API 650 Roof - Uplift Pressures
API 650 Roof - Uplift Pressures
(OP)
I have a question regarding the intent/philosophy related to the design of supported cone roofs in API 650.
The specific question is regarding design of the roof for suction (uplift) forces from wind. I see that the roof plate is not normally welded to the supporting structure and I am interested in understanding how the roof carries the loading to the shell. Is it assumed/tested that the roof plate will simply deflect enough to carry the wind loads via membrane stresses to the perimeter? If so, are the any practical diameter limits? Are their concerns with impact loading on the roof structure as the plate vibrates due to variable wind suction pressures?
I am asking these questions as the Engineering Representative for an Owner purchasing the tank. I just want to be sure that we do not have issues with the roof during a wind event.
Any assistance provided would be greatly appreciated.
The specific question is regarding design of the roof for suction (uplift) forces from wind. I see that the roof plate is not normally welded to the supporting structure and I am interested in understanding how the roof carries the loading to the shell. Is it assumed/tested that the roof plate will simply deflect enough to carry the wind loads via membrane stresses to the perimeter? If so, are the any practical diameter limits? Are their concerns with impact loading on the roof structure as the plate vibrates due to variable wind suction pressures?
I am asking these questions as the Engineering Representative for an Owner purchasing the tank. I just want to be sure that we do not have issues with the roof during a wind event.
Any assistance provided would be greatly appreciated.





RE: API 650 Roof - Uplift Pressures
The roof would have to carry the uplift forces via membrane stresses to the perimeter. The slope of the roof aids this.
Small tanks (subjective) are not able to have frangible roofs, so are not negatively affected by having their supporting structures welded to the roof plate. Of course, these tanks often require no supporting structure at all.
I believe the effect of impact loading would be covered by the required live load rating of the roof.
RE: API 650 Roof - Uplift Pressures
Thousands have been in service for decades without failure from wind load.
I think you can rest easy.
RE: API 650 Roof - Uplift Pressures
Have we ever had a "code case in regarding the up-lift in API650" ..what was the answer of the committee ?
why do not we have this issue of up lift with vessels..etc..
of course many "how' s"
Thanks a lot
take care and thanks
RE: API 650 Roof - Uplift Pressures