How best to route top reinforcement around shear key pockets?

[MrFurleyEIT]

I am designing shear lugs for my base plates on my mat foundation. The base plate is sitting on top of the mat foundation and the shear lug and shear lug pocket where they do occur (around vertical bracing areas, primarily) will interfere with the top reinforcement of my mat.

To get a feel of the situation, my base plates are about 15x15 and about 2 inches thick on a 1-1/2 structural non-shrink grout. The shear lug runs the length of the base plate and is 6 inches deep from the bottom of the base plate (i.e. 4-1/2 inches into the mat) and about 1 inch thick. The mat itself is about 18 inches thick. I generally use the minimum 4 1" diameter anchor bolts with embedment of about 15 inches deep.

My question is about the top horizontal reinforcement crossing the shear lug pockets. What is the best way to handle the horizontal reinforcement? I am thinking that one of the ways to handle this is to treat the shear lug pocket as an opening on my mat, and stop the horizontal reinforcement just short of the shear lug pocket and bend it downwards. Then provide additional reinforcement around the perimeter of the shear lug pocket and also below the pocket itself. Please provide your opinion whether this is feasible or not. What is the best design approach, or how do I design it?

Is there any other better method to design the reinforcement around the shear lug pocket? Does anyone know of a method so easy that a caveman can do it?

How about running the reinforcement through the shear lug pocket itself and have it embedded in the structural non-shrink grout? Has anyone done this before, and is it a practical solution?

What about base plates with two-way shear lugs? I am guessing the approach above, if acceptable, is similar to the one-way shear lug, right?

Please provide your thoughts and suggestions, and thanks in advance.

 

[jike]

Two approaches come to mind:

1) Terminate the reinforcement at the pocket and provide supplemental (additional) bars (minimum of 2) each side of the pocket equal to 1/2 of the reinforcement terminated by the pocket.

2) If the pocket is not too big, just flare out the continuous reinforcing around the pocket on all sides. Do not exceed a 1:6 angle.

 

[shin25]

I agree with jike. This is the way I have seen done in the construction industry.

 

[csd72]

Make sure the pocket is not at the point of maximum moment. If it is and the pocket is in the compression area then double check the moment with the reduced effective compression width.

csd

 

[MrFurleyEIT]

jike and shin25, thank you very much for your quick responses. You basically confirmed what I had in mind, but you provided verification of what had been done before and the numbers certainly helped and gave me a feel of what I need to do.

csd72, you brought up a very interesting and important which I had overlooked. See, four heads are better than one! Could you please elaborate more on it, esp, on the reduced effective compression width, and provide examples, if possible?

Thank you so much, everyone.

 

[csd72]

I usually ignore the contribution of the grout. So you reduce the effective compressive width locally by the 15" (pocket) and calculate based on that.

It should only make a few % difference but if you are right on the capacity then it may be significant.

csd