W40×149 Steel Beam
A W40×149 is a wide flange steel beam 38.2 inches deep with 11.8-inch flanges, weighing 149 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 2,243 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 650 kips.
Design a W40×149 beam Opens a 57 ft span in the free beam designer.
W40×149 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 38.2 in |
| Flange width, bf | 11.8 in |
| Flange thickness, tf | 0.830 in |
| Web thickness, tw | 0.630 in |
| Distance to web toe of fillet, kdes | 2.01 in |
| Distance between flange centroids, ho | 37.37 in |
| Cross-sectional area, A | 43.8 in2 |
| Weight | 149 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W40×149 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 9800 in4 | 229 in4 |
| Elastic section modulus, S | 513 in3 | 38.8 in3 |
| Plastic section modulus, Z | 598 in3 | 62.2 in3 |
| Radius of gyration, r | 15.0 in | 2.29 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 9.36 in4 |
| Warping constant, Cw | 80000 in6 |
| Effective radius of gyration, rts | 2.89 in |
| Flange slenderness, bf/2tf | 7.11 |
| Web slenderness, h/tw | 54.3 |
W40×149 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 = 2,243 kip-ft | Mn/Ω = 1,492 kip-ft |
| Shear | φVn = 650 kips | Vn/Ω = 432 kips |
If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to Lp = 8.1 ft between braces it keeps its full strength; past Lr = 23.5 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 2,243 kip-ft | 1,492 kip-ft |
| 5 ft | 2,243 kip-ft | 1,492 kip-ft |
| 8.1 ft (Lp) | 2,242 kip-ft | 1,492 kip-ft |
| 10 ft | 2,132 kip-ft | 1,418 kip-ft |
| 15 ft | 1,842 kip-ft | 1,225 kip-ft |
| 20 ft | 1,552 kip-ft | 1,033 kip-ft |
| 23.5 ft (Lr) | 1,347 kip-ft | 896 kip-ft |
| 25 ft | 1,213 kip-ft | 807 kip-ft |
| 30 ft | 894 kip-ft | 595 kip-ft |
| 35 ft | 700 kip-ft | 466 kip-ft |
| 40 ft | 571 kip-ft | 380 kip-ft |
| 45 ft | 481 kip-ft | 320 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.
W40×149 load table by span
The largest uniform load a simply supported W40×149 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 0.149 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 19 ft | 49.7 | 33.1 | 61.4 | 92.1 |
| 21 ft | 40.7 | 27.1 | 45.5 | 68.2 |
| 23 ft | 33.9 | 22.6 | 34.6 | 51.9 |
| 25 ft | 28.7 | 19.1 | 26.9 | 40.4 |
| 27 ft | 24.6 | 16.4 | 21.4 | 32.1 |
| 29 ft | 21.3 | 14.2 | 17.3 | 25.9 |
| 31 ft | 18.7 | 12.4 | 14.1 | 21.2 |
| 33 ft | 16.5 | 11.0 | 11.7 | 17.6 |
| 35 ft | 14.6 | 9.74 | 9.82 | 14.7 |
| 37 ft | 13.1 | 8.72 | 8.31 | 12.5 |
| 39 ft | 11.8 | 7.85 | 7.10 | 10.6 |
| 41 ft | 10.7 | 7.10 | 6.11 | 9.16 |
| 43 ft | 9.70 | 6.46 | 5.30 | 7.94 |
| 45 ft | 8.86 | 5.89 | 4.62 | 6.93 |
| 47 ft | 8.12 | 5.40 | 4.06 | 6.08 |
| 49 ft | 7.47 | 4.97 | 3.58 | 5.37 |
| 51 ft | 6.90 | 4.59 | 3.17 | 4.76 |
| 53 ft | 6.39 | 4.25 | 2.83 | 4.24 |
| 55 ft | 5.93 | 3.95 | 2.53 | 3.80 |
| 57 ft | 5.52 | 3.67 | 2.27 | 3.41 |
| 59 ft | 5.15 | 3.43 | 2.05 | 3.08 |
| 61 ft | 4.82 | 3.21 | 1.85 | 2.78 |
| 63 ft | 4.52 | 3.01 | 1.68 | 2.53 |
| 65 ft | 4.25 | 2.83 | 1.53 | 2.30 |
| 67 ft | 4.00 | 2.66 | 1.40 | 2.10 |
| 69 ft | 3.77 | 2.51 | 1.28 | 1.92 |
| 71 ft | 3.56 | 2.37 | 1.18 | 1.76 |
| 73 ft | 3.37 | 2.24 | 1.08 | 1.62 |
| 75 ft | 3.19 | 2.12 | 1.00 | 1.50 |
| 77 ft | 3.03 | 2.01 | 0.92 | 1.38 |
| 79 ft | 2.87 | 1.91 | 0.85 | 1.28 |
| 81 ft | 2.73 | 1.82 | 0.79 | 1.19 |
| 83 ft | 2.60 | 1.73 | 0.74 | 1.10 |
| 85 ft | 2.48 | 1.65 | 0.69 | 1.03 |
| 87 ft | 2.37 | 1.58 | 0.64 | 0.96 |
| 89 ft | 2.26 | 1.51 | 0.60 | 0.90 |
| 91 ft | 2.17 | 1.44 | 0.56 | 0.84 |
| 93 ft | 2.07 | 1.38 | 0.52 | 0.79 |
| 95 ft | 1.99 | 1.32 | 0.49 | 0.74 |
- 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 57 ft span, a W40×149 carries a factored load of 5.52 kips per foot (LRFD) or an allowable load of 3.67 kips per foot (ASD). A live load of 2.27 kips per foot would deflect it span/360, which is 1.90 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.
W40×149 questions
What does W40×149 mean?
W means a wide flange shape. 40 is its nominal depth in inches (the actual depth is 38.2 in) and 149 is its weight in pounds per foot.
How much does a W40×149 weigh?
149 pounds per foot, so a 20 ft W40×149 weighs about 2,980 pounds.
How far can a W40×149 span?
It depends on the load. Braced along its length, it carries 49.7 kips per foot of factored load at 19 ft and 1.99 kips per foot at 95 ft; the load table has the spans in between. Floor beams are often 57 to 76 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W40×149 a compact section?
Yes. Its flanges (bf/2tf = 7.11) and web (h/tw = 54.3) are both compact for bending in 50 ksi steel.