Subject: Circular Concrete Tanks without Prestressing
From: "David Hall" <Dahl(--nospam--at)deainc.com>
Date: Tue, 25 Jan 2000 16:12:04 -0800
Our firm has designed a circular concrete tank to be constructed in northern Washington. The design was done under the above listed publication. However, this design was done from what I am now told a 1960's version of this publication. I have a copy of the 1993 version.
Anyway, the base slab was detailed as being placed in segments (8 total) opposite of each other within the tank with expansion joints separating these pours and an 18 " wide by 12" reinforced continuous footing below this joint to prevent differential sentiment which would cause leaks. This is the recommended method prescribed in the 1960's version.
The 1993 version as eliminated this method and recommends using ACI 350R with consideration given for the "z" factor to reduce cracking.
Can anyone tell me why the 1960's method was removed from the code. I am providing the final QM review and the engineer who designed the tank insists his design is the way to go.
Also, that tank is above grade and seismic considerations were accounted for. Plans are going out to bid shortly.
Thank you for your assistance.
David A. Hall, S.E., P.E.