We all know finishing steel nut connections with rolling screw thread steel with special wrench tighten the nut, the pretension of reinforcement produce huge and out of control, through the nut and plate, connections also has a force of the same size. Under pressure, connected surface will create greater friction, it is clear that as long as the axial force is less than the friction components will not slip, the connection will not be damaged, this is the nut connecting the principle.
However, if the bars and nuts their spacing is too large, there is no case of prestressed, nut will slide and affect the quality of engineering. Therefore, nut and spacing of reinforcement is very important.
In short, rolling steel nut connection is by friction between the contact surfaces to prevent it from sliding to make enough friction on the contact surface, it is necessary to improve the component clamping force and increase the friction coefficient of component contact surfaces. Clamping force between the components is fulfilled by placed on the rolling rebar pretension.