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RE: fibers in composite slab

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Andrew –


You wrote, “…explain why, using case study as a valid reason so you don't look like you are just being overly conservative.”  That’s exactly what I’m trying to do.  Do you have any specifics of the slab with the previous employer that had the problems?  Harold’s comment and yours (both of which I respect) unfortunately amount only to, “I saw one of those slabs once that had real problems.”  How can I possibly use that to make an informed decision without knowing any of the details?  It certainly underscores the fact that I need to be cautious in making my recommendation, but doesn’t provide any real evidence one way or the other.  How do I know that our experience won’t be more like what Michelle Motchos had?  (Thank you, Michelle, for sharing your experience.)  Were the problem slabs that you and Harold saw built in the early days of synthetic micro fiber?  Does Michelle’s recent success indicate that maybe the fiber developers have finally developed something that works in the various configurations of steel fibers, macro synthetics, or steel/synthetic blends?  That’s what I need to figure out.


We’re going to talk to the concrete sub to see if they can show us any local projects in which they used fibers in this application.  To me, that would be the most compelling factor in making a decision.


Thanks again for your input, and if you can provide any more information regarding what went into the slab that had problems, so we know what NOT to do, I’d appreciate it very much.


-- Joel


From: Andrew Kester, P.E. [mailto:akester(--nospam--at)]
Sent: Friday, July 11, 2008 10:05 AM
To: seaint
Subject: re: fibers in composite slab


With all due respect, I read this part fo the post aloud to the other engineer in my office for discussion/humor purposes:

"the contractor has suggested that we
could save some money by taking out the welded wire fabric and just
using fibers"


The contractor will actually be making more money, because he will have a repair job in a couple of weeks and you may be getting a bill or worse... I completely agree with Harold. A previous employer did it on one job and they had all kinds of cracking. I think even with composite stl deck and bars over negative regions and at reentrant corners, there are too many other "accidental" tensile forces (in addition to negative bending and shrinkage) in a deck+slab system to not have steel reinforcement, WWR at a min.


My answer would be NO WAY! And stick to your guns but explain why, using case study as a valid reason so you don't look like you are just being overly conservative. And a $100M building they probably have a few more areas of budget concern than your WWR.... I would think that would be a very minor cost anyway.



Andrew Kester, P.E.
Principal/Project Manager
ADK Structural Engineering, PLLC
1510 E. Colonial Drive, Suite 301
Orlando, FL 32803

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