3D Scanners

A white paper to assist in the evaluation of 3D scanning hardware solutions.

STEM Career Outlook

Wages, employment opportunities, and growth projections for STEM jobs.

Negotiate Your Salary

Learn the best principles to negotiate the salary you deserve!

CNC Machining Design Guide

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

more free publications

Materials

Design

Processes

Units

Formulas

Math
Glossary » Beams » Simply Supported » Uniformly Distributed Load » Three Equal Spans » Wide Flange Steel I Beam » W21 × 68
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 = 1480 in4) for the W21 × 68 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: W21 × 68 (Wide Flange 21 inch tall × 68 lbf/ft)
L = 3.00 ft
P (lbf/ft) w_max (in) stress_max (psi)
68.0 1.44 × 10-6 5.24
70.0 1.48 × 10-6 5.40
80.0 1.69 × 10-6 6.17
90.0 1.90 × 10-6 6.94
100 2.11 × 10-6 7.71
200 4.22 × 10-6 15.4
300 6.33 × 10-6 23.1
400 8.45 × 10-6 30.8
500 1.06 × 10-5 38.5
600 1.27 × 10-5 46.3
700 1.48 × 10-5 54.0
800 1.69 × 10-5 61.7
900 1.90 × 10-5 69.4
1000 2.11 × 10-5 77.1
2000 4.22 × 10-5 154
3000 6.33 × 10-5 231
4000 8.45 × 10-5 308
5000 1.06 × 10-4 385
6000 1.27 × 10-4 463
7000 1.48 × 10-4 540
8000 1.69 × 10-4 617
9000 1.90 × 10-4 694
1.00 × 104 2.11 × 10-4 771
2.00 × 104 4.22 × 10-4 1540
3.00 × 104 6.33 × 10-4 2310
4.00 × 104 8.45 × 10-4 3080
5.00 × 104 0.00106 3850
6.00 × 104 0.00127 4630
7.00 × 104 0.00148 5400
8.00 × 104 0.00169 6170
9.00 × 104 0.00190 6940
1.00 × 105 0.00211 7710
2.00 × 105 0.00422 1.54 × 104
3.00 × 105 0.00633 2.31 × 104
4.00 × 105 0.00845 3.08 × 104
5.00 × 105 0.0106 3.85 × 104
6.00 × 105 0.0127 4.63 × 104
7.00 × 105 0.0148 5.40 × 104
8.00 × 105 0.0169 6.17 × 104
9.00 × 105 0.0190 6.94 × 104
1.00 × 106 0.0211 7.71 × 104
2.00 × 106 0.0422 1.54 × 105
3.00 × 106 0.0633 2.31 × 105
3.85 × 106 0.0813 2.97 × 105
Steel I Beam: W21 × 68 (Wide Flange 21 inch tall × 68 lbf/ft)
L = 5.00 ft
P (lbf/ft) w_max (in) stress_max (psi)
68.0 1.11 × 10-5 14.6
70.0 1.14 × 10-5 15.0
80.0 1.30 × 10-5 17.1
90.0 1.47 × 10-5 19.3
100 1.63 × 10-5 21.4
200 3.26 × 10-5 42.8
300 4.89 × 10-5 64.2
400 6.52 × 10-5 85.7
500 8.15 × 10-5 107
600 9.78 × 10-5 128
700 1.14 × 10-4 150
800 1.30 × 10-4 171
900 1.47 × 10-4 193
1000 1.63 × 10-4 214
2000 3.26 × 10-4 428
3000 4.89 × 10-4 642
4000 6.52 × 10-4 857
5000 8.15 × 10-4 1070
6000 9.78 × 10-4 1280
7000 0.00114 1500
8000 0.00130 1710
9000 0.00147 1930
1.00 × 104 0.00163 2140
2.00 × 104 0.00326 4280
3.00 × 104 0.00489 6420
4.00 × 104 0.00652 8570
5.00 × 104 0.00815 1.07 × 104
6.00 × 104 0.00978 1.28 × 104
7.00 × 104 0.0114 1.50 × 104
8.00 × 104 0.0130 1.71 × 104
9.00 × 104 0.0147 1.93 × 104
1.00 × 105 0.0163 2.14 × 104
2.00 × 105 0.0326 4.28 × 104
3.00 × 105 0.0489 6.42 × 104
