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CSA A23.3 Interface Shear Transfer - can we interpolate?

CSA A23.3 Interface Shear Transfer - can we interpolate?

CSA A23.3 Interface Shear Transfer - can we interpolate?

(OP)
Re: CSA A23.3 Clause 11.5.3 Interface shear transfer: Do you think that it might be acceptable to linearly interpolate the values of “c” and “μ” for surface roughness amplitude between 0 mm (c=0.25, μ = 0.60) and 5 mm (c=0.50, μ = 1.00)?

For example, if we had roughness of say 2.5 mm full amplitude, might we take c = 0.375 and μ = 0.80 ?

RE: CSA A23.3 Interface Shear Transfer - can we interpolate?

It seems like a reasonable approach but I wouldn't do it personally. I'd either get the 5 mm amplitude or settle for the smooth concrete values. What's the situation?

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: CSA A23.3 Interface Shear Transfer - can we interpolate?

I'm with Kootk in not doing it, but I disagree about it being reasonable. Short of cast against plastic or another "mirror finish" concrete surface condition, pretty much every concrete surface is +/- a couple of mm. Those are covered by the smooth case, with 5mm being the minimum specified amplitude.

It needs to be measurable, achievable, and reliable. Existing surfaces need to be tight and free of dusting or lose material. Everything I've seen that would have qualified as a 3mm or so existing had lose and or friable surface material.

Anything less than 5mm (I'm seen 3mm specified many times) is simply not realistic. I often specify +/- 8mm and design to 5mm. But then again, I think history has shown me to be a fairly cautious engineer...

RE: CSA A23.3 Interface Shear Transfer - can we interpolate?

(OP)
CELinOttawa - ok I take your point. Do you have any way of actually checking it on site? Which of the ICRI plastic samples swatches (they are numbered 1 to 10) corresponds to 5 mm full amplitude?

RE: CSA A23.3 Interface Shear Transfer - can we interpolate?

When in doubt, or in need of ammunition to force further chipping, I check with a pin plate gauge. Those roughness sample plates are really only suitable for architectural finish in my opinion.

RE: CSA A23.3 Interface Shear Transfer - can we interpolate?

(OP)
CELinOttawa - Last night (the work is being done nights) the inspection company did use what I suppose is what you call a pin plate, together with a straightedge, and then subtracted the thickness of the pin plate. The full amplitude came out to be much more than the required 5 mm although it depends on how you place the straightedge. I notice that one of the product manufacturers refers to the roughness sample plates and correlates it with 6 mm, and the roughness they require, so that seems to indicate that they are being used for more than architectural finishes, although I suppose that I should buy the ICRI document that goes with the samples to see what it says....would you have that?

RE: CSA A23.3 Interface Shear Transfer - can we interpolate?

If you don't have access to a pin plate, just use a vernier caliper's depth probe and a short ruler. You should uae an averaging plate not more than 2" wide. The result they got was likely high because they used too large of a flat edge, which doesn't check the local, but rather more global, roughness.

I will try to put my hands on the Quebec Ministry of Transport roughness checking procedure. They are the only authority I know to have published a formal test procedure.

RE: CSA A23.3 Interface Shear Transfer - can we interpolate?

(OP)
CELinOttawa - ok, much appreciated. (In my prior post, I should have said they subtracted the thickness of the straightedge; I think the length of the straightedge may have been too much).

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