Hello

I have an FE model (linear elastic material, homogeneous) using shell181 elements. The structure is subject to constant acceleration and undergoes a static analysis (antype,static).

About shell,mid and keyopt(8), Ansys manual reports:

KEYOPT(8) = 2 stores midsurface results in the results file for single or multi-layer shell elements. If you use SHELL,MID, you will see these calculated values, rather than the average of the TOP and BOTTOM results. You should use this option to access these correct midsurface results (membrane results) for those analyses where averaging TOP and BOTTOM results is inappropriate; examples include midsurface stresses and strains with nonlinear material behavior, and midsurface results after mode combinations that involve squaring operations such as in spectrum analyses

My midsurface results are not the average of top and bottom results, despite linear material and static analysis.

Just as an example for one element, I have for Von Mises (PRETAB):

ELEM STOP SMID SBOT

41848 0.20593E+008 0.60772E+007 0.26821E+008

where SMID, Von mises at shell,mid location, clearly is not the average between top and bottom.

So, why is this behavior happening given that I have linear material and no response spectrum analysis?

Thanks in advance.

Mathias