超大跨度公铁两用斜拉桥结构体系研究

Research on Structural Systems for Very Long-Span Rail-cum-Road Cable-Stayed Bridge

为了寻求超大跨度公铁两用斜拉桥结构受力最优的结构体系,以常泰长江大桥主跨1176 m公铁两用斜拉桥为工程背景,在设计中研究了常用结构体系在纵向风荷载、温度荷载、活载、制动力及地震等作用下的结构力学行为。针对超大跨度斜拉桥梁端位移大、桥塔弯矩大等主要问题,基于结构温度变形特征优化纵向荷载传力途径,提出了“温度自适应塔梁约束体系(TARS)”。该体系采用CFRP水平索连接桥塔和主梁上的温度不动点,主梁受到纵向约束的同时不会因温度变化产生较大的结构内力,可大幅降低梁端位移和塔底弯矩。与常用结构体系对比,TARS结构静、动力性能优越。

The structural systems enabling the very long-span rail-cum-road cable-stayed bridge to exhibit optimal load bearing performance have been researched.The Changtai Changjiang River Bridge,which will be a rail-cum-road cable-stayed bridge with a main span of 1176 m,is taken as a prototype bridge.In the design process,the mechanical properties and behaviors of the conventional structural systems under the actions of longitudinal wind loads,thermal loads,live loads,braking forces and seismic loads were investigated.The very long-span cable-stayed bridge also means big girder-end displacements and bending moment in pylons,to address these problems,a thermal-adapting tower-deck restraint system(TARS)is proposed,based on the optimization of transfer paths of longitudinal loads as per the characteristics of temperature-induced structural deformation.TARS features the horizontal CFRP cables that connect the temperature fixed points on the pylons to those on the main girder,which allow the main girder to be longitudinally restrained,as a result,big structural internal forces will not occur in the main girder as the change of temperature,thereby leading to the reduction of girder-end displacement and pier-base bending moment.Compared with the conventional structural systems,TARS has superior static and dynamic properties.