Concrete Joint between New Retaining Wall and Existing Bridge Abutment

[DakotaKid01]

I am working on the design of a concrete joint between an existing bridge abutment and a new retaining wall. The existing bridge (built in 1964) carries a railroad over a roadway underpass and has a wingwall that extends to become a retaining wall approximately 275 feet long. The roadway is being realigned, so this retaining wall is being removed and I am designing the new one. The existing bridge abutment, wingwall, and retaining walls are basically large gravity walls on piles. The retaining walls we are putting in are t-walls.

My questions are about the details of the joint between the new retaining wall and the existing bridge. I am thinking this should be an isolation joint because of the high potential of differential settlement, so there would be only preformed joint filler and sealant in the joint and no dowel bar as we are including in the expansion joints between the other new wall segments, is this thinking correct? There are is a vertical keyway in the stem and a horizontal keyway in the footing of the existing bridge for the wall that will be removed. Any ideas on what to do with these keyways - should they be filled in with concrete to provide a smooth abutment wall, should keys be included in the new wall and use the keyways, or something else? We also have waterstops in our typical expansion joint, should I put one here as well? Any thoughts would be appreciated!

 

[TehMightyEngineer]

I'm working on a similar project, but a much smaller scale, for single span precast culvert on a private road with MSE wing walls. I'm leaving the wing wall flush to the edge of the culvert with no keyway or dowels. I too am worried about differential displacement causing this joint to naturally want to open up or shift and I don't want to try to restrain it to the culvert. As yours is a much larger scale wall you might have more of a concern with joint movement but perhaps not.

Maine Professional and Structural Engineer
American Concrete Industries

http://www.americanconcrete.com

 

[DakotaKid01]

Yes, joint movement is a big concern, but I don't know of any way to mitigate joint movement that would not potentially damage the existing bridge. I too am leaning toward no keyway or dowels, and filling in the keyway on the existing bridge. Thanks for your comments.

 

[cvg]

you may want to discuss with your geotechnical engineer. for instance, is the new wall footing on cut or fill? If on fill, then what is the expected settlement and due to what load? If on cut, than should you be expecting any significant settlement? what about seismic or groundwater impacts. what is the failure mode if you don't dowel? Is there a good reason to dowel, other than to try and maintain a tight joint?