WT 9X59.5 vs ST 10X37.5
WT 9X59.5 is an WT section from the American AISC Shapes Database; ST 10X37.5 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 470.31 cm³ against 468.67 cm³ of plastic modulus, a difference of 0.3%. ST 10X37.5 is the lighter of the two at 55.8 kg/m against 88.5 kg/m, a saving of 58.6% on steel weight. ST 10X37.5 is deeper, 254 mm against 241 mm, which matters where the floor zone is tight.
| Property | WT 9X59.5 WT | ST 10X37.5 ST | Difference |
|---|---|---|---|
| Mass | 88.5 kg/m | 55.8 kg/m | +58.6% |
| Depth | 241 mm | 254 mm | -5.1% |
| Width | 287 mm | 162.3 mm | +76.8% |
| Web thickness | 16.6 mm | 16.1 mm | +3.1% |
| Flange thickness | 26.9 mm | 20.2 mm | +33.2% |
| Area | 113.5 cm² | 71 cm² | +59.9% |
| Second moment, major (Iy) | 4,953 cm⁴ | 4,537 cm⁴ | +9.2% |
| Plastic modulus, major (Wpl,y) | 470.31 cm³ | 468.67 cm³ | +0.3% |
| Elastic modulus, major (Wel,y) | 260.55 cm³ | 258.92 cm³ | +0.6% |
| Second moment, minor (Iz) | 5,245 cm⁴ | 616 cm⁴ | +751.5% |
| Plastic modulus, minor (Wpl,z) | 565.35 cm³ | 137 cm³ | +312.7% |
| Radius of gyration, minor (iz) | 6.83 cm | 2.95 cm | +131.5% |
| Torsion constant (It) | 220.6 cm⁴ | 94.9 cm⁴ | +132.5% |
WT 9X59.5 to AISC Shapes Database v16.0; ST 10X37.5 to AISC Shapes Database v16.0. Difference is expressed relative to ST 10X37.5.
How to choose between them
On stiffness, WT 9X59.5 has the larger second moment of area: 4,953 cm⁴ against 4,537 cm⁴, a difference of 9.2%. 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, ST 10X37.5 is the more efficient section: 8.4 against 5.3 cm³ per kg/m, 36.7% 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: WT 9X59.5 has 565.35 cm³ of minor-axis plastic modulus against 137 cm³, 312.7% 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.
In short, WT 9X59.5 is the stronger section and ST 10X37.5 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.