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The difference between high-strength bolt friction type and pressure type connection

Update:07-02-2021
Summary:

High-strength bolt connection is to clamp the plate of […]

High-strength bolt connection is to clamp the plate of the connecting plate through the large tightening pretension in the bolt rod, which is sufficient to generate a large friction force, thereby improving the integrity and rigidity of the connection. When subjected to shear force, according to the design and The different force requirements can be divided into two types: high-strength bolt friction type connection and high-strength bolt pressure-bearing type connection. The essential difference between the two is that the limit state is different. Although they are the same type of bolts, they are calculated in terms of calculation methods, requirements, and scope All are very different.

In the shear design, the high-strength bolt friction type connection is the limit state when the external shear force reaches the maximum possible friction force provided by the bolt tightening force between the contact surfaces of the plate, which is to ensure that the internal and external shear force of the connection does not exceed during the whole use Maximum friction. The plates will not undergo relative sliding deformation (the original gap between the screw and the hole wall is always maintained), and the connected plates will be stressed as a whole by elasticity. In the shear design, the external shear force is allowed to exceed the maximum friction force in the high-strength bolt pressure-bearing connection. At this time, relative sliding deformation occurs between the connected plates until the bolt rod contacts the hole wall, and then the connection depends on the bolt rod Shaft shear and hole wall pressure and the friction between the contact surfaces of the plate jointly transmit force, and finally the shaft shear or hole wall pressure failure is regarded as the limit state of connection shear.

In short, friction-type high-strength bolts and pressure-bearing high-strength bolts are actually the same kind of bolts, it is just whether slippage is considered in the design. Friction-type high-strength bolts must not slide, and the bolts do not bear shear force. Once slipped, the design is considered to have reached a failure state, which is technically mature; pressure-bearing high-strength bolts can slide, and the bolts also bear shear force, and the final damage is equivalent to ordinary Bolt damage (bolt shearing or steel plate crushing).
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