What does crack stress in handling a concrete pile really mean?

[RobertEIT]

I checked in ACI318 and PCI Handbook, but can't find such a terminology crack stress in handling a concrete pile. Is this "crack stress" during handling a concrete pile a bogus terminology and the question asking for the "crack stress" during handling a concrete pile a bogus question?

Previously I thought it may imply allowable handling stress of a concrete pile which equals 6*sqrt(fc')+fpc with fpc=0(see <<Foundtion Design --- Principles and Practices>> by Donald P. Coduto. After a second thinking, it seems crack stress and allowable handling stress can't mean same thing. So What does this "crack stress" really mean? Does anybody know?

Thanks a lot for your help!

 

[Lion06]

It seems like you are asking them to check for strength during their handling of the member. I don't know if I would call it "crack stress", but this is common. There are some cases where you want to be sure that it won't crack during handling - a long, slender tapered , precast colimn!! I had the pleasure of dealing with one a couple years ago. It had a kl/r of around 210. They ended up having to prestress it to keep it from cracking during handling.

I would just ask for calcs showing that the strength is ok for however they plan to rig it during erection.

 

[RobertEIT]

Thank you StructuralEIT for your response.

Suppose in a test you were asked to answer how many psi the crack stress in handling a concrete pile is and the only information given to you is the concrete fc'. Would you think it is a bogus question?

 

[Lion06]

No, I would use 7.5(f'c)^0.5. That being said, cracking is not usually an issue during handling because you expect cracking in service (typically, not always). You are typically only concerned with strength during handling - again, unless cracking is a concern for architectural reasons or for prestressed concrete.

 

[PEinc]

This question should be in the Concrete Pile Engineering forum.

 

[RobertEIT]

PEinc:

It seems very few people visits the Concrete Pile Engineering forum and even less people responds to the question, therefore I posted here seeking for help.

StructuralEIT:

Yes, my first reaction is also to consider fr=7.5(f'c)^0.5 as the crack stress. But the maximum value it gives you to select is 6(f'c)^0.5, the other values given to you include
1.5(f'c)^0.5, 3(f'c)^0.5, and 4.5(f'c)^0.5. None of 7.5(f'c)^0.5 as your choice.

I am thinking could it be possible that it is asking for the permissible stress at transfer which will equal 3(f'c)^0.5? But I am still suspect where the word "crack stress comes from. Any thought?

Thanks!

 

[Lion06]

Is this a prestressed member?

 

[RobertEIT]

It does not give any information on this either. It just ask what is the crack stress in handling a concrete pile with fc'=xxxx.