Hollow core slab and methods for its production

Abstract

Hollow core slab (1) comprising a top slab (10) and a bottom slab (20) connected to the top slab (10) made of a matrix material, wherein the top slab (10) has reinforced webs (6) made of the matrix material which are embedded in the matrix material of the bottom slab (20) and wherein the reinforced web (6) and the bottom slab (20) form a connecting penetration area (22), characterized in that the top slab (10) additionally has projecting reinforcement elements (4) embedded in a matrix material of the top slab (10) with a first side, wherein the projecting reinforcement elements (4) are embedded in the matrix material of the bottom slab (20) with a second side, wherein the cross-section of at least a part of the reinforced webs (6) widens in the direction of the bottom slab (20).

Description

[0001] The invention relates to a hollow-core slab and a method for manufacturing a hollow-core slab, also known as a double-walled concrete slab. Double-walled concrete components, such as wall elements, but also hollow-core slabs, are known from the prior art. In the case of wall elements, the cavity is filled with concrete on-site to reduce transport costs. However, slab elements with a favorable ratio between load-bearing capacity on the one hand and weight and material usage on the other are already in use.

[0002] Document CN 102535710 A describes a ceiling beam that is open at the top on one side and intended for concreting. Document DD 151 424 A1 also specifies in-situ concreting, using a lightweight panel as the beam.

[0003] In contrast, ceiling elements are also known that do not require concrete and in which a cavity remains inside. Fiber-reinforced concrete elements, in particular slabs and webs, which are joined together, especially bonded, to form a ceiling, are known from publication WO 2021 / 043428 A1. In publication WO 2024 / 002854 A1, textile-reinforced concrete strips connect an upper and a lower slab of the ceiling. In publication DE 10 2013 106 174 A1, however, the cavity is formed by a cellulose honeycomb core.

[0004] US Patent 3,475,529 A describes a ceiling element, a hollow-core slab, assembled from two parts, one of which is prestressed. First, a concrete slab with continuous ribs is produced and placed, with these ribs, into a freshly poured, flat concrete slab traversed by prestressing tendons. To achieve a connection between the first ribbed concrete slab and the flat, prestressed concrete slab, wires are inserted in the ribbed area in some embodiments (see [reference]). Fig. 8) or by different types of concrete (see below). Fig. 9) an improved connection to the second element is achieved. However, due to the demoldability, the rib has its narrowest width where it is connected to the second part, and this connection point is particularly critical and must absorb shear forces under load.

[0005] German patent application DE 34 17 020 A1 relates to a method and a device for producing prefabricated hollow-core slabs made of reinforced concrete, particularly for ceiling and floor applications in building construction and civil engineering. The invention provides for the separate production of two shells, one of which incorporates ribs with protruding reinforcing bars. These reinforcing bars are then embedded in the fresh concrete of the second shell. This results in load-bearing rib connections with minimal concrete usage. The method enables simplified demolding and more efficient industrial production, e.g., on assembly line production lines. Furthermore, the use of sand fill eliminates the need for complex formwork. The resulting hollow-core slabs are highly load-bearing and also suitable for climate control, for example, by introducing heated air into the cavities.

[0006] German patent application DE 10 2004 039 576 A1 relates to a connecting element for joining spaced-apart wall or ceiling panels, characterized by a metal core and a concrete encasing it. The object of the invention is a permanently load-bearing, corrosion-protected, and material-saving connection solution. The concrete encasing increases the compressive strength and buckling stiffness of the element and can additionally have profiled end sections for improved anchorage in the concrete of the shell. In preferred embodiments, the connecting element is designed as a lattice girder with a diagonally arranged core, wherein the encasing is connected between the diagonals to concrete bridges, the end sections of which are embedded in the concrete of the wall or ceiling panels. A wedge-shaped insulation serves as permanent formwork for the encasing and simultaneously creates flat surfaces for additional insulation panels.Overall, the invention enables an improved static and structural connection of double-shell building elements with reduced effort.

[0007] German patent application DE 30 42 078 A1 discloses a hollow core slab comprising a top slab and a bottom slab connected to the top slab. Reinforced webs are embedded in a matrix material of the top slab. The reinforced webs have two sides, a first and a second side, which are arranged opposite each other along the longitudinal axes and parallel to the longitudinal extent. The reinforced webs are embedded in the top slab with one side and in the matrix material of the bottom slab with the other. The web and bottom slab form a connecting penetration zone. Cement or a similar material is used as the matrix material.

[0008] German patent application DE 43 15 254 A1 describes a method for producing concrete slab elements with integrated ribs and the resulting concrete slab element, which is used for grouting with cast-in-place concrete. The unique feature lies in the use of permanent formwork, in which lattice girders serve simultaneously as reinforcement and as supports for the formwork walls. These walls preferably consist of perforated material such as expanded metal, allowing the cast-in-place concrete to mechanically interlock with the rib during subsequent grouting. A portion of the reinforcement is intentionally left exposed to enable a strong bond with the cast-in-place concrete. This design increases the load-bearing capacity of the precast element and simplifies its production.

[0009] The object of the invention is to offer a hollow ceiling slab in which the connection between the two parts is particularly stable and designed to transmit forces in a defined manner, but which does not require concreting on the construction site.

[0010] The problem is solved by a hollow core slab according to the prior art, comprising a top slab and a bottom slab connected to the top slab. According to the invention, the top slab, in addition to projecting webs, has projecting reinforcement elements embedded in a matrix material of the top slab. The projecting reinforcement elements also have two sides, a first and a second side, which are arranged opposite each other along the longitudinal axes and parallel to the longitudinal extent. The projecting reinforcement elements and the reinforced webs are embedded in the top slab with one side. The projecting reinforcement elements and the reinforced webs are embedded in the matrix material of the bottom slab with the other side. According to the invention, the cross-section of at least part of the webs widens towards the bottom slab, thus enabling improved anchorage with the bottom slab and force transmission into the bottom slab.The web and base plate form a connecting penetration zone, as in the prior art. Preferably, concrete is used as the matrix material and the hollow core slab is designed as a double concrete slab.

