W12×87 Steel Beam
A W12×87 is a wide flange steel beam 12.5 inches deep with 12.1-inch flanges, weighing 87 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 495 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 193 kips.
Design a W12×87 beam Opens a 18 ft span in the free beam designer.
W12×87 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 12.5 in |
| Flange width, bf | 12.1 in |
| Flange thickness, tf | 0.810 in |
| Web thickness, tw | 0.515 in |
| Distance to web toe of fillet, kdes | 1.41 in |
| Distance between flange centroids, ho | 11.69 in |
| Cross-sectional area, A | 25.6 in2 |
| Weight | 87 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W12×87 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 740 in4 | 241 in4 |
| Elastic section modulus, S | 118 in3 | 39.7 in3 |
| Plastic section modulus, Z | 132 in3 | 60.4 in3 |
| Radius of gyration, r | 5.38 in | 3.07 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 5.10 in4 |
| Warping constant, Cw | 8270 in6 |
| Effective radius of gyration, rts | 3.46 in |
| Flange slenderness, bf/2tf | 7.48 |
| Web slenderness, h/tw | 18.9 |
W12×87 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 = 495 kip-ft | Mn/Ω = 329 kip-ft |
| Shear | φVn = 193 kips | Vn/Ω = 129 kips |
If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to Lp = 10.8 ft between braces it keeps its full strength; past Lr = 43.1 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 495 kip-ft | 329 kip-ft |
| 10 ft | 495 kip-ft | 329 kip-ft |
| 10.8 ft (Lp) | 495 kip-ft | 329 kip-ft |
| 20 ft | 442 kip-ft | 294 kip-ft |
| 30 ft | 385 kip-ft | 256 kip-ft |
| 40 ft | 327 kip-ft | 218 kip-ft |
| 43.1 ft (Lr) | 310 kip-ft | 206 kip-ft |
| 50 ft | 262 kip-ft | 174 kip-ft |
| 60 ft | 215 kip-ft | 143 kip-ft |
| 70 ft | 182 kip-ft | 121 kip-ft |
| 80 ft | 158 kip-ft | 105 kip-ft |
| 90 ft | 140 kip-ft | 93.3 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.
W12×87 load table by span
The largest uniform load a simply supported W12×87 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 0.087 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 6 ft | 64.4* | 42.9* | 147.2 | 220.8 |
| 8 ft | 48.3* | 32.2* | 62.1 | 93.1 |
| 10 ft | 38.6* | 25.8* | 31.8 | 47.7 |
| 12 ft | 27.5 | 18.3 | 18.4 | 27.6 |
| 14 ft | 20.2 | 13.4 | 11.6 | 17.4 |
| 16 ft | 15.5 | 10.3 | 7.76 | 11.6 |
| 18 ft | 12.2 | 8.13 | 5.45 | 8.18 |
| 20 ft | 9.90 | 6.59 | 3.97 | 5.96 |
| 22 ft | 8.18 | 5.44 | 2.99 | 4.48 |
| 24 ft | 6.88 | 4.57 | 2.30 | 3.45 |
| 26 ft | 5.86 | 3.90 | 1.81 | 2.71 |
| 28 ft | 5.05 | 3.36 | 1.45 | 2.17 |
| 30 ft | 4.40 | 2.93 | 1.18 | 1.77 |
- 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 18 ft span, a W12×87 carries a factored load of 12.2 kips per foot (LRFD) or an allowable load of 8.13 kips per foot (ASD). A live load of 5.45 kips per foot would deflect it span/360, which is 0.60 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.
W12×87 questions
What does W12×87 mean?
W means a wide flange shape. 12 is its nominal depth in inches (the actual depth is 12.5 in) and 87 is its weight in pounds per foot.
How much does a W12×87 weigh?
87 pounds per foot, so a 20 ft W12×87 weighs about 1,740 pounds.
How far can a W12×87 span?
It depends on the load. Braced along its length, it carries 64.4 kips per foot of factored load at 6 ft and 4.40 kips per foot at 30 ft; the load table has the spans in between. Floor beams are often 19 to 25 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W12×87 a compact section?
Yes. Its flanges (bf/2tf = 7.48) and web (h/tw = 18.9) are both compact for bending in 50 ksi steel.