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Re: Alternatives to Post-Tensioning Construction

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Do you by any chance have the web address for PT-Data?

Juan C. Gray

Paul Feather wrote:
> 
> Nicholas,
> 
> I could not have stated it better.  As far as the software is concerned we
> use PT-Data typically (Always current version), have older versions of ADAPT
> and are looking closely at upgrading soon.
> 
> Paul Feather
> 
> ----- Original Message -----
> From: "Nicholas Blackburn" <nblackburn(--nospam--at)fdgoak.com>
> To: <seaint(--nospam--at)seaint.org>
> Sent: Wednesday, May 09, 2001 11:57 AM
> Subject: RE: Alternatives to Post-Tensioning Construction
> 
> > Post tensioning systems have come a long way since the 70's.  A typical
> > modern system includes complete factory-encasement of the strands in a
> > waterproof grease and then an extruded plastic sheath and either of the
> two
> > main types of anchorage available:
> >
> > 1) standard anchors which are bare castings and provide minimum protection
> > to the gripper zone and the transition between the anchor and the strand.
> >
> > 2) fully encapsulated, electrically isolated anchors that are completely
> > covered in a thick plastic coat, have a grease cap over the gripper pocket
> > and a plastic trumpet that fully engages and seals the strand sheathing to
> > the anchor sheathing.
> >
> > A properly detailed PT system will provide excellent performance over the
> > life span of the structure.  In areas where salt exposure is a problem the
> > typical system recommended is the fully encapsulated one.  Further
> > protection can be provided with proper specification of low-shrinkage,
> > high-density concrete containing fly ash and/or silica fume.
> >
> > The durability of any concrete structure, PT reinforced or otherwise, is
> > predicated on proper and timely maintenance coupled with good detailing
> and
> > construction practices.  The reasons previously stated by others on the
> list
> > note the benefits of PT.  I would however try to locate penetrations early
> > on in the design process and only locate conduit parallel with and in the
> > slab. Plumbing should be kept out of the decks for maintenance reasons if
> > nothing else.
> >
> >
> > Nicholas Blackburn, PE
> >
> > ps: On a related note what software does the List use for PT design.  We
> use
> > PT Data typically but I am familiar with Floor and ADAPT PT.
> >
> > -----Original Message-----
> > From: h.d.richardson(--nospam--at)home.com [mailto:h.d.richardson(--nospam--at)home.com]
> > Sent: Wednesday, May 09, 2001 10:23 AM
> > To: seaint(--nospam--at)seaint.org
> > Subject: Re: Alternatives to Post-Tensioning Construction
> >
> >
> > 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.
> >
>


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