1) Friction coefficient:, where F is anti-slip tests measured to generate the initial specimen slip force, nf the number for the friction surface, with F the corresponding high-strength bolts fastening the measured value and the pre-tension .
(2) Torque coefficient:, where d is high-strength bolt nominal diameter (mm), M the applied torque value (N.M), P for the bolt preload. 10.9 High-strength hexagon bolt connection must ensure that the average torque coefficient K is 0.110 ~ 0.150. Its standard deviation should be less than equal to 0.010.
(3) The first screw torque: In order to reduce the bolts fastening the process of steel plate deformation can be used to reduce successively the second tightening bolts tightening the interaction between. High-strength bolts screwed to the beginning of the first screw, axial force to axial force should meet the standard of 60% ~ 80%.
(4) The final screw torque
: high-strength bolts used in the final tightening torque for terminal screw torque. Consider a variety of prestress losses, the final screw torque is generally poorer than the pre-tension is designed to make theoretical calculations of the torque value of large 5% ~ 10%.