CHS 101.6×5.6 vs PIPE 3-1-2STD
CHS 101.6×5.6 is an CHS Hot-finished section from the UK Blue Book (SCI P363); PIPE 3-1-2STD is the closest equivalent in the American AISC Shapes Database. CHS 101.6×5.6 carries more bending: 51.7 cm³ of plastic modulus against 49.653 cm³, 4.1% more. CHS 101.6×5.6 is the lighter of the two at 13.3 kg/m against 13.6 kg/m, a saving of 2.2% on steel weight. Both are about 102 mm deep, so either fits the same construction zone.
| Property | CHS 101.6×5.6 CHS Hot-finished | PIPE 3-1-2STD Pipe | Difference |
|---|---|---|---|
| Mass | 13.3 kg/m | 13.6 kg/m | -2.2% |
| Depth | 101.6 mm | 101.6 mm | same |
| Width | 101.6 mm | 101.6 mm | same |
| Web thickness | 0 mm | 5.4 mm | -100.0% |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 16.9 cm² | 16.1 cm² | +5.0% |
| Second moment, major (Iy) | 195 cm⁴ | 188.1 cm⁴ | +3.7% |
| Plastic modulus, major (Wpl,y) | 51.7 cm³ | 49.653 cm³ | +4.1% |
| Elastic modulus, major (Wel,y) | 38.4 cm³ | 37.035 cm³ | +3.7% |
| Second moment, minor (Iz) | 195 cm⁴ | 188.1 cm⁴ | +3.7% |
| Plastic modulus, minor (Wpl,z) | 51.7 cm³ | 49.653 cm³ | +4.1% |
| Radius of gyration, minor (iz) | 3.4 cm | 3.4 cm | same |
| Torsion constant (It) | 390 cm⁴ | 376.3 cm⁴ | +3.6% |
CHS 101.6×5.6 to BS EN 10210-2:2006; PIPE 3-1-2STD to AISC Shapes Database v16.0. Difference is expressed relative to PIPE 3-1-2STD.
How to choose between them
On stiffness, CHS 101.6×5.6 has the larger second moment of area: 195 cm⁴ against 188.1 cm⁴, a difference of 3.7%. 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, CHS 101.6×5.6 is the more efficient section: 3.9 against 3.7 cm³ per kg/m, 6.5% 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 2.2% weight.
In short, CHS 101.6×5.6 is the stronger section and CHS 101.6×5.6 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.