Precautions for steel structure installation

Precautions for steel structure installation: 1. Torque coefficient: where d is the nominal diameter of the high-strength bolt (mm), M is the applied torque value (N﹒M), and P is the bolt preload. Grade 10.9 high-strength hexagonal bolt connections must ensure that the average torque coefficient K is 0.110 to 0.150. Its standard deviation should be less than or equal to 0.010. 2. Final tightening torque: the final tightening torque of the high-strength bolt is the final tightening torque. Considering the loss of various prestresses, the final torque is generally 5% to 10% larger than the theoretically calculated torque value based on the design pretension. 3. Friction coefficient: where F is the force that causes the initial slip of the specimen 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 pretension corresponding to F. 4. Initial tightening torque: In order to reduce the influence of the deformation of the steel plate during the bolt tightening process, secondary tightening can be used to reduce the mutual influence between successively tightened bolts. The high-strength bolts should be screwed for the first time, so that their axial force should reach 60% to 80% of the standard axial force.