W 40X297 vs UB 1016×305×437
W 40X297 is an W section from the American AISC Shapes Database; UB 1016×305×437 is the closest equivalent in the UK Blue Book (SCI P363). W 40X297 carries more bending: 21794.8 cm³ of plastic modulus against 20800 cm³, 4.8% more. They weigh essentially the same, 442 kg/m and 437 kg/m. Both are about 1019 mm deep, so either fits the same construction zone.
| Property | W 40X297 W | UB 1016×305×437 UB | Difference |
|---|---|---|---|
| Mass | 442 kg/m | 437 kg/m | +1.1% |
| Depth | 1010.9 mm | 1026.1 mm | -1.5% |
| Width | 401.3 mm | 305.4 mm | +31.4% |
| Web thickness | 23.6 mm | 26.9 mm | -12.3% |
| Flange thickness | 41.9 mm | 49 mm | -14.5% |
| Area | 563.2 cm² | 557 cm² | +1.1% |
| Second moment, major (Iy) | 965,657 cm⁴ | 910,000 cm⁴ | +6.1% |
| Plastic modulus, major (Wpl,y) | 21,794.8 cm³ | 20,800 cm³ | +4.8% |
| Elastic modulus, major (Wel,y) | 19,172.9 cm³ | 17,700 cm³ | +8.3% |
| Second moment, minor (Iz) | 45,369 cm⁴ | 23,400 cm⁴ | +93.9% |
| Plastic modulus, minor (Wpl,z) | 3,523.2 cm³ | 2,470 cm³ | +42.6% |
| Radius of gyration, minor (iz) | 8.99 cm | 6.49 cm | +38.5% |
| Torsion constant (It) | 2,547 cm⁴ | 3,190 cm⁴ | -20.2% |
W 40X297 to AISC Shapes Database v16.0; UB 1016×305×437 to BS EN 10365:2017. Difference is expressed relative to UB 1016×305×437.
How to choose between them
On stiffness, W 40X297 has the larger second moment of area: 965,657 cm⁴ against 910,000 cm⁴, a difference of 6.1%. 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 of steel, W 40X297 is the more efficient section: 49.3 against 47.6 cm³ per kg/m, 3.6% better. Over a floor of repeated beams that difference is real tonnage, though it is often outweighed by whichever section the fabricator can actually source.
The two diverge much more about the minor axis: W 40X297 has 3523.2 cm³ of minor-axis plastic modulus against 2470 cm³, 42.6% more. If the member sees any minor-axis bending, or if it is unrestrained over a long length and lateral-torsional buckling governs, that gap decides the comparison even though the major-axis numbers looked equivalent.
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, W 40X297 is the stronger section and UB 1016×305×437 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.