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Re: Flat Slab Bridge

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David,

        Excuse me for being slow with my response but I had other things on my plate for the moment.

        One solution which may be workable is for you to provide a predetermined movement of the supports under vertical load.  One simple way would be to cast the slab with blocking or shoring between the slab and the interior supports and remove this after the concrete has cured.  This should eliminate the uplift.

        Other effects would include (for dead load only):
1.)    revising all of the reactions,
2.)    reducing the negative moment at the interior support,
3.)    increasing the positive moment at mid span.

        Hope you find this useful.  If not perhaps it will stimulate you to think of some other useful idea.

Regards,

H. Daryl Richardson

"M. David Finley, P.E." wrote:

I've got a project with several C.I.P. flat slab bridges with spans lengths of 13' / 30' / 13'.  With such short end spans, there is uplift at each end of the bridge if a continuous deck is used.  There is too much uplift to simply thicken the deck at the ends. Rather than use simple spans to eliminate the uplift, I'm considering using integral abutments to resist the uplift.  I know integral abutments have been used sucessfully on steel bridges, but I've not heard of them being used on flat slab bridges.  A further complication is that the agency requires 24" sq. conc. piles.  Obviously, they will be much stiffer than the H-piles normally used in integral abutments.  I don't need a lot of movement in order to accomodate thermal expansion/contraction, but I do need some. Any comments, ideas, suggestions? M. David Finley, P.E.
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