UC 356×368×129 vs HP 14X89
UC 356×368×129 is an UC section from the UK Blue Book (SCI P363); HP 14X89 is the closest equivalent in the American AISC Shapes Database. UC 356×368×129 carries more bending: 2480 cm³ of plastic modulus against 2392.5 cm³, 3.7% more. UC 356×368×129 is the lighter of the two at 129 kg/m against 132.4 kg/m, a saving of 2.6% on steel weight. Both are about 353 mm deep, so either fits the same construction zone.
| Property | UC 356×368×129 UC | HP 14X89 HP | Difference |
|---|---|---|---|
| Mass | 129 kg/m | 132.4 kg/m | -2.6% |
| Depth | 355.6 mm | 350.5 mm | +1.5% |
| Width | 368.6 mm | 373.4 mm | -1.3% |
| Web thickness | 10.4 mm | 15.6 mm | -33.3% |
| Flange thickness | 17.5 mm | 15.6 mm | +12.2% |
| Area | 164 cm² | 168.4 cm² | -2.6% |
| Second moment, major (Iy) | 40,200 cm⁴ | 37,627 cm⁴ | +6.8% |
| Plastic modulus, major (Wpl,y) | 2,480 cm³ | 2,392.5 cm³ | +3.7% |
| Elastic modulus, major (Wel,y) | 2,260 cm³ | 2,146.7 cm³ | +5.3% |
| Second moment, minor (Iz) | 14,600 cm⁴ | 13,569 cm⁴ | +7.6% |
| Plastic modulus, minor (Wpl,z) | 1,200 cm³ | 1,109.4 cm³ | +8.2% |
| Radius of gyration, minor (iz) | 9.43 cm | 8.97 cm | +5.1% |
| Torsion constant (It) | 153 cm⁴ | 149.4 cm⁴ | +2.4% |
UC 356×368×129 to BS EN 10365:2017; HP 14X89 to AISC Shapes Database v16.0. Difference is expressed relative to HP 14X89.
How to choose between them
On stiffness, UC 356×368×129 has the larger second moment of area: 40,200 cm⁴ against 37,627 cm⁴, a difference of 6.8%. 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, UC 356×368×129 is the more efficient section: 19.2 against 18.1 cm³ per kg/m, 6.4% 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: UC 356×368×129 has 1200 cm³ of minor-axis plastic modulus against 1109.4 cm³, 8.2% 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. UC sections are specified to BS EN 10365:2017 and HP 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 2.6% weight.
In short, UC 356×368×129 is the stronger section and UC 356×368×129 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.