Lapping Pier Reinforcement w/ Anchors

[ToadJones]

I ma trying to determine how deep to extend some anchor rods into a pier stem. The anchors have a very large uplift force.
Is anyone familiar with a good approach to lapping anchor rods with large pull-out forces with pier stem reinforcement.
AISC DG1 covers this but like rest of DG 1 I think it is done so poorly.
Has anyone run into this before?

 

[jike]

Yes, it is a common problem and not very well addressed.

Basically, I fully develop the anchor bolts and fully develop the reinforcing steel and then add the distance between the rods and the anchor bolts. You can also adjust the lap distance by the ratio of area of steel required to area of steel provided. Make sure your pier steel is well confined by ties includin extras at the top of pier per new ACI requirements.

I do not like to hook the pier steel at the top of the pier because it causes problems with concrete placement although it could shorten the lap required.

There was an older article in AISC Engineering Journal that suggested this approach.

 

[strucguy]

This article in Structure Magazine could be of some use to you.

http://structuremag.org/OldArchives/2004/july/From Experience.pdf

 

[ToadJones]

Jike-
I'm glad to hear that I am not in the dark on this by myself.
My problem is I have VERY large uplift or pullout force on the bolt/rod.
Do you use the pullout force on the bolt/rod as the force that you need to develop in the pier steel?
What approach do you use in order to fully develop the anchor bolts?
It is apparent to me at this point that I will need anchor plates on the bottom of the anchor rods to develop my force as a nut alone will not suffice, but do I count on this plate being in bearing alone?

Thanks for your help

 

[ToadJones]

Jike-
I found what seems to be a pretty good source that covers this in:
"Design of Monopole Bases"
By Daniel Horn P.E.

Not sure if I am allowed to post it?

 

[slickdeals]

ACI 318-08 has some good sketches that show the requirements for lapping the reinforcing bar to a headed stud so as to preclude a shear cone type failure.

You can also look at the following article

http://www.bechtel.com/assets/files/TechPapers/design-of-anchor-reinforcement.pdf

 

[ToadJones]

Thanks Slick
You're like my personal helper today