Note: Descriptions are shown in the official language in which they were submitted.
1
Method and layout for producing hollow concrete elements
The invention relates to a method and a layout for producing hollow concrete
elements, espe-
cially for producing finished-element components such as walls or ceilings.
From DE 10 2013 214 058 Al and DE 71 39 155 U concrete ceiling slabs are
known, having
substantially symmetrically shaped, often cylindrical, cavities extending
lengthwise through
the ceiling slab, as well as reinforcing elements which are pretensioned or
slack. Typically,
such hollow-element ceilings are produced by extrusion methods, during which
either extrud-
er worms shape and compact the concrete on a production line, generating the
hollow con-
tours in this way, or a slipformer compacts the concrete on a production line
on top of core
elements, which generate the hollow contours as negative forms. The hollow-
element ceilings
are generated in a continuous process, during which the extruded strand is
usually cut into
segments of defined length with a saw. The drawback to the continuous
extrusion process is
that significant cutting scraps are produced. and crosswise reinforcements,
recesses, installed
pieces or connecting elements in the crosswise direction, as well as
reinforcements sticking
out beyond the concrete can only be produced with great expense, if at all.
Starting from this, one problem which the present invention proposes to solve
is to provide a
method and a layout with which prestressed hollow concrete elements in
particular can be
produced effectively, avoiding the above mentioned drawbacks.
This problem is solved with a method having the features of claim 1. The
invention is based
on the idea that the hollow elements are produced in a circulating process,
especially one
analogous to the solid concrete finished element method. In this case, a
pallet with formwork
elements as it moves through various stations defines a space which
corresponds to the outer
contour of the hollow concrete element being produced, and concrete is then
poured into this
space. Recesses can be easily realized by the introducing of formwork
elements. Tensioning
wires can stick out from the element at the sides. Installed pieces and other
connecting ele-
ments can be concreted in the elements as protruding tensioning wires. This
facilitates the
force locking installation at the construction site, since the wires or
connecting elements can
be used to connect the hollow element to adjoining ceiling elements and walls.
Furthermore,
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reinforcements are possible in the transverse and longitudinal direction. If
is preferable for the
steel pallet to be configured such that lengthwise formwork elements and
transverse formwork
elements at both ends of the pallet can be put in place or firmly secured.
Typically, the form-
work elements are put in place on the pallet such that two or more hollow
elements can be
produced alongside each other on the pallet.
The method according to the invention for the producing of hollow concrete
elements, espe-
cially in a circulating production method, involves for example the following
steps: preparing
of a pallet, placing of formwork elements on the pallet, followed by
transporting of the pallet
to a reinforcing station, where tensioning wires are inserted into the space
defined by the
pallet and the formwork elements and pretensioned, followed by transporting of
the pallet to a
concreting station, where at least one layer of concrete is poured into the
space defined by the
pallet and the formwork elements, introducing of core elements into the space
defined by the
pallet and the formwork elements, during or after the introducing of the
concrete, followed by
transporting of the pallet to a curing station or curing chamber, where the
concrete is cured,
and followed by transporting of the pallet to a destressing station, where the
tensioning wires
are unstressed. It has proven to be advantageous to first pour a first layer
of concrete, e.g., up
to roughly the position of the lower edge of the cavities being produced, then
introduce core
elements to form the hollow spaces in the space defined by the pallet and the
formwork ele-
ments, and then pour at least one additional layer of concrete into the space
defined by the
pallet and the formwork elements.
The tensioning wires may be led through openings in at least two opposite
formwork elements
and secured in a tensioning and/or holding device on the side of these
formwork elements
facing away from the space defined by the pallet and the formwork elements. In
addition or
alternatively, the tensioning wires are secured in a clamping yoke which is
moved in a first
direction pointing away from the hollow concrete element being produced in
order to apply
the prestressing relative to the pallet.
According to one embodiment of the invention, the tensioning wires can be
secured on one
side of the pallet, e.g., to the transverse formwork elements or to end faces
of the pallet. The
tensioning wires may lie at a vertical distance of typically 0 to 50 mm above
the pallet and led
at this vertical distance in clamping blocks, which are secured on the pallet
next to the trans-
verse formwork elements. Outside the clamping blocks, clamping sleeves may
then be placed
on the tensioning wires. For example, hydraulic tensioning cylinders stress
the tensioning
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wires with the aid of the clamping sleeves and generate a prestressing in the
tensioning wires.
