UB 610×305×238 vs HE 650 B
UB 610×305×238 is an UB section from the UK Blue Book (SCI P363); HE 650 B is the closest equivalent in the European (Continental) range. UB 610×305×238 carries more bending: 7490 cm³ of plastic modulus against 7320 cm³, 2.3% more. HE 650 B is the lighter of the two at 225 kg/m against 238.1 kg/m, a saving of 5.8% on steel weight. HE 650 B is deeper, 650 mm against 635.8 mm, which matters where the floor zone is tight.
| Property | UB 610×305×238 UB | HE 650 B HE | Difference |
|---|---|---|---|
| Mass | 238.1 kg/m | 225 kg/m | +5.8% |
| Depth | 635.8 mm | 650 mm | -2.2% |
| Width | 311.4 mm | 300 mm | +3.8% |
| Web thickness | 18.4 mm | 16 mm | +15.0% |
| Flange thickness | 31.4 mm | 31 mm | +1.3% |
| Area | 303 cm² | 286 cm² | +5.9% |
| Second moment, major (Iy) | 209,000 cm⁴ | 211,000 cm⁴ | -0.9% |
| Plastic modulus, major (Wpl,y) | 7,490 cm³ | 7,320 cm³ | +2.3% |
| Elastic modulus, major (Wel,y) | 6,590 cm³ | 6,480 cm³ | +1.7% |
| Second moment, minor (Iz) | 15,800 cm⁴ | 14,000 cm⁴ | +12.9% |
| Plastic modulus, minor (Wpl,z) | 1,570 cm³ | 1,440 cm³ | +9.0% |
| Radius of gyration, minor (iz) | 7.23 cm | 6.99 cm | +3.4% |
| Torsion constant (It) | 785 cm⁴ | 749 cm⁴ | +4.8% |
UB 610×305×238 to BS EN 10365:2017; HE 650 B to EN 10365 · Continental Steel. Difference is expressed relative to HE 650 B.
How to choose between them
On stiffness, HE 650 B has the larger second moment of area: 211,000 cm⁴ against 209,000 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 of steel, HE 650 B is the more efficient section: 32.5 against 31.5 cm³ per kg/m, 3.3% 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 610×305×238 has 1570 cm³ of minor-axis plastic modulus against 1440 cm³, 9.0% 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 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 5.8% weight.
In short, UB 610×305×238 is the stronger section and HE 650 B 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.