W12x40

W12x40 is a designation for a standardized wide flange steel beam that is part of the EIA Steel Designation system used in North America. The "W" indicates a wide flange section, also known as a "Welded Beam". The first number, 12, represents the nominal depth of the beam in inches, while the second number, 40, specifies the weight of the beam in pounds per foot. Thus a W12x40 beam has a depth of 12 inches and weighs approximately 40 pounds per foot of length.

The beam’s cross‑section is defined by a pair of parallel flanges that run the length of the beam and a central web that supports bending and shear. Standard dimensions include a flange width of about 6.76 inches and a toe width of around 0.23 inches. The web thickness averages 0.55 inches at the mid‑depth. These dimensions vary slightly depending on the exact product grade and manufacturer but are bounded by ANSI/ASME 5.5.9 and ASTM A992 specifications.

W12x40 beams are typically fabricated from ASTM A992‑16 or A992‑20 structural steel, which offers high strength (yield strength 50 ksi, ultimate strength 65 ksi) and good weldability. They are widely used in commercial and industrial construction for framing floors, roofs, and columns, especially where moderate loads and longer spans are required. Their weight allows for easier handling and faster erection compared with heavier sections, yet they still provide adequate stiffness for many architectural and engineering applications.

The section’s load‑carrying capacity is derived from its section modulus of 4.30 inch³ and moment of inertia of 8.70 in⁴. These properties make the W12x40 suitable for typical residential and light‑commercial loading conditions. Design engineers refer to the American Institute of Steel Construction Nomogram and AISC Steel Construction Manual for span tables and design calculations.