EP1033455A1 - Method and device for reinforcing a concrete structure - Google Patents

Abstract

The reinforcement for concrete has a reinforcement panel (16) glued onto the concrete surface. The panel is composed of fibres extending along on a main surface (A) of the concrete. An anchor plate (17) is fixed to the concrete in a position in which the exterior surface is flush with the concrete surface which receives the panel, which is glued to the anchor plate.

Description

The present invention relates to the field of structural reinforcement of construction works.

In this area, it is usual to glue reinforcements by means of appropriate resins on the parts of a structure to be reinforced.

In a commonly applied conventional process, said process Lhermite, the reinforcement consists of a sheet of steel bonded to concrete after preparation of the bonding surface. This classic process followed various developments taking into account in particular the technological development of materials, and more particularly the evolution of substitute materials sheet metal, which frequently poses implementation problems and requires provisions to combat corrosion.

This is how we have seen the appearance in recent years of reinforcement techniques based on composite materials in the form of glued plates (see for example FR-A-2 594 871), then in the form of fibers glued (see US-A-5,308,430) and glued fabrics. These last types of reinforcement have many advantages, including their ease of implementation work and their ability to apply to surfaces of various shapes.

These different types of bonded reinforcements very significantly improve the static and dynamic behavior of the reinforced structure. It is also very rare to observe a rupture of the reinforcement itself. Figure 1 shows a section schematic of a reinforced concrete beam 8 resting on two supports 9 neighbors of its ends, and the lower face of which comprises, between these two supports 9, a bonded reinforcement 10 resistant to traction in the longitudinal direction of the beam. The bonded reinforcement 10 improves the behavior of the beam 8 in response to an effort F tending to cause it to flex between its two supports 9. When the effort F is important enough to cause a break in the structure of the beam, this rupture generally occurs in "covering" concrete, that is to say in the thickness of unreinforced concrete located between the surface provided of the bonded reinforcement 10 and the underlying reinforcing bars 11. Typically, the rupture 12 begins in the vicinity of one of the ends of the bonded reinforcement 10 under the effect of the shearing force E resulting from the reaction R of one of the supports 9 and the tensile force T exerted by the reinforcement 10, then propagates along the reinforcing bars 11. In other words, it is the concrete of the structure which gives way, in a part where it does not work in compression (its mode of stress desired) but in shear.

Consequently, the properties of the reinforcement are not fully exploited glue.

To increase the breaking force of a beam such as that of the Figure 1 reinforced by a metal sheet, it has been proposed to glue other pieces of sheet metal, called locks, on the sides of the beam, which provide shear strength of concrete. This method has the disadvantage of be applicable only in the case of a beam whose sides are accessible. In practice, reinforcements are often glued to slabs or walls, and it is then impossible to place locks.

Patent application FR-A-2 754 556 describes a method of reinforcement of a reinforced concrete structure by means of a composite reinforcement bonded with carbon fibers, in which strands of carbon are engaged, with agglomeration resin, in holes obliquely drilled in the concrete of the structure, in order to make a connection carbon fiber-based mechanics between the bonded reinforcement and the reinforcements of the concrete. This provides resistance to shear stress.

Patent application WO96 / 21785 describes a method for anchoring the ends of a composite reinforcement bonded to a concrete structure, consisting of form an inclined edge housing in the concrete of the structure, along which the end part of the reinforcement is glued. A wedge-shaped insert is then placed above this terminal part to restore the continuity of the area. This insert can be glued, or anchored in concrete by means of bolts or dowels. The anchoring at the end of the reinforcement therefore results from a some penetration of this end towards the inside of the concrete structure.

It is possible to apply a tensile preload on a reinforcement composite during hardening of the bonding resin (see FR-A-2 594 871 or US-A-5 617 685). This improves behavior in charge of the structure. On the other hand, the prestressed reinforcement stresses the concrete of compression overlap, which reduces the incidence of the problem below.

An object of the present invention is to propose another solution limiting the shear stress to which the concrete is subjected covering the reinforced surface of the structure.

