EP4124703A1 - Reinforced steel-concrete structure - Google Patents

Abstract

A reinforced concrete structure, in particular a reinforced concrete slab or reinforced concrete bending beam, comprises: a reinforced concrete structure; an adhesive; and an elongated fiber composite material which is loosely applied by means of the adhesive on a tension side of the reinforced concrete structure. The elongate fiber composite material has two end areas and a central area, with the reinforced concrete structure having at least one groove under the end areas of the fiber composite material, and the grooves being filled with the adhesive, so that the fiber composite material can be fixed in its end areas via the adhesive in the grooves in the Reinforced concrete structure is anchored.

Description

The invention relates to a reinforced concrete construction, in particular a reinforced concrete slab or reinforced concrete bending beam, and a method for reinforcing reinforced concrete constructions.

For a long time, fiber composite materials have been used for the static reinforcement of reinforced concrete components as flexural or flexural reinforcement. Such fiber composite materials made of carbon, basalt, aramid or glass fibers are produced as prefabricated laminates and glued to the entire surface of the reinforced concrete with a pasty epoxy resin. Alternatively, unidirectional scrims or bidirectional fabrics made from the aforementioned fibers are laminated directly to the building object.

In the prior art, prefabricated slats made of carbon fibers (also known as "CFRP slats") are glued loosely or under pretension. In the case of prestressed CFRP slats, the laminate is mechanically fixed on both sides at the end so that the slat can be prestressed. The force is introduced into the concrete on the one hand via the adhesive surface and on the other hand via a mechanical end anchor, which typically consists of metal elements. Even with slack CFRP reinforcements, the force can be introduced via the adhesive bond and, if necessary, via an additional mechanical end anchor.

WO 2020/157009 A1 shows a well-known deep anchorage for prestressed CFRP slats. Slots are milled across the entire surface of the slats and filled with adhesive. By slitting in depth, the area for the introduction of force is significantly increased due to the vertical of the slits. This almost doubles the force application area. Thanks to this doubling, it is possible to introduce more tensile force from the laminate into the concrete base. This deep anchoring is used when special thick CFRP slats are prestressed. Thick CFRP slats have a significantly higher tensile strength. Accordingly, full-surface adhesion is not sufficient to transfer these high forces to the supporting base.

According to WO 2020/157009 A1 an additional U-profile is used at the end of the slats in the area of the end anchorage. This U-profile also improves the introduction of force. In the case of thick, prestressed CFRP laminations, the tensile force of 3 mm thick CFRP laminations can be introduced into the supporting base. The costs, in particular for a workload, are according to reinforcement WO 2020/157009 A1 however very high.

The object of the invention is therefore to provide an improved system for a reinforced concrete structure and an improved method for reinforcing reinforced concrete structures. In particular, the costs and/or time required are to be reduced.

This object is initially achieved by a reinforced concrete construction, in particular a reinforced concrete slab or reinforced concrete bending beam, comprising: a reinforced concrete construction; an adhesive; and an elongated fiber composite material which is loosely applied by means of the adhesive on a tension side of the reinforced concrete structure. The elongate fiber composite material has two end areas and a central area, with the reinforced concrete structure having at least one groove under the end areas of the fiber composite material, and the grooves being filled with the adhesive, so that the fiber composite material can be fixed in its end areas via the adhesive in the grooves in the Reinforced concrete structure is anchored.

The solution proposed here initially has the advantage that inexpensive local deep anchoring is possible with local milled slots (grooves) under a fiber composite material. Such short, local milling cuts only in the end areas of the fiber composite material can be produced inexpensively, for example by means of hand milling.

Furthermore, the solution proposed here has the advantage that the anchoring of the fiber composite material in the grooves can reliably prevent premature delamination at the ends of the fiber composite material.
Such delaminations mean that only insufficient tensile force is transferred from the fiber composite material to the supporting base and must therefore be avoided as far as possible.

Another advantage of the solution proposed here is that no metal parts are used. In the case of metallic end anchorages (e.g. those discussed above WO 2020/157009 A1 ) there is a risk of corrosion because different metals are used in the screw connection and metal plates (contact corrosion). Chloride ions, which are used as de-icing salt in road construction, also attack the metallic elements of such end anchorages.

