UB 914×305×253 vs HE 900 A
UB 914×305×253 is an UB section from the UK Blue Book (SCI P363); HE 900 A is the closest equivalent in the European (Continental) range. They are close to interchangeable in bending: 10900 cm³ against 10800 cm³ of plastic modulus, a difference of 0.9%. They weigh essentially the same, 253.4 kg/m and 252 kg/m. UB 914×305×253 is deeper, 918.4 mm against 890 mm, which matters where the floor zone is tight.
| Property | UB 914×305×253 UB | HE 900 A HE | Difference |
|---|---|---|---|
| Mass | 253.4 kg/m | 252 kg/m | +0.6% |
| Depth | 918.4 mm | 890 mm | +3.2% |
| Width | 305.5 mm | 300 mm | +1.8% |
| Web thickness | 17.3 mm | 16 mm | +8.1% |
| Flange thickness | 27.9 mm | 30 mm | -7.0% |
| Area | 323 cm² | 320 cm² | +0.9% |
| Second moment, major (Iy) | 436,000 cm⁴ | 422,000 cm⁴ | +3.3% |
| Plastic modulus, major (Wpl,y) | 10,900 cm³ | 10,800 cm³ | +0.9% |
| Elastic modulus, major (Wel,y) | 9,500 cm³ | 9,480 cm³ | +0.2% |
| Second moment, minor (Iz) | 13,300 cm⁴ | 13,600 cm⁴ | -2.2% |
| Plastic modulus, minor (Wpl,z) | 1,370 cm³ | 1,410 cm³ | -2.8% |
| Radius of gyration, minor (iz) | 6.42 cm | 6.5 cm | -1.2% |
| Torsion constant (It) | 626 cm⁴ | 749 cm⁴ | -16.4% |
UB 914×305×253 to BS EN 10365:2017; HE 900 A to EN 10365 · Continental Steel. Difference is expressed relative to HE 900 A.
How to choose between them
On stiffness, UB 914×305×253 has the larger second moment of area: 436,000 cm⁴ against 422,000 cm⁴, a difference of 3.3%. 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 (43.0 against 42.9 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 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, these two are genuine equivalents. Pick whichever your supplier stocks and the rest of the frame already uses.