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RE: Tilt Up systems

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In Romania they used to build five stories apartment buildings out of
prefabricated reinforced concrete panels.  They NEVER used tilt-up systems,
not in this type of buildings, or in any other type.  This idea is unknown.
The basement was 20 cm (8") monolithically poured concrete walls and the
slab 12 cm (4") thick as well poured monolithically.  The height was about
1.5 - 2.0 m (5'-0" to 7'-0") and it was only used to run pipes (heating,
sewers etc.)
The interior walls and the slabs were 12 cm (4") thick reinforced concrete
panels, prefabricated in factory, and trucked at site.
The exterior panels were 27 cm thick (10") tri-layered;  the inner layer was
a structural layer, the middle one insulation (polystyrene) and the outer
layer just a protection layer; these panels also prefabricated in factory.
The reinforcement of the panels was a combination of independent bars and
welded wire mesh.
The connection between panels was realized with 15 mm dia. bars @ 30 cm
(12") and the edges of panels was notched at every 30 cm (12").  At erection
time the panels were shored, the bars were welded and the concrete was
poured to infill all notches.  The stairs were also prefabricated.
The prototype projects were done in a central institute and were designed to
be applied in the whole country with small variations, according to local
seismic conditions and architectural requirements/design.  (In Romania the
seismic zones span between 6 and 8 on Richter scale).
For a particular building, the design consisted in changing the shape of
balconies, (or maybe adding a balcony or completely deleting one), design of
the basement and footings, etc.  In other words, the main structural idea of
the building remained unchanged.
They started to build this kind of structures about in 1958.  These
structures went through two earthquakes, the first one in 1976 (7.2 on
Richter scale) and the second in 1986 (6.8 on Richter scale).  I do not
recall any damages whatsoever to have been reported to these structures.

My parents used to live for 30 years in such a building, at the fifth floor,
and never had a problem with the walls and the roof.

The problems I see with these panels are:
-a lots of welding on site;
-an extremely careful erection required to align the panels, to avoid
additional finishes on site;
-all joints have to be formed and concrete poured in joints.

The tragedy with this kind of structures, in my opinion, is that you are
building "concrete boxes" which is very hard to get rid of.

Vlad Cernescu
simina(--nospam--at)idirect.com

-----Original Message-----
From: Walter Sheen [mailto:wsp(--nospam--at)terra.com.pe]
Sent: Friday, June 08, 2001 10:23
To: seaint(--nospam--at)seaint.org
Subject: Re: Tilt Up systems

Dear Paul:

We build five stories cast in place concrete apartment buildings. All walls
are 4 inch thick and wire welded mesh reinforcement. We had the oportunity
to make some research for about two years with natural scale specimens that
had great behaviour, and even after we tested one of the specimens and epoxy
injected the cracks, the repaired specimen had the same performance (a
little bit more flexible though) and failed in another place, not where it
was repaired. This is our experience. Now, after constructing several
buildings (yes, we design and build and then sell the apartments), we came
to a point where we can't make the construction procedure cheaper, so we are
now thinking about some system (Maybe tilt up, or sort of) in which we could
avoid the use of forms, so we thought about using the slab as a form and
then lift the panels and conect them. This would be done over each slab as
the construction grows up. Now we are VERY concerned about connections. I
just received an e-mail from a very recognized Structural Engineer here (who
was one of my undergraduate professors), telling me this systems had a bad
behaviour in Russia, Rumania and China, because of connections. We will
certainly perform some laboratory tests, but it's always easier to go beyond
somebody else's work.

Thanks for your help

Walter
----- Original Message -----
From: "Paul Feather" <pfeather(--nospam--at)san.rr.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Thursday, June 07, 2001 8:31 PM
Subject: Re: Tilt Up systems


> I would think that a precast system would become a better approach than
> trying to do multiple elevations of tilt-up.  From my experience, one or
two
> stories is about the most economical and best suited for tilt-up. I have
> seen three stories, but these typically are just tilt-up cladding systems
> with interior gravity columns.  They may have been used as shear walls but
I
> am not sure.
>
> As the stories go up, I think you will have a real problem trying to get
the
> panels thin enough for economical tilt-up and still function as shear
walls
> without shear and boundary section limitations.
>
> Past a certain point I would think a pure pre-cast solution would work
> better and fit the flow of construction better.  The structure could be
> built with cast in place shear walls at the interior and designated
exterior
> sections, independent gravity system, and the precast applied as cladding.
> I would be willing to bet this would be more economical.
>
> Hugh Brooks used to publish a really good reference "The Tilt-up Design
> Manual".  Provides an excellent background on the benefits / economies /
and
> applications of tilt-up construction.  I don't know if he has updated the
> publication in light of the 1997 code changes.
>
> Paul Feather
> San Diego, CA
>
>
> ----- Original Message -----
> From: "Walter Sheen" <wsp(--nospam--at)terra.com.pe>
> To: <seaint(--nospam--at)seaint.org>
> Sent: Thursday, June 07, 2001 5:43 PM
> Subject: Re: Tilt Up systems
>
>
> > Gerard,
> >
> > Isn't it possible to build this kind of structures floor by floor.
You'll
> > always have the roof slab to build the panels in the next floor so the
> > height of the panels is only 8 feet (that's the standard height we use
for
> > apartment buildings) and you have the same problem you have on the
ground
> > but some floors over. We are more concerned about connections between
> panels
> > to effectively transfer shear during a seismic event. Do you or anyone
> > reading this topic know about any internet address or book reference
about
> > connection between wall panels, specially at corners. The roof slab
would
> be
> > a regular concrete slab and then we would repeat the procedure in the
next
> > floor until we reach the fifth level floor goal.
> >
> > Walter
> > ----- Original Message -----
> > From: "Gerard Madden" <GMadden(--nospam--at)mplusl.com>
> > To: <seaint(--nospam--at)seaint.org>
> > Sent: Thursday, June 07, 2001 7:07 PM
> > Subject: Re: Tilt Up systems
> >
> >
> > Walter,
> >
> > no problem on the tilt-up references.
> >
> > I don't think you'll find much to help you in those references if you
are
> > trying to do a 4 story building from panels with WWF as the reinforcing.
> It
> > would be uneconomical to do a 3 story, let alone a 4 story tilt up. At
> > panels that tall, you need to be aware of stresses during lifting and
the
> > actual weight of the panel ( 50 feet tall) may be too great for the
> standard
> > cranes to pick up and swing around. You also need a big slab to lay the
> > forms down on so you can fit them all. Otherwise it's stacked forms and
> > those can easily get messed up by an inexperience contractor.
> >
> > I suggest you avoid tilt up for this type of structure if you are trying
> to
> > maintain the 4" thickness. What you are describing does not fit into the
> > standard definition of a tilt-up bldg in this country. Be careful & good
> > luck.
> >
> > -gerard
> >
> >
> > >>> wsp(--nospam--at)terra.com.pe 06/07/01 04:44PM >>>
> > Gerard,
> >
> > Thanks for your quick reply. We don't use tilt up here in Peru. We are
> > building 5 story welded wire mesh reinforced concrete 4 inch thick wall
> > buildings and the cost of the forms if very important in the total cost
of
> > the building. So we are thinking about tilt up to lower this cost, but
we
> > wondered about connections and thought there might be some system
already
> > developed, that's what I meant by tilt up system providers.
> >
> > I'll get the references you suggest.
> >
> > Thanks a lot
> >
> > Walter
> >
> >
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