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Glossary » Beams » Simply Supported » Uniformly Distributed Load » Four 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 four equal spans, we compute the displacement at the middle of the first and fourth spans, and the maximum normal stress stress_max occuring at the second and fourth 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 8.42 × 10-6 13.7
20.0 9.35 × 10-6 15.2
30.0 1.40 × 10-5 22.8
40.0 1.87 × 10-5 30.4
50.0 2.34 × 10-5 38.0
60.0 2.81 × 10-5 45.6
70.0 3.27 × 10-5 53.2
80.0 3.74 × 10-5 60.8
90.0 4.21 × 10-5 68.4
100 4.68 × 10-5 76.1
200 9.35 × 10-5 152
300 1.40 × 10-4 228
400 1.87 × 10-4 304
500 2.34 × 10-4 380
600 2.81 × 10-4 456
700 3.27 × 10-4 532
800 3.74 × 10-4 608
900 4.21 × 10-4 684
1000 4.68 × 10-4 761
2000 9.35 × 10-4 1520
3000 0.00140 2280
4000 0.00187 3040
5000 0.00234 3800
6000 0.00281 4560
7000 0.00327 5320
8000 0.00374 6080
9000 0.00421 6840
1.00 × 104 0.00468 7610
2.00 × 104 0.00935 1.52 × 104
3.00 × 104 0.0140 2.28 × 104
4.00 × 104 0.0187 3.04 × 104
5.00 × 104 0.0234 3.80 × 104
6.00 × 104 0.0281 4.56 × 104
7.00 × 104 0.0327 5.32 × 104
8.00 × 104 0.0374 6.08 × 104
9.00 × 104 0.0421 6.84 × 104
1.00 × 105 0.0468 7.61 × 104
2.00 × 105 0.0935 1.52 × 105
3.00 × 105 0.140 2.28 × 105
3.91 × 105 0.183 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 6.50 × 10-5 38.0
20.0 7.22 × 10-5 42.3
30.0 1.08 × 10-4 63.4
40.0 1.44 × 10-4 84.5
50.0 1.80 × 10-4 106
60.0 2.17 × 10-4 127
70.0 2.53 × 10-4 148
80.0 2.89 × 10-4 169
90.0 3.25 × 10-4 190
100 3.61 × 10-4 211
200 7.22 × 10-4 423
300 0.00108 634
400 0.00144 845
500 0.00180 1060
600 0.00217 1270
700 0.00253 1480
800 0.00289 1690
900 0.00325 1900
1000 0.00361 2110
2000 0.00722 4230
3000 0.0108 6340
4000 0.0144 8450
5000 0.0180 1.06 × 104
6000 0.0217 1.27 × 104
7000 0.0253 1.48 × 104
8000 0.0289 1.69 × 104
9000 0.0325 1.90 × 104
1.00 × 104 0.0361 2.11 × 104
2.00 × 104 0.0722 4.23 × 104
3.00 × 104 0.108 6.34 × 104
4.00 × 104 0.144 8.45 × 104
5.00 × 104 0.180 1.06 × 105
6.00 × 104 0.217 1.27 × 105
7.00 × 104 0.253 1.48 × 105
8.00 × 104 0.289 1.69 × 105
9.00 × 104 0.325 1.90 × 105
1.00 × 105 0.361 2.11 × 105
1.41 × 105 0.507 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 0.00104 152
20.0 0.00115 169
30.0 0.00173 254
40.0 0.00231 338
50.0 0.00289 423
60.0 0.00346 507
70.0 0.00404 592
80.0 0.00462 676
90.0 0.00520 761
100 0.00577 845
200 0.0115 1690
300 0.0173 2540
400 0.0231 3380
500 0.0289 4230
600 0.0346 5070
700 0.0404 5920
800 0.0462 6760
900 0.0520 7610
1000 0.0577 8450
2000 0.115 1.69 × 104
3000 0.173 2.54 × 104
4000 0.231 3.38 × 104
5000 0.289 4.23 × 104
6000 0.346 5.07 × 104
7000 0.404 5.92 × 104
8000 0.462 6.76 × 104
9000 0.520 7.61 × 104
1.00 × 104 0.577 8.45 × 104
2.00 × 104 1.15 1.69 × 105
3.00 × 104 1.73 2.54 × 105
3.52 × 104 2.03 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 0.00526 342
20.0 0.00585 380
30.0 0.00877 570
40.0 0.0117 761
50.0 0.0146 951
60.0 0.0175 1140
70.0 0.0205 1330
80.0 0.0234 1520
90.0 0.0263 1710
100 0.0292 1900
200 0.0585 3800
300 0.0877 5700
400 0.117 7610
500 0.146 9510
600 0.175 1.14 × 104
700 0.205 1.33 × 104
800 0.234 1.52 × 104
900 0.263 1.71 × 104
1000 0.292 1.90 × 104
2000 0.585 3.80 × 104
3000 0.877 5.70 × 104
4000 1.17 7.61 × 104
5000 1.46 9.51 × 104
6000 1.75 1.14 × 105
