W14×398 Steel Beam
A W14×398 is a wide flange steel beam 18.3 inches deep with 16.6-inch flanges, weighing 398 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 3,004 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 972 kips.
Design a W14×398 beam Opens a 27 ft span in the free beam designer.
W14×398 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 18.3 in |
| Flange width, bf | 16.6 in |
| Flange thickness, tf | 2.85 in |
| Web thickness, tw | 1.77 in |
| Distance to web toe of fillet, kdes | 3.44 in |
| Distance between flange centroids, ho | 15.45 in |
| Cross-sectional area, A | 117 in2 |
| Weight | 398 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W14×398 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 6000 in4 | 2170 in4 |
| Elastic section modulus, S | 656 in3 | 262 in3 |
| Plastic section modulus, Z | 801 in3 | 402 in3 |
| Radius of gyration, r | 7.16 in | 4.31 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 273 in4 |
| Warping constant, Cw | 129000 in6 |
| Effective radius of gyration, rts | 5.05 in |
| Flange slenderness, bf/2tf | 2.92 |
| Web slenderness, h/tw | 6.44 |
W14×398 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 = 3,004 kip-ft | Mn/Ω = 1,999 kip-ft |
| Shear | φVn = 972 kips | Vn/Ω = 648 kips |
If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to Lp = 15.2 ft between braces it keeps its full strength; past Lr = 158.1 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 3,004 kip-ft | 1,999 kip-ft |
| 10 ft | 3,004 kip-ft | 1,999 kip-ft |
| 15.2 ft (Lp) | 3,004 kip-ft | 1,999 kip-ft |
| 20 ft | 2,961 kip-ft | 1,970 kip-ft |
| 30 ft | 2,871 kip-ft | 1,910 kip-ft |
| 40 ft | 2,781 kip-ft | 1,851 kip-ft |
| 50 ft | 2,692 kip-ft | 1,791 kip-ft |
| 60 ft | 2,602 kip-ft | 1,731 kip-ft |
| 70 ft | 2,512 kip-ft | 1,672 kip-ft |
| 80 ft | 2,423 kip-ft | 1,612 kip-ft |
| 90 ft | 2,333 kip-ft | 1,552 kip-ft |
| 100 ft | 2,243 kip-ft | 1,492 kip-ft |
| 110 ft | 2,153 kip-ft | 1,433 kip-ft |
| 158.1 ft (Lr) | 1,722 kip-ft | 1,146 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.
W14×398 load table by span
The largest uniform load a simply supported W14×398 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 0.398 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 9 ft | 215.9* | 144.0* | 353.6 | 530.4 |
| 11 ft | 176.7* | 117.8* | 193.7 | 290.5 |
| 13 ft | 142.2 | 94.6 | 117.3 | 176.0 |
| 15 ft | 106.8 | 71.1 | 76.4 | 114.6 |
| 17 ft | 83.1 | 55.3 | 52.5 | 78.7 |
| 19 ft | 66.6 | 44.3 | 37.6 | 56.4 |
| 21 ft | 54.5 | 36.3 | 27.8 | 41.8 |
| 23 ft | 45.4 | 30.2 | 21.2 | 31.8 |
| 25 ft | 38.4 | 25.6 | 16.5 | 24.7 |
| 27 ft | 33.0 | 21.9 | 13.1 | 19.6 |
| 29 ft | 28.6 | 19.0 | 10.6 | 15.9 |
| 31 ft | 25.0 | 16.6 | 8.65 | 13.0 |
| 33 ft | 22.1 | 14.7 | 7.17 | 10.8 |
| 35 ft | 19.6 | 13.1 | 6.01 | 9.02 |
| 37 ft | 17.6 | 11.7 | 5.09 | 7.63 |
| 39 ft | 15.8 | 10.5 | 4.35 | 6.52 |
| 41 ft | 14.3 | 9.51 | 3.74 | 5.61 |
| 43 ft | 13.0 | 8.65 | 3.24 | 4.86 |
| 45 ft | 11.9 | 7.90 | 2.83 | 4.24 |
- 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 27 ft span, a W14×398 carries a factored load of 33.0 kips per foot (LRFD) or an allowable load of 21.9 kips per foot (ASD). A live load of 13.1 kips per foot would deflect it span/360, which is 0.90 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.
W14×398 questions
What does W14×398 mean?
W means a wide flange shape. 14 is its nominal depth in inches (the actual depth is 18.3 in) and 398 is its weight in pounds per foot.
How much does a W14×398 weigh?
398 pounds per foot, so a 20 ft W14×398 weighs about 7,960 pounds.
How far can a W14×398 span?
It depends on the load. Braced along its length, it carries 215.9 kips per foot of factored load at 9 ft and 11.9 kips per foot at 45 ft; the load table has the spans in between. Floor beams are often 27 to 37 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W14×398 a compact section?
Yes. Its flanges (bf/2tf = 2.92) and web (h/tw = 6.44) are both compact for bending in 50 ksi steel.