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Skewed Bridge Deck Reinforcing
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- Subject: Skewed Bridge Deck Reinforcing
- From: Roger Turk <73527.1356(--nospam--at)compuserve.com>
- Date: Thu, 6 Dec 2001 20:46:00 -0500
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 ******* ****** ******* ******** ******* ******* ******* *** * Read list FAQ at: http://www.seaint.org/list_FAQ.asp * * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to: * * http://www.seaint.org/sealist1.asp * * Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: http://www.seaint.org ******* ****** ****** ****** ******* ****** ****** ********
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