A core idea of the present invention is that deep anchoring takes place only locally at both ends of the loosely applied lamella (fiber composite material). It has been shown that the effect of such anchoring is greatest in these areas, and that by omitting such anchoring in a central area of the slats, a comparatively large amount of effort and costs can be saved without losing the essential effect of the anchoring .

In particular, tests have shown that shear cracks are to be expected in these end areas of the fiber composite material, which can lead to early delamination of the fiber composite material. This could be reliably prevented thanks to the inventive anchoring of the adhesive in grooves under the end areas of the fiber composite material.

In the context of this invention, the designation "loosely" or "loosely applied" means "not pretensioned" or "not pretensioned".

In an exemplary embodiment, the reinforcement elements applied to the reinforced concrete structure, in particular the adhesive and the fiber composite material, do not include any metallic components.

In an exemplary embodiment, the same adhesive is used for bonding the fiber composite material to the reinforced concrete structure and for filling the grooves.

In an exemplary embodiment, an epoxy resin adhesive is used as the adhesive.

In an alternative embodiment, two different adhesives are used as the adhesive, with the grooves being filled with a first adhesive and the fiber composite material being applied to the reinforced concrete structure with a second adhesive.

In an exemplary development, the first adhesive has a lower modulus of elasticity (tensile modulus) than the second adhesive.

In an exemplary embodiment, the reinforced concrete structure comprises a plurality of grooves, in particular running parallel to one another, under each end area of the fiber composite material.

In an exemplary embodiment, the grooves run substantially parallel to the elongated fiber composite.

In an alternative embodiment, the grooves run essentially orthogonally to the elongate fiber composite material.

In a further alternative embodiment, the grooves run in a freely selectable direction and/or the grooves do not run parallel to one another.

In a further alternative embodiment, the grooves at least partially intersect.

In an exemplary embodiment, the grooves have a length of 200 to 2000 mm, preferably 200 to 1500 mm, particularly preferably 200 to 1000 mm.

In an exemplary embodiment, the grooves have a depth of 5 to 30 mm, preferably 10 to 25 mm, particularly preferably 12 to 22 mm.

In an exemplary embodiment, the grooves have a width of 5 to 30 mm, preferably 10 to 20 mm.

In an exemplary embodiment, the grooves have a rectangular cross-section.

In an alternative embodiment, the grooves have a triangular, or a semicircular, or an irregularly shaped, or a trapezoidal cross-section.

In a further alternative embodiment, the grooves have a cross section which has an undercut.

In an exemplary embodiment, at least two or at least three or at least four or at least five grooves are arranged under the end regions of the fiber composite material.

In an exemplary embodiment, a maximum of ten or a maximum of eight or a maximum of six grooves are arranged under the end regions of the fiber composite material.

Experiments have shown that, in principle, an anchoring force can be increased by a larger number of grooves under the end regions of the fiber composite material.

By providing suitable grooves, the anchoring force can be roughly tripled compared to gluing the fiber composite material without grooves. Thus, depending on the application, a suitable number, shape and dimensioning of the grooves can be selected.

In an exemplary embodiment, the fiber composite material consists of a prefabricated laminate.

In an alternative embodiment, the fiber composite material consists of a unidirectional or bidirectional fabric that is manufactured on site.

In an exemplary embodiment, the fiber composite material consists of carbon fibers, in particular high-strength carbon fibers, or of basalt fibers, or of aramid fibers, or of glass fibers, or of a combination of these materials.

In an exemplary embodiment, a fibrous material is arranged across the end areas of the fiber composite material, which is anchored in the reinforced concrete structure to the side of the end areas of the fiber composite material.

In an exemplary development, this fibrous material is a unidirectional fiber fabric or fibrous fabric, and/or this fibrous material consists of high-strength carbon fibers.

