Tee 127×178×20 vs WT 7X13
Tee 127×178×20 is an Tees (from UB) section from the UK Blue Book (SCI P363); WT 7X13 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 98 cm³ against 96.52 cm³ of plastic modulus, a difference of 1.5%. They weigh essentially the same, 19.5 kg/m and 19.3 kg/m. Both are about 177 mm deep, so either fits the same construction zone.
| Property | Tee 127×178×20 Tees (from UB) | WT 7X13 WT | Difference |
|---|---|---|---|
| Mass | 19.5 kg/m | 19.3 kg/m | +1.0% |
| Depth | 176.6 mm | 176.8 mm | -0.1% |
| Width | 126 mm | 127.8 mm | -1.4% |
| Web thickness | 6.6 mm | 6.5 mm | +1.5% |
| Flange thickness | 10.7 mm | 10.7 mm | same |
| Area | 24.9 cm² | 24.8 cm² | +0.4% |
| Second moment, major (Iy) | 728 cm⁴ | 720.1 cm⁴ | +1.1% |
| Plastic modulus, major (Wpl,y) | 98 cm³ | 96.52 cm³ | +1.5% |
| Elastic modulus, major (Wel,y) | 55 cm³ | 54.241 cm³ | +1.4% |
| Second moment, minor (Iz) | 179 cm⁴ | 185.2 cm⁴ | -3.3% |
| Plastic modulus, minor (Wpl,z) | 44.5 cm³ | 45.228 cm³ | -1.6% |
| Radius of gyration, minor (iz) | 2.68 cm | 2.74 cm | -2.2% |
| Torsion constant (It) | 7.53 cm⁴ | 7.45 cm⁴ | +1.1% |
Tee 127×178×20 to BS EN 10365:2017; WT 7X13 to AISC Shapes Database v16.0. Difference is expressed relative to WT 7X13.
How to choose between them
On stiffness, Tee 127×178×20 has the larger second moment of area: 728 cm⁴ against 720.1 cm⁴, a difference of 1.1%. 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 (5.0 against 5.0 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.