FRP over an existing plastered wall?

Question

FRP over an existing plastered wall?

Backcheckrage (Structural)

(OP)

5 Nov 13 16:10

Hello community,

I have an existing 1940's concrete frame system with infill brick for the entire elevation(two leaf with a 25mm air gap in between). I am considering installing FRP at the base floor to halt potential soft-story effects when the infill fails . The issue is that there is an existing cement plaster render on both sides of the infilled frame. My question is what do you think of installing FRP over the plaster rather than chipping out all the plaster where this will go? I think applyying FRP to the existing brick is always ideal but in terms of shear transfer, im sure i can transfer shear forces from the conc frame to the FRP, the plaster is only bracing the FRP. Thoughts?

jayrod12 (Structural) · Answer 1 · 2013-11-05 17:08:36

How would the shear forces from the concrete frame get to the FRP if you don't attach it directly to the frame. Without designing the plaster to transfer the loads I would shy away from that.

hokie66 (Structural) · Answer 2 · 2013-11-05 17:15:53

You would be depending on two bonded interfaces rather than one. FRP to plaster, and plaster to brick. Perhaps you need to do some testing of the existing plaster to brick bond to assure yourself that it is strong enough. Seismic retrofitting always depends as much on judgment as on analysis, but I would want to be satisfied that the plaster is sound and well adhered.

Backcheckrage (Structural) · Answer 3 · 2013-11-05 21:49:50

I appreciate the feedback. You are all echo-ing my thoughts. Cheers.
I'm just going to have blow out the plaster and install FRP, I can sleep better that way.

Backcheckrage (Structural) · Answer 4 · 2013-11-05 21:49:54

I appreciate the feedback. You are all echo-ing my thoughts. Cheers.
I'm just going to have blow out the plaster and install FRP, I can sleep better that way.

wannabeSE (Civil/Environmental) · Answer 5 · 2013-11-05 21:57:18

Have you considered blowing out the plaster and bricks, and infilling with reinforced concrete? In my area, FRP is an expensive alternative.

Backcheckrage (Structural) · Answer 6 · 2013-11-08 22:58:40

wannabeSE,
Actually my situation is a bit unique in that my client's property is half of an existing structure. If I stiffen up the elevation in the way you are talking about, then i am introducing eccentricity in a big way because i have ability to equally stiffen up the elevation on the neighbor's side of the building. I am only trying to introduce ductility into the existing system rather than stiffen it up and have it attract more load (it's founded on a rock, so ground has stiff period already).

Backcheckrage (Structural) · Answer 7 · 2013-11-08 23:00:42

oops, missed a word: ...I don't have the bility to equally stiffen...

dik (Structural) · Answer 8 · 2013-11-09 22:52:49

Did you check your plaster for asbestos? May not be an issue... it was often used as a binder for plaster at that time period.

Dik

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FRP over an existing plastered wall?