API 650 Appendix E - What does "Y" stand for??

[jcoots]

I am looking at the newest version of App. E, Seismic Design and found that the definition of "Y" is not clear to me. The given definition states "Distance from liquid surface to analysis point". What is the analysis point?

Thanks,

 

[JStephen]

Typically, the bottom of the shell course. You could also assume this to be 1' above the bottom (for 1-foot method) or at the "variable design point" if the variable design point method is used. If seismic stresses are not extreme, it won't much matter.

 

[jcoots]

Thanks JStephen, you've been very helpful here and in the past.