low breaks for piers 3

[structuralaggie]

The 56 day break for the bell-bottomed piers on one of my jobs came back a little over 2100 psi. I had specified 3000 psi, however I was not privileged to see the mix design before hand, and now the builder wants me to come up with a fix or write a letter that says everything is ok.

While I am not all that excited about the situation, the reality is the piers are essentially only in compression and even at 2100 psi, they are still much stronger than the soil they bear on. Is there anything else I should be worried about? The only "fix" I can think of is to retro-fit in a bunch of piers, but this would be ugly, and not even really an option on the interior piers. Any thoughts?

 

[csd72]

Check the bending in them assuming maximum allowable construction placement tolerance (I think this is about 4").

Also check the bearing stress at the top of the pile (under the baseplate or whatever).

csd

 

[JAE]

Agree with that....

and I'd add that you have essentially followed ACI 5.6.5.

Since your f'c is now at 2100 psi, you have done the proper next step and checked the structure capacity at 2100...if it is OK at that level, then nothing more needs to be done if you are satisfied with that lower strength level.

 

[GregLamberson]

structuralaggie

On a related note, rather than writing a letter stating it's okay, I would ask the contractor to prepare a deviation request and then if you're happy with everything, approve that request.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[structuralaggie]

Thanks for the tips. I especially like asking the contractor to request a deviation from what I specified so that it looks like it was his idea.

 

[BigH]

The contractor is in non-compliance with the stipulated requirements of his contract - correct? Then before I would start checking anything - issue a non-compliance. It is then HIS responsibility to provide one or more solutions. He may request a relaxation. If this is the case, then you can check out the problem - but, in my view, you should then bill the owner for the time it takes you to check out the non-compliant work (and document it as such). The owner then would have the recourse to recover the costs. I have seen the concrete cored, as well, in the past and tested. Again, the mode of making the work right rests with the contractor - if he is non-responsive to his obligations, then other recourse through the commercial terms of the contract would then come into play. It never ceases to amaze me that engineers are so willing without hesitation to assume (or appear to assume) responsibility in looking for "ways out" when it is clearly the contractor's responsibility to make the first move after a non-compliance.

 

[structuralaggie]

BigH - believe me I'm not going to assume any responsiblity for the contractor not installing the specified concrete. The GC is taking the same stance with his concrete sub. And yes, I am supposed to be paid for my work, but I have already told them that I need to be paid up front. All around it is a bad situation. I am going to take your advice and let them make the next move.