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Re: Steel Fibers Replacing Structural Reinforcing?

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Johathan:

To my knowledge, there are no code provisions that directly permit the use
of steel fibers to completely replace reinforcing steel in structural
concrete.  I _KNOW_ that ACI committee 318 has not been convinced that
fibers can replace reinforcing steel required for structural concrete (at
least that was their position while I was an ACI staff member).  The only
use that I have seen to date for fibers was either in non-structural
concrete (i.e. slabs-on-grade) or in addition to the primary rebar
reinforcing.

Thus, if used as replacement for primary reinforcing, then it would seem
to me that this would fall under the "providence" of the alternative
materials provisions in the IBC/UBC/etc.

This is not to say that there has not been research in the area.  I know
that there is lots of research looking into using fibers (steel and
otherwise) as primary reinforcing.  It is just as matter that it has not
become widely accepted by the code developers and others.

I would agree with Jason's suggestion of looking at it from the aspect of
being plain structural concrete (i.e. no rebar needed).  To me, that is
the only logical choice that would place you within the "letter of the
law" so to speak and still be able to use fibers.  But, then be careful,
as I believe that the use of plain structural concrete is limited based
upon which seismic zone you are in.

HTH,

Scott
Adrian, MI

On Thu, 17 Jun 2004, Meyer, Jonathan wrote:

> I am currently designing an industrial facility a portion of which is a
> rack supported building. We designed the mat foundation to support this
> building and came up with an 18" thick slab with two layers of #7 bars
> @12 OCEW. One of the concrete contractors has asked a steel fiber
> manufacturer to value engineer the reinforcing to determine if they can
> do it with steel fibers instead of the reinforcing specified. There are
> also slab on grade and elevated composite slabs in this facility. That's
> the background, here is my question - Has anyone replaced structural
> reinforcing with steel fibers and are there any standards related to
> such a replacement?
>
> The steel fiber representative called me and told me that they would
> have to increase the slab thickness to 19" and use 60# of fiber per
> cubic yard. He invited me to use their software to "verify" the design.
> I guess I am a bit skeptical about using someone else's software that
> has a vested interest in the outcome of the design to produce a design.
> I told the steel fiber manufacturer that they would have to take full
> responsibility for the design and produce sealed stamped plans if they
> wanted to change my designs to steel fiber for the mat slab of the rack
> supported building. As far as the slabs on grade are concerned, I feel
> that if the client wants to use steel fibers in those areas that would
> be fine as long as they understand any limitations of the fibers.
>
> Any input would be greatly appreciated. Thanks for you assistance.
>
> Jonathan Meyer
> Webber Smith Associates
>
>

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