I'm running a simple simulation of a rectangular vacuum chamber subjected to external ambient pressure using shell elements, just to verify my calculation with the ASME VIII code. However, I got really confused when trying to plot the bending stress.
For shell elements, when generating a stress plot, I have the option to select the stress component (Von Mises, principal etc.) but also bending/membrane. My question is, how can a stress be Von Mises stress and bending stress at the same time?
Also, I set up my simulation as indicated in the attached picture but the result does not make sense comparing to my hand calculation. I basically applied gravity and external pressure on the out side of the box while fixing the bottom face.
Could anyone provide insight on what I'm doing wrong?