CONCRETE CEILING ELEMENT WITH CONCRETE WEDGE

Description

[0001] The invention relates to a ceiling element according to the preamble of claim 1.

[0002] From DE 20 2022 105 282 U1 a generic ceiling element is known which is designed as a hybrid prefabricated element and has a wooden element between the two concrete shells, which can be designed as a web or beam with a correspondingly small cross-section, or as a slab with a correspondingly larger cross-section.

[0003] US 2022 / 372759 A1 describes a T- or I-beam, which can also be designed as a U- or box-section profile. Three plates made of a reinforced stone material, for example with a concrete material, are aligned and connected to each other in a known manner, such that, for example, a central, upright plate connects an upper plate to a lower plate. Carbon fibers embedded in a stone or concrete matrix are proposed as reinforcement. A force-transmitting connection between the upright plate and the other plates is achieved by interlocking the plates, with the upright plate having prongs that engage in recesses in the other plates. The reinforcements of the orthogonally intersecting plate planes should geometrically overlap or at least meet in a cross-sectional plane.

[0004] AT 396 274 B describes a cast concrete ceiling slab with a reinforcement body that includes displacement elements, the spacing of which creates a space for the formation of stiffening ribs. The stiffening ribs are also made of cast concrete and connect an upper and a lower element slab, with the reinforcement body from the lower element slab engaging with the upper element slab, among other things, via the stiffening ribs.

[0005] DE 35 07 197 A1 describes a composite element for steel-concrete composite structures, whereby a grid profile strip is welded onto a flange plate of a steel beam. The grid of the profile strip consists of narrow webs and large-area openings arranged between them. Anchor bolts fixed to support plates are inserted through the openings, with the webs of the grid profile strip overlapping the support plate and, together with the anchor bolts, embedded in cast concrete. Using the proposed grid profile strip, a composite structure is to be created which, under load, develops a rigid force-displacement characteristic and, in the limit load range, a plastic one.

[0006] The invention is based on the objective of further developing a generic ceiling element in such a way that it can be particularly well recycled after its service life. Furthermore, it aims to enable high force transmission between elements in a simple manner while using as few resources as possible.

[0007] This problem is solved by a ceiling element according to claim 1. Advantageous embodiments are described in the dependent claims.

[0008] In other words, the invention proposes manufacturing the web, which is statically activated to absorb shear forces and connects to the two concrete shells, thus giving the ceiling element high flexural stiffness, as a reinforced concrete component, just like the two concrete shells. In this way, both the shells and the one or more webs arranged in a ceiling element are always made of the same base material, namely concrete, thus facilitating subsequent processing of the ceiling element by minimizing the number of different materials it contains. The web can consist of fiber-reinforced concrete, with fibers of various materials being suitable, such as plastic, carbon, or steel fibers, and which can be in the form of random fibers or fiber mats. However, the web can also contain rod-shaped reinforcing elements, either exclusively or in addition to the fibers, such as...the reinforcing steel bars, which are known in themselves.

[0009] In one embodiment, the shells, the bridge and the cleats are all made of reinforced concrete, so that the materials used for the various components are as identical as possible.

[0010] The design of the walkway as a reinforced concrete component is surprising insofar as long concrete components with a comparatively small cross-section are prone to breakage. The walkways are narrow and can have a length of, for example, 10 or 12 meters. The invention, however, is based on the premise that the handling of the walkways takes place exclusively at the manufacturing plant of the ceiling elements and thus under controlled conditions, whereas during transport and handling on a construction site, the walkways do not need to be handled individually, but rather form components of the entire ceiling element and are accordingly protected.In addition, the susceptibility of the web to breakage can be significantly reduced by the use of reinforcing material, and since the two shells are already designed as reinforced concrete components, typically as reinforced concrete components, it does not adversely affect the reprocessing of the ceiling element if the webs also consist of reinforced concrete, for example, as reinforced concrete components containing steel reinforcement material.

[0011] The cleats serve to transfer shear forces between a shell and the adjacent web in the ceiling element, which is subject to deflection. Suitable cleats are therefore elements that can transfer the longitudinal shear forces acting between the web and an adjacent shell to that adjacent shell, or from the shell to the web. Furthermore, the cleats advantageously transfer tensile forces from a first shell, via the web, to a second shell.

