W 40X277 vs UB 1016×305×437
W 40X277 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). They are close to interchangeable in bending: 20483.8 cm³ against 20800 cm³ of plastic modulus, a difference of 1.5%. W 40X277 is the lighter of the two at 412.2 kg/m against 437 kg/m, a saving of 5.7% on steel weight. Both are about 1017 mm deep, so either fits the same construction zone.
| Property | W 40X277 W | UB 1016×305×437 UB | Difference |
|---|---|---|---|
| Mass | 412.2 kg/m | 437 kg/m | -5.7% |
| Depth | 1008.4 mm | 1026.1 mm | -1.7% |
| Width | 401.3 mm | 305.4 mm | +31.4% |
| Web thickness | 21.1 mm | 26.9 mm | -21.6% |
| Flange thickness | 40.1 mm | 49 mm | -18.2% |
| Area | 525.8 cm² | 557 cm² | -5.6% |
| Second moment, major (Iy) | 911,547 cm⁴ | 910,000 cm⁴ | +0.2% |
| Plastic modulus, major (Wpl,y) | 20,483.8 cm³ | 20,800 cm³ | -1.5% |
| Elastic modulus, major (Wel,y) | 18,025.8 cm³ | 17,700 cm³ | +1.8% |
| Second moment, minor (Iz) | 43,288 cm⁴ | 23,400 cm⁴ | +85.0% |
| Plastic modulus, minor (Wpl,z) | 3,343 cm³ | 2,470 cm³ | +35.3% |
| Radius of gyration, minor (iz) | 9.09 cm | 6.49 cm | +40.1% |
| Torsion constant (It) | 2,144 cm⁴ | 3,190 cm⁴ | -32.8% |
W 40X277 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 40X277 has the larger second moment of area: 911,547 cm⁴ against 910,000 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 of steel, W 40X277 is the more efficient section: 49.7 against 47.6 cm³ per kg/m, 4.4% 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 40X277 has 3343 cm³ of minor-axis plastic modulus against 2470 cm³, 35.3% 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 5.7% weight.
In short, UB 1016×305×437 is the stronger section and W 40X277 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.