UB 1016×305×349 vs W 40X235
UB 1016×305×349 is an UB section from the UK Blue Book (SCI P363); W 40X235 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 16600 cm³ against 16550.9 cm³ of plastic modulus, a difference of 0.3%. They weigh essentially the same, 349.4 kg/m and 349.7 kg/m. Both are about 1008 mm deep, so either fits the same construction zone.
| Property | UB 1016×305×349 UB | W 40X235 W | Difference |
|---|---|---|---|
| Mass | 349.4 kg/m | 349.7 kg/m | -0.1% |
| Depth | 1008.1 mm | 1008.4 mm | same |
| Width | 302 mm | 302.3 mm | -0.1% |
| Web thickness | 21.1 mm | 21.1 mm | same |
| Flange thickness | 40 mm | 40.1 mm | -0.2% |
| Area | 445 cm² | 445.8 cm² | -0.2% |
| Second moment, major (Iy) | 723,000 cm⁴ | 724,243 cm⁴ | -0.2% |
| Plastic modulus, major (Wpl,y) | 16,600 cm³ | 16,550.9 cm³ | +0.3% |
| Elastic modulus, major (Wel,y) | 14,300 cm³ | 14,338.7 cm³ | -0.3% |
| Second moment, minor (Iz) | 18,500 cm⁴ | 18,481 cm⁴ | +0.1% |
| Plastic modulus, minor (Wpl,z) | 1,940 cm³ | 1,933.7 cm³ | +0.3% |
| Radius of gyration, minor (iz) | 6.44 cm | 6.45 cm | -0.2% |
| Torsion constant (It) | 1,720 cm⁴ | 1,719 cm⁴ | +0.1% |
UB 1016×305×349 to BS EN 10365:2017; W 40X235 to AISC Shapes Database v16.0. Difference is expressed relative to W 40X235.
How to choose between them
On stiffness, W 40X235 has the larger second moment of area: 724,243 cm⁴ against 723,000 cm⁴, a difference of 0.2%. 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 (47.5 against 47.3 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. UB sections are specified to BS EN 10365:2017 and W to AISC Shapes Database v16.0; 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.