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RE: Skewed Bridge Deck Reinforcing

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I'm sorry but I was curious about how long the bridge is and whether the
control joints really need to be there. Could you not just make it
continuous over the bents and keep the reinforcement square? Of course you
would have to deal with the negative bending moments due to live loads over
the bents.

Calvin Lee, PE

-----Original Message-----
From: Roger Turk [mailto:73527.1356(--nospam--at)compuserve.com]
Sent: Thursday, December 06, 2001 5:46 PM
To: seaint(--nospam--at)seaint.org
Subject: Skewed Bridge Deck Reinforcing


Tripp,

Your reasoning is correct.

The slab is, of course, going to span perpendicular to the girders.  What I 
do in cases like yours is to calculate the area required to span the 
perpendicular direction and then divide it by the cosine of the skew.  I
then 
provide that area parallel to the skew.

It gets really interesting when you have a heavily skewed bridge on a curve,

grade and superelevated.

BTW, don't forget top bars at the corners of the slab parallel to a line 
bisecting the angle.

HTH

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

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:

. >    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) 
. >    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 
. >    The tension force required would be proportional to the horizontal
leg 
. > of this triangle 
. >    The actual force felt by the bars would be proportional to the ratio 
. > of the hypoteneuse over the horizontal of this triangle 
. >    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

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