W 40X278 vs UB 1016×305×393
W 40X278 is an W section from the American AISC Shapes Database; UB 1016×305×393 is the closest equivalent in the UK Blue Book (SCI P363). W 40X278 carries more bending: 19500.6 cm³ of plastic modulus against 18500 cm³, 5.4% more. UB 1016×305×393 is the lighter of the two at 392.7 kg/m against 413.7 kg/m, a saving of 5.3% on steel weight. Both are about 1019 mm deep, so either fits the same construction zone.
| Property | W 40X278 W | UB 1016×305×393 UB | Difference |
|---|---|---|---|
| Mass | 413.7 kg/m | 392.7 kg/m | +5.3% |
| Depth | 1021.1 mm | 1015.9 mm | +0.5% |
| Width | 304.8 mm | 303 mm | +0.6% |
| Web thickness | 26.2 mm | 24.4 mm | +7.4% |
| Flange thickness | 46 mm | 43.9 mm | +4.8% |
| Area | 531 cm² | 500 cm² | +6.2% |
| Second moment, major (Iy) | 853,274 cm⁴ | 808,000 cm⁴ | +5.6% |
| Plastic modulus, major (Wpl,y) | 19,500.6 cm³ | 18,500 cm³ | +5.4% |
| Elastic modulus, major (Wel,y) | 16,714.8 cm³ | 15,900 cm³ | +5.1% |
| Second moment, minor (Iz) | 21,686 cm⁴ | 20,500 cm⁴ | +5.8% |
| Plastic modulus, minor (Wpl,z) | 2,294.2 cm³ | 2,170 cm³ | +5.7% |
| Radius of gyration, minor (iz) | 6.4 cm | 6.4 cm | same |
| Torsion constant (It) | 2,706 cm⁴ | 2,330 cm⁴ | +16.1% |
W 40X278 to AISC Shapes Database v16.0; UB 1016×305×393 to BS EN 10365:2017. Difference is expressed relative to UB 1016×305×393.
How to choose between them
On stiffness, W 40X278 has the larger second moment of area: 853,274 cm⁴ against 808,000 cm⁴, a difference of 5.6%. 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 (47.1 against 47.1 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 5.3% weight.
In short, W 40X278 is the stronger section and UB 1016×305×393 is the lighter one; where those are the same section, it is the clear choice, and where they are not, decide on whether your design is governed by capacity or by tonnage.