Design of Dowels Across Expansion Joints

[mattaem]

I am designing a new slab foundation to be poured adjacent to an existing slab foundation with an expansion/isolation joint separating the two. The issue is there will be loading going from one slab to the next and I would like there to be shear transfer between the two so that as the load transfers the two slabs will deflect together. I plan to use smooth dowels so that the shear can be transferred but that the two slabs can still expand and contract dependent of each other. I am aware that ACI 360R-06 provides provisions of how many dowels and what size, unfortunately it doesn't give any guidance on how to calculate this information. If both sides of the dowels where embedded in concrete I would use the shear friction models where the steel across the joint yields, however since these bars are designed to slip I do not feel this applies. Does anyone have any advice, manuals, papers, etc. that describe how to calculate a number of bars needed? Sometimes this problem occurs where the two concrete members aren't slabs so being able to calc the shear transfer would be awesome.

Thanks,

Matt, MS PE

 

[dcarr82775]

Use the shear strength of the steel itself (or breakout of the concrete whichever controls). If there is an actual gap between the slabs then bending of then bending of the dowel also would need to be checked.

 

[hokie66]

Agree with dcarr, but would question the need for a gap between the slabs at this level. The new slab will shrink, so will make its own gap.