Tee 191×229×81 vs ST 10X43
Tee 191×229×81 is an Tees (from UB) section from the UK Blue Book (SCI P363); ST 10X43 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 507 cm³ against 509.64 cm³ of plastic modulus, a difference of 0.5%. ST 10X43 is the lighter of the two at 64 kg/m against 80.7 kg/m, a saving of 26.1% on steel weight. ST 10X43 is deeper, 259.1 mm against 246 mm, which matters where the floor zone is tight.
| Property | Tee 191×229×81 Tees (from UB) | ST 10X43 ST | Difference |
|---|---|---|---|
| Mass | 80.7 kg/m | 64 kg/m | +26.1% |
| Depth | 246 mm | 259.1 mm | -5.1% |
| Width | 199.4 mm | 179.3 mm | +11.2% |
| Web thickness | 18 mm | 16.8 mm | +7.1% |
| Flange thickness | 32 mm | 23.4 mm | +36.8% |
| Area | 103 cm² | 81.9 cm² | +25.8% |
| Second moment, major (Iy) | 5,160 cm⁴ | 5,161 cm⁴ | same |
| Plastic modulus, major (Wpl,y) | 507 cm³ | 509.64 cm³ | -0.5% |
| Elastic modulus, major (Wel,y) | 281 cm³ | 281.86 cm³ | -0.3% |
| Second moment, minor (Iz) | 2,130 cm⁴ | 969.8 cm⁴ | +119.6% |
| Plastic modulus, minor (Wpl,z) | 336 cm³ | 190.09 cm³ | +76.8% |
| Radius of gyration, minor (iz) | 4.55 cm | 3.45 cm | +31.9% |
| Torsion constant (It) | 256 cm⁴ | 137.4 cm⁴ | +86.3% |
Tee 191×229×81 to BS EN 10365:2017; ST 10X43 to AISC Shapes Database v16.0. Difference is expressed relative to ST 10X43.
How to choose between them
On stiffness, ST 10X43 has the larger second moment of area: 5,161 cm⁴ against 5,160 cm⁴, a difference of 0.0%. 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, ST 10X43 is the more efficient section: 8.0 against 6.3 cm³ per kg/m, 21.1% 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: Tee 191×229×81 has 336 cm³ of minor-axis plastic modulus against 190.09 cm³, 76.8% 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 ST 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 26.1% weight.
In short, ST 10X43 is the stronger section and ST 10X43 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.