PFC 100×50×10 vs C 4X7.25
PFC 100×50×10 is an PFC section from the UK Blue Book (SCI P363); C 4X7.25 is the closest equivalent in the American AISC Shapes Database. PFC 100×50×10 carries more bending: 48.9 cm³ of plastic modulus against 46.539 cm³, 5.1% more. PFC 100×50×10 is the lighter of the two at 10.2 kg/m against 10.8 kg/m, a saving of 5.6% on steel weight. Both are about 101 mm deep, so either fits the same construction zone.
| Property | PFC 100×50×10 PFC | C 4X7.25 C | Difference |
|---|---|---|---|
| Mass | 10.2 kg/m | 10.8 kg/m | -5.6% |
| Depth | 100 mm | 101.6 mm | -1.6% |
| Width | 50 mm | 43.7 mm | +14.4% |
| Web thickness | 5 mm | 8.2 mm | -39.0% |
| Flange thickness | 8.5 mm | 7.5 mm | +13.3% |
| Area | 13 cm² | 13.7 cm² | -5.1% |
| Second moment, major (Iy) | 208 cm⁴ | 190.6 cm⁴ | +9.1% |
| Plastic modulus, major (Wpl,y) | 48.9 cm³ | 46.539 cm³ | +5.1% |
| Elastic modulus, major (Wel,y) | 41.5 cm³ | 37.526 cm³ | +10.6% |
| Second moment, minor (Iz) | 32.3 cm⁴ | 17.69 cm⁴ | +82.6% |
| Plastic modulus, minor (Wpl,z) | 17.5 cm³ | 11.389 cm³ | +53.7% |
| Radius of gyration, minor (iz) | 1.58 cm | 1.14 cm | +38.6% |
| Torsion constant (It) | 2.53 cm⁴ | 3.4 cm⁴ | -25.6% |
PFC 100×50×10 to BS EN 1993-1-1:2005 / BS 4-1:2005; C 4X7.25 to AISC Shapes Database v16.0. Difference is expressed relative to C 4X7.25.
How to choose between them
On stiffness, PFC 100×50×10 has the larger second moment of area: 208 cm⁴ against 190.6 cm⁴, a difference of 9.1%. 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 100×50×10 is the more efficient section: 4.8 against 4.3 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.
The two diverge much more about the minor axis: PFC 100×50×10 has 17.5 cm³ of minor-axis plastic modulus against 11.389 cm³, 53.7% 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 C 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 5.6% weight.
In short, PFC 100×50×10 is the stronger section and PFC 100×50×10 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.