1. When installing high-strength bolts, the high-strength bolts should freely penetrate into the holes and must not be forcibly knocked. The washer of the torsion-shear type high-strength bolt should be installed on the side of the nut. The chamfered side of the washer hole should be in contact with the nut and must not be installed upside down (the washer of large hexagonal head and high-strength bolts should be installed on the side of the bolt head and the nut. The chamfered side of the washer hole should be in contact with the bolt head and must not be installed backwards).
2. When the bolt cannot penetrate freely, gas cutting is not allowed to enlarge the hole. Instead, a reamer must be used to ream the hole. When repairing the hole, the board layers must be kept close to prevent iron filings from entering the seam of the board. After reaming, use a grinder to clear the hole. Remove edge burrs and remove iron filings.
3. The bolts should be inserted in the same direction. After inserting the high-strength bolts and tightening them with a wrench, remove the temporary bolts and replace them with high-strength bolts. High-strength bolts must not be installed on rainy days, and the friction surface should be dry.
Tightening of high-strength bolts: must be done in two steps. Initial tightening: The initial tightening is tightened to 60% to 80% of the standard axial force of the bolt (ie, the design pretension force). The initial tightening torque value shall not be less than 30% of the final tightening torque value. Final tightening: During final tightening, the torsion-shear type high-strength bolts should have their plum blossom chucks removed. In order to ensure that all bolts in the bolt group are stressed evenly, the initial and final tightening should be performed in a certain order.
1. General joints: The bolts should be tightened sequentially from the middle to the outside.
2. Proceed from the joint's stiffest point toward the unconstrained free end.
3. Spread from the middle of the bolt group to the surroundings.
The initial tightening wrench should be able to control the torque, and the bolts that have been initially tightened should be marked for confirmation. In order to prevent missed tightening, the high-strength bolts installed on the same day should be finally tightened on the same day.
All high-strength torsion-shear bolts should be tightened by removing all the plum blossom chucks at the end, and no omissions are allowed.
When the special wrench cannot be used, the torsion-shear type high-strength bolts should be constructed using the torque method according to the large hexagonal head high-strength bolts. After the final tightening is completed, it is advisable to use a small hammer weighing 0.3 to 0.5kg to check for leakage and under-tightening. If any under-tightening or missing tightening is found, the screws should be re-tightened; over-tightening should be replaced. During inspection, the nut should be retracted 30° to 50°, then tightened to the original position, and the final tightening torque value should be measured. The deviation should not be greater than ±10%. Those that have passed the final tightening should be marked.
