PFC 260×90×35 vs MC 10X25
PFC 260×90×35 is an PFC section from the UK Blue Book (SCI P363); MC 10X25 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 425 cm³ against 429.34 cm³ of plastic modulus, a difference of 1.0%. PFC 260×90×35 is the lighter of the two at 34.8 kg/m against 37.2 kg/m, a saving of 6.5% on steel weight. PFC 260×90×35 is deeper, 260 mm against 254 mm, which matters where the floor zone is tight.
| Property | PFC 260×90×35 PFC | MC 10X25 MC | Difference |
|---|---|---|---|
| Mass | 34.8 kg/m | 37.2 kg/m | -6.5% |
| Depth | 260 mm | 254 mm | +2.4% |
| Width | 90 mm | 86.6 mm | +3.9% |
| Web thickness | 8 mm | 9.7 mm | -17.5% |
| Flange thickness | 14 mm | 14.6 mm | -4.1% |
| Area | 44.4 cm² | 47.4 cm² | -6.3% |
| Second moment, major (Iy) | 4,730 cm⁴ | 4,579 cm⁴ | +3.3% |
| Plastic modulus, major (Wpl,y) | 425 cm³ | 429.34 cm³ | -1.0% |
| Elastic modulus, major (Wel,y) | 364 cm³ | 360.52 cm³ | +1.0% |
| Second moment, minor (Iz) | 353 cm⁴ | 301.8 cm⁴ | +17.0% |
| Plastic modulus, minor (Wpl,z) | 102 cm³ | 92.587 cm³ | +10.2% |
| Radius of gyration, minor (iz) | 2.82 cm | 2.52 cm | +11.9% |
| Torsion constant (It) | 20.6 cm⁴ | 26.56 cm⁴ | -22.4% |
PFC 260×90×35 to BS EN 1993-1-1:2005 / BS 4-1:2005; MC 10X25 to AISC Shapes Database v16.0. Difference is expressed relative to MC 10X25.
How to choose between them
On stiffness, PFC 260×90×35 has the larger second moment of area: 4,730 cm⁴ against 4,579 cm⁴, a difference of 3.3%. 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, PFC 260×90×35 is the more efficient section: 12.2 against 11.5 cm³ per kg/m, 5.8% 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.
The two diverge much more about the minor axis: PFC 260×90×35 has 102 cm³ of minor-axis plastic modulus against 92.587 cm³, 10.2% more. If the member sees any minor-axis bending, or if it is unrestrained over a long length and lateral-torsional buckling governs, that gap decides the comparison even though the major-axis numbers looked equivalent.
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 MC 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 6.5% weight.
In short, MC 10X25 is the stronger section and PFC 260×90×35 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.