W 21X93 vs HE 600 AA
W 21X93 is an W section from the American AISC Shapes Database; HE 600 AA is the closest equivalent in the European (Continental) range. They are close to interchangeable in bending: 3621.5 cm³ against 3620 cm³ of plastic modulus, a difference of 0.0%. HE 600 AA is the lighter of the two at 129 kg/m against 138.4 kg/m, a saving of 7.3% on steel weight. HE 600 AA is deeper, 571 mm against 548.6 mm, which matters where the floor zone is tight.
| Property | W 21X93 W | HE 600 AA HE | Difference |
|---|---|---|---|
| Mass | 138.4 kg/m | 129 kg/m | +7.3% |
| Depth | 548.6 mm | 571 mm | -3.9% |
| Width | 213.9 mm | 300 mm | -28.7% |
| Web thickness | 14.7 mm | 12 mm | +22.5% |
| Flange thickness | 23.6 mm | 15.5 mm | +52.3% |
| Area | 176.1 cm² | 164 cm² | +7.4% |
| Second moment, major (Iy) | 86,160 cm⁴ | 91,900 cm⁴ | -6.2% |
| Plastic modulus, major (Wpl,y) | 3,621.5 cm³ | 3,620 cm³ | same |
| Elastic modulus, major (Wel,y) | 3,146.3 cm³ | 3,220 cm³ | -2.3% |
| Second moment, minor (Iz) | 3,867 cm⁴ | 6,990 cm⁴ | -44.7% |
| Plastic modulus, minor (Wpl,z) | 568.63 cm³ | 724 cm³ | -21.5% |
| Radius of gyration, minor (iz) | 4.67 cm | 6.53 cm | -28.5% |
| Torsion constant (It) | 251 cm⁴ | 142 cm⁴ | +76.8% |
W 21X93 to AISC Shapes Database v16.0; HE 600 AA to EN 10365 · Continental Steel. Difference is expressed relative to HE 600 AA.
How to choose between them
On stiffness, HE 600 AA has the larger second moment of area: 91,900 cm⁴ against 86,160 cm⁴, a difference of 6.2%. 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 of steel, HE 600 AA is the more efficient section: 28.1 against 26.2 cm³ per kg/m, 6.8% 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 600 AA has 724 cm³ of minor-axis plastic modulus against 568.63 cm³, 21.5% 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. 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 7.3% weight.
In short, W 21X93 is the stronger section and HE 600 AA 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.