using ASCE 7-16 chapter 15 vs ACI 350.3 1

[MathStructeng]

Hi,
I am currently designing a concrete water tank and I was wondering which seismic design code shall be used.
ASCE 7-16, chapter 15, clause 15.4 calculates seismic shear force regardless of impulsive and convective forces.
On the other hand ACI 350.3 calculates two mentioned forces and their overturning moments.
Anyone with water tank design experience care to shed some light?

Thanks,
Math

 

[r13]

Below is the excerption of introduction of the document of ACI350.3-06. You should get the present copy and go over it, as the instructions may have changed. Hope it helps.

"INTRODUCTION
.....
The seismic subcommittee’s work was guided by two main objectives: 1. To produce a self-contained set of procedures that would enable a practicing engineer to perform a full seismic analysis and design of a liquid-containing structure. This meant that these procedures should cover both aspects of seismic design: the “loading side” (namely the determination of the seismic loads based on the mapped maximum considered earthquake spectral response accelerations at short periods (Ss) and 1 second (S1) obtained from the Seismic Ground Motion maps [Fig. 22-1 through 22-14 of ASCE 7-05, Chapter 22] and the geometry of the structure); and the “resistance side” (the detailed design of the structure in accordance with the provisions of ACI 350, so as to resist those loads safely); and 2. To establish the scope of the new procedures consistent with the overall scope of ACI 350. This required the inclusion of all types of tanks—rectangular, as well as circular; and reinforced concrete, as well as prestressed. (Note: While there are currently at least two national standards that provide detailed procedures for the seismic analysis and design of liquid-containing structures (ANSI/AWWA 1995a,b), these are limited to circular, prestressed concrete tanks only).

As the loading side of seismic design is outside the scope of ACI 318, Chapter 21, it was decided to maintain this practice in ACI 350 as well. Accordingly, the basic scope, format, and mandatory language of Chapter 21 of ACI 318 were retained with only enough revisions to adapt the chapter to environmental engineering structures....."

 

[JStephen]

With steel tanks that are "large" (say, more than 30' or so diameter) consideration of the convective forces reduces the overturning moment on the tank, which may not be the effect you would expect. IE, treating the entire structure as a rigid mass/ impulsive may be more conservative. (Consideration of sloshing may also increase the require freeboard, though.)

 

[HTURKAK]

I will suggest you to look 15.7 TANKS AND VESSELS ..and for ground supported tanks,15.7.6 Ground-Supported Storage Tanks for Liquids.. and commentary C15.7

I copied and pasted the relevant item,


That is, for OT and V base, will be calculated assuming entire content and tank mass are impulsive..

You are expected also to comply with other requirements stated at 15.7

If you provide the tank details with specific question, you may get better specific responds..