SHS 180×180×6.3 vs CF SHS 180×180×6.3
SHS 180×180×6.3 is an SHS Hot-finished section from the UK Blue Book (SCI P363); CF SHS 180×180×6.3 is the closest equivalent in the UK Blue Book (SCI P363). SHS 180×180×6.3 carries more bending: 281 cm³ of plastic modulus against 273 cm³, 2.9% more. CF SHS 180×180×6.3 is the lighter of the two at 33.3 kg/m against 34 kg/m, a saving of 2.1% on steel weight. Both are about 180 mm deep, so either fits the same construction zone.
| Property | SHS 180×180×6.3 SHS Hot-finished | CF SHS 180×180×6.3 SHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 34 kg/m | 33.3 kg/m | +2.1% |
| Depth | 180 mm | 180 mm | same |
| Width | 180 mm | 180 mm | same |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 43.3 cm² | 42.4 cm² | +2.1% |
| Second moment, major (Iy) | 2,170 cm⁴ | 2,100 cm⁴ | +3.3% |
| Plastic modulus, major (Wpl,y) | 281 cm³ | 273 cm³ | +2.9% |
| Elastic modulus, major (Wel,y) | 241 cm³ | 233 cm³ | +3.4% |
| Second moment, minor (Iz) | 2,170 cm⁴ | 2,100 cm⁴ | +3.3% |
| Plastic modulus, minor (Wpl,z) | 281 cm³ | 273 cm³ | +2.9% |
| Radius of gyration, minor (iz) | 7.07 cm | 7.03 cm | +0.6% |
| Torsion constant (It) | 3,360 cm⁴ | 3,380 cm⁴ | -0.6% |
SHS 180×180×6.3 to BS EN 10210-2:2006; CF SHS 180×180×6.3 to BS EN 10219-2:2006. Difference is expressed relative to CF SHS 180×180×6.3.
How to choose between them
On stiffness, SHS 180×180×6.3 has the larger second moment of area: 2,170 cm⁴ against 2,100 cm⁴, a difference of 3.3%. 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 (8.3 against 8.2 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.
In short, SHS 180×180×6.3 is the stronger section and CF SHS 180×180×6.3 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.