Ibeam

I-beam, also known as an I-section or H-section in some regions, is a structural steel member with a cross-section that resembles the letter I. It consists of two horizontal flanges connected by a vertical web. The flanges resist bending, while the web carries shear and helps locate the centroid. This arrangement provides a high second moment of area, yielding substantial bending stiffness with relatively low weight for many load cases.

Manufacture and sizes: I-beams are typically hot-rolled from steel, but versions exist in aluminum or composite materials. Sizes are defined by overall depth, flange width, and web thickness, with depth usually measured from outer face to outer face of the flanges. In American practice, standard I-beams are often referred to as S-beams (standard) or W-beams (wide-flange); similar profiles exist worldwide under different designations. Beams are supplied in lengths that may require splicing on site and are joined by bolting or welding.

Applications: I-beams are widely used as primary load-bearing members in steel-frame buildings, bridges, cranes, platforms, and other structures where vertical loads produce bending moments. They are typically connected to columns and other members with bolted or welded connections and can be used in concert with other shapes to suit specific performance requirements.

Advantages and limitations: I-beams offer high bending stiffness and a favorable strength-to-weight ratio, ease of fabrication, and broad availability in multiple sizes. They are especially efficient for long spans and frames with predominant bending loads. Limitations include relatively weaker torsional resistance compared with closed sections, potential web buckling under certain load combinations, and the need for proper bracing and connections to maintain overall stability.