摘要
沪通长江大桥主航道桥为主跨1 092m的双塔钢桁梁斜拉桥,桥塔墩采用86.9 m(长)×58.7m(宽)×105m(高)的沉井基础,针对超长超宽混凝土沉井易发生早期裂纹的情况,研究控制混凝土沉井开裂的施工关键技术。考虑造成混凝土沉井开裂的因素——混凝土水化热、混凝土收缩、温度梯度,确定采用分节分块浇筑混凝土、设置后浇段以及局部抗裂钢筋相结合的裂纹控制措施。在上游段设置后浇段+增设抗裂钢筋、留2处不设置后浇段的措施,中间段设置后浇段、不设抗裂钢筋的措施,下游段设置后浇段+增设抗裂钢筋,并布置测量元件监测结构应变和应力。结果证明,设置抗裂钢筋使混凝土收缩应力沿钢筋轴向均匀分布,避免在截断处出现应力集中,设置后浇段可使后浇段两侧一定范围的混凝土自由变形,释放混凝土收缩产生的拉应力,提高了混凝土的抗裂性能,避免了混凝土沉井出现裂纹。
The main ship channel bridge of Hutong Changjiang River Bridge is a double-pylon steel truss girder cable-stayed bridge with a main span of 1092 m. The foundation of a pylon pier of the bridge is mainly the concrete caisson foundation in dimensions of 86.9 m （length） X58.7 m （width） X105 m （height）. In view of the problem that such very long and very wide concrete caisson is prone to early cracks, the key techniques for construction control of the cracks in the concrete caisson were researched. In consideration of the factors, such as the concrete hydration heat, shrinkage and temperature gradients, that could cause the cracks, it was determined that the combined crack control measures of casting the concrete of the caisson in lifts and in segments and arranging the late cast segments and local crack-resistant reinforcement should be taken. Specifically speaking, at the upstream part of the caisson, the late cast segments＋crack-resistant reinforcement were arranged and two places where the late cast segments were not to he arranged were reserved. At the middle part, the late cast segments were arranged and the crack-resistant reinforcement were not. At the downstream part, the late cast segments＋crack-resistant reinforcement were arranged and the measurement elements for monitoring the structural strain and stress were laid out. The results indicate that the arrangement of the crack-resistant reinforcement can make the concrete shrinkage stress distribute uniformly along the axial direction of the reinforcement and can avoid the stress concentration at the cutoff points. The arrangement of the late cast segments can make the concrete in the certain range of both sides of the segments deform freely, release the tensile stress caused by the concrete shrinkage, enhance the crack-resistant performance of the concrete and eventually avoid the cracks in the concrete caisson.
出处
《桥梁建设》
EI
CSCD
北大核心
2015年第4期113-118,共6页
Bridge Construction
关键词
斜拉桥
沉井
混凝土
裂纹
成因
施工控制
后浇段
抗裂钢筋
cable-stayed bridge
caisson
concrete
crack
formation cause
construction control
late cast segment
crack-resistant reinforcement
