高墩连续刚构桥长边跨现浇段施工方案比选

Comparison and Selection of Construction Schemes for Long Cast-in-Situ Segments of Side Spans of a High-Rise Pier Continuous Rigid-Frame Bridge

上坡米一号大桥主桥为(72+120+120+72)m预应力混凝土连续刚构桥,主梁采用单箱单室截面,T构主梁采用挂篮悬臂浇筑施工。针对过渡墩高(69.91m)且边跨现浇段长(11m)的特点,结合桥址处的地形条件,提出了墩顶吊架施工(方案1);先不对称浇筑、再合龙中跨、最后合龙边跨(方案2);先合龙中跨、再不对称浇筑、最后合龙边跨(方案3)3种边跨现浇段施工方案,采用MIDAS Civil软件建立全桥有限元模型,分析3种方案的关键截面应力、成桥线形和主墩偏移,并从适用性、安全性、经济性及工期等方面对3种方案进行综合比选,选择方案3。实践证明采用方案3施工,结构受力与变形合理,且施工适用性较强、安全性高、经济性好、工期短。

The main bridge of the Shangpomi Bridge No.1is a prestressed concrete continuous rigid-frame bridge with span arrangement（72＋120＋120＋72）m.The main girder of the bridge is of the single-cell single-box section and the T-frame main girder was constructed by the cantilever casting method by the form travelers.In the light of the characteristics that the transition pier of the bridge is high（69.91m）and the cast-in-suit segments of the side spans are long（11m）and in consideration of the topographic conditions at the bridge site,3construction schemes for the castin-suit segments were proposed,i.e.the scheme 1,the utilization of the pier-top lifting frames,the scheme 2,the asymmetrically casting of the segments first,the closing of the central spans then and the closing of the side spans finally and the scheme 3,the closing of the central spans first,the asymmetrically casting of the segments then and the closing of the side spans finally.The finite element model for the whole bridge of the bridge was established,using the software MIDAS Civil,the stress in the critical sections,the geometric shapes of the completed bridge and the offsetting of the main piers of the 3schemes were analyzed.The 3schemes were also comprehensively compared from aspects of the applicability,safety,economy and construction time schedules and the scheme 3was finally selected.Practice proves that with the selected scheme 3,the structural force conditions and deformation of the bridge are reasonable,the construction applicability is good,the safety is high,the economy is effective and the construction time schedule is short.