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Re: Skewed Bridge Deck Reinforcing

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Tripp,

	This does not sound too bad; you probably should do this regardless of
what else you decide to do.  However, why not consider the following as
well?

1.)	There have been M.Eng. and/or M.Sc. theses on this topic published
at University of Calgary (probably under the direction of Dr. W. H.
Dilger, who is an internationally known expert on bridge design).  You
should be able to access these via microfilm at any university library. 
Read one of these to see if you have missed something.

2.)	Why not use a program like SAP2000 to analyze the bridge deck as you
choose to lay it out.  This plus the hand analyses you discuss should
give you the best results.

	Good luck.

				Regards,

				H. Daryl Richardson

Tripp Howard wrote:
> 
> I'm sorry, I know this is going to be difficult to describe without a
> diagram, but bear with me.  We are designing a concrete highway
> bridge.  The support bents for the bridge are at a 26-degree skew to
> the AASHTO girders, which run parallel with the length of the bridge.
> A control joint has to be installed above each support bent.  The
> girder span and width of the bridge works out in such a way that if
> the main deck reinforcing is installed perpendicular to the AASHTO
> girders, as is normally done, each piece would have to be detailed and
> cut to a different length.  This would not only make our job tougher
> but the poor contractor's as well.
> 
> We would like to skew the main deck reinforcing to be parallel with
> the support bents so that they can all be the same length.  The
> question is just how do we size the reinforcing since it is at a skew
> to the actual direction of bending?
> 
> Our current reasoning is as follows:
> 
>   1. Calculate the tension force required to resist the bending moment
>      based on the deck spanning 5-ft perp. to the AASHTO girders
>      (which is in fact what it does)
>   2. Draw a force triangle with the hypoteneuse at 26-degrees and
>      parallel to the support bents and the skewed main deck
>      reinforcing, and the horizontal perp. to the AASHTO girders
>   3. The tension force required would be proportional to the
>      horizontal leg of this triangle
>   4. The actual force felt by the bars would be proportional to the
>      ratio of the hypoteneuse over the horizontal of this triangle
>   5. To get the actual area of skewed reinforcing required, multiply
>      the area calculated in step (1) by the ration in step (4)
> 
> Does this make sense to anyone, or am I off my rocker?  Any comments
> would be greatly appreciated, especially if you've encountered this
> situation before.
> 
> Thanks for the help
> 
> Tripp Howard, EIT
> 
> 
> 
> 
> 
> Tripp Howard
> 
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