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Wide Flange Steel I Beam: W8 × 21
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Glossary » Beams » Simply Supported » Uniformly Distributed Load » Two Equal Spans » Wide Flange Steel I Beam » W8 × 21
Wide Flange Steel I Beam | Single Span | Two Equal Spans | Three Equal Spans | Four Equal Spans

For a simply supported beam in two equal spans, we compute the displacement at the middle of each span w_mid and the maximum normal stress stress_max occuring at the center support of the beam.
The tabulated data listed in this page are calculated based on the area moment of inertia (Ixx = 75.3 in4) for the W8 × 21 Wide Flange Steel I Beam and the typical Young's modulus (E = 3.046 × 107 psi) of steels. Note that the typical yielding stress Yield of steels can range from 1.015 × 104 to 2.970 × 105 psi. The purpose of this page is to give a rough estimation of the load-bearing capacity of this particular beam, rather than a guideline for designing actual building structures. Please check your local building codes for regulatory requirements.

Note: The weight of the beam itself is not included in the calculation.
L = 3 ft
L = 5 ft
L = 10 ft
L = 15 ft
L = 20 ft
L = 25 ft
L = 30 ft
L = 40 ft
L = 50 ft
L = 60 ft
L = 70 ft
L = 80 ft
L = 90 ft
L = 100 ft
   
Steel I Beam: W8 × 21 (Wide Flange 8 inch tall × 21 lbf/ft)
L = 3.00 ft
P (lbf/ft) w_max (in) stress_max (psi)
21.0 6.67 × 10-6 15.6
30.0 9.54 × 10-6 22.3
40.0 1.27 × 10-5 29.7
50.0 1.59 × 10-5 37.1
60.0 1.91 × 10-5 44.5
70.0 2.22 × 10-5 52.0
80.0 2.54 × 10-5 59.4
90.0 2.86 × 10-5 66.8
100 3.18 × 10-5 74.2
200 6.36 × 10-5 148
300 9.54 × 10-5 223
400 1.27 × 10-4 297
500 1.59 × 10-4 371
600 1.91 × 10-4 445
700 2.22 × 10-4 520
800 2.54 × 10-4 594
900 2.86 × 10-4 668
1000 3.18 × 10-4 742
2000 6.36 × 10-4 1480
3000 9.54 × 10-4 2230
4000 0.00127 2970
5000 0.00159 3710
6000 0.00191 4450
7000 0.00222 5200
8000 0.00254 5940
9000 0.00286 6680
1.00 × 104 0.00318 7420
2.00 × 104 0.00636 1.48 × 104
3.00 × 104 0.00954 2.23 × 104
4.00 × 104 0.0127 2.97 × 104
5.00 × 104 0.0159 3.71 × 104
6.00 × 104 0.0191 4.45 × 104
7.00 × 104 0.0222 5.20 × 104
8.00 × 104 0.0254 5.94 × 104
9.00 × 104 0.0286 6.68 × 104
1.00 × 105 0.0318 7.42 × 104
2.00 × 105 0.0636 1.48 × 105
3.00 × 105 0.0954 2.23 × 105
4.00 × 105 0.127 2.97 × 105
4.00 × 105 0.127 2.97 × 105
Steel I Beam: W8 × 21 (Wide Flange 8 inch tall × 21 lbf/ft)
L = 5.00 ft
P (lbf/ft) w_max (in) stress_max (psi)
21.0 5.15 × 10-5 43.3
30.0 7.36 × 10-5 61.9
40.0 9.81 × 10-5 82.5
50.0 1.23 × 10-4 103
60.0 1.47 × 10-4 124
70.0 1.72 × 10-4 144
80.0 1.96 × 10-4 165
90.0 2.21 × 10-4 186
100 2.45 × 10-4 206
200 4.91 × 10-4 412
300 7.36 × 10-4 619
400 9.81 × 10-4 825
500 0.00123 1030
600 0.00147 1240
700 0.00172 1440
800 0.00196 1650
