I-beams have a cross-sectional area that is shaped like the capital letter I. Wide Flange (W) steel beams are I-beams that have flanges where the planes are almost parallel. In the United States these beams are specified by depth and weight of the beam. If a beam is specified as W15x25, it is approximately 15 inches in depth and weighs approximately 25 pounds. The height refers to the height when the I-beam is standing on its flanges. For a simply supported beam, this is the most efficient cross section. Efficiency here refers to the fact that when comparing cross-sectional areas, the beam deflects less for the same cross-sectional area subjected to the same loading conditions.
American Standard (S) I-beams have a cross section that resembles a capital letter I. They have a slope on the inner flange surface. They are designated by depth and weight. An S24x121 specifies an S I-beam that is a depth of 24 inches from end to end of the standing beam and a weight of 121 pounds. This cross section is efficient because of the fact that most of the material is away from the neutral axis and the parallel axis theorem. The stiffness increases as the second moment of inertia increases. This cross section is only superior for unidirectional bending.
HP Bearing Pile (H) I-beams have an H cross section. These I-beams have parallel flange surfaces and equal web and flange thickness. HP14x117 is an H I-beam with a depth of 14 inches and a weight of 117 pounds. This weight is a nominal weight per foot designation. These beams are used in construction in formworks for building construction, curved wall formwork, custom-made formwork and table formwork. Table formwork is a kind of formwork specializing in floor concreting used in high buildings and skyscrapers. It is also used in slab and column formwork systems. These beams are made from a variety of materials.
Rolled Steel Joist (RSJ) beams are a type of I-beam. They are used in construction and industry. They come in a set of normal dimensions and can be sized by using tables. Made mainly of structural steel, they can be made of other materials as well. They have historically been used in large structures. The Eiffel Tower boasts RSJ beams as well as the Ferris wheel in the 19th century. With such success these beams were the impetus for the start of the second industrial revolution.