How to calculate the shear resistance of a steel section
This is a short tutorial on how to calculate the shear resistance of an I, H, parallel flange channel and square hollow section
Shear resistance is often overlooked in structural steel design, and this is partly because it is rarely the critical case. But rarely does not mean never - in certain cases shear resistance will be the critical design case.
So when is it critical?
Most beams experience a uniformly distributed load that evenly spreads the load across the beam's length. In these cases, what we are most interested in is the bending and deflection results. However, when we have high concentrated point loads or a primary beam that supports the secondaries close to the supports, it's a different story.
In this article we'll look at how to check the design shear resistance for a steel section, but don't forget that if you are doing this check in practise, you may need to consider the combined shear and moment check as well.
Breaking this down we have:
This is the area of steel subject to shear stresses, ie parallel to applied load. This is best explained visually so I've created a PDF of how to calculate the shear resistance, add your mail at the bottom of this page and I'll send it to you.
Unlike when doing bending checks which uses tensile yield stress (usually either 275N/mm2 or 375N/mm2), we need to transform this to the shear yield stress before it can be used.
Hence the square root of three.
The shear area is then multiplied by the shear yield stress and divided by the partial material factor of 1. Please note - this article relates to design codes in the UK, but elsewhere you may have a different factor so always check your local design code first.
For an example of how this is used in practise, check out my course on the Principles of Structural Steel Design where we go through it in a bit more detail.
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