In this article, you will learn more about shear vs moment connection in steel detailing. The moment connection and shear connection types and their uses in steel detailing.
When it comes to steel detailing, steel connection is one of the most crucial design components, in terms of cost as well as the integrity of the structure. If connection types and arrangements are not carefully chosen, they can account for up to 65% of the total cost of production. This is because, for steel structures, the raw material cost is around 30-36%. The remaining is in shop fabrication.
Also read: How to understand welding symbols in steel detailing
For this reason, the selection of members and sizes should be such that the connection requirements can be simple. Hence increasing size can be allowed if it can simplify the steel connection. Detailing a connection is equally important as designing a connection.
The assumptions and philosophies used in the design should be reflected in the shop drawings. This will ease the fabrication process. Based on complexity and force transfer mechanism, the connections can be classified into the following categories.
- Simple shear connection
- Moment connection
Simple shear connection
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| Shear connection example |
Simple shear connections are one of the most common steel connections in practice. As the name says, these connections can transfer only shear forces to connected members. Moment transfer or moment continuity cannot be achieved using this steel connection. A shear connection keeps something from sliding back and forth.
The arrangement is less complicated and easy to fabricate in shops. Shear connections are achieved using shear plates, clip angles, end plates or seated connections.
Moment connection
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| Moment connection example |
In a steel structure, a moment connection refers to a joint that allows the transfer of bending moment forces between a column and a beam or between any other two adjoining members. A moment connection keeps something from turning in a circle.
Moment connections are decided only when considered necessary by the designer and most designers try to avoid it as it increases the costs of fabrication and erection.
Moment connections include shear connections. While a shear connection resists only shear, a moment connection takes care of both shear and end moments.
Moment connections become necessary under the following circumstances:
- At the fixed end support of a cantilever beam.
- A frame needs to be prevented from folding up under the action of lateral loads. Usually, bracings are provided at selected bays to achieve this stability and moment connections become unnecessary. But when these bracings cannot be provided for functional or architectural reasons, then the stability of the frame must be ensured by fixed beam-column end connections.
These moment connections prevent end rotations in the beams by firmly holding the flanges of the beams. Sometimes a moment connection is provided for particular beams to reduce the mid-span moment in a beam with a depth restriction due to headroom considerations. A simply supported beam may turn out to be too deep.
Almost all connections between beams and columns are simple shear connections in most steel-framed structures. If the frame is braced, a moment connection may not be necessary anywhere in the frame as lateral stability of the building is assured by the provision of bracings.