[0012] In one embodiment, the cleats are made of concrete, i.e., a similar or even the same material as the reinforced concrete elements. In another embodiment, the cleats are made of a material other than concrete, for example, steel, so that the cleats are made of a similar or even the same material as the reinforcement, if the reinforced concrete components are designed as reinforced concrete components.

[0013] The design of the cleats from concrete, with or without reinforcement, is considered particularly advantageous because it allows for a particularly good connection and force transmission with adjacent concrete components, and is also advantageous from a production standpoint and therefore particularly economical. Therefore, unless explicitly stated otherwise, the following descriptions assume that the cleats are made of concrete as the typical design of the web.

[0014] If the cleats are designed as concrete components, excellent force transmission between the web and the shells is ensured, going beyond purely mechanical interaction. Since in this case not only the cleats but also the web are made of concrete, the cleats can be designed as integral parts of the web, which simplifies the production of the ceiling element. The design of the reinforcement during the web's production can determine whether the cleats are reinforced or not. A further simplification can be achieved by manufacturing the web in a standardized, consistently uniform length, thus enabling advantageous and therefore economical mass production.Since the exact dimensions of the ceiling element and thus also the length of the web are individually determined by the respective dimensions of the building to be erected, the webs must be cut to the individually required length anyway.

[0015] If the cleats are not made of concrete, they can also be designed as integral components of the web, for example, in the form of so-called headed studs, bars, (bar) loops, or the like, which project upwards and / or downwards from the web into the adjacent shell. For example, the headed studs, bars, or (bar) loops can be made of steel and be part of the web's reinforcement, although they protrude from the web in sections. Such cleats can be inclined, curved, or angled, e.g., U- or L-shaped, in order to transfer not only the aforementioned shear forces but also load-bearing or tensile forces between the web and the adjacent shell.

[0016] The lugs connecting the web to the shells are, in an alternative design, not integral but rather separate components of the web. This allows for the position and number of lugs to be individually determined according to the specific structural conditions, thus fulfilling the structural requirements as economically as possible. In this case as well, the lugs can be made of concrete, steel, iron, or similar materials. Regardless of their material, the initially separate lugs can be bonded, screwed, bolted, or otherwise fastened to the web, thereby permanently fixing it in place to ensure the desired force transmission.

[0017] If the separate cleats are not made of concrete, they can, for example, be designed as so-called countersunk screws, which are commercially available and therefore economical. In this case, the web can be manufactured in a closed mold without any elements protruding beyond the mold. Instead, threaded sleeves can be cast into the web, so that after completion of the web, the aforementioned countersunk screws can be screwed into the threaded sleeves to form cleats that can absorb shear forces in the longitudinal direction of the web as well as vertical load-bearing forces and transfer them to the adjacent structural component.

[0018] According to the invention, a number of lugs are designed as headed bolts, each with at least one head section and one rod section, wherein a headed bolt is radially expanded in the head section.

[0019] Advantageously, the radial extension in the head section can create a collar which engages a reinforcement arranged in a shell, allowing tensile forces from the shell to be transferred into the web. According to the invention, the rod can be round or polygonal. Furthermore, the radial extension can be circumferential, resulting in an approximately T-shaped cross-section, or it can be implemented as a partial radial extension.

[0020] In the present case, the term "number" can encompass one, several, or all of the elements or objects mentioned.

[0021] The use of headed studs is advantageous because they are relatively easy to produce in large quantities. Such headed studs are typically created by forming, for example, by heating and upsetting an end section of a reinforcing bar, creating a radial expansion in the head section. Forming a reinforcing steel bar can be particularly advantageous for creating a headed stud. Headed studs as described in this proposal preferably have a diameter of at least 6 mm in the bar section.

[0022] In an advantageous embodiment, at least the head section projects higher than the bridge.

[0023] The vertical projection of the head section defines the engagement depth of the headed bolt into a shell. Initial tests have shown that the engagement depth is advantageously 40–80% of the shell thickness, preferably 50–60%, and particularly preferably 60%. Considering these engagement depths allows for particularly efficient load transfer.

[0024] Preferably, a headed bolt can have a head section at each end, thus two head sections, which preferably each extend higher than the web, so that a first head section of the headed bolt engages in a first shell and a second head section of the same headed bolt engages in a second shell.

[0025] In a further development, a number of brackets can be designed in a rod shape with a curved course, at least in sections.

