玉磨铁路元江特大桥钢桁梁悬臂架设关键技术

Key Cantilever Erection Techniques for Steel Truss Girder of Yuanjiang Bridge of Yuxi-Mohan Railway

玉磨铁路元江特大桥主桥为(108+151.5+249+151.5+108)m上承式连续钢桁梁桥,主桁由2片钢桁架组成。根据该桥钢桁梁的结构特点及施工条件,选择采用主跨对称单悬臂架设方案施工。施工中,全桥共设置3组临时支架和2组超高临时墩(设置在两端次边跨,最高达133.1 m),有效解决了次边跨钢桁梁悬臂架设时结构承载能力和抗倾覆不足的问题;在超高临时墩顶部设置柔性抄垫装置(由顶部结构、板式橡胶垫、楔形钢板、刚性抄垫等组成),有效减弱了钢桁梁悬臂架设过程中该处的转角和偏心效应;根据不同边坡等级要求采用不同防护形式的综合山体防护方案,合理解决了山区桥梁建设过程中边坡防护问题;采用以动态线形控制为基础的应力分析方法,提高了应力分析的准确性。

The main bridge of Yuanjiang Bridge of Yuxi-Mohan Railway is a continuous steel truss girder bridge with the deck atop the two lateral trusses.The bridge has a main span of 249 m,two side spans of 151.5 m and two secondary side spans of 108 m.Given the structural characteristics of the steel truss girder and site space,the assembly of trusses in the main span was started as a single cantilever from the two main piers towards the midspan.During the construction,a number of three sets of temporary scaffolds and two sets of high-rise temporary piers were applied,since the load bearing capacity and anti-overturning ability of the structure were insufficient in the phase of cantilever assembly of steel trusses in the secondary side spans.The two sets of the high-rise temporary piers were installed in the secondary side span on each end,with a maximum height reaching up to 133.1 m.Flexible paddings,which include the pier head,laminated rubber pads,wedge steel plates and stiff paddings,were filled into the head of the high-rise temporary piers to effectively reduce the pier-head rotation and eccentricity during the cantilever assembly of the steel truss girder.Diverse slope protection measures were taken to handle with varying grades of slopes with different protection requirements,aiming to resolving the slope protection issue in the construction process of bridges in mountainous areas.A stress analytical method based on dynamic geometry control was utilized to improve the precision of stress analysis.