Hi,
I modeled a multi level structure and i try to get periods of vibration modes.
When I change the method of plates calculation from shell to slab-rigid diaphragm, instead of a small increase, the periods decreased by half.
is this normal or how can i obtain the correct periods?
Thank you!
Solved! Go to Solution.
Solved by Pawel.Pulak. Go to Solution.
Please check the zip file you attached. I'm not able to open it.
The results you obtained were coherent with the calculation model of panels.
In case of shell model the first vibration periods for X and Y were 1.09 and 1.00 seconds respectively
In case if rigid diaphragm model the settings are as below:
Full rigid body is related to all degrees of freedom, i.e UX, UY, UZ displacements and RX, RY, RZ rotations. It means that each slab remains flat and that all columns remain perpendicular to slabs.
Such behavior corresponds to very significant increase of the stiffness of structure. That is why the first vibration periods for X and Y are in such case significantly smaller than for shell calculation model: 0.55 and 0.51 seconds respectively
What you tried to obtain was probably to define for slabs the diaphragm fixing only horizontal displacements. Such calculation model of the panels can be obtained using the following parameters:
In such case the first vibration periods for X and Y are as expected by you: 1.13 and 1.03 seconds respectively.
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Regards,
thanks a lot!
I thought I tried to change the rigid connection of nodes but obviously I didn't...