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RE: Steel Jacketing of RC columns

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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)destination.com.lb]
Sent: Thursday, May 14, 1998 10:47 AM
To: seaoc(--nospam--at)seaoc.org
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