Regarding high-strength screws, there are actually differences in planning and calculation methods. Conflict-type high-strength screws use sliding between plate layers as the load-bearing capacity limit; pressure-bearing high-strength screws use sliding between plate layers as the normal operating limit condition. Convergence destruction serves as a bearing capacity to limit the situation.

Conflict-type high-strength screws cannot fully exploit the potential of screws. In actual use, for very important structures or structures that are subjected to dynamic loads, especially when the load causes reverse stress, conflict-type high-strength bolts should be used. At this time, the unutilized screw potential can be used as a safe storage. In other places, pressure-bearing high-strength screws should be used to reduce the cost.

According to the construction process, it is divided into: torsion shear type high-strength screws and large hexagonal high-strength screws.

Large hexagonal high-strength screws belong to the high-strength grade of general screws, while torsion shear type high-strength screws are improved types of large hexagonal high-strength screws for better construction.

The construction of high-strength screws must be first tightened and then finally tightened. For the first tightening of high-strength screws, an impact-type electric wrench or torque-adjustable electric wrench must be used; and the final tightening of high-strength screws has strict requirements, and the final tightening of torsion shear type high-strength screws must be torsion shears. Torque-type electric wrenches must be used for final tightening torque-type high-strength screws.

The large hexagonal strong screw consists of a screw, a nut, and two washers. The torsion shear type high-strength screw consists of a screw, a nut, and a washer.

Several concepts about high-strength screws

According to the rules, bolts whose functional grade is above 8.8 are called high-strength bolts. Currently, the country only reaches M39. With regard to large-size standards, especially high-strength bolts with a length greater than 10 to 15 times, domestic production is still short-term.

From the perspective of strength level: high-strength screws are increasingly widely used. Two strength levels of 8.8s and 10.9s are commonly used, of which 10.9 is the majority. Generally, the bolt strength grade is low, generally 4.4, 4.8, 5.6 and 8.8.

From the perspective of force characteristics: high-strength bolts exert pretension and rely on conflicting forces to transmit external forces. Generally, bolts are connected by the shear resistance of the bolt rod and the pressure of the hole wall to transmit the shear force. The pretension force generated when the nut is tightened is very small, and its effect can be ignored. In addition to the high material strength of the high-strength bolt, it also exerts a large amount on the bolt. The pre-tension force causes the squeezing force to occur between the connecting members, so that there is a great conflict force perpendicular to the screw direction, and the pre-tension force, the anti-slip coefficient and the steel variety directly affect the bearing capacity of the high-strength bolts. According to the force characteristics, it is divided into pressure type and conflict type. The calculation methods of the two are different. High-strength bolts are of small standard M12, commonly used M16~M30, and the function of super-large standard bolts is unstable and should be used steadily in planning.