SHS 90×90×5 vs CF SHS 90×90×5
SHS 90×90×5 is an SHS Hot-finished section from the UK Blue Book (SCI P363); CF SHS 90×90×5 is the closest equivalent in the UK Blue Book (SCI P363). SHS 90×90×5 carries more bending: 53 cm³ of plastic modulus against 51.4 cm³, 3.1% more. CF SHS 90×90×5 is the lighter of the two at 12.8 kg/m against 13.1 kg/m, a saving of 2.3% on steel weight. Both are about 90 mm deep, so either fits the same construction zone.
| Property | SHS 90×90×5 SHS Hot-finished | CF SHS 90×90×5 SHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 13.1 kg/m | 12.8 kg/m | +2.3% |
| Depth | 90 mm | 90 mm | same |
| Width | 90 mm | 90 mm | same |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 16.7 cm² | 16.4 cm² | +1.8% |
| Second moment, major (Iy) | 200 cm⁴ | 193 cm⁴ | +3.6% |
| Plastic modulus, major (Wpl,y) | 53 cm³ | 51.4 cm³ | +3.1% |
| Elastic modulus, major (Wel,y) | 44.4 cm³ | 42.9 cm³ | +3.5% |
| Second moment, minor (Iz) | 200 cm⁴ | 193 cm⁴ | +3.6% |
| Plastic modulus, minor (Wpl,z) | 53 cm³ | 51.4 cm³ | +3.1% |
| Radius of gyration, minor (iz) | 3.45 cm | 3.43 cm | +0.6% |
| Torsion constant (It) | 316 cm⁴ | 316 cm⁴ | same |
SHS 90×90×5 to BS EN 10210-2:2006; CF SHS 90×90×5 to BS EN 10219-2:2006. Difference is expressed relative to CF SHS 90×90×5.
How to choose between them
On stiffness, SHS 90×90×5 has the larger second moment of area: 200 cm⁴ against 193 cm⁴, a difference of 3.6%. 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 (4.0 against 4.0 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 90×90×5 is the stronger section and CF SHS 90×90×5 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.