Tee 254×343×63 vs WT 13.5X42
Tee 254×343×63 is an Tees (from UB) section from the UK Blue Book (SCI P363); WT 13.5X42 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 643 cm³ against 642.37 cm³ of plastic modulus, a difference of 0.1%. They weigh essentially the same, 62.6 kg/m and 62.5 kg/m. Both are about 340 mm deep, so either fits the same construction zone.
| Property | Tee 254×343×63 Tees (from UB) | WT 13.5X42 WT | Difference |
|---|---|---|---|
| Mass | 62.6 kg/m | 62.5 kg/m | +0.2% |
| Depth | 338.9 mm | 340.4 mm | -0.4% |
| Width | 253 mm | 254 mm | -0.4% |
| Web thickness | 11.7 mm | 11.7 mm | same |
| Flange thickness | 16.2 mm | 16.3 mm | -0.6% |
| Area | 79.7 cm² | 80 cm² | -0.4% |
| Second moment, major (Iy) | 8,980 cm⁴ | 8,991 cm⁴ | -0.1% |
| Plastic modulus, major (Wpl,y) | 643 cm³ | 642.37 cm³ | +0.1% |
| Elastic modulus, major (Wel,y) | 358 cm³ | 358.88 cm³ | -0.2% |
| Second moment, minor (Iz) | 2,190 cm⁴ | 2,198 cm⁴ | -0.4% |
| Plastic modulus, minor (Wpl,z) | 271 cm³ | 272.03 cm³ | -0.4% |
| Radius of gyration, minor (iz) | 5.24 cm | 5.26 cm | -0.4% |
| Torsion constant (It) | 57.9 cm⁴ | 58.27 cm⁴ | -0.6% |
Tee 254×343×63 to BS EN 10365:2017; WT 13.5X42 to AISC Shapes Database v16.0. Difference is expressed relative to WT 13.5X42.
How to choose between them
On stiffness, WT 13.5X42 has the larger second moment of area: 8,991 cm⁴ against 8,980 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 (10.3 against 10.3 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.