呼准铁路黄河特大桥刚构连续梁设计关键技术研究

呼准铁路黄河特大桥主桥采用高墩、长联、大跨刚构连续梁的结构形式,为了确保结构设计安全,需要解决以下关键技术问题:选择合龙顺序、确定合龙顶力、减小梁体徐变下挠、解决梁端和支座处较大的水平位移等。结构设计时运用有限元程序对主桥进行了整体静力分析、箱梁横向环框计算、桥墩罕遇地震延性分析以及车桥耦合动力仿真分析等详细计算,确定主桥为2个固结墩;采用先合龙次中跨、再次边跨、然后边跨、最后中跨的合龙顺序;在设计条件下采用9 000 kN的跨中合龙顶力;通过调整钢束张拉顺序、二期恒载上桥时间以及预留体外预应力束等措施解决大跨梁的徐变下挠;通过设置梁端大位移伸缩装置及大位移活动支座适应梁体较大的水平位移。结果证明刚构连续梁的结构受力和变形均满足规范要求。

Research on Key Technologies in the Design of Yellow River Rigid Frame Continuous Beam Bridge on Hohhot-Zhunge'er Railway

The extra-long bridge over the Yellow River on Hohhot-Zhunge'er Railway uses rigid frame continuous beam structure with high pier,long span and long unit. Some key technical problems must be settled such as the selection of closure sequences,the determination of closure jacking force,the reduction of creep deflection and the horizontal displacement at the beam end and the bearing. The finite element program is employed in the design to analyze the integral static force of the main bridge,calculate the box girder transverse ring frame,analyze the ductility of the pier in case of rare earthquake and conduct vehicle/bridge interaction. Study results suggest two rigid piers for the main bridge. The first closure is the second middle span followed by the second side span and the side span,and the last is the middle span. By adjusting the tension sequence of the steel beam,the time of the two phase dead load and the external pre-stressed tendon,the creep deflection of the long-span beam is solved. Large horizontal displacement of the beam is accommodated by installing large displacement expansion device and large displacement movable bearing. The results show that the stress and deformation of the rigid frame continuous beam structure meet the specification.