The invention thus provides a device for reinforcing a structure in concrete, comprising a reinforcement bonded to the concrete of the structure and means anchoring at least a portion of the reinforcement to the structure. The reinforcement includes reinforcing fibers extending in at least one direction main. The anchoring means comprise at least one plate anchor fixed to the concrete of the structure in a position such as a surface exterior of the anchor plate is flush with a surface of the structure receiving the reinforcement. The anchored portion of the reinforcement is bonded to the outer surface of the anchor plate.

The plate fixed to the concrete takes up the shear force generated by the reinforcement glued in its anchored portion, which will typically be (but not mandatory) near one end of the reinforcement.

The flush with the anchor plate ensures that the composite reinforcement remains in a continuous bonding plane, without geometric accident which create vacuum surges.

The anchor plate is fixed to the concrete by means of connection can be of any known structure. They are typically arranged to extend to areas of concrete provided with reinforcements, in order to achieve continuity in the resumption of efforts between these areas and the surface stressed by the bonded composite reinforcement.

A preferred embodiment of the device comprises means to maintain tension in the reinforcement parallel to the steering main. These means advantageously include a system of locking the anchor plate in a housing formed in a support anchor fixed to concrete.

• former au moins un renfoncement sur une surface de l'ouvrage ;
• coller un renfort, comportant des fibres de renforcement, sur ladite surface de l'ouvrage en orientant certaines au moins des fibres de renforcement suivant une direction principale de ladite surface de l'ouvrage, le renfort étant disposé de manière à avoir au moins une portion collée sur une surface extérieure d'une plaque d'ancrage fixée dans un renfoncement de façon telle que la surface extérieure de la plaque d'ancrage affleure ladite surface de l'ouvrage.

Another aspect of the present invention relates to a method for reinforcing a concrete structure, comprising the following steps:

• forming at least one indentation on a surface of the structure;
• sticking a reinforcement, comprising reinforcing fibers, on said surface of the structure by orienting at least some of the reinforcing fibers in a main direction of said surface of the structure, the reinforcement being arranged so as to have at least one portion bonded to an outer surface of an anchor plate fixed in a recess so that the outer surface of the anchor plate is flush with said surface of the structure.

• la figure 1, précédemment commentée, est une vue schématique d'une poutre en béton armé pourvue d'un renfort collé et se rompant sous l'effet d'un effort de flexion ;
• la figure 2 est une vue de face d'un dispositif de renforcement selon l'invention ;
• la figure 3 est une vue en coupe du dispositif, suivant le plan III-III indiqué sur la figure 2 ;
• la figure 4 est une vue en coupe du même type que la figure 3, montrant une variante du dispositif ;
• la figure 5 est une vue de face d'une autre variante du dispositif, dans laquelle la plaque d'ancrage porte des moyens de mise en tension du renfort ;
• les figures 6 à 8 sont des vues, respectivement en coupe longitudinale, de face et en coupe transversale d'une autre réalisation d'un dispositif de renforcement selon l'invention, les plans de coupe VI-VI et VIII-VIII des figures 6 et 8 étant indiqués sur la figure 7 ;
• les figures 9 et 10 sont des vues de face et en coupe transversale d'une autre forme de réalisation du dispositif, le plan de coupe X-X de la figure 10 étant indiqué sur la figure 9 ;
• les figures 11 et 12 sont des vues en coupe longitudinale et de face d'une variante de réalisation de la plaque d'ancrage, le plan de coupe XI-XI de la figure 11 étant indiqué sur la figure 12 ; et
• les figures 13 et 14 sont des vues en coupe longitudinale et de face d'une autre variante de réalisation du dispositif d'ancrage, le plan de coupe XIII-XIII de la figure 13 étant indiqué sur la figure 14 .

