W 12X45 vs HE 300 AA
W 12X45 is an W section from the American AISC Shapes Database; HE 300 AA is the closest equivalent in the European (Continental) range. They are close to interchangeable in bending: 1052 cm³ against 1060 cm³ of plastic modulus, a difference of 0.8%. W 12X45 is the lighter of the two at 67 kg/m against 69.8 kg/m, a saving of 4.0% on steel weight. W 12X45 is deeper, 307.3 mm against 283 mm, which matters where the floor zone is tight.
| Property | W 12X45 W | HE 300 AA HE | Difference |
|---|---|---|---|
| Mass | 67 kg/m | 69.8 kg/m | -4.0% |
| Depth | 307.3 mm | 283 mm | +8.6% |
| Width | 204.5 mm | 300 mm | -31.8% |
| Web thickness | 8.5 mm | 7.5 mm | +13.3% |
| Flange thickness | 14.6 mm | 10.5 mm | +39.0% |
| Area | 84.5 cm² | 88.9 cm² | -4.9% |
| Second moment, major (Iy) | 14,485 cm⁴ | 13,800 cm⁴ | +5.0% |
| Plastic modulus, major (Wpl,y) | 1,052 cm³ | 1,060 cm³ | -0.8% |
| Elastic modulus, major (Wel,y) | 945.53 cm³ | 976 cm³ | -3.1% |
| Second moment, minor (Iz) | 2,081 cm⁴ | 4,730 cm⁴ | -56.0% |
| Plastic modulus, minor (Wpl,z) | 311.35 cm³ | 482 cm³ | -35.4% |
| Radius of gyration, minor (iz) | 4.95 cm | 7.3 cm | -32.2% |
| Torsion constant (It) | 52.45 cm⁴ | 47.8 cm⁴ | +9.7% |
W 12X45 to AISC Shapes Database v16.0; HE 300 AA to EN 10365 · Continental Steel. Difference is expressed relative to HE 300 AA.
How to choose between them
On stiffness, W 12X45 has the larger second moment of area: 14,485 cm⁴ against 13,800 cm⁴, a difference of 5.0%. 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 12X45 is the more efficient section: 15.7 against 15.2 cm³ per kg/m, 3.4% 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: HE 300 AA has 482 cm³ of minor-axis plastic modulus against 311.35 cm³, 35.4% 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 4.0% weight.
In short, HE 300 AA is the stronger section and W 12X45 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.