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What are the types of beams?

Beams can be classified in many different ways, for example by looking at support types, material, type of section, and so on. In this article we will discuss how beams can be differentiated based on their boundary conditions, i.e. how they are supported.

What is a beam?

Before jumping into the various beam types, we should probably define what a beam is.

In general, a beam is a member of a structure that is used to support vertical loads, and that can be approximated as a one-dimensional entity. In order for this approximation to be valid, the cross-section dimensions of a beam must be at least one order of magnitude smaller than the beam’s length. In other words, beams can’t be too "stubby".

What are the types of beams?

There are five main types of beams:

• simply supported beam;
• cantilever beam;
• overhang beam;
• continuous beam;
• fixed beam.

The distinction is based on how the beam is supported. As you can imagine, this is not an exhaustive list, since most beam configurations don’t have an actual name. Having said that, the vast majority of beams that exist in the world fall into one of these categories.

One key aspect to keep in mind is the degree of determinacy of any given beam. Some beam types are statically determinate and some are not. If you want to learn more about this, check out our degrees of freedom article.

Simply supported beam

Simply supported beams have a pin at one end and a roller at the other. This configuration is statically determinate with 3 degrees of freedom and 3 restraints. Simply supported beams can be “chained” together to form multiple spans by adding more rollers and hinges.

The key aspect to remember about simply supported beams is that the bending moment at the supports is always zero.

Cantilever beam

Cantilever beams have a fixed support at one end, while the other end is free. This configuration is also statically determinate. The bending moment is maximum at the fixed end, and zero at the free end.

Overhang beam

An overhang beam is just like a simply supported beam, except one or both ends extend beyond the supports. Like the simply supported beams, overhang beams are statically determinate.

Continuous beam

A continuous beam is supported by a pin and two or more rollers. There are no hinges in this configuration (unlike in the multi-span simply supported beam) so it is statically indeterminate. The advantage is that the overall beam is more rigid, resulting in a smaller deflection when subjected to a load.

Fixed beam

Fixed beams are fixed at both ends, resulting in a very rigid configuration. They are mostly found in frames, and are statically indeterminate to the third degree.

Conclusion

The most common types of beams are five: simply supported,cantilever, overhang, continuous and fixed. This distinction is made by looking at the supports. In general, statically determinate beams have bigger deflections than statically indeterminate beams.

For more great information about beams and structures, check out or resources page.