(1) Types and uses of ordinary bolts
According to the difference in shape, ordinary bolts can be divided into three types, namely hexagonal bolts, stud bolts and anchor bolts.
① Hexagon bolts: According to the quality and products, they are divided into three grades: A, B, and C.
Grade A-refined bolts;
Grade B-semi-refined bolts;
Grade C-crude bolts.
The connection part of the structure needs to transmit a large shear force. A and B grade bolts can be used for installation. The C grade bolts are suitable for temporary fixation in the installation of steel structures.
② Stud bolts: Also called studs, they are mostly used to connect thick plates or where it is inconvenient to use hexagon bolts.
③ Anchor bolts: There are general anchor bolts, right angle anchor bolts, hammer head bolts and anchor anchor bolts. General anchor bolts, right angle anchor bolts and hammer head bolts are pre-buried in the foundation before concrete pouring. It is used to fix the steel column; the anchor bolt is a kind of anchor bolt that is installed and grouted to fix the hole after drilling the hole on the formed concrete foundation.
⑵ Construction of ordinary bolts
① Connection requirements:
1) A flat washer should be placed under the bolt head under the nut. Up to 2 washers under the nut, up to 1 washer under the bolt head
2) The bolt heads and nuts should fit closely with the surface of the structural member and the washer.
3) For bolt connection on the inclined surface, place the inclined washer to level it up.
4) For bolts with dynamic loads or important parts, spring washers are required.
5) The length of the bolt extending from the nut should be greater than the length of two complete threads.
② Tightening axial force
The bolts should be tightened from the center and tightened symmetrically; for large joints, double tightening is used, that is, the "twice tightening method". The tightening axial force during screwing should not exceed the corresponding regulations. The quality of permanent bolt tightening is inspected by hammering or with a torque wrench. The bolts are required to be free from flutter and deviation. The authenticity of tightening is checked with a feeler gauge. The height difference (roughness) of the butt surface should not exceed 0.5mm.