What Is a Wide Flange Beam?

B. Turner

A wide flange beam is a type of building material used to construct homes, bridges, and other structures. Like the standard I-beam, it features a profile that resembles the letter "I" or "H." A central web connects the two parallel end units, known as flanges. While the flanges in a standard beam are relatively narrow, those in a wide beam are much broader, and may be equal in length to the height of the web. In the United States (US), wide flange beams represent the most widely-used type of beam, while standard I-beams are less common.

A wide flange beam.
A wide flange beam.

To understand how this type of beam works, a person can picture a single sheet of steel lying flat on the ground. This sheet represents the bottom flange of the beam. A second sheet of steel with the same dimensions as the first can be placed in the center of this sheet, positioned at a 90-degree angle, then welded or forged in placed to form the web. A third sheet is then placed parallel to the first to form the second flange. In a standard I-beam, the flanges are generally narrower than the height of the web, while in a wide flange beam, they are often just as long as the web is tall.

Wide flange beams often serve as structural supports for highway ramps and overpasses.
Wide flange beams often serve as structural supports for highway ramps and overpasses.

This beam can be used in many types of building applications. In the US, it is the standard for creating columns in home and commercial buildings. These beams can also be placed parallel to the ground to form floors and roofs. They also play a pivotal role in bridge construction, and serve as structural supports for highway ramps and overpasses. These beams are traditionally made of steel or aluminum, though wood and composite models have also become more common, particularly for residential construction.

The primary advantage to the wide flange beam is that it allows builders to distribute a load over a wide area. This means that it can support a larger or wider structure with less risk of failure. They also weigh less than a square beam of the same size, but can support a larger load, making them more efficient.

Throughout the world, beam sizes are standardized, making it easier for engineers, architects, and builders to coordinate during construction. In the US, sizes are based on standards developed by American Society for Testing and Materials (ASTM) International or the American National Standards Institute (ANSI). Other countries may also use these standards, though some rely on their own set of beam sizing requirements.

The size of a wide flange beam in the US is always preceded by a "W." The numbers following this letter provide the depth of the web and the weight of the beam. For example, a beam marked W10x22 will have a 10 inch (25 cm) web depth and a weight of 22 pounds per foot (33 kg per m).

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