[0011] Preferably, the projecting reinforcement elements comprise lattice girders that connect the top and bottom slabs and, in particular, absorb tensile loads. Additional reinforcement elements, such as longitudinal chords, can also be used.

[0012] It has proven advantageous if at least part of the reinforced webs are flanked, at least on their sides, by a lost web form, and wherein the reinforced webs in particular bear compressive loads. Preferably, the lost web form consists of a layer of expanded metal formed into a V-shaped cross-section with a flattened bottom.

[0013] A preferred embodiment of the hollow core slab has a height of 250 mm, wherein the top slab, in the area of ​​the reinforced webs, comprises at least a portion of each web containing three 19 mm lattice girders. Two of these girders flank the reinforced web in a normal position, while the central girder is mounted upside down and embedded in the web. The top slab of this embodiment is 70 mm thick, and the bottom slab is 60 mm thick. The web penetrates 10 mm into the matrix material of the bottom slab, forming a penetration zone there.

[0014] The problem is also solved by a method for manufacturing the aforementioned hollow ceiling panel according to claim 7, which has a top panel and a bottom panel connected to the top panel, characterized by the following steps: 1. Inserting protruding reinforcement elements with one side into a preferably open-topped form for the top plate; 2. Introducing the matrix material of the top plate, in particular concrete, into the mold for the top plate and compacting it, e.g. by vibrating the mold; 3. Placement and compaction of the matrix material, in particular concrete, of the reinforced bridge; 4. Roughening the surface of the reinforced walkway; 5. Curing and demolding of the top plate with molded, reinforced web; 6. Place and compact the matrix material of the base plate into a mold for the base plate; 7. Rotate the top plate so that the protruding reinforcement elements and the reinforced web point downwards towards the shape for the bottom plate; 8. Insert the top slab with a portion of the reinforcement elements and the reinforced web, each with its second side, into the fresh matrix material of the bottom slab; 9. Curing and demolding of the base plate.

[0015] Preferably, lattice girders are used as projecting reinforcement elements. A lattice girder consists of a plurality of parallel bars that are laid diagonally one above the other and connected to each other at the intersections to form a grid. The top and bottom edges of the girder are generally formed by continuous flanges. It is further preferably provided that concrete is used as the matrix material and that the top and bottom slabs are made of concrete. Thus, the hollow core slab according to the invention is designed as a double concrete slab.

[0016] According to an advantageous embodiment of the method, the central lattice girder is held overhead with short 6 mm iron bars under the longitudinal chords.

[0017] The invention is explained in more detail below with reference to the description of exemplary embodiments and their illustration in the accompanying drawings. The drawings show: Fig. 1: schematically a cutaway side view of a top plate of an embodiment of a concrete double ceiling according to the invention; Fig. 2: schematically a cutaway side view of a top plate with a bottom plate of an embodiment of a concrete double slab according to the invention before joining; and Fig. 3: Schematically, a cutaway side view of a double concrete ceiling according to the invention.

[0018] Fig. Figure 1: Schematic of a cutaway side view of a top slab 10 of an embodiment of a double concrete slab 1 according to the invention. The top slab 10 was removed from a mold (not shown) into which the matrix material concrete and, prior to concreting, the projecting reinforcement elements 4, consisting of lattice girders 4 and reinforcing meshes 5, had been placed. In addition, the lost web forms 8, together with a lattice girder 4 mounted in reverse, were placed onto the reinforcing mesh 5 inserted into the mold before concreting. The lost web form 8, with its V-shaped cross-section, consists of a formed expanded metal, which is indicated by dashed lines in the cutaway view. To form the reinforced web 6, the lost web form 8 was also filled with the matrix material concrete, wet-on-wet, almost to the upper edge after the top slab 10 had been concreted.The surface is roughened to facilitate the subsequent bonding with the matrix material of the base plate 20 (see . Fig. 2 and Fig. 3) to improve.

[0019] Fig. Figure 2 schematically shows a cutaway side view of a top slab 10 with a bottom slab 20 of an embodiment of a double concrete slab 1 according to the invention before assembly. For this purpose, the top slab 10 was turned over so that the reinforced webs 6 and the lattice girders 4 point downwards towards the freshly poured bottom slab 20. Subsequently, the top slab 10 is lowered until the lattice girders 4 and the reinforced webs 6 penetrate the fresh concrete of the bottom slab 20 and bond with it as it hardens.

[0020] Fig.Figure 3 schematically shows a cut side view of a concrete double slab 1 according to the invention, after the upper slab with the webs 6 and the lattice girders 4 has been lowered into the fresh concrete of the lower slab 20 to such an extent that a penetration area 22 is created for the reinforced webs 6.

[0021] In the illustrated embodiment of the inventive double concrete slab 1, the overall height is 25 cm, with the upper slab being 70 mm thick and the lower slab 60 mm thick. The space between is bridged by the lattice girders 4 and the reinforced webs 6 and does not need to be filled with concrete, resulting in savings of material and weight. Reference symbol list 1 hollow ceiling slab, concrete double ceiling 4 projecting reinforcement elements, lattice girders 5 additional reinforcement elements, reinforcement mat 6 reinforced footbridge 8 lost bridge shape 10 Top plate 20 Base plate 22 Penetration area

Images