Understanding Structural Steel Shapes & Beam Types

Forms of structural steel have long been standardized by AISI.  In discussing beams, tees, and channels, reference is made to flanges and webs. The flange is identified as the flat portion which, in the case of a beam, would normally be situated at the top and the bottom of the beam. The web connects the two flanges, and in normal construction is oriented vertically to give the beam its high resistance to bending. Angles are identified by their leg lengths, which may be equal or unequal.

ASTM A36 steel, with a yield strength of 36,000 psi, is the most common material for structural steel shapes although other materials are available for special circumstances including low-alloy, high-strength, and stainless steels. Steel members are connected to one another through the use of bolted or riveted plates that attach to the beam webs or they may be welded directly to each other. AISC specifies for both framed-beam and heavy framed-beam connections the appropriate number of rows of bolts or rivets based on several standard-diameter fasteners.

A distinction is recognized between “bar-size” and “structural-size” shapes. Bar size is used to describe any shape whose major sectional dimension is under 3 inches.

This article briefly discusses some of the popular steel shapes as well as the settings in which these shapes excel.

The principal types of structural steel shapes include:

• Beams
• Tees
• Channels
• Angles
• Hollow Structural Sections (HSSs)

Types of Steel Beams

Structural steel beams and girders are available in three shapes: standard or “S” beams, wide flange or “W” beams, and pile or “H” beams.

Standard beams are specified by a letter callout, S, then the nominal web height in inches, then the per-foot weight in pounds.  Most come in lightweight versions and some of the larger beams are available in several intermediate weights. Standard beams have tapered flanges whereas wide-flange beams have parallel flanges.

“H” beams will often have flanges and webs of equal thickness while the flanges of “S” and “W” beams are thicker than the webs. “H” beams are commonly driven into the soil to provide foundation piling. They can be built-up from separate pieces. “S” and “W” shapes are typically hot-rolled as single pieces. Beams are typically available in lengths up to 60 ft.

On a semantic note, while all girders are beams, not all beams are girders. In construction, the girder is identified as the primary load-carrying member, with the beams loading to it.

Tees  

Tees are steel beams cut longitudinally through their webs, resulting in a single full flange and a half-deep web. They are available in the same shapes as full-size beams: “S” and “W.” The designation identifies the type, “ST,” followed by the nominal web depth in inches, followed by the shape, “I” or “WF.”

Channels

Channels have single webs flanked by upper and lower flanges, with the webs oriented off to the side and the flanges projecting perpendicularly to the webs, much like half a beam except the web is full thickness.  The channel flanges have the same taper as standard beams – approximately a 16-2/3 % slope. Lengths of up to 20 and 40 ft. are common for bar sizes, with structural size usually available as 60 ft. lengths. Channels are not ordinarily applied as beams but the flat faces allow them to be bolted up to other flat faces.

Angles

Angles are “L” shaped in section with equal- or unequal-length, tapered legs. Their use as beams is strongly discouraged unless they are doubled up and connected in a manner approximating a tee. Angles have many applications, however, and are used as bracing, for trusses, etc.

Hollow Structural Sections (HSSs)

HSSs, or Hollow Structural Sections, are rectangular, square, elliptical, or circular in section, and the rectangular shapes are commonly used for welded frames where the loads act upon the structure in several directions. Circular HSSs, sometimes called round structural tubing, differs from pipe in the fluid-carrying sense (which is covered by different standards) but is used for load-bearing columns, etc. such as Lally columns. These shapes all start as welded rounds, with the square and rectangular tubing put through additional forming to create final products with heavy radii at their corners.

Summary

This article presented a brief summary of common structural steel shapes. For more information on additional products, consult our other guides or visit the Thomas Supplier Discovery Platform to locate potential sources of supply or view details on specific products.