W36×170 Steel Beam
A W36×170 is a wide flange steel beam 36.2 inches deep with 12-inch flanges, weighing 170 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 2,505 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 738 kips.
Design a W36×170 beam Opens a 54 ft span in the free beam designer.
W36×170 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 36.2 in |
| Flange width, bf | 12.0 in |
| Flange thickness, tf | 1.10 in |
| Web thickness, tw | 0.680 in |
| Distance to web toe of fillet, kdes | 1.85 in |
| Distance between flange centroids, ho | 35.10 in |
| Cross-sectional area, A | 50.1 in2 |
| Weight | 170 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W36×170 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 10500 in4 | 320 in4 |
| Elastic section modulus, S | 581 in3 | 53.2 in3 |
| Plastic section modulus, Z | 668 in3 | 83.8 in3 |
| Radius of gyration, r | 14.5 in | 2.53 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 15.1 in4 |
| Warping constant, Cw | 98500 in6 |
| Effective radius of gyration, rts | 3.11 in |
| Flange slenderness, bf/2tf | 5.47 |
| Web slenderness, h/tw | 47.7 |
W36×170 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 = 2,505 kip-ft | Mn/Ω = 1,667 kip-ft |
| Shear | φVn = 738 kips | Vn/Ω = 492 kips |
If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to Lp = 8.9 ft between braces it keeps its full strength; past Lr = 26.4 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 2,505 kip-ft | 1,667 kip-ft |
| 5 ft | 2,505 kip-ft | 1,667 kip-ft |
| 8.9 ft (Lp) | 2,505 kip-ft | 1,667 kip-ft |
| 10 ft | 2,445 kip-ft | 1,627 kip-ft |
| 15 ft | 2,164 kip-ft | 1,440 kip-ft |
| 20 ft | 1,883 kip-ft | 1,253 kip-ft |
| 25 ft | 1,601 kip-ft | 1,065 kip-ft |
| 26.4 ft (Lr) | 1,525 kip-ft | 1,015 kip-ft |
| 30 ft | 1,239 kip-ft | 824 kip-ft |
| 35 ft | 979 kip-ft | 652 kip-ft |
| 40 ft | 806 kip-ft | 537 kip-ft |
| 45 ft | 684 kip-ft | 455 kip-ft |
| 50 ft | 594 kip-ft | 395 kip-ft |
| 55 ft | 525 kip-ft | 349 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.
W36×170 load table by span
The largest uniform load a simply supported W36×170 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 0.170 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 18 ft | 61.9 | 41.2 | 77.4 | 116.0 |
| 20 ft | 50.1 | 33.3 | 56.4 | 84.6 |
| 22 ft | 41.4 | 27.5 | 42.4 | 63.5 |
| 24 ft | 34.8 | 23.1 | 32.6 | 48.9 |
| 26 ft | 29.6 | 19.7 | 25.7 | 38.5 |
| 28 ft | 25.6 | 17.0 | 20.5 | 30.8 |
| 30 ft | 22.3 | 14.8 | 16.7 | 25.1 |
| 32 ft | 19.6 | 13.0 | 13.8 | 20.7 |
| 34 ft | 17.3 | 11.5 | 11.5 | 17.2 |
| 36 ft | 15.5 | 10.3 | 9.67 | 14.5 |
| 38 ft | 13.9 | 9.23 | 8.22 | 12.3 |
| 40 ft | 12.5 | 8.33 | 7.05 | 10.6 |
| 42 ft | 11.4 | 7.56 | 6.09 | 9.13 |
| 44 ft | 10.4 | 6.89 | 5.30 | 7.94 |
| 46 ft | 9.47 | 6.30 | 4.63 | 6.95 |
| 48 ft | 8.70 | 5.79 | 4.08 | 6.12 |
| 50 ft | 8.02 | 5.33 | 3.61 | 5.41 |
| 52 ft | 7.41 | 4.93 | 3.21 | 4.81 |
| 54 ft | 6.87 | 4.57 | 2.86 | 4.30 |
| 56 ft | 6.39 | 4.25 | 2.57 | 3.85 |
| 58 ft | 5.96 | 3.96 | 2.31 | 3.47 |
| 60 ft | 5.57 | 3.70 | 2.09 | 3.13 |
| 62 ft | 5.21 | 3.47 | 1.89 | 2.84 |
| 64 ft | 4.89 | 3.26 | 1.72 | 2.58 |
| 66 ft | 4.60 | 3.06 | 1.57 | 2.35 |
| 68 ft | 4.33 | 2.88 | 1.43 | 2.15 |
| 70 ft | 4.09 | 2.72 | 1.32 | 1.97 |
| 72 ft | 3.87 | 2.57 | 1.21 | 1.81 |
| 74 ft | 3.66 | 2.43 | 1.11 | 1.67 |
| 76 ft | 3.47 | 2.31 | 1.03 | 1.54 |
| 78 ft | 3.29 | 2.19 | 0.95 | 1.43 |
| 80 ft | 3.13 | 2.08 | 0.88 | 1.32 |
| 82 ft | 2.98 | 1.98 | 0.82 | 1.23 |
| 84 ft | 2.84 | 1.89 | 0.76 | 1.14 |
| 86 ft | 2.71 | 1.80 | 0.71 | 1.06 |
| 88 ft | 2.59 | 1.72 | 0.66 | 0.99 |
| 90 ft | 2.47 | 1.65 | 0.62 | 0.93 |
- 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 54 ft span, a W36×170 carries a factored load of 6.87 kips per foot (LRFD) or an allowable load of 4.57 kips per foot (ASD). A live load of 2.86 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.
W36×170 questions
What does W36×170 mean?
W means a wide flange shape. 36 is its nominal depth in inches (the actual depth is 36.2 in) and 170 is its weight in pounds per foot.
How much does a W36×170 weigh?
170 pounds per foot, so a 20 ft W36×170 weighs about 3,400 pounds.
How far can a W36×170 span?
It depends on the load. Braced along its length, it carries 61.9 kips per foot of factored load at 18 ft and 2.47 kips per foot at 90 ft; the load table has the spans in between. Floor beams are often 54 to 72 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W36×170 a compact section?
Yes. Its flanges (bf/2tf = 5.47) and web (h/tw = 47.7) are both compact for bending in 50 ksi steel.