公路钢桁梁桥组合桥面预制板湿接缝收缩自应力计算分析

Comparative Calculation of Self-shrinkage Stress on Wet-joint in Precast Concrete Bridge Deck

混凝土桥面板现浇湿接缝是预制装配式桥梁的常见连接方式和关键受力部位;而湿接缝与预制桥面板通常存在6个月的龄期差,湿接缝混凝土在收缩作用下容易发生开裂。为研究预制混凝土桥面板湿接缝收缩自应力特性,以某公路组合桥面简支钢桁梁桥为研究背景,利用大型有限元软件ABAQUS建立精细组合单元模型,对比研究在不同钢筋搭接形式、混凝土强度和养护条件下,湿接缝混凝土收缩自应力的变化规律。以60 d收缩应力为例,结果表明:现浇湿接缝最大收缩应力发生在预制混凝土板与湿接缝交界面处,纵向接缝的收缩应力比横向接缝大15.7%~25.5%;不同养护条件可显著影响收缩应力,养护条件为70%≤RH<99%时湿接缝收缩自应力比40%≤RH<70%时减少36.9%~46.1%;混凝土强度越高,湿接缝收缩应力越大,C45混凝土比C40混凝土的收缩应力增大2.5%~3.8%,C50混凝土比C40混凝土的收缩应力增大5.3%~16.5%;湿接缝不同钢筋搭接形式对收缩应力影响不大:U形钢筋连接湿接缝的收缩应力比直钢筋连接增大0~8.5%;在运营阶段车辆荷载局部作用下,纵向和横向湿接缝以及预制混凝土板最大主应力分别为7.8、6.1、6.7 MPa。

The cast-in-place wet joints of concrete bridge decks are a common connection method and the key stress area of prefabricated bridges.The wet joints and precast concrete decks usually have a 6-month age difference,so,the wet joint concrete is easy to crack under the action of shrinkage.In order to compare characteristics of the self-shrinkage stress of wet joints in precast concrete bridge decks,a simple supported steel truss bridge was used as a prototype,and the large-scale finite element software ABAQUS was used to establish a minute integrated element model.And comparative study was conducted on the change of self-shrinkage stress of wet-joint concrete under different forms of bar connection,concrete strength and maintenance conditions.Taking the 60-day shrinkage stress as an example,all following results were got from the research.The maximum shrinkage stress of the cast-in-place wet joint occurs at the interface between the precast concrete slab and the wet joint.The shrinkage stress of the longitudinal joint is 15.7%~25.5%larger than that of the transverse joint.Moreover,different maintenance conditions can significantly affect shrinkage stress.The shrinkage stress of wet joints decreases by 36.9%~46.1%under the condition of 70%≤RH<99%compared with that of 40%≤RH<70%.Thus,the higher the concrete strength is,the larger the shrinkage stress of the wet joint will become.The shrinkage stress of C45 concrete is 2.5%~3.8%larger than that of C40 concrete,and the shrinkage stress of C50 concrete is 5.3%~16.5%larger than that of C40 concrete.The impact of different forms of bar connection is not large:the shrinkage stress of the U-shaped bar type is increased by 0~8.5%compared with that of the straight bar type.Under the local load of the vehicle during the operation stage,the maximum principal stresses of longitudinal and transverse wet joints and precast concrete decks are 7.8,6.1,6.7 MPa,respectively.