W 40X331 vs UB 1016×305×487
W 40X331 is an W section from the American AISC Shapes Database; UB 1016×305×487 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 23433.5 cm³ against 23200 cm³ of plastic modulus, a difference of 1.0%. They weigh essentially the same, 492.6 kg/m and 486.7 kg/m. Both are about 1036 mm deep, so either fits the same construction zone.
| Property | W 40X331 W | UB 1016×305×487 UB | Difference |
|---|---|---|---|
| Mass | 492.6 kg/m | 486.7 kg/m | +1.2% |
| Depth | 1036.3 mm | 1036.3 mm | same |
| Width | 309.9 mm | 308.5 mm | +0.5% |
| Web thickness | 31 mm | 30 mm | +3.3% |
| Flange thickness | 54.1 mm | 54.1 mm | same |
| Area | 630.3 cm² | 620 cm² | +1.7% |
| Second moment, major (Iy) | 1,028,092 cm⁴ | 1,022,000 cm⁴ | +0.6% |
| Plastic modulus, major (Wpl,y) | 23,433.5 cm³ | 23,200 cm³ | +1.0% |
| Elastic modulus, major (Wel,y) | 19,828.3 cm³ | 19,700 cm³ | +0.7% |
| Second moment, minor (Iz) | 26,805 cm⁴ | 26,700 cm⁴ | +0.4% |
| Plastic modulus, minor (Wpl,z) | 2,818.6 cm³ | 2,800 cm³ | +0.7% |
| Radius of gyration, minor (iz) | 6.53 cm | 6.57 cm | -0.6% |
| Torsion constant (It) | 4,370 cm⁴ | 4,300 cm⁴ | +1.6% |
W 40X331 to AISC Shapes Database v16.0; UB 1016×305×487 to BS EN 10365:2017. Difference is expressed relative to UB 1016×305×487.
How to choose between them
On stiffness, W 40X331 has the larger second moment of area: 1,028,092 cm⁴ against 1,022,000 cm⁴, a difference of 0.6%. This matters more often than the strength comparison, because on normal floor spans deflection rather than bending capacity sets the beam size - so if the two are close on modulus but apart on inertia, the stiffer one is usually the better answer even when it is not the stronger one.
Measured as bending capacity per kilogram, the two are equally efficient (47.6 against 47.7 cm³ per kg/m), so on a pure steel-tonnage basis there is nothing to choose between them. The decision comes down to availability, connection detailing and what the rest of the frame uses.
These come from different catalogues, so treat the swap as a design change rather than a like-for-like substitution. W sections are specified to AISC Shapes Database v16.0 and UB to BS EN 10365:2017; the steel grades, tolerances and available lengths differ, connection details and bolt gauges are set out differently, and the two are rarely both stocked in the same market. Check availability before changing a section on a drawing to save a marginal amount of weight.
In short, these two are genuine equivalents. Pick whichever your supplier stocks and the rest of the frame already uses.