UB 533×210×122 vs IPE O 550
UB 533×210×122 is an UB section from the UK Blue Book (SCI P363); IPE O 550 is the closest equivalent in the European (Continental) range. They are close to interchangeable in bending: 3200 cm³ against 3260 cm³ of plastic modulus, a difference of 1.8%. They weigh essentially the same, 122 kg/m and 123 kg/m. IPE O 550 is deeper, 556 mm against 544.5 mm, which matters where the floor zone is tight.
| Property | UB 533×210×122 UB | IPE O 550 IPE | Difference |
|---|---|---|---|
| Mass | 122 kg/m | 123 kg/m | -0.8% |
| Depth | 544.5 mm | 556 mm | -2.1% |
| Width | 211.9 mm | 212 mm | same |
| Web thickness | 12.7 mm | 12.7 mm | same |
| Flange thickness | 21.3 mm | 20.2 mm | +5.4% |
| Area | 155 cm² | 156 cm² | -0.6% |
| Second moment, major (Iy) | 76,000 cm⁴ | 79,200 cm⁴ | -4.0% |
| Plastic modulus, major (Wpl,y) | 3,200 cm³ | 3,260 cm³ | -1.8% |
| Elastic modulus, major (Wel,y) | 2,790 cm³ | 2,850 cm³ | -2.1% |
| Second moment, minor (Iz) | 3,390 cm⁴ | 3,220 cm⁴ | +5.3% |
| Plastic modulus, minor (Wpl,z) | 500 cm³ | 481 cm³ | +4.0% |
| Radius of gyration, minor (iz) | 4.67 cm | 4.55 cm | +2.6% |
| Torsion constant (It) | 178 cm⁴ | 187 cm⁴ | -4.8% |
UB 533×210×122 to BS EN 10365:2017; IPE O 550 to EN 10365 · Continental Steel. Difference is expressed relative to IPE O 550.
How to choose between them
On stiffness, IPE O 550 has the larger second moment of area: 79,200 cm⁴ against 76,000 cm⁴, a difference of 4.0%. 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, the two are equally efficient (26.2 against 26.5 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.
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 IPE to EN 10365 · Continental Steel; 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.