Selecting the correctly sizez steel I beam is very important for your structural design. Gain more understanding of the selection procedure for a steel I beam for given load specifications.

A steel I beam typically has the following important features or dimensions. (Please refer to the picture below):

### I-Beam Terminology

○ **Flange thickness:** Top and bottom horizontal plate-like sections of an I-beam 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.

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