Using ACI 318 in tanks design
Using ACI 318 in tanks design
(OP)
Hi everyone,
I am a reviewing a tank design calculation submitted by a NYS Structural Engineer.
I do not agree with the calculation and I want to get your opinion about some of the assumptions in the structural
calculation report.
1. The report considered ACI 350 just a recommendation and based on that ACI 318 has been used to eliminate the
sanitary factor (1.3) and reduce the design moment on the tank walls.
2. The calculation is based on PCA tables but it did not follow the listed modification in the book calculation.
3. The calculation used minimum area steel equations listed in ACI 350 (As, min = ((3 x square root(f’c))/fy) x bw x d
≥ (200/fy) x bw x d) and then claimed that even the horizontal reinforcement is not meeting those equations, it is ok
because ACI 350 is only recommendation and the horizontal rebars area steel satisfies the minimum temperature &
shrinkage area steel listed in ACI 318!, As far as I know, the minimum area steel equation listed in ACI 350 is
adopted and listed in ACI 318 should be applied using both code. The horizontal reinforcement of the walls is
# 4 @ 12" .
I would appreciate your opinion.
Thank You
Nader Soliman, P.E.
I am a reviewing a tank design calculation submitted by a NYS Structural Engineer.
I do not agree with the calculation and I want to get your opinion about some of the assumptions in the structural
calculation report.
1. The report considered ACI 350 just a recommendation and based on that ACI 318 has been used to eliminate the
sanitary factor (1.3) and reduce the design moment on the tank walls.
2. The calculation is based on PCA tables but it did not follow the listed modification in the book calculation.
3. The calculation used minimum area steel equations listed in ACI 350 (As, min = ((3 x square root(f’c))/fy) x bw x d
≥ (200/fy) x bw x d) and then claimed that even the horizontal reinforcement is not meeting those equations, it is ok
because ACI 350 is only recommendation and the horizontal rebars area steel satisfies the minimum temperature &
shrinkage area steel listed in ACI 318!, As far as I know, the minimum area steel equation listed in ACI 350 is
adopted and listed in ACI 318 should be applied using both code. The horizontal reinforcement of the walls is
# 4 @ 12" .
I would appreciate your opinion.
Thank You
Nader Soliman, P.E.






RE: Using ACI 318 in tanks design
As a summary:
Eliminating the 1.3 sanitary factor-BAD IDEA
Not using minimum bending steel-BAD IDEA
PCA Tables-OK, if all the errata are considered. Bureau of Reclamation has better tools.
This sounds like a rookie design. A tank is no place to economize. Us hairy eared engineers know that.
I'd make my comments, note them as important and keep track of the project. There will be a failure and when they blame the contractor, your notes will be valuable to their lawyers. See below:
http://www.pressconnects.com/article/20110816/NEWS...
http://www.knoxnews.com/news/2011/oct/27/deficient...
RE: Using ACI 318 in tanks design
Mike McCann
MMC Engineering
RE: Using ACI 318 in tanks design
RE: Using ACI 318 in tanks design
RE: Using ACI 318 in tanks design
I would say that it's not proper to refer to ACI 350 as a recommendation but not sure how things like that are enforced. Most city/entities don't specifically call out in their building codes a requirement for 350 as they usually deal with buildings. That said, the use of 350 in tanks is so typical and prevalent in the US that NOT using 350 sort of takes that NY engineer out of the "reasonable standard" that we engineers are judged by. If the tanks do leak, as miecz suggests, then that NY engineer really has no way to testify as to why they didn't use it (when questioned by the complainant's attorney).
RE: Using ACI 318 in tanks design
RE: Using ACI 318 in tanks design
RE: Using ACI 318 in tanks design
Regardless of which shape the tank is, I can't recall a single design where analysis didn't require more steel than the minimum required in the horizontal dimension. If this tank is rectangular there will be significant moments in the horizontal direction and if it is circular there will significant tensile hoop forces. Something doesn't seem correct.
RE: Using ACI 318 in tanks design
Brian C Potter, PE
http://simplesupports.wordpress.com
RE: Using ACI 318 in tanks design
RE: Using ACI 318 in tanks design
used in water and waste treatment works where dense, impermeable concrete with high resistance to chemical attack is required."
NADER666 hasn't told us what this tank is designed to hold or any serviceability requirements, such as being water tight. I think most just assumed this was a water or watewater tank.
I would agree that any water or wastewater treatment should be designed using ACI 350. The intent of these structures is that they will be watertight.
RE: Using ACI 318 in tanks design
A few thoughts here...
1. In the Northwest, and I do realize other regions have different water qualities, we do not have serious fertilizer or caustic chemical concerns (the tank is not designed to remove them anyway), and other than sediment, the only effluents we commonly worry about are oil and gasoline.
2. I also have a problem with the time of water detention in the tanks, which is commonly only 24 hours, as opposed to a water tank or digester that is continuous. Other than the bottom of the tank, any cracks of which eventually become clogged with sediment, the water has little time to escape through the walls. So what if some does and the walls are not subject to freeze-thaw?
3. Moreover, buried tanks/walls/slabs are not subject to the same freeze-thaw conditions as non buried or partly exposed wall, receiving latent heat from the ground they retain. I can see possibly applying the minimums to exposed walls. but, to me, even that is a stretch.
Personally, I think that ACI 350-06 needs to give the design engineer more latitude based on the local site conditions. It already gives some, but needs more to be realistic in its application.
Mike McCann
MMC Engineering