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Wide Flange Steel I Beam: W8 × 18
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Glossary » Beams » Simply Supported » Uniformly Distributed Load » Three Equal Spans » Wide Flange Steel I Beam » W8 × 18
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 = 61.9 in4) for the W8 × 18 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 × 18 (Wide Flange 8 inch tall × 18 lbf/ft)
L = 3.00 ft
P (lbf/ft) w_max (in) stress_max (psi)
18.0 9.09 × 10-6 12.8
20.0 1.01 × 10-5 14.2
30.0 1.51 × 10-5 21.3
40.0 2.02 × 10-5 28.4
50.0 2.52 × 10-5 35.5
60.0 3.03 × 10-5 42.6
70.0 3.53 × 10-5 49.7
80.0 4.04 × 10-5 56.8
90.0 4.54 × 10-5 63.9
100 5.05 × 10-5 71.0
200 1.01 × 10-4 142
300 1.51 × 10-4 213
400 2.02 × 10-4 284
500 2.52 × 10-4 355
600 3.03 × 10-4 426
700 3.53 × 10-4 497
800 4.04 × 10-4 568
900 4.54 × 10-4 639
1000 5.05 × 10-4 710
2000 0.00101 1420
3000 0.00151 2130
4000 0.00202 2840
5000 0.00252 3550
6000 0.00303 4260
7000 0.00353 4970
8000 0.00404 5680
9000 0.00454 6390
1.00 × 104 0.00505 7100
2.00 × 104 0.0101 1.42 × 104
3.00 × 104 0.0151 2.13 × 104
4.00 × 104 0.0202 2.84 × 104
5.00 × 104 0.0252 3.55 × 104
6.00 × 104 0.0303 4.26 × 104
7.00 × 104 0.0353 4.97 × 104
8.00 × 104 0.0404 5.68 × 104
9.00 × 104 0.0454 6.39 × 104
1.00 × 105 0.0505 7.10 × 104
2.00 × 105 0.101 1.42 × 105
3.00 × 105 0.151 2.13 × 105
4.00 × 105 0.202 2.84 × 105
4.18 × 105 0.211 2.97 × 105
Steel I Beam: W8 × 18 (Wide Flange 8 inch tall × 18 lbf/ft)
L = 5.00 ft
P (lbf/ft) w_max (in) stress_max (psi)
18.0 7.01 × 10-5 35.5
20.0 7.79 × 10-5 39.5
30.0 1.17 × 10-4 59.2
40.0 1.56 × 10-4 78.9
50.0 1.95 × 10-4 98.6
60.0 2.34 × 10-4 118
70.0 2.73 × 10-4 138
80.0 3.12 × 10-4 158
90.0 3.51 × 10-4 178
100 3.90 × 10-4 197
200 7.79 × 10-4 395
300 0.00117 592
400 0.00156 789
500 0.00195 986
600 0.00234 1180
700 0.00273 1380
800 0.00312 1580
900 0.00351 1780
1000 0.00390 1970
2000 0.00779 3950
3000 0.0117 5920
4000 0.0156 7890
5000 0.0195 9860
6000 0.0234 1.18 × 104
7000 0.0273 1.38 × 104
8000 0.0312 1.58 × 104
9000 0.0351 1.78 × 104
1.00 × 104 0.0390 1.97 × 104
2.00 × 104 0.0779 3.95 × 104
3.00 × 104 0.117 5.92 × 104
4.00 × 104 0.156 7.89 × 104
5.00 × 104 0.195 9.86 × 104
6.00 × 104 0.234 1.18 × 105
7.00 × 104 0.273 1.38 × 105
8.00 × 104 0.312 1.58 × 105
9.00 × 104 0.351 1.78 × 105
1.00 × 105 0.390 1.97 × 105
1.51 × 105 0.587 2.97 × 105
Steel I Beam: W8 × 18 (Wide Flange 8 inch tall × 18 lbf/ft)
L = 10.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
18.0 0.00112 142
20.0 0.00125 158
30.0 0.00187 237
40.0 0.00249 316
50.0 0.00312 395
60.0 0.00374 473
70.0 0.00436 552
80.0 0.00499 631
90.0 0.00561 710
100 0.00623 789
200 0.0125 1580
300 0.0187 2370
400 0.0249 3160
500 0.0312 3950
600 0.0374 4730
700 0.0436 5520
800 0.0499 6310
900 0.0561 7100
1000 0.0623 7890
2000 0.125 1.58 × 104
3000 0.187 2.37 × 104
4000 0.249 3.16 × 104
5000 0.312 3.95 × 104
6000 0.374 4.73 × 104
7000 0.436 5.52 × 104
8000 0.499 6.31 × 104
9000 0.561 7.10 × 104
1.00 × 104 0.623 7.89 × 104
2.00 × 104 1.25 1.58 × 105
3.00 × 104 1.87 2.37 × 105
3.76 × 104 2.35 2.97 × 105
Steel I Beam: W8 × 18 (Wide Flange 8 inch tall × 18 lbf/ft)
L = 15.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
18.0 0.00568 320
20.0 0.00631 355
30.0 0.00947 533
40.0 0.0126 710
50.0 0.0158 888
60.0 0.0189 1070
70.0 0.0221 1240
80.0 0.0252 1420
90.0 0.0284 1600
100 0.0316 1780
200 0.0631 3550
300 0.0947 5330
400 0.126 7100
500 0.158 8880
600 0.189 1.07 × 104
700 0.221 1.24 × 104
800 0.252 1.42 × 104
900 0.284 1.60 × 104
1000 0.316 1.78 × 104
