W8x31 Beam Specifications

W8x31 is a rolled structural beam with wide flanges that is used in construction and other applications.

W8x31 Beam Size and Dimensions

The dimensions and specifications of this structural steel beam are below:

Depth	8 in
Width	8 in
Area	9.1 in2
Weight	31 lb/ft
Web Thickness	0.29 in
Flange Thickness	0.44 in
Area Moment of Inertia	108 in4
Elastic Section Modulus	27 in3

W8x31 Profile

The depth of W8x31 beams may vary by 1/8” above and below the nominal value.

The flange width may vary by 1/4” above nominal and 3/16” below nominal. Flanges may be out of square by as much as 5/16”.

The distance from the center of the web to the center of the profile may be no greater than 3/16”.

The radii of fillets and toes for W-beams are not specified. Instead, these dimensions are left up to individual manufacturers.

W8x31 Weight

Wide flange beams are designated by their depth x weight. The W8x31 designation indicates that the beam weighs 31 pounds per foot. A 10-foot section of W8x31 would weigh 310 pounds and a 50-foot section of W8x31 would weigh 1,550 pounds.

W8x31 Conversion to Metric

The metric equivalent to W8x31 is W200x46.1. This metric beam has the following specifications:

Depth	203 mm
Width	203 mm
Area	5890 mm2
Weight	46.1 kg/m
Web Thickness	7.2 mm
Flange Thickness	11 mm

W8x31 Section Properties

W8x31 Area Moment of Inertia

The area moment of inertia (or second moment area) for a W8x31 beam about the x-axis (perpendicular to the flange) can be calculated from the equation below:

The area moment of inertia of the W8x31 profile about the x-axis is approximately 108 in⁴.

W8x31 Section Modulus

The elastic section modulus for a W8x31 beam about the X-axis is calculated from the following equation:

The elastic section modulus for the W8x31 profile about the X-axis is approximately 27 in³.

W8x31 Properties

The properties of W8x31 beams are specified by ASTM A6 “Standard Specifications for Rolled Structural Steel Bars, Plates, Shapes and Sheet Piling”