Tee 127×152×21 vs WT 6X20
Tee 127×152×21 is an Tees (from UB) section from the UK Blue Book (SCI P363); WT 6X20 is the closest equivalent in the American AISC Shapes Database. Tee 127×152×21 carries more bending: 88.9 cm³ of plastic modulus against 86.524 cm³, 2.7% more. Tee 127×152×21 is the lighter of the two at 20.9 kg/m against 29.8 kg/m, a saving of 29.9% on steel weight. Both are about 153 mm deep, so either fits the same construction zone.
| Property | Tee 127×152×21 Tees (from UB) | WT 6X20 WT | Difference |
|---|---|---|---|
| Mass | 20.9 kg/m | 29.8 kg/m | -29.9% |
| Depth | 153.5 mm | 151.6 mm | +1.3% |
| Width | 124.3 mm | 203.5 mm | -38.9% |
| Web thickness | 8 mm | 7.5 mm | +6.7% |
| Flange thickness | 12.1 mm | 13.1 mm | -7.6% |
| Area | 26.7 cm² | 37.7 cm² | -29.2% |
| Second moment, major (Iy) | 573 cm⁴ | 599.4 cm⁴ | -4.4% |
| Plastic modulus, major (Wpl,y) | 88.9 cm³ | 86.524 cm³ | +2.7% |
| Elastic modulus, major (Wel,y) | 49.9 cm³ | 48.342 cm³ | +3.2% |
| Second moment, minor (Iz) | 194 cm⁴ | 915.7 cm⁴ | -78.8% |
| Plastic modulus, minor (Wpl,z) | 49.2 cm³ | 137.32 cm³ | -64.2% |
| Radius of gyration, minor (iz) | 2.7 cm | 4.93 cm | -45.2% |
| Torsion constant (It) | 10.5 cm⁴ | 18.81 cm⁴ | -44.2% |
Tee 127×152×21 to BS EN 10365:2017; WT 6X20 to AISC Shapes Database v16.0. Difference is expressed relative to WT 6X20.
How to choose between them
On stiffness, WT 6X20 has the larger second moment of area: 599.4 cm⁴ against 573 cm⁴, a difference of 4.4%. 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 127×152×21 is the more efficient section: 4.3 against 2.9 cm³ per kg/m, 46.5% 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 6X20 has 137.32 cm³ of minor-axis plastic modulus against 49.2 cm³, 64.2% 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 WT 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 29.9% weight.
In short, Tee 127×152×21 is the stronger section and Tee 127×152×21 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.