API 650 -App. E. seismic design with floating roof

[carthago]

Seismic design floating roof:
reference : API -650- Appendix E

Wt = Total mass of tank content.

How can we include the Floating roof mass effect??
Does the stored liquid sees a splashing or sloshing ? or is it probably damped
Practically: What are the extra stresses generated by the roof when subjected to earthquake forcses/accelerations?

 

[JoeTank]

The roof obviously adds mass to the problem, but the method of how to incorporate it into the analysis is not covered in API-650. Although the roof adds mass, it is already accounted for in the product mass term since it displaces an equivalent mass of product when it is floating. The sloshing wave would be damped somewhat, but there are no provisions in the Standard for doing this. It conservatively ignores this issue.

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com

 

[IFRs]

You may want to check the floating roof for stresses. You could determine the slosh height up the shell and assume some curveed shape of the liquid that the IFR would follow. Also, you could determine the crest-to-crest wave height and see if the IFR can support itself between crests. Etc.