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Wide Flange Steel I Beam: W8 × 21
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Glossary » Beams » Simply Supported » Uniformly Distributed Load » Three 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 three equal spans, we compute the displacement at the middle of the first and the third spans, and the maximum normal stress stress_max occuring at the second and third supports 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
  
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 8.71 × 10-6 12.5
30.0 1.24 × 10-5 17.8
40.0 1.66 × 10-5 23.8
50.0 2.07 × 10-5 29.7
60.0 2.49 × 10-5 35.6
70.0 2.90 × 10-5 41.6
80.0 3.32 × 10-5 47.5
90.0 3.73 × 10-5 53.4
100 4.15 × 10-5 59.4
200 8.30 × 10-5 119
300 1.24 × 10-4 178
400 1.66 × 10-4 238
500 2.07 × 10-4 297
600 2.49 × 10-4 356
700 2.90 × 10-4 416
800 3.32 × 10-4 475
900 3.73 × 10-4 534
1000 4.15 × 10-4 594
2000 8.30 × 10-4 1190
3000 0.00124 1780
4000 0.00166 2380
5000 0.00207 2970
6000 0.00249 3560
7000 0.00290 4160
8000 0.00332 4750
9000 0.00373 5340
1.00 × 104 0.00415 5940
2.00 × 104 0.00830 1.19 × 104
3.00 × 104 0.0124 1.78 × 104
4.00 × 104 0.0166 2.38 × 104
5.00 × 104 0.0207 2.97 × 104
6.00 × 104 0.0249 3.56 × 104
7.00 × 104 0.0290 4.16 × 104
8.00 × 104 0.0332 4.75 × 104
9.00 × 104 0.0373 5.34 × 104
1.00 × 105 0.0415 5.94 × 104
2.00 × 105 0.0830 1.19 × 105
3.00 × 105 0.124 1.78 × 105
4.00 × 105 0.166 2.38 × 105
5.00 × 105 0.207 2.97 × 105
5.00 × 105 0.208 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 6.72 × 10-5 34.6
30.0 9.61 × 10-5 49.5
40.0 1.28 × 10-4 66.0
50.0 1.60 × 10-4 82.5
60.0 1.92 × 10-4 99.0
70.0 2.24 × 10-4 115
80.0 2.56 × 10-4 132
90.0 2.88 × 10-4 148
100 3.20 × 10-4 165
200 6.40 × 10-4 330
300 9.61 × 10-4 495
400 0.00128 660
500 0.00160 825
600 0.00192 990
700 0.00224 1150
800 0.00256 1320
900 0.00288 1480
1000 0.00320 1650
2000 0.00640 3300
3000 0.00961 4950
4000 0.0128 6600
5000 0.0160 8250
6000 0.0192 9900
7000 0.0224 1.15 × 104
8000 0.0256 1.32 × 104
9000 0.0288 1.48 × 104
1.00 × 104 0.0320 1.65 × 104
2.00 × 104 0.0640 3.30 × 104
3.00 × 104 0.0961 4.95 × 104
4.00 × 104 0.128 6.60 × 104
5.00 × 104 0.160 8.25 × 104
6.00 × 104 0.192 9.90 × 104
7.00 × 104 0.224 1.15 × 105
8.00 × 104 0.256 1.32 × 105
9.00 × 104 0.288 1.48 × 105
1.00 × 105 0.320 1.65 × 105
1.80 × 105 0.577 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 0.00108 139
30.0 0.00154 198
40.0 0.00205 264
50.0 0.00256 330
60.0 0.00307 396
70.0 0.00359 462
80.0 0.00410 528
90.0 0.00461 594
100 0.00512 660
200 0.0102 1320
300 0.0154 1980
400 0.0205 2640
500 0.0256 3300
600 0.0307 3960
700 0.0359 4620
800 0.0410 5280
900 0.0461 5940
1000 0.0512 6600
2000 0.102 1.32 × 104
3000 0.154 1.98 × 104
4000 0.205 2.64 × 104
5000 0.256 3.30 × 104
6000 0.307 3.96 × 104
7000 0.359 4.62 × 104
8000 0.410 5.28 × 104
9000 0.461 5.94 × 104
1.00 × 104 0.512 6.60 × 104
2.00 × 104 1.02 1.32 × 105
3.00 × 104 1.54 1.98 × 105
4.00 × 104 2.05 2.64 × 105
4.50 × 104 2.31 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 0.00545 312
30.0 0.00778 445
40.0 0.0104 594
50.0 0.0130 742
