钢-混组合连续箱梁施工预拱度设置影响因素研究

为确定合理的临时支撑间距与拆除时机、负弯矩区剪力连接件类型及是否设置桥面板预留槽等,以便于钢-混组合连续梁桥设置合理的预拱度,以某(40+75+75+40)m钢-混组合连续梁桥为背景,采用MIDAS Civil软件建立全桥有限元模型,分析相关设计与施工因素对预拱度设置的影响规律。结果表明:钢梁拼装时应采用临时密支撑,并在正弯矩区桥面板混凝土浇筑后再拆除临时支撑;负弯矩区应采用抗拔不抗剪连接件,桥面板正、负弯矩交界区域应设置桥面板预留槽;仅边跨设置向上的混凝土收缩徐变预拱度值,而中跨不需设向下的混凝土收缩徐变预挠度值。该桥边、中跨跨中钢梁制造预拱度分别为17.7mm和161.9mm,施工时考虑了10mm的弹性变形预抬值。成桥时组合梁线形误差在±10mm内,满足设计要求。

Study of Influential Factors on Pre-camber Setting for Steel-Concrete Composite Continuous Box Girder During Construction

To facilitate the setting of rational pre-camber for steel-concrete composite continuous box girder bridge,the proper spacing and demolition timing of temporary supports,types of shear connectors in hogging moment zone and whether or not to reserve shear pockets on deck panels should be determined.A steel-concrete composite continuous girder bridge with four spans of40,75,75 and 40 mwas taken as the background project.The software MIDAS Civil was used to build the model of the overall bridge,to analyze the influential law of related design and construction factors on pre-camber setting.The results show that temporary supports should be densely distributed during the assembly of steel girders,and dismantled after the pouring of deck concrete in positive moment zone.In the hogging moment zone,stud connectors should be able to resist uplifting force,but incapable of resisting shear force.Shear pockets should be reserved in the interfacial area of positive and hogging moment decks.The upward pre-camber to absorb concrete shrinkage and creep is only needed on side spans,and no downward pre-deflection to handle concrete shrinkage and creep is needed on intermediate spans.The manufacturing pre-cambers for the steel girders in the side span and intermediate span are 17.7 mm and 161.9 mm,respectively.In the construction period,apre-lift value of 10 mm was considered to address elastic deformation.The geometric error of the composite girder in completed bridge state is within the range of±10 mm,meeting the design requirements.