CHS 168.3×5 vs CF CHS 168.3×5
CHS 168.3×5 is an CHS Hot-finished section from the UK Blue Book (SCI P363); CF CHS 168.3×5 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 133 cm³ against 133 cm³ of plastic modulus, a difference of 0.0%. They weigh essentially the same, 20.1 kg/m and 20.1 kg/m. Both are about 168 mm deep, so either fits the same construction zone.
| Property | CHS 168.3×5 CHS Hot-finished | CF CHS 168.3×5 CHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 20.1 kg/m | 20.1 kg/m | same |
| Depth | 168.3 mm | 168.3 mm | same |
| Width | 168.3 mm | 168.3 mm | same |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 25.7 cm² | 25.7 cm² | same |
| Second moment, major (Iy) | 856 cm⁴ | 856 cm⁴ | same |
| Plastic modulus, major (Wpl,y) | 133 cm³ | 133 cm³ | same |
| Elastic modulus, major (Wel,y) | 102 cm³ | 102 cm³ | same |
| Second moment, minor (Iz) | 856 cm⁴ | 856 cm⁴ | same |
| Plastic modulus, minor (Wpl,z) | 133 cm³ | 133 cm³ | same |
| Radius of gyration, minor (iz) | 5.78 cm | 5.78 cm | same |
| Torsion constant (It) | 1,710 cm⁴ | 1,710 cm⁴ | same |
CHS 168.3×5 to BS EN 10210-2:2006; CF CHS 168.3×5 to BS EN 10219-2:2006. Difference is expressed relative to CF CHS 168.3×5.
How to choose between them
On stiffness, CF CHS 168.3×5 has the larger second moment of area: 856 cm⁴ against 856 cm⁴, a difference of 0.0%. 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 (6.6 against 6.6 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, these two are genuine equivalents. Pick whichever your supplier stocks and the rest of the frame already uses.