Tee 178×305×50 vs WT 12X38
Tee 178×305×50 is an Tees (from UB) section from the UK Blue Book (SCI P363); WT 12X38 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 490 cm³ against 493.25 cm³ of plastic modulus, a difference of 0.7%. Tee 178×305×50 is the lighter of the two at 50.1 kg/m against 56.6 kg/m, a saving of 11.5% on steel weight. Both are about 304 mm deep, so either fits the same construction zone.
| Property | Tee 178×305×50 Tees (from UB) | WT 12X38 WT | Difference |
|---|---|---|---|
| Mass | 50.1 kg/m | 56.6 kg/m | -11.5% |
| Depth | 303.7 mm | 304.8 mm | -0.4% |
| Width | 179.2 mm | 228.3 mm | -21.5% |
| Web thickness | 11.3 mm | 11.2 mm | +0.9% |
| Flange thickness | 17.2 mm | 17.3 mm | -0.6% |
| Area | 63.9 cm² | 72.3 cm² | -11.6% |
| Second moment, major (Iy) | 5,890 cm⁴ | 6,285 cm⁴ | -6.3% |
| Plastic modulus, major (Wpl,y) | 490 cm³ | 493.25 cm³ | -0.7% |
| Elastic modulus, major (Wel,y) | 270 cm³ | 276.94 cm³ | -2.5% |
| Second moment, minor (Iz) | 829 cm⁴ | 1,719 cm⁴ | -51.8% |
| Plastic modulus, minor (Wpl,z) | 148 cm³ | 234.34 cm³ | -36.8% |
| Radius of gyration, minor (iz) | 3.6 cm | 4.88 cm | -26.2% |
| Torsion constant (It) | 47.3 cm⁴ | 55.78 cm⁴ | -15.2% |
Tee 178×305×50 to BS EN 10365:2017; WT 12X38 to AISC Shapes Database v16.0. Difference is expressed relative to WT 12X38.
How to choose between them
On stiffness, WT 12X38 has the larger second moment of area: 6,285 cm⁴ against 5,890 cm⁴, a difference of 6.3%. 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 of steel, Tee 178×305×50 is the more efficient section: 9.8 against 8.7 cm³ per kg/m, 12.2% better. Over a floor of repeated beams that difference is real tonnage, though it is often outweighed by whichever section the fabricator can actually source.
The two diverge much more about the minor axis: WT 12X38 has 234.34 cm³ of minor-axis plastic modulus against 148 cm³, 36.8% more. If the member sees any minor-axis bending, or if it is unrestrained over a long length and lateral-torsional buckling governs, that gap decides the comparison even though the major-axis numbers looked equivalent.
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 11.5% weight.
In short, WT 12X38 is the stronger section and Tee 178×305×50 is the lighter one; where those are the same section, it is the clear choice, and where they are not, decide on whether your design is governed by capacity or by tonnage.