Wood shrinkage and hold-down anchors
Wood shrinkage and hold-down anchors
(OP)
We are designing a 5-story wood framed building and are trying to accommodate wood shrinkage that we are estimating to be about 0.375” per floor. Among the challenges is trying to figure out an economical hold-down detail in the lateral-load resisting shear walls. In the past we have used strap anchors at the hold-down locations and have never had any problems (shorter 3-story buildings), but I am concerned that with 0.375” of shortening per floor (with most occurring within the depth of the floor framing) the straps will buckle and be ineffective. We would like to try to avoid using shrinkage compensating anchors. Is there an easy and inexpensive hold-down detail that we could use that will allow the wood to shrink yet still be effective in resisting tension forces in the chords of shear walls? One solution is to have a sufficient number of walls such that we don’t need any hold-downs. We are looking into that.
Also, at what point does wood shrinkage become a problem? I am asking, because we have designed many 3-story buildings and have never had any problems - and we did not give much thought to shrinkage. I would think that the issues of shrinkage within the depth of the floor framing and it's effect on hold-down anchors would be almost the same for 3-story versus 5-story buildings. Of course the overall amount of shortening in a 5-story building would be greater than in a 3-story building.
Thanks in advance for ideas or suggestions that anyone might have.
Also, at what point does wood shrinkage become a problem? I am asking, because we have designed many 3-story buildings and have never had any problems - and we did not give much thought to shrinkage. I would think that the issues of shrinkage within the depth of the floor framing and it's effect on hold-down anchors would be almost the same for 3-story versus 5-story buildings. Of course the overall amount of shortening in a 5-story building would be greater than in a 3-story building.
Thanks in advance for ideas or suggestions that anyone might have.






RE: Wood shrinkage and hold-down anchors
If you use the Simpson ATS system - continuous rods at the ends of the shear walls, they make automatic take-up devices for the system, and I think there are others too. But it is expensive...
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Wood shrinkage and hold-down anchors
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Wood shrinkage and hold-down anchors
However if you are only strapping across the rim joists (I'm assuming a metal strap from post above to post below?) why would it matter how many stories you have? The amount of shrinkage would be the same for each strap at each floor, no? I can see however other continuous components that extend foundation to roof may be a problem but why is the shrinkage different at each floor than in the other buildings?
EIT
www.HowToEngineer.com
RE: Wood shrinkage and hold-down anchors
It matters on the siding details and any masonry on the outside of the structure, not to mention overall internal plumbing, mechanical, and eletrical runs.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Wood shrinkage and hold-down anchors
http://www.eng-tips.com/viewthread.cfm?qid=276910
CSD72 linked
http://www.diva-portal.org/smash/get/diva2:206355/...
Carair linked
http://www.structuremag.org/Archives/2006-6/D-Fex-...
RE: Wood shrinkage and hold-down anchors
http://www.eng-tips.com/viewthread.cfm?qid=276910
http://www.eng-tips.com/viewthread.cfm?qid=282403
RE: Wood shrinkage and hold-down anchors
Nice references Boo.
EIT
www.HowToEngineer.com
RE: Wood shrinkage and hold-down anchors
RE: Wood shrinkage and hold-down anchors
http://www.strongtie.com/products/ats/index.html?s...
RE: Wood shrinkage and hold-down anchors
RE: Wood shrinkage and hold-down anchors
RE: Wood shrinkage and hold-down anchors
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