UC 356×368×177 vs W 14X120
UC 356×368×177 is an UC section from the UK Blue Book (SCI P363); W 14X120 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 3460 cm³ against 3474.1 cm³ of plastic modulus, a difference of 0.4%. They weigh essentially the same, 177 kg/m and 178.6 kg/m. Both are about 368 mm deep, so either fits the same construction zone.
| Property | UC 356×368×177 UC | W 14X120 W | Difference |
|---|---|---|---|
| Mass | 177 kg/m | 178.6 kg/m | -0.9% |
| Depth | 368.2 mm | 368.3 mm | same |
| Width | 372.6 mm | 373.4 mm | -0.2% |
| Web thickness | 14.4 mm | 15 mm | -4.0% |
| Flange thickness | 23.8 mm | 23.9 mm | -0.4% |
| Area | 226 cm² | 227.7 cm² | -0.7% |
| Second moment, major (Iy) | 57,100 cm⁴ | 57,440 cm⁴ | -0.6% |
| Plastic modulus, major (Wpl,y) | 3,460 cm³ | 3,474.1 cm³ | -0.4% |
| Elastic modulus, major (Wel,y) | 3,100 cm³ | 3,113.5 cm³ | -0.4% |
| Second moment, minor (Iz) | 20,500 cm⁴ | 20,603 cm⁴ | -0.5% |
| Plastic modulus, minor (Wpl,z) | 1,670 cm³ | 1,671.5 cm³ | -0.1% |
| Radius of gyration, minor (iz) | 9.54 cm | 9.5 cm | +0.4% |
| Torsion constant (It) | 381 cm⁴ | 390 cm⁴ | -2.3% |
UC 356×368×177 to BS EN 10365:2017; W 14X120 to AISC Shapes Database v16.0. Difference is expressed relative to W 14X120.
How to choose between them
On stiffness, W 14X120 has the larger second moment of area: 57,440 cm⁴ against 57,100 cm⁴, a difference of 0.6%. 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 (19.5 against 19.5 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 a marginal amount of weight.
In short, these two are genuine equivalents. Pick whichever your supplier stocks and the rest of the frame already uses.