UB 406×140×53 vs W 16X36
UB 406×140×53 is an UB section from the UK Blue Book (SCI P363); W 16X36 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 1030 cm³ against 1048.8 cm³ of plastic modulus, a difference of 1.8%. They weigh essentially the same, 53.3 kg/m and 53.6 kg/m. Both are about 405 mm deep, so either fits the same construction zone.
| Property | UB 406×140×53 UB | W 16X36 W | Difference |
|---|---|---|---|
| Mass | 53.3 kg/m | 53.6 kg/m | -0.6% |
| Depth | 406.6 mm | 403.9 mm | +0.7% |
| Width | 143.3 mm | 177.5 mm | -19.3% |
| Web thickness | 7.9 mm | 7.5 mm | +5.3% |
| Flange thickness | 12.9 mm | 10.9 mm | +18.3% |
| Area | 67.9 cm² | 68.4 cm² | -0.7% |
| Second moment, major (Iy) | 18,300 cm⁴ | 18,647 cm⁴ | -1.9% |
| Plastic modulus, major (Wpl,y) | 1,030 cm³ | 1,048.8 cm³ | -1.8% |
| Elastic modulus, major (Wel,y) | 899 cm³ | 925.87 cm³ | -2.9% |
| Second moment, minor (Iz) | 635 cm⁴ | 1,020 cm⁴ | -37.7% |
| Plastic modulus, minor (Wpl,z) | 139 cm³ | 176.98 cm³ | -21.5% |
| Radius of gyration, minor (iz) | 3.06 cm | 3.86 cm | -20.7% |
| Torsion constant (It) | 29 cm⁴ | 22.68 cm⁴ | +27.9% |
UB 406×140×53 to BS EN 10365:2017; W 16X36 to AISC Shapes Database v16.0. Difference is expressed relative to W 16X36.
How to choose between them
On stiffness, W 16X36 has the larger second moment of area: 18,647 cm⁴ against 18,300 cm⁴, a difference of 1.9%. 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 (19.3 against 19.6 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.
The two diverge much more about the minor axis: W 16X36 has 176.98 cm³ of minor-axis plastic modulus against 139 cm³, 21.5% 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. UB 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.