Stress degree of torsion shear bolt

High strength torsional shear bolts exert pre tightening force and transmit external force through friction. The shear force is transmitted through the bolt and the hole wall. The pre tightening force produced by tightening the nut is very small and can be ignored. In addition to material strength, high strength torsion bolts are also very high. In addition, a large pre tension is applied on the bolt, which leads to the extrusion pressure between the connecting members and the huge friction force perpendicular to the screw direction. In addition, preload, anti slide coefficient and steel grade directly affect the bearing capacity of high strength torsional shear bolts. According to the characteristics of force and friction, it can be divided into types. The two calculation methods are different.

The minimum specification of steel structure torsion shear bolt is M12, commonly used m16m30. The performance of super large torsional shear bolt is unstable, so it should be used carefully in design. The difference between high-strength torsional shear bolt friction type connection and pressure bearing type connection is that the high-strength torsional shear bolt connection uses the torsional shear bolt rod to clamp the connecting plate with a larger tightening pre tightening force, which can generate large friction force and improve the integrity and stiffness of the connection. When the shear force is applied, according to different design and mechanical requirements, the high-strength torsional shear bolt connection has the advantages of high-strength torsional shear bolt connection, which can be divided into high-strength shear bolt friction connection and high-strength torsional shear bolt compression connection. Their essential difference lies in the difference of limit states. Although they are the same kind of torsion bolt, there are great differences in calculation methods, requirements and application scope.

In the shear design, the friction connection of high-strength torsional shear bolt is the limit state. When the external shear force reaches the maximum possible friction force, the tightening force of the torsional shear bolt between the indirect contact surfaces of the plate is obtained. In other words, ensure that the internal and external shear forces of the connector do not exceed the maximum friction force over the life of the connector. There is no relative slip deformation (the clearance between screw and hole wall is always maintained), and the connecting plate is under elastic force. In the shear design, the external shear force is allowed to exceed the maximum friction force in the load-bearing connection of high-strength torsion bolt, and the relative slip deformation occurs between the connecting plates until the torsion shear bolt rod contacts the hole wall. From then on, the connection depends on the shear force of the bolt body, the pressure of the hole wall and the friction force between the contact surfaces of the plate. Finally, the ultimate shear state of the connector is the shear failure of the member or the hole wall pressure. In a word, the friction type high-strength torsional shear bolt and the bearing high-strength torsional shear bolt are actually the same kind of torsion bolt, but whether to consider the slip in the design.

   friction type high-strength bolt can not slide, the bolt does not bear shear force, once sliding, the design will reach failure state, which is relatively mature in technology; compression type high-strength bolt can slide, bolt also bears shear force, ultimate failure is equivalent to failure shear failure of ordinary bolt (bolt) or steel plate crushing).