UC 356×368×153 vs W 14X99
UC 356×368×153 is an UC section from the UK Blue Book (SCI P363); W 14X99 is the closest equivalent in the American AISC Shapes Database. UC 356×368×153 carries more bending: 2960 cm³ of plastic modulus against 2835 cm³, 4.4% more. W 14X99 is the lighter of the two at 147.3 kg/m against 152.9 kg/m, a saving of 3.8% on steel weight. Both are about 361 mm deep, so either fits the same construction zone.
| Property | UC 356×368×153 UC | W 14X99 W | Difference |
|---|---|---|---|
| Mass | 152.9 kg/m | 147.3 kg/m | +3.8% |
| Depth | 362 mm | 360.7 mm | +0.4% |
| Width | 370.5 mm | 370.8 mm | -0.1% |
| Web thickness | 12.3 mm | 12.3 mm | same |
| Flange thickness | 20.7 mm | 19.8 mm | +4.5% |
| Area | 195 cm² | 187.7 cm² | +3.9% |
| Second moment, major (Iy) | 48,600 cm⁴ | 46,202 cm⁴ | +5.2% |
| Plastic modulus, major (Wpl,y) | 2,960 cm³ | 2,835 cm³ | +4.4% |
| Elastic modulus, major (Wel,y) | 2,680 cm³ | 2,572.8 cm³ | +4.2% |
| Second moment, minor (Iz) | 17,600 cm⁴ | 16,733 cm⁴ | +5.2% |
| Plastic modulus, minor (Wpl,z) | 1,430 cm³ | 1,370 cm³ | +4.4% |
| Radius of gyration, minor (iz) | 9.49 cm | 9.42 cm | +0.7% |
| Torsion constant (It) | 251 cm⁴ | 223.5 cm⁴ | +12.3% |
UC 356×368×153 to BS EN 10365:2017; W 14X99 to AISC Shapes Database v16.0. Difference is expressed relative to W 14X99.
How to choose between them
On stiffness, UC 356×368×153 has the larger second moment of area: 48,600 cm⁴ against 46,202 cm⁴, a difference of 5.2%. 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 (19.4 against 19.2 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. 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 3.8% weight.
In short, UC 356×368×153 is the stronger section and W 14X99 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.