UB 533×210×122 vs HE 550 AA
UB 533×210×122 is an UB section from the UK Blue Book (SCI P363); HE 550 AA is the closest equivalent in the European (Continental) range. UB 533×210×122 carries more bending: 3200 cm³ of plastic modulus against 3130 cm³, 2.2% more. They weigh essentially the same, 122 kg/m and 120 kg/m. UB 533×210×122 is deeper, 544.5 mm against 522 mm, which matters where the floor zone is tight.
| Property | UB 533×210×122 UB | HE 550 AA HE | Difference |
|---|---|---|---|
| Mass | 122 kg/m | 120 kg/m | +1.7% |
| Depth | 544.5 mm | 522 mm | +4.3% |
| Width | 211.9 mm | 300 mm | -29.4% |
| Web thickness | 12.7 mm | 11.5 mm | +10.4% |
| Flange thickness | 21.3 mm | 15 mm | +42.0% |
| Area | 155 cm² | 153 cm² | +1.3% |
| Second moment, major (Iy) | 76,000 cm⁴ | 72,900 cm⁴ | +4.3% |
| Plastic modulus, major (Wpl,y) | 3,200 cm³ | 3,130 cm³ | +2.2% |
| Elastic modulus, major (Wel,y) | 2,790 cm³ | 2,790 cm³ | same |
| Second moment, minor (Iz) | 3,390 cm⁴ | 6,770 cm⁴ | -49.9% |
| Plastic modulus, minor (Wpl,z) | 500 cm³ | 699 cm³ | -28.5% |
| Radius of gyration, minor (iz) | 4.67 cm | 6.65 cm | -29.8% |
| Torsion constant (It) | 178 cm⁴ | 127 cm⁴ | +40.2% |
UB 533×210×122 to BS EN 10365:2017; HE 550 AA to EN 10365 · Continental Steel. Difference is expressed relative to HE 550 AA.
How to choose between them
On stiffness, UB 533×210×122 has the larger second moment of area: 76,000 cm⁴ against 72,900 cm⁴, a difference of 4.3%. 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 26.1 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: HE 550 AA has 699 cm³ of minor-axis plastic modulus against 500 cm³, 28.5% 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. UB sections are specified to BS EN 10365:2017 and HE 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, UB 533×210×122 is the stronger section and HE 550 AA 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.