The degree of stress on torsional shear bolts
The degree of stress on torsional shear bolts
High strength torsional shear bolts apply pre tightening force and transmit external force through friction. Shear force is transmitted through bolts and hole walls. The pre tightening force generated by tightening the nut is very small and can be ignored. In addition to material strength, high-strength torsional bolts are also very high. In addition, applying a large pre tension force on the torsion shear bolt causes compression pressure between the connecting components, resulting in a huge frictional force perpendicular to the direction of the screw. In addition, the preload, anti slip 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. These two calculation methods are different.
The minimum specification of steel structure torsion shear bolts is M12, commonly used as m16m30. The performance of super large torsional shear bolts is unstable and should be used with caution in design. The difference between high-strength torsional shear bolt friction type connection and pressure bearing type connection is that high-strength torsional shear bolt connection is achieved by clamping the connecting plate with a large tightening pre tightening force through the torsional shear bolt rod, which is sufficient to generate a large amount of friction and improve the integrity and stiffness of the connection. When applying shear force, according to different design and mechanical requirements, 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 in limit states. Although they are the same type of torsional bolts, there are significant differences in calculation methods, requirements, and scope of application.
In shear design, the frictional connection of high-strength torsional shear bolts is the limit state. When the external shear force reaches the maximum possible frictional force, the tightening force of the torsional shear bolts between the indirect contact surfaces of the plate is determined. In other words, ensure that the internal and external shear forces of the connector do not exceed the maximum friction force throughout the entire service life of the connector. There is no relative slip deformation (always maintaining the gap between the screw and the hole wall), and the connecting plate is subjected to elastic force. In shear design, in high-strength torsional bolt bearing connections, external shear force is allowed to exceed the maximum friction force, causing relative sliding deformation between connecting plates until the torsional shear bolt rod contacts the hole wall. From then on, the connection depends on the shear force of the bolt body, the pressure on the hole wall, and the friction force between the plate contact surfaces. Finally, the ultimate shear state of the connector is the shear failure of the member or the pore wall pressure. In short, friction type high-strength torsional shear bolts and pressure bearing high-strength torsional shear bolts are actually the same type of torsional bolt, but whether sliding is considered in the design.
Friction type high-strength bolts cannot slide and do not withstand shear forces. Once they slide, the design will reach a failure state, which is relatively mature in technology; Compression type high-strength bolts can slide, and the bolts also bear shear force. The ultimate failure is equivalent to the failure shear failure or steel plate crushing of ordinary bolts (bolts).
