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由于混凝土结构的抗拉强度低,在钢筋混凝土构件中采用钢筋来帮助混凝土承受拉力。但是,混凝土的极限拉应变很小,超过极限拉应变值,混凝土就要开裂。为避免混凝土结构裂缝过早出现,避免混凝土产生过宽的裂缝,保证结构的耐久性,充分发挥材料的强度,可增大钢筋混凝土构件的截面尺寸,或者增加钢筋用量来控制构件的裂缝和变形。但是,这样做既不经济,又不适用大跨结构和某些特殊高层建筑对结构功能的要求。为了解决这一问题,可采用预应力混凝土结构。
Due to the low tensile strength of concrete structures, steel bars are used in reinforced concrete members to help concrete withstand tensile forces. However, the ultimate tensile strain of concrete is small, beyond the ultimate tensile strain value, the concrete will crack. In order to avoid premature cracks in concrete structures, to avoid excessive cracks in concrete to ensure structural durability, give full play to the strength of the material, can increase the cross-sectional size of reinforced concrete members, or increase the amount of steel to control the cracks and deformation components . However, this is neither economical nor suitable for the structural functional requirements of long-span structures and some special high-rise buildings. In order to solve this problem, prestressed concrete structures can be used.