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Glossary » Beams » Simply Supported » Uniformly Distributed Load » Four Equal Spans » Wide Flange Steel I Beam » W18 × 40
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 = 612 in4) for the W18 × 40 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
L = 125 ft
L = 150 ft
   
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 3.00 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 1.89 × 10-6 6.77
50.0 2.37 × 10-6 8.46
60.0 2.84 × 10-6 10.1
70.0 3.31 × 10-6 11.8
80.0 3.78 × 10-6 13.5
90.0 4.26 × 10-6 15.2
100 4.73 × 10-6 16.9
200 9.46 × 10-6 33.8
300 1.42 × 10-5 50.7
400 1.89 × 10-5 67.7
500 2.37 × 10-5 84.6
600 2.84 × 10-5 101
700 3.31 × 10-5 118
800 3.78 × 10-5 135
900 4.26 × 10-5 152
1000 4.73 × 10-5 169
2000 9.46 × 10-5 338
3000 1.42 × 10-4 507
4000 1.89 × 10-4 677
5000 2.37 × 10-4 846
6000 2.84 × 10-4 1010
7000 3.31 × 10-4 1180
8000 3.78 × 10-4 1350
9000 4.26 × 10-4 1520
1.00 × 104 4.73 × 10-4 1690
2.00 × 104 9.46 × 10-4 3380
3.00 × 104 0.00142 5070
4.00 × 104 0.00189 6770
5.00 × 104 0.00237 8460
6.00 × 104 0.00284 1.01 × 104
7.00 × 104 0.00331 1.18 × 104
8.00 × 104 0.00378 1.35 × 104
9.00 × 104 0.00426 1.52 × 104
1.00 × 105 0.00473 1.69 × 104
2.00 × 105 0.00946 3.38 × 104
3.00 × 105 0.0142 5.07 × 104
4.00 × 105 0.0189 6.77 × 104
5.00 × 105 0.0237 8.46 × 104
6.00 × 105 0.0284 1.01 × 105
7.00 × 105 0.0331 1.18 × 105
8.00 × 105 0.0378 1.35 × 105
9.00 × 105 0.0426 1.52 × 105
1.00 × 106 0.0473 1.69 × 105
1.76 × 106 0.0831 2.97 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 5.00 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 1.46 × 10-5 18.8
50.0 1.83 × 10-5 23.5
60.0 2.19 × 10-5 28.2
70.0 2.56 × 10-5 32.9
80.0 2.92 × 10-5 37.6
90.0 3.29 × 10-5 42.3
100 3.65 × 10-5 47.0
200 7.30 × 10-5 94.0
300 1.10 × 10-4 141
400 1.46 × 10-4 188
500 1.83 × 10-4 235
600 2.19 × 10-4 282
700 2.56 × 10-4 329
800 2.92 × 10-4 376
900 3.29 × 10-4 423
1000 3.65 × 10-4 470
2000 7.30 × 10-4 940
3000 0.00110 1410
4000 0.00146 1880
5000 0.00183 2350
6000 0.00219 2820
7000 0.00256 3290
8000 0.00292 3760
9000 0.00329 4230
1.00 × 104 0.00365 4700
2.00 × 104 0.00730 9400
3.00 × 104 0.0110 1.41 × 104
4.00 × 104 0.0146 1.88 × 104
5.00 × 104 0.0183 2.35 × 104
6.00 × 104 0.0219 2.82 × 104
7.00 × 104 0.0256 3.29 × 104
8.00 × 104 0.0292 3.76 × 104
9.00 × 104 0.0329 4.23 × 104
1.00 × 105 0.0365 4.70 × 104
2.00 × 105 0.0730 9.40 × 104
3.00 × 105 0.110 1.41 × 105
4.00 × 105 0.146 1.88 × 105
5.00 × 105 0.183 2.35 × 105
6.00 × 105 0.219 2.82 × 105
6.32 × 105 0.231 2.97 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 10.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 2.34 × 10-4 75.2
50.0 2.92 × 10-4 94.0
60.0 3.50 × 10-4 113
70.0 4.09 × 10-4 132
80.0 4.67 × 10-4 150
90.0 5.26 × 10-4 169
100 5.84 × 10-4 188
200 0.00117 376
300 0.00175 564
400 0.00234 752
500 0.00292 940
600 0.00350 1130
700 0.00409 1320
800 0.00467 1500
900 0.00526 1690
1000 0.00584 1880
2000 0.0117 3760
3000 0.0175 5640
4000 0.0234 7520
5000 0.0292 9400
6000 0.0350 1.13 × 104
7000 0.0409 1.32 × 104
8000 0.0467 1.50 × 104
9000 0.0526 1.69 × 104
1.00 × 104 0.0584 1.88 × 104
2.00 × 104 0.117 3.76 × 104
3.00 × 104 0.175 5.64 × 104
4.00 × 104 0.234 7.52 × 104
5.00 × 104 0.292 9.40 × 104
6.00 × 104 0.350 1.13 × 105
