IPE 550 vs UB 533×210×109
IPE 550 is an IPE section from the European (Continental) range; UB 533×210×109 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 2790 cm³ against 2830 cm³ of plastic modulus, a difference of 1.4%. IPE 550 is the lighter of the two at 106 kg/m against 109 kg/m, a saving of 2.8% on steel weight. Both are about 545 mm deep, so either fits the same construction zone.
| Property | IPE 550 IPE | UB 533×210×109 UB | Difference |
|---|---|---|---|
| Mass | 106 kg/m | 109 kg/m | -2.8% |
| Depth | 550 mm | 539.5 mm | +1.9% |
| Width | 210 mm | 210.8 mm | -0.4% |
| Web thickness | 11.1 mm | 11.6 mm | -4.3% |
| Flange thickness | 17.2 mm | 18.8 mm | -8.5% |
| Area | 134 cm² | 139 cm² | -3.6% |
| Second moment, major (Iy) | 67,100 cm⁴ | 66,800 cm⁴ | +0.4% |
| Plastic modulus, major (Wpl,y) | 2,790 cm³ | 2,830 cm³ | -1.4% |
| Elastic modulus, major (Wel,y) | 2,440 cm³ | 2,480 cm³ | -1.6% |
| Second moment, minor (Iz) | 2,670 cm⁴ | 2,940 cm⁴ | -9.2% |
| Plastic modulus, minor (Wpl,z) | 401 cm³ | 436 cm³ | -8.0% |
| Radius of gyration, minor (iz) | 4.45 cm | 4.6 cm | -3.3% |
| Torsion constant (It) | 123 cm⁴ | 126 cm⁴ | -2.4% |
IPE 550 to EN 10365 · Continental Steel; UB 533×210×109 to BS EN 10365:2017. Difference is expressed relative to UB 533×210×109.
How to choose between them
On stiffness, IPE 550 has the larger second moment of area: 67,100 cm⁴ against 66,800 cm⁴, a difference of 0.4%. 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 (26.3 against 26.0 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: UB 533×210×109 has 436 cm³ of minor-axis plastic modulus against 401 cm³, 8.0% 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. IPE sections are specified to EN 10365 · Continental Steel 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 2.8% weight.
In short, UB 533×210×109 is the stronger section and IPE 550 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.