Practical fastening method of high strength bolt in steel structure

1、 Torque method
In order to reduce the pre tightening force difference of high-strength bolts which are tightened first and then tightened, the ordinary wrench is generally used for initial tightening (the torque value is not less than 50% of the final tightening torque value) in the process of bolt connection and tightening in steel structure engineering, so that the steel plate overlaps and is disturbed, and then the constant torque wrench which can display the torque value is used for final tightening. The final tightening torque should be determined according to the relationship between the pre tightening torque and the pre tightening force (increase 5% - 10% after tightening to compensate for the relaxation effect), and the deviation during tightening shall not be greater than ± 10%.
2、 Angle method
In this method, the required preload is obtained by controlling the bolt strain (i.e., controlling the angle of the nut). The angle starts from the marking line of the initial tightening action, and then uses a long wrench (or electric or pneumatic wrench) to finally tighten 1 / 3-2 / 3 turns (120 ° - 240 °). The final tightening angle is related to the stack thickness and bolt diameter, which can be determined in advance.

3、 Screw off the end of the bolt
This method is suitable for torsional shear high strength bolts. First, tighten the bolt, and then cover the nut and the end of the bolt with two sockets of the special electric wrench. During operation, the large sleeve rotates forward to apply the tightening torque, while the small sleeve rotates in the opposite direction to apply the tightening torque. After tightening the bolt, screw off the plum head along the end cut.
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