Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

Register Log in
  • Congratulations GregLocock on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

What does ACI 350-06 consider to be "Environmental Exposure Conditions" for Mat Foundation

Status
Not open for further replies.
oengineer

oengineer

Structural
Apr 25, 2011
708
What does ACI 350-06 consider to be "Environmental Exposure Conditions" for shrinkage and temperature reinforcement for Mat Foundations?

Section 7.12.2.1 states the following:

"For members subjected to Environmental Exposure Conditions or required to be liquid tight, the area of shrinkage and temperature reinforcement shall provide at least the ratios of reinforcement area to gross concrete area shown in Table 7.12.2.1:

Concrete sections that are at least 24 in. may have the minimum shrinkage and temperature reinforcement based on a 12 in. concrete layer at each face. The reinforcement in the bottom of base slabs in contact with soil may be reduced to 50 percent of that required in Table 7.12.2.1."

The image below is Table 7.12.2.1
table_7.12.2.1_gf7vot.jpg



Would rain water meet this criteria? This is for a mat foundation being design for an irrigation pump station. The mat foundation is just a solid square block with a filter equipment sitting on top, so liquid tight situation would not apply. The filter equipment & mat foundation will NOT be covered and exposed to rain (whenever it rains).


Suggestions/comments are appreciated.
 
Replies continue below

Recommended for you

Sort by date Sort by votes
Here are some definitions that I have found in the ACI 360 code that mention Environmental Exposure:

Environmental_Exposure_def_y6zykp.jpg


Environmental_Exposure_def_2_vjbe1n.jpg


Would rain water or possible flooding ever be considered as meeting the following:

[ul]
[li]a pH greater than 5, or exposure to sulfate solutions 1000 ppm or less[/li]
[/ul]
 
Upvote 0 Downvote
How big is your irrigation pump station mat? And how thick is the mat?

If small enough, the differences between normal temp & shrinkage (.002) and the increased ACI 350 requirements (maybe ~.003) might not affect the design.
 
Upvote 0 Downvote
JoelTXCive said:
How big is your irrigation pump station mat? And how thick is the mat?
Click to expand...

The Mat Foundation is 12'-0" x 12'-0" and 24" thick. It has one piece of equipment on it.

There is also a Chlorine Containment shelter sitting on a Mat foundation that is 9'-6" x 9'-6" & 24" thick.
 
Upvote 0 Downvote
It would be also helpful to develop a design methodology regarding the interpretation of the statement "Environmental Exposure Conditions" for mat foundation designs supporting equipment for facilities using ACI 350.
 
Upvote 0 Downvote
For my mat foundation, liquid tightness would not be a deciding factor in applying the ACI 350 minimum shrinkage and temperature reinforcement.

The only aspect that may apply would be the Environmental Exposure Conditions. But would a general outdoor mat foundation be beholden to ACI 350 minimum shrinkage and temperature reinforcement of 0.003?
 
Upvote 0 Downvote
Suggestions/comments regarding the qualification for "Environmental Exposure Conditions" of foundations using ACI 350 are appreciated.
 
Upvote 0 Downvote
JoelTXCive said:
If small enough, the differences between normal temp & shrinkage (.002) and the increased ACI 350 requirements (maybe ~.003) might not affect the design.
Click to expand...

The issue is that I am reviewing a rebar submittal for a design that has already been provided. The reinforcing shown in the submittal meets ACI 318 shrinkage and temperature reinforcement for Mat Foundations, but the steel reinforcement would need to be increased if the "Environmental Exposure Conditions" mentioned in ACI 350 should apply.

The mat foundation is not a liquid tight situation.

If the reinforcing needs to be increased, it may possibly trigger a change order request. If the reinforcing only needs to satisfy ACI 318, then no increase in reinforcing is required (because it has already been satisfied).
 
Upvote 0 Downvote
An exterior equipment mat-slab foundation need not be designed to ACI 350.
It is disappointing that a mat foundation would be designed with T&S reinforcing only, but strictly speaking, that does meet ACI 318 minimums.
 
Upvote 0 Downvote
ATSE said:
An exterior equipment mat-slab foundation need not be designed to ACI 350.
It is disappointing that a mat foundation would be designed with T&S reinforcing only, but strictly speaking, that does meet ACI 318 minimums.
Click to expand...

