Small Knowledge of Steel Structure High Strength Bolt Tightening

Small Knowledge of Steel Structure High Strength Bolt Tightening

Practical tightening methods for high-strength bolts in steel structures

With the continuous development of science and technology, the shape and structural form of steel structures are becoming increasingly complex, bringing new challenges to the installation of steel structures. The fastening of high-strength bolts in steel structures is an important task. How to do a good job in tightening high-strength bolts.

1、 Torque method

In order to reduce the pre tightening force difference of high-strength bolts that are tightened first and then tightened, ordinary wrenches are 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 structural engineering, so that the steel plates overlap and are disturbed, and then a constant torque wrench that can display the torque value is used for final tightening. The final tightening torque value should be determined based on the relationship between the pre tightening torque and the pre tightening force (increase by 5% -10% after tightening to compensate for the relaxation effect), and the deviation during tightening should not exceed ± 10%.

2、 Angle method

In this method, the specified preload is obtained by controlling the bolt strain (i.e. controlling the angle of the nut). Starting from the marked line of the initial tightening action, use 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 layer thickness and bolt diameter, and can be determined in advance.

3、 Unscrew the end of the bolt

This method is suitable for torsion shear type high-strength bolts. Tighten the bolts first, and then cover the nut and bolt end with the two sockets of a special electric wrench. During the 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 bolts, unscrew the plum blossom head along the end notch.