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Re: Location of footing reinforcement

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The longitudinal reinforcement is sized for temperature and shrinkage
control in the longitudinal direction.  It is placed in the bottom of
the footing to provide sufficient support for the tranverse
reinforcement.  I would think you could provide the steel anywhere in
footing provided you have proper clearanced; however, if placed in the
bottom of the footing the steel will also act as bending reinforcement
should you get any deflection in longitudinal direction.  

I do not concur with your idea of placing the concrete 2" shy from the
top of the footing, placing the steel, and then completing the pour. 
You would be asking for a cold joint between the two pours.  I also
think you would run into problems trying to splice the steel in wet

Along the same lines, why did you not question the placement of t&s
steel in the bottom of a one-way slab??

Richard Lewis wrote:
> Let me ask an engineering judgement question which I hope sparks a lot of
> controversy and causes many different opinions to be brought forth.
> A week or so back someone had posted a question regarding minimum thickness
> of a concrete footing.  It reminded my of a engineering philosophy question
> of where to locate the longitudinal reinforcing in a continuous strip
> footing.  I think traditionally we locate longitudinal reinforcing in a strip
> footing at the bottom.  My question is WHY?  What is the purpose of
> longitudinal reinforcing?  Is it to:
>   -span across local settlement of the soil?
>   -tie the wall footing together to prevent
>      it from pulling apart, somewhat similar
>      to a bond beam at the top of a wall?
>   -somehow provide strength to the footing element?
> Why does it have to be at the bottom to provide these functions?  Wouldn't it
> make more sense to put it at the top?  For strength, a larger load can be
> supported over a slight settlement using negative moment at ends then a
> positive moment at the middle.  It would be easier to place the reinforcing
> and not worry about bottom cover if the contractor were able to pour the
> concrete to say 2 inches from the top of footing, lay the reinforcing in
> place and then pour the rest of the concrete.  What difference does it make
> if the reinforcing is top or bottom in regards to shrinkage?
> I look forward to reading many different opinions on this topic.
> __________________________________________________
> Richard Lewis, P.E.
> Missionary TECH Team
> rlewis(--nospam--at)
> The service mission like-minded Christian organizations
> may turn to for technical assistance and know-how.