Post-installed anchors in stemwall

[shaneelliss]

I have found myself trying to get some post-installed anchors to resist uplift in existing foundation stem walls many times over the years and it is always hard to do. The numbers from ACI 318 App. D just don't work out to where you can resist more than 2500 or 3000 lbs in tension or shear without blowing out the side. Forget about it if you have to resist 3000 lbs in tension and shear. What solutions have you guys come up with where you have to resist more than this?

 

[KootK]

I've bolted steel straps to the sides of concrete stem walls. Desperation is the mother of invention. It can be intrusive to the building envelope system.

With longer wood shear walls, I've argued that the boundary tension and compression loads are shared by two stud packs at the ends of each wall rather than one. If those packs can be separated such that the anchor breakout cones don't intersect, you can cut the demand down a fair bit.

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.

 

[shaneelliss]

I had considered straps to the sides of the stem wall but was worried about corrosion. Do precautions other than galvanized strap or something need to be taken? The top of the stemwall in this case goes down 4' or so but the top is only 6" above grade and it would be hard to regrade the area to not have the straps partially buried. In the past I have had the contractors drill 24" or so into the stemwalls to try to develop the strength of the rebar but I am not sure how effective that really is and the contractors have not liked doing it.

 

[KootK]

Yeah, I've used galvanized steel at least 1/4" thick and reconstituted the building envelope around it where it was there to begin with.

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.

 

[XR250]

In our area, most stemwalls are 4" brick/4" CMU for residential. Try working with that! I usually have them take off a face and epoxy the rod into the footing and then notch the CMU back over the rod.

 

[shaneelliss]

Wow, XR250, that sounds less fun.

 

[BUGGAR]

I've used laser-cut decorative steel plates thru-bolted which worked well and looked classy. Use thick steel and it will last (but leave rust stains).

 

[slickdeals]

There's new documents and testing from HILTI that allows the use of ACI Ch 12 development length equations for reinforcement bars. This document has a lot of information on the theory and testing, including design examples.

http://submittals.us.hilti.com/PIR_Guide/files/assets/common/downloads/publication.pdf