Below is an introduction to the topic Connections. You can also search for your specific topic using the Search box at the top of the page or click on any of the following keywords and phrases: Simple connections; Moment connections; Greenbooks.
In a typical braced multi-storey frame the connections may account for less than 5% of the frame by weight, and yet probably 30% or more of the total cost. Efficient connections will therefore have the lowest detailing, fabrication and erection labour content - they will not necessarily be the lightest.
A problem facing the connection designer is the bewildering range of options he has in selecting:
Modern connection design is therefore based on a rationalisation of the above options and this procedure leads to a standard connection where the fittings, bolts, welds and geometry are fully defined. The benefits of this approach are:
Steel structures can be complex and there will be times when standard connections are not suitable. However even in these cases it will still be possible to adopt some of the general principles of standardisation such as limiting the range of fittings, sections and bolt sizes.
|Fittings||Material of grade S275||Limited range of standard flats and angles|
|Bolts||M20 grade 8.8 bolts||Some heavily loaded connections may need larger diameter bolts
Foundation bolts M24 grade 4.6
|Holes||22 mm diameter punched or drilled, or 22 mm x 26 mm slotted holes made by:
- Punching in one operation
- Formed by drilling two holes and completed by cutting
- Machine operated flame cutting
|26 mm dia for M24 bolts
6mm oversize for Foundation bolts
|Welds||Fillet welds with E35 electrodes 6 mm or 8 mm leg length||Larger welds may be needed for some column bases|
Design procedures for simple connections are given in the publication Joints in Steel Construction - Simple Connection (1). This publication provides procedures for desiging connections in steel-framed structures in accordance with the recommendations given in B=S 5950-1: 2000(2). It uses the simple design method described in clause 126.96.36.199 of BS 5950-1: 2000. Connections between universal beams and universal columns are included and between universal beams and hot finished structural hollow section columns using Flowdrill and Hollo-Bolt systems Design are provided for:
The procedures given in this publication are suitable for either hand calculation or for the preparation of computer software.
Designing connections by hand is a laborious process and so a full set of capacity tables is included in Joints in Steel Construction - Simple Connection (1). Checking the strength of a simple connection involves three stages:
Design procedures for moment connections are given in the publication Joints in Steel construction - Moment Connections (3). This publication provides methods for designing the following types of moment resisting connections in steel-framed structures:
The design procedures given in this publication are based on a combination of design models to established methods used both in the UK and overseas and capacity checks on bolts, welds and sections based on BS 5950-1: 2000. The methods are generally not suitable for hand calculation.