Tee 312×267×91 vs WT 10.5X61
Tee 312×267×91 is an Tees (from UB) section from the UK Blue Book (SCI P363); WT 10.5X61 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 562 cm³ against 562.08 cm³ of plastic modulus, a difference of 0.0%. They weigh essentially the same, 90.7 kg/m and 90.8 kg/m. Both are about 275 mm deep, so either fits the same construction zone.
| Property | Tee 312×267×91 Tees (from UB) | WT 10.5X61 WT | Difference |
|---|---|---|---|
| Mass | 90.7 kg/m | 90.8 kg/m | -0.1% |
| Depth | 275.6 mm | 274.3 mm | +0.5% |
| Width | 314.5 mm | 315 mm | -0.2% |
| Web thickness | 15.2 mm | 15.2 mm | same |
| Flange thickness | 24.4 mm | 24.4 mm | same |
| Area | 116 cm² | 115.5 cm² | +0.4% |
| Second moment, major (Iy) | 6,890 cm⁴ | 6,909 cm⁴ | -0.3% |
| Plastic modulus, major (Wpl,y) | 562 cm³ | 562.08 cm³ | same |
| Elastic modulus, major (Wel,y) | 317 cm³ | 316.27 cm³ | +0.2% |
| Second moment, minor (Iz) | 6,330 cm⁴ | 6,327 cm⁴ | same |
| Plastic modulus, minor (Wpl,z) | 619 cm³ | 619.43 cm³ | -0.1% |
| Radius of gyration, minor (iz) | 7.4 cm | 7.39 cm | +0.1% |
| Torsion constant (It) | 186 cm⁴ | 186.1 cm⁴ | -0.1% |
Tee 312×267×91 to BS EN 10365:2017; WT 10.5X61 to AISC Shapes Database v16.0. Difference is expressed relative to WT 10.5X61.
How to choose between them
On stiffness, WT 10.5X61 has the larger second moment of area: 6,909 cm⁴ against 6,890 cm⁴, a difference of 0.3%. 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 (6.2 against 6.2 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.