4.00 × 105 0.0652 8.57 × 104
5.00 × 105 0.0815 1.07 × 105
6.00 × 105 0.0978 1.28 × 105
7.00 × 105 0.114 1.50 × 105
8.00 × 105 0.130 1.71 × 105
9.00 × 105 0.147 1.93 × 105
1.00 × 106 0.163 2.14 × 105
1.39 × 106 0.226 2.97 × 105
Steel I Beam: W21 × 68 (Wide Flange 21 inch tall × 68 lbf/ft)
L = 10.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
68.0 1.77 × 10-4 58.3
70.0 1.82 × 10-4 60.0
80.0 2.09 × 10-4 68.5
90.0 2.35 × 10-4 77.1
100 2.61 × 10-4 85.7
200 5.21 × 10-4 171
300 7.82 × 10-4 257
400 0.00104 343
500 0.00130 428
600 0.00156 514
700 0.00182 600
800 0.00209 685
900 0.00235 771
1000 0.00261 857
2000 0.00521 1710
3000 0.00782 2570
4000 0.0104 3430
5000 0.0130 4280
6000 0.0156 5140
7000 0.0182 6000
8000 0.0209 6850
9000 0.0235 7710
1.00 × 104 0.0261 8570
2.00 × 104 0.0521 1.71 × 104
3.00 × 104 0.0782 2.57 × 104
4.00 × 104 0.104 3.43 × 104
5.00 × 104 0.130 4.28 × 104
6.00 × 104 0.156 5.14 × 104
7.00 × 104 0.182 6.00 × 104
8.00 × 104 0.209 6.85 × 104
9.00 × 104 0.235 7.71 × 104
1.00 × 105 0.261 8.57 × 104
2.00 × 105 0.521 1.71 × 105
3.00 × 105 0.782 2.57 × 105
3.47 × 105 0.904 2.97 × 105
Steel I Beam: W21 × 68 (Wide Flange 21 inch tall × 68 lbf/ft)
L = 15.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
68.0 8.97 × 10-4 131
70.0 9.24 × 10-4 135
80.0 0.00106 154
90.0 0.00119 173
100 0.00132 193
200 0.00264 385
300 0.00396 578
400 0.00528 771
500 0.00660 964
600 0.00792 1160
700 0.00924 1350
800 0.0106 1540
900 0.0119 1730
1000 0.0132 1930
2000 0.0264 3850
3000 0.0396 5780
4000 0.0528 7710
5000 0.0660 9640
6000 0.0792 1.16 × 104
7000 0.0924 1.35 × 104
8000 0.106 1.54 × 104
9000 0.119 1.73 × 104
1.00 × 104 0.132 1.93 × 104
2.00 × 104 0.264 3.85 × 104
3.00 × 104 0.396 5.78 × 104
4.00 × 104 0.528 7.71 × 104
5.00 × 104 0.660 9.64 × 104
6.00 × 104 0.792 1.16 × 105
7.00 × 104 0.924 1.35 × 105
8.00 × 104 1.06 1.54 × 105
9.00 × 104 1.19 1.73 × 105
1.00 × 105 1.32 1.93 × 105
1.54 × 105 2.03 2.97 × 105
Steel I Beam: W21 × 68 (Wide Flange 21 inch tall × 68 lbf/ft)
L = 20.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
68.0 0.00284 233
70.0 0.00292 240
80.0 0.00334 274
90.0 0.00375 308
100 0.00417 343
200 0.00834 685
300 0.0125 1030
400 0.0167 1370
500 0.0209 1710
600 0.0250 2060
700 0.0292 2400
800 0.0334 2740
900 0.0375 3080
1000 0.0417 3430
2000 0.0834 6850
3000 0.125 1.03 × 104
4000 0.167 1.37 × 104
5000 0.209 1.71 × 104
6000 0.250 2.06 × 104
7000 0.292 2.40 × 104
8000 0.334 2.74 × 104
9000 0.375 3.08 × 104
1.00 × 104 0.417 3.43 × 104
2.00 × 104 0.834 6.85 × 104
3.00 × 104 1.25 1.03 × 105
4.00 × 104 1.67 1.37 × 105
5.00 × 104 2.09 1.71 × 105
6.00 × 104 2.50 2.06 × 105
7.00 × 104 2.92 2.40 × 105
8.00 × 104 3.34 2.74 × 105
8.67 × 104 3.62 2.97 × 105
