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Re: Grade @ Anchor Bolts

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Nels,

I don't think the second nut on a threaded achor rod would do much for
actual pull out.  About the only reason I could see to use a second nut
would be if someone were worried about the threaded rod un-"threading"
from the nut.  But this worry can be elimnated by either tack welding the
nut to the rod or spoiling the threads rather than using two nuts (or just
use a headed rod).

Scott Maxwell, PE, SE


On Fri, 18 Aug 2000, Nels Roselund wrote:

> Do multiple nuts on a threaded rod improve the anchorage performance?  I've
> done that to develop a holddown into a grouted concrete block wall.
> 
> Nels Roselund
> Structural Engineer
> 
> 
> >> >With a head or nut (but no plate) at the end of the
> >> embedment(s), the mode
> >> >of failure on anchorage devices is a cone-type failure in
> >> the concrete,
> >> >assuming that limit state is the controlling limit state.
> >> The intersection
> >> >of cones often reduced the total strength of the embedment
> >> group, but you
> >> >can still count on a cone-type failure.
> >> >
> >> >With a plate at the bottom of the anchors, the mode of
> >> failure is likely to
> >> >change from a lot of individual cones to one big chunk
> >> (technical term)
> >> with
> >> >a flat bottom. If so, and since this has less surface area,
> >> it reduces the
> >> >strength.
> >> >
> >> >Charlie
> 
> 
> 
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