W40×249 Steel Beam
A W40×249 is a wide flange steel beam 39.4 inches deep with 15.8-inch flanges, weighing 249 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 4,200 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 887 kips.
Design a W40×249 beam Opens a 60 ft span in the free beam designer.
W40×249 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 39.4 in |
| Flange width, bf | 15.8 in |
| Flange thickness, tf | 1.42 in |
| Web thickness, tw | 0.750 in |
| Distance to web toe of fillet, kdes | 2.60 in |
| Distance between flange centroids, ho | 37.98 in |
| Cross-sectional area, A | 73.3 in2 |
| Weight | 249 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W40×249 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 19600 in4 | 926 in4 |
| Elastic section modulus, S | 993 in3 | 118 in3 |
| Plastic section modulus, Z | 1120 in3 | 182 in3 |
| Radius of gyration, r | 16.3 in | 3.55 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 38.1 in4 |
| Warping constant, Cw | 334000 in6 |
| Effective radius of gyration, rts | 4.21 in |
| Flange slenderness, bf/2tf | 5.55 |
| Web slenderness, h/tw | 45.6 |
W40×249 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 = 4,200 kip-ft | Mn/Ω = 2,794 kip-ft |
| Shear | φVn = 887 kips | Vn/Ω = 591 kips |
If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to Lp = 12.5 ft between braces it keeps its full strength; past Lr = 37.2 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 4,200 kip-ft | 2,794 kip-ft |
| 10 ft | 4,200 kip-ft | 2,794 kip-ft |
| 12.5 ft (Lp) | 4,200 kip-ft | 2,794 kip-ft |
| 20 ft | 3,718 kip-ft | 2,473 kip-ft |
| 30 ft | 3,071 kip-ft | 2,043 kip-ft |
| 37.2 ft (Lr) | 2,603 kip-ft | 1,732 kip-ft |
| 40 ft | 2,332 kip-ft | 1,551 kip-ft |
| 50 ft | 1,691 kip-ft | 1,125 kip-ft |
| 60 ft | 1,324 kip-ft | 881 kip-ft |
| 70 ft | 1,089 kip-ft | 724 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.
W40×249 load table by span
The largest uniform load a simply supported W40×249 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 0.249 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 20 ft | 84.0 | 55.9 | 105.3 | 157.9 |
| 22 ft | 69.4 | 46.2 | 79.1 | 118.6 |
| 24 ft | 58.3 | 38.8 | 60.9 | 91.4 |
| 26 ft | 49.7 | 33.1 | 47.9 | 71.9 |
| 28 ft | 42.9 | 28.5 | 38.4 | 57.5 |
| 30 ft | 37.3 | 24.8 | 31.2 | 46.8 |
| 32 ft | 32.8 | 21.8 | 25.7 | 38.5 |
| 34 ft | 29.1 | 19.3 | 21.4 | 32.1 |
| 36 ft | 25.9 | 17.2 | 18.0 | 27.1 |
| 38 ft | 23.3 | 15.5 | 15.3 | 23.0 |
| 40 ft | 21.0 | 14.0 | 13.2 | 19.7 |
| 42 ft | 19.0 | 12.7 | 11.4 | 17.0 |
| 44 ft | 17.4 | 11.5 | 9.89 | 14.8 |
| 46 ft | 15.9 | 10.6 | 8.65 | 13.0 |
| 48 ft | 14.6 | 9.70 | 7.61 | 11.4 |
| 50 ft | 13.4 | 8.94 | 6.74 | 10.1 |
| 52 ft | 12.4 | 8.27 | 5.99 | 8.98 |
| 54 ft | 11.5 | 7.67 | 5.35 | 8.02 |
| 56 ft | 10.7 | 7.13 | 4.79 | 7.19 |
| 58 ft | 9.99 | 6.65 | 4.32 | 6.47 |
| 60 ft | 9.33 | 6.21 | 3.90 | 5.85 |
| 62 ft | 8.74 | 5.82 | 3.53 | 5.30 |
| 64 ft | 8.20 | 5.46 | 3.21 | 4.82 |
| 66 ft | 7.71 | 5.13 | 2.93 | 4.39 |
| 68 ft | 7.27 | 4.83 | 2.68 | 4.02 |
| 70 ft | 6.86 | 4.56 | 2.46 | 3.68 |
| 72 ft | 6.48 | 4.31 | 2.26 | 3.38 |
| 74 ft | 6.14 | 4.08 | 2.08 | 3.12 |
| 76 ft | 5.82 | 3.87 | 1.92 | 2.88 |
| 78 ft | 5.52 | 3.67 | 1.77 | 2.66 |
| 80 ft | 5.25 | 3.49 | 1.64 | 2.47 |
| 82 ft | 5.00 | 3.32 | 1.53 | 2.29 |
| 84 ft | 4.76 | 3.17 | 1.42 | 2.13 |
| 86 ft | 4.54 | 3.02 | 1.32 | 1.99 |
| 88 ft | 4.34 | 2.89 | 1.24 | 1.85 |
| 90 ft | 4.15 | 2.76 | 1.16 | 1.73 |
| 92 ft | 3.97 | 2.64 | 1.08 | 1.62 |
| 94 ft | 3.80 | 2.53 | 1.01 | 1.52 |
| 96 ft | 3.65 | 2.43 | 0.95 | 1.43 |
| 98 ft | 3.50 | 2.33 | 0.89 | 1.34 |
- 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 60 ft span, a W40×249 carries a factored load of 9.33 kips per foot (LRFD) or an allowable load of 6.21 kips per foot (ASD). A live load of 3.90 kips per foot would deflect it span/360, which is 2.00 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.
W40×249 questions
What does W40×249 mean?
W means a wide flange shape. 40 is its nominal depth in inches (the actual depth is 39.4 in) and 249 is its weight in pounds per foot.
How much does a W40×249 weigh?
249 pounds per foot, so a 20 ft W40×249 weighs about 4,980 pounds.
How far can a W40×249 span?
It depends on the load. Braced along its length, it carries 84.0 kips per foot of factored load at 20 ft and 3.50 kips per foot at 98 ft; the load table has the spans in between. Floor beams are often 59 to 79 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W40×249 a compact section?
Yes. Its flanges (bf/2tf = 5.55) and web (h/tw = 45.6) are both compact for bending in 50 ksi steel.