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RE: Steel Jacketing of RC columns

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UCSD under contract to CalTrans has done a great deal of work on steel &
composite jacking of columns; circular, square & rectangular.  They
looked at "flat / stiffened" jackets as well as eliptical jackets for the 
square & rectangular columns.  Their work in documented in CalTrans
reasearch reports which should be available through CalTrans or UCSD.
When this type of research results in field workable methods they are
incorporated in CalTrans- Memos To Designers.  UCB has done work on steel
jacketing of square & rectangular columns.
UC Irvine has also done composite wrap research as has USC.  The only
vendors not mentioned that I can think of are Dupont & Mitsubishi.

It depends are your design objective as to whether you need to jacket the
entire column or just the top & bottom potential plastic hinge zones.  Is
the objective to add confinement or shear reinforcement?  

It is possible to wrap square & rectangular columns with or without
changing the cross section to elliptical the results are better if the
cross section is changed.  The fiber wrap installation techniques are not
extremely difficult & can be done in a low tech environmnet.  The wrap
strength is a function of the fiber & the number (thickness) of total
wrap.  Any one of the vendors mentioned can provide information, materials  
& service.  

I would recommend against the welded angle iron confinement of an
unmodified square column.  Without changing the shape to round or at least
elliptical you'll either need some substantial stiffening or the
improvement in confinement will be mnimal.

Robert Kazanjy, PE *****I speak for myself not UC-Irvine*****
Senior Development Engineer
Dept of CIvil & Enviromental Engineering

 On Thu, 14 May 1998, Serroels, Chris/SAC wrote:

> I am also not a corrosion expert so I can't unfortunately
> offer a suggestion as to the appropriateness of the unpainted
> jacket.  However, in general what I have seen and read
> with respect to bridge columns (can't imagine why it wouldn't
> also apply to buildings) is that rectangular jackets
> are very hard to make effective without through-bolting
> or external stiffeners.  Otherwise the jacket will not provide any
> significant confining pressure until the concrete has dilated.
> At this point, lap splices will have surely degraded - probably
> failed.
> If I interpret the description of your jacketing concept
> correctly, it seems that you will have gaps in the jacket
> along the sides of the column.  I would be leery of this
> as it will provide space for spalled concrete to escape,
> subsequently reducing the ability of the jacket to provide
> a confining pressure.
> In general, Caltrans has avoided rectangular jackets.  They
> typically install elliptical jackets on rectangular columns.
> What is typically done on building retrofits?  Are rectangular
> jackets common?  If so, what is the anticipated performance
> of a rectangular jacket - how is it justified.
> Chris Serroels, PE
> -----Original Message-----
> From: Sleiman Serhal [mailto:mony(--nospam--at)]
> Sent: Thursday, May 14, 1998 10:47 AM
> To: seaoc(--nospam--at)
> Subject: Re: Steel Jacketing of RC columns
> Germaine, Bob/CVO wrote:
> > 
> > Aberdeen's Concrete Repair (April/May 1996) had a discussion about the
> > system.  They reference the following companies:
> > 
> I have Peter Emmons' Concrete Repair and Maintenance Illustrated, ACI
> SP-160's Seismic Rehabilitation of Concrete Structures, NEHRP's
> Techniques for Seismically Rehabilitating Existing Buildings, ATC-40,
> and I looked into about 2 years of ACI's Structural Journal and Concrete
> International. I could only find one paper on steel jacketing by Jirsa
> but it was a full solid jacket and it did not cover the issue of
> corrosion protection of that jacket.
> What I'm thinking of doing is putting vertical steel angles at the
> column corners and weld steel plates at distances of d/2 then dry
> packing between the steel and the existing concrete then applying two
> coats of PC plaster over lath. This is not expensive and doesn't require
> highly skilled labor. But I need some encouragement or a throw of ripe
> tomatoes from my peers :)
> Thanks,
> Moni Serhal