shell vs plate in SAP

[jiao]

I am studing the vibration period of a shell with SAP.
When I modeled it as a group of shells, everything is ok--I got the out-of-plane vibration period.
But when modeled as plates, I got in-plane vibration--shear deformation.
Can anyone tell me why? Thanks

 

[zliazmei]

In sap200 the plate element is designed to work only for shear forces and moments out of plane.
If you are trying to create a wall you will need to use shell elements.
Otherwise the plate ellement must be plased horizontaly.
Hope this will help.
Regards. BigZmeiIMnogoZul