IPE 400 vs UB 406×178×67
IPE 400 is an IPE section from the European (Continental) range; UB 406×178×67 is the closest equivalent in the UK Blue Book (SCI P363). UB 406×178×67 carries more bending: 1350 cm³ of plastic modulus against 1310 cm³, 3.0% more. They weigh essentially the same, 66.3 kg/m and 67.1 kg/m. UB 406×178×67 is deeper, 409.4 mm against 400 mm, which matters where the floor zone is tight.
| Property | IPE 400 IPE | UB 406×178×67 UB | Difference |
|---|---|---|---|
| Mass | 66.3 kg/m | 67.1 kg/m | -1.2% |
| Depth | 400 mm | 409.4 mm | -2.3% |
| Width | 180 mm | 178.8 mm | +0.7% |
| Web thickness | 8.6 mm | 8.8 mm | -2.3% |
| Flange thickness | 13.5 mm | 14.3 mm | -5.6% |
| Area | 84.5 cm² | 85.5 cm² | -1.2% |
| Second moment, major (Iy) | 23,100 cm⁴ | 24,300 cm⁴ | -4.9% |
| Plastic modulus, major (Wpl,y) | 1,310 cm³ | 1,350 cm³ | -3.0% |
| Elastic modulus, major (Wel,y) | 1,160 cm³ | 1,190 cm³ | -2.5% |
| Second moment, minor (Iz) | 1,320 cm⁴ | 1,360 cm⁴ | -2.9% |
| Plastic modulus, minor (Wpl,z) | 229 cm³ | 237 cm³ | -3.4% |
| Radius of gyration, minor (iz) | 3.95 cm | 3.99 cm | -1.0% |
| Torsion constant (It) | 51.3 cm⁴ | 46.1 cm⁴ | +11.3% |
IPE 400 to EN 10365 · Continental Steel; UB 406×178×67 to BS EN 10365:2017. Difference is expressed relative to UB 406×178×67.
How to choose between them
On stiffness, UB 406×178×67 has the larger second moment of area: 24,300 cm⁴ against 23,100 cm⁴, a difference of 4.9%. 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 (19.8 against 20.1 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.
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 a marginal amount of weight.
In short, UB 406×178×67 is the stronger section and IPE 400 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.