Other features and advantages of the present invention will appear in the description below of nonlimiting exemplary embodiments, with reference to the appended drawing, in which:

• Figure 1, previously commented, is a schematic view of a reinforced concrete beam provided with a bonded reinforcement and breaking under the effect of a bending force;
• Figure 2 is a front view of a reinforcement device according to the invention;
• Figure 3 is a sectional view of the device, along the plane III-III indicated in Figure 2;
• Figure 4 is a sectional view of the same type as Figure 3, showing a variant of the device;
• FIG. 5 is a front view of another variant of the device, in which the anchoring plate carries means for tensioning the reinforcement;
• Figures 6 to 8 are views, respectively in longitudinal section, from the front and in cross section of another embodiment of a reinforcing device according to the invention, the section planes VI-VI and VIII-VIII of Figures 6 and 8 being indicated in FIG. 7;
• Figures 9 and 10 are front views and in cross section of another embodiment of the device, the section plane XX of Figure 10 being indicated in Figure 9;
• Figures 11 and 12 are longitudinal sectional and front views of an alternative embodiment of the anchor plate, the section plane XI-XI of Figure 11 being indicated in Figure 12; and
• FIGS. 13 and 14 are views in longitudinal section and from the front of another alternative embodiment of the anchoring device, the section plane XIII-XIII of FIG. 13 being indicated in FIG. 14.

Figures 2 and 3 illustrate the application of the invention to a structure in reinforced concrete with a surface 15 provided with a bonded reinforcement 16.

The reinforcement 16 is intended to resist traction in a direction main A of surface 15. It preferably consists of a strip of fibers of sized carbon oriented parallel to direction A, or in a carbon fiber fabric whose warp threads are oriented in the direction A, the carbon fibers being impregnated with a hardening resin ambient temperature. The reinforcement 16 can in particular be carried out from the as follows: an epoxy resin, capable of polymerizing at temperature ambient, is coated in the liquid state on the surface 15; the tape or fabric is then applied to the coated surface so that the resin permeates the fibers and ensures bonding. The tape or fabric can be applied with a simple masking, not requiring the application of prolonged pressure.

The resin used is for example the two-component epoxy resin consisting on the one hand by the base resin of the brand "CECA XEP 3935 / A", and on the other hand by the hardener of mark "CECA XEP 2919 / B", these two components being manufactured and marketed by CECA S.A., 12 place de l'Iris, La Défense 2, Cedex 54, 92062 PARIS LA DEFENSE (FRANCE).

This resin has, when applied in the fluid state, a viscosity at room temperature between 1,000 and 10,000 mPa.s.

• une résistance au cisaillement compatible avec celle du matériau constituant l'ouvrage,
• une résistance à la rupture en traction comprise entre 5 et 100 MPa, avec un allongement à la rupture compris entre 0,5 et 10%,
• et une résistance à la rupture en compression comprise entre 5 et 100 MPa, avec un raccourcissement à la rupture compris entre 0,5 et 10%.

This resin, once hardened, presents:

• a shear strength compatible with that of the material constituting the structure,
• a tensile breaking strength of between 5 and 100 MPa, with an elongation at break of between 0.5 and 10%,
• and a compressive breaking strength between 5 and 100 MPa, with a shortening at break between 0.5 and 10%.

The sized carbon fibers constituting the strip or the fabric 16 have a tensile strength greater than 1,500 MPa, and an elastic modulus between 200 and 400 GPa.

The carbon fiber strip or fabric 16 is extended beyond the area of the structure to be reinforced, in order to anchor its ends in the concrete of the structure. To achieve such anchoring of a end, a plate 17 is installed, the outer surface of which is flush with the reinforced concrete surface 15, and on which the end of the reinforcement 16 is glued.

The length L (measured parallel to direction A), of the portion of the reinforcement 16 bonded to the anchor plate 17 is typically at least 10 cm, in order to ensure a good recovery of the shearing force. This plate 17 is advantageously made of steel with a thickness of at least 5 mm in order have adequate shear strength. The dimensions and precise materials of the plate 17, as well as the characteristics of the means used to anchor it in concrete, are parameters whose values are adjusted according to the relevant stresses for each structure to reinforce and characteristics of the composite reinforcement.

