What are the key points of steel structure installation?

　　(1) Friction coefficient: F is the force that causes the initial sliding of the test piece measured by the anti sliding test, NF is the number of friction surfaces, and is the sum of the measured values of the tightening pretension of the high-strength bolt corresponding to F. 

　　(2) Torque coefficient: where D is the nominal diameter of high-strength bolt (mm), M is the applied torque value (n).M), P is the bolt pre tightening force.The average value of torque coefficient K must be 0.110-0.150 for grade 10.9 high strength large hexagon bolt connection.The standard deviation shall 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 successively tightened bolts.The first tightening of high-strength bolt is initial tightening, so that its axial force should be 60% – 80% of the standard axial force.

　　(4) Final tightening torque: the final tightening torque of high-strength bolt is final tightening torque.Considering the loss of various prestressing forces, the final tightening torque is generally 5% – 10% larger than that calculated theoretically according to the design pretension.