UC 356×406×393 vs W 14X257
UC 356×406×393 is an UC section from the UK Blue Book (SCI P363); W 14X257 is the closest equivalent in the American AISC Shapes Database. UC 356×406×393 carries more bending: 8220 cm³ of plastic modulus against 7980.5 cm³, 3.0% more. W 14X257 is the lighter of the two at 382.5 kg/m against 393 kg/m, a saving of 2.7% on steel weight. Both are about 418 mm deep, so either fits the same construction zone.
| Property | UC 356×406×393 UC | W 14X257 W | Difference |
|---|---|---|---|
| Mass | 393 kg/m | 382.5 kg/m | +2.7% |
| Depth | 419 mm | 416.6 mm | +0.6% |
| Width | 407 mm | 406.4 mm | +0.1% |
| Web thickness | 30.6 mm | 30 mm | +2.0% |
| Flange thickness | 49.2 mm | 48 mm | +2.5% |
| Area | 501 cm² | 487.7 cm² | +2.7% |
| Second moment, major (Iy) | 147,000 cm⁴ | 141,519 cm⁴ | +3.9% |
| Plastic modulus, major (Wpl,y) | 8,220 cm³ | 7,980.5 cm³ | +3.0% |
| Elastic modulus, major (Wel,y) | 7,000 cm³ | 6,800.6 cm³ | +2.9% |
| Second moment, minor (Iz) | 55,400 cm⁴ | 53,694 cm⁴ | +3.2% |
| Plastic modulus, minor (Wpl,z) | 4,150 cm³ | 4,031.2 cm³ | +2.9% |
| Radius of gyration, minor (iz) | 10.5 cm | 10.49 cm | +0.1% |
| Torsion constant (It) | 3,550 cm⁴ | 3,292 cm⁴ | +7.8% |
UC 356×406×393 to BS EN 10365:2017; W 14X257 to AISC Shapes Database v16.0. Difference is expressed relative to W 14X257.
How to choose between them
On stiffness, UC 356×406×393 has the larger second moment of area: 147,000 cm⁴ against 141,519 cm⁴, a difference of 3.9%. 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, the two are equally efficient (20.9 against 20.9 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 2.7% weight.
In short, UC 356×406×393 is the stronger section and W 14X257 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.