Cable Suspended IFR

[Ahlai78]

Hi,

We have a client would like install cable suspended Internal Floating Roof (IFR) for a new tank (diameter=25m).
due to certain reasons, we prefer to use self-supported dome roof without rafter to support the IFR.

I would like to check whether self-support dome roof without rafter strong enough to support the IFR weight due to point load as requested by API650.

What type of calculation shall been used to analysis strength of roof in such a case, by FEA?

Thank for the advice.

 

[IFRs]

You can use point loading in FEA or run the analysis by hand. Sometimes people just add a uniform load and do not go into the detail of locating point loads. In this case you might want to look at the local stresses for a single point load. The load will be based on the area supported by each of the cables, the unhjit dead load per the manufacturer and the unit live load per API 650. Per API 650, if the IFR includes automatic drains the live load is 5 psf, if not then it is 12.5 psf. The dead load will vary between 1.25 psf and 2 psf depending on the manufacturer and quality of the IFR. API 650 includes all the load combinations and load factors you need to consider. A 25M IFR will have between about 20 and 40 cables depending on the vendor. Some vendors can easily add additional uniformly spaced cables if it helps.

 

[Soln]

IFR- can you suggest a reference for hand calculating the stress on the roof due to the pointload?