W40×297 Steel Beam
A W40×297 is a wide flange steel beam 39.8 inches deep with 15.8-inch flanges, weighing 297 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 4,988 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 1,110 kips.
Design a W40×297 beam Opens a 60 ft span in the free beam designer.
W40×297 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 39.8 in |
| Flange width, bf | 15.8 in |
| Flange thickness, tf | 1.65 in |
| Web thickness, tw | 0.930 in |
| Distance to web toe of fillet, kdes | 2.83 in |
| Distance between flange centroids, ho | 38.15 in |
| Cross-sectional area, A | 87.4 in2 |
| Weight | 297 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W40×297 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 23200 in4 | 1090 in4 |
| Elastic section modulus, S | 1170 in3 | 138 in3 |
| Plastic section modulus, Z | 1330 in3 | 215 in3 |
| Radius of gyration, r | 16.3 in | 3.54 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 61.2 in4 |
| Warping constant, Cw | 399000 in6 |
| Effective radius of gyration, rts | 4.22 in |
| Flange slenderness, bf/2tf | 4.80 |
| Web slenderness, h/tw | 36.8 |
W40×297 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 = 4,988 kip-ft | Mn/Ω = 3,318 kip-ft |
| Shear | φVn = 1,110 kips | Vn/Ω = 740 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 = 39.4 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 4,988 kip-ft | 3,318 kip-ft |
| 10 ft | 4,988 kip-ft | 3,318 kip-ft |
| 12.5 ft (Lp) | 4,988 kip-ft | 3,318 kip-ft |
| 20 ft | 4,453 kip-ft | 2,963 kip-ft |
| 30 ft | 3,739 kip-ft | 2,488 kip-ft |
| 39.4 ft (Lr) | 3,072 kip-ft | 2,044 kip-ft |
| 40 ft | 2,999 kip-ft | 1,995 kip-ft |
| 50 ft | 2,211 kip-ft | 1,471 kip-ft |
| 60 ft | 1,751 kip-ft | 1,165 kip-ft |
| 70 ft | 1,451 kip-ft | 966 kip-ft |
| 80 ft | 1,241 kip-ft | 826 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.
W40×297 load table by span
The largest uniform load a simply supported W40×297 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 0.297 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 20 ft | 99.8 | 66.4 | 124.6 | 186.9 |
| 22 ft | 82.4 | 54.8 | 93.6 | 140.4 |
| 24 ft | 69.3 | 46.1 | 72.1 | 108.2 |
| 26 ft | 59.0 | 39.3 | 56.7 | 85.1 |
| 28 ft | 50.9 | 33.9 | 45.4 | 68.1 |
| 30 ft | 44.3 | 29.5 | 36.9 | 55.4 |
| 32 ft | 39.0 | 25.9 | 30.4 | 45.6 |
| 34 ft | 34.5 | 23.0 | 25.4 | 38.0 |
| 36 ft | 30.8 | 20.5 | 21.4 | 32.0 |
| 38 ft | 27.6 | 18.4 | 18.2 | 27.2 |
| 40 ft | 24.9 | 16.6 | 15.6 | 23.4 |
| 42 ft | 22.6 | 15.0 | 13.5 | 20.2 |
| 44 ft | 20.6 | 13.7 | 11.7 | 17.6 |
| 46 ft | 18.9 | 12.5 | 10.2 | 15.4 |
| 48 ft | 17.3 | 11.5 | 9.01 | 13.5 |
| 50 ft | 16.0 | 10.6 | 7.97 | 12.0 |
| 52 ft | 14.8 | 9.82 | 7.09 | 10.6 |
| 54 ft | 13.7 | 9.10 | 6.33 | 9.49 |
| 56 ft | 12.7 | 8.47 | 5.68 | 8.51 |
| 58 ft | 11.9 | 7.89 | 5.11 | 7.66 |
| 60 ft | 11.1 | 7.37 | 4.61 | 6.92 |
| 62 ft | 10.4 | 6.91 | 4.18 | 6.27 |
| 64 ft | 9.74 | 6.48 | 3.80 | 5.70 |
| 66 ft | 9.16 | 6.09 | 3.47 | 5.20 |
| 68 ft | 8.63 | 5.74 | 3.17 | 4.75 |
| 70 ft | 8.14 | 5.42 | 2.91 | 4.36 |
| 72 ft | 7.70 | 5.12 | 2.67 | 4.01 |
| 74 ft | 7.29 | 4.85 | 2.46 | 3.69 |
| 76 ft | 6.91 | 4.60 | 2.27 | 3.41 |
| 78 ft | 6.56 | 4.36 | 2.10 | 3.15 |
| 80 ft | 6.23 | 4.15 | 1.95 | 2.92 |
| 82 ft | 5.93 | 3.95 | 1.81 | 2.71 |
| 84 ft | 5.65 | 3.76 | 1.68 | 2.52 |
| 86 ft | 5.39 | 3.59 | 1.57 | 2.35 |
| 88 ft | 5.15 | 3.43 | 1.46 | 2.19 |
| 90 ft | 4.93 | 3.28 | 1.37 | 2.05 |
| 92 ft | 4.71 | 3.14 | 1.28 | 1.92 |
| 94 ft | 4.52 | 3.00 | 1.20 | 1.80 |
| 96 ft | 4.33 | 2.88 | 1.13 | 1.69 |
| 98 ft | 4.15 | 2.76 | 1.06 | 1.59 |
| 100 ft | 3.99 | 2.65 | 1.00 | 1.50 |
- 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 W40×297 carries a factored load of 11.1 kips per foot (LRFD) or an allowable load of 7.37 kips per foot (ASD). A live load of 4.61 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.
W40×297 questions
What does W40×297 mean?
W means a wide flange shape. 40 is its nominal depth in inches (the actual depth is 39.8 in) and 297 is its weight in pounds per foot.
How much does a W40×297 weigh?
297 pounds per foot, so a 20 ft W40×297 weighs about 5,940 pounds.
How far can a W40×297 span?
It depends on the load. Braced along its length, it carries 99.8 kips per foot of factored load at 20 ft and 3.99 kips per foot at 100 ft; the load table has the spans in between. Floor beams are often 60 to 80 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W40×297 a compact section?
Yes. Its flanges (bf/2tf = 4.80) and web (h/tw = 36.8) are both compact for bending in 50 ksi steel.