[0026] Advantageously, a metallic rod, such as reinforcing steel or the like, can be formed into a cleat as described in this proposal after being shaped to create a curved profile. Such cleats are particularly easy to manufacture and can be easily adapted to the expected load conditions, for example, by defining a specific bending radius and / or a required rod diameter.

[0027] Preferably, the curved profile is essentially U-shaped, so that the bending radius is essentially 180°.

[0028] In one embodiment, the curved section and the bridge include an access opening which opens in the longitudinal direction of the bridge.

[0029] The aforementioned access opening can advantageously serve, in particular, to insert rod-like reinforcement elements or similar components to create a statically activated, i.e., force-transmitting, connection between a shell and the web. For example, it can be provided that, for improved connection of a reinforcement element to the cleat, the cleat and reinforcement element are first joined using wire or by means of a spot weld before the shell is cast, into which the cleat and reinforcement element are at least partially embedded.

[0030] For a particularly advantageous further development, it can be provided that the curved path forms a loop, such that sections of a cleat overlap and / or cross each other.

[0031] In the case of an overlapping design, the cleat can, for example, be designed in the form of two essentially U-shaped sections, with the free ends of the respective U-shaped sections facing each other and partially overlapping.

[0032] In an alternative embodiment, it may be provided that the cleat has only an essentially U-shaped section and that one or both free ends are themselves reshaped, for example parallel to the plane of the U-shaped section and / or essentially orthogonal to it.

[0033] In the case of an intersecting design, the cleat can form a loop with an engagement opening, whereby this engagement opening is advantageously embedded at least partially in the web, i.e., cast into concrete, so that the area of ​​the engagement opening is reduced by the web.

[0034] A cleat with a curved profile, in particular in the manner of the loops presented and / or in the manner of the other embodiments presented with a curved profile, represents a particularly advantageous embodiment which is based on a particularly inventive activity irrespective of the features otherwise described herein.

[0035] In accordance with the present proposal, it is preferably possible to provide for different designs of a cleat for the same ceiling element. This allows for consideration of situation-specific load cases and the achievement of optimal load transfer within a given structure. Preferably, different cleats can be arranged (ir)regularly within a web, whereby, in addition to the design of the cleat, its orientation can also be varied, either alternatively or additionally.

[0036] Furthermore, it may be provided that the web of a proposed ceiling element is not a single, continuous piece, but instead a split web. A split web is particularly advantageous from a production engineering perspective, as fixed lengths for webs can be prefabricated and any shorter webs can be replaced or supplemented with separate web sections. Split webs, or any shorter webs, can also be used to provide space within a ceiling element for a pipe and / or cable conduit, or similar components.

[0037] In one embodiment, a cleat has a number of projections that are oriented essentially parallel to a shell. Alternatively or additionally, it can also be provided that the projections are oriented essentially in the direction of a shell. An arrangement of projections serves, among other things, to counteract tensile and / or shear forces acting, in particular, on the shell and webs. Preferably, the projections can be configured as a (partial) thread, which extends, for example, along the rod section of a headed stud or along a rod-shaped cleat with a curved section. Alternatively or additionally, particle-like projections can be provided, which increase the surface roughness and thus help to counteract relative movement between the shell and the web.

[0038] The aforementioned projections or surface roughening may be intended for a cleat and / or for the web.

[0039] In one embodiment, the cleats project laterally beyond the web, enabling them to transmit load-bearing forces directed perpendicular to the surface of the ceiling element or shell, particularly tensile forces. For this purpose, the cleats can, for example, have an approximately T-shaped cross-section, ensuring a positive fit within the shell in terms of load-bearing capacity.

[0040] In one embodiment, the lugs project higher than the web, so that they form shear lugs which can transmit shear forces acting in the longitudinal direction of the web between the adjacent shell and the web.

[0041] In one embodiment, the cleats have transverse bores, meaning bores that run perpendicular to the longitudinal direction of the web. Supporting struts, which can be made of steel, for example, the same material as the reinforcing steel used, extend through these transverse bores. The supporting struts project laterally beyond the web and the cleats and each run within a shell. Therefore, similar to the cleats mentioned above that project laterally beyond the web, they can transmit tensile forces between this shell and the web.

[0042] In a design deemed advantageous, the support struts extend beyond the web and the lugs on both sides to achieve a symmetrical load distribution. This extension on both sides allows for a large overall load-bearing length of the support struts while simultaneously minimizing the lever arms relative to the lug.

