高寒地区后张箱梁纵向裂缝成因分析、验证及处理

Cause Analysis,Verification and Treatment of Longitudinal Cracks in Post-Tensioned Box Girders in Cold and High-Altitude Environments

为研究高寒地区后张预应力混凝土箱梁的纵向裂缝成因及损伤机理,采用钻孔法检测结构内部损伤特征,并利用Abaqus有限元软件分析孔道冻胀过程中的混凝土损伤行为。结果表明:低温环境下预应力孔道内水泥浆水化反应不充分、泌水受冻结冰膨胀是梁体混凝土沿纵向开裂的主要原因。冻胀过程中,孔道边缘混凝土率先受损,随后腹板内、外表面同时沿纵向开裂,底板顶面最晚出现纵向裂缝。基于纵向裂缝成因,提出采用排水注胶法,可有效地修复受损梁体。

The causes of longitudinal cracks and damage mechanism of post-tensioned box girder in the cold and high-altitude environments are studied.Boreholes were drilled to inspect the characteristics of the inner damages of the structure,and Abaqus was used to analyze the damage behavior of concrete due to frost heaving in ducts.At low temperatures,the cement grout in the ducts is not well hydrated,and the bleeding water is prone to freeze and expand,which are the main causes of longitudinal cracks in the concrete girders.During the frost heaving process,the concrete contact the walls of the ducts is damaged first,then followed the simultaneous cracking of inner and outer surfaces of webs in the longitudinal direction.At last,longitudinal cracks appear in the top surface of base plate.Based on the causes of longitudinal cracks,adhesive injection after drainage is proposed to repair the damaged girders effectively.