W27×178 Steel Beam
A W27×178 is a wide flange steel beam 27.8 inches deep with 14.1-inch flanges, weighing 178 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 2,138 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 605 kips.
Design a W27×178 beam Opens a 42 ft span in the free beam designer.
W27×178 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 27.8 in |
| Flange width, bf | 14.1 in |
| Flange thickness, tf | 1.19 in |
| Web thickness, tw | 0.725 in |
| Distance to web toe of fillet, kdes | 1.98 in |
| Distance between flange centroids, ho | 26.61 in |
| Cross-sectional area, A | 52.5 in2 |
| Weight | 178 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W27×178 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 7020 in4 | 555 in4 |
| Elastic section modulus, S | 505 in3 | 78.8 in3 |
| Plastic section modulus, Z | 570 in3 | 122 in3 |
| Radius of gyration, r | 11.6 in | 3.25 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 20.1 in4 |
| Warping constant, Cw | 98400 in6 |
| Effective radius of gyration, rts | 3.83 in |
| Flange slenderness, bf/2tf | 5.92 |
| Web slenderness, h/tw | 32.9 |
W27×178 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 = 2,138 kip-ft | Mn/Ω = 1,422 kip-ft |
| Shear | φVn = 605 kips | Vn/Ω = 403 kips |
If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to Lp = 11.5 ft between braces it keeps its full strength; past Lr = 36.3 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 2,138 kip-ft | 1,422 kip-ft |
| 10 ft | 2,138 kip-ft | 1,422 kip-ft |
| 11.5 ft (Lp) | 2,137 kip-ft | 1,422 kip-ft |
| 20 ft | 1,859 kip-ft | 1,237 kip-ft |
| 30 ft | 1,532 kip-ft | 1,019 kip-ft |
| 36.3 ft (Lr) | 1,324 kip-ft | 881 kip-ft |
| 40 ft | 1,160 kip-ft | 772 kip-ft |
| 50 ft | 867 kip-ft | 577 kip-ft |
| 60 ft | 693 kip-ft | 461 kip-ft |
| 70 ft | 579 kip-ft | 385 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.
W27×178 load table by span
The largest uniform load a simply supported W27×178 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 0.178 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 14 ft | 86.4* | 57.6* | 109.9 | 164.9 |
| 16 ft | 66.8 | 44.4 | 73.6 | 110.4 |
| 18 ft | 52.8 | 35.1 | 51.7 | 77.6 |
| 20 ft | 42.8 | 28.4 | 37.7 | 56.6 |
| 22 ft | 35.3 | 23.5 | 28.3 | 42.5 |
| 24 ft | 29.7 | 19.8 | 21.8 | 32.7 |
| 26 ft | 25.3 | 16.8 | 17.2 | 25.7 |
| 28 ft | 21.8 | 14.5 | 13.7 | 20.6 |
| 30 ft | 19.0 | 12.6 | 11.2 | 16.8 |
| 32 ft | 16.7 | 11.1 | 9.20 | 13.8 |
| 34 ft | 14.8 | 9.84 | 7.67 | 11.5 |
| 36 ft | 13.2 | 8.78 | 6.46 | 9.70 |
| 38 ft | 11.8 | 7.88 | 5.50 | 8.24 |
| 40 ft | 10.7 | 7.11 | 4.71 | 7.07 |
| 42 ft | 9.69 | 6.45 | 4.07 | 6.11 |
| 44 ft | 8.83 | 5.88 | 3.54 | 5.31 |
| 46 ft | 8.08 | 5.38 | 3.10 | 4.65 |
| 48 ft | 7.42 | 4.94 | 2.73 | 4.09 |
| 50 ft | 6.84 | 4.55 | 2.41 | 3.62 |
| 52 ft | 6.32 | 4.21 | 2.14 | 3.22 |
| 54 ft | 5.86 | 3.90 | 1.92 | 2.87 |
| 56 ft | 5.45 | 3.63 | 1.72 | 2.58 |
| 58 ft | 5.08 | 3.38 | 1.55 | 2.32 |
| 60 ft | 4.75 | 3.16 | 1.40 | 2.09 |
| 62 ft | 4.45 | 2.96 | 1.27 | 1.90 |
| 64 ft | 4.17 | 2.78 | 1.15 | 1.73 |
| 66 ft | 3.93 | 2.61 | 1.05 | 1.57 |
| 68 ft | 3.70 | 2.46 | 0.96 | 1.44 |
| 70 ft | 3.49 | 2.32 | 0.88 | 1.32 |
- 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 42 ft span, a W27×178 carries a factored load of 9.69 kips per foot (LRFD) or an allowable load of 6.45 kips per foot (ASD). A live load of 4.07 kips per foot would deflect it span/360, which is 1.40 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.
W27×178 questions
What does W27×178 mean?
W means a wide flange shape. 27 is its nominal depth in inches (the actual depth is 27.8 in) and 178 is its weight in pounds per foot.
How much does a W27×178 weigh?
178 pounds per foot, so a 20 ft W27×178 weighs about 3,560 pounds.
How far can a W27×178 span?
It depends on the load. Braced along its length, it carries 86.4 kips per foot of factored load at 14 ft and 3.49 kips per foot at 70 ft; the load table has the spans in between. Floor beams are often 42 to 56 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W27×178 a compact section?
Yes. Its flanges (bf/2tf = 5.92) and web (h/tw = 32.9) are both compact for bending in 50 ksi steel.