[0043] In one embodiment, the cleats at the top and bottom of the web, namely towards the upper and lower adjacent shells of the ceiling element, are arranged offset from each other in order to achieve the most even distribution possible of the forces acting on the web via the cleats.

[0044] The ceiling element according to the invention can be manufactured by first producing the web from reinforced concrete. If the cleats are provided as separate components, they are connected to the web. A shell of reinforced concrete, for example, the so-called upper shell, is cast lying flat, with its future upper surface facing downwards. The web is pressed into the still-soft, malleable concrete. The cleats and, if applicable, the supporting struts are encased by the concrete of the shell, creating a positive connection between the web and the shell. A second shell of reinforced concrete, the lower shell, is also cast lying flat after the first, upper shell has set.This first, upper shell, together with the bridge, is lifted as a single, manageable assembly, turned 180° so that the bridge is located below the upper shell, and then this assembly is pressed into the still uncured, deformable concrete of the lower shell, so that the connection between the shell and the bridge also takes place when the concrete of the lower shell cures.

[0045] The ceiling element is structurally designed so that, in use, it has a specific orientation and thus a defined top and bottom, and consequently an upper and a lower shell. In one embodiment, the ceiling element incorporates a tensioning element in its lower half, either in its lower shell, in the lower region of the web, or in the transition area between the web and the lower shell. The tensioning element is designed to generate compressive stress within the ceiling element. This counteracts downward deflection of the ceiling element.

[0046] The aforementioned tensioning element is prestressed, or rather stretched, within a specific configuration of the slab element. The tensioning element can be designed, for example, as a rod, a strand, or similar. In this prestressed state, it is encased in the concrete of the web and / or the lower shell during the manufacturing of the slab element, so that in the finished slab element, the concrete is in direct contact with the tensioning element. When the tensioning element is released after the concrete has set, it tends to contract. Due to the friction between the tensioning element and the concrete, the tensioning forces are transferred to the concrete via this friction, resulting in compressive forces acting within the concrete in the lower half of the slab element.

[0047] In an alternative embodiment, the tensioning element has no direct contact with the concrete, but is instead arranged within a sheathing tube. Tensioning devices are attached to the tensioning element, bearing against the web and / or the lower shell. The tensioning element can be designed as a rod, particularly a threaded rod, or as a strand, with the tensioning element having a threaded rod section in the area where the tensioning devices are located. The tensioning devices can have contact plates that bear against the concrete, as well as a clamping nut that runs on the threaded rod on the side of the respective contact plate facing away from the concrete. The length of the sheathing tube is dimensioned so short that it does not make contact with the two contact plates.After the concrete has set, the tensioning devices are actuated by screwing the nuts onto the threaded rods against the support plates, so that compressive forces are introduced into the concrete in the lower half of the ceiling element via the support plates.

[0048] Depending on the dimensions of the ceiling element, several webs are typically used to connect the upper and lower shells.

[0049] Exemplary embodiments of the invention are explained in more detail below with reference to the purely schematic representations. These show Fig. 1 a perspective, partial view of a first embodiment of a ceiling element, Fig. 2 a top view of the web of the ceiling element of Fig. 1 , Fig. 3 a top view of the section of Fig. 1 , Fig. 4 a vertical section through the cutout of the Fig. 3 along line IV-IV, Figs. 5-8: Views of a second embodiment similar to the Fig. 1 bis 4 , Fig. 9 a vertical section of another embodiment of a ceiling element with headed bolts, Fig. 10 a vertical section of another embodiment, and Figs. 11a-c views of different cleats.

[0050] In Fig. 1 A section of a ceiling element 1 is shown. The ceiling element 1 has an upper shell 2 and a lower shell 3, each made of reinforced concrete, and connected to each other by an intermediate web 4 made of reinforced concrete, which in the illustrated embodiment is also made of reinforced concrete. The designations upper shell 2 and lower shell 3 refer not only to the arrangement in the drawings, but also to the position that the ceiling element 1 will occupy in use.

[0051] In Fig. 1 Hidden edges of the individual components are shown in dashed lines. It is therefore evident that the web 4 forms several lugs 5 as integral components on its upper side, towards the upper shell 2, and also forms lugs 5 on its underside, towards the lower shell 3. The lower lugs 5 are arranged offset from the upper lugs 5 in the longitudinal direction of the web 4. Although the lugs 5 can be made of a single material as integral components of the web 4, which is also the case in the illustrated embodiment, a distinction is made linguistically between the web 4 and the lugs 5, since the lugs 5 can also be manufactured as separate components, deviating from the illustrated embodiment, and may, also deviating from the illustrated embodiment, consist of a material other than concrete.