60.0 0.0156 891
70.0 0.0182 1040
80.0 0.0207 1190
90.0 0.0233 1340
100 0.0259 1480
200 0.0519 2970
300 0.0778 4450
400 0.104 5940
500 0.130 7420
600 0.156 8910
700 0.182 1.04 × 104
800 0.207 1.19 × 104
900 0.233 1.34 × 104
1000 0.259 1.48 × 104
2000 0.519 2.97 × 104
3000 0.778 4.45 × 104
4000 1.04 5.94 × 104
5000 1.30 7.42 × 104
6000 1.56 8.91 × 104
7000 1.82 1.04 × 105
8000 2.07 1.19 × 105
9000 2.33 1.34 × 105
1.00 × 104 2.59 1.48 × 105
2.00 × 104 5.19 2.97 × 105
2.00 × 104 5.19 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 0.0172 554
30.0 0.0246 792
40.0 0.0328 1060
50.0 0.0410 1320
60.0 0.0492 1580
70.0 0.0574 1850
80.0 0.0656 2110
90.0 0.0738 2380
100 0.0820 2640
200 0.164 5280
300 0.246 7920
400 0.328 1.06 × 104
500 0.410 1.32 × 104
600 0.492 1.58 × 104
700 0.574 1.85 × 104
800 0.656 2.11 × 104
900 0.738 2.38 × 104
1000 0.820 2.64 × 104
2000 1.64 5.28 × 104
3000 2.46 7.92 × 104
4000 3.28 1.06 × 105
5000 4.10 1.32 × 105
6000 4.92 1.58 × 105
7000 5.74 1.85 × 105
8000 6.56 2.11 × 105
9000 7.38 2.38 × 105
1.00 × 104 8.20 2.64 × 105
1.13 × 104 9.23 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 0.0420 866
30.0 0.0600 1240
40.0 0.0801 1650
50.0 0.100 2060
60.0 0.120 2470
70.0 0.140 2890
80.0 0.160 3300
90.0 0.180 3710
100 0.200 4120
200 0.400 8250
300 0.600 1.24 × 104
400 0.801 1.65 × 104
500 1.00 2.06 × 104
600 1.20 2.47 × 104
700 1.40 2.89 × 104
800 1.60 3.30 × 104
900 1.80 3.71 × 104
1000 2.00 4.12 × 104
2000 4.00 8.25 × 104
3000 6.00 1.24 × 105
4000 8.01 1.65 × 105
4140 8.28 1.71 × 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 0.0871 1250
30.0 0.124 1780
40.0 0.166 2380
50.0 0.207 2970
60.0 0.249 3560
70.0 0.290 4160
80.0 0.332 4750
90.0 0.373 5340
100 0.415 5940
200 0.830 1.19 × 104
300 1.24 1.78 × 104
400 1.66 2.38 × 104
500 2.07 2.97 × 104
600 2.49 3.56 × 104
700 2.90 4.16 × 104
800 3.32 4.75 × 104
900 3.73 5.34 × 104
1000 4.15 5.94 × 104
2000 8.28 1.18 × 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 0.275 2220
30.0 0.393 3170
40.0 0.525 4220
50.0 0.656 5280
60.0 0.787 6330
70.0 0.918 7390
80.0 1.05 8440
90.0 1.18 9500
100 1.31 1.06 × 104
200 2.62 2.11 × 104
300 3.93 3.17 × 104
400 5.25 4.22 × 104
500 6.56 5.28 × 104
600 7.87 6.33 × 104
631 8.28 6.66 × 104
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 0.672 3460
30.0 0.961 4950
40.0 1.28 6600
50.0 1.60 8250
60.0 1.92 9900
70.0 2.24 1.15 × 104
80.0 2.56 1.32 × 104
90.0 2.88 1.48 × 104
100 3.20 1.65 × 104
200 6.40 3.30 × 104
259 8.28 4.27 × 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 1.39 4990
30.0 1.99 7130
40.0 2.66 9500
50.0 3.32 1.19 × 104
60.0 3.98 1.43 × 104
70.0 4.65 1.66 × 104
80.0 5.31 1.90 × 104
90.0 5.98 2.14 × 104
100 6.64 2.38 × 104
125 8.28 2.96 × 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 2.58 6790
30.0 3.69 9700
40.0 4.92 1.29 × 104
50.0 6.15 1.62 × 104
60.0 7.38 1.94 × 104
67.3 8.28 2.18 × 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 4.41 8870
30.0 6.30 1.27 × 104
39.5 8.28 1.67 × 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 7.06 1.12 × 104
24.6 8.28 1.32 × 104
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