该体系抵抗纵向荷载能力强、释放体系温度变形差,与常用的半漂浮体系相比,在静、动力荷载作用下桥梁总荷载效应小,具有良好的静动力性能,其中静力作用下两桥塔塔底总弯矩降低15%,两侧梁端总位移降低51%,两塔顶位移减少29%;动力作用下两桥塔塔底总弯矩相当,两侧梁端总位移降低76%。

Fuchimen Sea-crossing Bridge of Ningbo-Zhoushan Railway adopts cantilever steel box girder cable stayed bridge with main span of 388 m,and it is the largest cable-stayed bridge with unequal height pylons serving rail and road in the same floor.In order to develop the optimal structural system for the bridge,five different types of semi floating systems and tower beam restraint systems are studied combined with the characteristics of structural asymmetry.Through comparative analysis of the bridge tower bending moment,bridge tower displacement and main beam displacement of five restraint systems under static and dynamic loads,the restraint system with fixed support on the high tower side and movable support on the low tower side is recommended.The system has strong resistance to longitudinal load and poor temperature deformation of the release system.Compared with the commonly used semi-floating system,the total load effect of the bridge is small under static and dynamic load with good static and dynamic performance.Under static load,the total bending moment at the bottom of the two bridge towers is reduced by 15%,the total displacement at the ends of the two side beams is reduced by 51%,and the displacement at the top of the two towers is reduced by 29%.Under dynamic action,the total bending moment at the tower bottom of the two bridges is equivalent,and the total displacement at the beam ends on both sides is reduced by 76%.