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RE: PT Construction

[Subject Prev][Subject Next][Thread Prev][Thread Next] James,

Neither prestressing approach can overcome  bad design and/or bad detailing and/or bad construction. Unfortunately, some "designers" would not know the difference between good or bad for all 3 of these and this can lead to problems such as you have mentioned. Bad design guides and methodologies do not help either.

These problems will show up more in PT buildings than in RC where the closely spaced reinforcement often hides the mistakes.

Re inspections, I am of the school where the "experienced" design engineer should understand the processes and do the inspections of his own designs along with proper supervision from the PT companies (this never happens with unbonded PT because the unbonded PT companies do not provide any, they normally only provide materials).

At 10:21 AM 3/05/2005, you wrote:
I know monostrand is pretty popular around the Seattle area for things like multi-story condos, and I've seen it used for deck post-tensioning on a parking garage next to the building I work in. Unfortunately, the post-tensioning was only run in the span direction and the deck almost immediately developed some phenomenal shrinkage cracks in the transverse direction which look pretty ugly for a new structure.
I have never used monostrand post-tensioning, but have been involved in some tank designs and tieback walls using multiple strand tendons that were then grouted. No problems have been reported.
I have read reports of corrosion problems in bonded tendons when the grouting was not properly done, but I have also read reports and heard first hand accounts of broken monostrand. Neither of these PT systems are fool-proof. The sales reps for either system will usually be happy to tell you horror stories about the other guy's products.  I always require special inspection for post-tensioning work with certification of the inspector.
-----Original Message-----
From: gskwy(--nospam--at) [mailto:gskwy(--nospam--at) ]
Sent: Monday, May 02, 2005 4:44 PM
To: seaint(--nospam--at)
Subject: Re: PT Construction

Well, I certainly wouldn't want to name any names, publicly refer to any vendors, or insult anyone,  but if you call up the article below and scroll down to page five,  you see a drawing of what looks darn-like a multi-strand anchorage.
And the pictures I have of these anchorages (in-situ as it were) look darn-like the pictures in this article. 
I took pictures of this garage only because I had nothing else to do while waiting for the shuttle bus.  I have other pictures (from other structures) from litigations.  The beam anchorages always kind of look big and round,  not little and rectangular.
Gail Kelley

-----Original Message-----
From: Gil Brock <gil(--nospam--at)>
To: seaint(--nospam--at)
Sent: Tue, 03 May 2005 09:06:51 +1000
Subject: Re: PT Construction

I have never, in 30 years, used multi-strand tendons in anything other than a very heavily loaded transfer member or a bridge.
I have never used one in a parking garage or other normal building member. The jacks used are standard single strand jacks. If the US PT industry uses multi-strand tendons in this type of bonded member, it is no wonder bonded PT has never taken off there as it has in many other areas of the world.
At 12:22 AM 3/05/2005, you wrote:
>Problems with getting the beams stressed has pretty much make grouted PT >construction a non-viable option for parking garages in this >country. The beam tendons in grouted one-way slab and beam construction >are multi-strand tendons which require a special jack. Usually, the >stressing is done by the p-t supplier, and there are always problems wit! h >getting them out to the site in a timely fashion.
>In other countries, where it is standard construction, grouted PT works >fine. Grouted pt works fine in bridges, too, except the presentations I >have seen on the new cable-stay bridge in Boston were not >confidence-inspiring, as far as the quality of the inspection on >construction of the deck.
>Gail Kelley
Regards Gil Brock
Prestressed Concrete Design Consultants Pty. Ltd. (ABN 84 003 163 586)
5 Cameron Street Beenleigh Qld 4207 Australia
Ph +61 7 3807 8022 Fax +61 7 3807 8422
email: gil(--nospam--at)
email: sales(--nospam--at)
email: support(--nospam--at)
webpage: http://www.r!
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Regards  Gil Brock
Prestressed Concrete Design Consultants Pty. Ltd. (ABN 84 003 163 586)
5 Cameron Street Beenleigh Qld 4207 Australia
Ph +61 7 3807 8022               Fax +61 7 3807 8422
email:            gil(--nospam--at)
email:            sales(--nospam--at)
email:            support(--nospam--at)