CA3016992A1

CA3016992A1 - Method and layout for producing hollow concrete elements

Info

Publication number: CA3016992A1
Application number: CA3016992A
Authority: CA
Inventors: Hans-Jorg Vollert
Original assignee: VOLLERT ANLAGENBAU GmbH
Current assignee: VOLLERT ANLAGENBAU GmbH
Priority date: 2017-11-20
Filing date: 2018-09-10
Publication date: 2019-05-20
Also published as: EP3486053B1; RU2018131101A; DE102017127283A1; RU2018131101A3; EP3486053A1; RU2718743C2

Abstract

The invention relates to a method for producing hollow concrete elements with the following steps, especially in a circulating method: a) preparing of a pallet (15), b) placing of formwork elements (16, 17) on the pallet (15), c) transporting of the pallet (15) to a reinforcing station (5), where tensioning wires (19) are inserted into the space defined by the pallet (15) and the formwork elements (16, 17) and pretensioned, d) transporting of the pallet (15) to a concreting station (7), where at least one layer of concrete is poured into the space defined by the pallet (15) and the formwork elements (16, 17), e) introducing of core elements (21) into the space defined by the pallet (15) and the formwork elements (16, 17), f) pouring of at least one further layer of concrete into the space defined by the pallet (15) and the formwork elements (16, 17), transporting of the pallet (15) to a curing station (11), where the concrete is cured, and h) transporting of the pallet (15) to a destressing station (13), where the tensioning wires (19) are unstressed, especially at the same time. Further, the invention relates to a layout for producing hollow concrete elements.

Description

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,

2 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

3 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

4 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).

5 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.

6 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:

7 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

8 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.

9 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.

10 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.

11 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

Claims

Claims:

1. A method for producing hollow concrete elements with the following steps, especially in a circulating method:
a) preparing of a pallet (15), b) placing of formwork elements (16, 17) on the pallet (15), c) transporting of the pallet (15) to a reinforcing station (5), where tensioning wires (19) are inserted into the space defined by the pallet (15) and the formwork elements (16, 17) and pretensioned, d) transporting of the pallet (15) to a concreting station (7), where at least one layer of concrete is poured into the space defined by the pallet (15) and the formwork elements (16, 17), e) introducing of core elements (21) into the space defined by the pallet (15) and the formwork elements (16, 17), f) pouring of at least one further layer of concrete into the space defined by the pallet (15) and the formwork elements (16, 17), transporting of the pallet (15) to a curing station (11), where the concrete is cured, and h) transporting of the pallet (15) to a destressing station (13), where the tensioning wires (19) are unstressed, especially at the same time.

2. The method as claimed in claim 1, characterized in that in step c) the tensioning wires (19) are led through openings in at least two opposite formwork elements (16) and se-cured in a tensioning and/or holding device (20, 25) on the side of these formwork el-ements (16) facing away from the space defined by the pallet (15) and the formwork elements (16, 17).

3. The method as claimed in claim 1 or 2, characterized in that in step c) the tensioning wires (19) are secured in a clamping yoke (25) which is moved in a first direction pointing away from the hollow concrete element (18) being produced in order to apply the prestressing relative to the pallet (15).

4. The method as claimed in claim 3, characterized in that after applying the prestress-ing to the tensioning wires (19) at least one supporting bracket (28) and/or at least one hy-draulic ram (27) is introduced between the clamping yoke (25) and the pallet (15).

5. The method as claimed in claim 4, characterized in that the at least one supporting bracket (28) and/or the at least one hydraulic ram (27) is introduced by a lifting movement in a second direction at least substantially perpendicular to the plane of the pallet (15) between the clamping yoke (25) and the pallet (15).

6. The method as claimed in one of claims 4 or 5, characterized in that in step h) the at least one supporting bracket (28) between the clamping yoke (25) and the pallet (15) is re-moved and/or the at least one hydraulic ram (27) between the clamping yoke (25) and the pallet (15) is shortened in order to thereby move the clamping yoke (25) relative to the pallet (15) in a third direction opposite the first direction.

7. A layout for producing hollow concrete elements (18) in the circulating pallet method, especially according to the method as claimed in one of the preceding claims, with at least one cleaning station (2), at least one formwork station (4), at least one reinforcing station (5), at least one concreting station (7), at least one curing station or curing chamber (11) and at least one form stripping station (12) as well as a transporting mechanism for conveying of pallets (15) between the individual stations (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14), characterized in that the reinforcing station (5) and/or an additional tensioning station (6) has a mechanism for inserting of tensioning wires (19), the reinforcing station (5) and/or an additional tension-ing station (6) has means (20, 25) for applying a prestressing to the tensioning wires (19), and the form stripping station (12) and/or an additional destressing station (13) has means (27) for unstressing the tensioning wires (19).

8. The layout as claimed in claim 7, characterized in that the means for applying a prestressing to the tensioning wires (15) has at least one hydraulic tensioning cylinder (27) which can be connected to the pallets (15), especially in releasable manner, and which can be connected by clamping sleeves to the tensioning wires (19), and/or the means for applying a prestressing to the tensioning wires (19) has at least one clamping yoke (25) which can be connected to the tensioning wires (19), which is additionally connected to countersupport tensioning wires for applying a prestressing to the tensioning wires (19).

9. The layout as claimed in claim 7 or 8, characterized in that the reinforcing station (5) and/or the additional tensioning station (6) has a mechanism (29) for introducing at least one supporting bracket (28) and/or at least one hydraulic ram (27) between the pallet (15) and an element connected to the tensioning wires (19), especially the clamping yoke (25).

10. The layout as claimed in one of claims 7 to 9, characterized in that the concreting station (7) and/or a further station has means for introducing of core elements (21) into the space defined by the respective pallet (15) and formwork elements (16, 17) arranged on it, and/or the pallet (15) is filled at least in one region with reinforcing concrete (23) and provided with countersupport wires or tensioning strands (24) which can be selectively tightened up and relaxed, in order to at least partly absorb the deformation moments introduced into the pallet (15) by the prestressing forces of the concrete part (18) being produced.