Simple Understanding Of Steel Structure Bolt Parameters

We specialize in the production of steel structural bolts and have accumulated many years of experience in steel structural bolts. We provide hexagonal head bolt connection pairs (GB1228) for steel structures in stock, with each connection pair containing one bolt, one nut, and two washers. The torsion shear high-strength bolt connection pair (GB3632) for steel structures includes a screw. A nut and a washer are used to facilitate the operation of the steel structure. The high-strength torsion shear bolt connection pair is actually an improved version of the steel structure's large hexagonal bolt connection pair. The main advantage is that the construction is simpler than that of the large hexagonal bolt, and the tail end of the plum blossom head can be directly screwed off using an electric wrench. Moreover, the inspection and construction are very convenient. Generally, visual inspection is required to confirm that the plum blossom head has been screwed off.

(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 pre tightening force of the bolt. The high-strength hexagonal bolt connection of grade 10.9 must ensure an average torque coefficient K of 0.110~0.150. Its standard deviation should be less than or equal to 0.010.
(2) Friction coefficient: where F is the force measured in the anti slip test that causes the initial slip of the specimen, nf is the number of friction surfaces, and is the sum of the measured values of the tightening pre tension of the high-strength bolt corresponding to F.
(3) Initial tightening torque: In order to reduce the impact of steel plate deformation during bolt tightening, secondary tightening can be used to reduce the mutual influence between bolts tightened sequentially. The first tightening of high-strength bolts is the initial tightening, so that their axial force should reach 60% to 80% of the standard axial force.
(4) Final tightening torque: The final tightening torque used for high-strength bolts is the final tightening torque. Considering the loss of various prestressing forces, the final tightening torque is generally 5% to 10% higher than the torque value calculated theoretically based on the designed prestressing force