W36×231 Steel Beam
A W36×231 is a wide flange steel beam 36.5 inches deep with 16.5-inch flanges, weighing 231 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 3,611 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 832 kips.
Design a W36×231 beam Opens a 54 ft span in the free beam designer.
W36×231 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 36.5 in |
| Flange width, bf | 16.5 in |
| Flange thickness, tf | 1.26 in |
| Web thickness, tw | 0.760 in |
| Distance to web toe of fillet, kdes | 2.21 in |
| Distance between flange centroids, ho | 35.24 in |
| Cross-sectional area, A | 68.1 in2 |
| Weight | 231 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W36×231 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 15600 in4 | 940 in4 |
| Elastic section modulus, S | 854 in3 | 114 in3 |
| Plastic section modulus, Z | 963 in3 | 176 in3 |
| Radius of gyration, r | 15.1 in | 3.71 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 28.7 in4 |
| Warping constant, Cw | 292000 in6 |
| Effective radius of gyration, rts | 4.40 in |
| Flange slenderness, bf/2tf | 6.54 |
| Web slenderness, h/tw | 42.2 |
W36×231 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 = 3,611 kip-ft | Mn/Ω = 2,403 kip-ft |
| Shear | φVn = 832 kips | Vn/Ω = 555 kips |
If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to Lp = 13.1 ft between braces it keeps its full strength; past Lr = 38.6 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 3,611 kip-ft | 2,403 kip-ft |
| 10 ft | 3,611 kip-ft | 2,403 kip-ft |
| 13.1 ft (Lp) | 3,611 kip-ft | 2,403 kip-ft |
| 20 ft | 3,241 kip-ft | 2,156 kip-ft |
| 30 ft | 2,703 kip-ft | 1,799 kip-ft |
| 38.6 ft (Lr) | 2,239 kip-ft | 1,490 kip-ft |
| 40 ft | 2,118 kip-ft | 1,409 kip-ft |
| 50 ft | 1,524 kip-ft | 1,014 kip-ft |
| 60 ft | 1,186 kip-ft | 789 kip-ft |
| 70 ft | 970 kip-ft | 646 kip-ft |
| 80 ft | 822 kip-ft | 547 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.
W36×231 load table by span
The largest uniform load a simply supported W36×231 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 0.231 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 18 ft | 89.2 | 59.3 | 114.9 | 172.4 |
| 20 ft | 72.2 | 48.1 | 83.8 | 125.7 |
| 22 ft | 59.7 | 39.7 | 62.9 | 94.4 |
| 24 ft | 50.2 | 33.4 | 48.5 | 72.7 |
| 26 ft | 42.7 | 28.4 | 38.1 | 57.2 |
| 28 ft | 36.8 | 24.5 | 30.5 | 45.8 |
| 30 ft | 32.1 | 21.4 | 24.8 | 37.2 |
| 32 ft | 28.2 | 18.8 | 20.5 | 30.7 |
| 34 ft | 25.0 | 16.6 | 17.1 | 25.6 |
| 36 ft | 22.3 | 14.8 | 14.4 | 21.5 |
| 38 ft | 20.0 | 13.3 | 12.2 | 18.3 |
| 40 ft | 18.1 | 12.0 | 10.5 | 15.7 |
| 42 ft | 16.4 | 10.9 | 9.05 | 13.6 |
| 44 ft | 14.9 | 9.93 | 7.87 | 11.8 |
| 46 ft | 13.7 | 9.08 | 6.89 | 10.3 |
| 48 ft | 12.5 | 8.34 | 6.06 | 9.09 |
| 50 ft | 11.6 | 7.69 | 5.36 | 8.04 |
| 52 ft | 10.7 | 7.11 | 4.77 | 7.15 |
| 54 ft | 9.91 | 6.59 | 4.26 | 6.38 |
| 56 ft | 9.21 | 6.13 | 3.82 | 5.72 |
| 58 ft | 8.59 | 5.71 | 3.44 | 5.15 |
| 60 ft | 8.02 | 5.34 | 3.10 | 4.65 |
| 62 ft | 7.52 | 5.00 | 2.81 | 4.22 |
| 64 ft | 7.05 | 4.69 | 2.56 | 3.84 |
| 66 ft | 6.63 | 4.41 | 2.33 | 3.50 |
| 68 ft | 6.25 | 4.16 | 2.13 | 3.20 |
| 70 ft | 5.90 | 3.92 | 1.95 | 2.93 |
| 72 ft | 5.57 | 3.71 | 1.80 | 2.69 |
| 74 ft | 5.28 | 3.51 | 1.65 | 2.48 |
| 76 ft | 5.00 | 3.33 | 1.53 | 2.29 |
| 78 ft | 4.75 | 3.16 | 1.41 | 2.12 |
| 80 ft | 4.51 | 3.00 | 1.31 | 1.96 |
| 82 ft | 4.30 | 2.86 | 1.22 | 1.82 |
| 84 ft | 4.09 | 2.72 | 1.13 | 1.70 |
| 86 ft | 3.91 | 2.60 | 1.05 | 1.58 |
| 88 ft | 3.73 | 2.48 | 0.98 | 1.48 |
| 90 ft | 3.57 | 2.37 | 0.92 | 1.38 |
- 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 54 ft span, a W36×231 carries a factored load of 9.91 kips per foot (LRFD) or an allowable load of 6.59 kips per foot (ASD). A live load of 4.26 kips per foot would deflect it span/360, which is 1.80 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.
W36×231 questions
What does W36×231 mean?
W means a wide flange shape. 36 is its nominal depth in inches (the actual depth is 36.5 in) and 231 is its weight in pounds per foot.
How much does a W36×231 weigh?
231 pounds per foot, so a 20 ft W36×231 weighs about 4,620 pounds.
How far can a W36×231 span?
It depends on the load. Braced along its length, it carries 89.2 kips per foot of factored load at 18 ft and 3.57 kips per foot at 90 ft; the load table has the spans in between. Floor beams are often 55 to 73 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W36×231 a compact section?
Yes. Its flanges (bf/2tf = 6.54) and web (h/tw = 42.2) are both compact for bending in 50 ksi steel.