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RE: Subject: Concrete Deck Tendon Repair

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Thank you.  Your response is very thorough.

I have done the walk-through visual investigation of all 6 levels of the
garage including soffits, verticals and decks as well a chain drag to find
the hollow areas in the decks.  

On the second level, where this occurs, there are nine exposed tendons.
They are above one beam (perpendicular to the beam) and range from 12" long
to 21" long.  Two of the nine sheaths are damaged.  

I'm sure the defect was caused because of thin concrete coverage at the high
level of the tendons and the high traffic volume as most of the vehicles
that use this garage pass over this area.

Will you please explain what cracks you mean when you say "grease leaks
through cracks."

I appreciate your input.

Sharon Robertson Bonds, PE
Salerno/Livingston Architects
363 Fifth Avenue, Third Floor
San Diego, California  92101
(619) 234-7471

	-----Original Message-----
	From:	Mark Geoghegan [SMTP:mgeoghegan(--nospam--at)structural-tech.com]
	Sent:	Tuesday, June 05, 2001 5:36 AM
	To:	Seaint
	Subject:	Subject: Concrete Deck Tendon Repair

	sharon,

	a good technical and practical reference is the International
Concrete
	Repair Institute (www.irci.org). they are about to release a guide
	specification on the repair of unbonded PT tendons.

	depending on the age of the parking garage will determine the type
of
	sheathing used, and also the possible extent of damage. could be
paper-wrap
	or plastic, push-thru, heat-sealed, or extruded. this will also have
an
	effect on the repair that is undertaken.

	it appears that you can visually see the tendon (strand and grease,
inside
	the sheath), so this could indicate that the tendon has failed
(corrosion?)
	at some other location, released its tension, and erupted at this
point. OR
	it may just be localized damage and corrosion is not the cause. you
need
	more investigation.

	an investigation should be undertaken and begin with a review of the
	structural drawings and PT shop drawings, and a walk-through of the
entire
	structure. during this initial visual and tactile investigation note
any PT
	strand erupting, slab spalls, leaking joints, grease leaks through
cracks,
	evidence of previous repairs, grout pockets loose etc.

	if this initial investigation reveals corrosion more investigation
is
	prudent to determine more accurately the severity of the damage etc.

	any repairs should involve the owner, engineer and contractor. the
repair of
	unbonded PT is specialized and safety is a concern, so a contractor
with
	experience in such repairs is vital.

	if you describe the preliminary visual observations in a bit more
detail, i
	may be able to assist further.

	HTH

	Regards

	Mark

	------------------------------------
	Mark Geoghegan BE (Hons.-Structural)
	   S T R U C T U R A L   T E C H
	AUSTRALIA    -   GUAM    -    HAWAII
	------------------------------------

	>Subject: Concrete Deck Tendon Repair
	>
	>Story:
	>On an existing parking garage concrete slab, post-tensioned tendons
are
	>exposed at the deck surface because the concrete coverage was a
little
	>thin.
	>At a few locations the tendons' sheathing is damaged.
	>
	>Question:
	>Are there any suggestions or sources of information for repairing
the
	>sheathing?
	>
	>
	>Sharon Robertson Bonds, PE
	>Salerno/Livingston Architects
	>363 Fifth Avenue, Third Floor
	>San Diego, California  92101
	>(619) 234-7471



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