先张法预制U形梁单端张拉预应力施工技术研究

Research on the Single-End Prestressed Construction Technology of Prefabricated U-shaped Beam Pretensioned

结合某轨道交通工程预制U形梁工程实例,采用一联多片式长线法,整体单端先张拉多根预应力钢绞线,一次张拉长度超过78 m,研究不同施工阶段梁体预应力的损失情况。研究结果表明:逐根单端先张拉预应力钢绞线至设计应力的15%,而后整体单端先张拉预应力钢绞线至设计应力的100%,混凝土浇筑60 d后,梁体预应力平均损失≤5%,应力及伸长值符合设计要求。根据研究结果,一联多片式长线先张法预制U形梁施工中,采用先逐根再整体的单端先张拉技术是稳定可行的。

Combined with an example of a prefabricated U-beam project in a rail transit project,a single multi-piece long-line method is used to pull multiple pre-stressed steel strands at one end as a whole,and the length of one stretch exceeds 78 m.Then the loss of prestress in different stages is studied.The results show that the prestressed steel strands are first tensioned one by one to 15%of the design stress,and then the overall tensioned prestressed steel strands are used to 100%of the design stress.After 60 days of concrete placement,the prestress of the beam is averaged.The loss is≤5%,and the stress and elongation values meet the design requirements.According to the research results,it is proposed that in the construction of a prefabricated U-beam with a multi-piece long-line pre-tensioning method,the technique of pre-tensioning at the single end of the whole one-by-one is stable and reliable.