How to Design a Steel IBeam: Selection of Correct Size Steel for Load Specifications
A steel I beam typically has the following important features or dimensions. (Please refer to the picture below):
IBeam Terminology
 Flange thickness: Top and bottom horizontal platelike sections of an Ibeam are called flangen. The thickness of the flanges is called the flange thickness.
 Flange width: The width of the flanges is called flange width.
 Beam depth: The height between the top and bottom surface of the steel I beam is called beam depth.
 Web thickness: The vertical section of steel I beam is called web, and the thickness of the web is called web thickness.
 Fillet radius: The curved portion, where the transition between the web and flange happens is called a fillet. The radius of the fillet is called the fillet radius.
Steps for Selecting a Correctly Sized I Beam
The overall procedure of selecting the correct size of the I beam is based upon basic mechanical design calculations as follows:

The first input you need is the steel I beam load specifications or loading details on the steel I beam.

Draw bending moment diagram for the given loads and you will find the value of maximum bending moments (say M) that the steel I beam is expected to experience.

Choose an approximate size of steel I beam from a standard I beam table.

Find out the area moment of inertia (say I) of the selected steel I beam.

Get the beam depth (say d) of the selected steel I beam.

Now use the following formulae for calculating stress developed (f) in the beam:
f/(d/2)=M/ I
f is the bending stress
M  the moment at the neutral axis
y  the perpendicular distance to the neutral axis
I  the area moment of inertia about the neutral axis x
 Compare the calculated value of the bending stress with the yield stress of the steel in order to check the safety factor of your design.
Conclusion
Correctly sized I beam selection is the first step toward correct structural design. The procedure explained above is based upon static I beam load specifications. In the cases where dynamic loads are involved, you need to use FEA tools like ANSYS, Pro Mechanica, etc.
See also

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