W8×31 wide-flange beam

Detailing dimensions and section properties from the AISC Shapes Database, 16th Edition. Values are shown to the nearest 1/16 in. as they appear on a shop drawing.

W8×31 measures 8 in. deep with a 8 in. flange, on a 5/16 in. web and 7/16 in. flanges.

At 31 lb per foot it is one of the 13 W8 sizes, which run from 10 to 67 lb/ft.

For strong-axis bending its section modulus is Sx = 27.5 in³ and its moment of inertia Ix = 110 in⁴, with a plastic modulus Zx = 30.4 in³.

Detailing dimensions

Depth (d)8"
Flange width (bf)8"
Web thickness (tw)5/16"
Flange thickness (tf)7/16"
k (detailing)1 1/8"
Workable gage (g)5 1/2"

Section properties

Weight31 lb/ft
Area (A)9.13 in²
Ix110 in⁴
Sx27.5 in³
Zx30.4 in³
rx3.47 in
Iy37.1 in⁴
Sy9.27 in³
Zy14.1 in³
ry2.02 in
J0.536 in⁴

Other W8 sizes

Same nominal size, different weight — useful when you are checking a substitution or a lighter section.

W8×10W8×13W8×15W8×18W8×21W8×24W8×28W8×35W8×40W8×48W8×58W8×67

All W8 sizes and dimensions →

Similar weight wide-flange beams

Comparable 31 lb/ft sections in other wide-flange beam sizes.

W16×3131 lb/ft · Sx 47.2 in³W14×3030 lb/ft · Sx 42 in³W12×3030 lb/ft · Sx 38.6 in³W10×3030 lb/ft · Sx 32.4 in³W10×3333 lb/ft · Sx 35 in³W14×3434 lb/ft · Sx 48.6 in³W18×3535 lb/ft · Sx 57.6 in³W12×3535 lb/ft · Sx 45.6 in³

Compare W8×31 with a nearby size

W8×28 vs W8×31W8×31 vs W8×35W8×31 vs W16×31

Detailing values are rounded to the nearest 1/16 in. per the AISC Steel Construction Manual. Verify critical dimensions against the current Manual before fabrication. Need W8×31 cut, formed, or fabricated? Huntington Steel & Supply Co.

Browse more: Wide flange beams · Steel Beam Size Chart

Interactive drawing