W 18X65 vs HE 450 AA
W 18X65 is an W section from the American AISC Shapes Database; HE 450 AA is the closest equivalent in the European (Continental) range. They are close to interchangeable in bending: 2179.5 cm³ against 2180 cm³ of plastic modulus, a difference of 0.0%. W 18X65 is the lighter of the two at 96.7 kg/m against 99.7 kg/m, a saving of 3.0% on steel weight. W 18X65 is deeper, 467.4 mm against 425 mm, which matters where the floor zone is tight.
| Property | W 18X65 W | HE 450 AA HE | Difference |
|---|---|---|---|
| Mass | 96.7 kg/m | 99.7 kg/m | -3.0% |
| Depth | 467.4 mm | 425 mm | +10.0% |
| Width | 192.8 mm | 300 mm | -35.7% |
| Web thickness | 11.4 mm | 10 mm | +14.0% |
| Flange thickness | 19 mm | 13.5 mm | +40.7% |
| Area | 123.2 cm² | 127 cm² | -3.0% |
| Second moment, major (Iy) | 44,537 cm⁴ | 41,900 cm⁴ | +6.3% |
| Plastic modulus, major (Wpl,y) | 2,179.5 cm³ | 2,180 cm³ | same |
| Elastic modulus, major (Wel,y) | 1,917.3 cm³ | 1,970 cm³ | -2.7% |
| Second moment, minor (Iz) | 2,281 cm⁴ | 6,090 cm⁴ | -62.5% |
| Plastic modulus, minor (Wpl,z) | 368.71 cm³ | 624 cm³ | -40.9% |
| Radius of gyration, minor (iz) | 4.29 cm | 6.92 cm | -38.0% |
| Torsion constant (It) | 113.6 cm⁴ | 91.4 cm⁴ | +24.3% |
W 18X65 to AISC Shapes Database v16.0; HE 450 AA to EN 10365 · Continental Steel. Difference is expressed relative to HE 450 AA.
How to choose between them
On stiffness, W 18X65 has the larger second moment of area: 44,537 cm⁴ against 41,900 cm⁴, a difference of 6.3%. 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 18X65 is the more efficient section: 22.5 against 21.9 cm³ per kg/m, 3.1% 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: HE 450 AA has 624 cm³ of minor-axis plastic modulus against 368.71 cm³, 40.9% 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. W sections are specified to AISC Shapes Database v16.0 and HE to EN 10365 · Continental Steel; 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 3.0% weight.
In short, HE 450 AA 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.