W30×173 Steel Beam
A W30×173 is a wide flange steel beam 30.4 inches deep with 15-inch flanges, weighing 173 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 2,276 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 597 kips.
Design a W30×173 beam Opens a 45 ft span in the free beam designer.
W30×173 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 30.4 in |
| Flange width, bf | 15.0 in |
| Flange thickness, tf | 1.07 in |
| Web thickness, tw | 0.655 in |
| Distance to web toe of fillet, kdes | 1.85 in |
| Distance between flange centroids, ho | 29.33 in |
| Cross-sectional area, A | 51.0 in2 |
| Weight | 173 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W30×173 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 8230 in4 | 598 in4 |
| Elastic section modulus, S | 541 in3 | 79.8 in3 |
| Plastic section modulus, Z | 607 in3 | 123 in3 |
| Radius of gyration, r | 12.7 in | 3.42 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 15.6 in4 |
| Warping constant, Cw | 129000 in6 |
| Effective radius of gyration, rts | 4.03 in |
| Flange slenderness, bf/2tf | 7.04 |
| Web slenderness, h/tw | 40.8 |
W30×173 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 = 2,276 kip-ft | Mn/Ω = 1,514 kip-ft |
| Shear | φVn = 597 kips | Vn/Ω = 398 kips |
If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to Lp = 12.1 ft between braces it keeps its full strength; past Lr = 35.5 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 2,276 kip-ft | 1,514 kip-ft |
| 10 ft | 2,276 kip-ft | 1,514 kip-ft |
| 12.1 ft (Lp) | 2,276 kip-ft | 1,514 kip-ft |
| 20 ft | 1,986 kip-ft | 1,321 kip-ft |
| 30 ft | 1,620 kip-ft | 1,078 kip-ft |
| 35.5 ft (Lr) | 1,418 kip-ft | 944 kip-ft |
| 40 ft | 1,183 kip-ft | 787 kip-ft |
| 50 ft | 861 kip-ft | 573 kip-ft |
| 60 ft | 675 kip-ft | 449 kip-ft |
| 70 ft | 556 kip-ft | 370 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.
W30×173 load table by span
The largest uniform load a simply supported W30×173 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 0.173 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 15 ft | 79.6* | 53.1* | 104.8 | 157.1 |
| 17 ft | 63.0 | 41.9 | 72.0 | 108.0 |
| 19 ft | 50.4 | 33.6 | 51.6 | 77.3 |
| 21 ft | 41.3 | 27.5 | 38.2 | 57.3 |
| 23 ft | 34.4 | 22.9 | 29.1 | 43.6 |
| 25 ft | 29.1 | 19.4 | 22.6 | 33.9 |
| 27 ft | 25.0 | 16.6 | 18.0 | 26.9 |
| 29 ft | 21.7 | 14.4 | 14.5 | 21.7 |
| 31 ft | 18.9 | 12.6 | 11.9 | 17.8 |
| 33 ft | 16.7 | 11.1 | 9.84 | 14.8 |
| 35 ft | 14.9 | 9.89 | 8.25 | 12.4 |
| 37 ft | 13.3 | 8.85 | 6.98 | 10.5 |
| 39 ft | 12.0 | 7.97 | 5.96 | 8.94 |
| 41 ft | 10.8 | 7.21 | 5.13 | 7.70 |
| 43 ft | 9.85 | 6.55 | 4.45 | 6.67 |
| 45 ft | 8.99 | 5.98 | 3.88 | 5.82 |
| 47 ft | 8.24 | 5.48 | 3.41 | 5.11 |
| 49 ft | 7.58 | 5.05 | 3.01 | 4.51 |
| 51 ft | 7.00 | 4.66 | 2.67 | 4.00 |
| 53 ft | 6.48 | 4.31 | 2.38 | 3.56 |
| 55 ft | 6.02 | 4.01 | 2.13 | 3.19 |
| 57 ft | 5.60 | 3.73 | 1.91 | 2.86 |
| 59 ft | 5.23 | 3.48 | 1.72 | 2.58 |
| 61 ft | 4.89 | 3.26 | 1.56 | 2.34 |
| 63 ft | 4.59 | 3.05 | 1.41 | 2.12 |
| 65 ft | 4.31 | 2.87 | 1.29 | 1.93 |
| 67 ft | 4.06 | 2.70 | 1.18 | 1.76 |
| 69 ft | 3.82 | 2.54 | 1.08 | 1.61 |
| 71 ft | 3.61 | 2.40 | 0.99 | 1.48 |
| 73 ft | 3.42 | 2.27 | 0.91 | 1.36 |
| 75 ft | 3.24 | 2.15 | 0.84 | 1.26 |
- 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 45 ft span, a W30×173 carries a factored load of 8.99 kips per foot (LRFD) or an allowable load of 5.98 kips per foot (ASD). A live load of 3.88 kips per foot would deflect it span/360, which is 1.50 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.
W30×173 questions
What does W30×173 mean?
W means a wide flange shape. 30 is its nominal depth in inches (the actual depth is 30.4 in) and 173 is its weight in pounds per foot.
How much does a W30×173 weigh?
173 pounds per foot, so a 20 ft W30×173 weighs about 3,460 pounds.
How far can a W30×173 span?
It depends on the load. Braced along its length, it carries 79.6 kips per foot of factored load at 15 ft and 3.24 kips per foot at 75 ft; the load table has the spans in between. Floor beams are often 46 to 61 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W30×173 a compact section?
Yes. Its flanges (bf/2tf = 7.04) and web (h/tw = 40.8) are both compact for bending in 50 ksi steel.