Modified Stiffness in Moment Distr
Modified Stiffness in Moment Distr
(OP)
I have a three span beam with two-three foot overhangs. I treated the ends with the overhangs as pinned and did one moment distribution using modified stiffness (0.75*stiffenss) at the pinned ends and one without modified stiffness. They both converge to within two decimal places (using Excel) but they got different answers at the interior supports. Is it proper to consider a continuous beam with an overhang to be a pinned end? Is modified stiffness mandatory for a pinned end? I thought it was just to speed up convergence which is not a problem with Excel anyway. Everything about the two spreadsheets is identical except the two stiffnesses.
Thanks,
DPA
Thanks,
DPA






RE: Modified Stiffness in Moment Distr
Good luck.
RE: Modified Stiffness in Moment Distr
RE: Modified Stiffness in Moment Distr
apsix,
Thank you for your comments.
Motorcity,
You are right about the moment being zero at a pinned end but not if there is an overhang. When you get to the bottom of the moment distribution the moment on both sides of the pin should be equal to the original moment calculated for a cantilever. In both my spreadsheets the moments at the supports next to the cantilevers do converge to the proper values. It is only the internal supports where there is a difference between the two spreadsheets.
haynewp,
I agree with your answer but I just can't seem to figure out what the problem is. I suspect that the modified stiffness value in Hsieh's book may only apply to a simple pinned end with no overhang. Can't figure out why that should be just yet.
Thanks guys for all the quick responses.
DPA
RE: Modified Stiffness in Moment Distr
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My version of the propped cantilever
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RE: Modified Stiffness in Moment Distr
-Mike
RE: Modified Stiffness in Moment Distr
DPA
RE: Modified Stiffness in Moment Distr