Ties question 1

[delagina]

If you have a concrete pedestal connecting to footing. Do you provide extra tie?
If yes, what is the reason behind this? I see footing details with and without this extra tie.

 

[JAE]

I never have. I don't believe a tie there would do much. And I've never seen it done that way.

Ties are to control bursting of column sections from axial loads (think of the vertical column bars buckling outward).
Inside the footing there is adequate resistance to any (if any) outward buckling of the vertical bars.

 

[hokie66]

That tie is sometimes provided for construction purposes, i.e. maintaining the shape of the cage. But it has no structural function.

 

[RHTPE]

Hokie is correct - the tie within the footing is used to help hold the vertical bars (or dowels) in position for the pier or column to be placed later. It's not required for structural purposes. If the contractor uses a more accurate template (ha!), it can be omitted.


Ralph
Structures Consulting
Northeast USA

 

[msquared48]

NO.

Mike McCann
MMC Engineering

 

[JAE]

Usually the bottom hooks are simply tied into the bottom mat of footing rebar and the ties above (in the column are there to hold the vertical bars shape in place.

 

[dik]

Often see it as Hokie has described... keeps the dowels same as the column/pier above...

Dik

 

[Hokie93]

Such ties could be required for seismic design purposes. ACI 318-08 chapter 21.12.2.3 requires ties (transverse reinforcement) within a footing or foundation member for columns or boundary elements of special structural walls that have an edge located within h/2 from the edge of the footing, where h = the footing thickness. This only applies to Seismic Design Category D, E, and F for ACI 318-08. If your pedestal doesn't fall into the requirements of ACI 318-08 chapter 21 then I agree with the others that the ties are not required and/or serving a useful structural purpose.

By the way, if your pedestal is resisting any significant moment, the performance of the joint will be greatly improved if you turn the longitudinal bar hooks (the 90-degree hooks) such that they are pointing towards the centerline of the pedestal.