o-bround reinforcement

[Sergio76]

Hello guys, I have a vert. heater treater vessel where the opening is an o-bround shape, vessel is 72" OD and the o-bround is 27"W x 48"H, to calculate if the reinforcement is required, as this is a large opening, probably i need to use appx 1-10, my question is how i treat the shape geometry, it means can i considering as a circular opening with 48" diameter?, since non of the paragraphs for reinforcement specified how we have to modified the formulas according to the shape.
Someone have any ideas, Thanks!

 

[JStephen]

With a round opening, you can generally just check it in the direction of maximum stress. With an obround opening, you can check it in each direction, as the minimum opening dimension would normally be normal to the maximum stress.

 

[chaulklate]

Sergio,
My jurisdiction approaches this as you have indicated, to evaluate the opening as though it were ciruclar relative to the longest axis. I have calculated many obround openings this way. As the code does not offer firm guidance, it would be best to present your idea to your regulator/AI before proceeding.