WT 7X54.5 vs ST 7.5X25
WT 7X54.5 is an WT section from the American AISC Shapes Database; ST 7.5X25 is the closest equivalent in the American AISC Shapes Database. WT 7X54.5 carries more bending: 235.97 cm³ of plastic modulus against 229.42 cm³, 2.9% more. ST 7.5X25 is the lighter of the two at 37.2 kg/m against 81.1 kg/m, a saving of 118.0% on steel weight. ST 7.5X25 is deeper, 190.5 mm against 181.9 mm, which matters where the floor zone is tight.
| Property | WT 7X54.5 WT | ST 7.5X25 ST | Difference |
|---|---|---|---|
| Mass | 81.1 kg/m | 37.2 kg/m | +118.0% |
| Depth | 181.9 mm | 190.5 mm | -4.5% |
| Width | 370.8 mm | 143.3 mm | +158.8% |
| Web thickness | 13.3 mm | 14 mm | -5.0% |
| Flange thickness | 21.8 mm | 15.8 mm | +38.0% |
| Area | 103.2 cm² | 47.4 cm² | +117.7% |
| Second moment, major (Iy) | 1,886 cm⁴ | 1,686 cm⁴ | +11.9% |
| Plastic modulus, major (Wpl,y) | 235.97 cm³ | 229.42 cm³ | +2.9% |
| Elastic modulus, major (Wel,y) | 123.89 cm³ | 126.51 cm³ | -2.1% |
| Second moment, minor (Iz) | 9,282 cm⁴ | 324.2 cm⁴ | +2763.0% |
| Plastic modulus, minor (Wpl,z) | 758.72 cm³ | 81.771 cm³ | +827.9% |
| Radius of gyration, minor (iz) | 9.47 cm | 2.62 cm | +261.5% |
| Torsion constant (It) | 147.8 cm⁴ | 43.7 cm⁴ | +238.2% |
WT 7X54.5 to AISC Shapes Database v16.0; ST 7.5X25 to AISC Shapes Database v16.0. Difference is expressed relative to ST 7.5X25.
How to choose between them
On stiffness, WT 7X54.5 has the larger second moment of area: 1,886 cm⁴ against 1,686 cm⁴, a difference of 11.9%. 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 7.5X25 is the more efficient section: 6.2 against 2.9 cm³ per kg/m, 52.8% 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 7X54.5 has 758.72 cm³ of minor-axis plastic modulus against 81.771 cm³, 827.9% 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 7X54.5 is the stronger section and ST 7.5X25 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.