The prestressing is thus imposed on the tensioning wires from the outside.
Typically, 10 to 20
tensioning wires are introduced per hollow element, being subjected to a
prestressing force of
up to around 120 kN per tensioning wire. The overall prestressing force per
hollow element
typically has values in the range of 1000 to 2000 kN.
These forces are transmitted to the pallet e.g. via the clamping blocks. For
this reason, it is
preferable for the pallet to be very rigid in configuration. One idea for this
is to reinforce it
with large steel girders or to cast it in concrete.
What is especially novel about the present invention is to both cast the
pallets in reinforcing
concrete and to further stress the pallet during the ongoing production
process with counter-
support wires, as described below. In this way, the bending moments introduced
into the
pallet by the prestressing forces of the concrete element being produced are
absorbed and the
pallet remains flat. Preferably, the countersupport wires or tensioning
strands can be selective-
ly tightened and relaxed, in order to at least partly absorb and/or equalize
the deformation
moments introduced into the pallet by the prestressing forces of the concrete
part being pro-
duced.
Before, during or after the applying of the prestressing to the tensioning
wires, at least one
supporting bracket and/or at least one hydraulic ram can be introduced between
the clamping
yoke and the pallet, in order to maintain the prestressing during the
following production
steps. It has proven to be expedient here for the at least one supporting
bracket and/or the at
least one hydraulic ram to be introduced by a lifting movement in a second
direction at least
.. substantially perpendicular to the plane of the pallet between the clamping
yoke and the
pallet. Advisedly, at least two spacing elements, i.e., supporting brackets
and/or hydraulic
rams, are provided between clamping yoke and pallet in order to absorb the
forces without
creating significant moments in the yoke.
One specific embodiment for the generating of the prestressing consists for
example in fas-
tening a clamping/unclamping yoke on the pallets at the side. Boreholes are
provided in the
yoke, through which the tensioning wires are led. The boreholes are introduced
into the yoke
for example in two or more rows, one above another. The tensioning wires which
run across
the pallet can run through the top row of boreholes. Countersupport tensioning
wires can then
run through the lower row of boreholes and be fastened to the pallet on the
outside. The
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stressing forces which run through the countersupport wires generate an
equilibrium with the
tensioning wires on the pallet during the tensioning process. The
countersupport wires may
alternatively be replaced by another solution which is elastically deformed
during the tension-
ing in the longitudinal direction or which equalizes the deformation path. The
clamp-
ing/unclamping yoke is led for example by guide spikes in the longitudinal
direction.
Basically, there are two possibilities for tensioning the wires:
1) Simultaneous tensioning of all wires by the clamping/unclamping yoke (group
tension-
ing)
The wires being tensioned are fastened to the pallet on one side (passive
side, without clamp-
ing/unclamping yoke).
On the other side (active side), the wires being tensioned are fastened, as
described above, in
the clamping/unclamping yoke, the clamping/unclamping yoke being as close as
possible to
the edge of the pallet with the tensioning cylinders retracted as much as
possible. After fas-
tening all wires being tensioned to the clamping/unclamping yoke, one or more
hydraulic
cylinders presses the clamping yoke in the tensioning direction away from the
pallet and
thereby tensions all the wires at the same time.
After completion of the tensioning process, supporting brackets may be
inserted between the
clamping/unclamping yoke and the edge of the pallet. The function of the
supporting brackets
is to brace the tensioning forces produced by the tensioning device against
the pallet. After
inserting the supporting brackets, the tensioning device may be removed. One
idea is to hy-
draulically move the tensioning or also the destressing cylinders downward and
upward so
that they can be moved into and out from the active zone between pallet and
clamp-
ing/unclamping yoke.
2) Individual tensioning of all wires (individual tensioning)
The wires being tensioned are fastened to the pallet on one side (passive
side, without clamp-
ing/unclamping yoke).
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On the other side (active side), the wires being tensioned are fastened, as
described above, in
the clamping/unclamping yoke, the clamping/unclamping yoke being already
distant from the
pallet at least by the destressing path and the structural width of the
retracted destressing
cylinder, and the clamping/unclamping yoke is secured by support plates
against sliding in the
tensioning direction toward the pallet.
