Tee 229×305×63 vs WT 12X42
Tee 229×305×63 is an Tees (from UB) section from the UK Blue Book (SCI P363); WT 12X42 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 531 cm³ against 532.58 cm³ of plastic modulus, a difference of 0.3%. They weigh essentially the same, 62.5 kg/m and 62.5 kg/m. Both are about 307 mm deep, so either fits the same construction zone.
| Property | Tee 229×305×63 Tees (from UB) | WT 12X42 WT | Difference |
|---|---|---|---|
| Mass | 62.5 kg/m | 62.5 kg/m | same |
| Depth | 306 mm | 307.3 mm | -0.4% |
| 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 | 79.7 cm² | 80 cm² | -0.4% |
| Second moment, major (Iy) | 6,900 cm⁴ | 6,909 cm⁴ | -0.1% |
| Plastic modulus, major (Wpl,y) | 531 cm³ | 532.58 cm³ | -0.3% |
| Elastic modulus, major (Wel,y) | 299 cm³ | 299.88 cm³ | -0.3% |
| Second moment, minor (Iz) | 1,970 cm⁴ | 1,965 cm⁴ | +0.3% |
| Plastic modulus, minor (Wpl,z) | 268 cm³ | 267.11 cm³ | +0.3% |
| Radius of gyration, minor (iz) | 4.97 cm | 4.95 cm | +0.4% |
| Torsion constant (It) | 76.9 cm⁴ | 76.59 cm⁴ | +0.4% |
Tee 229×305×63 to BS EN 10365:2017; WT 12X42 to AISC Shapes Database v16.0. Difference is expressed relative to WT 12X42.
How to choose between them
On stiffness, WT 12X42 has the larger second moment of area: 6,909 cm⁴ against 6,900 cm⁴, a difference of 0.1%. 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, the two are equally efficient (8.5 against 8.5 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. Tees (from UB) sections are specified to BS EN 10365:2017 and WT 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.