UC 305×305×240 vs W 14X145
UC 305×305×240 is an UC section from the UK Blue Book (SCI P363); W 14X145 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 4250 cm³ against 4260.6 cm³ of plastic modulus, a difference of 0.2%. W 14X145 is the lighter of the two at 215.8 kg/m against 240 kg/m, a saving of 11.2% on steel weight. W 14X145 is deeper, 375.9 mm against 352.5 mm, which matters where the floor zone is tight.
| Property | UC 305×305×240 UC | W 14X145 W | Difference |
|---|---|---|---|
| Mass | 240 kg/m | 215.8 kg/m | +11.2% |
| Depth | 352.5 mm | 375.9 mm | -6.2% |
| Width | 318.4 mm | 393.7 mm | -19.1% |
| Web thickness | 23 mm | 17.3 mm | +32.9% |
| Flange thickness | 37.7 mm | 27.7 mm | +36.1% |
| Area | 306 cm² | 275.5 cm² | +11.1% |
| Second moment, major (Iy) | 64,200 cm⁴ | 71,176 cm⁴ | -9.8% |
| Plastic modulus, major (Wpl,y) | 4,250 cm³ | 4,260.6 cm³ | -0.2% |
| Elastic modulus, major (Wel,y) | 3,640 cm³ | 3,801.8 cm³ | -4.3% |
| Second moment, minor (Iz) | 20,300 cm⁴ | 28,179 cm⁴ | -28.0% |
| Plastic modulus, minor (Wpl,z) | 1,950 cm³ | 2,179.5 cm³ | -10.5% |
| Radius of gyration, minor (iz) | 8.15 cm | 10.11 cm | -19.4% |
| Torsion constant (It) | 1,270 cm⁴ | 632.7 cm⁴ | +100.7% |
UC 305×305×240 to BS EN 10365:2017; W 14X145 to AISC Shapes Database v16.0. Difference is expressed relative to W 14X145.
How to choose between them
On stiffness, W 14X145 has the larger second moment of area: 71,176 cm⁴ against 64,200 cm⁴, a difference of 9.8%. 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, W 14X145 is the more efficient section: 19.7 against 17.7 cm³ per kg/m, 10.3% 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: W 14X145 has 2179.5 cm³ of minor-axis plastic modulus against 1950 cm³, 10.5% 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. 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 11.2% weight.
In short, W 14X145 is the stronger section and W 14X145 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.