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RE: concrete tanks

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Title: concrete tanks
ACI 350R-89 suggests the designer should use the basic Gergley-Lutz equation, as recommended in the Commentary to Section 10.6.4 of ACI 318, for one-way flexural members.
According to it, "the servicibility requirements of ACI 318 to control calculated deflections and crack width are applicable to environmental engineering structures. For flexural reinforcement located in one layer, the quantity Z should not exceed 115 kips/in. Z values were established for cover equal to or less than 2-in (50 mm) and should be based on this value when the cover exceeds 2-in. Additional cover may be regarded as added protection".
Additionally the code stipulates, "for members subject to direct tension (hoop tension), a sanitary durability coefficient of 1.65 may be used for all grades of reinforcing. The factor Z has no direct bearing for this state of stress".
More over it further adds, "for severe environmental exposures, structural design should conform to section 2.6.6 (as detailed above, the code reference above is from section 2.6.6) with the quantity Z which does not exceed 95 kips/in., and surface or other protection or barrier should be provided suitable for the particular conditions of exposure".
I hope this helps. If you still need a copy of this, I can scan for you & send you later. Best regards,
Syed Faiz Ahmad; MEngg, M.ASCE
Senior Structural Engineer
Saudi Oger Ltd
Riyadh, Saudi Arabia.
-----Original Message-----
From: brian stanley [mailto:bstanley(--nospam--at)]
Sent: Tuesday, November 04, 2003 4:17 PM
To: seaint(--nospam--at)
Subject: concrete tanks

It is my understanding that ACI 350 contains recommendations as to crack widths/z-factor for water retaining structures.  What is the required crack width/z-factor for water retaining structures?  If someone has ACI 350, would anyone be willing to fax me that part of the code?  Does it make sense to use epoxy-coated rebar?  Are there special kinds of curing/sealing compounds that should be used?  Is silane based sealant with 40% alkytrialkoxsilane (typically used in parking garages) appropriate?  For reference, I am working on a ice/water tank which will be filled with water and then chilled over and over again.

Thanks for the help.

Brian Stanley
Baltimore, Md