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在长线法生产预应力多孔板时,为了防止由于预应力损失而造成预应力值不足的现象出现,往往采用一次超张拉工艺,错误认为应力拉得越高越好(甚至超过110％)。这样,钢丝不是当即或浇灌时被拉断,就是白天拉好了,晚上被拉断。有的板即使钢丝不断,也会由于钢丝应力过高,板件反拱过大而出现裂缝,以致断裂。多孔板钢丝被拉断的原因大致有以下几方面: 一是钢丝本身抗拉强度不足,未达规定值。
When the prestressed porous plate is produced by the long line method, in order to prevent the occurrence of the phenomenon that the prestress value is insufficient due to the loss of prestress, a super drawing process is often used, and it is erroneously considered that the higher the stress is, the better (even more than 110%). In this way, the steel wire is not pulled off immediately or when it is poured, it is pulled during the day and it is broken at night. Some steel plates, even if they are continuous, may have cracks due to overstressing of the steel wire due to excessive stress in the steel wire, resulting in fractures. The reason why the perforated plate steel wire is broken is roughly the following: First, the tensile strength of the steel wire itself is insufficient, and the specified value is not reached.