W30×124 Steel Beam
A W30×124 is a wide flange steel beam 30.2 inches deep with 10.5-inch flanges, weighing 124 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 1,530 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 530 kips.
Design a W30×124 beam Opens a 45 ft span in the free beam designer.
W30×124 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 30.2 in |
| Flange width, bf | 10.5 in |
| Flange thickness, tf | 0.930 in |
| Web thickness, tw | 0.585 in |
| Distance to web toe of fillet, kdes | 1.58 in |
| Distance between flange centroids, ho | 29.27 in |
| Cross-sectional area, A | 36.5 in2 |
| Weight | 124 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W30×124 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 5360 in4 | 181 in4 |
| Elastic section modulus, S | 355 in3 | 34.4 in3 |
| Plastic section modulus, Z | 408 in3 | 54.0 in3 |
| Radius of gyration, r | 12.1 in | 2.23 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 7.99 in4 |
| Warping constant, Cw | 38600 in6 |
| Effective radius of gyration, rts | 2.73 in |
| Flange slenderness, bf/2tf | 5.65 |
| Web slenderness, h/tw | 46.2 |
W30×124 bending and shear strength
For ASTM A992 steel (Fy = 50 ksi, E = 29,000 ksi) per AISC 360-16. Its flanges and web are compact for bending, so with its compression flange braced it reaches its full plastic moment.
| Strength | LRFD | ASD |
|---|---|---|
| Bending, compression flange braced | φMn = 1,530 kip-ft | Mn/Ω = 1,018 kip-ft |
| Shear | φVn = 530 kips | Vn/Ω = 353 kips |
If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to Lp = 7.9 ft between braces it keeps its full strength; past Lr = 23.2 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 1,530 kip-ft | 1,018 kip-ft |
| 5 ft | 1,530 kip-ft | 1,018 kip-ft |
| 7.9 ft (Lp) | 1,530 kip-ft | 1,018 kip-ft |
| 10 ft | 1,447 kip-ft | 963 kip-ft |
| 15 ft | 1,253 kip-ft | 833 kip-ft |
| 20 ft | 1,058 kip-ft | 704 kip-ft |
| 23.2 ft (Lr) | 930 kip-ft | 619 kip-ft |
| 25 ft | 828 kip-ft | 551 kip-ft |
| 30 ft | 626 kip-ft | 416 kip-ft |
| 35 ft | 500 kip-ft | 333 kip-ft |
| 40 ft | 416 kip-ft | 277 kip-ft |
| 45 ft | 356 kip-ft | 237 kip-ft |
A beam with a uniform load between braces has Cb above 1.0 (1.14 for a simple span braced only at its ends), so these values are conservative. The beam designer works out Cb for every segment between braces.
W30×124 load table by span
The largest uniform load a simply supported W30×124 can carry, in kips per foot, with its compression flange braced along its length (by a floor or roof deck, for example). The loads include the beam's own weight of 0.124 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 15 ft | 54.4 | 36.2 | 68.2 | 102.3 |
| 17 ft | 42.4 | 28.2 | 46.9 | 70.3 |
| 19 ft | 33.9 | 22.6 | 33.6 | 50.4 |
| 21 ft | 27.8 | 18.5 | 24.9 | 37.3 |
| 23 ft | 23.1 | 15.4 | 18.9 | 28.4 |
| 25 ft | 19.6 | 13.0 | 14.7 | 22.1 |
| 27 ft | 16.8 | 11.2 | 11.7 | 17.5 |
| 29 ft | 14.6 | 9.68 | 9.44 | 14.2 |
| 31 ft | 12.7 | 8.47 | 7.73 | 11.6 |
| 33 ft | 11.2 | 7.48 | 6.41 | 9.61 |
| 35 ft | 9.99 | 6.65 | 5.37 | 8.06 |
| 37 ft | 8.94 | 5.95 | 4.55 | 6.82 |
| 39 ft | 8.05 | 5.35 | 3.88 | 5.82 |
| 41 ft | 7.28 | 4.84 | 3.34 | 5.01 |
| 43 ft | 6.62 | 4.40 | 2.90 | 4.34 |
| 45 ft | 6.04 | 4.02 | 2.53 | 3.79 |
| 47 ft | 5.54 | 3.69 | 2.22 | 3.33 |
| 49 ft | 5.10 | 3.39 | 1.96 | 2.94 |
| 51 ft | 4.71 | 3.13 | 1.74 | 2.60 |
| 53 ft | 4.36 | 2.90 | 1.55 | 2.32 |
| 55 ft | 4.05 | 2.69 | 1.38 | 2.08 |
| 57 ft | 3.77 | 2.51 | 1.24 | 1.87 |
| 59 ft | 3.52 | 2.34 | 1.12 | 1.68 |
| 61 ft | 3.29 | 2.19 | 1.01 | 1.52 |
| 63 ft | 3.08 | 2.05 | 0.92 | 1.38 |
| 65 ft | 2.90 | 1.93 | 0.84 | 1.26 |
| 67 ft | 2.73 | 1.81 | 0.77 | 1.15 |
| 69 ft | 2.57 | 1.71 | 0.70 | 1.05 |
| 71 ft | 2.43 | 1.62 | 0.64 | 0.97 |
| 73 ft | 2.30 | 1.53 | 0.59 | 0.89 |
| 75 ft | 2.18 | 1.45 | 0.55 | 0.82 |
- Factored and allowable loads are limited by bending, or by shear where marked *.
- The deflection columns are the service loads that make the beam sag span/360 or span/240. Compare span/360 with the live load alone and span/240 with dead plus live load, the usual floor limits in IBC Table 1604.3.
Reading the table
At a 45 ft span, a W30×124 carries a factored load of 6.04 kips per foot (LRFD) or an allowable load of 4.02 kips per foot (ASD). A live load of 2.53 kips per foot would deflect it span/360, which is 1.50 in. The beam works if the factored load is under the first number and the live and total loads are under the deflection numbers. For other spans, supports or loads, open it in the beam designer, or follow the steel beam design guide to check one by hand.
W30×124 questions
What does W30×124 mean?
W means a wide flange shape. 30 is its nominal depth in inches (the actual depth is 30.2 in) and 124 is its weight in pounds per foot.
How much does a W30×124 weigh?
124 pounds per foot, so a 20 ft W30×124 weighs about 2,480 pounds.
How far can a W30×124 span?
It depends on the load. Braced along its length, it carries 54.4 kips per foot of factored load at 15 ft and 2.18 kips per foot at 75 ft; the load table has the spans in between. Floor beams are often 45 to 60 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W30×124 a compact section?
Yes. Its flanges (bf/2tf = 5.65) and web (h/tw = 46.2) are both compact for bending in 50 ksi steel.