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Re: Steel Reinforcement Elongation Limit

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This is true....

I am however trying to determine what would be an appropriate limiting
elongation when applying composite plates to the underside of beams for
flexural strengthening.

Composites have no plasticity...they are elastic to failure....

Plates can be manufactured to have the same modulus as steel (oops...is that
29ksi or 30ksi ?).....However, they are elastic up to failure, so it would
be nice to have an understanding of the maximum elongation that will keep
the underlying concrete from separating from the existing steel
rebars....precisely to avoid catastrophic failures..


jim


----- Original Message -----
From: "Scott E Maxwell" <smaxwell(--nospam--at)engin.umich.edu>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, July 25, 2000 8:28 PM
Subject: Re: Steel Reinforcement Elongation Limit


> As well, I believe the intent of the ACI code is that the development
> length provided in the code would fully develop the bar.  This would mean
> that the bar would reach yield stregth and "plateau" while elongating.
> That is to say that no matter the elongation, the "bond" between the steel
> and concrete would never "break" allowing the bar to pull loose.  Thus,
> the bar would either fracture or the concrete would crush before the bar
> would pull loose.  This is all predicated on proper developement of the
> bar.
>
> I could be wrong, so maybe someone more knowledgeable will chime in...
>
> Scott Maxwell, PE, SE
>
>
> On Tue, 25 Jul 2000, Roger Turk wrote:
>
> > ASTM requires 11 to 12 percent (min.) for Grade 40 steel, and 7 to 9
percent
> > for Grade 60 steel.
> >
> > Since this is much beyond the cracking strain of concrete, the concrete
will
> > crack and go along for the ride.  (Take a piece of paper and cut one
edge in
> > parallel strips and glue a rubber band across the strips.  Pull the
rubber
> > band and see if the glue comes loose.)
> >
> > At these strains, deflected shape becomes a part in determining the
capacity
> > of the structure with the structure behaving like a cable supported
structure
> > more than a flexural member.
> >
> > We (at least *I* do) want our structures to look like a sway-backed mule
> > before it collapses.  I do not want strains limited so that collapse
comes
> > suddenly and without warning.!
> >
> > A. Roger Turk, P.E.(Structural)
> > Tucson, Arizona
> >
> > Jim Korff wrote:
> >
> > >>The steel reinforcement "yield point" is at an elongation of .002
(0.2%)
> >
> > Does ACI Code give a maximum permitted elongation for internal
reinforcement
> > ??
> >
> > (For DIN it is 0.5% and for the Euro Standard it is 1.0% )
> >
> > Are there any papers or research on this subject -maximum elongation to
> > avoid steel/concrete bond failure ??<<
> >
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