The object set at the beginning is also achieved by a method for reinforcing reinforced concrete structures, in particular reinforced concrete slabs or reinforced concrete bending beams, the method comprising the steps: milling at least two grooves in a tension side of the reinforced concrete structure, with an intermediate area between the two grooves remaining without milling; applying an adhesive in an elongate pattern, the adhesive covering both the areas of the grooves and the intermediate area, and the grooves being filled with adhesive; applying a flaccid elongate fiber composite to the adhesive such that an end portion of the fiber composite overlies the grooves and a central portion of the fiber composite overlies the intermediate portion between the grooves; so that the fiber composite material is anchored in its end areas via the adhesive in the grooves in the reinforced concrete structure.

The method proposed here in turn offers the same advantages that have already been mentioned for the system proposed here. In particular, as a result, the method can be designed to be more cost-effective, less time-consuming and require fewer tools.

In an exemplary embodiment, a hand mill is used in the milling.

In an exemplary embodiment, the milling operation involves the use of multiple milling blades in a milling machine to form the grooves and gouging away any concrete left between the milling grooves formed thereby.

In an exemplary embodiment, the application of the adhesive forms a continuous adhesive layer which has essentially the same base area as the fiber composite adhesive to be applied thereto.

In an exemplary embodiment, only one adhesive is used when applying the adhesive.

In an alternative embodiment, two different adhesives are used during application, with the grooves being filled with a first adhesive, and with a second adhesive being applied at least to the intermediate area, in particular after the grooves have been filled with the first adhesive.

In an exemplary development, the first adhesive has a lower modulus of elasticity (tensile modulus) than the second adhesive.

Fig. 1

eine schematische Darstellung einer beispielhaften verstärkten Stahlbetonkonstruktion;

Fig. 2a und 2b

schematische Darstellungen von beispielhaften Nuten auf einer Zugseite einer Stahlbetonkonstruktion;

Fig. 3a bis 3c

schematische Darstellungen beispielhafter Querschnitte durch eine verstärkte Stahlbetonkonstruktion; und

Fig. 4

eine schematische Darstellung einer beispielhaften verstärkten Stahlbetonkonstruktion.

Details and advantages of the invention are described below using exemplary embodiments and with reference to schematic drawings. Show it:

1

a schematic representation of an exemplary reinforced concrete structure;

Figures 2a and 2b

schematic representations of exemplary grooves on a tension side of a reinforced concrete structure;

Figures 3a to 3c

schematic representations of exemplary cross-sections through a reinforced concrete structure; and

4

a schematic representation of an exemplary reinforced concrete structure.

In 1 an exemplary reinforced concrete structure 1 is shown, which is reinforced with a fiber composite material 4 . The fiber composite material 4 is applied to a tension side 2 of the reinforced concrete structure 1 . The fiber composite material 4 has two end areas 5 and an intermediate central area 6. Under the end areas 5 of the fiber composite material 4 there are grooves in the reinforced concrete structure 1, which is not visible in this figure.

In the Figures 2a and 2b two exemplary embodiments of grooves 7 are shown schematically. The grooves 7 each have a length 9.
In Figure 2a the grooves 7 are aligned in a direction which runs essentially parallel to the intended longitudinal direction of the fiber composite material.
In Figure 2b the grooves 7 are aligned in a direction which is essentially orthogonal to the intended longitudinal direction of the fiber composite material.
In addition, the intended application locations of the fiber composite material are shown in these figures, with the end regions 5 and the central region 6 of the fiber composite material being identified.

In the Figures 3a to 3c Various cross sections are shown through a reinforced reinforced concrete structure, with one end area of the fiber composite material 4 being shown in each case. It can be seen that an adhesive 3 anchors the fiber composite material 4 in each of its end regions in the grooves 7 .

In Figure 3a three grooves 7 are shown with a rectangular cross section. The grooves 7 have a width 11 and a depth 10. In Figure 3b four grooves 7 are shown with a triangular cross-section. In this exemplary embodiment, the grooves 7 run essentially transversely to a longitudinal direction of the fiber composite material 4. In 3c five grooves 7 are shown, the cross section of which is trapezoidal and has an undercut.