2000 0.631 3.55 × 104
3000 0.947 5.33 × 104
4000 1.26 7.10 × 104
5000 1.58 8.88 × 104
6000 1.89 1.07 × 105
7000 2.21 1.24 × 105
8000 2.52 1.42 × 105
9000 2.84 1.60 × 105
1.00 × 104 3.16 1.78 × 105
1.67 × 104 5.28 2.97 × 105
Steel I Beam: W8 × 18 (Wide Flange 8 inch tall × 18 lbf/ft)
L = 20.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
18.0 0.0179 568
20.0 0.0199 631
30.0 0.0299 947
40.0 0.0399 1260
50.0 0.0499 1580
60.0 0.0598 1890
70.0 0.0698 2210
80.0 0.0798 2520
90.0 0.0897 2840
100 0.0997 3160
200 0.199 6310
300 0.299 9470
400 0.399 1.26 × 104
500 0.499 1.58 × 104
600 0.598 1.89 × 104
700 0.698 2.21 × 104
800 0.798 2.52 × 104
900 0.897 2.84 × 104
1000 0.997 3.16 × 104
2000 1.99 6.31 × 104
3000 2.99 9.47 × 104
4000 3.99 1.26 × 105
5000 4.99 1.58 × 105
6000 5.98 1.89 × 105
7000 6.98 2.21 × 105
8000 7.98 2.52 × 105
8160 8.14 2.58 × 105
Steel I Beam: W8 × 18 (Wide Flange 8 inch tall × 18 lbf/ft)
L = 25.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
18.0 0.0438 888
20.0 0.0487 986
30.0 0.0730 1480
40.0 0.0974 1970
50.0 0.122 2470
60.0 0.146 2960
70.0 0.170 3450
80.0 0.195 3950
90.0 0.219 4440
100 0.243 4930
200 0.487 9860
300 0.730 1.48 × 104
400 0.974 1.97 × 104
500 1.22 2.47 × 104
600 1.46 2.96 × 104
700 1.70 3.45 × 104
800 1.95 3.95 × 104
900 2.19 4.44 × 104
1000 2.43 4.93 × 104
2000 4.87 9.86 × 104
3000 7.30 1.48 × 105
3340 8.14 1.65 × 105
Steel I Beam: W8 × 18 (Wide Flange 8 inch tall × 18 lbf/ft)
L = 30.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
18.0 0.0909 1280
20.0 0.101 1420
30.0 0.151 2130
40.0 0.202 2840
50.0 0.252 3550
60.0 0.303 4260
70.0 0.353 4970
80.0 0.404 5680
90.0 0.454 6390
100 0.505 7100
200 1.01 1.42 × 104
300 1.51 2.13 × 104
400 2.02 2.84 × 104
500 2.52 3.55 × 104
600 3.03 4.26 × 104
700 3.53 4.97 × 104
800 4.04 5.68 × 104
900 4.54 6.39 × 104
1000 5.05 7.10 × 104
1610 8.14 1.15 × 105
Steel I Beam: W8 × 18 (Wide Flange 8 inch tall × 18 lbf/ft)
L = 40.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
18.0 0.287 2270
20.0 0.319 2520
30.0 0.479 3790
40.0 0.638 5050
50.0 0.798 6310
60.0 0.957 7570
70.0 1.12 8840
80.0 1.28 1.01 × 104
90.0 1.44 1.14 × 104
100 1.60 1.26 × 104
200 3.19 2.52 × 104
300 4.79 3.79 × 104
400 6.38 5.05 × 104
500 7.98 6.31 × 104
510 8.14 6.44 × 104
Steel I Beam: W8 × 18 (Wide Flange 8 inch tall × 18 lbf/ft)
L = 50.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
18.0 0.701 3550
20.0 0.779 3950
30.0 1.17 5920
40.0 1.56 7890
50.0 1.95 9860
60.0 2.34 1.18 × 104
70.0 2.73 1.38 × 104
80.0 3.12 1.58 × 104
90.0 3.51 1.78 × 104
100 3.90 1.97 × 104
200 7.79 3.95 × 104
209 8.14 4.12 × 104
Steel I Beam: W8 × 18 (Wide Flange 8 inch tall × 18 lbf/ft)
L = 60.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
18.0 1.45 5110
20.0 1.62 5680
30.0 2.42 8520
40.0 3.23 1.14 × 104
50.0 4.04 1.42 × 104
60.0 4.85 1.70 × 104
70.0 5.65 1.99 × 104
80.0 6.46 2.27 × 104
90.0 7.27 2.56 × 104
100 8.08 2.84 × 104
101 8.14 2.86 × 104
Steel I Beam: W8 × 18 (Wide Flange 8 inch tall × 18 lbf/ft)
L = 70.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
18.0 2.69 6960
20.0 2.99 7730
30.0 4.49 1.16 × 104
40.0 5.99 1.55 × 104
50.0 7.48 1.93 × 104
54.4 8.14 2.10 × 104
Steel I Beam: W8 × 18 (Wide Flange 8 inch tall × 18 lbf/ft)
L = 80.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
18.0 4.60 9090
20.0 5.11 1.01 × 104
30.0 7.66 1.51 × 104
31.9 8.14 1.61 × 104
Steel I Beam: W8 × 18 (Wide Flange 8 inch tall × 18 lbf/ft)
L = 90.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
18.0 7.36 1.15 × 104
19.9 8.14 1.27 × 104
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