UB 457×152×67 vs W 18X46
UB 457×152×67 is an UB section from the UK Blue Book (SCI P363); W 18X46 is the closest equivalent in the American AISC Shapes Database. W 18X46 carries more bending: 1486.3 cm³ of plastic modulus against 1450 cm³, 2.4% more. They weigh essentially the same, 67.2 kg/m and 68.5 kg/m. Both are about 459 mm deep, so either fits the same construction zone.
| Property | UB 457×152×67 UB | W 18X46 W | Difference |
|---|---|---|---|
| Mass | 67.2 kg/m | 68.5 kg/m | -1.9% |
| Depth | 458 mm | 459.7 mm | -0.4% |
| Width | 153.8 mm | 153.9 mm | -0.1% |
| Web thickness | 9 mm | 9.1 mm | -1.1% |
| Flange thickness | 15 mm | 15.4 mm | -2.6% |
| Area | 85.6 cm² | 87.1 cm² | -1.7% |
| Second moment, major (Iy) | 28,900 cm⁴ | 29,636 cm⁴ | -2.5% |
| Plastic modulus, major (Wpl,y) | 1,450 cm³ | 1,486.3 cm³ | -2.4% |
| Elastic modulus, major (Wel,y) | 1,260 cm³ | 1,291.3 cm³ | -2.4% |
| Second moment, minor (Iz) | 913 cm⁴ | 936.5 cm⁴ | -2.5% |
| Plastic modulus, minor (Wpl,z) | 187 cm³ | 191.73 cm³ | -2.5% |
| Radius of gyration, minor (iz) | 3.27 cm | 3.28 cm | -0.3% |
| Torsion constant (It) | 47.7 cm⁴ | 50.78 cm⁴ | -6.1% |
UB 457×152×67 to BS EN 10365:2017; W 18X46 to AISC Shapes Database v16.0. Difference is expressed relative to W 18X46.
How to choose between them
On stiffness, W 18X46 has the larger second moment of area: 29,636 cm⁴ against 28,900 cm⁴, a difference of 2.5%. 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 (21.6 against 21.7 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, W 18X46 is the stronger section and UB 457×152×67 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.