带模过冬工况下的连续刚构箱梁开裂机理研究

Research on Box Girder Cracking Mechanism of Continuous Rigid Frame under Winter Construction with Formwork

针对某大跨径预应力混凝土连续刚构桥箱梁带模过冬后的开裂机理展开研究。在详细调查了现场开裂情况的基础上,对开裂节段进行了空间实体有限元分析。分析结果表明,引起箱梁开裂的主要原因是:由于混凝土水化热和收缩的影响,在过冬期间混凝土与钢模板的变形存在差异,而模板拉杆阻碍了这一变形差异,从而在混凝土结构中造成较大主拉应力。若先张拉预应力再予以停工,则可以避免带模过冬引起的箱梁开裂。

The box girder cracking mechanism of a long-span prestressed concrete continuous rigid frame bridge under winter construction with formwork is studied.Based on the detailed investigation and statistics of the cracking situation at site,a spatial finite element analysis for the cracking segment is carried out.The analysis results show that the main cause of box girder cracking is as follow:considering the concrete hydration heat and shrinkage,there is a difference between the deformation of concrete and steel,which the formwork tie would try to prevent,so that a tremendous tensile stress in the concrete structure is caused.This kind of cracking can be avoided by tensioning the prestress before the winter shutdown.