预应力混凝土连续箱梁裂缝产生原因及预防措施研究

Study on Causes and Preventive Measures of Cracks in PC Continuous Box Girder

为研究混凝土箱梁顶板裂缝产生原因,对一座预应力混凝土连续梁桥采用实体单元建立全桥数值模型予以计算分析。依据TB 10092-2011《铁路桥涵混凝土结构设计规范》给出的分布函数计算出沿板厚方向的温度分布,根据经验公式计算出先浇混凝土与后浇混凝土之间的收缩差,分析温差与收缩差两种因素对箱梁顶板应力的影响。研究结果表明:顶板的温差荷载对其下缘拉应力影响较大,两侧翼缘对腹板的遮阳作用能较大程度降低顶板下缘的拉应力,先浇混凝土与后浇混凝土之间的收缩差在合龙段产生较大拉应力。依据分析结果提出了一些有效预防措施,可供相关工程参考。

In order to study the causes of cracking in top flange of concrete box girder,a numerical model of a PC continuous beam is established using solid element.According to the distribution function given in the railway bridge and culvert code,the temperature distribution along the slab thickness direction was calculated,and the shrinkage difference between the pre-casting concrete and the post-casting concrete was calculated according to the empirical formula.The influence of temperature difference and shrinkage difference on the stress of top flange of box girder was analyzed.The results shows that the temperature difference of the top flange has a great influence on the tensile stress of the lower surface,the shading effect of both flanges on the web can greatly reduce the tensile stress of the lower surface of the top flange,and the shrinkage difference between the pre-casting concrete and the post-casting concrete will also produce a large tensile stress in the closure section.Effective preventive measures were put forward according to the analysis results,providing some references for relevant projects.