I-beams have a central section and four horizontal flanges so that a cross-section of the beam resembles the letter I. Beams are rated by an "A" number according to their load-bearing capacity, up to 65,000 lbs. per square inch for A992. They are also designated as to their depth and weight per square foot. Structural I-Beams are also known as S beams. They are used as basic structural components in building projects of all kinds, from large garden sheds to 100-story skyscrapers.
A wide-flange I-Beam has longer flanges than S beams, so that the beam in cross-section resembles the letter H. The American Standard I-Beam has flanges that are not parallel. H-beams are commonly used as foundation beams or vertical piles.
Bar-size T beams or "tees" have a short horizontal flange and long vertical component known as a stem. The beam is shaped like the letter T. The beam is specified by flange width, stem depth, stem thickness and weight. Like many varieties of steel beams and rods, they are sold in 20-foot lengths.
Channels are flat, shallow beams in the shape of a U, with a set of parallel short flanges on one side of the beam. They can be used as flat load-bearers attached to a horizontal surface, such as a flat roof or a poured concrete foundation. They also come in 20-foot lengths.
Flats and Rails
Flats are steel beams without flanges, up to 3 inches in thickness and up to 8 inches wide. They are sold by height, width and weight per foot. A rail is a steel beam with a thick, wide base, a short vertical stem and a thick, rounded horizontal section, as in the lengths of railroad track.
Steel beams can be connected to each other in the traditional way, with plates and rivets welded into the faces of the linked beams. They can also be linked by heavy clamps, which are attached with plates and a set of heavy bolts. No welding is necessary when using clamps, which can be adjusted to the depth and thickness of the beam.