W8×28 vs W8×31
A side-by-side comparison of two AISC wide-flange beams, 16th Edition. Detailing dimensions to the nearest 1/16 in.
W8×31 is the heavier section at 31 lb per foot, versus 28 for W8×28 (3 lb/ft more).
Both are nominally 8 in. deep.
W8×31 has the greater bending strength: section modulus Sx of 27.5 in³ versus 24.3, about 13% more.
| Property | W8×28 | W8×31 |
|---|---|---|
| Weight | 28 lb/ft | 31 lb/ft |
| Depth (d) | 8" | 8" |
| Flange width (bf) | 6 1/2" | 8" |
| Web thickness (tw) | 5/16" | 5/16" |
| Flange thickness (tf) | 7/16" | 7/16" |
| Area (A) | 8.25 in² | 9.13 in² |
| Moment of inertia (Ix) | 98 in⁴ | 110 in⁴ |
| Section modulus (Sx) | 24.3 in³ | 27.5 in³ |
| Plastic modulus (Zx) | 27.2 in³ | 30.4 in³ |
Open W8×28 in the interactive size chart →
Full detail: W8×28 · W8×31. Verify critical dimensions against the current AISC Steel Construction Manual before fabrication.
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