某预应力混凝土箱梁桥悬臂施工中底板纵向裂缝成因分析及处理措施  

Analysis of Causes Inducing Longitudinal Cracks in Base Slabs During Cantilever Construction of A Prestressed Concrete Box Girder Bridge and Treating Measures

作　　者：胡志红 王攀 邹红丹 

机构地区：[1]武汉交通工程建设投资集团有限公司,湖北武汉430056 [2]中交武汉港湾设计研究院有限公司,湖北武汉430020 [3]武汉市公路工程咨询监理公司,湖北武汉430051

出　　处：《世界桥梁》2015年第3期86-90,共5页World Bridges

摘　　要：某预应力混凝土连续梁-刚构组合箱梁桥跨径布置为(80+2×150+80)m,箱梁为直腹板单箱双室截面,采用挂篮悬臂现浇施工,在前8个节段的施工过程中,箱梁底板出现了纵向裂缝。采用ANSYS建立1号、2号节段箱梁实体有限元模型,计算4种荷载工况下箱体的应力分布情况,并监测箱梁混凝土养护过程中的横向应力和温度,分析了箱梁底板纵向裂缝开裂原因。分析得出混凝土内部的梯度温度荷载效应是底板产生纵向裂缝的主要原因,提出加强箱梁底板的横向配筋及重视箱梁底板养护的处理措施。采用上述措施后,后续梁段的施工监测发现箱梁底板没有出现明显的纵向裂缝。The bridge cited as an example in this study is a combined prestressed concrete con- tinuous beam and rigid-frame composite box girder bridge with span arrangement of（80＋2× 150＋ 80） m. The box girder adopts the two-cell single box cross section with straight diaphragms, cas- ted in situ in cantilevers using form travelers. During the construction of the first 8 sections, longi- tudinal cracks were found in the base slabs of the box girder. ANSYS was used to establish the fi- nite element models of the No. 1 and No. 2 box girder sections and calculate the stress distribution condition of the girder under 4 load cases. By analyzing the distributive law of the cracks in the base slabs of the girder, the transverse stress and temperature during the curing of the box girder concrete were monitored, and the causes inducing longitudinal cracks in the base slabs of the box girder was analyzed. The results of the analysis indicate that the gradient thermal loading effect in- side the concrete takes the major responsibility for longitudinal cracks. Then the measures for in- tensifying the transverse prestressing tendons in the base slabs of box girder were proposed. The curing of base slabs should also be given enough attention. By using the aforementioned measures, no marked longitudinal cracks were found in the base slabs of the box girder during the construc- tion monitoring of the girder sections.

关 键 词：预应力钢筋混凝土桥 箱形梁 悬臂施工 纵向裂缝 原因分析 梯度温度 处理措施 

分 类 号：U445.57[建筑科学—桥梁与隧道工程]