CHS 76.1×4.5 vs PIPE 2-1-2STD
CHS 76.1×4.5 is an CHS Hot-finished section from the UK Blue Book (SCI P363); PIPE 2-1-2STD is the closest equivalent in the American AISC Shapes Database. CHS 76.1×4.5 carries more bending: 23.1 cm³ of plastic modulus against 22.45 cm³, 2.9% more. CHS 76.1×4.5 is the lighter of the two at 7.95 kg/m against 8.6 kg/m, a saving of 7.6% on steel weight. CHS 76.1×4.5 is deeper, 76.1 mm against 73 mm, which matters where the floor zone is tight.
| Property | CHS 76.1×4.5 CHS Hot-finished | PIPE 2-1-2STD Pipe | Difference |
|---|---|---|---|
| Mass | 8 kg/m | 8.6 kg/m | -7.6% |
| Depth | 76.1 mm | 73 mm | +4.2% |
| Width | 76.1 mm | 73 mm | +4.2% |
| Web thickness | 0 mm | 4.8 mm | -100.0% |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 10.1 cm² | 10.4 cm² | -2.9% |
| Second moment, major (Iy) | 65.1 cm⁴ | 60.35 cm⁴ | +7.9% |
| Plastic modulus, major (Wpl,y) | 23.1 cm³ | 22.45 cm³ | +2.9% |
| Elastic modulus, major (Wel,y) | 17.1 cm³ | 16.551 cm³ | +3.3% |
| Second moment, minor (Iz) | 65.1 cm⁴ | 60.35 cm⁴ | +7.9% |
| Plastic modulus, minor (Wpl,z) | 23.1 cm³ | 22.45 cm³ | +2.9% |
| Radius of gyration, minor (iz) | 2.54 cm | 2.42 cm | +5.0% |
| Torsion constant (It) | 130 cm⁴ | 120.3 cm⁴ | +8.1% |
CHS 76.1×4.5 to BS EN 10210-2:2006; PIPE 2-1-2STD to AISC Shapes Database v16.0. Difference is expressed relative to PIPE 2-1-2STD.
How to choose between them
On stiffness, CHS 76.1×4.5 has the larger second moment of area: 65.1 cm⁴ against 60.35 cm⁴, a difference of 7.9%. 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 76.1×4.5 is the more efficient section: 2.9 against 2.6 cm³ per kg/m, 11.3% 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 7.6% weight.
In short, CHS 76.1×4.5 is the stronger section and CHS 76.1×4.5 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.