CIP Retaining Walls...Joints!

[MileHighMadness]

Anyone, I'm presenting working on a tradition CIP reinforced concrete retaining wall. The wall is pretty long, and we have placed contraction joints every 22 feet, and expansion joints every 88 feet per the local client standard. Our contractor (this is a Design/Build project) wants to double those spacings. I understand the joints are for crack control for temperature, shrinkage and creep.

Are the any design examples, technical papers that address this issue?

If I approve/disapprove this request, it would be nice to have a reference.

 

[JAE]

Does this help?

 

[MileHighMadness]

Yes...this helps a lot...MHM

 

[slickdeals]

@JAE:
Which reference book (paper) is that chart from? Is it an ACI publication?

 

[hokie66]

What I have never understood about this type graph is the distinction between grades of reinforcement. For a given shrinkage force, the elongation of the steel is the same regardless of the grade.

 

[JAE]

hokie66 - isn't that because E is the same for all grades?

 

[ron9876]

That is from the CRSI manual. It seems to work in my experience.

 

[RFreund]

Hokie/JAE,

Is there a formula to go along with that chart? I imagine there should be. That might help explain.

EIT

 

[hokie66]

JAE - yes, that is what I mean. Crack control reinforcement controls the width of cracks, and the steel elongation is the same regardless of the grade. So why do they say you can use less of the higher strength steel?

 

[dik]

I typically use 15' to 20' as the spacing for control joints and 60' to 75' for spacing of spacing of expansion joints... I think you (depending on your climate) are probably not far off the mark. I think the contractor's spacing is too great...

Dik

 

[JAE]

Ah....I get your statement, hokie.

 

[RWW0002]

The diagram is referenced in the CRSI manual and ACI 224R as comming from ACI 350R.

 

[JAE]

I think it might be based upon the idea that at the major crack, the bars are yielding and the higher grade of steel will allow a longer space between the joints and "just yield".

 

[JAE]

Yes - RWW0002 is right - it references ACI 350.

 

[MiketheEngineer]

I like Versa-Lok or equal. NO PROBLEMS

 

[hokie66]

If the wall is unrestrained at the top, as for a cantilevered retaining wall, I wouldn't make the reinforcement continuous through open joints as depicted. Use slip dowels to keep the joint planar, but the continuous bars are counterproductive.

 

[RFreund]

Agreed w/ Mike, probably cheaper too.

However I still want to see the equation for that graph, it must exist or did someone freehand sketch that? (laughter)

EIT

 

[JAE]

RFreund - I think you'd have to buy the ACI 350 to see if there is a formula for it.

 

[PEinc]

Try this ACI paper that I found on the internet:

www.PeirceEngineering.com

 

[dik]

and from 350-01... the following:


could not find a formula... easy to create though...

Dik