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一、提高张拉系数 K 值,以提高管的抗裂性按设计规范 TJ10-74的规定,预应力钢筋的张拉系数 K 取0.70～0.75。笔者认为那是指一般构件,特别是指建筑构件,一旦出现裂缝有采取补救措施的时间,绝对不允许发生脆断,不允许发生损害生命的危险事故。但对预应力管的要求与一般构件有所不同,前者在使用过程中绝对不允许出现裂缝,一旦裂缝出现就认为此管已破坏。所以,笔者认为在制管中可以提高张拉系数 K值,这样既提高管的抗裂性,又不影响管的使用寿命和使用价值。从安全角度考虑,提高张拉系数 K 值也是可行的。环筋张拉与纵筋张拉有所不同,
1. Raise the K value of the tension coefficient to improve the crack resistance of the pipe According to the design specification TJ10-74, the tension coefficient K of the prestressed steel is 0.70-0.75. The author believes that it refers to the general components, especially to the building components. Once the cracks have taken remedial measures, absolutely no brittle fracture is allowed, and no dangerous accidents that will damage lives are allowed. However, the requirement for the prestressed pipe is different from that of the general component. In the former, cracks are absolutely not allowed in the process of use. Once the crack appears, the pipe is considered damaged. Therefore, the author believes that the value of the tension factor K can be increased in the pipe system so that the crack resistance of the pipe can be improved without affecting the service life and value of the pipe. From the perspective of safety, it is also feasible to increase the K value of the tension factor. Tension between ring tendons and longitudinal tendons is different.