7000 2.05 1.33 × 105
8000 2.34 1.52 × 105
9000 2.63 1.71 × 105
1.00 × 104 2.92 1.90 × 105
1.56 × 104 4.57 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 0.0166 608
20.0 0.0185 676
30.0 0.0277 1010
40.0 0.0370 1350
50.0 0.0462 1690
60.0 0.0554 2030
70.0 0.0647 2370
80.0 0.0739 2700
90.0 0.0831 3040
100 0.0924 3380
200 0.185 6760
300 0.277 1.01 × 104
400 0.370 1.35 × 104
500 0.462 1.69 × 104
600 0.554 2.03 × 104
700 0.647 2.37 × 104
800 0.739 2.70 × 104
900 0.831 3.04 × 104
1000 0.924 3.38 × 104
2000 1.85 6.76 × 104
3000 2.77 1.01 × 105
4000 3.70 1.35 × 105
5000 4.62 1.69 × 105
6000 5.54 2.03 × 105
7000 6.47 2.37 × 105
8000 7.39 2.70 × 105
8790 8.12 2.97 × 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 0.0406 951
20.0 0.0451 1060
30.0 0.0677 1580
40.0 0.0902 2110
50.0 0.113 2640
60.0 0.135 3170
70.0 0.158 3700
80.0 0.180 4230
90.0 0.203 4750
100 0.226 5280
200 0.451 1.06 × 104
300 0.677 1.58 × 104
400 0.902 2.11 × 104
500 1.13 2.64 × 104
600 1.35 3.17 × 104
700 1.58 3.70 × 104
800 1.80 4.23 × 104
900 2.03 4.75 × 104
1000 2.26 5.28 × 104
2000 4.51 1.06 × 105
3000 6.77 1.58 × 105
3610 8.14 1.91 × 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 0.0842 1370
20.0 0.0935 1520
30.0 0.140 2280
40.0 0.187 3040
50.0 0.234 3800
60.0 0.281 4560
70.0 0.327 5320
80.0 0.374 6080
90.0 0.421 6840
100 0.468 7610
200 0.935 1.52 × 104
300 1.40 2.28 × 104
400 1.87 3.04 × 104
500 2.34 3.80 × 104
600 2.81 4.56 × 104
700 3.27 5.32 × 104
800 3.74 6.08 × 104
900 4.21 6.84 × 104
1000 4.68 7.61 × 104
1740 8.14 1.32 × 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 0.266 2430
20.0 0.296 2700
30.0 0.443 4060
40.0 0.591 5410
50.0 0.739 6760
60.0 0.887 8110
70.0 1.03 9460
80.0 1.18 1.08 × 104
90.0 1.33 1.22 × 104
100 1.48 1.35 × 104
200 2.96 2.70 × 104
300 4.43 4.06 × 104
400 5.91 5.41 × 104
500 7.39 6.76 × 104
551 8.14 7.45 × 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 0.650 3800
20.0 0.722 4230
30.0 1.08 6340
40.0 1.44 8450
50.0 1.80 1.06 × 104
60.0 2.17 1.27 × 104
70.0 2.53 1.48 × 104
80.0 2.89 1.69 × 104
90.0 3.25 1.90 × 104
100 3.61 2.11 × 104
200 7.22 4.23 × 104
226 8.14 4.77 × 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 1.35 5480
20.0 1.50 6080
30.0 2.25 9130
40.0 2.99 1.22 × 104
50.0 3.74 1.52 × 104
60.0 4.49 1.83 × 104
70.0 5.24 2.13 × 104
80.0 5.99 2.43 × 104
90.0 6.74 2.74 × 104
100 7.48 3.04 × 104
109 8.14 3.31 × 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 2.50 7450
20.0 2.77 8280
30.0 4.16 1.24 × 104
40.0 5.55 1.66 × 104
50.0 6.93 2.07 × 104
58.7 8.14 2.43 × 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 4.26 9730
20.0 4.73 1.08 × 104
30.0 7.10 1.62 × 104
34.4 8.14 1.86 × 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 6.82 1.23 × 104
20.0 7.58 1.37 × 104
21.5 8.14 1.47 × 104
Additional Information
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CNC Machining Design Guide

Optimize your designs, reduce machining time, and lower your costs.

Essentials of Manufacturing

Information, coverage of important developments and expert commentary in manufacturing.

Salary Expectation

8 things to know about the interview question "What's your salary expectation"?

Metal 3D Printing Design Guide

Direct Metal Laser Sintering (DMLS) 3D printing for parts with reduced cost and little waste.

more publications