PC连续箱梁悬臂段空间效应的影响参数研究

Study on Influencing Parameters of Spatial Effect in Cantilever of Prestressed Concrete Continuous Box Girder

为了分析采用移动模架法进行逐段现浇的PC(Prestressed Concrete)连续箱梁悬臂端底板出现纵向裂缝的原因,结合工程实例,采用有限元方法建立了3种不同计算模型进行比较,确立了一种高效而又精确的有限元计算模型,并通过对箱梁悬臂段空间效应及相关影响参数的研究,分析了底板纵向裂缝的形成原因。研究表明:端部预应力纵向分量和门形吊架支反力是导致悬臂端底板横向拉应力过大而出现纵向裂缝的主要因素。简单地采用增加底板宽度、厚度等措施并不能有效降低悬臂端底板横向拉应力,必须从结构、力学及材料3个方面采取综合的裂缝防治措施。

In order to analyze the cause for longitudinal cracks on the bottom slab of cantilever of PC continuous box girder constructed by sect-by-sect moulding using the MSS （movable scaffold system） method, three different FE models of an actual project were established and compared, and the efficient and exact model was ascertained to study spatial effect and correlative influencing parameters. Further more, the cause for longitudinal cracks was also discussed.It is shows that the main cause for the cracks is the excessive transverse stress of caused by longitudinal part of end prestressing and resistance of door-shape suspensory frame. Simply increasing the width and thickness of bottom slab cannot reduce the bottom slab transverse stress of cantilever efficiently, and integrated measures of structure, mechanics and material must be taken to prevent the cracks.