W33×118 Steel Beam
A W33×118 is a wide flange steel beam 32.9 inches deep with 11.5-inch flanges, weighing 118 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 1,556 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 489 kips.
Design a W33×118 beam Opens a 50 ft span in the free beam designer.
W33×118 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 32.9 in |
| Flange width, bf | 11.5 in |
| Flange thickness, tf | 0.740 in |
| Web thickness, tw | 0.550 in |
| Distance to web toe of fillet, kdes | 1.44 in |
| Distance between flange centroids, ho | 32.16 in |
| Cross-sectional area, A | 34.7 in2 |
| Weight | 118 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W33×118 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 5900 in4 | 187 in4 |
| Elastic section modulus, S | 359 in3 | 32.6 in3 |
| Plastic section modulus, Z | 415 in3 | 51.3 in3 |
| Radius of gyration, r | 13.0 in | 2.32 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 5.30 in4 |
| Warping constant, Cw | 48300 in6 |
| Effective radius of gyration, rts | 2.89 in |
| Flange slenderness, bf/2tf | 7.76 |
| Web slenderness, h/tw | 54.5 |
W33×118 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 = 1,556 kip-ft | Mn/Ω = 1,035 kip-ft |
| Shear | φVn = 489 kips | Vn/Ω = 325 kips |
If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to Lp = 8.2 ft between braces it keeps its full strength; past Lr = 23.5 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 1,556 kip-ft | 1,035 kip-ft |
| 5 ft | 1,556 kip-ft | 1,035 kip-ft |
| 8.2 ft (Lp) | 1,556 kip-ft | 1,035 kip-ft |
| 10 ft | 1,484 kip-ft | 987 kip-ft |
| 15 ft | 1,283 kip-ft | 853 kip-ft |
| 20 ft | 1,082 kip-ft | 720 kip-ft |
| 23.5 ft (Lr) | 942 kip-ft | 627 kip-ft |
| 25 ft | 844 kip-ft | 561 kip-ft |
| 30 ft | 621 kip-ft | 413 kip-ft |
| 35 ft | 484 kip-ft | 322 kip-ft |
| 40 ft | 395 kip-ft | 263 kip-ft |
| 45 ft | 332 kip-ft | 221 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.
W33×118 load table by span
The largest uniform load a simply supported W33×118 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 0.118 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 16 ft | 48.6 | 32.4 | 61.9 | 92.8 |
| 18 ft | 38.4 | 25.6 | 43.5 | 65.2 |
| 20 ft | 31.1 | 20.7 | 31.7 | 47.5 |
| 22 ft | 25.7 | 17.1 | 23.8 | 35.7 |
| 24 ft | 21.6 | 14.4 | 18.3 | 27.5 |
| 26 ft | 18.4 | 12.3 | 14.4 | 21.6 |
| 28 ft | 15.9 | 10.6 | 11.5 | 17.3 |
| 30 ft | 13.8 | 9.20 | 9.39 | 14.1 |
| 32 ft | 12.2 | 8.09 | 7.74 | 11.6 |
| 34 ft | 10.8 | 7.17 | 6.45 | 9.67 |
| 36 ft | 9.61 | 6.39 | 5.43 | 8.15 |
| 38 ft | 8.62 | 5.74 | 4.62 | 6.93 |
| 40 ft | 7.78 | 5.18 | 3.96 | 5.94 |
| 42 ft | 7.06 | 4.70 | 3.42 | 5.13 |
| 44 ft | 6.43 | 4.28 | 2.98 | 4.46 |
| 46 ft | 5.88 | 3.91 | 2.60 | 3.91 |
| 48 ft | 5.40 | 3.60 | 2.29 | 3.44 |
| 50 ft | 4.98 | 3.31 | 2.03 | 3.04 |
| 52 ft | 4.60 | 3.06 | 1.80 | 2.70 |
| 54 ft | 4.27 | 2.84 | 1.61 | 2.41 |
| 56 ft | 3.97 | 2.64 | 1.44 | 2.17 |
| 58 ft | 3.70 | 2.46 | 1.30 | 1.95 |
| 60 ft | 3.46 | 2.30 | 1.17 | 1.76 |
| 62 ft | 3.24 | 2.15 | 1.06 | 1.60 |
| 64 ft | 3.04 | 2.02 | 0.97 | 1.45 |
| 66 ft | 2.86 | 1.90 | 0.88 | 1.32 |
| 68 ft | 2.69 | 1.79 | 0.81 | 1.21 |
| 70 ft | 2.54 | 1.69 | 0.74 | 1.11 |
| 72 ft | 2.40 | 1.60 | 0.68 | 1.02 |
| 74 ft | 2.27 | 1.51 | 0.63 | 0.94 |
| 76 ft | 2.16 | 1.43 | 0.58 | 0.87 |
| 78 ft | 2.05 | 1.36 | 0.53 | 0.80 |
| 80 ft | 1.95 | 1.29 | 0.50 | 0.74 |
| 82 ft | 1.85 | 1.23 | 0.46 | 0.69 |
- 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 50 ft span, a W33×118 carries a factored load of 4.98 kips per foot (LRFD) or an allowable load of 3.31 kips per foot (ASD). A live load of 2.03 kips per foot would deflect it span/360, which is 1.67 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.
W33×118 questions
What does W33×118 mean?
W means a wide flange shape. 33 is its nominal depth in inches (the actual depth is 32.9 in) and 118 is its weight in pounds per foot.
How much does a W33×118 weigh?
118 pounds per foot, so a 20 ft W33×118 weighs about 2,360 pounds.
How far can a W33×118 span?
It depends on the load. Braced along its length, it carries 48.6 kips per foot of factored load at 16 ft and 1.85 kips per foot at 82 ft; the load table has the spans in between. Floor beams are often 49 to 66 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W33×118 a compact section?
Yes. Its flanges (bf/2tf = 7.76) and web (h/tw = 54.5) are both compact for bending in 50 ksi steel.