Anatomy of a Steel I-Beam

Characteristics and Terminology of Structural I-Beams

Apr 14, 2009 Susan Kristoff

Steel I-beams are used for a variety of structural applications. Specific terminology is used to describe I-beam characteristics and properties.

Steel I-beams can be found in nearly all construction projects, from skyscrapers and highways to residential construction and industrial cranes. The properties of the I-beam make it an optimal choice to balance beam strength and weight. Most of an I-beam’s cross-sectional area is located away from the neutral axis of the beam, resulting in a high moment of inertia, or “I” value.

Steel I-Beam Terminology

I-beams are characterized by the size of their features, including:

  • Beam Depth – The outside vertical height of the I-beam from one flange surface to the other flange surface
  • Web Thickness – The thickness of the vertical portion of the I-beam
  • Flange Width – The outside horizontal width of the flange
  • Flange Thickness – The thickness of the horizontal portion of the I-beam
  • Fillet – the concave transition between the web and the flange of the I-beam

These parameters are illustrated in the figure below for reference.

Types of I-Beams

There are three primary types of I-beam profiles used in the United States:

  • American Standard Beams have tall webs with narrow flanges. The beam size is written beginning with the letter “S” followed by the depth of the beam in inches and the weight in pounds per linear beam foot. The flanges are sloped on the inner flange surface, with the thickest point at the web and tapering out to the ends.
  • Wide Flange Beams have much wider flanges than American Standard Beams. The beam size is written beginning with the letter “W” followed by the depth of the beam in inches and the weight in pounds per linear beam foot. The inner and outer surfaces of the flanges are parallel.
  • H-Piles are used for compression support in foundations. H-piles are driven down into soils and other foundations that cannot support structures on their own. Unlike the other beam types, which are generally loaded transversely, H-piles are meant to be loaded on their ends. H-piles are generally square, in that their flange width is the same as the beam depth.

Selection of beam type depends on its usage and the types and magnitudes of forces that the beam will experience during its use. Steel I-beam manufacturers outside of the United States use the same naming convention, but replace the measurements with metric units, usually millimeters for beam depth and kilograms/meter for linear weight.

To learn more about the uses and benefits of steel I-beams, please read The Properties of Steel I-Beams.

Sources

Wide Flange Beam Tables at The Engineering Toolbox

The copyright of the article Anatomy of a Steel I-Beam in Engineering is owned by Susan Kristoff. Permission to republish Anatomy of a Steel I-Beam in print or online must be granted by the author in writing.
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Comments

Oct 8, 2009 8:46 AM
Guest :
Thanks so much for this. It's helped a bit with understand the terminology. :)
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