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1. Common bolts, high-strength large hexagon head bolts, torsional shear type high-strength bolts and other fasteners are used for steel structure connection.
      2. The high strength large hexagon head bolt connection pair and torsional shear type high strength bolt connection pair should have torque coefficient and tightening force coefficient respectively.
The factory inspection report of fixed axial force (pretension) shall be attached with the box belt. When the high-strength bolt connection pair is used after storage for more than 6 months, the torque coefficient or tightening axial force test shall be conducted again according to relevant requirements, and it shall be used after it is qualified.
      3. The torque coefficient and tightening axial force (pretension) of high-strength large hexagon head bolt connection pair and torsional shear type high-strength bolt connection pair shall be re inspected respectively. The test bolts shall be randomly selected from the bolt batches to be installed at the construction site, and 8 sets of connection pairs shall be selected from each batch for re inspection.
     4. The surface hardness test shall be carried out for the high-strength bolts of the steel grid structure with bolt ball joints and span of 40m and above, the surface hardness of the high-strength bolts of grade 8.8 shall be hrc21 ~ 29, the surface hardness of the high-strength bolts of grade 10.9 shall be hrc32 ~ 36, and there shall be no cracks or damage.
5. When ordinary bolts are used as permanent connecting bolts, and there are requirements in the design documents or doubts about their quality, the minimum tensile load of bolts shall be rechecked, and 8 bolts of each specification shall be sampled.