Introduction to Torsional Shear Bolts

Introduction to Torsional Shear Bolts

The calculation of torsional shear bolt connections can be divided into two types based on different failure criteria: friction type and pressure type. These are two calculation models or two failure criteria for the same connection, rather than two types of friction and pressure for high-strength bolts.

There are two types of commonly used high-strength bolts, which are divided into grade 10.9 and grade 8.8 based on material. Although there is currently a third level 9.8, the application has not yet become widespread. Whether it is grade 10.9 or 8.8 high-strength bolts, friction or pressure type connections can be used. The types of high-strength bolts and connectors are two concepts in this sense. Many people believe that high-strength bolts can be divided into friction type and pressure type, with each class having levels 10.9 and 8.8. Some textbooks and reference materials are not clear about this, and this concept is incorrect.

When the connection is subjected to external shear V, there will be a trend of relative sliding. The friction between the steel plates is caused by the extrusion pressure P, and an increase in N=P will cause friction between the steel plates. V will also increase N until the maximum Stiction, I. E. Reach the OA segment of the curve. If V continues to increase, the maximum Stiction will be overcome, and the relative slip between steel plates will begin to occur until the bar contacts the hole wall (section BC). The maximum Stiction is slightly greater than the maximum dynamic friction, which can be considered equal in engineering applications. Starting from point C, when the external force increases the pin action of the bolt rod, the bearing capacity of the connection continues to increase to its maximum value at point D, and the bearing capacity of the node also has a decreasing stage of DE. After failure. Through the above analysis, we can see that the stress and failure of high-strength bolt connections have their own characteristics, similar to the uniaxial tension of steel. If the damage sign is to overcome the maximum Stiction, the connection is friction type, and the bearing capacity is the maximum Stiction. In fact, there is no physical damage to this connection. If the failure criterion is relaxed and the pin action of the bolt rod is allowed to continue, the connection is of the pressure bearing type. At this point, the force on the connecting bolt is equivalent to that of an ordinary bolt, and its failure mode mainly manifests as shear failure of the bolt rod, hole wall pressure failure, or steel plate tension fracture.