Hold down for a bearing wall question with contiguous shearwall?
Hold down for a bearing wall question with contiguous shearwall?
(OP)
I am designing a wood building. Due to some construction problems we had to remove the sheathing in one of two contiguous bearing/shear walls because contractors were struggling to actually nail the sheathing. Anyways, we were having a discussion at work because somebody picked up one of my details and told me the bearing walls needed hold downs otherwise the nailing would just pull out. Detail is attached. Now my train of thought, as that of my boss, is that the contiguous wall is taking the shear, and the bearing wall isn't exactly connected to the diaphragm as to actually transfer or take the shear forces to the top plates or in that matter to anything connected to that wall. However, I do believe that in flexible diaphragms this is only half true, I mean had this been concrete in the sense that stiffest elements take the most load, I wouldn't doubt the uselessness of a tie down, since proximity and stiffness would pretty much let the sheathed wall handle the load transfer but in the case of wood and flexible diaphragms, I can only be half sure of whether or not the bearing wall takes some of the shear forces, or at least suffers from some deformation that can indeed pull out some of the nailing. and would indeed need tie-downs/hold downs to transfer everything to the foundation.

Any technical expertise on this topic out there?

Any technical expertise on this topic out there?






RE: Hold down for a bearing wall question with contiguous shearwall?
1) Every stacking bearing wall sheathed in any material is going to effectively be an unintended shear wall right up until it fails in some way which may well be vertical separation from the walls below (overcoming of gravity load and nail pullout).
2) If the tied down, intended shear walls in the building are doing their job, the vertical separation in uninteded shear walls should be pretty small, more or less matching that of the tied down walls.
Conclusion:
Yeah, you may well pull the nails out a bit. Not enough to cause any problems though. No hold downs required. And this phenomenon is not unique to bearing walls that just happen to be former shear walls located right next to current shear walls. In fact, it would be more true for stacked walls located further from the intended shear walls because diaphragm deflections would exacerbate wall rotations.
I'm amazed that you were able to get continuous sheathing across the party wall joint. Every time that I've pushed for that, I've been denied. You must be a better architect tamer.
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.
RE: Hold down for a bearing wall question with contiguous shearwall?
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: Hold down for a bearing wall question with contiguous shearwall?
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.
RE: Hold down for a bearing wall question with contiguous shearwall?
RE: Hold down for a bearing wall question with contiguous shearwall?
DaveAtkins
RE: Hold down for a bearing wall question with contiguous shearwall?
RE: Hold down for a bearing wall question with contiguous shearwall?
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.
RE: Hold down for a bearing wall question with contiguous shearwall?
RE: Hold down for a bearing wall question with contiguous shearwall?
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.
RE: Hold down for a bearing wall question with contiguous shearwall?
pfft, that's not even half of my concern now, I was doing the wind analysis by hand and I don't know if my numbers are very off, but even the exterior walls on the third floor do not provide enough shear resistance (most sections are less than 2') and I was thinking on how to approach it, I don't know if it's permitted to have the single interior shearwall take the whole hit or do i extra-reinforce the ext. walls even if they don't really pass by either strength or service, this a regular 3 story and 4 story building [I attached the plan so you can have a look].
The architect restricted us to 2x4's, the ext. walls are already overbearing, the first floor is (3) 2x4's at 12", One of my coworkers said I should run the thing on Woodworks and have it design it by it, but still I'm hesitant on how it could differ so much from my work. I was using TEDDS to do the shear wall analysis/design (either perforated or segmented) but i don't really trust that thing.
RE: Hold down for a bearing wall question with contiguous shearwall?
RE: Hold down for a bearing wall question with contiguous shearwall?
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.
RE: Hold down for a bearing wall question with contiguous shearwall?
Although can you when you're obligated to consider it a flexible diaphragm?
RE: Hold down for a bearing wall question with contiguous shearwall?
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.
RE: Hold down for a bearing wall question with contiguous shearwall?
And then they are not to use sheathing in ext walls, they just expect the gypsum to do all the work. I wouldn't live in this bdg even if i was paid to.