column starter bars

[aladdin76]

In a reinforced concrete buildings project, the contractor casted about 150 foundations with 6 ?14mm starter bars for the columns, at a later stage it was found that the reinforcement in some columns has to increased to 6 ?16mm, the first proposition was to add dowels by drilling and epoxy, then after consulting it was decided that the 6 ?16mm can be just added to overlap with the 6 ?14mm, I checked ACI 318 and ACI 315 and found nothing in regard??
Note : the foundations were designed as Fixed.

 

[countervail]

Are the 16s required to transfer the stress from the moment at the column to foundation junction?

If they are then I don't see what good just lapping them with the 14 starters does.

 

[JAE]

You would have to obtain the bending moment in the column (along with the axial loads) for each load combination and check the 14mm bars at the bottom of the column.

It may be that the 16mm bars were required for the column itself (compression-buckling criteria) and at the base, the moment into the footing is smaller such that the 14mm bars will work OK....

But you have to check the calculations and perhaps perform new calculations to know for sure.

 

[countervail]

As JAE says

 

[csd72]

I suggest you go to the AISC webinar 'field fixes' it has a good section on fixes to anchor bolts.

http://www.aisc.org/content.aspx?id=2164

 

[JAE]

csd72, I think they are referring to reinforced concrete columns - not steel columns with anchor bolts.