Steel I Beam: W21 × 68 (Wide Flange 21 inch tall × 68 lbf/ft)
L = 25.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
68.0 0.00692 364
70.0 0.00713 375
80.0 0.00815 428
90.0 0.00916 482
100 0.0102 535
200 0.0204 1070
300 0.0305 1610
400 0.0407 2140
500 0.0509 2680
600 0.0611 3210
700 0.0713 3750
800 0.0815 4280
900 0.0916 4820
1000 0.102 5350
2000 0.204 1.07 × 104
3000 0.305 1.61 × 104
4000 0.407 2.14 × 104
5000 0.509 2.68 × 104
6000 0.611 3.21 × 104
7000 0.713 3.75 × 104
8000 0.815 4.28 × 104
9000 0.916 4.82 × 104
1.00 × 104 1.02 5.35 × 104
2.00 × 104 2.04 1.07 × 105
3.00 × 104 3.05 1.61 × 105
4.00 × 104 4.07 2.14 × 105
5.00 × 104 5.09 2.68 × 105
5.55 × 104 5.65 2.97 × 105
Steel I Beam: W21 × 68 (Wide Flange 21 inch tall × 68 lbf/ft)
L = 30.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
68.0 0.0144 524
70.0 0.0148 540
80.0 0.0169 617
90.0 0.0190 694
100 0.0211 771
200 0.0422 1540
300 0.0633 2310
400 0.0845 3080
500 0.106 3850
600 0.127 4630
700 0.148 5400
800 0.169 6170
900 0.190 6940
1000 0.211 7710
2000 0.422 1.54 × 104
3000 0.633 2.31 × 104
4000 0.845 3.08 × 104
5000 1.06 3.85 × 104
6000 1.27 4.63 × 104
7000 1.48 5.40 × 104
8000 1.69 6.17 × 104
9000 1.90 6.94 × 104
1.00 × 104 2.11 7.71 × 104
2.00 × 104 4.22 1.54 × 105
3.00 × 104 6.33 2.31 × 105
3.85 × 104 8.13 2.97 × 105
Steel I Beam: W21 × 68 (Wide Flange 21 inch tall × 68 lbf/ft)
L = 40.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
68.0 0.0454 932
70.0 0.0467 959
80.0 0.0534 1100
90.0 0.0601 1230
100 0.0667 1370
200 0.133 2740
300 0.200 4110
400 0.267 5480
500 0.334 6850
600 0.400 8220
700 0.467 9590
800 0.534 1.10 × 104
900 0.601 1.23 × 104
1000 0.667 1.37 × 104
2000 1.33 2.74 × 104
3000 2.00 4.11 × 104
4000 2.67 5.48 × 104
5000 3.34 6.85 × 104
6000 4.00 8.22 × 104
7000 4.67 9.59 × 104
8000 5.34 1.10 × 105
9000 6.01 1.23 × 105
1.00 × 104 6.67 1.37 × 105
2.00 × 104 13.3 2.74 × 105
2.17 × 104 14.5 2.97 × 105
Steel I Beam: W21 × 68 (Wide Flange 21 inch tall × 68 lbf/ft)
L = 50.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
68.0 0.111 1460
70.0 0.114 1500
80.0 0.130 1710
90.0 0.147 1930
100 0.163 2140
200 0.326 4280
300 0.489 6420
400 0.652 8570
500 0.815 1.07 × 104
600 0.978 1.28 × 104
700 1.14 1.50 × 104
800 1.30 1.71 × 104
900 1.47 1.93 × 104
1000 1.63 2.14 × 104
2000 3.26 4.28 × 104
3000 4.89 6.42 × 104
4000 6.52 8.57 × 104
5000 8.15 1.07 × 105
6000 9.78 1.28 × 105
7000 11.4 1.50 × 105
8000 13.0 1.71 × 105
9000 14.7 1.93 × 105
1.00 × 104 16.3 2.14 × 105
1.39 × 104 22.6 2.97 × 105
Steel I Beam: W21 × 68 (Wide Flange 21 inch tall × 68 lbf/ft)
L = 60.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
68.0 0.230 2100
70.0 0.236 2160
80.0 0.270 2470
90.0 0.304 2780
100 0.338 3080
200 0.676 6170
300 1.01 9250
400 1.35 1.23 × 104
500 1.69 1.54 × 104
