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RE: Elevated post-tensioned slab cracks

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To answer your questions:
Yes, we are planning on having corrosion investigation done. The building was built in 1992 and it appears that extruded strands were used.
As to the catenary action, I wouldn't endorse it, but it seems that's what is holding the slab and the only noticeable deflection in the slab is the vertical offset in the slab at the 1/4" crack.
Thank you for your comments.
Oshin Tosounian, S.E.
Los Angeles, CA
-----Original Message-----
From: Mark Geoghegan [mailto:structuraltech.vsl(--nospam--at)]
Sent: Thursday, January 09, 2003 4:23 PM
To: seaint(--nospam--at)
Subject: RE: Elevated post-tensioned slab cracks

Now that you state there is water leakage out of a tendon pocket and effloresce you should probably read one of Gail's papers on unbonded PT evaluation - she more than adequately covers issues regarding evaluation for potential corrosion related issue to unbonded PT structures, water leakage and more. This structure may warrant some limited-scope invasive investigation for possible corrosion damage.
Just curious, what year was the structure built? Was it heat-sealed strand, or extruded? If you do not know, you should possibly find out.
To rely upon catenary action as a justification for ignoring the cracks, you may be on your own there - ACI 318 nor UBC code does not address it. Have you noticed any excessive deflections?
Mark Geoghegan
Honolulu, HI