Tee 146×127×22 vs ST 5X12.7
Tee 146×127×22 is an Tees (from UB) section from the UK Blue Book (SCI P363); ST 5X12.7 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 59.5 cm³ against 60.632 cm³ of plastic modulus, a difference of 1.9%. ST 5X12.7 is the lighter of the two at 18.9 kg/m against 21.5 kg/m, a saving of 13.8% on steel weight. Tee 146×127×22 is deeper, 129.7 mm against 127 mm, which matters where the floor zone is tight.
| Property | Tee 146×127×22 Tees (from UB) | ST 5X12.7 ST | Difference |
|---|---|---|---|
| Mass | 21.5 kg/m | 18.9 kg/m | +13.8% |
| Depth | 129.7 mm | 127 mm | +2.1% |
| Width | 147.3 mm | 118.4 mm | +24.4% |
| Web thickness | 7.2 mm | 7.9 mm | -8.9% |
| Flange thickness | 12.7 mm | 12.5 mm | +1.6% |
| Area | 27.4 cm² | 24 cm² | +14.2% |
| Second moment, major (Iy) | 343 cm⁴ | 324.2 cm⁴ | +5.8% |
| Plastic modulus, major (Wpl,y) | 59.5 cm³ | 60.632 cm³ | -1.9% |
| Elastic modulus, major (Wel,y) | 33.2 cm³ | 33.593 cm³ | -1.2% |
| Second moment, minor (Iz) | 339 cm⁴ | 139.9 cm⁴ | +142.3% |
| Plastic modulus, minor (Wpl,z) | 70.5 cm³ | 40.804 cm³ | +72.8% |
| Radius of gyration, minor (iz) | 3.52 cm | 2.41 cm | +46.1% |
| Torsion constant (It) | 11.9 cm⁴ | 12.49 cm⁴ | -4.7% |
Tee 146×127×22 to BS EN 10365:2017; ST 5X12.7 to AISC Shapes Database v16.0. Difference is expressed relative to ST 5X12.7.
How to choose between them
On stiffness, Tee 146×127×22 has the larger second moment of area: 343 cm⁴ against 324.2 cm⁴, a difference of 5.8%. 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 5X12.7 is the more efficient section: 3.2 against 2.8 cm³ per kg/m, 13.7% 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 146×127×22 has 70.5 cm³ of minor-axis plastic modulus against 40.804 cm³, 72.8% 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 13.8% weight.
In short, ST 5X12.7 is the stronger section and ST 5X12.7 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.