Incremental launching method was adopted in steel U-girder construction of Jiubao North Approach Bridge. The longest cantilever length reached 85 m during launching. In order to investigate the safety of steel U-girder,a FE computation model was established considering launching device length, structural parameters and imperfection. Ultimate bearing capacities of different supports and spans were consistent which illustrated that the computation model was correct. The influence facters on ultimate bearing capacity of U-girders, such as launching device length, top/bottom flange thickness, web thickness, stiffener and imperfection were discussed. The results showed that steel U-girder constructed by incremental launching method is safe.%针对九堡大桥北引桥槽形钢梁最大悬臂85 m顶推施工的安全性,建立了包括顶推设备竖向支撑的纵向长度、结构设计参数和初始缺陷影响的槽形钢梁有限元模型.首先比较了不同支座条件、计算跨度对槽形钢梁的极限承载力计算结果的影响,表明计算模型是合理的.然后,通过引入顶推设备竖向支撑的纵向长度、钢梁顶板、底板、腹板厚度、加劲肋构造以及初始缺陷,分析了槽形钢梁在各种条件下的极限承载力.分析结果表明:槽形钢梁采用顶推法施工是安全的,且有足够的安全系数.
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