WT 10.5X66 vs ST 10X48
WT 10.5X66 is an WT section from the American AISC Shapes Database; ST 10X48 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 616.15 cm³ against 604.68 cm³ of plastic modulus, a difference of 1.9%. ST 10X48 is the lighter of the two at 71.4 kg/m against 98.2 kg/m, a saving of 37.5% on steel weight. WT 10.5X66 is deeper, 276.9 mm against 259.1 mm, which matters where the floor zone is tight.
| Property | WT 10.5X66 WT | ST 10X48 ST | Difference |
|---|---|---|---|
| Mass | 98.2 kg/m | 71.4 kg/m | +37.5% |
| Depth | 276.9 mm | 259.1 mm | +6.9% |
| Width | 315 mm | 182.9 mm | +72.2% |
| Web thickness | 16.5 mm | 20.3 mm | -18.7% |
| Flange thickness | 26.4 mm | 23.4 mm | +12.8% |
| Area | 125.2 cm² | 91 cm² | +37.6% |
| Second moment, major (Iy) | 7,534 cm⁴ | 5,952 cm⁴ | +26.6% |
| Plastic modulus, major (Wpl,y) | 616.15 cm³ | 604.68 cm³ | +1.9% |
| Elastic modulus, major (Wel,y) | 345.77 cm³ | 332.66 cm³ | +3.9% |
| Second moment, minor (Iz) | 6,909 cm⁴ | 1,041 cm⁴ | +563.7% |
| Plastic modulus, minor (Wpl,z) | 673.51 cm³ | 204.84 cm³ | +228.8% |
| Radius of gyration, minor (iz) | 7.44 cm | 3.38 cm | +120.1% |
| Torsion constant (It) | 233.9 cm⁴ | 173.2 cm⁴ | +35.0% |
WT 10.5X66 to AISC Shapes Database v16.0; ST 10X48 to AISC Shapes Database v16.0. Difference is expressed relative to ST 10X48.
How to choose between them
On stiffness, WT 10.5X66 has the larger second moment of area: 7,534 cm⁴ against 5,952 cm⁴, a difference of 26.6%. 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 10X48 is the more efficient section: 8.5 against 6.3 cm³ per kg/m, 25.9% 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 10.5X66 has 673.51 cm³ of minor-axis plastic modulus against 204.84 cm³, 228.8% 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 10.5X66 is the stronger section and ST 10X48 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.