UB 457×191×98 vs W 18X65
UB 457×191×98 is an UB section from the UK Blue Book (SCI P363); W 18X65 is the closest equivalent in the American AISC Shapes Database. UB 457×191×98 carries more bending: 2230 cm³ of plastic modulus against 2179.5 cm³, 2.3% more. They weigh essentially the same, 98.3 kg/m and 96.7 kg/m. Both are about 467 mm deep, so either fits the same construction zone.
| Property | UB 457×191×98 UB | W 18X65 W | Difference |
|---|---|---|---|
| Mass | 98.3 kg/m | 96.7 kg/m | +1.7% |
| Depth | 467.2 mm | 467.4 mm | same |
| Width | 192.8 mm | 192.8 mm | same |
| Web thickness | 11.4 mm | 11.4 mm | same |
| Flange thickness | 19.6 mm | 19 mm | +3.2% |
| Area | 125 cm² | 123.2 cm² | +1.5% |
| Second moment, major (Iy) | 45,700 cm⁴ | 44,537 cm⁴ | +2.6% |
| Plastic modulus, major (Wpl,y) | 2,230 cm³ | 2,179.5 cm³ | +2.3% |
| Elastic modulus, major (Wel,y) | 1,960 cm³ | 1,917.3 cm³ | +2.2% |
| Second moment, minor (Iz) | 2,350 cm⁴ | 2,281 cm⁴ | +3.0% |
| Plastic modulus, minor (Wpl,z) | 379 cm³ | 368.71 cm³ | +2.8% |
| Radius of gyration, minor (iz) | 4.33 cm | 4.29 cm | +0.9% |
| Torsion constant (It) | 121 cm⁴ | 113.6 cm⁴ | +6.5% |
UB 457×191×98 to BS EN 10365:2017; W 18X65 to AISC Shapes Database v16.0. Difference is expressed relative to W 18X65.
How to choose between them
On stiffness, UB 457×191×98 has the larger second moment of area: 45,700 cm⁴ against 44,537 cm⁴, a difference of 2.6%. 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 (22.7 against 22.5 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. UB 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 a marginal amount of weight.
In short, UB 457×191×98 is the stronger section and W 18X65 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.