Structural Steel

Structural steel is steel that has been rolled or formed into standardized shapes for use as construction members, most recognizably the I-beam, whose deep, narrow cross section gives it a high second moment of area so it can carry a heavy load without excessive sagging. Beyond I-beams, which appear under different national naming systems such as Universal Beams and Universal Columns in Britain or Wide Flange sections in the United States, structural steel is also rolled into Z-shapes, hollow structural sections, angles, channels, tees, bars, rods and plates, each suited to a different structural role. The shapes, sizes, chemical composition and mechanical properties of structural steel are set by published standards in most industrialized countries, so a given shape designation carries the same guaranteed strength wherever it is specified. Structural steel members are typically assembled into an interconnected frame, riveted, bolted or welded at their joints, that together carries the loads a building or bridge must resist; the Home Insurance Building in Chicago, completed in 1885 to the design of William Le Baron Jenney, is often called the first skyscraper for using a fireproofed structural steel frame this way, though earlier iron framed buildings complicate the claim of a single first.