Fastening knowledge of steel structure high strength bolt

Practical fastening method of high strength bolt in steel structure

With the continuous development of science and technology, the shape and structural form of steel structure become more and more complex, which brings new challenges to the installation of steel structure. It is an important work to fasten high strength bolts of steel structure. How to fasten the high strength bolt.

1、 Torque method
       In order to reduce the pre tightening force difference of high-strength bolts which are tightened first and then tightened, in the process of bolt connection and tightening of steel structure engineering, the ordinary wrench is generally used for initial tightening (the torque value is not less than 50% of the final tightening torque value), so that the steel plates are overlapped and disturbed, and then the constant torque wrench which can display the torque value is used for final tightening. The final tightening torque value shall 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 specified preload is obtained by controlling the bolt strain (i.e. the angle of the control 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 turn (120 ° - 240 °). The final tightening angle is related to the lamination thickness and bolt diameter, which can be determined in advance.

3、 Screw off the end of the bolt
       This method is suitable for high strength bolts of torsion shear type. Tighten the bolt first, then cover the nut and the end of the bolt ring head with two sockets of the special electric wrench. During operation, the large sleeve rotates in the forward direction to apply tightening torque, while the small sleeve rotates in the reverse direction to apply tightening torque. After tightening the bolt, unscrew the plum head along the end cut-out.