UC 356×406×634 vs W 14X426
UC 356×406×634 is an UC section from the UK Blue Book (SCI P363); W 14X426 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 14200 cm³ against 14240.4 cm³ of plastic modulus, a difference of 0.3%. They weigh essentially the same, 633.9 kg/m and 634 kg/m. Both are about 475 mm deep, so either fits the same construction zone.
| Property | UC 356×406×634 UC | W 14X426 W | Difference |
|---|---|---|---|
| Mass | 633.9 kg/m | 634 kg/m | same |
| Depth | 474.6 mm | 475 mm | -0.1% |
| Width | 424 mm | 424.2 mm | same |
| Web thickness | 47.6 mm | 47.8 mm | -0.4% |
| Flange thickness | 77 mm | 77.2 mm | -0.3% |
| Area | 808 cm² | 806.5 cm² | +0.2% |
| Second moment, major (Iy) | 275,000 cm⁴ | 274,713 cm⁴ | +0.1% |
| Plastic modulus, major (Wpl,y) | 14,200 cm³ | 14,240.4 cm³ | -0.3% |
| Elastic modulus, major (Wel,y) | 11,600 cm³ | 11,569.3 cm³ | +0.3% |
| Second moment, minor (Iz) | 98,100 cm⁴ | 98,231 cm⁴ | -0.1% |
| Plastic modulus, minor (Wpl,z) | 7,110 cm³ | 7,112 cm³ | same |
| Radius of gyration, minor (iz) | 11 cm | 11.02 cm | -0.2% |
| Torsion constant (It) | 13,700 cm⁴ | 13,777 cm⁴ | -0.6% |
UC 356×406×634 to BS EN 10365:2017; W 14X426 to AISC Shapes Database v16.0. Difference is expressed relative to W 14X426.
How to choose between them
On stiffness, UC 356×406×634 has the larger second moment of area: 275,000 cm⁴ against 274,713 cm⁴, a difference of 0.1%. 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 (22.4 against 22.5 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.