Several key points for steel structure installation, including friction coefficient, torque coefficient, initial tightening torque, and final tightening torque. These are all very important points when installing steel structures. This will affect the installation quality of steel structures, so these key points need to be understood. What are the specific situations?
Friction coefficient: where F is the initial slip force generated by the anti slip test, nf is the number of friction surfaces, and is the sum of the high-strength bolt tightening pre tension test values corresponding to F.
Torque coefficient: d is the nominal diameter of high-strength bolts (mm), m is the applied torque value (N ± M), and p is the bolt preload force. The high-strength large hexagonal bolt connection grade 10.9 must ensure that the average torque coefficient K is between 0.110 and 0.150. Its standard deviation should be below 0.010.
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 bolts tightened successively. High strength bolts should be tightened at once to achieve an initial tightening force of 60% to 80% of the standard axial force.
Final tightening torque: The torque used to tighten high-strength bolts is the final tightening torque. Considering the loss of various pre stresses, the final tightening torque is generally 5% to 10% greater than the torque value calculated according to the design pre tension theory.
