1. Classification according to the receiving force: pressure-bearing high-strength nuts, friction-type high-strength nuts (1) Friction-type high-strength nuts: its ultimate bearing capacity is rolling between plates, and the development potential of bolts cannot be rubbed High-strength nuts are sufficient for full play. (2) Pressure-bearing high-strength nut: its limit condition is rolling between plates, and the limit condition of bearing capacity is invalid connection. 2. Classified according to the operation method: large hexagonal high-strength nuts, torsional shear type high-strength nuts (1) Large hexagonal high-strength nuts: its compressive strength is relatively high compared to ordinary screws. (2) Torsional shear-type high-strength nut: In order to achieve better and faster application effects, it is improved on the basis of large hexagonal high-strength nuts. What high-strength nuts have in common with ordinary bolts is the buckle structure and shape. There are also differences between them. Generally, the transmission of bolt shear stress requires the bending capacity and the bearing capacity of the rod body. When the nut is tightened, the pre-tightening force of the bolt is very small, and its influence is not considered. The high-strength nut connection is intentionally added with a large torque bolt to facilitate the contact surface of each part of the connection will cause extrusion pressure, so there is a very large friction force to the spiral vertical, and the friction of the connection shear stress transfer force. For high-strength nuts, its pre-tensioning method is to tighten the nut, the method is the corner method and the torque method, and the method of twisting the high-strength nut to control the pre-tightening force is to twist the tail end of the bolt for operation . In the case of actual engineering construction, for some unique structures (structures bearing dynamic loads, very critical structures), especially for reverse pressure caused by adverse effects of loads, friction-type high-strength nuts should be selected. At this time , The potential difference of the unused high-strength nut can be used as a safety reserve. In addition, pressure-bearing high-strength nuts should be selected, and its advantage is to reduce enterprise costs.