Steel Connections – Bolts, Rivets, Welding

Members of Steel structure are connected with each other by using Bolts, Rivets and Welding. Such connections can be used to properly transfer load to different members of the structure.

1) Bolted Connections

Bolts and Nuts are used for temporary connections between steel structure members. A bolt can be defined as a metal pin with a head at one end and a shank threaded at the other end to receive a nut. Steel washers are provided under the bolt and nut to distribute the pressure on the bolted member.

Bolted connections can be made quickly and not much skill is required for basic use. But when subjected to vibrations, they can get loose. They have reduced strength because of their loose fit.

These can be of many types. Commonly used are:
(a) Unfinished Bolts
(b) Turned Bolts
(c) Ribbed Bolts
(d) High Strength Bolts
(e) Interference Bolts

2) Riveted Connections

Rivets are made from the round steel rods and consist of a hemispherical bottom shaped head with a cylindrical shank. The holes are drilled in the members to be connected. The rivet is heated and is inserted in the hole. The second head is formed on the other end of shank by hand hammering, hydraulic pressure driving or pneumatic pressure driving.

Diameter of the holes drilled between members is slightly greater than the diameter of the shank. Rivets can be inserted in cold state too, but their use is limited. Two types of riveted joints are:

a) Lap Joint: The two members to be connected are overlapped and connected together.
b) Butt Joint: The two members to be connected are placed end to end, and additional cover plate is connected with main plates.

Spacing of Rivets and number of Rivets to be placed for a connection are calculated based on design requirements.

3) Welded Connections

Welding has become a popular method for connecting steel members in a structure. Two major welding methods are a) Electric Arc Welding and b) Oxy-Acetylene Gas Welding. Welding rods are used to provide the molten material necessary to fill the joint.

In Electric Arc Welding, a spark is produced between the welding rod and the surface to be welded. In Oxy-Acetylene Gas Welding, a combination of oxygen and acetylene gases is supplied under pressure.

Common types of welding joints are a) Lap Joint, b) Butt Joint and c) Fillet Joint

Welding process can be done rapidly and no holes need to be drilled. It is economical and members can be joint in various desired patterns.