W27×281 Steel Beam
A W27×281 is a wide flange steel beam 29.3 inches deep with 14.4-inch flanges, weighing 281 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 3,510 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 932 kips.
Design a W27×281 beam Opens a 45 ft span in the free beam designer.
W27×281 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 29.3 in |
| Flange width, bf | 14.4 in |
| Flange thickness, tf | 1.93 in |
| Web thickness, tw | 1.06 in |
| Distance to web toe of fillet, kdes | 2.72 in |
| Distance between flange centroids, ho | 27.37 in |
| Cross-sectional area, A | 82.9 in2 |
| Weight | 281 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W27×281 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 11900 in4 | 953 in4 |
| Elastic section modulus, S | 814 in3 | 133 in3 |
| Plastic section modulus, Z | 936 in3 | 206 in3 |
| Radius of gyration, r | 12.0 in | 3.39 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 79.5 in4 |
| Warping constant, Cw | 178000 in6 |
| Effective radius of gyration, rts | 4.00 in |
| Flange slenderness, bf/2tf | 3.72 |
| Web slenderness, h/tw | 22.5 |
W27×281 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 = 3,510 kip-ft | Mn/Ω = 2,335 kip-ft |
| Shear | φVn = 932 kips | Vn/Ω = 621 kips |
If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to Lp = 12.0 ft between braces it keeps its full strength; past Lr = 49.1 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 3,510 kip-ft | 2,335 kip-ft |
| 10 ft | 3,510 kip-ft | 2,335 kip-ft |
| 12.0 ft (Lp) | 3,510 kip-ft | 2,335 kip-ft |
| 20 ft | 3,213 kip-ft | 2,138 kip-ft |
| 30 ft | 2,844 kip-ft | 1,892 kip-ft |
| 40 ft | 2,474 kip-ft | 1,646 kip-ft |
| 49.1 ft (Lr) | 2,135 kip-ft | 1,421 kip-ft |
| 50 ft | 2,093 kip-ft | 1,392 kip-ft |
| 60 ft | 1,707 kip-ft | 1,136 kip-ft |
| 70 ft | 1,444 kip-ft | 961 kip-ft |
| 80 ft | 1,252 kip-ft | 833 kip-ft |
| 90 ft | 1,106 kip-ft | 736 kip-ft |
| 100 ft | 991 kip-ft | 659 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.
W27×281 load table by span
The largest uniform load a simply supported W27×281 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 0.281 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 15 ft | 124.2* | 82.8* | 151.5 | 227.2 |
| 17 ft | 97.2 | 64.6 | 104.1 | 156.1 |
| 19 ft | 77.8 | 51.8 | 74.5 | 111.8 |
| 21 ft | 63.7 | 42.4 | 55.2 | 82.8 |
| 23 ft | 53.1 | 35.3 | 42.0 | 63.0 |
| 25 ft | 44.9 | 29.9 | 32.7 | 49.1 |
| 27 ft | 38.5 | 25.6 | 26.0 | 39.0 |
| 29 ft | 33.4 | 22.2 | 21.0 | 31.4 |
| 31 ft | 29.2 | 19.4 | 17.2 | 25.7 |
| 33 ft | 25.8 | 17.2 | 14.2 | 21.3 |
| 35 ft | 22.9 | 15.3 | 11.9 | 17.9 |
| 37 ft | 20.5 | 13.6 | 10.1 | 15.1 |
| 39 ft | 18.5 | 12.3 | 8.62 | 12.9 |
| 41 ft | 16.7 | 11.1 | 7.42 | 11.1 |
| 43 ft | 15.2 | 10.1 | 6.43 | 9.65 |
| 45 ft | 13.9 | 9.23 | 5.61 | 8.42 |
| 47 ft | 12.7 | 8.46 | 4.92 | 7.39 |
| 49 ft | 11.7 | 7.78 | 4.35 | 6.52 |
| 51 ft | 10.8 | 7.18 | 3.85 | 5.78 |
| 53 ft | 10.00 | 6.65 | 3.43 | 5.15 |
| 55 ft | 9.28 | 6.18 | 3.07 | 4.61 |
| 57 ft | 8.64 | 5.75 | 2.76 | 4.14 |
| 59 ft | 8.07 | 5.37 | 2.49 | 3.73 |
| 61 ft | 7.55 | 5.02 | 2.25 | 3.38 |
| 63 ft | 7.07 | 4.71 | 2.04 | 3.07 |
| 65 ft | 6.65 | 4.42 | 1.86 | 2.79 |
| 67 ft | 6.26 | 4.16 | 1.70 | 2.55 |
| 69 ft | 5.90 | 3.92 | 1.56 | 2.33 |
| 71 ft | 5.57 | 3.71 | 1.43 | 2.14 |
| 73 ft | 5.27 | 3.51 | 1.31 | 1.97 |
- 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 W27×281 carries a factored load of 13.9 kips per foot (LRFD) or an allowable load of 9.23 kips per foot (ASD). A live load of 5.61 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.
W27×281 questions
What does W27×281 mean?
W means a wide flange shape. 27 is its nominal depth in inches (the actual depth is 29.3 in) and 281 is its weight in pounds per foot.
How much does a W27×281 weigh?
281 pounds per foot, so a 20 ft W27×281 weighs about 5,620 pounds.
How far can a W27×281 span?
It depends on the load. Braced along its length, it carries 124.2 kips per foot of factored load at 15 ft and 5.27 kips per foot at 73 ft; the load table has the spans in between. Floor beams are often 44 to 59 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W27×281 a compact section?
Yes. Its flanges (bf/2tf = 3.72) and web (h/tw = 22.5) are both compact for bending in 50 ksi steel.