Reinforcement in the top of a Pedestal 3

[waytsh]

Section 7.10.5.6 of the ACI code states the following:

7.10.5.6 — Where anchor bolts are placed in the
top of columns or pedestals, the bolts shall be
enclosed by lateral reinforcement that also surrounds
at least four vertical bars of the column or pedestal.
The lateral reinforcement shall be distributed within 5
in. of the top of the column or pedestal, and shall consist
of at least two No. 4 or three No. 3 bars.

When it refers to two "bars" is it referring to one "stirrup" which would have two bars acting on each side of the pedestal to resist lateral forces? Or does it actually mean that we have to try to cram three stirrups in the top 5" of concrete?

If it means two or three stirrups than I am a little concerened that many engineers are not meeting this requirement. (I have seen five in the last few months) Just curious how everyone else is interpreting this portion of the code.

Thanks,

 

[civilperson]

Two each number four bars or three each number three bars in the top 5".Thus, 2" clear #3 1" #3 1" #3.

 

[rulljs]

Just to clarify, if you have 1" of grout on the top of your pedestal, your 2-#4's or 3-#3's should be within the first five inches of CONCRETE correct, or can you count the 1" of grout as part of the 5 inches?

 

[civilperson]

Grout is not part of the concrete. Many applications have no grout and need no grout. The five inch measurement is to top of concrete.

 

[waytsh]

I assume none of this applies if using an unreinforced pedestal. Is that correct?

 

[J1D]

This seems like a new requirement, as the Commentary said: R7.10.5.6 - Provisions for confinement of anchor bolts that are placed in the top of columns or pedestals were added in the 2002 code.

I have a same question as waytch, whether "two No. 4 or three No. 3 bars" means two sets of No. 4 bars or 3 sets of No. 3 bars? A set of lateral reinforcement can be two legs, three legs or more.

If it allows three sets within the top 5". The spacing is a bit crowded. The typical stirrip from top is (as I experienced) 2"+3"+3", then the total is more than 5". It is not good even using 2"+2"+2"

 

[WillisV]

See this thread on the subject: thread167-143033

This provision has actually has been around for a while - UBC, then IBC 2000, then moved to ACI-02 and of course now ACI-05 (referenced by IBC 2003 and 2006 respectively).

I agree it does not seem like this is commonly done as of yet, but it should be to meet code. I have modified most of my standard details to allow the use of either 2#4 or 3#3 ties within the top 5 inches (contractor's option) - and yes the 3#3 becomes very crowded.

 

[majg]

FYI. The canadian code (CSA A23.3-04) added a provision (article 7.6.5.8) for reinforcement in the top of a pedestal as well.
However, the only option given is 2#10M bar size (produced in Canada).

Here, 10M bars are between #3 and #4 bars, but from what I can see 10M bars are the same as #3 bars in the US. Is this right?

 

[miecz]

waytsh

I believe you are right. You don't need to meet this for an unreinforced pedestal. However, you do then need to meet Appendix D.