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Re: FRP reinforcement

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I was referring to CFRP actually (Carbon Fibre). I agree with the EI comment. I don't think it will accomplish the required stiffenning however a slight increase will be obtained because they are installed on the exterior surfaces of the slab and get the additional lever arm from the concrete cover thickness.
Anybody want to tackle the question about the amount of slab jacking..or the installation of drop panels in an existing slab? BTW there are several floors above the level of concern that will not be evacuated.



David A. Handy P.Eng.

----- Original Message -----
Sent: Monday, October 30, 2006 10:28 PM
Subject: RE: FRP reinforcement

What is the FRP?

To me FRPC is Fibre Reinforced Polymer Composite. Glass fibres are stiffer than steel, whilst Kevlar fibres are tougher than steel, not sure where carbon fibres lie. The articles I have read on FRPC have generally concerned using FRPC sheets to strengthen reinforced concrete bridges, either wrapped around columns or applied to sides of beams. Purposes being to either repair damaged concrete, allow for increased traffic loading, or meet earthquake requirements.


Not sure how FRPC would help reduce deflection of a slender slab. Need to increase EI, and I don?t believe it will have much effect on that!



Has anyone used FRP reinforcement to strengthen existing structural slabs. I am dealing with a slab with a significant deflection (3"+/-) and it is about 15 years old. I am concerned about the amount of jacking that could be done prior to the installation of the FRP. I am thinking that we could only jack the slab back up by the amount of the "immediate DL deflection" which could be only about a 1/4 or 1/3 of the long term DL deflection. Any thoughts on procedures?  I am also not sure that this is the answer to the problem; it was the suggested method.  I seemed to remember reading that the stiffness is not increased as much as the strength is. Is there any way to get the slab back to level condition without the use of toppings? 


I also have other concerns about the strength as the area where there is a problem is the area where there are no drop panels. Has anyone on the list ever added drops to an existing slab. I am mulling over what kind of connection/joint there would have to be between the new and the old.




David A. Handy P.Eng.