CHS 42.4×3.2 vs PIPE 1-1-4STD
CHS 42.4×3.2 is an CHS Hot-finished section from the UK Blue Book (SCI P363); PIPE 1-1-4STD is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 4.93 cm³ against 4.998 cm³ of plastic modulus, a difference of 1.4%. CHS 42.4×3.2 is the lighter of the two at 3.09 kg/m against 3.4 kg/m, a saving of 9.1% on steel weight. Both are about 42 mm deep, so either fits the same construction zone.
| Property | CHS 42.4×3.2 CHS Hot-finished | PIPE 1-1-4STD Pipe | Difference |
|---|---|---|---|
| Mass | 3.1 kg/m | 3.4 kg/m | -9.1% |
| Depth | 42.4 mm | 42.2 mm | +0.5% |
| Width | 42.4 mm | 42.2 mm | +0.5% |
| Web thickness | 0 mm | 3.3 mm | -100.0% |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 3.9 cm² | 4 cm² | -1.5% |
| Second moment, major (Iy) | 7.62 cm⁴ | 7.66 cm⁴ | -0.5% |
| Plastic modulus, major (Wpl,y) | 4.93 cm³ | 4.998 cm³ | -1.4% |
| Elastic modulus, major (Wel,y) | 3.59 cm³ | 3.638 cm³ | -1.3% |
| Second moment, minor (Iz) | 7.62 cm⁴ | 7.66 cm⁴ | -0.5% |
| Plastic modulus, minor (Wpl,z) | 4.93 cm³ | 4.998 cm³ | -1.4% |
| Radius of gyration, minor (iz) | 1.39 cm | 1.38 cm | +0.7% |
| Torsion constant (It) | 15.2 cm⁴ | 15.32 cm⁴ | -0.8% |
CHS 42.4×3.2 to BS EN 10210-2:2006; PIPE 1-1-4STD to AISC Shapes Database v16.0. Difference is expressed relative to PIPE 1-1-4STD.
How to choose between them
On stiffness, PIPE 1-1-4STD has the larger second moment of area: 7.66 cm⁴ against 7.62 cm⁴, a difference of 0.5%. 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, CHS 42.4×3.2 is the more efficient section: 1.6 against 1.5 cm³ per kg/m, 8.5% 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.
These come from different catalogues, so treat the swap as a design change rather than a like-for-like substitution. CHS Hot-finished sections are specified to BS EN 10210-2:2006 and Pipe to AISC Shapes Database v16.0; the steel grades, tolerances and available lengths differ, connection details and bolt gauges are set out differently, and the two are rarely both stocked in the same market. Check availability before changing a section on a drawing to save 9.1% weight.
In short, PIPE 1-1-4STD is the stronger section and CHS 42.4×3.2 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.