The W24 family: what 117, 131 and 146 mean
W24x117, W24x131 and W24x146 are three American standard wide flange beams that share a nominal depth of about 24 in and differ in mass per unit length: 117, 131 and 146 lb/ft, which correspond to about 174.1, 194.9 and 217.2 kg per metre. Because the depth band is the same, the three shapes are interchangeable in a framing line and can be chosen purely on the strength and stiffness the design demands, which makes them a convenient family for progressive sizing on a single project.
The weight figure is the clearest indicator of capacity in the group. Each step up adds flange and web thickness without changing the nominal depth, so the section modulus, moment of inertia and shear area all increase in sequence, and the cost of the beam rises with the mass rather than with the depth.
Comparison of W24x117, W24x131 and W24x146
| Parameter | W24x117 | W24x131 | W24x146 |
|---|---|---|---|
| Nominal depth d | 24.26 in / 616.2 mm | 24.48 in / 621.8 mm | 24.74 in / 628.4 mm |
| Flange width bf | 12.80 in / 325.1 mm | 12.99 in / 329.9 mm | 12.90 in / 327.7 mm |
| Flange thickness tf | 0.850 in / 21.6 mm | 0.960 in / 24.4 mm | 1.090 in / 27.7 mm |
| Web thickness tw | 0.550 in / 14.0 mm | 0.605 in / 15.4 mm | 0.650 in / 16.5 mm |
| Section area A | 34.4 in2 / 221.9 cm2 | 38.5 in2 / 248.4 cm2 | 42.9 in2 / 276.8 cm2 |
| Moment of inertia Ix | 3,540 in4 / 147,300 cm4 | 4,020 in4 / 167,300 cm4 | 4,580 in4 / 190,600 cm4 |
| Section modulus Sx | 291 in3 / 4,770 cm3 | 329 in3 / 5,390 cm3 | 371 in3 / 6,080 cm3 |
| Mass per length | 117 lb/ft / 174.1 kg/m | 131 lb/ft / 194.9 kg/m | 146 lb/ft / 217.2 kg/m |
| Nominal yield moment at 345 MPa | about 1,646 kN.m | about 1,859 kN.m | about 2,098 kN.m |
The yield moments shown are simple products of the elastic section modulus and the 345 MPa specified minimum yield stress. They are order of magnitude figures for comparing the three shapes, not design resistances, because the resistance factor, lateral torsional buckling along the unbraced length, shear at the supports and deflection limits will all reduce the usable value.
Material options for the three sections
ASTM A992 is the usual specification for building frames. It guarantees a minimum yield of 345 MPa, caps the yield at 450 MPa, requires a tensile to yield ratio of at least 1.05 and limits carbon equivalent to 0.45%, which supports both weldability and dependable ductility. ASTM A572 Grade 50 reaches the same 345 MPa minimum yield and is widely rolled for beams and girders, and it is an acceptable alternative where the design does not rely on the tighter A992 controls. Hot rolled carbon steel such as ASTM A36 is still used for lightly loaded and secondary members, but its lower yield strength means the heavier W24 shapes are rarely the economical choice in that grade.
How to choose between W24x117, W24x131 and W24x146
Size for the governing action first. If bending governs, the section modulus drives the choice; if deflection or vibration governs, the moment of inertia does; if the span is short and the load is concentrated, web shear and stiffener requirements decide.
Keep the nominal depth constant. Because all three shapes sit in the same depth band, the ceiling void, cladding line and connection geometry stay unchanged when a beam is upsized during detailed design.
Check local effects before stepping up. Web local buckling, concentrated load stiffeners, block shear at the connection and the number of bolts required often make a heavier beam cheaper overall than adding reinforcement to a lighter one.
Confirm the bracing arrangement. Lateral torsional buckling depends on the unbraced length and the shape of the moment diagram, so the position of secondary beams and braces can matter more than the difference between two adjacent rolled sizes.
Fabrication and erection practice
Cutting and drilling: the sections are cut to length by band saw or thermal process and drilled for end plates, shear tabs and stiffeners under shop control, which keeps the site work to bolting and final connection.
Welding: E70XX electrodes and matching gas shielded wires suit both A992 and A572 Grade 50. Carbon equivalent limits keep preheat moderate, and all procedures are qualified before production.
Stiffeners and reinforcement: bearing stiffeners at supports, intermediate stiffeners at heavy point loads and doubler plates at moment connections are added in the shop to avoid overhead welding on site.
Lifting and stability: the three sections weigh between about 174 and 217 kg per metre, so lifting plans use spreader beams and slings bearing on the web, and temporary bracing is placed before the frame is released.
Coating: shop primer with site topcoat is normal, while galvanizing or a heavy duty system is chosen for external, humid or marine exposure, with vent and drain holes detailed into the connections.
Where these beams are used
High rise and long span building frames acting as primary beams, transfer members and columns.
Bridge girders, floor beams and pier caps on road and rail crossings.
Heavy industrial plant structures, equipment support frames, crane girders and runway beams.
Warehouse, logistics and mezzanine framing where long spans and heavy floor loads occur.
Pipe racks, towers, port handling structures and other open steelwork exposed to wind and dynamic load.
FAQ about W24x117, W24x131 and W24x146 beams
Q: Which of the three beams is strongest?
W24x146 is the heaviest and strongest of the group, with an elastic section modulus of about 6,080 cm3 against 5,390 cm3 for W24x131 and 4,770 cm3 for W24x117. Its greater flange and web thickness give both higher bending capacity and better local stability.
Q: Can the three sections be used in the same framing line?
Yes. They share the same nominal depth band, so the beam soffit and the connection geometry remain compatible. Sizing each span on its own demand is normal practice, as long as the connection design recognises the different flange and web thicknesses.
Q: What steel grades are supplied for these shapes?
ASTM A992 is standard for building frames and ASTM A572 Grade 50 is a common alternative for beams and girders; both give a 345 MPa minimum yield. The grade actually supplied must match the design assumptions and appear on the mill certificate.
Q: How is the section modulus used in a quick check?
Multiplying the elastic section modulus by the specified yield stress gives an approximate yield moment, for example about 1,646 kN.m for W24x117 at 345 MPa. The design moment is lower after applying the resistance factor and checking lateral torsional buckling, shear and deflection.
Q: Are these beams available cut to length and pre-drilled?
Yes. Shop cutting, drilling, stiffener welding and coating are normal scope for a fabricator, and delivering members ready to bolt reduces site time and protects the coating during handling and storage.