UB 610×305×149 vs H-600x300x12x20-151
UB 610×305×149 is an UB section from the UK Blue Book (SCI P363); H-600x300x12x20-151 is the closest equivalent in the European (Continental) range. UB 610×305×149 carries more bending: 4590 cm³ of plastic modulus against 4489 cm³, 2.2% more. They weigh essentially the same, 149.2 kg/m and 151 kg/m. UB 610×305×149 is deeper, 612.4 mm against 588 mm, which matters where the floor zone is tight.
| Property | UB 610×305×149 UB | H-600x300x12x20-151 MB & MC | Difference |
|---|---|---|---|
| Mass | 149.2 kg/m | 151 kg/m | -1.2% |
| Depth | 612.4 mm | 588 mm | +4.1% |
| Width | 304.8 mm | 300 mm | +1.6% |
| Web thickness | 11.8 mm | 12 mm | -1.7% |
| Flange thickness | 19.7 mm | 20 mm | -1.5% |
| Area | 190 cm² | 192 cm² | -1.0% |
| Second moment, major (Iy) | 126,000 cm⁴ | 118,100 cm⁴ | +6.7% |
| Plastic modulus, major (Wpl,y) | 4,590 cm³ | 4,489 cm³ | +2.2% |
| Elastic modulus, major (Wel,y) | 4,110 cm³ | 4,018 cm³ | +2.3% |
| Second moment, minor (Iz) | 9,310 cm⁴ | 9,025 cm⁴ | +3.2% |
| Plastic modulus, minor (Wpl,z) | 937 cm³ | 928 cm³ | +1.0% |
| Radius of gyration, minor (iz) | 7 cm | 6.85 cm | +2.2% |
| Torsion constant (It) | 200 cm⁴ | 241 cm⁴ | -17.0% |
UB 610×305×149 to BS EN 10365:2017; H-600x300x12x20-151 to Continental Steel. Difference is expressed relative to H-600x300x12x20-151.
How to choose between them
On stiffness, UB 610×305×149 has the larger second moment of area: 126,000 cm⁴ against 118,100 cm⁴, a difference of 6.7%. 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, UB 610×305×149 is the more efficient section: 30.8 against 29.7 cm³ per kg/m, 3.5% 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.
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, UB 610×305×149 is the stronger section and UB 610×305×149 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.