When the high-strength bolts are installed, the nuts are tightened, so that the screw produces pre-tension and presses the contact surface of the component, and the friction of the contact surface is used to prevent the connecting plates from sliding each other, so as to achieve the purpose of transmitting external force.
 
High-strength bolts are divided into friction-type high-strength bolts and pressure-bearing high-strength bolts according to the force transmission mechanism. These two bolts have basically the same structure and installation. However, friction-type high-strength bolts transmit loads by friction, so the difference between the screw and the screw hole can reach 1.5-2.0mm. The force transmission characteristic of pressure-bearing high-strength bolts is to ensure that under normal use, the shear force does not exceed the friction force, which is the same as that of friction-type high-strength bolts. When the load increases again, relative slippage will occur between the connecting plates, and the connection relies on the shear resistance of the screw and the pressure of the hole wall to transmit force, which is the same as that of ordinary bolts, so the difference between the screw and the screw hole is slightly smaller, 1.0-1.5mm.
 
Compared with pressure-bearing high-strength bolts, friction-type high-strength bolts have less deformation, lower bearing capacity, and better fatigue resistance and dynamic load resistance. The pressure-bearing high-strength bolt connection has a high bearing capacity, but has a large shear deformation, so it is generally only used for connections in structures that bear static loads and indirectly bear dynamic loads.