Temporarily chipping a slab edge

[itez]

Can you see anything wrong with chipping the edge of slabs to enable hands to enter it and for carbon fiber to be wrapped around beams and then epoxy back (epoxy grout) the slabs avoiding cutting any rebars? Would this be as strong as original slab? Why and why not?

 

[wannabeSE]

FYFE's website says they have a global network of applicators for this type of work (

http://www.fyfeco.com/).

They have done similar work to what you described in the "hook within hoop" thread:

http://www.fyfeco.com/projects/pdf/flyaway parking structure.pdf.

It looks like they cored the slab to wrap a bundle of fibers around the top.

Our office used FYFE once to strengthen an existing shear wall but I was not involved in the project. There are other companies doing this type of work, but FYFE is the only one I know. So I can't say if they are better or worse than other. I know it is expensive.

 

[itez]

I talked to them. They didn't core the slabs. What they did is to wrap the ends of the carbon fiber and insert it to a 50mm hole drilled on beam just below the slabs.

The designer said I can put hole in the slabs every alternative of the strips. Meaning every alternative carbon strip will be wrapped around the beam through the slabs. Just avoid cutting the rebars of the slabs. Then epoxy/grout epoxy it back. This would work isn't it? Isn't it the slabs are connected to the beams by rebars and this is the strength of the tension in the interface and the concrete is not enough for tension anyway? Can anyone forsee any problems with this?

 

[Ingenuity]

We have strengthened RC beams for shear many times. Depending on the available beam depth (below the slab soffit) will determine the necessity to develop the FRP via development into the slab, or achieving a complete "closed-stirrup" equivalent.

We usually do this when full "closed-stirrup" equivalent is required:

1. Scan top of slab to locate top slab rebar using GPR
2. Scan beam web to locate bear shear rebar using GPR
3. Percussion drill (or core drill) full depth holes thru slab from top, missing top slab rebar and beam stirrups.
4. Prep surfaces for FRP
5. Using FRP anchors (diameter and length pre determined for application - they look like a girls pony tail, for example: 3/4" dia x 36" long, in a tight but flexible bundle).
6. Saturate the single continuous FRP anchor and install into holes on each side of beam.
7. Fan out the FRP anchor from underside of slab hole to 8" width over the beam web face, creating a fan pattern.
8. Repeat for required stirrup spacing.
9. Saturate and install FRP sheet layers, as required, in a U-shape, lapping with the FRP anchors on each side of beam web.

Usually a 2-person job to install anchors - one on top of slab, and one below the slab, and use a temporary tie wire, or similar, is used to slip the anchor thru the two slab holes.

Pre-designed FRP anchors are easier to use than manually trying to bundle up FRP sheet and install thru small slots.

The annular space between the drilled holes and the FRP anchor are filled with the same thickened epoxy used with the FRP system.

Usually drill hole diameter is say 1" for a 3/4" dia anchor.

The 90 degree corner created at top of drill hole in slab needs to be slightly transitioned/rounded to avoid the acute angle change.

 

[itez]

Ingenuity. Are you describing the Fyfeco Tyfo Composite Anchor technique? Or is it another brand. Because in the Tyfo Composite Anchor. What the local branch applicator described is they just drilled a 50mm depth of hole (as deep as concrete cover) on each side of the beam and just insert it to the 50mm depth hole. Meaning the girl-like pony tail is not continuous through the slab above but just reaching 50mm (about 2 inches) into the beam. Is this the normal Tyfo Composite Anchor technique? Or do they do like what you did anchoring it around the slab above? Fyfeco Tyfo is worldwide and has branches in many countries so I'd let them do the FRP but they described about putting the anchor into the 50mm depth of the beam but not through it or through the slab above. I think continuous anchor is stronger than partial one.