W 18X86 vs H-500x300x11x18-125
W 18X86 is an W section from the American AISC Shapes Database; H-500x300x11x18-125 is the closest equivalent in the European (Continental) range. H-500x300x11x18-125 carries more bending: 3132 cm³ of plastic modulus against 3048 cm³, 2.7% more. H-500x300x11x18-125 is the lighter of the two at 125 kg/m against 128 kg/m, a saving of 2.4% on steel weight. H-500x300x11x18-125 is deeper, 488 mm against 467.4 mm, which matters where the floor zone is tight.
| Property | W 18X86 W | H-500x300x11x18-125 MB & MC | Difference |
|---|---|---|---|
| Mass | 128 kg/m | 125 kg/m | +2.4% |
| Depth | 467.4 mm | 488 mm | -4.2% |
| Width | 281.9 mm | 300 mm | -6.0% |
| Web thickness | 12.2 mm | 11 mm | +10.9% |
| Flange thickness | 19.6 mm | 18 mm | +8.9% |
| Area | 163.2 cm² | 159 cm² | +2.6% |
| Second moment, major (Iy) | 63,683 cm⁴ | 68,860 cm⁴ | -7.5% |
| Plastic modulus, major (Wpl,y) | 3,048 cm³ | 3,132 cm³ | -2.7% |
| Elastic modulus, major (Wel,y) | 2,720.3 cm³ | 2,822 cm³ | -3.6% |
| Second moment, minor (Iz) | 7,284 cm⁴ | 8,106 cm⁴ | -10.1% |
| Plastic modulus, minor (Wpl,z) | 793.13 cm³ | 825 cm³ | -3.9% |
| Radius of gyration, minor (iz) | 6.68 cm | 7.14 cm | -6.4% |
| Torsion constant (It) | 170.7 cm⁴ | 143 cm⁴ | +19.4% |
W 18X86 to AISC Shapes Database v16.0; H-500x300x11x18-125 to Continental Steel. Difference is expressed relative to H-500x300x11x18-125.
How to choose between them
On stiffness, H-500x300x11x18-125 has the larger second moment of area: 68,860 cm⁴ against 63,683 cm⁴, a difference of 7.5%. 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 of steel, H-500x300x11x18-125 is the more efficient section: 25.1 against 23.8 cm³ per kg/m, 5.0% 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.
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 2.4% weight.
In short, H-500x300x11x18-125 is the stronger section and H-500x300x11x18-125 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.