What a W-Series Wide Flange Beam Is
A W-series wide flange beam is a rolled structural shape with two parallel flanges and a web perpendicular to them, identified by nominal depth and weight, for example W8×10 or W8×31, with dimensions controlled by ASTM A6 and published in the AISC shapes tables. Unlike an I-beam, the wide flange has parallel flange faces and a relatively thicker web, which simplifies bolted and welded connections and improves performance in bending. The W8 family, with a nominal depth of 200 mm, is a popular choice for lighter roof frames, mezzanines, and plant structures where headroom and section size matter.
W8×10 and W8×31 Section Details
The W8×10 section has a nominal depth of 203.7 mm, a flange width of 100.1 mm, a web thickness of about 4.3 mm, and a unit weight of 14.9 kg per meter, which makes it one of the lightest wide flange beams available. The W8×31 is a much heavier member with a depth of 203.2 mm, a flange width of 203.2 mm, a web thickness of about 7.2 mm, and a unit weight of 46.1 kg per meter. The wider flange of the W8×31 gives substantially higher minor-axis strength and a larger bearing surface for connections, which is valuable for crane-runway brackets, equipment platforms, and column applications.
Material Grades and Mechanical Properties
ASTM A36 is the default grade for welded frames and general fabrication, with a minimum yield strength of 250 MPa and a tensile range of 400 to 550 MPa. ASTM A572 Grade 50 provides a minimum yield of 345 MPa and a minimum tensile strength of 450 MPa, allowing longer spans or lighter members at a modest cost premium. For seismic moment frames, ASTM A992 is the preferred W-shape grade, with a controlled yield range of 345 to 450 MPa and specified Charpy V-notch toughness. All three grades are weldable with common carbon steel consumables.
Roof Support and Plant Structure Applications
In a typical manufacturing plant, W8 beams serve as roof purlin supports spanning between main roof trusses or girders, carrying the roof sheet, insulation, and services. They are also used as mezzanine floor beams, equipment support stools, ladder and platform framing, and pick-up beams for overhead doors. Because the W8 series fits within a compact envelope, it allows maximum clear height in low-clearance buildings and simplifies the support of ductwork, cable trays, and pipe racks that run beneath the roof.
Cutting, Drilling, and Surface Treatment
Wide flange beams can be cut by band saw or oxy-fuel, coped at ends for beam-to-beam connections, and drilled for high-strength bolting. Hot-dip galvanizing or a two-coat paint system is applied where the steel is exposed to humidity or industrial atmospheres. For plant structures, intumescent fire protection may be required on roof members if the building code imposes a fire rating, so fabrication planning should allow for surface preparation that is compatible with the chosen coating system.
Frequently Asked Questions
Q: What does W8×10 mean?
W indicates a wide flange shape, 8 is the nominal depth in inches, and 10 is the nominal weight of 10 pounds per foot, which equals about 14.9 kg per meter.
Q: Should I use A36 or A572 Grade 50?
Use A36 for simple welded frames and secondary members; use A572 Grade 50 when longer spans, heavier loads, or smaller sections are required to reduce total steel weight.
Q: Can W8 beams be used as columns?
Yes, W8 sections are commonly used as columns in light industrial buildings and mezzanines, with base plates and cap plates welded to the ends.
Q: Are W8 beams available galvanized?
Yes, beams can be hot-dip galvanized after fabrication, and vent and drain holes should be arranged so that the interior of the section is fully coated.
Q: What standard controls W-shape dimensions?
Rolling tolerances and section properties are governed by ASTM A6, with tabulated dimensions and properties published in the AISC steel construction manual.