W 36X318 vs UB 1016×305×437
W 36X318 is an W section from the American AISC Shapes Database; UB 1016×305×437 is the closest equivalent in the UK Blue Book (SCI P363). W 36X318 carries more bending: 21303.2 cm³ of plastic modulus against 20800 cm³, 2.4% more. UB 1016×305×437 is the lighter of the two at 437 kg/m against 473.2 kg/m, a saving of 8.3% on steel weight. UB 1016×305×437 is deeper, 1026.1 mm against 970.3 mm, which matters where the floor zone is tight.
| Property | W 36X318 W | UB 1016×305×437 UB | Difference |
|---|---|---|---|
| Mass | 473.2 kg/m | 437 kg/m | +8.3% |
| Depth | 970.3 mm | 1026.1 mm | -5.4% |
| Width | 315 mm | 305.4 mm | +3.1% |
| Web thickness | 30 mm | 26.9 mm | +11.5% |
| Flange thickness | 54.1 mm | 49 mm | +10.4% |
| Area | 602.6 cm² | 557 cm² | +8.2% |
| Second moment, major (Iy) | 882,411 cm⁴ | 910,000 cm⁴ | -3.0% |
| Plastic modulus, major (Wpl,y) | 21,303.2 cm³ | 20,800 cm³ | +2.4% |
| Elastic modulus, major (Wel,y) | 18,189.6 cm³ | 17,700 cm³ | +2.8% |
| Second moment, minor (Iz) | 28,387 cm⁴ | 23,400 cm⁴ | +21.3% |
| Plastic modulus, minor (Wpl,z) | 2,884.1 cm³ | 2,470 cm³ | +16.8% |
| Radius of gyration, minor (iz) | 6.86 cm | 6.49 cm | +5.7% |
| Torsion constant (It) | 4,092 cm⁴ | 3,190 cm⁴ | +28.3% |
W 36X318 to AISC Shapes Database v16.0; UB 1016×305×437 to BS EN 10365:2017. Difference is expressed relative to UB 1016×305×437.
How to choose between them
On stiffness, UB 1016×305×437 has the larger second moment of area: 910,000 cm⁴ against 882,411 cm⁴, a difference of 3.0%. 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 1016×305×437 is the more efficient section: 47.6 against 45.0 cm³ per kg/m, 5.4% 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 36X318 has 2884.1 cm³ of minor-axis plastic modulus against 2470 cm³, 16.8% 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 8.3% weight.
In short, W 36X318 is the stronger section and UB 1016×305×437 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.