All wires are then individually tensioned, for example, by conventional
prestressing jacks.
The destressing of the tensioning wires can be done, e.g., in that the at
least one hydraulic ram
at first forces the clamping/unclamping yoke so far away from the pallet in
the tensioning
direction that the supporting brackets between the clamping/unclamping yoke
can be relaxed
and removed. After this, the holding pressure of the hydraulic cylinder is
successively re-
duced; the tensioning forces acting on the clamping/unclamping yoke slowly
force the hy-
draulic cylinder in the tensioning direction, Once the hydraulic cylinder has
been push in
enough, no further tensioning forces will be acting on the fastenings of the
tensioning wires
on the clamping/unclamping yoke, so that the fastenings of the wires can be
released, and the
prestressed concrete part can be removed from the pallet.
The above mentioned problem is further solved with a layout for producing
hollow concrete
elements in the circulating pallet method. This layout comprises, e.g., at
least one cleaning
station, at least one formwork station, at least one reinforcing station, at
least one concreting
station, at least one curing station and at least one form stripping station
as well as a transport-
ing mechanism for conveying of pallets between the individual stations.
Further stations may
be integrated in the circulating layout, such as at least one plotter station,
at which markings
are made on the pallet, at least one compacting station for compacting the
concrete, at least
one smoothing station for surface treatment and/or at least one buffer station
for interim
storage of pallets. Preferably, this layout is automated such that the ballets
are transported by
computer control to individual stations and the work steps being done at the
individual sta-
tions occur mechanically and/or computer controlled. According to the
invention, the rein-
forcing station and/or an additional tensioning station may have a mechanism
for inserting of
tensioning wires. Further, the reinforcing station and/or an additional
tensioning station may
have means for applying a prestressing to the tensioning wires. The form
stripping station
and/or an additional destressing station may furthermore have means for
destressing the
tensioning wires.
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The means for applying a prestressing to the tensioning wires has, e.g., at
least one hydraulic
tensioning cylinder which can be connected to the pallets, especially in
releasable manner,
and which can be connected by clamping sleeves to the tensioning wires.
Alternatively or
additionally, the means for applying a prestressing to the tensioning wires
has at least one
clamping yoke which can be connected to the tensioning wires, which is
additionally connect-
ed to countersupport tensioning wires for applying a prestressing to the
tensioning wires.
Moreover, the reinforcing station and/or the additional tensioning station may
have a mecha-
nism for introducing at least one supporting bracket and/or at least one
hydraulic ram between
the pallet and an element connected to the tensioning wires, especially the
clamping yoke.
In order to form cavities in the hollow concrete element, the concreting
station and/or a fur-
ther station of the layout may have means for introducing of core elements
into the space
defined by the respective pallet and formwork elements arranged on it. For
example, round or
rectangular openings may be present in the transverse formwork elements, which
may be
single or two-piece in configuration, through which the (core) tubes or
profiles can be shoved,
creating the cavities in the concrete element. The core elements, i.e., tubes
or other profiles,
may be shoved for example by a tube drawing machine from the right and the
left through the
boreholes of the transverse formwork elements. Another solution is to shove
the profiles
simply by manual effort or other technical assistance through the boreholes of
the transverse
formwork elements, or to insert them from above. The tubes or profiles are
preferably mount-
ed in the boreholes of the transverse formwork elements. Hoses filled with
liquid or gas may
also be used to create the cavities.
The lengthwise formwork elements may have a shear toothing in order to
generate corre-
sponding formations in the concrete elements, by which an especially firm
concrete connec-
tion can be produced by incorporating concrete in situ, especially for
earthquake regions.
The invention shall now be explained more closely with the aid of a sample
embodiment
making reference to the drawing. All features described and/or depicted form
the subject
matter of the invention in themselves, regardless of being brought together in
the claims or
referred back to the claims.
There are shown schematically:
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Fig. 1 a schematic diagram of a layout according to the invention,
Fig. 2 in perspective view, a pallet with hollow concrete elements,
Fig. 3 in cross sectional view a detail of the tensioning station,
Fig. 4 in perspective view, a further detail of the tensioning station, and
Fig. 5 in cross sectional view, a further detail of the tensioning
station.
