Vacuum in Addenda 4

[LeonEarle]

API 650 Addenda 4 now includes an appendix V for considering vacuum. Once I have determined the moment of inertia and the area required for end stiffening at the bottom, I need to compare to the moment and area of the shell and bottom contributing. No problem with the area but when looking at the moment of inertia, can I figure the moment of inertia for each part (shell and then bottom) and add these?

 

[JStephen]

You need to figure the moment of inertia of the composite section, which will be more than the sum of the moments of inertia of the two parts (assuming you're taking moments of inertia about a vertical axis).