ASCE 7-10 Chapter 15 Seismic Loading on Tanks
ASCE 7-10 Chapter 15 Seismic Loading on Tanks
(OP)
I've been tasked with designing a foundation system for a 60' tall, 50,000 gallon ground-support tank used for liquid storage. My firm has had a older "rule of thumb" reference on tank seismic design from IBC 2000.
However, looking through ASCE 7-10's seismic requirements, it would seem section 15.7.6 would be the appropriate method to use in finding the seismic base shear for the tank. I've yet to find a good design example for ASCE 7-10 Ch. 15, if anyone could point me to one? But I have specific questions as well:
1. How is Wc (portion of liquid weight sloshing) calculated? Is this provided from the tank manufacturer typically? Further, are there any approximate methods out there?
2. Is TL the same as it would be for typical buildings? (i.e. using Figure 22-12)
3. At what elevations are the impulsive and convective base shears applied? I imagine the convective effects would occur at a higher elevation than the typical impulsive effects?
I would appreciate input on any of these questions. Thanks!
However, looking through ASCE 7-10's seismic requirements, it would seem section 15.7.6 would be the appropriate method to use in finding the seismic base shear for the tank. I've yet to find a good design example for ASCE 7-10 Ch. 15, if anyone could point me to one? But I have specific questions as well:
1. How is Wc (portion of liquid weight sloshing) calculated? Is this provided from the tank manufacturer typically? Further, are there any approximate methods out there?
2. Is TL the same as it would be for typical buildings? (i.e. using Figure 22-12)
3. At what elevations are the impulsive and convective base shears applied? I imagine the convective effects would occur at a higher elevation than the typical impulsive effects?
I would appreciate input on any of these questions. Thanks!






RE: ASCE 7-10 Chapter 15 Seismic Loading on Tanks
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RE: ASCE 7-10 Chapter 15 Seismic Loading on Tanks
Generally, the approach will be to do all the calculations per API or AWWA, then check for any adjustments required by ASCE 7.
RE: ASCE 7-10 Chapter 15 Seismic Loading on Tanks
API-650 (mostly used for welded steel tanks found in tank farms)
AWWA D100 (water tanks of any material and occasionally elevated up on stands)
I've only anchored tanks per AWWA D100 but if you can get your hands on it it has all the equations to determine the sloshing and impulsive force as well as the height of the force application. The terms include a lot of hyperbolic sine and cosine terms if I recall. But it's a prescriptive process.
The overturning values per AWWA are a little better (as in less conservative) than those found by simply treating the tank as a rigid mass per the Chapter 15 simplified approach.
RE: ASCE 7-10 Chapter 15 Seismic Loading on Tanks
But I'll warn you, you'll be using buttons on your calculator you didn't even know you had.
RE: ASCE 7-10 Chapter 15 Seismic Loading on Tanks
We actually have a copy of ACI350.3-06, which seems to present the same dynamic model that ASCE 7-10 is using (Housner 1963). If I'm analyzing a steel tank, are ACI350.3 equations for Tc, Wc, etc. still applicable considering it was written for concrete structures? In other words, do those equations apply to "flexible" structures as they do "rigid" concrete structures?
RE: ASCE 7-10 Chapter 15 Seismic Loading on Tanks
I have the same task at my firm, the design of a 30,000 gallon water storage flat-bottom concrete tank, in Southern California, and haven't been able to find an example on how to do this, any help will be greatly appreciated.