W 12X210 vs UC 356×406×287
W 12X210 is an W section from the American AISC Shapes Database; UC 356×406×287 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 5702.7 cm³ against 5810 cm³ of plastic modulus, a difference of 1.8%. UC 356×406×287 is the lighter of the two at 287.1 kg/m against 312.5 kg/m, a saving of 8.8% on steel weight. UC 356×406×287 is deeper, 393.6 mm against 373.4 mm, which matters where the floor zone is tight.
| Property | W 12X210 W | UC 356×406×287 UC | Difference |
|---|---|---|---|
| Mass | 312.5 kg/m | 287.1 kg/m | +8.8% |
| Depth | 373.4 mm | 393.6 mm | -5.1% |
| Width | 325.1 mm | 399 mm | -18.5% |
| Web thickness | 30 mm | 22.6 mm | +32.7% |
| Flange thickness | 48.3 mm | 36.5 mm | +32.3% |
| Area | 398.7 cm² | 366 cm² | +8.9% |
| Second moment, major (Iy) | 89,074 cm⁴ | 99,900 cm⁴ | -10.8% |
| Plastic modulus, major (Wpl,y) | 5,702.7 cm³ | 5,810 cm³ | -1.8% |
| Elastic modulus, major (Wel,y) | 4,785 cm³ | 5,070 cm³ | -5.6% |
| Second moment, minor (Iz) | 27,638 cm⁴ | 38,700 cm⁴ | -28.6% |
| Plastic modulus, minor (Wpl,z) | 2,605.5 cm³ | 2,950 cm³ | -11.7% |
| Radius of gyration, minor (iz) | 8.33 cm | 10.3 cm | -19.1% |
| Torsion constant (It) | 2,693 cm⁴ | 1,440 cm⁴ | +87.0% |
W 12X210 to AISC Shapes Database v16.0; UC 356×406×287 to BS EN 10365:2017. Difference is expressed relative to UC 356×406×287.
How to choose between them
On stiffness, UC 356×406×287 has the larger second moment of area: 99,900 cm⁴ against 89,074 cm⁴, a difference of 10.8%. 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, UC 356×406×287 is the more efficient section: 20.2 against 18.2 cm³ per kg/m, 9.8% 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: UC 356×406×287 has 2950 cm³ of minor-axis plastic modulus against 2605.5 cm³, 11.7% 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. W sections are specified to AISC Shapes Database v16.0 and UC to BS EN 10365:2017; 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 8.8% weight.
In short, UC 356×406×287 is the stronger section and UC 356×406×287 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.