SHS 120×120×8 vs CF SHS 120×120×8
SHS 120×120×8 is an SHS Hot-finished section from the UK Blue Book (SCI P363); CF SHS 120×120×8 is the closest equivalent in the UK Blue Book (SCI P363). SHS 120×120×8 carries more bending: 146 cm³ of plastic modulus against 138 cm³, 5.8% more. CF SHS 120×120×8 is the lighter of the two at 26.4 kg/m against 27.6 kg/m, a saving of 4.5% on steel weight. Both are about 120 mm deep, so either fits the same construction zone.
| Property | SHS 120×120×8 SHS Hot-finished | CF SHS 120×120×8 SHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 27.6 kg/m | 26.4 kg/m | +4.5% |
| Depth | 120 mm | 120 mm | same |
| Width | 120 mm | 120 mm | same |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 35.2 cm² | 33.6 cm² | +4.8% |
| Second moment, major (Iy) | 726 cm⁴ | 677 cm⁴ | +7.2% |
| Plastic modulus, major (Wpl,y) | 146 cm³ | 138 cm³ | +5.8% |
| Elastic modulus, major (Wel,y) | 121 cm³ | 113 cm³ | +7.1% |
| Second moment, minor (Iz) | 726 cm⁴ | 677 cm⁴ | +7.2% |
| Plastic modulus, minor (Wpl,z) | 146 cm³ | 138 cm³ | +5.8% |
| Radius of gyration, minor (iz) | 4.55 cm | 4.49 cm | +1.3% |
| Torsion constant (It) | 1,160 cm⁴ | 1,160 cm⁴ | same |
SHS 120×120×8 to BS EN 10210-2:2006; CF SHS 120×120×8 to BS EN 10219-2:2006. Difference is expressed relative to CF SHS 120×120×8.
How to choose between them
On stiffness, SHS 120×120×8 has the larger second moment of area: 726 cm⁴ against 677 cm⁴, a difference of 7.2%. 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 (5.3 against 5.2 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 120×120×8 is the stronger section and CF SHS 120×120×8 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.