CIP Box Culvert Construction Joints

[engjg]

Working on a two cell 8ft wide x 7ft high CIP box culvert design. In addition to construction joints at top and bottom of walls, contractor wants construction joints adjacent to web in top & bot slab for phased construction to accommodate flow diversion. Anyone have recommendations on detailing/design of these joints including consideration towards shear transfer. Shear friction justification? Keyway? Haunch?

 

[JoelTXCive]

Let me check. I think I have some research on this.

Just to confirm. The contractor wants to put a longitudinal construction joint into the bottom/top slab running along the length of the barrel?

Or, are you saying the contractor wants to cast the first barrel; and then come back and cast the 2nd barrel?

 

[engjg]

? Yes and yes. See attached sketch should clarify sequencing.

 

[JoelTXCive]

I apologize. The research paper I have on culvert joints just addresses the normal joints that are transverse to the cross section. I attached it here, but I did not see any mention of the joints you are talking about. It's an Auburn student's master thesis...

https://etd.auburn.edu/xmlui/handle/10415/3334

Link

I did think about it though.... There is no difference in the joint your contractor is proposing and the normal wall joint at the intersection of the stem and base of a retaining wall. A retaining wall sees its highest shear and moment at the base; and there is almost always a construction joint there. How is that loading any different than the gravity load on the top of your culvert?

You could do a keyed joint or just pass the shear through shear friction.

Someone else can chime in if I am missing something.

 

[TehMightyEngineer]

I don't see anything wrong with it either. As Joel said, roughen and shear friction or a shear key joint.

You'll have less clamping force than the joints on the walls but should be more than sufficient to always provide clamping across the joint. The shear there will be highest due to vehicle loads and that is worth some extra consideration to ensure the joint is reliable (FIU bridge) but I wouldn't say it's a show stopper.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL, CO) Structural Engineer (IL, HI)

 

[1ManWolfpack]

We do this all the time in NC. There's usually plenty of reinforcement passing through that joint that you should be able to just handle the shear through shear friction, as others have said. Also you may be able to eliminate a pour if you wait until all of your walls have been cast, and then cast the entire top slab in one go. If you do this, however, make sure your 107 bars (from your sketch) have adequate moment capacity to handle the temporary condition where you have water in only a single barrel and no top slab. Hope this helps some.