RHS 160×80×8.8 vs CF RHS 160×80×10
RHS 160×80×8.8 is an RHS Hot-finished section from the UK Blue Book (SCI P363); CF RHS 160×80×10 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 189 cm³ against 191 cm³ of plastic modulus, a difference of 1.0%. RHS 160×80×8.8 is the lighter of the two at 30.1 kg/m against 31.8 kg/m, a saving of 5.3% on steel weight. Both are about 160 mm deep, so either fits the same construction zone.
| Property | RHS 160×80×8.8 RHS Hot-finished | CF RHS 160×80×10 RHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 30.1 kg/m | 31.8 kg/m | -5.3% |
| Depth | 160 mm | 160 mm | same |
| Width | 80 mm | 80 mm | same |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 38.3 cm² | 40.6 cm² | -5.7% |
| Second moment, major (Iy) | 1,170 cm⁴ | 1,150 cm⁴ | +1.7% |
| Plastic modulus, major (Wpl,y) | 189 cm³ | 191 cm³ | -1.0% |
| Elastic modulus, major (Wel,y) | 147 cm³ | 143 cm³ | +2.8% |
| Second moment, minor (Iz) | 379 cm⁴ | 380 cm⁴ | -0.3% |
| Plastic modulus, minor (Wpl,z) | 114 cm³ | 117 cm³ | -2.6% |
| Radius of gyration, minor (iz) | 3.15 cm | 3.06 cm | +2.9% |
| Torsion constant (It) | 949 cm⁴ | 1,030 cm⁴ | -7.9% |
RHS 160×80×8.8 to BS EN 10210-2:2006; CF RHS 160×80×10 to BS EN 10219-2:2006. Difference is expressed relative to CF RHS 160×80×10.
How to choose between them
On stiffness, RHS 160×80×8.8 has the larger second moment of area: 1,170 cm⁴ against 1,150 cm⁴, a difference of 1.7%. 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 of steel, RHS 160×80×8.8 is the more efficient section: 6.3 against 6.0 cm³ per kg/m, 4.5% better. Over a floor of repeated beams that difference is real tonnage, though it is often outweighed by whichever section the fabricator can actually source.
In short, CF RHS 160×80×10 is the stronger section and RHS 160×80×8.8 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.