To make such anchors of the reinforcement 16, the procedure is as follows.

Before gluing the reinforcement 16, a recess 19 is formed at the level from the end to be anchored of this reinforcement. The bottom of the recess 19 is treated with a leveling mortar to make it smooth. Then we drill into the concrete holes 20 intended to receive the connection members 18 of the plate. These holes 20 extend to the reinforcing bars (not shown) of the concrete of the structure in order to make an appropriate connection between these reinforcements and the reinforcement 16. Plate 17, previously prepared to receive the bonded reinforcement (sandblasting), is installed in the recess and anchored using the connectors 18 engaged in the holes 20. The connectors 18 are typically steel rods engaged in the holes 20 where they are chemically or mechanically sealed. They could also be in one other material with the required capabilities to work in shear and traction. These connectors can be active (pre-stressed) or passive.

Once in place and anchored, the plate 17 has its outer surface which is flush with the surface 15 of the structure on which the reinforcement 16 is bonded. can then stick the reinforcement 16 in the manner previously described such so that its end overlaps the anchor plate 17. According to applications, a protective and / or decorative treatment of the reinforced surface can be applied.

In the variant shown in Figure 4, the reinforcement 16 is held between the anchor plate 17a on which it is glued and a second plate 17b. The second plate 17b may have a configuration similar to that of the plate 17a. It is clamped against the reinforcement 16 and the anchor plate 17a by the stress exerted on the connection members 18, for example by means nuts.

In the variant shown in Figure 5, supports 24 are welded to the outer surface of the anchor plate 27 to carry the axle of a roller 25 perpendicular to the direction A. The roller 25, which can be removable or not, used to tension the strip of reinforcing fabric 16 at the time of its collage. For example, the fabric strip can be rolled up on the roller 25 and tensioning by actuation thereof. We can also exert traction on the strip 16 beyond the rollers 25 which then serve as a guide to guide the strip along the surface of the work to reinforce and orient the traction parallel to this surface.

The invention has been described with reference to Figures 2 to 5 in the case of anchoring the end of a bonded reinforcement. Similarly, any portion of the reinforcement could be anchored by covering an anchor plate suitably fixed to the structure using connectors. In a way general, the reinforcement method according to the invention has the advantage of being able be implemented with very diverse surface configurations reinforced.

In the embodiments shown in Figures 6 to 14, the plate anchor to which the end of the composite reinforcement 16 is bonded is not anchored directly in concrete. An anchor support 30, 40, 60 (not shown for the example of Figures 11 and 12) is fixed in each indentation, previously formed in the concrete of the structure, for example by means of connection members 18 similar to those previously described. This anchoring support 30, 40, 60 is provided with a housing 31, 41, 61 open to the outside of the structure and suitable for receiving the anchor plate 32, 42, 62.

In use, a locking system blocks the anchor plate 32, 42, 52, 62 in its housing 31, 41, 61, so as to maintain an effort of prestressing in the main direction A in the composite reinforcement 16.

In the embodiment shown in Figures 6 to 8, the support 30 and the anchor plate 32 are provided with holes 33, 34 opening onto the face exterior of the structure, intended to receive a tensioning system for strip 16. The tensioning system may include one or more telescopic cylinders having one end connected to the orifices 33 and one end opposite connected to the orifice 34. The actuation of these jacks makes it possible to set tensioning the strip 16, the end of which has been previously fixed by gluing to the anchor plate 32, by sliding the plate 32 in the housing 31. A wedge 35 is then engaged in the housing 31 in order to block the plate there. anchor 32 during and after the hardening of the adhesive, the surface of which concrete has been coated.

