Tee 305×305×119 vs WT 12X81
Tee 305×305×119 is an Tees (from UB) section from the UK Blue Book (SCI P363); WT 12X81 is the closest equivalent in the American AISC Shapes Database. Tee 305×305×119 carries more bending: 894 cm³ of plastic modulus against 873.43 cm³, 2.4% more. They weigh essentially the same, 119 kg/m and 120.5 kg/m. Both are about 318 mm deep, so either fits the same construction zone.
| Property | Tee 305×305×119 Tees (from UB) | WT 12X81 WT | Difference |
|---|---|---|---|
| Mass | 119 kg/m | 120.5 kg/m | -1.2% |
| Depth | 317.9 mm | 317.5 mm | +0.1% |
| Width | 311.4 mm | 330.2 mm | -5.7% |
| Web thickness | 18.4 mm | 17.9 mm | +2.8% |
| Flange thickness | 31.4 mm | 31 mm | +1.3% |
| Area | 152 cm² | 154.2 cm² | -1.4% |
| Second moment, major (Iy) | 12,400 cm⁴ | 12,196 cm⁴ | +1.7% |
| Plastic modulus, major (Wpl,y) | 894 cm³ | 873.43 cm³ | +2.4% |
| Elastic modulus, major (Wel,y) | 501 cm³ | 489.97 cm³ | +2.3% |
| Second moment, minor (Iz) | 7,920 cm⁴ | 9,199 cm⁴ | -13.9% |
| Plastic modulus, minor (Wpl,z) | 787 cm³ | 861.96 cm³ | -8.7% |
| Radius of gyration, minor (iz) | 7.23 cm | 7.75 cm | -6.7% |
| Torsion constant (It) | 391 cm⁴ | 383.8 cm⁴ | +1.9% |
Tee 305×305×119 to BS EN 10365:2017; WT 12X81 to AISC Shapes Database v16.0. Difference is expressed relative to WT 12X81.
How to choose between them
On stiffness, Tee 305×305×119 has the larger second moment of area: 12,400 cm⁴ against 12,196 cm⁴, a difference of 1.7%. 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 305×305×119 is the more efficient section: 7.5 against 7.2 cm³ per kg/m, 3.6% 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 12X81 has 861.96 cm³ of minor-axis plastic modulus against 787 cm³, 8.7% 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 a marginal amount of weight.
In short, Tee 305×305×119 is the stronger section and Tee 305×305×119 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.