W 18X46 vs H-450x200x8x12-66.2
W 18X46 is an W section from the American AISC Shapes Database; H-450x200x8x12-66.2 is the closest equivalent in the European (Continental) range. W 18X46 carries more bending: 1486.3 cm³ of plastic modulus against 1450 cm³, 2.5% more. H-450x200x8x12-66.2 is the lighter of the two at 66.2 kg/m against 68.5 kg/m, a saving of 3.5% on steel weight. W 18X46 is deeper, 459.7 mm against 446 mm, which matters where the floor zone is tight.
| Property | W 18X46 W | H-450x200x8x12-66.2 MB & MC | Difference |
|---|---|---|---|
| Mass | 68.5 kg/m | 66.2 kg/m | +3.5% |
| Depth | 459.7 mm | 446 mm | +3.1% |
| Width | 153.9 mm | 199 mm | -22.7% |
| Web thickness | 9.1 mm | 8 mm | +13.7% |
| Flange thickness | 15.4 mm | 12 mm | +28.3% |
| Area | 87.1 cm² | 84.3 cm² | +3.3% |
| Second moment, major (Iy) | 29,636 cm⁴ | 28,700 cm⁴ | +3.3% |
| Plastic modulus, major (Wpl,y) | 1,486.3 cm³ | 1,450 cm³ | +2.5% |
| Elastic modulus, major (Wel,y) | 1,291.3 cm³ | 1,287 cm³ | +0.3% |
| Second moment, minor (Iz) | 936.5 cm⁴ | 1,581 cm⁴ | -40.8% |
| Plastic modulus, minor (Wpl,z) | 191.73 cm³ | 247 cm³ | -22.4% |
| Radius of gyration, minor (iz) | 3.28 cm | 4.33 cm | -24.2% |
| Torsion constant (It) | 50.78 cm⁴ | 38.3 cm⁴ | +32.6% |
W 18X46 to AISC Shapes Database v16.0; H-450x200x8x12-66.2 to Continental Steel. Difference is expressed relative to H-450x200x8x12-66.2.
How to choose between them
On stiffness, W 18X46 has the larger second moment of area: 29,636 cm⁴ against 28,700 cm⁴, a difference of 3.3%. 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, the two are equally efficient (21.7 against 21.9 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: H-450x200x8x12-66.2 has 247 cm³ of minor-axis plastic modulus against 191.73 cm³, 22.4% 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 MB & MC to 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 3.5% weight.
In short, W 18X46 is the stronger section and H-450x200x8x12-66.2 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.