UB 254×102×28 vs H-250x125x6x9-29
UB 254×102×28 is an UB section from the UK Blue Book (SCI P363); H-250x125x6x9-29 is the closest equivalent in the European (Continental) range. They are close to interchangeable in bending: 353 cm³ against 358 cm³ of plastic modulus, a difference of 1.4%. UB 254×102×28 is the lighter of the two at 28.3 kg/m against 29 kg/m, a saving of 2.4% on steel weight. UB 254×102×28 is deeper, 260.4 mm against 250 mm, which matters where the floor zone is tight.
| Property | UB 254×102×28 UB | H-250x125x6x9-29 MB & MC | Difference |
|---|---|---|---|
| Mass | 28.3 kg/m | 29 kg/m | -2.4% |
| Depth | 260.4 mm | 250 mm | +4.2% |
| Width | 102.2 mm | 125 mm | -18.2% |
| Web thickness | 6.3 mm | 6 mm | +5.0% |
| Flange thickness | 10 mm | 9 mm | +11.1% |
| Area | 36.1 cm² | 37 cm² | -2.4% |
| Second moment, major (Iy) | 4,000 cm⁴ | 3,965 cm⁴ | +0.9% |
| Plastic modulus, major (Wpl,y) | 353 cm³ | 358 cm³ | -1.4% |
| Elastic modulus, major (Wel,y) | 308 cm³ | 317 cm³ | -2.8% |
| Second moment, minor (Iz) | 179 cm⁴ | 294 cm⁴ | -39.1% |
| Plastic modulus, minor (Wpl,z) | 54.8 cm³ | 72.7 cm³ | -24.6% |
| Radius of gyration, minor (iz) | 2.22 cm | 2.82 cm | -21.3% |
| Torsion constant (It) | 9.57 cm⁴ | 8.51 cm⁴ | +12.5% |
UB 254×102×28 to BS EN 10365:2017; H-250x125x6x9-29 to Continental Steel. Difference is expressed relative to H-250x125x6x9-29.
How to choose between them
On stiffness, UB 254×102×28 has the larger second moment of area: 4,000 cm⁴ against 3,965 cm⁴, a difference of 0.9%. 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 (12.5 against 12.3 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: H-250x125x6x9-29 has 72.7 cm³ of minor-axis plastic modulus against 54.8 cm³, 24.6% 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 MB & MC to 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 2.4% weight.
In short, H-250x125x6x9-29 is the stronger section and UB 254×102×28 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.