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CIP Retaining Walls...Joints!

CIP Retaining Walls...Joints!

CIP Retaining Walls...Joints!

(OP)
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.

RE: CIP Retaining Walls...Joints!

(OP)
Yes...this helps a lot...MHM

RE: CIP Retaining Walls...Joints!

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

RE: CIP Retaining Walls...Joints!

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.

RE: CIP Retaining Walls...Joints!

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

RE: CIP Retaining Walls...Joints!

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

RE: CIP Retaining Walls...Joints!

Hokie/JAE,

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

EIT

RE: CIP Retaining Walls...Joints!

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?

RE: CIP Retaining Walls...Joints!

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

RE: CIP Retaining Walls...Joints!

Ah....I get your statement, hokie.  

 

RE: CIP Retaining Walls...Joints!

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

RE: CIP Retaining Walls...Joints!

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".

 

RE: CIP Retaining Walls...Joints!

Yes - RWW0002 is right - it references ACI 350.

RE: CIP Retaining Walls...Joints!

I like Versa-Lok or equal.  NO PROBLEMS

RE: CIP Retaining Walls...Joints!

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.

RE: CIP Retaining Walls...Joints!

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

RE: CIP Retaining Walls...Joints!

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

 

RE: CIP Retaining Walls...Joints!

It seems to me that the key points to consider are whether the structure is a building, a slab or a wall, water-retaining or -excluding structur, and the structure's environmental exposure. My very recent experience with this topic indicates that the reviewing engineers all assume the worst condition, whether or not they are applicable.  They want the same joint details that they always use for every structure, regardless of the ACI recommendations or the cost.

www.PeirceEngineering.com

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