WT 8X38.5 vs Tee 191×229×41
WT 8X38.5 is an WT section from the American AISC Shapes Database; Tee 191×229×41 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 250.72 cm³ against 250 cm³ of plastic modulus, a difference of 0.3%. Tee 191×229×41 is the lighter of the two at 41 kg/m against 57.3 kg/m, a saving of 39.8% on steel weight. Tee 191×229×41 is deeper, 229.9 mm against 209.8 mm, which matters where the floor zone is tight.
| Property | WT 8X38.5 WT | Tee 191×229×41 Tees (from UB) | Difference |
|---|---|---|---|
| Mass | 57.3 kg/m | 41 kg/m | +39.8% |
| Depth | 209.8 mm | 229.9 mm | -8.7% |
| Width | 261.6 mm | 191.3 mm | +36.7% |
| Web thickness | 11.6 mm | 9.9 mm | +17.2% |
| Flange thickness | 19.3 mm | 16 mm | +20.6% |
| Area | 72.9 cm² | 52.2 cm² | +39.7% |
| Second moment, major (Iy) | 2,368 cm⁴ | 2,470 cm⁴ | -4.1% |
| Plastic modulus, major (Wpl,y) | 250.72 cm³ | 250 cm³ | +0.3% |
| Elastic modulus, major (Wel,y) | 140.76 cm³ | 141 cm³ | -0.2% |
| Second moment, minor (Iz) | 2,880 cm⁴ | 935 cm⁴ | +208.0% |
| Plastic modulus, minor (Wpl,z) | 335.93 cm³ | 152 cm³ | +121.0% |
| Radius of gyration, minor (iz) | 6.27 cm | 4.23 cm | +48.2% |
| Torsion constant (It) | 74.09 cm⁴ | 34.5 cm⁴ | +114.8% |
WT 8X38.5 to AISC Shapes Database v16.0; Tee 191×229×41 to BS EN 10365:2017. Difference is expressed relative to Tee 191×229×41.
How to choose between them
On stiffness, Tee 191×229×41 has the larger second moment of area: 2,470 cm⁴ against 2,368 cm⁴, a difference of 4.1%. 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 of steel, Tee 191×229×41 is the more efficient section: 6.1 against 4.4 cm³ per kg/m, 28.2% 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 8X38.5 has 335.93 cm³ of minor-axis plastic modulus against 152 cm³, 121.0% 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. WT sections are specified to AISC Shapes Database v16.0 and Tees (from UB) to BS EN 10365:2017; 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 39.8% weight.
In short, WT 8X38.5 is the stronger section and Tee 191×229×41 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.