900 0.00221 1860
1000 0.00245 2060
2000 0.00491 4120
3000 0.00736 6190
4000 0.00981 8250
5000 0.0123 1.03 × 104
6000 0.0147 1.24 × 104
7000 0.0172 1.44 × 104
8000 0.0196 1.65 × 104
9000 0.0221 1.86 × 104
1.00 × 104 0.0245 2.06 × 104
2.00 × 104 0.0491 4.12 × 104
3.00 × 104 0.0736 6.19 × 104
4.00 × 104 0.0981 8.25 × 104
5.00 × 104 0.123 1.03 × 105
6.00 × 104 0.147 1.24 × 105
7.00 × 104 0.172 1.44 × 105
8.00 × 104 0.196 1.65 × 105
9.00 × 104 0.221 1.86 × 105
1.00 × 105 0.245 2.06 × 105
1.44 × 105 0.353 2.97 × 105
Steel I Beam: W8 × 21 (Wide Flange 8 inch tall × 21 lbf/ft)
L = 10.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
21.0 8.24 × 10-4 173
30.0 0.00118 247
40.0 0.00157 330
50.0 0.00196 412
60.0 0.00235 495
70.0 0.00275 577
80.0 0.00314 660
90.0 0.00353 742
100 0.00392 825
200 0.00785 1650
300 0.0118 2470
400 0.0157 3300
500 0.0196 4120
600 0.0235 4950
700 0.0275 5770
800 0.0314 6600
900 0.0353 7420
1000 0.0392 8250
2000 0.0785 1.65 × 104
3000 0.118 2.47 × 104
4000 0.157 3.30 × 104
5000 0.196 4.12 × 104
6000 0.235 4.95 × 104
7000 0.275 5.77 × 104
8000 0.314 6.60 × 104
9000 0.353 7.42 × 104
1.00 × 104 0.392 8.25 × 104
2.00 × 104 0.785 1.65 × 105
3.00 × 104 1.18 2.47 × 105
3.60 × 104 1.41 2.97 × 105
Steel I Beam: W8 × 21 (Wide Flange 8 inch tall × 21 lbf/ft)
L = 15.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
21.0 0.00417 390
30.0 0.00596 557
40.0 0.00795 742
50.0 0.00993 928
60.0 0.0119 1110
70.0 0.0139 1300
80.0 0.0159 1480
90.0 0.0179 1670
100 0.0199 1860
200 0.0397 3710
300 0.0596 5570
400 0.0795 7420
500 0.0993 9280
600 0.119 1.11 × 104
700 0.139 1.30 × 104
800 0.159 1.48 × 104
900 0.179 1.67 × 104
1000 0.199 1.86 × 104
2000 0.397 3.71 × 104
3000 0.596 5.57 × 104
4000 0.795 7.42 × 104
5000 0.993 9.28 × 104
6000 1.19 1.11 × 105
7000 1.39 1.30 × 105
8000 1.59 1.48 × 105
9000 1.79 1.67 × 105
1.00 × 104 1.99 1.86 × 105
1.60 × 104 3.18 2.97 × 105
Steel I Beam: W8 × 21 (Wide Flange 8 inch tall × 21 lbf/ft)
L = 20.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
21.0 0.0132 693
30.0 0.0188 990
40.0 0.0251 1320
50.0 0.0314 1650
60.0 0.0377 1980
70.0 0.0440 2310
80.0 0.0502 2640
90.0 0.0565 2970
100 0.0628 3300
200 0.126 6600
300 0.188 9900
400 0.251 1.32 × 104
500 0.314 1.65 × 104
600 0.377 1.98 × 104
700 0.440 2.31 × 104
800 0.502 2.64 × 104
900 0.565 2.97 × 104
1000 0.628 3.30 × 104
2000 1.26 6.60 × 104
3000 1.88 9.90 × 104
4000 2.51 1.32 × 105
5000 3.14 1.65 × 105
6000 3.77 1.98 × 105
7000 4.40 2.31 × 105
8000 5.02 2.64 × 105
9000 5.65 2.97 × 105
9000 5.65 2.97 × 105
Steel I Beam: W8 × 21 (Wide Flange 8 inch tall × 21 lbf/ft)
L = 25.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
21.0 0.0322 1080
30.0 0.0460 1550
40.0 0.0613 2060
50.0 0.0766 2580
60.0 0.0920 3090
70.0 0.107 3610
80.0 0.123 4120
90.0 0.138 4640
100 0.153 5150
