Connection And Installation Of Friction-type High-strength Bolts For Steel Structures

(1) Preparations before installation

(2) Choose qualified bolts, nuts and washers. The guarantee period of the torque coefficient of the connection pair is six months from the date of delivery.

(3) Bolts, nuts, and washers have the following conditions as unqualified products and are prohibited from use.

a. The source (manufacturing plant) is unknown;

b. Unknown mechanical properties;

c. The torque coefficient k is unknown;

d. Those with cracks, scars, burrs, bends, rust, thread wear, oil stains, wetted with water or defective;

e. Those without performance test report;

f. Mixed with other batch number bolts;

g. Bolts with insufficient length, that is, the head of the bolt does not show the end face of the nut after tightening. Generally, the length of the end face of the extended nut is 2~3 threads.

h. The torque coefficient of the connecting pair exceeds the guarantee period.

Pay special attention to waterproofing during transportation and storage.

(4) Before the construction of large hexagon head high-strength bolts, the torque coefficient of the high-strength bolt connection pair should be re-examined according to the factory approval. 8 sets of each batch are re-inspected. The average value of the torque coefficients of the 8 sets should be in the range of 0.110~0.150. The deviation should be less than or equal to 0.010. The re-inspection method of the torque coefficient is carried out in accordance with the provisions of GB50205 "Code for Acceptance of Construction Quality of Steel Structure Engineering". After the test, the high-strength bolts should be installed in a short time.