W 36X350 vs UB 1016×305×487
W 36X350 is an W section from the American AISC Shapes Database; UB 1016×305×487 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 23597.4 cm³ against 23200 cm³ of plastic modulus, a difference of 1.7%. UB 1016×305×487 is the lighter of the two at 486.7 kg/m against 520.9 kg/m, a saving of 7.0% on steel weight. UB 1016×305×487 is deeper, 1036.3 mm against 980.4 mm, which matters where the floor zone is tight.
| Property | W 36X350 W | UB 1016×305×487 UB | Difference |
|---|---|---|---|
| Mass | 520.9 kg/m | 486.7 kg/m | +7.0% |
| Depth | 980.4 mm | 1036.3 mm | -5.4% |
| Width | 320 mm | 308.5 mm | +3.7% |
| Web thickness | 33 mm | 30 mm | +10.0% |
| Flange thickness | 58.9 mm | 54.1 mm | +8.9% |
| Area | 664.5 cm² | 620 cm² | +7.2% |
| Second moment, major (Iy) | 982,306 cm⁴ | 1,022,000 cm⁴ | -3.9% |
| Plastic modulus, major (Wpl,y) | 23,597.4 cm³ | 23,200 cm³ | +1.7% |
| Elastic modulus, major (Wel,y) | 19,992.2 cm³ | 19,700 cm³ | +1.5% |
| Second moment, minor (Iz) | 32,466 cm⁴ | 26,700 cm⁴ | +21.6% |
| Plastic modulus, minor (Wpl,z) | 3,261 cm³ | 2,800 cm³ | +16.5% |
| Radius of gyration, minor (iz) | 6.99 cm | 6.57 cm | +6.4% |
| Torsion constant (It) | 5,369 cm⁴ | 4,300 cm⁴ | +24.9% |
W 36X350 to AISC Shapes Database v16.0; UB 1016×305×487 to BS EN 10365:2017. Difference is expressed relative to UB 1016×305×487.
How to choose between them
On stiffness, UB 1016×305×487 has the larger second moment of area: 1,022,000 cm⁴ against 982,306 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 of steel, UB 1016×305×487 is the more efficient section: 47.7 against 45.3 cm³ per kg/m, 5.0% 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: W 36X350 has 3261 cm³ of minor-axis plastic modulus against 2800 cm³, 16.5% 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. W sections are specified to AISC Shapes Database v16.0 and UB 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 7.0% weight.
In short, W 36X350 is the stronger section and UB 1016×305×487 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.