Key points of work control of steel structure fastener connection engineering

1. During the inspection of steel structure production, the anti slip coefficient test of high-strength bolt connection friction surface shall be witnessed, and the anti slip coefficient shall meet the design requirements; It shall be noted that the sand blasting of the connecting friction surface of the steel structure shall meet the quality requirements of the test plate that has passed the anti slip coefficient test of the connecting friction surface.

The anti slip coefficient of the friction surface of high-strength bolt connection is related to the type of steel, the type of sand used for surface treatment, wind pressure, sand blasting time and the corrosion degree of the friction surface before the test. Therefore, the steel structure manufacturer must carry out anti slip coefficient test on representative. The treatment of the test plate shall be consistent with the actual production. The specification requires that a group of tests shall be conducted for every 2000 tons of steel structure, and each group of tests shall have six pairs of test plates, of which three pairs shall be tested before the production of steel structure, and the other three pairs shall be retested before the installation of high-strength bolts of steel structure, so as to verify that the anti slip coefficient of friction surface of high-strength bolt connection is still within the range of specification or design requirements. In the production of steel structure, if the pretreatment site of friction surface connected by high-strength bolts is changed or the treatment method is changed, the anti slip coefficient test must be carried out again.

2. The installation quality of high-strength bolt connection friction surface and the tightening degree of high-strength bolt shall be inspected by no less than 10% respectively. The torque wrench shall be calibrated. The torque wrench shall be rechecked before and after each shift, and the inspection records shall be made. The supervisor shall check the final tightening torque together with the quality inspection of the construction unit within 1h and 48h after the final tightening. At the same time, check that the exposed bolt threads shall be 2-3 threads (10% of the bolt threads are allowed to be exposed by 1 thread or 4 threads).

The construction unit shall prepare two torque wrenches, one construction wrench with error within 5%, and the other as testing wrench with error within 3%. The construction wrench shall be tested before and after each shift. High strength bolts shall not be used as positioning bolts, and the initial tightening to final tightening of high strength bolts shall be completed within 24h. The final tightening torque of high-strength bolts shall be tested with a testing wrench.

3. If the anti slip coefficient test of high-strength bolt connection friction surface is qualified, the quality certificate of high-strength bolt is qualified and effective, the final tightening torque inspection is qualified, and the supervisor is qualified, the fastener connection is qualified.