In the example shown, the lateral edges of the housing 31 include two respective longitudinal grooves 36A, 36B formed in the thickness of the anchoring support 30, one 36A receiving a flange complementary 37A provided on a lateral edge of the anchoring plate 32, and the other 36B receiving a complementary flange 37B provided on the lateral edge opposite of the shim 35. The plate 32 and the shim 35 are in mutual contact according to a surface 38 parallel to direction A, and inclined relative to the surface of the work, so that the shim 35 prevents the plate 32 from coming out of its housing 31. On the other hand, the wedge 35 is supported on the support 30 along a ramp 39 forming an angle with direction A, so that when the system of tensioning is activated, just push the shim 35 into the housing 31 towards the strip of fabric 16 to block the plate 32 in the housing 31, which maintains the prestressing force in the strip 16 during and after the glue has hardened.

Figures 9 and 10 show an alternative embodiment in which the lateral edges of the anchor plate 42 are provided with flanges respective 47 engaged in complementary grooves 46 formed in the lateral edges of the housing 41. The grooves 46 are interrupted in a front part 43 of the housing 41, over a length at least equal to that of the plate 42. In this front part 43, the housing 41 is wider than the anchor plate 42, to allow its introduction. Plate 42 can then slide back when tensioning the composite reinforcement, by being guided and held in place by the grooves 46. This setting tension can be carried out by means of two wedge effect wedges 44, 45 interposed in the front part 43 of the housing 41, bearing one on the other on an oblique surface, the shim 44 being applied against the edge front of the plate 42, and the shim 45 being applied against the front edge of the housing 41. By pushing the shims 44, 45 towards each other, as indicated by the arrows P in FIG. 9, the reinforcement is tensioned composite previously bonded to the anchor plate 42.

In the embodiment shown in Figures 11 and 12, the plate anchor 52 has a slot 53 perpendicular to direction A, and length slightly greater than the width of the strip of fabric 16. The strip 16 is engaged in the slot 53, and wound around the portion 54 of the plate 52 located in front of the slot 53, before being bonded to this portion 54. This increases the robustness of the fixing of the reinforcement 16 on the plate anchor 52. Once this attachment is made, the plate can be installed 52 on an anchor support previously sealed in the concrete surface to be to reinforce. This anchoring support can for example be of the same kind as those described above with reference to FIGS. 6 to 10.

In the embodiment according to Figures 13 and 14, the anchor plate 62 also has a slot 63 perpendicular to the direction A. The references 62A and 62B respectively designate the portions of the plate 62 located in front and behind the slot 63. In this embodiment, the strip of fabric 16 is wound in S around the two portions 62A, 62B of the plate anchor 62, as shown in FIG. 13. The end of the strip 16 is applied to the outer face of the rear portion 62B, and from there, the strip 16 goes around the rear edge of plate 62, runs along the inside of the portion 62B, crosses the slot 63, runs along the outside face of the portion 62A, bypasses the front edge of the plate 62, runs along the inside of the portions 62A and 62B, returns around the rear edge of the plate 62, then runs along again the external face of the portions 62B and 62A before coming into contact of the concrete face to be reinforced.

This S-shaped winding ensures firm fixing of the strip 16 on the anchor plate 62, so that the bonding of the strip 16 on the plate anchoring 62 can be carried out at the same time as the bonding of this strip on the concrete face. On the other hand, the tensioning of the strip of fabric 16 can be carried out by applying the front edge of the plate 62 against the edge front of the housing 61 formed in the anchoring support 60, and by folding the rear edge of plate 62 as shown in phantom in Figure 13. After this tensioning, the plate 62 is immobilized in its housing 61, for example by screwing on the support 60 through holes 64 provided on either side of the strip 16 in the anchor plate 62. As the shows figure 14, in order not to damage the fabric 16, the front edge of the anchor plate 62 bears against the front edge of housing 61 only on either side of the width of the strip 16.

