PFC 260×90×35 vs PFC 260×90
PFC 260×90×35 is a PFC section from the UK Blue Book (SCI P363); PFC 260×90 is the closest equivalent in the European (Continental) range. They are close to interchangeable in bending: 425 cm³ against 425 cm³ of plastic modulus, a difference of 0.0%. They weigh essentially the same, 34.8 kg/m and 34.8 kg/m. Both are about 260 mm deep, so either fits the same construction zone.
| Property | PFC 260×90×35 PFC | PFC 260×90 PFC | Difference |
|---|---|---|---|
| Mass | 34.8 kg/m | 34.8 kg/m | same |
| Depth | 260 mm | 260 mm | same |
| Width | 90 mm | 90 mm | same |
| Web thickness | 8 mm | 8 mm | same |
| Flange thickness | 14 mm | 14 mm | same |
| Area | 44.4 cm² | 44.4 cm² | same |
| Second moment, major (Iy) | 4,730 cm⁴ | 4,728 cm⁴ | same |
| Plastic modulus, major (Wpl,y) | 425 cm³ | 425 cm³ | same |
| Elastic modulus, major (Wel,y) | 364 cm³ | 364 cm³ | same |
| Second moment, minor (Iz) | 353 cm⁴ | 353 cm⁴ | same |
| Plastic modulus, minor (Wpl,z) | 102 cm³ | 102 cm³ | same |
| Radius of gyration, minor (iz) | 2.82 cm | 2.82 cm | same |
| Torsion constant (It) | 20.6 cm⁴ | 20.6 cm⁴ | same |
PFC 260×90×35 to BS EN 1993-1-1:2005 / BS 4-1:2005; PFC 260×90 to Continental Steel. Difference is expressed relative to PFC 260×90.
How to choose between them
On stiffness, PFC 260×90×35 has the larger second moment of area: 4,730 cm⁴ against 4,728 cm⁴, a difference of 0.0%. 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 (12.2 against 12.2 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.
These come from different catalogues, so treat the swap as a design change rather than a like-for-like substitution. PFC sections are specified to BS EN 1993-1-1:2005 / BS 4-1:2005 and PFC to Continental Steel; 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 a marginal amount of weight.
In short, these two are genuine equivalents. Pick whichever your supplier stocks and the rest of the frame already uses.