In our common steel structure facilities, we usually need to pay attention to the following 4 installation points, and we cannot be careless. (1) Friction coefficient: F is the force that causes the specimen to produce initial slip measured by the anti-slip test, nf is the number of friction surfaces, and is the sum of the measured values of the high-strength bolt tightening pre-tension corresponding to F. (2) Torque coefficient: d is the nominal diameter of the high-strength bolt (mm), M is the applied torque value (N﹒M), and P is the bolt pre-tightening force. The connection of 10.9 grade high-strength large hexagonal bolts must ensure that the average value of the torque coefficient K is 0.110~0.150. Its standard deviation should be less than or equal to 0.010. (3) Initial tightening torque: In order to reduce the influence of steel plate deformation during bolt tightening, secondary tightening can be used to reduce the mutual influence between the bolts tightened successively. The first tightening of high-strength bolts is the initial tightening, and its axial force should reach 60%~80% of the standard axial force.
(4) Final tightening torque: The torque used for the final tightening of high-strength bolts is the final tightening torque. Considering the loss of various prestresses, the final tightening torque is generally 5% to 10% greater than the torque value calculated theoretically based on the designed pretension.
