W27×258 Steel Beam
A W27×258 is a wide flange steel beam 29 inches deep with 14.3-inch flanges, weighing 258 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 3,195 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 853 kips.
Design a W27×258 beam Opens a 45 ft span in the free beam designer.
W27×258 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 29.0 in |
| Flange width, bf | 14.3 in |
| Flange thickness, tf | 1.77 in |
| Web thickness, tw | 0.980 in |
| Distance to web toe of fillet, kdes | 2.56 in |
| Distance between flange centroids, ho | 27.23 in |
| Cross-sectional area, A | 76.0 in2 |
| Weight | 258 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W27×258 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 10800 in4 | 859 in4 |
| Elastic section modulus, S | 745 in3 | 120 in3 |
| Plastic section modulus, Z | 852 in3 | 187 in3 |
| Radius of gyration, r | 11.9 in | 3.36 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 61.6 in4 |
| Warping constant, Cw | 159000 in6 |
| Effective radius of gyration, rts | 3.96 in |
| Flange slenderness, bf/2tf | 4.03 |
| Web slenderness, h/tw | 24.4 |
W27×258 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 = 3,195 kip-ft | Mn/Ω = 2,126 kip-ft |
| Shear | φVn = 853 kips | Vn/Ω = 568 kips |
If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to Lp = 11.9 ft between braces it keeps its full strength; past Lr = 45.9 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 3,195 kip-ft | 2,126 kip-ft |
| 10 ft | 3,195 kip-ft | 2,126 kip-ft |
| 11.9 ft (Lp) | 3,195 kip-ft | 2,126 kip-ft |
| 20 ft | 2,899 kip-ft | 1,929 kip-ft |
| 30 ft | 2,534 kip-ft | 1,686 kip-ft |
| 40 ft | 2,170 kip-ft | 1,444 kip-ft |
| 45.9 ft (Lr) | 1,956 kip-ft | 1,301 kip-ft |
| 50 ft | 1,768 kip-ft | 1,176 kip-ft |
| 60 ft | 1,438 kip-ft | 957 kip-ft |
| 70 ft | 1,214 kip-ft | 808 kip-ft |
| 80 ft | 1,051 kip-ft | 699 kip-ft |
| 90 ft | 928 kip-ft | 617 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.
W27×258 load table by span
The largest uniform load a simply supported W27×258 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 0.258 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 15 ft | 113.6 | 75.6 | 137.5 | 206.2 |
| 17 ft | 88.4 | 58.8 | 94.4 | 141.7 |
| 19 ft | 70.8 | 47.1 | 67.6 | 101.5 |
| 21 ft | 58.0 | 38.6 | 50.1 | 75.2 |
| 23 ft | 48.3 | 32.1 | 38.1 | 57.2 |
| 25 ft | 40.9 | 27.2 | 29.7 | 44.5 |
| 27 ft | 35.1 | 23.3 | 23.6 | 35.4 |
| 29 ft | 30.4 | 20.2 | 19.0 | 28.5 |
| 31 ft | 26.6 | 17.7 | 15.6 | 23.4 |
| 33 ft | 23.5 | 15.6 | 12.9 | 19.4 |
| 35 ft | 20.9 | 13.9 | 10.8 | 16.2 |
| 37 ft | 18.7 | 12.4 | 9.16 | 13.7 |
| 39 ft | 16.8 | 11.2 | 7.82 | 11.7 |
| 41 ft | 15.2 | 10.1 | 6.73 | 10.1 |
| 43 ft | 13.8 | 9.20 | 5.84 | 8.75 |
| 45 ft | 12.6 | 8.40 | 5.09 | 7.64 |
| 47 ft | 11.6 | 7.70 | 4.47 | 6.70 |
| 49 ft | 10.6 | 7.08 | 3.94 | 5.92 |
| 51 ft | 9.83 | 6.54 | 3.50 | 5.25 |
| 53 ft | 9.10 | 6.05 | 3.12 | 4.68 |
| 55 ft | 8.45 | 5.62 | 2.79 | 4.18 |
| 57 ft | 7.87 | 5.23 | 2.51 | 3.76 |
| 59 ft | 7.34 | 4.89 | 2.26 | 3.39 |
| 61 ft | 6.87 | 4.57 | 2.04 | 3.07 |
| 63 ft | 6.44 | 4.28 | 1.86 | 2.78 |
| 65 ft | 6.05 | 4.03 | 1.69 | 2.53 |
| 67 ft | 5.69 | 3.79 | 1.54 | 2.31 |
| 69 ft | 5.37 | 3.57 | 1.41 | 2.12 |
| 71 ft | 5.07 | 3.37 | 1.30 | 1.94 |
| 73 ft | 4.80 | 3.19 | 1.19 | 1.79 |
- 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 W27×258 carries a factored load of 12.6 kips per foot (LRFD) or an allowable load of 8.40 kips per foot (ASD). A live load of 5.09 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.
W27×258 questions
What does W27×258 mean?
W means a wide flange shape. 27 is its nominal depth in inches (the actual depth is 29.0 in) and 258 is its weight in pounds per foot.
How much does a W27×258 weigh?
258 pounds per foot, so a 20 ft W27×258 weighs about 5,160 pounds.
How far can a W27×258 span?
It depends on the load. Braced along its length, it carries 113.6 kips per foot of factored load at 15 ft and 4.80 kips per foot at 73 ft; the load table has the spans in between. Floor beams are often 44 to 58 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W27×258 a compact section?
Yes. Its flanges (bf/2tf = 4.03) and web (h/tw = 24.4) are both compact for bending in 50 ksi steel.