Shear-Friction and Waterproofing
Shear-Friction and Waterproofing
(OP)
I have a question on whether the shear-friction section of ACI is applicable when a layer of liquid waterproofing membrane is applied between two concrete placements?
ACI commentary states that when using coefficient of friction µ=0.6, the shear force is resisted “primarily due to dowel action” and the value is confirmed with tests.
From the commentary I assume that some of the shear is resisted by friction of unroughened concrete against the second pour. (in my case it's the joint between footing and stem of the 20ft tall cantilever retaining wall)
I would appreciate any thoughts
thanks
David
ACI commentary states that when using coefficient of friction µ=0.6, the shear force is resisted “primarily due to dowel action” and the value is confirmed with tests.
From the commentary I assume that some of the shear is resisted by friction of unroughened concrete against the second pour. (in my case it's the joint between footing and stem of the 20ft tall cantilever retaining wall)
I would appreciate any thoughts
thanks
David






RE: Shear-Friction and Waterproofing
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Shear-Friction and Waterproofing
I am questioning the applicability of ACI guidance for shear -friction with applied waterproofing. It becomes a standard detail for waterproofing consultants and I'm not sure most structural engineers pay enough attention to it.
RE: Shear-Friction and Waterproofing
For the heel side bars, I don't believe that the bar being utilized for other purposes is the primary concern. Rather, it is the fact that you're only likely to have 50 mm of cover and, when the dowels push against that thin layer of concrete, there is a high propensity for it to spall off.
Now that I think of it, this may not work either. I can't remember the exact clause but I'm pretty sure that ACI has a provision that prevents bars in compression from being used in shear friction. It makes sense as a compressed bar is actually resisting the clamping force that you'd want in the joint. Of course, if you're going with dowel action instead of true friction, perhaps this is not a concern. The "dowel action" statement in ACI is one of my least favorite statement in that entire document. It's an entirely different mechanism from standard shear friction and, really, little guidance is given for its application.
I don't doubt it. Would it be possible to waterproof over top of a shear key? That would fix things up in my opinion.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Shear-Friction and Waterproofing
RE: Shear-Friction and Waterproofing
KootK's "least favourite" statement about dowel action is my "most favourite", because I am not a shear friction advocate, but then he knows that.
RE: Shear-Friction and Waterproofing
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.