W18×234 Steel Beam
A W18×234 is a wide flange steel beam 21.1 inches deep with 11.7-inch flanges, weighing 234 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 2,059 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 734 kips.
Design a W18×234 beam Opens a 33 ft span in the free beam designer.
W18×234 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 21.1 in |
| Flange width, bf | 11.7 in |
| Flange thickness, tf | 2.11 in |
| Web thickness, tw | 1.16 in |
| Distance to web toe of fillet, kdes | 2.51 in |
| Distance between flange centroids, ho | 18.99 in |
| Cross-sectional area, A | 68.8 in2 |
| Weight | 234 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W18×234 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 4900 in4 | 558 in4 |
| Elastic section modulus, S | 466 in3 | 95.8 in3 |
| Plastic section modulus, Z | 549 in3 | 149 in3 |
| Radius of gyration, r | 8.44 in | 2.85 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 78.7 in4 |
| Warping constant, Cw | 50100 in6 |
| Effective radius of gyration, rts | 3.37 in |
| Flange slenderness, bf/2tf | 2.76 |
| Web slenderness, h/tw | 13.8 |
W18×234 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 = 2,059 kip-ft | Mn/Ω = 1,370 kip-ft |
| Shear | φVn = 734 kips | Vn/Ω = 490 kips |
If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to Lp = 10.1 ft between braces it keeps its full strength; past Lr = 61.4 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 2,059 kip-ft | 1,370 kip-ft |
| 10 ft (Lp) | 2,059 kip-ft | 1,370 kip-ft |
| 10.1 ft (Lp) | 2,059 kip-ft | 1,370 kip-ft |
| 20 ft | 1,897 kip-ft | 1,262 kip-ft |
| 30 ft | 1,734 kip-ft | 1,154 kip-ft |
| 40 ft | 1,571 kip-ft | 1,046 kip-ft |
| 50 ft | 1,409 kip-ft | 937 kip-ft |
| 60 ft | 1,246 kip-ft | 829 kip-ft |
| 61.4 ft (Lr) | 1,223 kip-ft | 814 kip-ft |
| 70 ft | 1,069 kip-ft | 711 kip-ft |
| 80 ft | 933 kip-ft | 620 kip-ft |
| 90 ft | 827 kip-ft | 551 kip-ft |
| 100 ft | 744 kip-ft | 495 kip-ft |
| 110 ft | 675 kip-ft | 449 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.
W18×234 load table by span
The largest uniform load a simply supported W18×234 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 0.234 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 11 ft | 133.5* | 89.0* | 158.2 | 237.2 |
| 13 ft | 97.5 | 64.8 | 95.8 | 143.7 |
| 15 ft | 73.2 | 48.7 | 62.4 | 93.6 |
| 17 ft | 57.0 | 37.9 | 42.8 | 64.3 |
| 19 ft | 45.6 | 30.4 | 30.7 | 46.0 |
| 21 ft | 37.3 | 24.8 | 22.7 | 34.1 |
| 23 ft | 31.1 | 20.7 | 17.3 | 26.0 |
| 25 ft | 26.4 | 17.5 | 13.5 | 20.2 |
| 27 ft | 22.6 | 15.0 | 10.7 | 16.0 |
| 29 ft | 19.6 | 13.0 | 8.63 | 12.9 |
| 31 ft | 17.1 | 11.4 | 7.07 | 10.6 |
| 33 ft | 15.1 | 10.1 | 5.86 | 8.79 |
| 35 ft | 13.4 | 8.95 | 4.91 | 7.37 |
| 37 ft | 12.0 | 8.00 | 4.16 | 6.23 |
| 39 ft | 10.8 | 7.20 | 3.55 | 5.32 |
| 41 ft | 9.80 | 6.52 | 3.05 | 4.58 |
| 43 ft | 8.91 | 5.93 | 2.65 | 3.97 |
| 45 ft | 8.13 | 5.41 | 2.31 | 3.47 |
| 47 ft | 7.46 | 4.96 | 2.03 | 3.04 |
| 49 ft | 6.86 | 4.56 | 1.79 | 2.68 |
| 51 ft | 6.33 | 4.21 | 1.59 | 2.38 |
| 53 ft | 5.86 | 3.90 | 1.41 | 2.12 |
- 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 33 ft span, a W18×234 carries a factored load of 15.1 kips per foot (LRFD) or an allowable load of 10.1 kips per foot (ASD). A live load of 5.86 kips per foot would deflect it span/360, which is 1.10 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.
W18×234 questions
What does W18×234 mean?
W means a wide flange shape. 18 is its nominal depth in inches (the actual depth is 21.1 in) and 234 is its weight in pounds per foot.
How much does a W18×234 weigh?
234 pounds per foot, so a 20 ft W18×234 weighs about 4,680 pounds.
How far can a W18×234 span?
It depends on the load. Braced along its length, it carries 133.5 kips per foot of factored load at 11 ft and 5.86 kips per foot at 53 ft; the load table has the spans in between. Floor beams are often 32 to 42 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W18×234 a compact section?
Yes. Its flanges (bf/2tf = 2.76) and web (h/tw = 13.8) are both compact for bending in 50 ksi steel.