W21×132 Steel Beam
A W21×132 is a wide flange steel beam 21.8 inches deep with 12.4-inch flanges, weighing 132 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 1,249 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 425 kips.
Design a W21×132 beam Opens a 33 ft span in the free beam designer.
W21×132 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 21.8 in |
| Flange width, bf | 12.4 in |
| Flange thickness, tf | 1.04 in |
| Web thickness, tw | 0.650 in |
| Distance to web toe of fillet, kdes | 1.54 in |
| Distance between flange centroids, ho | 20.76 in |
| Cross-sectional area, A | 38.8 in2 |
| Weight | 132 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W21×132 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 3220 in4 | 333 in4 |
| Elastic section modulus, S | 295 in3 | 53.5 in3 |
| Plastic section modulus, Z | 333 in3 | 82.3 in3 |
| Radius of gyration, r | 9.12 in | 2.93 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 11.3 in4 |
| Warping constant, Cw | 36000 in6 |
| Effective radius of gyration, rts | 3.43 in |
| Flange slenderness, bf/2tf | 6.01 |
| Web slenderness, h/tw | 28.9 |
W21×132 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 = 1,249 kip-ft | Mn/Ω = 831 kip-ft |
| Shear | φVn = 425 kips | Vn/Ω = 283 kips |
If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to Lp = 10.3 ft between braces it keeps its full strength; past Lr = 34.2 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 1,249 kip-ft | 831 kip-ft |
| 10 ft | 1,249 kip-ft | 831 kip-ft |
| 10.4 ft (Lp) | 1,249 kip-ft | 831 kip-ft |
| 20 ft | 1,057 kip-ft | 703 kip-ft |
| 30 ft | 857 kip-ft | 570 kip-ft |
| 34.2 ft (Lr) | 774 kip-ft | 515 kip-ft |
| 40 ft | 631 kip-ft | 420 kip-ft |
| 50 ft | 480 kip-ft | 320 kip-ft |
| 60 ft | 389 kip-ft | 259 kip-ft |
| 70 ft | 327 kip-ft | 218 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.
W21×132 load table by span
The largest uniform load a simply supported W21×132 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 0.132 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 11 ft | 77.3* | 51.5* | 103.9 | 155.9 |
| 13 ft | 59.1 | 39.3 | 63.0 | 94.5 |
| 15 ft | 44.4 | 29.5 | 41.0 | 61.5 |
| 17 ft | 34.6 | 23.0 | 28.2 | 42.2 |
| 19 ft | 27.7 | 18.4 | 20.2 | 30.3 |
| 21 ft | 22.7 | 15.1 | 14.9 | 22.4 |
| 23 ft | 18.9 | 12.6 | 11.4 | 17.1 |
| 25 ft | 16.0 | 10.6 | 8.85 | 13.3 |
| 27 ft | 13.7 | 9.12 | 7.03 | 10.5 |
| 29 ft | 11.9 | 7.90 | 5.67 | 8.51 |
| 31 ft | 10.4 | 6.92 | 4.64 | 6.97 |
| 33 ft | 9.17 | 6.10 | 3.85 | 5.77 |
| 35 ft | 8.16 | 5.43 | 3.23 | 4.84 |
| 37 ft | 7.30 | 4.86 | 2.73 | 4.10 |
| 39 ft | 6.57 | 4.37 | 2.33 | 3.50 |
| 41 ft | 5.94 | 3.95 | 2.01 | 3.01 |
| 43 ft | 5.40 | 3.59 | 1.74 | 2.61 |
| 45 ft | 4.93 | 3.28 | 1.52 | 2.28 |
| 47 ft | 4.52 | 3.01 | 1.33 | 2.00 |
| 49 ft | 4.16 | 2.77 | 1.18 | 1.76 |
| 51 ft | 3.84 | 2.56 | 1.04 | 1.56 |
| 53 ft | 3.56 | 2.37 | 0.93 | 1.39 |
| 55 ft | 3.30 | 2.20 | 0.83 | 1.25 |
- 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 33 ft span, a W21×132 carries a factored load of 9.17 kips per foot (LRFD) or an allowable load of 6.10 kips per foot (ASD). A live load of 3.85 kips per foot would deflect it span/360, which is 1.10 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.
W21×132 questions
What does W21×132 mean?
W means a wide flange shape. 21 is its nominal depth in inches (the actual depth is 21.8 in) and 132 is its weight in pounds per foot.
How much does a W21×132 weigh?
132 pounds per foot, so a 20 ft W21×132 weighs about 2,640 pounds.
How far can a W21×132 span?
It depends on the load. Braced along its length, it carries 77.3 kips per foot of factored load at 11 ft and 3.30 kips per foot at 55 ft; the load table has the spans in between. Floor beams are often 33 to 44 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W21×132 a compact section?
Yes. Its flanges (bf/2tf = 6.01) and web (h/tw = 28.9) are both compact for bending in 50 ksi steel.