Seismic analysis of plastic water tanks 3

[NKT]

I am looking for information on seismic analysis of plastic water storage tanks.

I have only been able to find information on steel and concrete tanks. I looked into using the steel tank analysis as a starting point, but it seems that the elastic modulus, failure strain, etc are bundled together in empirical(?) constants.

Any help would be appreciated.

 

[futharkk]

I took a quick look at "Guidelines for Seismic Evaluation and Design of Petrocheical Facilities" from ASCE. At the time the document was written (about 12 years ago) no known standard existed for seismically assessing plastic tanks. The document suggests to use API650 (or AWWA) for the loads and to use material properties from the manufacturer to determine the capacity. Hope this helps.

 

[JStephen]

ASCE 7-05 in Table 15.4-2 includes a line for "fiber-reinforced plastic" and a line for "All other", and I assume it could be covered under one or the other.

The general analysis for forces from API-650 should work, but R factors could vary due to material.

 

[JedClampett]

Usually we require the manufacturer to do their own seismic (and all other) design. And they have engineers, either on staff or contracted, who are experienced doing these calculations.
So I'm confused why you need to do these calculations yourself.

 

[JStephen]

Maybe he's on staff or contracted to do this. Or perhaps wants to size foundations prior to bidding out the tank.

 

[NKT]

Thanks for the replies; this gives me a good place to start.

The owner requested that I check the seismic performance of the tank. I'll proceed with the AWWA analysis to get the hoop stress and shell compression stress, and compare against published material properties to get a ballpark idea of whether or not the kind of tank I'm considering will work.

Then I'll add a requirement to the spec that the tank supplier provide documentation of seismic performance for the specific site conditions.

My main concern was modeling the more exotic failure modes like "elephant foot" buckling and sloshing damage at the tank top, but it sounds like I can leave that to the tank supplier.

Thanks Again.