W 36X247 vs UB 914×419×388
W 36X247 is an W section from the American AISC Shapes Database; UB 914×419×388 is the closest equivalent in the UK Blue Book (SCI P363). UB 914×419×388 carries more bending: 17700 cm³ of plastic modulus against 16878.7 cm³, 4.6% more. W 36X247 is the lighter of the two at 367.6 kg/m against 388 kg/m, a saving of 5.3% on steel weight. Both are about 927 mm deep, so either fits the same construction zone.
| Property | W 36X247 W | UB 914×419×388 UB | Difference |
|---|---|---|---|
| Mass | 367.6 kg/m | 388 kg/m | -5.3% |
| Depth | 932.2 mm | 921 mm | +1.2% |
| Width | 419.1 mm | 420.5 mm | -0.3% |
| Web thickness | 20.3 mm | 21.4 mm | -5.1% |
| Flange thickness | 34.3 mm | 36.6 mm | -6.3% |
| Area | 467.7 cm² | 494 cm² | -5.3% |
| Second moment, major (Iy) | 695,106 cm⁴ | 720,000 cm⁴ | -3.5% |
| Plastic modulus, major (Wpl,y) | 16,878.7 cm³ | 17,700 cm³ | -4.6% |
| Elastic modulus, major (Wel,y) | 14,961.4 cm³ | 15,600 cm³ | -4.1% |
| Second moment, minor (Iz) | 42,039 cm⁴ | 45,400 cm⁴ | -7.4% |
| Plastic modulus, minor (Wpl,z) | 3,113.5 cm³ | 3,340 cm³ | -6.8% |
| Radius of gyration, minor (iz) | 9.5 cm | 9.59 cm | -0.9% |
| Torsion constant (It) | 1,444 cm⁴ | 1,730 cm⁴ | -16.5% |
W 36X247 to AISC Shapes Database v16.0; UB 914×419×388 to BS EN 10365:2017. Difference is expressed relative to UB 914×419×388.
How to choose between them
On stiffness, UB 914×419×388 has the larger second moment of area: 720,000 cm⁴ against 695,106 cm⁴, a difference of 3.5%. 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 (45.9 against 45.6 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, UB 914×419×388 is the stronger section and W 36X247 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.