Calculating moment capacity and section modulus for pipes/cylinders
Calculating moment capacity and section modulus for pipes/cylinders
(OP)
The AWWA M11 gives
Section modulus = I/c = π * r^2 * t
However, I found in the McGraw Hill Civil Engineering Formulas textbook,
Section modulus = I / c = π (OD^4 - ID^4)/(32 * OD)
The results are totally different.
Has anybody done any bending moment checks on large pipes/cylinders?
Thanks.
Section modulus = I/c = π * r^2 * t
However, I found in the McGraw Hill Civil Engineering Formulas textbook,
Section modulus = I / c = π (OD^4 - ID^4)/(32 * OD)
The results are totally different.
Has anybody done any bending moment checks on large pipes/cylinders?
Thanks.






RE: Calculating moment capacity and section modulus for pipes/cylinders
RE: Calculating moment capacity and section modulus for pipes/cylinders
RE: Calculating moment capacity and section modulus for pipes/cylinders
15^2 * 0.05 = 11.25 in^3
Using the McGraw formula:
(30^4 - 29.9^4)/(32 * 30) = 11.19 in^3
A change of less than 1/2 of a percent.
It doesn't work so well when the wall gets thick compared to the diameter, though:
10" diameter, 1/2" W.T. pipe:
5^2 x .5 = 12.5 in^3
Now if I use the McGraw formula:
(10^4 - 9^4)/(32 x 10) = 10.75 in^3
which comes in at 16% off...
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