# SRSS on non-building structure?



## McEngr (Dec 15, 2010)

The SEAOC Vol 1 manual does a mass-distributed 1st mode period check on a vertically supported tank. However, it doesn't actually calculate the period. It only references a previous example. Is it worth looking into the structural dynamics book by SK Ghosh? Any suggestions are welcome.


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## MA_PE (Dec 15, 2010)

McEngr said:


> The SEAOC Vol 1 manual does a mass-distributed 1st mode period check on a vertically supported tank. However, it doesn't actually calculate the period. It only references a previous example. Is it work looking into the structural dynamics book by SK Ghosh? Any suggestions are welcome.


Wouldn't the period be dependent on the fluid action of the stored material in the tank? I'd think you need a dynamic FEM analysis to do this correctly.


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## McEngr (Dec 15, 2010)

MA_PE said:


> McEngr said:
> 
> 
> > The SEAOC Vol 1 manual does a mass-distributed 1st mode period check on a vertically supported tank. However, it doesn't actually calculate the period. It only references a previous example. Is it work looking into the structural dynamics book by SK Ghosh? Any suggestions are welcome.
> ...


I think chapter 13 of ASCE 7 says you can bump up the seismic force (not the rho factor) by 1.3 for rigid elements and without the sloshing. Chapter 13 also says that sloshing does not need to be considered unless it is a wide tank (ie for large diameter water storage or treatment).


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## Hromis1 (Dec 15, 2010)

McEngr,

I don't have the SEAOC book with me....does the solution differ from what is outlined in Chapter 15 of the ASCE 7 book? Ie section 15.7.6.1, equation 15.7-12? (natural period of sloshing equation)

I don't recall the problem well, was it a liquid tank, or a solid storage silo?

hromis1


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## Hromis1 (Dec 15, 2010)

McEngr,

You typed you answer regarding the question faster than I could answer. Again I don't recall the problem well, but in practice I am usually citing chapter 15, rather than chapter 13 for non-building structures.

But some of the details like minimum forces etc are different. (Cs)

I don't recall what this particular problem used, but I have had some tanks with very high or very low specific gravities....

If they did not use on of the approaches in chapter 15, I would call the answer "suspect"

Hromis1


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