W 21X83 vs HE 550 AA
W 21X83 is an W section from the American AISC Shapes Database; HE 550 AA is the closest equivalent in the European (Continental) range. W 21X83 carries more bending: 3211.9 cm³ of plastic modulus against 3130 cm³, 2.6% more. HE 550 AA is the lighter of the two at 120 kg/m against 123.5 kg/m, a saving of 2.9% on steel weight. W 21X83 is deeper, 543.6 mm against 522 mm, which matters where the floor zone is tight.
| Property | W 21X83 W | HE 550 AA HE | Difference |
|---|---|---|---|
| Mass | 123.5 kg/m | 120 kg/m | +2.9% |
| Depth | 543.6 mm | 522 mm | +4.1% |
| Width | 212.3 mm | 300 mm | -29.2% |
| Web thickness | 13.1 mm | 11.5 mm | +13.9% |
| Flange thickness | 21.2 mm | 15 mm | +41.3% |
| Area | 157.4 cm² | 153 cm² | +2.9% |
| Second moment, major (Iy) | 76,170 cm⁴ | 72,900 cm⁴ | +4.5% |
| Plastic modulus, major (Wpl,y) | 3,211.9 cm³ | 3,130 cm³ | +2.6% |
| Elastic modulus, major (Wel,y) | 2,802.2 cm³ | 2,790 cm³ | +0.4% |
| Second moment, minor (Iz) | 3,388 cm⁴ | 6,770 cm⁴ | -50.0% |
| Plastic modulus, minor (Wpl,z) | 499.81 cm³ | 699 cm³ | -28.5% |
| Radius of gyration, minor (iz) | 4.65 cm | 6.65 cm | -30.1% |
| Torsion constant (It) | 180.6 cm⁴ | 127 cm⁴ | +42.2% |
W 21X83 to AISC Shapes Database v16.0; HE 550 AA to EN 10365 · Continental Steel. Difference is expressed relative to HE 550 AA.
How to choose between them
On stiffness, W 21X83 has the larger second moment of area: 76,170 cm⁴ against 72,900 cm⁴, a difference of 4.5%. 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 (26.0 against 26.1 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.
The two diverge much more about the minor axis: HE 550 AA has 699 cm³ of minor-axis plastic modulus against 499.81 cm³, 28.5% 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 2.9% weight.
In short, W 21X83 is the stronger section and HE 550 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.