UC 305×305×240 vs HE 320 M
UC 305×305×240 is an UC section from the UK Blue Book (SCI P363); HE 320 M is the closest equivalent in the European (Continental) range. HE 320 M carries more bending: 4440 cm³ of plastic modulus against 4250 cm³, 4.3% more. UC 305×305×240 is the lighter of the two at 240 kg/m against 245 kg/m, a saving of 2.0% on steel weight. Both are about 356 mm deep, so either fits the same construction zone.
| Property | UC 305×305×240 UC | HE 320 M HE | Difference |
|---|---|---|---|
| Mass | 240 kg/m | 245 kg/m | -2.0% |
| Depth | 352.5 mm | 359 mm | -1.8% |
| Width | 318.4 mm | 309 mm | +3.0% |
| Web thickness | 23 mm | 21 mm | +9.5% |
| Flange thickness | 37.7 mm | 40 mm | -5.7% |
| Area | 306 cm² | 312 cm² | -1.9% |
| Second moment, major (Iy) | 64,200 cm⁴ | 68,100 cm⁴ | -5.7% |
| Plastic modulus, major (Wpl,y) | 4,250 cm³ | 4,440 cm³ | -4.3% |
| Elastic modulus, major (Wel,y) | 3,640 cm³ | 3,800 cm³ | -4.2% |
| Second moment, minor (Iz) | 20,300 cm⁴ | 19,700 cm⁴ | +3.0% |
| Plastic modulus, minor (Wpl,z) | 1,950 cm³ | 1,950 cm³ | same |
| Radius of gyration, minor (iz) | 8.15 cm | 7.95 cm | +2.5% |
| Torsion constant (It) | 1,270 cm⁴ | 1,510 cm⁴ | -15.9% |
UC 305×305×240 to BS EN 10365:2017; HE 320 M to EN 10365 · Continental Steel. Difference is expressed relative to HE 320 M.
How to choose between them
On stiffness, HE 320 M has the larger second moment of area: 68,100 cm⁴ against 64,200 cm⁴, a difference of 5.7%. 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, HE 320 M is the more efficient section: 18.1 against 17.7 cm³ per kg/m, 2.3% 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.
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 2.0% weight.
In short, HE 320 M is the stronger section and UC 305×305×240 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.