UB 533×312×151 vs IPE V 550
UB 533×312×151 is an UB section from the UK Blue Book (SCI P363); IPE V 550 is the closest equivalent in the European (Continental) range. They are close to interchangeable in bending: 4150 cm³ against 4200 cm³ of plastic modulus, a difference of 1.2%. UB 533×312×151 is the lighter of the two at 150.6 kg/m against 159 kg/m, a saving of 5.3% on steel weight. IPE V 550 is deeper, 566 mm against 542.5 mm, which matters where the floor zone is tight.
| Property | UB 533×312×151 UB | IPE V 550 IPE | Difference |
|---|---|---|---|
| Mass | 150.6 kg/m | 159 kg/m | -5.3% |
| Depth | 542.5 mm | 566 mm | -4.2% |
| Width | 312 mm | 216 mm | +44.4% |
| Web thickness | 12.7 mm | 17.1 mm | -25.7% |
| Flange thickness | 20.3 mm | 25.2 mm | -19.4% |
| Area | 192 cm² | 202 cm² | -5.0% |
| Second moment, major (Iy) | 101,000 cm⁴ | 102,000 cm⁴ | -1.0% |
| Plastic modulus, major (Wpl,y) | 4,150 cm³ | 4,200 cm³ | -1.2% |
| Elastic modulus, major (Wel,y) | 3,710 cm³ | 3,620 cm³ | +2.5% |
| Second moment, minor (Iz) | 10,300 cm⁴ | 4,260 cm⁴ | +141.8% |
| Plastic modulus, minor (Wpl,z) | 1,010 cm³ | 632 cm³ | +59.8% |
| Radius of gyration, minor (iz) | 7.32 cm | 4.59 cm | +59.5% |
| Torsion constant (It) | 216 cm⁴ | 372 cm⁴ | -41.9% |
UB 533×312×151 to BS EN 10365:2017; IPE V 550 to EN 10365 · Continental Steel. Difference is expressed relative to IPE V 550.
How to choose between them
On stiffness, IPE V 550 has the larger second moment of area: 102,000 cm⁴ against 101,000 cm⁴, a difference of 1.0%. 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 533×312×151 is the more efficient section: 27.6 against 26.4 cm³ per kg/m, 4.3% 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: UB 533×312×151 has 1010 cm³ of minor-axis plastic modulus against 632 cm³, 59.8% 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. 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 5.3% weight.
In short, IPE V 550 is the stronger section and UB 533×312×151 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.