大吨位预应力混凝土箱梁预张拉监测与分析

Pre-Tension Monitoring and Analysis of Large-Tonnage Prestressed Concrete Box Girder

为进一步提高箱梁抗裂性能,结合杭甬复线工程,对大吨位预应力混凝土箱梁在预张拉阶段进行混凝土应变现场监测,并采用有限元软件对预张拉方案进行优化分析。结果表明:通过对箱梁部分预应力钢束进行预张拉,箱梁各典型截面均出现一定的压应变增量,顶板压应变增量约为-23,底板压应变增量约为-22,可为箱梁顶板、底板提供约0.6 MPa的预压应力增量;预张拉施工工艺可使箱梁内部产生一定的预压应力,在满足混凝土强度要求前提下,应尽早拆除内部模板,选择在水化热温度和温差较大时段进行预张拉施工,并适当提高预张拉的控制应力。本文研究成果可为大吨位箱梁预制施工提供参考。

Based on the Hangzhou-Ningbo Expressway double-line project,the in-situ monitoring on the concrete strain in the pretension stage of the large-tonnage prestressed concrete box girder is carried out,and the pre-tension scheme is optimized and analyzed by finite element software,with a purpose to further improve the crack resistance of the box girder.The results show that by the pre-tension of the partially prestressed steel tendons,there is a certain increment of compressive strain in each section of the box girder.The increment of compressive strain in the top-plate is about-23,and the increment of compressive strain in the bottom plate is about-22,which can provide about 0.6 MPa increment of the pre-compression stress for the top and bottom plate of the box girder.The pre-tension construction process can generate certain pre-compression stress of the box girder,so when the concrete strength is satisfied the requirement,the internal formwork should be removed as soon as possible,and the pre-tension construction should be carried out when the hydration heat temperature and the temperature difference are big,and the control stress of the pre-tension can be appropriately increased.The research results can provide reference for the prefabrication construction of large-tonnage box girder.