In 4 Finally, another embodiment of a reinforced concrete structure 1 is shown. In this example, a fibrous material 8 is arranged over the end areas of the fiber composite material 4 and is anchored in the reinforced concrete structure 2 to the side of the end area of the fiber composite material 4 . In this example, the fiber material 8 is anchored by gluing it to the side walls of the reinforced concrete structure 1.

Reference List

1

reinforced concrete structure

2

train side

3

adhesive

4

fiber composite material

5

end area

6

center area

7

groove

8th

pulp

9

length of the groove

10

depth of the groove

11

width of the groove

Claims (15)

Reinforced reinforced concrete structure, in particular reinforced concrete slab or reinforced concrete bending beam, comprising: a reinforced concrete structure (1); an adhesive (3); an elongate fiber composite material (4) which is loosely applied to a tension side (2) of the reinforced concrete structure (1) by means of the adhesive (3);
characterized, that the elongate fiber composite material (4) has two end areas (5) and a central area (6), the reinforced concrete structure (1) having at least one groove (7) under each of the end areas (5) of the fiber composite material (4), and the grooves (7) are filled with the adhesive (3), so that the fiber composite material (4) is anchored in its end regions (5) via the adhesive (3) in the grooves (7) in the reinforced concrete structure (1). Reinforced structure according to Claim 1, in which the reinforced concrete structure (1) comprises a plurality of grooves (7), in particular running parallel to one another, under each end region (5) of the fiber composite material (4). A reinforced structure as claimed in any preceding claim, wherein the grooves (7) are substantially parallel to the elongate fiber composite (4), or wherein the grooves (7) are substantially orthogonal to the elongate fiber composite (4). Reinforced construction according to any one of the preceding claims, wherein the grooves (7) have a length (9) of 200 to 2000 mm. A reinforced structure according to any one of the preceding claims, wherein the grooves (7) have a depth (10) of 10 to 30mm. A reinforced structure according to any one of the preceding claims, wherein the grooves (7) have a width (11) of 10 to 30mm. A reinforced structure according to any one of the preceding claims, wherein the fiber composite material (4) consists of a prefabricated laminate, or wherein the fiber composite material (4) consists of a unidirectional or bidirectional fabric fabricated on site. Reinforced construction according to one of the preceding claims, wherein the fiber composite material (4) consists of carbon fibers, in particular high-strength carbon fibers, or of basalt fibers, or of aramid fibers, or of glass fibers, or of a combination of these materials. Reinforced structure according to one of the preceding claims, wherein a fibrous material (8) is arranged across the end regions (5) of the fiber composite material (4) and is anchored in the reinforced concrete structure (1) to the side of the end regions (5) of the fiber composite material (4). Reinforced construction according to claim 9, wherein said fibrous material (8) is a unidirectional fiber scrim or woven fabric, and/or wherein said fibrous material (8) consists of high-strength carbon fibers. Method for reinforcing reinforced concrete structures, in particular reinforced concrete slabs or reinforced concrete bending beams, the method comprising the steps: Milling at least two grooves (7) in a tension side (2) of the reinforced concrete structure (1), an intermediate area between the two grooves (7) remaining without milling; applying an adhesive (3) in an elongate pattern, the adhesive (3) covering both the areas of the grooves (7) and the intermediate area, and the grooves (3) being filled with adhesive (3); and Application of a slack, elongated fiber composite material (4) to the adhesive (3), so that one end area (5) of the fiber composite material (4) is arranged above the grooves (7) and that a central area (6) of the fiber composite material (4) is above the Intermediate area between the grooves (7) is arranged; so that the fiber composite material (4) is anchored in its end areas (5) via the adhesive (3) in the grooves (7) in the reinforced concrete structure (1). Method according to claim 11, wherein a hand mill is used during the milling. A method according to claim 11 or 12, wherein the milling operation uses a plurality of milling blades in a milling machine to form the grooves (7) and concrete which remains between the milling grooves thereby formed is chiselled away. Method according to one of Claims 11 to 13, in which the application of the adhesive (3) forms a continuous adhesive layer which has essentially the same base area as the fiber composite adhesive (4) to be applied thereto. Building having a reinforced structure according to any one of claims 1 to 10, which has been reinforced in particular by a method according to any one of claims 11 to 14.

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