UC 305×305×97 vs HE 320 A
UC 305×305×97 is an UC section from the UK Blue Book (SCI P363); HE 320 A is the closest equivalent in the European (Continental) range. HE 320 A carries more bending: 1630 cm³ of plastic modulus against 1590 cm³, 2.5% more. They weigh essentially the same, 96.9 kg/m and 97.6 kg/m. Both are about 309 mm deep, so either fits the same construction zone.
| Property | UC 305×305×97 UC | HE 320 A HE | Difference |
|---|---|---|---|
| Mass | 96.9 kg/m | 97.6 kg/m | -0.7% |
| Depth | 307.9 mm | 310 mm | -0.7% |
| Width | 305.3 mm | 300 mm | +1.8% |
| Web thickness | 9.9 mm | 9 mm | +10.0% |
| Flange thickness | 15.4 mm | 15.5 mm | -0.6% |
| Area | 123 cm² | 124 cm² | -0.8% |
| Second moment, major (Iy) | 22,200 cm⁴ | 22,900 cm⁴ | -3.1% |
| Plastic modulus, major (Wpl,y) | 1,590 cm³ | 1,630 cm³ | -2.5% |
| Elastic modulus, major (Wel,y) | 1,450 cm³ | 1,480 cm³ | -2.0% |
| Second moment, minor (Iz) | 7,310 cm⁴ | 6,980 cm⁴ | +4.7% |
| Plastic modulus, minor (Wpl,z) | 726 cm³ | 710 cm³ | +2.3% |
| Radius of gyration, minor (iz) | 7.69 cm | 7.49 cm | +2.7% |
| Torsion constant (It) | 91.2 cm⁴ | 112 cm⁴ | -18.6% |
UC 305×305×97 to BS EN 10365:2017; HE 320 A to EN 10365 · Continental Steel. Difference is expressed relative to HE 320 A.
How to choose between them
On stiffness, HE 320 A has the larger second moment of area: 22,900 cm⁴ against 22,200 cm⁴, a difference of 3.1%. 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 (16.4 against 16.7 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. 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 a marginal amount of weight.
In short, HE 320 A is the stronger section and UC 305×305×97 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.