7.00 × 104 0.409 1.32 × 105
8.00 × 104 0.467 1.50 × 105
9.00 × 104 0.526 1.69 × 105
1.00 × 105 0.584 1.88 × 105
1.58 × 105 0.923 2.97 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 15.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.00118 169
50.0 0.00148 211
60.0 0.00177 254
70.0 0.00207 296
80.0 0.00237 338
90.0 0.00266 381
100 0.00296 423
200 0.00591 846
300 0.00887 1270
400 0.0118 1690
500 0.0148 2110
600 0.0177 2540
700 0.0207 2960
800 0.0237 3380
900 0.0266 3810
1000 0.0296 4230
2000 0.0591 8460
3000 0.0887 1.27 × 104
4000 0.118 1.69 × 104
5000 0.148 2.11 × 104
6000 0.177 2.54 × 104
7000 0.207 2.96 × 104
8000 0.237 3.38 × 104
9000 0.266 3.81 × 104
1.00 × 104 0.296 4.23 × 104
2.00 × 104 0.591 8.46 × 104
3.00 × 104 0.887 1.27 × 105
4.00 × 104 1.18 1.69 × 105
5.00 × 104 1.48 2.11 × 105
6.00 × 104 1.77 2.54 × 105
7.00 × 104 2.07 2.96 × 105
7.02 × 104 2.08 2.97 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 20.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.00374 301
50.0 0.00467 376
60.0 0.00561 451
70.0 0.00654 526
80.0 0.00748 601
90.0 0.00841 677
100 0.00934 752
200 0.0187 1500
300 0.0280 2260
400 0.0374 3010
500 0.0467 3760
600 0.0561 4510
700 0.0654 5260
800 0.0748 6010
900 0.0841 6770
1000 0.0934 7520
2000 0.187 1.50 × 104
3000 0.280 2.26 × 104
4000 0.374 3.01 × 104
5000 0.467 3.76 × 104
6000 0.561 4.51 × 104
7000 0.654 5.26 × 104
8000 0.748 6.01 × 104
9000 0.841 6.77 × 104
1.00 × 104 0.934 7.52 × 104
2.00 × 104 1.87 1.50 × 105
3.00 × 104 2.80 2.26 × 105
3.95 × 104 3.69 2.97 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 25.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.00913 470
50.0 0.0114 587
60.0 0.0137 705
70.0 0.0160 822
80.0 0.0183 940
90.0 0.0205 1060
100 0.0228 1170
200 0.0456 2350
300 0.0684 3520
400 0.0913 4700
500 0.114 5870
600 0.137 7050
700 0.160 8220
800 0.183 9400
900 0.205 1.06 × 104
1000 0.228 1.17 × 104
2000 0.456 2.35 × 104
3000 0.684 3.52 × 104
4000 0.913 4.70 × 104
5000 1.14 5.87 × 104
6000 1.37 7.05 × 104
7000 1.60 8.22 × 104
8000 1.83 9.40 × 104
9000 2.05 1.06 × 105
1.00 × 104 2.28 1.17 × 105
2.00 × 104 4.56 2.35 × 105
2.53 × 104 5.77 2.97 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 30.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.0189 677
50.0 0.0237 846
60.0 0.0284 1010
70.0 0.0331 1180
80.0 0.0378 1350
90.0 0.0426 1520
100 0.0473 1690
200 0.0946 3380
300 0.142 5070
400 0.189 6770
500 0.237 8460
600 0.284 1.01 × 104
700 0.331 1.18 × 104
800 0.378 1.35 × 104
900 0.426 1.52 × 104
1000 0.473 1.69 × 104
2000 0.946 3.38 × 104
3000 1.42 5.07 × 104
4000 1.89 6.77 × 104
5000 2.37 8.46 × 104
6000 2.84 1.01 × 105
7000 3.31 1.18 × 105
8000 3.78 1.35 × 105
9000 4.26 1.52 × 105
1.00 × 104 4.73 1.69 × 105
1.76 × 104 8.31 2.97 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 40.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.0598 1200
50.0 0.0748 1500
60.0 0.0897 1800
70.0 0.105 2110
80.0 0.120 2410
90.0 0.135 2710
100 0.150 3010
200 0.299 6010
300 0.449 9020
400 0.598 1.20 × 104
500 0.748 1.50 × 104
600 0.897 1.80 × 104
700 1.05 2.11 × 104
800 1.20 2.41 × 104
900 1.35 2.71 × 104
1000 1.50 3.01 × 104
2000 2.99 6.01 × 104
3000 4.49 9.02 × 104
4000 5.98 1.20 × 105
5000 7.48 1.50 × 105
6000 8.97 1.80 × 105
7000 10.5 2.11 × 105
8000 12.0 2.41 × 105
9000 13.5 2.71 × 105
