How do you apply platform loads to a self supporting cone/umbrella?
How do you apply platform loads to a self supporting cone/umbrella?
(OP)
I have a 20' diameter tank that currently has a self-supporting cone roof with 3.65" in 12" pitch. I need to install a 12' x 15' platform above the roof and need to know how to apply the platform loads for designing the roof thickness. Platform will be 17.25 psf dead weight and API 650 says platform is to be designed with 1,000# moving concentrated load. We are planning to support with 9 supports from platform to roof.
Roof design dead load is weight of roof plate. Rood design live load is 20 psf in accordance with API 650. To apply the roof loads, do I distribute the loads over the area of the platform or calculate the loads as 9 concentrated loads?
Is there a reference for how to do this?
Thanks!!!
Roof design dead load is weight of roof plate. Rood design live load is 20 psf in accordance with API 650. To apply the roof loads, do I distribute the loads over the area of the platform or calculate the loads as 9 concentrated loads?
Is there a reference for how to do this?
Thanks!!!





RE: How do you apply platform loads to a self supporting cone/umbrella?
Joe Tank
RE: How do you apply platform loads to a self supporting cone/umbrella?
You have two issues. One is a lack of design methods for analyzing the roof under concentrated loads. (Come to think of it, you could treat it as a cylinder with radius equal to the cone roof normal radius, and use WRC 297 on it, but that would be a pain.)
Second issue is that there should be a big difference in rigidity between the shell and the roof, so that supports distributed across both would not be equally supported by both.
RE: How do you apply platform loads to a self supporting cone/umbrella?
RE: How do you apply platform loads to a self supporting cone/umbrella?
I concur that stiffening of the tank wall is likley required. I normally put the vertical shell stiffeners on the outside of the shell.
Joe Tank
RE: How do you apply platform loads to a self supporting cone/umbrella?
RE: How do you apply platform loads to a self supporting cone/umbrella?
RE: How do you apply platform loads to a self supporting cone/umbrella?
Joe Tank