UB 914×305×289 vs H-900x300x18x34-286
UB 914×305×289 is an UB section from the UK Blue Book (SCI P363); H-900x300x18x34-286 is the closest equivalent in the European (Continental) range. They are close to interchangeable in bending: 12600 cm³ against 12500 cm³ of plastic modulus, a difference of 0.8%. They weigh essentially the same, 289.1 kg/m and 286 kg/m. Both are about 919 mm deep, so either fits the same construction zone.
| Property | UB 914×305×289 UB | H-900x300x18x34-286 MB & MC | Difference |
|---|---|---|---|
| Mass | 289.1 kg/m | 286 kg/m | +1.1% |
| Depth | 926.6 mm | 912 mm | +1.6% |
| Width | 307.7 mm | 302 mm | +1.9% |
| Web thickness | 19.5 mm | 18 mm | +8.3% |
| Flange thickness | 32 mm | 34 mm | -5.9% |
| Area | 368 cm² | 364 cm² | +1.1% |
| Second moment, major (Iy) | 504,000 cm⁴ | 497,800 cm⁴ | +1.2% |
| Plastic modulus, major (Wpl,y) | 12,600 cm³ | 12,500 cm³ | +0.8% |
| Elastic modulus, major (Wel,y) | 10,900 cm³ | 10,920 cm³ | -0.2% |
| Second moment, minor (Iz) | 15,600 cm⁴ | 15,670 cm⁴ | -0.4% |
| Plastic modulus, minor (Wpl,z) | 1,600 cm³ | 1,629 cm³ | -1.8% |
| Radius of gyration, minor (iz) | 6.51 cm | 6.56 cm | -0.8% |
| Torsion constant (It) | 926 cm⁴ | 1,050 cm⁴ | -11.8% |
UB 914×305×289 to BS EN 10365:2017; H-900x300x18x34-286 to Continental Steel. Difference is expressed relative to H-900x300x18x34-286.
How to choose between them
On stiffness, UB 914×305×289 has the larger second moment of area: 504,000 cm⁴ against 497,800 cm⁴, a difference of 1.2%. 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 (43.6 against 43.7 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. 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 a marginal amount of weight.
In short, these two are genuine equivalents. Pick whichever your supplier stocks and the rest of the frame already uses.