[0052] Fig. 2 shows the pier 4 of Fig. 1 as a single component viewed from above. The lugs 5 are wider than the web 4, so that the upper lugs 5 conceal the web 4. The web 4 is visible between two adjacent upper lugs 5, and below it is the overhang by which the lower lugs 5 project laterally beyond the web 4. In the longitudinal direction of the web 4, the gaps between the respective adjacent lugs 5 on the upper side are the same size as the lugs on the underside, and vice versa, so that in the top view the upper and lower lugs do not overlap, but alternate.

[0053] Fig. 3 shows the section of Fig. 1 of ceiling element 1 in a top view. Hidden edges are shown visibly here, so that web 4 offers the same view as in Fig. 2 and the lower bowl 3 is covered by the upper bowl 2.

[0054] Fig. 4 shows a cross-section of the situation of Fig. 3 along line IV - IV in Fig. 3 The lugs 5 project not only laterally beyond the web 4, but also vertically, so that they can transmit shear forces acting longitudinally along the web 4. This creates an almost crenellated contour of the web 4 on both the upper and lower surfaces. Due to the staggered arrangement of the upper and lower lugs 5, the section cuts through an upper lug 5, while from the adjacent lower lug 5 into Fig. 4 The frontal view can be seen.

[0055] Fig. 5 Figure 1 shows a perspective view of a section of a second embodiment of a ceiling element 1. This embodiment is essentially the same as the embodiment of the Fig. 1 bis 4 The two embodiments are identical, so only the differences will be discussed below. The upper and lower lugs 5, which are molded onto the web 4 in the same material as in the first embodiment, do indeed project upwards and downwards above the web 4, respectively. However, the lugs 5 do not project laterally beyond the width of the web, which is evident from the Fig. 6 und 7 This becomes clear and simplifies the manufacturing of bridge 4.

[0056] Instead, some of the lugs 5 are provided with through holes, which run as transverse holes 6 perpendicular to the longitudinal direction of the web 4.

[0057] The Fig. 7 und 8 This makes it clear that 6 support struts are inserted into the transverse bores. From Fig. 8 It can be seen that the transverse bores 6 are arranged at such a height in the cleats 5 that the supporting struts 7 guided therein lie in the shells 2 and 3 and are completely surrounded by the material of the respective shell 2, 3, so that they can transmit shear and load-bearing forces.

[0058] Fig. 9 Figure 1 shows a vertical section of another embodiment of a ceiling element 1. The key feature is that the cleat 5 is designed as a headed stud 8 with a head section 9 at each end and a connecting rod section 10, wherein the headed stud 8 is radially extended in the head sections 9. The radial extensions form a collar 11 which engages supporting struts 7 in the upper and lower shells 2, 3. Thread-like projections 12 on the rod section 10 counteract tensile forces occurring under load.

[0059] Fig. 10 Figure 1 shows a vertical section of another embodiment of a ceiling element 1 with a cleat 5, which is rod-shaped with at least a partially curved section 13 and, in particular, is essentially U-shaped on both sides. The curved section 13 and the web 4 comprise an engagement opening 14, which opens in the longitudinal direction of the web 4. First support struts 7a extend through the engagement opening 14 and increase the shear and tensile strength of the composite of the ceiling element 1. Second support struts 7b are aligned orthogonally to the first support struts 7a and connected to them.

[0060] The Fig. 11a-c show views of different brackets 5. In Fig. 11a A cleat with a curved profile 13 is shown, with further angled free ends 15. In particular, the bending radius of the curved profile 13, as well as the orientation of the free ends 15, can be designed according to the specific load case in order to achieve optimal load transfer into the ceiling element 1. Fig. 11b und 11c Rod-shaped brackets are depicted with a curved profile 13, at least in sections, wherein the curved profile 13 forms a loop in each case. In Fig. 11b The loop is designed in such a way that sections of the lug 5 overlap each other and, in contrast, in Fig. 11c Sections that intersect each other. Reference symbol:

[0061] 1 Ceiling element 2 Upper shell 3 Lower shell 4 Web 5 Cleat 6 Transverse bore 7 Support strut 7a First support strut 7b Second support strut 8 Head bolt 9 Head section 10 Rod section 11 Collar 12 Projection 13 Curved section 14 Access opening 15 Free end

