Why do you get moment and stress concentrations where shells have a change in section properties or direction?
Discontinuous shells causes moment and stress concentrations when analysed with finite element calculation methods.
Shells with the same properties, which are shown in the same colour when the setting "Show element colour" is turned on, are seen as discontinuous when there is a change is surface direction. To overcome this, enable the "Smooth shells and solid stresses" setting on the "Settings" tab.
Shells with different properties, which are shown in different colours when the setting "Show element colour" is turned on, are also seen as discontinuous. To overcome this, the shells must be added to the same "Group Number". This is done on the “Shells” tab, in the column named "GN". Here the same number must be allocated to shells that form a continuous surface. The setting "Smooth stresses by group number also" on the "Settings" tab must be enabled.
Shells with mesh problems will also cause localised concentrations of forces and stresses, affecting the moment and stress diagrams. This can be due to incorrect mesh layout or meshing that is to coarse for the structure. Refining the mesh will improve the results of an analysis.