Wood shearwall holdown at elevator shaft

[jacky89]

I have a 4-story wood over 1-story concrete building. The elevator shaft wall is wood shearwall for the top four floors using a Simpson continuous rod tie down system. I'm trying to figure out how to anchor the tie-down into the lower floor 8" thick concrete shaft wall. Uplift on those anchors is about 30k. No way Appendix D will work. I'm thinking of either using a threaded end rebar or welding rebar to an anchor plate and welding the threaded tie down rod to the top of the anchor plate. That way I can use rebar development length in-lieu of Appendix D. Any suggestions? How do you guys normally detail the holdown here?

 

[mark_1155]

Why is block not going up the four floors? Thought it was code.

 

[jacky89]

What do you mean block is not going up four floors? The continouous tie rod goes up four floor. I'm talking about how to anchor into the 8" thick concrete elevator shaft wall at the 1st floor. Using Appendix D, it will not work.

 

[Agent666]

You could cast the rod in with an appropriate anchor plate a decent distance down the wall to develop the load required from the rod, and use overall mechanism of transferring the load to the wall reinforcement, similar to ACI requirements (i.e. Figure 17.4.2.9 in ACI318-14) whereby you can substitute concrete tension breakout capacity with appropriately developed reinforcement into the chunk of concrete being broken out by the rod amchorage. Add additional reinforcement as required to achieve the requirement.

Make sure elements such as bearing on the timber work for that level of load.

 

[KootK]

@jacky89. I think that you're on the right track with your thinking here. I encountered a similar situation recently as shown below. The combination of the ATS welded to the plate after the wall construction and the threaded rod for the hold-down make for a pretty field friendly setup. A couple of additional points:

1) In the situation depicted below, the shear walls were demising walls rather than shaft walls. As a result, the precise locating of the embeds was troublesome. Excess deformed bar anchors and large embed plates were used to compensate for that (cheap insurance). You may actually be in a much better position in this respect because you're dealing with a shaft wall. You can probably just specify plates that fit snug into the corners of the lower shaft walls and, thus, would be difficult to misplace.

2) The ATS plate will encroach into your upper wall sill plates and that would need some consideration. I don't think that would be too big of a problem though. Either cut away what you need to of the sill or add a second, sacrificial sill to accommodate the ATS.

HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me:

http://www.eng-tips.com/viewthread.cfm?qid=456235

 

[mark_1155]

Go to any job site with transfer level and four floors of wood above. You will see masonry elevator shaft walls 40' high well before floors are framed. One reason being they are well rated for fire.
30 kips upflift, gotta have like 3 kips or so per foot going through a plywood shearwall. How does that work?

 

[jacky89]

KootKt, thanks for posting the pic. I actually came up with something similar utilizing the ATS-SBC. Great way to get around the Appendix D restrictions.