Based on the equipment vendor drawings & foundation calculations, the loads/weights from the filter equipment were not very larger. Same goes for the Chlorine containment shelter.

The 24" thickness of the mat foundation was due to meet elevation requirements to connect to adjacent piping.

Could you please give your thoughts on when the "Environmental Exposure Conditions" mentioned in ACI 350 would apply to the shrinkage and temperature reinforcement for exterior Mat Foundations?
 
Upvote 0 Downvote
An exterior equipment mat-slab foundation need not be designed to ACI 350.
Click to expand...

True. But, what if the client has a requirement that the project be designed to ACI 350? I imagine that to be the case for just about anything designed at a waste or water treatment facility. Or, maybe even just for a client that specializes in those types of facilities. Partially because the pump or pipes could leak and such.
 
Upvote 0 Downvote
@ATSE

I just found this information contained ACI 350 (see image) which provides some clarity.

aci_350_preface_u2hkhz.jpg


The mat foundation in question for this irrigation pump station has nothing to do with "conveying, storing, or treating liquid....". It is just supporting equipment and shelter. I believe this also goes in line with the comments you made about exterior equipment mat-slab foundations.
 
Upvote 0 Downvote
JoshPlumSE said:
True. But, what if the client has a requirement that the project be designed to ACI 350? I imagine that to be the case for just about anything designed at a waste or water treatment facility.
Click to expand...

My original concern was that all concrete structures in a Water/Wastewater Treatment, Pump Station, and/or Lift station had to be designed to ACI 350 requirements (regardless if the concrete structure conveyed, stored, or treated liquid, wastewater, or other materials). This is the reason for the post.

My interpretation is that the preface of ACI 350 says otherwise (see image in my previous post), which lines up with ATSE's post.

JoshPlumSE said:
Or, maybe even just for a client that specializes in those types of facilities. Partially because the pump or pipes could leak and such.
Click to expand...

I am not aware of any documents from the client that specifies that the client has made such requirements.
 
Upvote 0 Downvote
The mat foundations will be supporting filters that contain stormwater & chlorine.

Would it be an issue to the mat foundation if any of the filters were to leak? Would the mat foundations need to be designed to ACI 350 to handle a possible leak issue of the equipment being supported?
 
Upvote 0 Downvote
I think you've answered your own question..that these don't need to be designed under ACI 350 based on the info you've given.

Unless these are intended to provide liquid containment to these filters in case of overflow/spillage. IE is there a perimeter containment wall with water stops at the mat slab foundation joint that would create a basin intended to contain spills? Does the client even want containment to be provided for these elements? I would think no, I've only really come across those containment provisions on industrial sites with nasty chemicals.

If not, sounds to me like these are just standard slab on grade equipment pads, and you don't need to meet any special requirements above ACI 318 requirements. The ACI 350 provisions are really intended to limit crack widths to prevent leakage of liquid containing structures. So if there is no need/desire to provide liquid containment, there isn't really a reason to follow them.



 
Upvote 0 Downvote
Infrequent splash / spill of diluted chlorine is not uncommon. Happens with swimming pools every day.
For higher concentrations of chlorine, then you have trouble no matter what code you use.

ACI 350 can be used, but you have identified a gray area; but most engineers that use 350 would say it isn't req'd here. ACI 318 still has durability requirements that will produce high quality concrete.
And as noted above, if your main heartburn is min reinforcing, going from 0.2% to 0.3% is a small cost.
 
Upvote 0 Downvote
These mat foundation will NOT contain any fluids/liquids. The mat foundations do not need to be Watertight.

Thank you all for your comments!



 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

ronjon322
  • Locked
  • Question
ACI 350-06 Environmental Exposure, Normal vs. Severe
Replies
2
Views
252
ronjon322
ronjon322
RDR89
  • Locked
  • Question
"Side Friction" to resist overturning in shallow precast foundation
Replies
5
Views
251
RDR89
RDR89
C
  • Question
MAT FOUNDATION - Not able to reduce the Soil pressure by increasing depth of Mat foundation.
Replies
14
Views
3K
haynewp
haynewp
Sammut Eng
  • Question
What is Concrete exposure Class XAS?
Replies
1
Views
322
LittleWheels
LittleWheels
DTS419
  • Question
Does ACI 318 Ch. 17 apply to masonry?
Replies
3
Views
858
DTS419
DTS419

Part and Inventory Search

Sponsor

Back
Top Bottom