Prestressed concrete, in order to make up for the phenomenon of premature cracks in concrete, a prestress is applied to the concrete before the component is used (loaded), that is, in the tensile area of concrete, the steel bar is tensioned by artificial force, and the tensile area of concrete is prestressed by the retraction force of steel bar. This kind of stored prestress, when the member bears the tensile force generated by external load, first offsets the prestress in the concrete in the tensile area, and then makes the concrete stretch with the increase of load, limiting the elongation of concrete and delaying or preventing the occurrence of cracks, which is called prestressed concrete. There is no need to reserve pore channels and grouting, and the construction is simple, fast, low in cost and easy to popularize and apply.