MecaStack has two methods by which to analyze breach openings (Cutouts) in stacks.
1) Troitsky Method
This is the more conservative approach and the one Meca recommends following when at all possible. For a more detailed explanation of this method, please click this link to read the "Troitsky Breach Analysis" article.
2) Section Properties
This is a more simplistic approach that was used exclusively by MecaStack in versions prior to v5506. Please refer to Article Life is a Breach for more detail on this method.
There isn’t a lot of great information on designing breech openings, but there is a little information. CICIND published some information in the link below.
http://www.mecaenterprises.com/downloads/software/CICIND_Breech_Openings.pdf
Round Openings:
All of the same basic principles are applied as above; however, you usually the reinforcement of a round opening is a reinforcement pad (Repad). In this case we take the cross sectional area of the repad is considered as the "Stiffener". This is handled automatically when you select the option within MecaStack Details / Nozzle (Round).
At this time the Round Opening option (Nozzle) in MecaStack uses only the "Section Property" analysis method.