UC 305×305×158 vs HE 360 B
UC 305×305×158 is an UC section from the UK Blue Book (SCI P363); HE 360 B is the closest equivalent in the European (Continental) range. They are close to interchangeable in bending: 2680 cm³ against 2680 cm³ of plastic modulus, a difference of 0.0%. HE 360 B is the lighter of the two at 142 kg/m against 158.1 kg/m, a saving of 11.3% on steel weight. HE 360 B is deeper, 360 mm against 327.1 mm, which matters where the floor zone is tight.
| Property | UC 305×305×158 UC | HE 360 B HE | Difference |
|---|---|---|---|
| Mass | 158.1 kg/m | 142 kg/m | +11.3% |
| Depth | 327.1 mm | 360 mm | -9.1% |
| Width | 311.2 mm | 300 mm | +3.7% |
| Web thickness | 15.8 mm | 12.5 mm | +26.4% |
| Flange thickness | 25 mm | 22.5 mm | +11.1% |
| Area | 201 cm² | 181 cm² | +11.0% |
| Second moment, major (Iy) | 38,700 cm⁴ | 43,200 cm⁴ | -10.4% |
| Plastic modulus, major (Wpl,y) | 2,680 cm³ | 2,680 cm³ | same |
| Elastic modulus, major (Wel,y) | 2,370 cm³ | 2,400 cm³ | -1.3% |
| Second moment, minor (Iz) | 12,600 cm⁴ | 10,100 cm⁴ | +24.8% |
| Plastic modulus, minor (Wpl,z) | 1,230 cm³ | 1,030 cm³ | +19.4% |
| Radius of gyration, minor (iz) | 7.9 cm | 7.49 cm | +5.5% |
| Torsion constant (It) | 378 cm⁴ | 298 cm⁴ | +26.8% |
UC 305×305×158 to BS EN 10365:2017; HE 360 B to EN 10365 · Continental Steel. Difference is expressed relative to HE 360 B.
How to choose between them
On stiffness, HE 360 B has the larger second moment of area: 43,200 cm⁴ against 38,700 cm⁴, a difference of 10.4%. 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 360 B is the more efficient section: 18.9 against 17.0 cm³ per kg/m, 10.2% 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: UC 305×305×158 has 1230 cm³ of minor-axis plastic modulus against 1030 cm³, 19.4% 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. UC 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 11.3% weight.
In short, HE 360 B is the stronger section and HE 360 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.