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Inverted Umbrella Concrete Roof Structure

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I have been asked to analyze an existing inverted umbrella concrete roof system built in 1968 near Memphis, TN.  The roof system is 100'-0 x 150'-0  and formed by 6 segments 50'-0 per side, each identical to the others, forming a 2 deep by 3 wide pattern.  At the interfaces between the cells, a keyed joint is present with #3 dowels.  The structure is supported by a 24" square RC column. 
 
The current building line is well inside the roof line - essentially 52'-0 x 102'-0.  The client would like to gut the current wall system and fully enclose a building at the roof edge. 
 
At this point, I have two primary concerns:  1.)  earthquake effects on this shape     and   2.)  determining the deflection expected at the perimeter of the roof system.
 
Any thoughts, guidance, or suggestions would be greatly appreciated.

Thanks!
 
Bobby Jenkins, P.E.
Jenkins Engineering, Inc.
PO Box 2101
Tupelo, Ms  38803
662.840.1233 V / 662.840.1103 F