W36×800 Steel Beam

A W36×800 is a wide flange steel beam 42.6 inches deep with 18-inch flanges, weighing 800 pounds per foot. In ASTM A992 steel (F_y = 50 ksi) it has a design bending strength of 13,688 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 3,042 kips.

Weight800 lb/ft

Depth42.6 in

I_x64700 in⁴

S_x3040 in³

Z_x3650 in³

φM_n13,688 kip-ft

Design a W36×800 beam Opens a 65 ft span in the free beam designer.

W36×800 dimensions

Dimension	Value
Depth, d	42.6 in
Flange width, b_f	18.0 in
Flange thickness, t_f	4.29 in
Web thickness, t_w	2.38 in
Distance to web toe of fillet, k_des	5.24 in
Distance between flange centroids, h_o	38.31 in
Cross-sectional area, A	236 in²
Weight	800 lb/ft

Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.

W36×800 section properties

Property	Strong axis (x)	Weak axis (y)
Moment of inertia, I	64700 in⁴	4200 in⁴
Elastic section modulus, S	3040 in³	467 in³
Plastic section modulus, Z	3650 in³	743 in³
Radius of gyration, r	16.6 in	4.22 in

Torsion and slenderness	Value
Torsional constant, J	1060 in⁴
Warping constant, C_w	1540000 in⁶
Effective radius of gyration, r_ts	5.14 in
Flange slenderness, b_f/2t_f	2.10
Web slenderness, h/t_w	13.5

W36×800 bending and shear strength

For ASTM A992 steel (F_y = 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	φM_n = 13,688 kip-ft	M_n/Ω = 9,107 kip-ft
Shear	φV_n = 3,042 kips	V_n/Ω = 2,028 kips

If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to L_p = 14.9 ft between braces it keeps its full strength; past L_r = 94.8 ft it buckles elastically. With uniform moment between braces (C_b = 1.0):

Unbraced length, L_b	φM_n (LRFD)	M_n/Ω (ASD)
Braced	13,688 kip-ft	9,107 kip-ft
10 ft	13,688 kip-ft	9,107 kip-ft
14.9 ft (L_p)	13,687 kip-ft	9,107 kip-ft
20 ft	13,323 kip-ft	8,865 kip-ft
30 ft	12,609 kip-ft	8,389 kip-ft
40 ft	11,894 kip-ft	7,914 kip-ft
50 ft	11,180 kip-ft	7,438 kip-ft
60 ft	10,465 kip-ft	6,963 kip-ft
70 ft	9,750 kip-ft	6,487 kip-ft
80 ft	9,036 kip-ft	6,012 kip-ft
90 ft	8,321 kip-ft	5,536 kip-ft
94.8 ft (L_r)	7,976 kip-ft	5,306 kip-ft
100 ft	7,549 kip-ft	5,022 kip-ft
110 ft	6,847 kip-ft	4,556 kip-ft

A beam with a uniform load between braces has C_b above 1.0 (1.14 for a simple span braced only at its ends), so these values are conservative. The beam designer works out C_b for every segment between braces.

W36×800 load table by span

The largest uniform load a simply supported W36×800 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 0.800 kips per foot.

Span	Factored load (LRFD)	Allowable load (ASD)	Load at span/360	Load at span/240
21 ft	248.3	165.2	300.2	450.2
23 ft	207.0	137.7	228.5	342.7
25 ft	175.2	116.6	177.9	266.9
27 ft	150.2	99.9	141.2	211.8
29 ft	130.2	86.6	114.0	171.0
31 ft	113.9	75.8	93.3	140.0
33 ft	100.6	66.9	77.3	116.0
35 ft	89.4	59.5	64.8	97.2
37 ft	80.0	53.2	54.9	82.3
39 ft	72.0	47.9	46.9	70.3
41 ft	65.1	43.3	40.3	60.5
43 ft	59.2	39.4	35.0	52.4
45 ft	54.1	36.0	30.5	45.8
47 ft	49.6	33.0	26.8	40.2
49 ft	45.6	30.3	23.6	35.4
51 ft	42.1	28.0	21.0	31.4
53 ft	39.0	25.9	18.7	28.0
55 ft	36.2	24.1	16.7	25.1
57 ft	33.7	22.4	15.0	22.5
59 ft	31.5	20.9	13.5	20.3
61 ft	29.4	19.6	12.2	18.4
63 ft	27.6	18.4	11.1	16.7
65 ft	25.9	17.2	10.1	15.2
67 ft	24.4	16.2	9.24	13.9
69 ft	23.0	15.3	8.46	12.7
71 ft	21.7	14.5	7.77	11.6
73 ft	20.5	13.7	7.15	10.7
75 ft	19.5	13.0	6.59	9.88
77 ft	18.5	12.3	6.09	9.13
79 ft	17.5	11.7	5.64	8.46
81 ft	16.7	11.1	5.23	7.85
83 ft	15.9	10.6	4.86	7.29
85 ft	15.2	10.1	4.53	6.79
87 ft	14.5	9.63	4.22	6.33
89 ft	13.8	9.20	3.94	5.91
91 ft	13.2	8.80	3.69	5.53
93 ft	12.7	8.42	3.46	5.18
95 ft	12.1	8.07	3.24	4.86
97 ft	11.6	7.74	3.05	4.57
99 ft	11.2	7.43	2.86	4.30
101 ft	10.7	7.14	2.70	4.05
103 ft	10.3	6.87	2.54	3.82
105 ft	9.93	6.61	2.40	3.60
107 ft	9.56	6.36	2.27	3.40

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 65 ft span, a W36×800 carries a factored load of 25.9 kips per foot (LRFD) or an allowable load of 17.2 kips per foot (ASD). A live load of 10.1 kips per foot would deflect it span/360, which is 2.17 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.

W36×800 questions

What does W36×800 mean?

W means a wide flange shape. 36 is its nominal depth in inches (the actual depth is 42.6 in) and 800 is its weight in pounds per foot.

How much does a W36×800 weigh?

800 pounds per foot, so a 20 ft W36×800 weighs about 16,000 pounds.

How far can a W36×800 span?

It depends on the load. Braced along its length, it carries 248.3 kips per foot of factored load at 21 ft and 9.56 kips per foot at 107 ft; the load table has the spans in between. Floor beams are often 64 to 85 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.

Is a W36×800 a compact section?

Yes. Its flanges (b_f/2t_f = 2.10) and web (h/t_w = 13.5) are both compact for bending in 50 ksi steel.