UB 610×229×125 vs W 24X84
UB 610×229×125 is an UB section from the UK Blue Book (SCI P363); W 24X84 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 3680 cm³ against 3670.7 cm³ of plastic modulus, a difference of 0.3%. They weigh essentially the same, 125.1 kg/m and 125 kg/m. Both are about 612 mm deep, so either fits the same construction zone.
| Property | UB 610×229×125 UB | W 24X84 W | Difference |
|---|---|---|---|
| Mass | 125.1 kg/m | 125 kg/m | +0.1% |
| Depth | 612.2 mm | 612.1 mm | same |
| Width | 229 mm | 229.1 mm | same |
| Web thickness | 11.9 mm | 11.9 mm | same |
| Flange thickness | 19.6 mm | 19.6 mm | same |
| Area | 159 cm² | 159.4 cm² | -0.3% |
| Second moment, major (Iy) | 98,600 cm⁴ | 98,647 cm⁴ | same |
| Plastic modulus, major (Wpl,y) | 3,680 cm³ | 3,670.7 cm³ | +0.3% |
| Elastic modulus, major (Wel,y) | 3,220 cm³ | 3,211.9 cm³ | +0.3% |
| Second moment, minor (Iz) | 3,930 cm⁴ | 3,929 cm⁴ | same |
| Plastic modulus, minor (Wpl,z) | 535 cm³ | 534.22 cm³ | +0.1% |
| Radius of gyration, minor (iz) | 4.97 cm | 4.95 cm | +0.4% |
| Torsion constant (It) | 154 cm⁴ | 154 cm⁴ | same |
UB 610×229×125 to BS EN 10365:2017; W 24X84 to AISC Shapes Database v16.0. Difference is expressed relative to W 24X84.
How to choose between them
On stiffness, W 24X84 has the larger second moment of area: 98,647 cm⁴ against 98,600 cm⁴, a difference of 0.0%. 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 (29.4 against 29.4 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, these two are genuine equivalents. Pick whichever your supplier stocks and the rest of the frame already uses.