Shear tie splices

[mgarza]

A foundation mat that we are reviewing is 12 foot in thickness with reinforcing mats in the top and bottom of the mat. There are additional shear ties at 24 inches on center each way with 180 degree hooks on top and 90 degree hooks on the bottom tying the two mats together. Can the shear ties (#7) be lap spliced, or must they be mechanically spliced?

 

[sdz]

12 foot thick?
Are ties there as shear reinforcement or as spacers? And why are they spliced anyway?

 

[mgarza]

They are shear ties. The supports for the mats will be seperate. The consideration for splices is being made because it is likely the mat will be poured in two placements (>15,000 sf). With the 180 degree hooks on top, it will be difficult to properly orient the hook to engage the bars of the top mat.

 

[mitchelon]

I am no foundation mat expert, but 12 ft??? No one considered to use a different type of foundation after seeing this number.
Are you talking about ties to transfer the shear between horizontal cold joints?

 

[mgarza]

We actually do quite a few, but this is the first with shear ties. Mat is for a 1000 foot tall stack.

 

[VoyageofDiscovery]

Hi mgarza,

Check your code under splicing. #7 don't have to be mechanically coupled, a lap splice will do.

Regards

VOD

 

[csd72]

Some codes wont let you splice shear ties as you can potentially get vertical cracking due to shrinkage e.t.c. The lap wouldnt work so well if you had a crack along it.

If it only has a little cover then you can potentially get breakout of the bars where they have a tendency to straighten.

If it is seismic then check your detailing provisions in the local building code.