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Re: Threaded Rod Holdowns in Wood Frame Buildings

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I've been using a threaded-rod holddown type of my own design consisting of a
threaded rod with square steel plate and double nut embedded in concrete.
Above the bottom plate, the threaded rod rises centered between two closely-
spaced anchored studs to engage a wood block by means of a steel plate and nut
on the top of the block.  The block is restrained each end to the anchored
studs by 2x vertical blocks nailed or screwed to each anchored studs.  The
plywood sheathing is nailed to each anchored stud.  

This type of holddown eliminates the flexibility due to eccentricity enherent
in a steel assembly that is anchored to one stud.  It may not be practical for
multi-story shear walls because of the lengths needed to develop the 2x
vertical block-to stud connections.  It probably does not accommodate quick-
assembly, high-production type construction -- maybe someone will see a way to
do that.  My projects are all related to repair and strengthening of old
buildings in which nearly every component of the work is special, one-of-a
kind -- one more special item is not a big deal.  

This kind of holddown is being studied by the subcommittee of the SEAOSC
Existing Building Committee that is preparing to present a seminar in November
on L.A City Division 93, the Soft-story Ordinance.  Questions remain
concerning how to compute this holddown system's contribution to shear wall
deflection.

Nels Roselund
Structural Engineer