大跨径上承空腹式梁拱组合刚构桥设计关键技术

Key Design Techniques for Long-span Open Web Arch-stiffened Girder Rigid-frame Bridge

为克服主跨大于200 m的山区桥梁在桥型选择中采用连续刚构桥易导致的弊端,以及选用上承式钢筋混凝土拱桥由于适用条件存在的局限性,提出了将常规预应力混凝土连续刚构桥和上承式钢筋混凝土拱桥在结构体系上进行组合,形成上承式梁拱组合刚构新桥型。大跨径上承空腹式梁拱组合刚构桥的结构体系和力学特征进行了分析,采用有限元分析方法对该桥型的主要结构参数、合理成桥状态、拱梁汇合段构造、梁拱倒三角区施工和临时扣索的合理拆除时机等设计关键技术开展研究,结果表明:上承空腹式梁拱组合刚构桥利用下弦拱辅助主梁受力并形成自平衡受力体系,显著减小了中跨和边跨主梁长度,使结构力学性能得以优化,具有结构竖向刚度大,对长期挠度变形控制效果好的优点;当结构关键控制点的强度、刚度和线形计算指标符合目标范围时,可达到合理成桥状态;拱梁汇合段的下弦拱顶板与上弦梁底板的交汇构造采用A字形,构造简单,传力效果好,施工质量容易控制;该桥型适宜采用平衡悬浇节段施工,梁拱倒三角区段上弦梁和下弦拱均需采用临时斜拉扣挂辅助结构受力,下弦拱临时扣索宜在拱梁汇合段形成后与中跨常规梁段跨中合龙之前分批拆除,上弦梁临时扣索在全桥合龙后拆除。

To overcome the disadvantages of using continuous rigid-frame bridge in selecting bridge type for mountainous bridges with a main span larger than 200 m,and the limitations of using reinforced concrete deck arch bridge due to the applicable conditions,a novel open web arch-stiffened girder rigid-frame bridge is proposed,which combining the conventional continuous rigid-frame bridge and deck arch bridge in the structural system.The structural system and mechanical characteristics of the bridge type are analysed by using finite element analysis to study the key design technologies such as main structural parameters,reasonable bridge state,construction of arch-girder confluence section,construction of inverted triangle area of girder-arch,and reasonable timing of removal of temporary buckling cable,etc.The result shows that the open web arch-stiffened girder rigid-frame bridge uses the lower chord arch to assist the main girders and form a self-balancing force system,which significantly reduces the length of mid-span and side-span of main girders,and optimizes the structural,mechanical properties with the advantages of large vertical stiffness and good control effect on long-term deflection and deformation.When the strength,stiffness,and linearity calculation indicators of critical control points of structure meet the target range,a reasonable bridge completion state can be achieved.The convergence of top slab of lower chord arch and the bottom slab of upper chord girder is constructed in the form of A-shaped structure,which is simple and effective in force transmission,and easy to control the construction quality.This type of bridge is suitable for balanced cantilever section construction.The upper chord girder and lower chord arch in the inverted triangle section of beam arch need to use temporary cables to assist the structural stress.During the dismantling phase,the lower chord arch temporary cables should be removed in batches after the formation of girder arch combined section,and the mid-span span conventional girder section before the closure,while the upper chord girder temporary buckle cables should be removed after the main bridge closure.The study describes the engineering practice of Chongqing Lijia Jialing River Bridge,the key design techniques for long-span archstiffened girder rigid-frame bridge can provide a valuable reference for the construction of similar bridges.