9880 14.8 2.97 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 50.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.146 1880
50.0 0.183 2350
60.0 0.219 2820
70.0 0.256 3290
80.0 0.292 3760
90.0 0.329 4230
100 0.365 4700
200 0.730 9400
300 1.10 1.41 × 104
400 1.46 1.88 × 104
500 1.83 2.35 × 104
600 2.19 2.82 × 104
700 2.56 3.29 × 104
800 2.92 3.76 × 104
900 3.29 4.23 × 104
1000 3.65 4.70 × 104
2000 7.30 9.40 × 104
3000 11.0 1.41 × 105
4000 14.6 1.88 × 105
4900 17.9 2.30 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 60.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.303 2710
50.0 0.378 3380
60.0 0.454 4060
70.0 0.530 4740
80.0 0.606 5410
90.0 0.681 6090
100 0.757 6770
200 1.51 1.35 × 104
300 2.27 2.03 × 104
400 3.03 2.71 × 104
500 3.78 3.38 × 104
600 4.54 4.06 × 104
700 5.30 4.74 × 104
800 6.06 5.41 × 104
900 6.81 6.09 × 104
1000 7.57 6.77 × 104
2000 15.1 1.35 × 105
2360 17.9 1.60 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 70.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.561 3680
50.0 0.701 4600
60.0 0.841 5530
70.0 0.982 6450
80.0 1.12 7370
90.0 1.26 8290
100 1.40 9210
200 2.80 1.84 × 104
300 4.21 2.76 × 104
400 5.61 3.68 × 104
500 7.01 4.60 × 104
600 8.41 5.53 × 104
700 9.82 6.45 × 104
800 11.2 7.37 × 104
900 12.6 8.29 × 104
1000 14.0 9.21 × 104
1280 17.9 1.18 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 80.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.957 4810
50.0 1.20 6010
60.0 1.44 7220
70.0 1.67 8420
80.0 1.91 9620
90.0 2.15 1.08 × 104
100 2.39 1.20 × 104
200 4.78 2.41 × 104
300 7.18 3.61 × 104
400 9.57 4.81 × 104
500 12.0 6.01 × 104
600 14.4 7.22 × 104
700 16.7 8.42 × 104
748 17.9 9.00 × 104
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 90.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 1.53 6090
50.0 1.92 7610
60.0 2.30 9130
70.0 2.68 1.07 × 104
80.0 3.07 1.22 × 104
90.0 3.45 1.37 × 104
100 3.83 1.52 × 104
200 7.66 3.04 × 104
300 11.5 4.57 × 104
400 15.3 6.09 × 104
467 17.9 7.11 × 104
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 100 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 2.34 7520
50.0 2.92 9400
60.0 3.50 1.13 × 104
70.0 4.09 1.32 × 104
80.0 4.67 1.50 × 104
90.0 5.26 1.69 × 104
100 5.84 1.88 × 104
200 11.7 3.76 × 104
300 17.5 5.64 × 104
306 17.9 5.76 × 104
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 125 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 5.70 1.17 × 104
50.0 7.13 1.47 × 104
60.0 8.56 1.76 × 104
70.0 9.98 2.06 × 104
80.0 11.4 2.35 × 104
90.0 12.8 2.64 × 104
100 14.3 2.94 × 104
126 17.9 3.69 × 104
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 150 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 11.8 1.69 × 104
50.0 14.8 2.11 × 104
60.0 17.7 2.54 × 104
60.5 17.9 2.56 × 104
Additional Information
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Essentials of Manufacturing

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

CNC Machining Design Guide

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

Negotiate Your Salary

Learn the best principles to negotiate the salary you deserve!

Mechanical Engineers Outlook

Guide for those interested in becoming a mechanical engineer. Includes qualifications, pay, and job duties.

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