UC 305×305×137 vs W 12X96
UC 305×305×137 is an UC section from the UK Blue Book (SCI P363); W 12X96 is the closest equivalent in the American AISC Shapes Database. W 12X96 carries more bending: 2408.9 cm³ of plastic modulus against 2300 cm³, 4.5% more. UC 305×305×137 is the lighter of the two at 136.9 kg/m against 142.9 kg/m, a saving of 4.2% on steel weight. Both are about 322 mm deep, so either fits the same construction zone.
| Property | UC 305×305×137 UC | W 12X96 W | Difference |
|---|---|---|---|
| Mass | 136.9 kg/m | 142.9 kg/m | -4.2% |
| Depth | 320.5 mm | 322.6 mm | -0.7% |
| Width | 309.2 mm | 309.9 mm | -0.2% |
| Web thickness | 13.8 mm | 14 mm | -1.4% |
| Flange thickness | 21.7 mm | 22.9 mm | -5.2% |
| Area | 174 cm² | 181.9 cm² | -4.3% |
| Second moment, major (Iy) | 32,800 cm⁴ | 34,672 cm⁴ | -5.4% |
| Plastic modulus, major (Wpl,y) | 2,300 cm³ | 2,408.9 cm³ | -4.5% |
| Elastic modulus, major (Wel,y) | 2,050 cm³ | 2,146.7 cm³ | -4.5% |
| Second moment, minor (Iz) | 10,700 cm⁴ | 11,238 cm⁴ | -4.8% |
| Plastic modulus, minor (Wpl,z) | 1,050 cm³ | 1,106.1 cm³ | -5.1% |
| Radius of gyration, minor (iz) | 7.83 cm | 7.85 cm | -0.3% |
| Torsion constant (It) | 249 cm⁴ | 285.1 cm⁴ | -12.7% |
UC 305×305×137 to BS EN 10365:2017; W 12X96 to AISC Shapes Database v16.0. Difference is expressed relative to W 12X96.
How to choose between them
On stiffness, W 12X96 has the larger second moment of area: 34,672 cm⁴ against 32,800 cm⁴, a difference of 5.4%. 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, the two are equally efficient (16.8 against 16.9 cm³ per kg/m), so on a pure steel-tonnage basis there is nothing to choose between them. The decision comes down to availability, connection detailing and what the rest of the frame uses.
These come from different catalogues, so treat the swap as a design change rather than a like-for-like substitution. UC sections are specified to BS EN 10365:2017 and W 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 4.2% weight.
In short, W 12X96 is the stronger section and UC 305×305×137 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.