预应力混凝土连续箱梁顶板早期裂缝控制研究  

Control of the Early Cracks in the Top Slab of the Prestressed Concrete Continuous Box Girder

作　　者：王建强[1] 吕忠达[2] 赵卓[2] 刘成坤 孙筠[2] WANG Jianqiang;LV Zhongda;ZHAO Zhuo;LIU Chengkun;SUN Yun(Zhengzhou University,Zhengzhou,Henan 450001,China;Ningbo University of Technology,Ningbo,Zhejiang 315211,China;Shanghai Zhongliang Real Estate Group Co.Ltd,Shanghai 200062,China)

机构地区：[1]郑州大学,郑州450001 [2]宁波工程学院,宁波315211 [3]上海中梁地产集团有限公司,上海200062

出　　处：《铁道工程学报》2019年第9期43-48,共6页Journal of Railway Engineering Society

基　　金：宁波市桥梁技术科技创新团队(2014B81003)

摘　　要：研究目的:预应力混凝土连续箱梁在施工时常采用二次浇筑施工方法,但在一些工程施工完成后发现箱梁顶板出现大量裂缝,其中沿横桥向裂缝较多,造成箱梁顶板在施工阶段出现早期裂缝的原因主要是由于二次浇筑过程中顶板与腹板混凝土之间的收缩差和顶板混凝土水化热的温度效应。本文结合实际工程,对预应力混凝土连续箱梁顶板在二次浇筑时进行水化热温度场和早期应变的连续监测,研究预应力钢束分阶段张拉对箱梁顶板早期裂缝的控制效果。研究结论:(1)由于二次浇筑的连续箱梁顶板与已浇筑的箱室腹板之间存在一定的温差,并且腹板对顶板有一定的约束作用,顶板混凝土有开裂的风险;(2)对预应力钢束进行一次张拉时,顶板早期将产生较大的拉应力,混凝土将开裂;对预应力钢束进行分阶段张拉时,箱梁顶板的早期应变和应力均有一定程度减小,可有效降低箱梁顶板混凝土开裂的风险;(3)预应力钢束采用分阶段张拉施工工艺对终张后箱梁的受力性能没有影响;(4)本研究成果可为预应力混凝土连续箱梁的施工提供参考。Research purposes:The second casting method is often used in the construction of prestressed concrete continuous box girders.However,after completion of some projects,a large number of cracks were found in the top slab of the box girder,among which there are more cracks along the transverse direction of the bridge.The reasons of the early cracks are mainly due to the concrete shrinkage difference between the top slab and the web slab during the second casting process,and the temperature effect of concrete hydration heat of the top slab.In this paper,based on the actual engineering,the concrete hydration temperature field and early concrete strain of the top slab are continuously monitored during the second casting,and the control effect of the prestressed steel strands tensioned in stages on the early cracks in the top slab of the box girder was studied.Research conclusions:(1)Due to the temperature difference between the top slab and the web slab,and the web slab has a certain constraint effect on the top slab,so the top slab concrete has the risk of cracking.(2)When the prestressed steel strands are one-time tensioned,the top slab will have larger tensile stress in the early stage,and the concrete will crack.When the prestressed steel strands are tensioned in stages,the early strain and stress of the top slab concrete are reduced,which effectively reduces the cracking risk of the top slab concrete.(3)The construction technology of prestressed steel strands tensioned in stages has no effect on the mechanical performance of the box girder after final tension.(4)The research results are helpful to the construction of the prestressed concrete continuous box girders.

关 键 词：连续箱梁 顶板 早期裂缝 水化热 分阶段张拉 

分 类 号：U445.47[建筑科学—桥梁与隧道工程]