ASCE 7, Section 15.7.6: Calculation of value of Ti

[MThomey]

I'm working on a ground supported storage tank that must consider the hydrodynamic effects for seismic design. I need some guidance on a couple of things.
(1) How to calculate the fundamental period of the tank structure and impulsive component of content, Ti
(2) How to determine the impulsive weight, Wi
(3) How to determine the portion of liquid weight sloshing, Wc

Thanks, in advance, for any help with this problem.

 

[jittles]

This is one piece of information that is lacking in this section of ASCE 7. You should look in AWWA D100 (water tank code) or API 650 (petroleum tank code) for equations to calculate these.

It was a while ago, but I think google searches relating to these codes turned up a couple of examples of petroleum tank design that included these calculations and were very thorough.

 

[JoshPlumSE]

The references I have used in the past are the following:

ACI 350.3R Seismic Design of Liquid Containing Concrete Structures.

PCA's Design of Liquid-Containing Concrete Structures for Earthquake Forces

These are specifically for concrete tanks. The ACI document that I have is 2001 and is still based on 94 UBC type seismic loading. It doesn't look to me as if ACI has updated the document. Though I would tend to believe that the concept of splitting the liquid mass into convective vs impulsive components would not change much based on tank material. The PCA document seeks to convert the ACI formulas into more IBC type seismic loading.

 

[JoshPlumSE]

FWIW: I checked out the ACI website and that document (ACI 350.3) was updated in 2006. So, that new version should have all the newer IBC formulations for the seismic loading.

 

[MThomey]

Thanks gents. The google search hasn't turned up much. Does anyone know where I can get a copy
of API or AWWA without spending a fortune? Or maybe someone could post the equations I need.
Thanks!