Tee 191×229×67 vs ST 9X35
Tee 191×229×67 is an Tees (from UB) section from the UK Blue Book (SCI P363); ST 9X35 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 414 cm³ against 411.32 cm³ of plastic modulus, a difference of 0.7%. ST 9X35 is the lighter of the two at 52.1 kg/m against 66.6 kg/m, a saving of 27.8% on steel weight. Tee 191×229×67 is deeper, 240.3 mm against 228.6 mm, which matters where the floor zone is tight.
| Property | Tee 191×229×67 Tees (from UB) | ST 9X35 ST | Difference |
|---|---|---|---|
| Mass | 66.6 kg/m | 52.1 kg/m | +27.8% |
| Depth | 240.3 mm | 228.6 mm | +5.1% |
| Width | 196.7 mm | 158.8 mm | +23.9% |
| Web thickness | 15.3 mm | 18.1 mm | -15.5% |
| Flange thickness | 26.3 mm | 17.6 mm | +49.4% |
| Area | 84.9 cm² | 66.5 cm² | +27.7% |
| Second moment, major (Iy) | 4,180 cm⁴ | 3,517 cm⁴ | +18.9% |
| Plastic modulus, major (Wpl,y) | 414 cm³ | 411.32 cm³ | +0.7% |
| Elastic modulus, major (Wel,y) | 231 cm³ | 229.42 cm³ | +0.7% |
| Second moment, minor (Iz) | 1,670 cm⁴ | 499.5 cm⁴ | +234.3% |
| Plastic modulus, minor (Wpl,z) | 267 cm³ | 117.5 cm³ | +127.2% |
| Radius of gyration, minor (iz) | 4.44 cm | 2.74 cm | +62.0% |
| Torsion constant (It) | 146 cm⁴ | 84.08 cm⁴ | +73.6% |
Tee 191×229×67 to BS EN 10365:2017; ST 9X35 to AISC Shapes Database v16.0. Difference is expressed relative to ST 9X35.
How to choose between them
On stiffness, Tee 191×229×67 has the larger second moment of area: 4,180 cm⁴ against 3,517 cm⁴, a difference of 18.9%. 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 9X35 is the more efficient section: 7.9 against 6.2 cm³ per kg/m, 21.3% 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 191×229×67 has 267 cm³ of minor-axis plastic modulus against 117.5 cm³, 127.2% 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 27.8% weight.
In short, Tee 191×229×67 is the stronger section and ST 9X35 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.