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Masonry: Epoxy-injection for shear repair?

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Michael:

Epoxy injection of earthquake damaged reinforced masonry walls may
be considered cosmetic since minor cracking does not significantly affect
the future strength of the wall. The micro cracking that may exist
is insignificant.  There is a project by the Applied Technology Council,
ATC 43, that is addressing the issue of earthquake damage repair in
concrete and masonry walls.  Epoxy injection is effective at improving the
stiffness of the wall and restoring nonstructural properties such as water
tightness. There has been testing at the University of California at San
Diego where a full scalle five story masonry wall structure was loaded to
cracking and then repaired and reloaded.  The best contact for information
is Greg Kingsley of Krawinkler Luth Associates of Boulder, Colorado.  He
was involved in the San Diego Tests and a member of the ATC 43 project.

Mr. Spraugue's comments on cement injection are more applicable
to unreinforced clay masonry walls.  Since this project is 10 stories and
built in California in the 70's, I assume that it is reinforced concrete
masonry.

>> Michael Livingston Wrote :
I'm evaluating a 10-story masonry apartment building built in the early
70's where the walls sustained cracking from both the Loma Prieta
earthquake and differential settlement.  About 5 years ago, it was
"repaired" using epoxy injection.  I'm trying to track down which
product was used without much success.  Apparently the criterion was to
fix all cracks you could stick a credit card into and call the rest
"cosmetic".
My question:  Are these epoxy injection methods effective for restoring
shear capacity of masonry walls?
I've talked to some manufacturers who say it is great, stronger than
the surrounding masonry, etc. but who were not forthcoming with test data.
A colleague of mine suggests that for every crack, there are many more
micro-cracks just waiting to open up nearby.  And where there is a
visible crack, the steel may have yielded, reducing the capacity of the
wall if steel was used to resist shear.
Does anyone have any opinions/data on this method of repair? <<


  E-mail from: Brian Kehoe, 26-Aug-1997