UC 152×152×23 vs W 6X15
UC 152×152×23 is an UC section from the UK Blue Book (SCI P363); W 6X15 is the closest equivalent in the American AISC Shapes Database. UC 152×152×23 carries more bending: 182 cm³ of plastic modulus against 176.98 cm³, 2.8% more. W 6X15 is the lighter of the two at 22.3 kg/m against 23 kg/m, a saving of 3.1% on steel weight. Both are about 152 mm deep, so either fits the same construction zone.
| Property | UC 152×152×23 UC | W 6X15 W | Difference |
|---|---|---|---|
| Mass | 23 kg/m | 22.3 kg/m | +3.1% |
| Depth | 152.4 mm | 152.1 mm | +0.2% |
| Width | 152.2 mm | 152.1 mm | +0.1% |
| Web thickness | 5.8 mm | 5.8 mm | same |
| Flange thickness | 6.8 mm | 6.6 mm | +3.0% |
| Area | 29.2 cm² | 28.6 cm² | +2.1% |
| Second moment, major (Iy) | 1,250 cm⁴ | 1,211 cm⁴ | +3.2% |
| Plastic modulus, major (Wpl,y) | 182 cm³ | 176.98 cm³ | +2.8% |
| Elastic modulus, major (Wel,y) | 164 cm³ | 159.28 cm³ | +3.0% |
| Second moment, minor (Iz) | 400 cm⁴ | 387.9 cm⁴ | +3.1% |
| Plastic modulus, minor (Wpl,z) | 80.1 cm³ | 77.839 cm³ | +2.9% |
| Radius of gyration, minor (iz) | 3.7 cm | 3.68 cm | +0.5% |
| Torsion constant (It) | 4.63 cm⁴ | 4.2 cm⁴ | +10.2% |
UC 152×152×23 to BS EN 10365:2017; W 6X15 to AISC Shapes Database v16.0. Difference is expressed relative to W 6X15.
How to choose between them
On stiffness, UC 152×152×23 has the larger second moment of area: 1,250 cm⁴ against 1,211 cm⁴, a difference of 3.2%. 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 (7.9 against 7.9 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. UC sections are specified to BS EN 10365:2017 and W 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 3.1% weight.
In short, UC 152×152×23 is the stronger section and W 6X15 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.