Figure 1 shows a schematic diagram of a layout for producing hollow concrete
elements in the
circulating pallet method. This layout has, in the series of the production
sequence, a buffer 1,
a cleaning station 2, a plotter station 3, several formwork stations 4,
reinforcing stations 5, a
tensioning station 6, a concreting station 7, a buffer 8, an inspection
station 9, a form stripping
station 10, a curing station 11 with several racks, further form stripping
stations 12, a
destressing station 13 and an unloading station 14. The individual stations
are joined together
by a conveying mechanism such that pallets 15 can be transported to the
stations, especially in
automated fashion. For example, the pallets 15 are transported in a circuit
between the sta-
tions with friction wheel drives.
In departure from the represented embodiment with a separate tensioning
station 6 and a
separate destressing station 13, these stations may also be integrated in
other processing
stations.
The production of hollow concrete elements occurs substantially in the
following sequence:
An empty pallet 15 is delivered from the buffer 1 to the cleaning station 2.
Here, the pallet 15
is cleaned and possibly oiled. After this, the pallet 15 is delivered to the
plotter station 3
where it is optionally plotted, e.g., if insert pieces need to be introduced
manually as a sup-
plement to the formwork.
The pallet 15 then runs through one or more formwork stations 4, where
formwork elements
16, 17 are placed on the pallet 15 and secured there. When applying the
formwork, lengthwise
formwork elements 17 are placed along the pallet (in the x-direction) in order
to bound the
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hollow element 18 being produced at the sides. In the crosswise direction (y-
direction) the
hollow element 18 is bounded by the transverse formwork elements 16.
The pallet 15 so prepared is then taken to one of the reinforcing stations 5,
where reinforce-
ments and/or tensioning wires 19 are introduced. If tensioning wires have been
introduced, the
pallet 15 is delivered to the tensioning station 6. Here, the tensioning wires
19, which typical-
ly run along the pallet through the transverse formwork elements 16 and
through clamping
blocks 20, are pretensioned in the manner described below. After this,
concreting is done in at
least one work station (concreting station 7). The concreting is done, e.g.,
with the aid of a
concrete distributor, which applies concrete in layers. First of all, a thin
layer of concrete is
distributed onto the pallet 15, then core elements 21, such as tubes, which
generate the cavi-
ties, are shoved from the outside through the transverse formwork elements 16,
and after this
a second and possibly other layers are concreted, until the cavity inside the
formwork ele-
ments 16, 17 is completely filled. The filled pallet 15 is then compacted,
e.g., with a separate
shaking station (not shown) or directly in the concreting station 7. The
quality of the concret-
ing and compacting process may be checked in a separate inspection station 9.
Optionally, the surface of the concrete elements 18 is smoothed by a screed
device (not
shown). The pallet 15 is delivered onward and driven by means of a storage and
retrieval
machine to the curing chamber 11. The formwork elements 16, 17 may be removed
before
and/or after the curing chamber. In the curing chamber 11, the concrete
elements 18 harden on
the pallets 15. The pallet 15 is transported by the storage and retrieval
machine from the
curing chamber 11. At a following work station 13, the tensioning wires 19 are
destressed.
Preferably all tensioning wires 19 are destressed at the same time, so that no
cracks are
formed in the concrete element 18.
At the unloading station 14, the concrete elements 18 are unloaded from the
pallets 15 and
taken from there to a storage yard. The pallets 15 arrive either through the
intervening buffer
1 or directly at the cleaning station 2.
Figure 2 shows a pallet 15 on which a concrete element 18 has been provided.
It can be seen
in Figure 2 that cavities running in the longitudinal direction are formed in
the lower/left
concrete element 18 in the figure. These are generated by shoving the core
elements 21, such
as tubes, through corresponding openings 22 in the transverse formwork
elements 16 before,
during or after the concreting process.
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Further, it can be seen that tensioning wires 19 are provided in the
lower/left concrete element
18 in the figure, running in the longitudinal direction, which in the example
shown run be-
neath the cavities. The tensioning wires 19 run through openings in the
transverse formwork
elements 16 and are led outside the transverse formwork elements 16 through
clamping blocks
20. Outside the clamping blocks 20, clamping sleeves are placed on the
tensioning wires 19,
by means of which hydraulic tensioning cylinders (not shown) tension the
tensioning wires 19
and generate a prestressing in the tensioning wires.