Claims

1. Ceiling element (1), having two shells (2, 3) and having at least one intermediate element which extends between the shells (2, 3) and is connected to the two shells (2, 3) in an effectively force-transmitting manner by means of cleats (5) in such a way that it forms a statically activated constituent part of the ceiling element (1), wherein the shells (2, 3) are each composed of reinforced concrete, and wherein the intermediate element is in the form of a web (4) made of reinforced concrete, characterized in that a number of cleats (5) are in the form of shear studs (8), each having at least one head portion (9) and a rod portion (10), wherein a shear stud (8) is radially expanded in the head portion (9).

2. Ceiling element according to Claim 1, characterized in that the cleats (5) are formed as integral constituent parts of the web (4).

3. Ceiling element according to Claim 1, characterized in that the cleats (5) are designed as separate components and are in particular adhesively bonded and / or bolted to the web (4).

4. Ceiling element according to any one of the preceding claims, characterized in that at least the head portion (9) protrudes in terms of height above the web (4).

5. Ceiling element according to any one of the preceding claims, characterized in that a number of cleats (5) are rod-shaped with an at least partially curved profile (13).

6. Ceiling element according to Claim 5, characterized in that the curved profile (13) is substantially U-shaped.

7. Ceiling element according to Claim 5 or 6, characterized in that the curved profile (13) and the web (4) enclose an engagement opening (14), which opens in the longitudinal direction of the web (4).

8. Ceiling element according to any one of Claims 5 to 7, characterized in that the curved profile (13) forms a loop in such a way that portions of a cleat (5) overlap and / or cross one another.

9. Ceiling element according to any one of the preceding claims, characterized in that a cleat (5) has a number of protrusions (12) which are oriented extending substantially parallel to a shell (2, 3).

10. Ceiling element according to any one of the preceding claims, characterized in that the cleats (5) are made of reinforced concrete.

11. Ceiling element according to Claim 10, characterized in that the shells (2, 3), the web (4) and the cleats (5) are composed of ferroconcrete.

12. Ceiling element according to any one of the preceding claims, characterized in that the cleats (5) protrude laterally over the web (4).

13. Ceiling element according to any one of the preceding claims, characterized in that the cleats (5) protrude in terms of height above the web (4) in such a way that they form push cams.

14. Ceiling element according to any one of the preceding claims, characterized in that the cleats (5) have transverse bores (6) through which extend support struts (7), which each protrude laterally over the web (4) and over the cleats (5).

15. Ceiling element according to any one of the preceding claims, characterized in that the cleats (5) are arranged offset from one another at the top and bottom of the web (4) with respect to the respectively adjacent shell (2, 3).

16. Ceiling element according to any one of the preceding claims, characterized in that one of the two shells (2, 3) forms the lower shell (3) during use, and the ceiling element (1) has a tensioning element in its lower half, which generates a compressive stress within the ceiling element (1).

17. Ceiling element according to Claim 16, characterized in that the tensioning element is cast in a pretensioned state by the concrete of the web (4) and / or of the lower shell (3) in such a way that, after the tensioning element is relieved of load, the tensioning forces are transmitted to the concrete via the surface friction.

18. Ceiling element according to Claim 16, characterized in that the tensioning element is arranged in a casing tube, and in that tensioning means are arranged on the tensioning element, the tensioning means bearing against the web (4) and / or the lower shell (3) in such a way that, after the concrete has set, actuation of the tensioning means enables compressive forces to be introduced into the lower half of the ceiling element (1).

19. Method for producing a ceiling element according to any one of the preceding claims, the method comprising the following steps: ▪ producing a web from reinforced concrete, ▪ casting a flat first shell from reinforced concrete, with the later upper side of the first shell facing downwards, ▪ pressing the web into the deformable concrete, which has not yet set, of the first shell, the cleats being encased by the concrete of the shell and bringing about a form-fitting connection of the web to the first shell, ▪ casting a flat second shell from reinforced concrete after the first, upper shell has set, ▪ turning the first, upper shell together with the web as a jointly handleable assembly by 180° such that the web is located below the upper shell, ▪ pressing the assembly into the deformable concrete, which has not yet set, of the lower shell in such a way that a connection between the shell and the web takes place as the concrete of the lower shell sets.