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四、预加应力的方法混凝土获得预加压力的方法甚多。有用蒸汽或电流的热张法,将钢筋加热,使它伸长而锚仕其两端,待冷却后发生预应力。有用膨胀水泥制造混凝土的自张法,由于混凝土在硬结过程中的体积膨胀与钢筋间的粘结力使钢筋受拉,同时混凝土中也逐渐形成预压力。此外,还有其他许多方法,但最有效的主要方法,是用预加钢筋以拉力来使混凝土受压。此时钢筋内拉力被混凝土的压力所平衡。根据钢筋张拉在混凝土浇灌时间的先后程序,用预拉钢筋来造成混凝土预压力的方法,可分先张与后张两个基本方法。 1.先张法即在浇灌混凝土之前将钢筋张拉。由张拉钢筋所引起的反力,传到特制的传力架,在混凝土浇
Fourth, the method of pre-stress Concrete pre-pressure to obtain a lot of ways. Use steam or current heat tension method, the steel heating, make it stretch and anchorage at both ends, to be pre-stressed after cooling. Expansion of cement used to make concrete self-Zhang method, due to the volume of concrete in the hardening process of expansion and reinforcement of the bond between the tensile strength of steel, while the concrete is also gradually formed pre-pressure. In addition, there are many other ways, but the most effective and primary method is to use pre-tensioned steel to pull the concrete to compress it. At this point the tension within the steel is balanced by the pressure of the concrete. According to the tensioning of steel in the concrete pouring time of the procedure, with pre-tensioned concrete to cause pre-pressure method can be divided into pre-Zhang and Zhang after the two basic methods. 1. Pretension method that is before pouring the concrete tension. The reaction force caused by the tension bar spreads to a special power-driven frame and is poured on the concrete