200 0.307 1.03 × 104
300 0.460 1.55 × 104
400 0.613 2.06 × 104
500 0.766 2.58 × 104
600 0.920 3.09 × 104
700 1.07 3.61 × 104
800 1.23 4.12 × 104
900 1.38 4.64 × 104
1000 1.53 5.15 × 104
2000 3.07 1.03 × 105
3000 4.60 1.55 × 105
4000 6.13 2.06 × 105
5000 7.66 2.58 × 105
5760 8.83 2.97 × 105
Steel I Beam: W8 × 21 (Wide Flange 8 inch tall × 21 lbf/ft)
L = 30.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
21.0 0.0667 1560
30.0 0.0954 2230
40.0 0.127 2970
50.0 0.159 3710
60.0 0.191 4450
70.0 0.222 5200
80.0 0.254 5940
90.0 0.286 6680
100 0.318 7420
200 0.636 1.48 × 104
300 0.954 2.23 × 104
400 1.27 2.97 × 104
500 1.59 3.71 × 104
600 1.91 4.45 × 104
700 2.22 5.20 × 104
800 2.54 5.94 × 104
900 2.86 6.68 × 104
1000 3.18 7.42 × 104
2000 6.36 1.48 × 105
2600 8.28 1.93 × 105
Steel I Beam: W8 × 21 (Wide Flange 8 inch tall × 21 lbf/ft)
L = 40.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
21.0 0.211 2770
30.0 0.301 3960
40.0 0.402 5280
50.0 0.502 6600
60.0 0.603 7920
70.0 0.703 9240
80.0 0.804 1.06 × 104
90.0 0.904 1.19 × 104
100 1.00 1.32 × 104
200 2.01 2.64 × 104
300 3.01 3.96 × 104
400 4.02 5.28 × 104
500 5.02 6.60 × 104
600 6.03 7.92 × 104
700 7.03 9.24 × 104
800 8.04 1.06 × 105
824 8.28 1.09 × 105
Steel I Beam: W8 × 21 (Wide Flange 8 inch tall × 21 lbf/ft)
L = 50.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
21.0 0.515 4330
30.0 0.736 6190
40.0 0.981 8250
50.0 1.23 1.03 × 104
60.0 1.47 1.24 × 104
70.0 1.72 1.44 × 104
80.0 1.96 1.65 × 104
90.0 2.21 1.86 × 104
100 2.45 2.06 × 104
200 4.91 4.12 × 104
300 7.36 6.19 × 104
338 8.28 6.96 × 104
Steel I Beam: W8 × 21 (Wide Flange 8 inch tall × 21 lbf/ft)
L = 60.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
21.0 1.07 6230
30.0 1.53 8910
40.0 2.03 1.19 × 104
50.0 2.54 1.48 × 104
60.0 3.05 1.78 × 104
70.0 3.56 2.08 × 104
80.0 4.07 2.38 × 104
90.0 4.58 2.67 × 104
100 5.09 2.97 × 104
163 8.28 4.83 × 104
Steel I Beam: W8 × 21 (Wide Flange 8 inch tall × 21 lbf/ft)
L = 70.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
21.0 1.98 8490
30.0 2.83 1.21 × 104
40.0 3.77 1.62 × 104
50.0 4.71 2.02 × 104
60.0 5.65 2.42 × 104
70.0 6.60 2.83 × 104
80.0 7.54 3.23 × 104
87.9 8.28 3.55 × 104
Steel I Beam: W8 × 21 (Wide Flange 8 inch tall × 21 lbf/ft)
L = 80.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
21.0 3.38 1.11 × 104
30.0 4.82 1.58 × 104
40.0 6.43 2.11 × 104
50.0 8.04 2.64 × 104
51.5 8.28 2.72 × 104
Steel I Beam: W8 × 21 (Wide Flange 8 inch tall × 21 lbf/ft)
L = 90.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
21.0 5.41 1.40 × 104
30.0 7.72 2.00 × 104
32.2 8.28 2.15 × 104
Steel I Beam: W8 × 21 (Wide Flange 8 inch tall × 21 lbf/ft)
L = 100 ft
P (lbf/ft) w_max (in) stress_max (psi)
21.0 8.24 1.73 × 104
21.1 8.28 1.74 × 104
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