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Re: Skewed Bridge Deck Reinforcing

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If the bridge is for a paticular agency (DOT, etc.) you also need to check with them.  Many have paticular detailing requirements/preferences.
M. David Finley, P.E.
Lake City, FL  32025
----- Original Message -----
Sent: Thursday, December 06, 2001 6:09 PM
Subject: Skewed Bridge Deck Reinforcing

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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