Epoxied wood shear wall hold down bolts

[jeffhed]

I have a project with high shear wall uplift. High enough that cast in hold downs such as STHD14 won't work. I have specified HDQ8-SDS3 hold downs with 7/8" diamter rods with embed plates cast in to the footings. The contractor wants to epoxy these instead of casting them in. Typically we use the dimensions of the footing for the area of concrete for the ACI 318 appendix D calculations. Does anyone give any credit for the thickened slab on top of the footing? We are in an area where the frost depth is practically zero. Typically there is a 10" - 12" thickened slab on top of the 10" - 12" footing. My problem is that the proximity to the edge of the thickened slab creates a break out problem, so we embed into the footing instead of the thickened slab. However, then we need to thicken the slab to get the epoxy bond strength to work out. Luckily in this case the footing isn't poured yet so changing footing dimensions is not a problem. Just wondering if anyone gives any credit for the thickened slab on top of the footing versus using only the footing dimensions when it comes to epoxy. Sometimes the increased footing depth for epoxy versus cast in is a pretty substantial difference, 25% - 30% in some cases.

 

[msquared48]

Unless you can develop the bond between the slab and footing, such as casting both monolichically, or adding extra cage steel, I would thicken the footing.

Mike McCann
MMC Engineering

 

[asixth]

Cast-in anchors will always have a higher pull-out capacity than post-installed anchors. Hopefully there is reinforcement crossing the joint between the slab and the footing, otherwise the hold down bolts would need to be anchored into the footing to achieve the required pull-out capacity.