W 33X141 vs UB 914×305×201
W 33X141 is an W section from the American AISC Shapes Database; UB 914×305×201 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 8423 cm³ against 8350 cm³ of plastic modulus, a difference of 0.9%. UB 914×305×201 is the lighter of the two at 200.9 kg/m against 209.8 kg/m, a saving of 4.4% on steel weight. UB 914×305×201 is deeper, 903 mm against 845.8 mm, which matters where the floor zone is tight.
| Property | W 33X141 W | UB 914×305×201 UB | Difference |
|---|---|---|---|
| Mass | 209.8 kg/m | 200.9 kg/m | +4.4% |
| Depth | 845.8 mm | 903 mm | -6.3% |
| Width | 292.1 mm | 303.3 mm | -3.7% |
| Web thickness | 15.4 mm | 15.1 mm | +2.0% |
| Flange thickness | 24.4 mm | 20.2 mm | +20.8% |
| Area | 267.7 cm² | 256 cm² | +4.6% |
| Second moment, major (Iy) | 310,092 cm⁴ | 325,000 cm⁴ | -4.6% |
| Plastic modulus, major (Wpl,y) | 8,423 cm³ | 8,350 cm³ | +0.9% |
| Elastic modulus, major (Wel,y) | 7,341.4 cm³ | 7,200 cm³ | +2.0% |
| Second moment, minor (Iz) | 10,239 cm⁴ | 9,420 cm⁴ | +8.7% |
| Plastic modulus, minor (Wpl,z) | 1,096.3 cm³ | 982 cm³ | +11.6% |
| Radius of gyration, minor (iz) | 6.17 cm | 6.07 cm | +1.6% |
| Torsion constant (It) | 403.7 cm⁴ | 291 cm⁴ | +38.7% |
W 33X141 to AISC Shapes Database v16.0; UB 914×305×201 to BS EN 10365:2017. Difference is expressed relative to UB 914×305×201.
How to choose between them
On stiffness, UB 914×305×201 has the larger second moment of area: 325,000 cm⁴ against 310,092 cm⁴, a difference of 4.6%. 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 914×305×201 is the more efficient section: 41.6 against 40.1 cm³ per kg/m, 3.4% 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 33X141 has 1096.3 cm³ of minor-axis plastic modulus against 982 cm³, 11.6% 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 4.4% weight.
In short, W 33X141 is the stronger section and UB 914×305×201 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.