Return to index: [Subject] [Thread] [Date] [Author]

RE: Alternatives to Post-Tensioning Construction

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Bonded is not a cure all (not to mention that it is cost prohibitive for
buildings in  most of the U.S.).  Some countries do not use it because of
corrosion problems, although these problems have not been as widespread as
those in Canada in the '70s.  The problems arise if the duct is not grouted
completely.  Water can collect in the air pockets left with incomplete
grouting and cause corrosion.  Proper installation and good detailing the
key to either a bonded or unbonded system.  

Paul Crocker, P.E.  

-----Original Message-----
From: Gil Brock [mailto:gil(--nospam--at)raptsoftware.com]
Sent: Wednesday, May 09, 2001 3:15 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Alternatives to Post-Tensioning Construction
Importance: High


Daryl ,

Use bonded post-tensioning tendons.

At 11:23 AM 9/05/01 -0600, you wrote:
>Fellow engineers,
>
>         I am astonished by what I am reading!
>
>         In Calgary during the late 1970s, up to 1981, most residential and
>office buildings being built were of post-tensioning construction.
>There were literally a few hundred of them built.  Serious structural
>problems have since developed with these buildings.  Breaking of the
>cables as a result of corrosion/oxidation is the culprit.  Water
>infiltration of the system seems to be a major contributing factor.
>
>         Fortunately for me, during that period of time I was working for 
> Fluor
>and similar employers, hence, I have no personal involvement in the
>problem at the design stage.
>
>         Presently, there are engineers doing a good "bread and butter" 
> business
>doing annual structural inspections locating broken cables; and there
>are contractors specializing in replacing broken cables.  It's a lot
>like replacing light bulbs or, as one mechanic I used to know years ago
>would say "like fixing Fords".  It's difficult to sell a post-tensioned
>building in Calgary at the present time; most buyers are aware of the
>high cost of maintaining the structure.  I doubt if there has been a
>post-tensioned building built in Calgary in the last 20 years.
>
>         I am curious to know how the corrosion problem is being dealt with
in
>other locations at the present time.  Moisture infiltration has to be a
>problem, especially in coastal climates like Seattle.  I hope the thread
>of the present discussion will extend to that topic.
>
>                                 Regards to all
>
>
>                                 H. Daryl Richardson
>
>Paul Crocker wrote:
> >
> > Of the several dozen residential project I am aware of having been done
in
> > the last few years in the Seattle area, any that were too tall to be
wood
> > were P.T. flat plates.  P.T. typically allows a shallower floor system
than
> > steel framing or mild steel slabs.  The P.T. also tends to reduce 
> deflection
> > problems that can occur in mild steel slabs.  Ducts and conduits can be
> > burried in the slab, which is an advantage overall even if it is not
> > something I enjoy as an engineer.  Openings are not very hard to deal
with
> > if placed *before* the slab is poured.  It becomes more difficult to
place
> > openings afterwards, however, as it is not a great idea to hit cables,
> > although a few will get broken by careless plumbers from time to 
> time.  Jobs
> > that anticipate cutting a large number of openings in the slab
throughout
> > the building's life are typically not P.T.
> >
> > Paul Crocker, P.E.
> >
> > *
> > *   This email was sent to you via Structural Engineers
> > *   Association of Southern California (SEAOSC) server. To
> > *   subscribe (no fee) or UnSubscribe, please go to:
> > *
> > *   http://www.seaint.org/sealist1.asp
> > *
> > *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> > *   send to the list is public domain and may be re-posted
> > *   without your permission. Make sure you visit our web
> > *   site at: http://www.seaint.org
>
>*
>*   This email was sent to you via Structural Engineers
>*   Association of Southern California (SEAOSC) server. To
>*   subscribe (no fee) or UnSubscribe, please go to:
>*
>*   http://www.seaint.org/sealist1.asp
>*
>*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
>*   send to the list is public domain and may be re-posted
>*   without your permission. Make sure you visit our web
>*   site at: http://www.seaint.org

Regards  Gil Brock
Prestressed Concrete Design Consultants Pty. Ltd.
5 Cameron Street Beenleigh Qld 4207 Australia
Ph +61 7 3807 8022              Fax +61 7 3807 8422
email:          gil(--nospam--at)raptsoftware.com
email:          sales(--nospam--at)raptsoftware.com
email:          support(--nospam--at)raptsoftware.com
webpage:        http://www.raptsoftware.com


* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 

* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org