Tee 133×102×13 vs WT 4X6.5
Tee 133×102×13 is an Tees (from UB) section from the UK Blue Book (SCI P363); WT 4X6.5 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 28.7 cm³ against 28.513 cm³ of plastic modulus, a difference of 0.7%. WT 4X6.5 is the lighter of the two at 9.7 kg/m against 12.5 kg/m, a saving of 28.9% on steel weight. Both are about 102 mm deep, so either fits the same construction zone.
| Property | Tee 133×102×13 Tees (from UB) | WT 4X6.5 WT | Difference |
|---|---|---|---|
| Mass | 12.5 kg/m | 9.7 kg/m | +28.9% |
| Depth | 101.5 mm | 101.6 mm | -0.1% |
| Width | 133.2 mm | 101.6 mm | +31.1% |
| Web thickness | 5.7 mm | 5.8 mm | -1.7% |
| Flange thickness | 7.8 mm | 6.5 mm | +20.0% |
| Area | 16 cm² | 12.4 cm² | +29.0% |
| Second moment, major (Iy) | 131 cm⁴ | 120.3 cm⁴ | +8.9% |
| Plastic modulus, major (Wpl,y) | 28.7 cm³ | 28.513 cm³ | +0.7% |
| Elastic modulus, major (Wel,y) | 16.2 cm³ | 15.961 cm³ | +1.5% |
| Second moment, minor (Iz) | 154 cm⁴ | 56.61 cm⁴ | +172.0% |
| Plastic modulus, minor (Wpl,z) | 35.5 cm³ | 17.534 cm³ | +102.5% |
| Radius of gyration, minor (iz) | 3.1 cm | 2.14 cm | +44.9% |
| Torsion constant (It) | 2.97 cm⁴ | 1.8 cm⁴ | +65.0% |
Tee 133×102×13 to BS EN 10365:2017; WT 4X6.5 to AISC Shapes Database v16.0. Difference is expressed relative to WT 4X6.5.
How to choose between them
On stiffness, Tee 133×102×13 has the larger second moment of area: 131 cm⁴ against 120.3 cm⁴, a difference of 8.9%. 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, WT 4X6.5 is the more efficient section: 2.9 against 2.3 cm³ per kg/m, 21.9% 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 133×102×13 has 35.5 cm³ of minor-axis plastic modulus against 17.534 cm³, 102.5% 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 28.9% weight.
In short, Tee 133×102×13 is the stronger section and WT 4X6.5 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.