An I-beam, also known as an H-beam, W-beam, rolled steel joist or double-T, is a structural support material commonly used in civil engineering and construction.
I-beams get their name from their distinctive shape. They’re comprised of a long, vertical piece of metal called a ‘web’ and shorter horizontal pieces called ‘flanges’. These pieces fit together to create a beam whose cross section looks like the letter ‘I’.
Types of I-beams
Steel I-beams are the most prevalent type, but it’s also common to find I-beams made of a variety of other materials, including aluminum and wood.
In addition to being classified by material type, I-beams are also classified by their dimensions. The nomenclature varies from country to country, but in the US I-beams are referred to by using the distance of the beam from the outer face of one flange to another and by the beam’s weight per foot. Hence an ‘11×20’ would have a depth of 11 inches and a weight 20 lbs per foot.
I-beams are often used as major support trusses in buildings, helping to ensure their structural integrity. An I-beam’s strength can reduce the need for numerous support structures, letting builders create aesthetically-pleasing, wide-open spaces within buildings.
Advantages and Disadvantages
An I-beam’s web resists shear forces, while its flanges resist bending moments. This allows the beam to excel at carrying shear and bending forces in the plane of the web. However, I-beam strength is less formidable in the transverse direction, and the I-beam is also less adept at carrying torsion.
Steel I-beams vs. Wooden I-beams
Wooden I-beams are often admired for their aesthetic beauty. They also allow you to hang furnishings from them, which is difficult with steel I-beams.
However, steel I-beams have various advantages of their own. They are much less likely to bend and warp. They’re also insusceptible to rot (though they will rust). Overall, they’re stronger than wooden beams, meaning you can use fewer of them to support the same load.
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