W36×361 Steel Beam
A W36×361 is a wide flange steel beam 38 inches deep with 16.7-inch flanges, weighing 361 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 5,813 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 1,277 kips.
Design a W36×361 beam Opens a 57 ft span in the free beam designer.
W36×361 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 38.0 in |
| Flange width, bf | 16.7 in |
| Flange thickness, tf | 2.01 in |
| Web thickness, tw | 1.12 in |
| Distance to web toe of fillet, kdes | 2.96 in |
| Distance between flange centroids, ho | 35.99 in |
| Cross-sectional area, A | 106 in2 |
| Weight | 361 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W36×361 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 25700 in4 | 1570 in4 |
| Elastic section modulus, S | 1350 in3 | 188 in3 |
| Plastic section modulus, Z | 1550 in3 | 293 in3 |
| Radius of gyration, r | 15.6 in | 3.85 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 109 in4 |
| Warping constant, Cw | 509000 in6 |
| Effective radius of gyration, rts | 4.58 in |
| Flange slenderness, bf/2tf | 4.16 |
| Web slenderness, h/tw | 28.6 |
W36×361 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 = 5,813 kip-ft | Mn/Ω = 3,867 kip-ft |
| Shear | φVn = 1,277 kips | Vn/Ω = 851 kips |
If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to Lp = 13.6 ft between braces it keeps its full strength; past Lr = 48.1 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 5,813 kip-ft | 3,867 kip-ft |
| 10 ft | 5,813 kip-ft | 3,867 kip-ft |
| 13.6 ft (Lp) | 5,812 kip-ft | 3,867 kip-ft |
| 20 ft | 5,392 kip-ft | 3,587 kip-ft |
| 30 ft | 4,735 kip-ft | 3,150 kip-ft |
| 40 ft | 4,078 kip-ft | 2,713 kip-ft |
| 48.1 ft (Lr) | 3,544 kip-ft | 2,358 kip-ft |
| 50 ft | 3,375 kip-ft | 2,245 kip-ft |
| 60 ft | 2,703 kip-ft | 1,798 kip-ft |
| 70 ft | 2,259 kip-ft | 1,503 kip-ft |
| 80 ft | 1,942 kip-ft | 1,292 kip-ft |
| 90 ft | 1,706 kip-ft | 1,135 kip-ft |
| 100 ft | 1,521 kip-ft | 1,012 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.
W36×361 load table by span
The largest uniform load a simply supported W36×361 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 0.361 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 19 ft | 128.8 | 85.7 | 161.0 | 241.5 |
| 21 ft | 105.4 | 70.2 | 119.2 | 178.8 |
| 23 ft | 87.9 | 58.5 | 90.7 | 136.1 |
| 25 ft | 74.4 | 49.5 | 70.7 | 106.0 |
| 27 ft | 63.8 | 42.4 | 56.1 | 84.1 |
| 29 ft | 55.3 | 36.8 | 45.3 | 67.9 |
| 31 ft | 48.4 | 32.2 | 37.1 | 55.6 |
| 33 ft | 42.7 | 28.4 | 30.7 | 46.1 |
| 35 ft | 38.0 | 25.3 | 25.8 | 38.6 |
| 37 ft | 34.0 | 22.6 | 21.8 | 32.7 |
| 39 ft | 30.6 | 20.3 | 18.6 | 27.9 |
| 41 ft | 27.7 | 18.4 | 16.0 | 24.0 |
| 43 ft | 25.1 | 16.7 | 13.9 | 20.8 |
| 45 ft | 23.0 | 15.3 | 12.1 | 18.2 |
| 47 ft | 21.1 | 14.0 | 10.6 | 16.0 |
| 49 ft | 19.4 | 12.9 | 9.39 | 14.1 |
| 51 ft | 17.9 | 11.9 | 8.32 | 12.5 |
| 53 ft | 16.6 | 11.0 | 7.42 | 11.1 |
| 55 ft | 15.4 | 10.2 | 6.64 | 9.95 |
| 57 ft | 14.3 | 9.52 | 5.96 | 8.94 |
| 59 ft | 13.4 | 8.89 | 5.38 | 8.06 |
| 61 ft | 12.5 | 8.31 | 4.86 | 7.30 |
| 63 ft | 11.7 | 7.79 | 4.42 | 6.62 |
| 65 ft | 11.0 | 7.32 | 4.02 | 6.03 |
| 67 ft | 10.4 | 6.89 | 3.67 | 5.51 |
| 69 ft | 9.77 | 6.50 | 3.36 | 5.04 |
| 71 ft | 9.22 | 6.14 | 3.08 | 4.63 |
| 73 ft | 8.73 | 5.81 | 2.84 | 4.26 |
| 75 ft | 8.27 | 5.50 | 2.62 | 3.93 |
| 77 ft | 7.84 | 5.22 | 2.42 | 3.63 |
| 79 ft | 7.45 | 4.96 | 2.24 | 3.36 |
| 81 ft | 7.09 | 4.72 | 2.08 | 3.12 |
| 83 ft | 6.75 | 4.49 | 1.93 | 2.90 |
| 85 ft | 6.44 | 4.28 | 1.80 | 2.70 |
| 87 ft | 6.14 | 4.09 | 1.68 | 2.52 |
| 89 ft | 5.87 | 3.91 | 1.57 | 2.35 |
| 91 ft | 5.62 | 3.74 | 1.47 | 2.20 |
| 93 ft | 5.38 | 3.58 | 1.37 | 2.06 |
| 95 ft | 5.15 | 3.43 | 1.29 | 1.93 |
- 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 57 ft span, a W36×361 carries a factored load of 14.3 kips per foot (LRFD) or an allowable load of 9.52 kips per foot (ASD). A live load of 5.96 kips per foot would deflect it span/360, which is 1.90 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.
W36×361 questions
What does W36×361 mean?
W means a wide flange shape. 36 is its nominal depth in inches (the actual depth is 38.0 in) and 361 is its weight in pounds per foot.
How much does a W36×361 weigh?
361 pounds per foot, so a 20 ft W36×361 weighs about 7,220 pounds.
How far can a W36×361 span?
It depends on the load. Braced along its length, it carries 128.8 kips per foot of factored load at 19 ft and 5.15 kips per foot at 95 ft; the load table has the spans in between. Floor beams are often 57 to 76 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W36×361 a compact section?
Yes. Its flanges (bf/2tf = 4.16) and web (h/tw = 28.6) are both compact for bending in 50 ksi steel.