Attaching Interior Shear Wall Bottom Plate to Post-Tensioned Slab on Grade 2

[TopKnot]

I have some high load interior shear walls I need to attach to a proposed PT slab on grade foundation. (550 PLF) Finishing concrete around placed anchor bolts on the interior of the slab will be a nightmare. I do not want anything nailed or shot into PT deeper than 1/2 in, which is basically nothing.

Can I use construction adhesive? I have looked and looked for data or testing on this scenario, and I can't find it. Does anyone have any references to testing data on this? ICC-ES hopefully? Thanks in advance.

_________________________
TKE

 

[Canuck67]

Just trying to think a bit outside the box. If you were going to continue with PT, would there be any merit to increasing the concrete cover by 1" or 1-1/2" (or more if necessary) to give additional cover above the tendons for the post installed anchors. There would be additional cost for the concrete, however, no covermeter work, no finishing around pre-placed anchors, etc...

 

[msquared48]

It would still not cover the shear wall hold downs, only the intermediate anchor bolts.

Mike McCann, PE, SE (WA)

 

[Onetripper]

I realize that the thread is some what old but I thought i might point you to AISC Design guide 01 "Column Base Plates" (I know its steel and we are talking wood) within this design guide AISC discuses friction resistance in resisting shear forces. I believe that they also site some reference articles that have provided a friction coefficient (steel on concrete) therefore allowing you to calculate the 'conservative' available capacity due to friction. All that being said, I am envisioning you slathering glue to the bottom plate of all of your wood shear walls and I do not understand why you are not concerned about the T & C forces and how to mount your tie downs. Are all your walls in net tension? If they are, I would look at FRP (FIFE web site is good example) to glue down anchors to the concrete.

 

[ChiefInspectorJeff]

Pour a stem wall with vertical dowels and embed into that if the slab is proposed and not poured.Them you finish up to a surface.

Inspector Jeff

 

[keyPitsimplE]

For what its worth, TopKnot, I always use the allowed 0.6 DL on a shear wall to help with my hold down forces. As far as friction for shear anchors, I have not done that. Honestly, I'm not sure if the code speaks to whether or not that is allowed. It seems reasonable (only because you are asking it to be supplemental to require fewer not zero bolts), but I would think your concrete under the sill plate would need to be roughened to provide a predictable coefficient of friction. However, shallow PAF's are probably the quickest route to achieve your shear. I'm not a huge fan of them knowing how they tend to break out the concrete. However, if you have significant dead loads, they could basically be viewed as creating that friction you are wanting even if they do cause break out.

I have looked into using structural adhesive several times and have yet to find a single source with published load values I can use. There are simply too many field variables to make it predictable. Glulams only work because of the tight shop control and regulation. Maybe talk to the FRP (carbon fiber) folks about their epoxy. They rely on it for a predictable adhesion of their FRP to concrete, but they require the concrete to be ground prior to install. HJ3 is a good resource company.

I'm sure you are past all this already, but good luck.

 

[BLSPAM]

You should be able to specify that the tendons need to be moved away from the walls. Temp steel can be located easily and marked on the slab or on drawings during construction. P-t is pretty forgiving. You can also cast sleeves through the slabs at the hold downs for through bolts and other high loads.