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RE: Hooks on bottom reinforcing steel in pile caps

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Jason,

Thanks for the response. Your explanation sounds
valid.

What confuses me is the implication that you and
several others made (and that intuitively sounds
correct) that a 180 degree hook has better holding
capacity than a 90 degree hook. The thing that I'm
having a problem with is that ACI 318 says NOTHING
about 180 degree hooked bars providing better
structural performance as compared to bars with 90
degree hooks.

If ACI 318 says that both hook types have identical
pullout capacity, how can I tell someone, "No, you
can't use bars with 90 degree hooks. You have to use
bars with 180 degree hooks. Even thought the code says
that they are both identical, I get a warm and fuzzy
feeling with the 180 degree hooks - so that's what you
have to use."

Can anyone list a single report, research study, or
structural failure that would highlight the difference
in structural integrity between bars with 180 degree
hooks and bars with 90 degree hooks?

Thanks everyone for your responses to my question!
This is an issue that I've been wondering about for
several years - but which I've never been able to find
a definitive answer to.

Cliff Schwinger


--- Jason Emoto <jemoto(--nospam--at)reidmidd.com> wrote:

> Pilecaps usually have small span-to-depth ratios and
> behave more like strut-and-tie systems than flexural
> members.  The compression strut theoretically could
> push on the 90 degree hook and try to straighten it
> out so that the anchorage mechanism is impaired.  A
> 180 degree hook would perform better.  This is
> somewhat analogous to a concrete corbel, where the
> primary tension reinforcement requires a positive
> means of anchorage.
> 
> Jason Emoto
> 
> 
> >>> Cliff Schwinger <clifford234(--nospam--at)yahoo.com> 11/05/04
> 08:43AM >>>
> So what does a 180 hook do that a 90 hook can't do?
> 
> 
> 
> 
> 
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