Isection

I-section, commonly referred to as an I-beam or H-beam, is a structural steel member with an I-shaped cross-section. The cross-section consists of two parallel horizontal flanges connected by a vertical web. The geometry places much of the material near the flanges, increasing bending stiffness while keeping weight relatively low.

Manufacture and materials: I-sections are usually produced by hot rolling from steel and are also available in aluminum or other metals. In the United States, wide-flange shapes (W-sections) are a common form of I-section; other regions use different designations such as I or HE shapes. Sizes are standardized with data on overall depth, flange width, web thickness, and weight per unit length.

Mechanical properties: The bending stiffness is quantified by the second moment of area, I, about the major axis (I_x) and minor axis (I_y). For a given depth, increasing flange width or thickness raises I more effectively than increasing web thickness. The section modulus and load-carrying capacity depend on geometry and material properties. I-sections are most efficient for bending about the strong axis and are commonly used in frames and beams.

Applications: I-sections are widely used in structural framing, bridges, cranes, and other load-bearing applications due to their high stiffness-to-weight ratio and straightforward fabrication. They are typically joined by welding or bolting and used in combinations to form frames, supports, and longitudinal members.

Notes: The term I-section can refer to various manufactured shapes made from steel, aluminum, or composites. In some regions, the term H-section is used for wide-flange shapes. The overall choice depends on required structural performance, availability, and local standards.