The pallet 15 may be appropriately stiffened in order to absorb the
prestressing force of
around 100 kN per tensioning wire 19. In Figure 5, for this purpose, an
example is shown in
which a concrete layer 23 has been introduced beneath the top plate of the
pallet 15, in which
casing tubes 24 run for the retightening. The casing tube 24 make it possible
to introduce by
means of tightening wire strands a stress in the pallet 15 having the effect
of making the
neutral phase run as close as possible in the plane of the top plate. In other
words, the mo-
ments created in the pallet 15 by the prestressing of the tensioning wires 19
should be at least
partly balanced out by specifically applying an opposite moment with the aid
of the tightening
strands.
Figures 3 and 4 show how the stress introduced into the tensioning wires 19
can be main-
tained during the production of the hollow concrete elements 18, i.e.,
especially during the
processing at the concreting station 7, the inspection station 9, the curing
station 11 and the
form stripping stations 10, 12. In Figures 3 and 4, the tensioning wires 19 in
the stressed state
are secured in a yoke 25, which is movably led by guide pins 26 relative to
the pallet 15 and
parallel to the pallet plane. The tensioning wires 19 are led through the
clamping block 20,
which is fixed on the pallet 15, and held in position.
Between the side edge of the pallet 15 and the yoke 25, two hydraulic rams 27
and two sup-
porting brackets 28 are provided in the example shown, wherein the hydraulic
rams 27 make
possible a movement of the yoke 25 relative to the pallet 15 along the guide
pins 26, e.g., for
the defined destressing of the tensioning wires 19 after removal of the
supporting brackets 28,
while the supporting brackets 28 brace the yoke 25 against the pallet 15. In
departure from the
embodiment shown, the yoke 25 may also be braced only by means of the
supporting brackets
28 and be moved in some other defined manner for the destressing of the
tensioning wires 19,
e.g., by countersupport tensioning wires (not shown) acting on the yoke 25
from the outside.
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The hydraulic rams 27 and/or the supporting brackets 28 can be raised up by
means of a lift
drive 29, such as a hydraulic mechanism, into the space between pallet 15 and
yoke 25 or be
lowered from this space. Thus, e.g., a lift drive 29 may be provided in the
tensioning station 6,
in order to arrange the hydraulic rams 27 and/or the supporting brackets 28
between the yoke
25 and the pallet 15 after the stressing of the tensioning wires 19, and a
further lift drive 29
can be provided in the destressing station 13, in order to remove the
hydraulic rams 27 and/or
the supporting brackets 28 after the destressing of the tensioning wires 19
between the yoke
25 and the pallet 15.
Summarizing, the invention by providing a mechanism for the stressing of
tensioning wires
19, especially a separate tensioning station 6, and a mechanism for the
defined unstressing of
the tensioning wires 19, especially a separate destressing station 13, makes
it possible to
produce prestressed hollow concrete elements 18 efficiently and process-safely
in a method or
in a layout by the circulating procedure. Prestressed hollow concrete elements
18 are distin-
guished in that, due to the stressing of the tensioning wires 19, a
compressive stress is exerted,
acting on the concrete, on which is superimposed the gravity force acting on
the hollow con-
crete elements 18 during their use as well as external loads, so that the
tensile stresses acting
on the concrete are minimized or even eliminated. In this way, more sturdy
hollow concrete
elements 18 can be realized for the same size, or more slender hollow concrete
elements 18
for the same loading.
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Reference numbers
1 Buffer 18 Hollow concrete element
2 Cleaning station 19 Tensioning wire
3 Plotter station 20 Clamping block
4 Formwork station 21 Core element
Reinforcing station 22 Opening
6 Tensioning station 23 Concrete layer
7 Concreting station 24 Tightening strand
8 Buffer 25 Yoke
9 Inspection station 26 Guide pin
Form stripping station 27 Hydraulic ram
11 Curing station 28 Supporting bracket
12 Form stripping station 29 Lift drive
13 Destressing station
14 Unloading station
Pallets
16 Transverse formwork element
17 Lengthwise formwork element
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