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The high-strength bolt connection is to clamp the plates of the connecting plate through a large tightening pre-tension force in the bolt rod, which is enough to generate a large friction force, thereby improving the integrity and rigidity of the connection. According to different force requirements, it can be divided into high-strength bolt friction connection and high-strength bolt pressure-bearing connection. The essential difference between the two is that the limit state is different. Both are very different.
In the shear design, the high-strength bolt friction connection is the limit state where the external shear force reaches the possible maximum friction force provided by the bolt tightening force between the contact surfaces of the plates, that is, to ensure that the internal and external shear force of the connection does not exceed maximum friction. There will be no relative sliding deformation of the plates (the original gap between the screw and the hole wall is always maintained), and the connected plates are stressed as a whole according to elasticity.
In the shear design, the allowable external shear force exceeds the maximum friction force in the high-strength bolt pressure-bearing connection. At this time, the relative sliding deformation occurs between the connected plates until the bolt rod contacts the hole wall. After that, the connection depends on the bolt rod. The shearing of the shaft, the pressure of the hole wall and the friction between the contact surfaces of the plates jointly transmit the force, and finally the shearing of the shaft or the failure of the pressure of the hole wall is taken as the limit state of the connection shear.
In short, friction-type high-strength bolts and pressure-type high-strength bolts are actually the same kind of bolts, but whether the design considers slippage or not. Friction-type high-strength bolts must not slide, and the bolts do not bear shear force. Once they slip, the design considers that they have reached a destructive state, which is relatively mature in technology; pressure-bearing high-strength bolts can slide, and the bolts also bear shear force, and the final failure is equivalent to that of ordinary bolts. Bolt damage (bolt shearing or steel plate crushing).