600 2.03 1.85 × 104
700 2.36 2.16 × 104
800 2.70 2.47 × 104
900 3.04 2.78 × 104
1000 3.38 3.08 × 104
2000 6.76 6.17 × 104
3000 10.1 9.25 × 104
4000 13.5 1.23 × 105
5000 16.9 1.54 × 105
6000 20.3 1.85 × 105
6250 21.1 1.93 × 105
Steel I Beam: W21 × 68 (Wide Flange 21 inch tall × 68 lbf/ft)
L = 70.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
68.0 0.426 2850
70.0 0.438 2940
80.0 0.501 3360
90.0 0.563 3780
100 0.626 4200
200 1.25 8390
300 1.88 1.26 × 104
400 2.50 1.68 × 104
500 3.13 2.10 × 104
600 3.76 2.52 × 104
700 4.38 2.94 × 104
800 5.01 3.36 × 104
900 5.63 3.78 × 104
1000 6.26 4.20 × 104
2000 12.5 8.39 × 104
3000 18.8 1.26 × 105
3380 21.1 1.42 × 105
Steel I Beam: W21 × 68 (Wide Flange 21 inch tall × 68 lbf/ft)
L = 80.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
68.0 0.726 3730
70.0 0.747 3840
80.0 0.854 4390
90.0 0.961 4930
100 1.07 5480
200 2.14 1.10 × 104
300 3.20 1.64 × 104
400 4.27 2.19 × 104
500 5.34 2.74 × 104
600 6.41 3.29 × 104
700 7.47 3.84 × 104
800 8.54 4.39 × 104
900 9.61 4.93 × 104
1000 10.7 5.48 × 104
1980 21.1 1.08 × 105
Steel I Beam: W21 × 68 (Wide Flange 21 inch tall × 68 lbf/ft)
L = 90.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
68.0 1.16 4720
70.0 1.20 4860
80.0 1.37 5550
90.0 1.54 6240
100 1.71 6940
200 3.42 1.39 × 104
300 5.13 2.08 × 104
400 6.84 2.78 × 104
500 8.55 3.47 × 104
600 10.3 4.16 × 104
700 12.0 4.86 × 104
800 13.7 5.55 × 104
900 15.4 6.24 × 104
1000 17.1 6.94 × 104
1240 21.1 8.57 × 104
Steel I Beam: W21 × 68 (Wide Flange 21 inch tall × 68 lbf/ft)
L = 100 ft
P (lbf/ft) w_max (in) stress_max (psi)
68.0 1.77 5830
70.0 1.82 6000
80.0 2.09 6850
90.0 2.35 7710
100 2.61 8570
200 5.21 1.71 × 104
300 7.82 2.57 × 104
400 10.4 3.43 × 104
500 13.0 4.28 × 104
600 15.6 5.14 × 104
700 18.2 6.00 × 104
800 20.9 6.85 × 104
811 21.1 6.94 × 104
Steel I Beam: W21 × 68 (Wide Flange 21 inch tall × 68 lbf/ft)
L = 125 ft
P (lbf/ft) w_max (in) stress_max (psi)
68.0 4.33 9100
70.0 4.45 9370
80.0 5.09 1.07 × 104
90.0 5.73 1.20 × 104
100 6.36 1.34 × 104
200 12.7 2.68 × 104
300 19.1 4.02 × 104
332 21.1 4.44 × 104
Steel I Beam: W21 × 68 (Wide Flange 21 inch tall × 68 lbf/ft)
L = 150 ft
P (lbf/ft) w_max (in) stress_max (psi)
68.0 8.97 1.31 × 104
70.0 9.24 1.35 × 104
80.0 10.6 1.54 × 104
90.0 11.9 1.73 × 104
100 13.2 1.93 × 104
160 21.1 3.09 × 104
Additional Information
Related Pages
FREE Publications
3D Scanners

A white paper to assist in the evaluation of 3D scanning hardware solutions.

STEM Career Outlook

Wages, employment opportunities, and growth projections for STEM jobs.

Negotiate Your Salary

Learn the best principles to negotiate the salary you deserve!

CNC Machining Design Guide

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

more publications