For structures subjected to external load before, on the tension bar module applied to the pre compressive stress, improve the component stiffness and cracks appeared at a later time, increase the durability of components. For the mechanical structure, its meaning is in advance to produce stress and its benefits is can improve the structure rigidity, reduce vibration and elastic deformation that can significantly improve the tensile module of elastic strength, so that the original resistance stronger.

Before the structure is subjected to external load, the compressive stress is applied to the tension zone under the action of external load to improve the performance of the structure, which is called the prestressed structure.

As the barrel, using iron or bamboo hoop tight barrel wall before installing water, edge produces a circumferential compressive stress on the barrel wall, if the applied stress exceeds the water pressure caused by tensile stress, the barrel will not crack Water Leakage. In the pool round on effect of prestressed hoop like barrel the same. Similarly, before the load of flexural members added to prestressed component will produce a generation and load deformation and reverse deformation, must first load the load and deformation of the opposite direction along the offset component before he can continue to deform, the component along the load direction so deformed. As for members of prestressed, exerted a protective.