Simulate, through thickness average stress also called membrane stress

Hi,

I am running Creo 3 Simulate, I am trying to determine the stress within the walls of a pressure vessel from external pressure, linear Von Mises has been run successfully, but we are now instructed to do membrane average stress, my question, is this possible and a different output menu pick for the analysis run. I am relatively new to Simulate.

thanks anyone

Geoff.