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RE: Retrofit of Existing RC Spread Footings for Additional Loads

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Dear Mr. Rogers:
I have had the opportunity do to a job exactly like the one yuo are
describing.
This design was done back in 1990 and the only reference I found was a
spanish book called "Patología y Terapéutica del Hormigón Armado", by Mr.
Fernández Cánovas. If you can read spanish I could e-mail you some
information.
Anyway the job consisted in guessing the existing loads and adding the new
loads on a different pier and the do a combined footing analisys using
finite element analisys.
We required some core test from the old concrete slab, and we removed the
existing concrete exposing the rebar, then we applied epoxy (I think it SIKA
COLMA FIX, but now it has a different name), and we casted the new concrete
again. During this process we had to temporary support the existing
structure.
By the way, we could not use piles, and since the work was inside a
petrochemical process plant in function, welding was not allowed.
The only thing you have to remenber is that when you modify somebody elses
foundation, you automatically become responsible of that building. In our
case was the same owner. What about your case?

Ing. Vincenzo Valerio
******************************************************
Enmar Representaciones y Asesorias, C.A.
Caracas, Venezuela.
Tel: 58-2-238-5253 ; Fax: 58-2-237-1101
E-mail: enmar(--nospam--at)etheron.net
******************************************************
-----Original Message-----
De: Robert Rogers <robert.rogers(--nospam--at)woolpert.com>
Para: SEAINT(--nospam--at)SEAINT.ORG <SEAINT(--nospam--at)SEAINT.ORG>
Fecha: Lunes 21 de Diciembre de 1998 02:45 PM
Asunto: Retrofit of Existing RC Spread Footings for Additional Loads


> I have recently searched the SEAINT E-Mail Archive for any information on
> modifying existing reinforced concrete spread footings to carry additional
> column loads.  Although I have found some posts they have provided little
> information which I could extract for useful purposes.  I have also
performed
> a search of COMPENDEX for similar information.  My success has been
limited.
>
> When placing new columns right beside an existing line of spread footings
> (interconnected by strip footings) substructure interferences abound.  In
> one particular case, the spread footing protrude 5 to 8 ft. into a new
> building area (where new columns are coming down).  I am searching for any
> good references (journal articles, practice periodicals, etc.) which deals
> with the design/analysis methodology of increasing the plan dimensions of
> the existing footings to pick-up and carry the new columns loads.  I know
I
> will end up with a combined mat footing which could dictate a slab on an
> elastic foundation analysis.
>
> I am more interested in connection details (new concrete to old, cap
system
> over the existing foundation, etc.).  I have found one article in the
> Transportation Research Record (No. 1476, Seismic Retrofitting of Bridge
> Substructures) which was helpful.  Can anybody else point me in a good
> direction or offer some advice ?
>
> Thanks
>
> P.S (use of piles or caissons cannot be used).
>
>
>