Bolt arrangement and other structural requirements

1. Arrangement of bolts

The arrangement of bolts on the components should be simple, uniform, neat and compact, usually divided into two forms: parallel and staggered (below). The parallel arrangement is relatively simple and tidy, and the size of the connecting plate used is small, but due to the existence of bolt holes, the cross-section of the member is weakened greatly. Staggered arrangement can reduce the weakening of the cross-section of bolt holes, but the arrangement of bolt holes is not as compact as the parallel arrangement, and the size of the connecting plate is larger.

Arrangement of bolts (rivets) on steel plate

The arrangement of bolts on the components should meet the requirements of force, structure and construction:

(1) Force requirements: If the end distance of the bolts in the force direction is too small, the steel may be sheared or torn. If the bolt distance and line distance of each row are too small, the components may be damaged along the broken line or straight line. For compression members, when the bolt distance along the acting direction is too large, the phenomenon of bulging and opening between the connected plates is prone to occur.

(2) Structural requirements: The middle moment and edge distance of the bolts should not be too large, otherwise the steel plates cannot be closely attached, and moisture invades the gaps and the steel is corroded. (Guide: Detailed description of main geometric parameters of self-tapping and self-drilling threads)

(3) Construction requirements: ensure a certain space to facilitate turning the bolt wrench to tighten the nut.

According to the above requirements, the maximum and minimum allowable distances of bolts (or rivets) are specified, see the table. The spacing of bolts arranged along the length of the section steel shall not only meet the requirements of Table 3.5.1, but also meet the requirements of Appendix 10 bolt line spacing. Table bolt or rivet maximum and minimum allowable distance

Note: 1d0 is the hole diameter of the bolt or rivet, and t is the thickness of the outer thinner plate.

2 The maximum spacing of bolts or rivets between the edge of the steel plate and rigid components (such as angle steel, channel steel, etc.) can be adopted according to the value in the middle row.

2. Other structural requirements for bolts

In addition to meeting the allowable distance of the bolt arrangement mentioned above, the bolt connection should also meet the following structural requirements according to different situations:

(1) In order to make the connection reliable, the number of permanent bolts should not be less than two for each rod at the node and one end of the splicing joint. However, according to practical experience, a bolt can be used for the end connection of the composite member.

(2) Double nuts or other effective measures to prevent loosening of nuts should be adopted for ordinary bolt connections that directly bear dynamic loads. For example, using spring washers, or welding nuts or screws.

(3) Since there is a large gap between the C-level bolt and the hole wall, it should only be used for the connection under tension along the rod axis. In the secondary connection of the static load bearing structure, the connection of the detachable structure and the installation connection of the temporary fixed member, the C-level bolt can also be used for shearing. However, in important connections, such as the connection between the upper flange of the brake beam or the crane beam and the column, because the horizontal supporting reaction force of the brake beam is transmitted, and the repeated dynamic load is applied at the same time, the C-level bolts shall not be used. The connection between the column support and the column, and the connection of the lower flange of the crane beam at the support between the columns, should be given priority to using high-strength bolts due to the repeated horizontal braking force and the jamming force.

(4) The end plate (flange plate) in the bolt connection that is tensioned along the rod axis should be appropriately strengthened (such as adding stiffeners) to reduce the disadvantage of the prying force on the tensile bearing capacity of the bolt influences.

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