S4R plane strain plane stress condition

[albert1981]

Dear all,

I am doing a plastic analaysis using S4R elements. The previous resutls show that the S_op will change wheather using plane stress or plane strain condition. I search on the manual but I could not find weather S4R can be considered as plane stress condition or plane strain condition. Which other element I can use as plane stress or plane strain?
If anybody can help me please let me know.

Thanks in advance,
Albert