Horizontal Construction Joints In Conc. Box Culverts
Horizontal Construction Joints In Conc. Box Culverts
(OP)
We have designed a deep cover (44') box culvert using the Box Car program. The box is 8'x 8' with 12" haunches at the interior corners. Wall thickness was selected to accomodate shear and then vertical reinf. selected for resulting bending. We are calling for a construction joint just above the bottom haunch (bending steel will be continuous thru joint), a peer review is asking for confirmation of shear transfer across the joint. Was wondering if anyone has had to supplement similiar program output before, and how. Otherwise manual check of joint shear friction and/or shear across bending steel presumed most applicable?






RE: Horizontal Construction Joints In Conc. Box Culverts
RE: Horizontal Construction Joints In Conc. Box Culverts
Looking at PCA Notes on ACI 318-02, Figure 14.2 shows "Applictions of the shear friction Concept...". Seven applications are shown. All are significantly different from this application. PCA goes on to say, under "Additional Requirements", that shear friction steel should be anchored in confined concrete. Confinement may be provided by beam or column ties, "external" concrete, or special added reinforcement.
RE: Horizontal Construction Joints In Conc. Box Culverts
In reading the commentary, it is clear that 5.8.4 is geared toward the transfer of shear between beams and composite deck, so I can't say if your case is an abuse of the provision.
I would add one other comment about this joint. I always see this joint "stepped" such that the face of the joint is even with the haunch on the outside of the wall and a few inches higher on the inside of the wall. I have always wondered if this became standard practice as an attempt at additional shear capacity or simply as a water stop.
RE: Horizontal Construction Joints In Conc. Box Culverts
AASHTO 5.8.1.4 rules out the use of shear friction for slabs and footings. All the PCA examples involve the interface between two elements, one much larger than the other, intersecting at 90 degrees.
In this case, by "haunch", I believe we're talking about a 12 inch fillet between the bottom slab and the side wall. The intersecting angle would be 45 degrees.
I think the reinforcing crossing the joint could be considered as confined if the longitudinal reinforcing is detailed on the outside, opposite to convention.
RE: Horizontal Construction Joints In Conc. Box Culverts
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Horizontal Construction Joints In Conc. Box Culverts