Claims (21)

Reinforcement device for a concrete structure, comprising a reinforcement (16) bonded to the concrete of the structure and anchoring means of at least a portion of the reinforcement on the structure, in which the reinforcement comprises fibers reinforcement extending in at least one main direction (A), characterized in that the anchoring means comprise at least one anchor plate (17; 17a; 27; 32; 42; 52; 62) fixed to the concrete of the structure in a position such as an exterior surface of the anchor plate is flush with a surface (15) of the structure receiving the reinforcement, and in that said portion of the reinforcement is glued to the outer surface of the anchor plate. Device according to claim 1, in which the reinforcement (16) covers the outer surface of the anchor plate (17; 17a; 27; 32; 42; 52; 62) over a length (L) of at least 10 cm measured parallel to the main direction (A). Device according to claim 1 or 2, in which the plate anchor (17; 17a; 27; 32; 42; 52; 62) has resistance to shear greater than 1.5 MPa. Device according to claim 3, in which the anchor plate (17; 17a; 27; 32; 42; 52; 62) is made of steel and of thickness at least equal to 5 mm. Device according to any one of claims 1 to 4, in which the outer surface of the anchor plate (27) has means (24) for supporting a system (25) for tensioning the reinforcement (16) according to the main direction (A). Device according to any one of claims 1 to 5, in which reinforcement is held between the anchor plate (17a) and a second plate (17b), said plates being fixed to concrete by means of common connection (18). Device according to any one of the preceding claims, comprising means for maintaining tension in the reinforcement parallel to the main direction (A). Device according to claim 7, in which the means for maintain tension in the reinforcement parallel to the main direction (A) include an anchor plate locking system (32; 42; 52; 62) in a housing (31; 41; 51; 61) formed in a fixed anchoring support to concrete. Device according to claim 8, in which the system of locking device comprises at least one wedge effect member (35; 44, 45) arranged between the anchor support and the anchor plate to resist tension exerted in the reinforcement (16). Device according to claim 8 or 9, in which the plate anchor (52, 62) has a slot (53, 63) substantially perpendicular to the main direction (A), and in which the reinforcement (16) is in the form of a strip having an end portion wrapped around the anchor plate in crossing said slot. Method for reinforcing a concrete structure, comprising the following steps: forming at least one recess (19) on a surface (15) of the structure; sticking a reinforcement (16), comprising reinforcing fibers, on said surface of the structure (15) by orienting at least some of the reinforcing fibers in a main direction (A) of said surface of the structure, the reinforcement being arranged to have at least a portion glued to an outer surface of an anchor plate (17; 17a; 27; 32; 42; 52; 62) fixed in a recess so that the outer surface of the plate anchor is flush with said surface of the structure. The method of claim 11, wherein a plate anchor (17; 17a; 27) is fixed in each recess by means connection members (18) before gluing the reinforcement. Method according to claim 12, in which the reinforcement is placed between the anchor plate (17a) and a second plate (17b) fixed by means connecting members (18). The method of claim 13, wherein a stress on the connection members (18) in order to tighten the second plate (17b) against the reinforcement (16) and the anchor plate (17a). Process according to any one of Claims 11 to 14, in which has the reinforcement (16) so that it covers the outer surface anchor plate (17; 17a; 27; 32; 42; 52; 62) over a length (L) at least 10 cm measured parallel to the main direction (A). Process according to any one of Claims 11 to 15, in which has the reinforcement (16) so that it stops, parallel to the main direction (A), on the outer surface of the anchor plate (17; 17a; 27; 32; 42; 52; 62). Method according to any one of claims 11 to 16, in which the reinforcement is placed in tension when the reinforcement (16) is bonded to said surface of the structure (15). The method of claim 17, wherein the tensioning is carried out by means of a system (25) installed on the anchor plate. Method according to claim 17 or 18, in which a anchoring support in the recess formed on said surface (15) of the structure, and the anchor plate is blocked in a housing formed in said anchoring support to maintain the tension exerted when gluing the reinforcement on said surface of the structure. Method according to any one of claims 17 to 19, in which is bonded the reinforcement (16) on said surface of the work (15) after having glued said portion to the anchor plate (32; 42; 52), the tension of the reinforcement being applied by traction to the anchor plate. Method according to any one of claims 17 to 19, in which is bonded the reinforcement (16) on said surface of the work (15) at the same time that said portion on the anchor plate (62).

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