Tee 133×102×15 vs ST 4X9.2
Tee 133×102×15 is an Tees (from UB) section from the UK Blue Book (SCI P363); ST 4X9.2 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 33.5 cm³ against 33.921 cm³ of plastic modulus, a difference of 1.2%. ST 4X9.2 is the lighter of the two at 13.7 kg/m against 15 kg/m, a saving of 9.5% on steel weight. Both are about 102 mm deep, so either fits the same construction zone.
| Property | Tee 133×102×15 Tees (from UB) | ST 4X9.2 ST | Difference |
|---|---|---|---|
| Mass | 15 kg/m | 13.7 kg/m | +9.5% |
| Depth | 103.3 mm | 101.6 mm | +1.7% |
| Width | 133.9 mm | 101.6 mm | +31.8% |
| Web thickness | 6.4 mm | 6.9 mm | -7.2% |
| Flange thickness | 9.6 mm | 10.8 mm | -11.1% |
| Area | 19.1 cm² | 17.4 cm² | +9.8% |
| Second moment, major (Iy) | 154 cm⁴ | 145.3 cm⁴ | +6.0% |
| Plastic modulus, major (Wpl,y) | 33.5 cm³ | 33.921 cm³ | -1.2% |
| Elastic modulus, major (Wel,y) | 18.8 cm³ | 18.681 cm³ | +0.6% |
| Second moment, minor (Iz) | 192 cm⁴ | 76.59 cm⁴ | +150.7% |
| Plastic modulus, minor (Wpl,z) | 44.1 cm³ | 26.055 cm³ | +69.3% |
| Radius of gyration, minor (iz) | 3.17 cm | 2.1 cm | +51.0% |
| Torsion constant (It) | 5.13 cm⁴ | 6.95 cm⁴ | -26.2% |
Tee 133×102×15 to BS EN 10365:2017; ST 4X9.2 to AISC Shapes Database v16.0. Difference is expressed relative to ST 4X9.2.
How to choose between them
On stiffness, Tee 133×102×15 has the larger second moment of area: 154 cm⁴ against 145.3 cm⁴, a difference of 6.0%. 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 4X9.2 is the more efficient section: 2.5 against 2.2 cm³ per kg/m, 9.8% 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 133×102×15 has 44.1 cm³ of minor-axis plastic modulus against 26.055 cm³, 69.3% 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 9.5% weight.
In short, ST 4X9.2 is the stronger section and ST 4X9.2 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.