SHS 400×400×12.5 vs CF SHS 400×400×12.5
SHS 400×400×12.5 is an SHS Hot-finished section from the UK Blue Book (SCI P363); CF SHS 400×400×12.5 is the closest equivalent in the UK Blue Book (SCI P363). SHS 400×400×12.5 carries more bending: 2780 cm³ of plastic modulus against 2680 cm³, 3.7% more. CF SHS 400×400×12.5 is the lighter of the two at 147 kg/m against 151 kg/m, a saving of 2.7% on steel weight. Both are about 400 mm deep, so either fits the same construction zone.
| Property | SHS 400×400×12.5 SHS Hot-finished | CF SHS 400×400×12.5 SHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 151 kg/m | 147 kg/m | +2.7% |
| Depth | 400 mm | 400 mm | same |
| Width | 400 mm | 400 mm | same |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 192 cm² | 187 cm² | +2.7% |
| Second moment, major (Iy) | 47,800 cm⁴ | 45,900 cm⁴ | +4.1% |
| Plastic modulus, major (Wpl,y) | 2,780 cm³ | 2,680 cm³ | +3.7% |
| Elastic modulus, major (Wel,y) | 2,390 cm³ | 2,290 cm³ | +4.4% |
| Second moment, minor (Iz) | 47,800 cm⁴ | 45,900 cm⁴ | +4.1% |
| Plastic modulus, minor (Wpl,z) | 2,780 cm³ | 2,680 cm³ | +3.7% |
| Radius of gyration, minor (iz) | 15.8 cm | 15.7 cm | +0.6% |
| Torsion constant (It) | 73,900 cm⁴ | 74,600 cm⁴ | -0.9% |
SHS 400×400×12.5 to BS EN 10210-2:2006; CF SHS 400×400×12.5 to BS EN 10219-2:2006. Difference is expressed relative to CF SHS 400×400×12.5.
How to choose between them
On stiffness, SHS 400×400×12.5 has the larger second moment of area: 47,800 cm⁴ against 45,900 cm⁴, a difference of 4.1%. 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 (18.4 against 18.2 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 400×400×12.5 is the stronger section and CF SHS 400×400×12.5 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.