WO2020234341A1 - Method for reinforcing a structure - Google Patents

Method for reinforcing a structure Download PDF

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Publication number
WO2020234341A1
WO2020234341A1 PCT/EP2020/064049 EP2020064049W WO2020234341A1 WO 2020234341 A1 WO2020234341 A1 WO 2020234341A1 EP 2020064049 W EP2020064049 W EP 2020064049W WO 2020234341 A1 WO2020234341 A1 WO 2020234341A1
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WO
WIPO (PCT)
Prior art keywords
frame
reinforcement
initial configuration
groove
anchoring
Prior art date
Application number
PCT/EP2020/064049
Other languages
French (fr)
Inventor
Christian Tourneur
Julien Mercier
Philippe Salmon
Bernard Basile
Original Assignee
Soletanche Freyssinet
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Soletanche Freyssinet filed Critical Soletanche Freyssinet
Publication of WO2020234341A1 publication Critical patent/WO2020234341A1/en

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
    • E04G23/00—Working measures on existing buildings
    • E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
    • E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
    • E04C5/08—Members specially adapted to be used in prestressed constructions
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2201/00—Treatment for obtaining particular effects
    • C21D2201/01—Shape memory effect
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
    • E04G23/00—Working measures on existing buildings
    • E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
    • E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
    • E04G2023/0251—Increasing or restoring the load-bearing capacity of building construction elements by using fiber reinforced plastic elements

Definitions

  • the present invention relates to repair and / or reinforcement of concrete structures in the field of construction. More particularly, the invention relates to methods for repairing and / or reinforcing structures using shape memory reinforcements.
  • One of the known methods is to seal the shape memory framework in a groove that is filled with a sealing mortar after installation of the framework.
  • the assembly consisting of the framework and the sealing mortar is then placed in mechanical tension by raising the temperature of the framework.
  • a drawback of this method is that the mechanical tensioning of the reinforcement embedded in the sealing mortar consumes a lot of energy due to the heat dissipation generated by conduction due to the contact of the reinforcement with the sealing mortar. .
  • the concrete is locally subjected to a high temperature because of the heating of the reinforcement, risking generating local cracks which can be detrimental to the long-term resistance of the reinforcement. structure.
  • a second known method consists in placing shape memory reinforcements of flattened section on the facing of the structure and in maintaining them by fasteners at the ends, such as steel nails driven into the concrete by means of a cartridge gun. explosives.
  • a drawback of this technique lies in particular in its incompatibility with the use of an additional external reinforcement.
  • such a reinforcement is either placed on top of the shape memory frame stretched beforehand and therefore not adherent to the structure, or placed beforehand to be in contact with the structure. In the latter case, the risk is that the reinforcement is damaged by the temperature of the reinforcement during its activation.
  • repair it is rare that the need for reinforcement of the structure is limited to a single direction and one is often confronted with the needs of multiaxial reinforcements, therefore calling on such additional external reinforcements.
  • the invention aims to meet this need and its subject, according to one of its aspects, is a method for reinforcing a structure comprising a cementitious material, this method comprising the steps of:
  • c) raise the temperature, at least of the free portion, to a value, preferably between 160 and 300 ° C, to cause the reinforcement to return to its initial configuration and generate a prestress (a compressive force) in the structure.
  • the invention by reducing the heat transfer between the shape memory reinforcement and the structure due to the fact that the activation takes place before filling the groove, facilitates the rise in temperature of the reinforcement and limits the heat dissipation to the surface. within the structure, thus reducing energy losses and the risk of its weakening by heat during activation.
  • the shape memory frame passes from its initial configuration to its stretched configuration by a traction exerted on the frame at room temperature. Switching to the stretched configuration can be done in the factory, for example, before delivery of the reinforcement to the site.
  • the reinforcement is in the form of a notched bar. The latter may have a cross section of substantially circular or rectangular shape.
  • the frame is in the form of a flat.
  • any shape memory reinforcement capable of being tensioned when activated and generating a prestress (a compressive force) in the structure may be suitable.
  • the material of the shape memory frame is an alloy comprising a base alloy consisting of manganese, silicon, chromium and nickel as well as a complementary proportion by mass of iron.
  • Shape-memory reinforcements which can be used are, for example, those described in European patent application EP 2 141 251 A1 and marketed by the company RE-FER.
  • the method according to the invention includes the step of injecting a filler around the frame in the groove, after the frame has returned to its initial configuration.
  • the filling product can be a resin or any other filling material, for example a cementitious grout.
  • the invention makes it possible to use materials which would be incompatible with the activation temperature of the framework if the activation took place while the kerf is already closed.
  • the filling of the groove makes it possible in particular to ensure a continuity of surface allowing the subsequent installation of one or more additional external reinforcements, these reinforcements being able to adhere perfectly to the structure.
  • the method can thus advantageously comprise the installation, above the groove, of at least one reinforcement transverse to the frame, preferably a reinforcement comprising one or more strips of fabric, in particular a carbon fiber fabric (TFC). or more generally a Fiber Reinforced Polymer (FRP) fabric.
  • a reinforcement comprising one or more strips of fabric, in particular a carbon fiber fabric (TFC). or more generally a Fiber Reinforced Polymer (FRP) fabric.
  • the transverse reinforcement is applied to the filling material, after the latter has hardened.
  • the transverse reinforcement (s) provide additional strength in traction and in shear to the structure.
  • the rise in temperature in the free portion is advantageously obtained by passing an electric current through the latter, but other methods can be used to heat the memory armature from shape, such as exposing the frame to radiation from a UV light source.
  • the electric current flows between points spaced from the zones of the reinforcement anchored in the structure, and this avoids excessively heating the anchored zones.
  • the ends of the reinforcement can be anchored in the structure in many ways, in particular by passive anchoring, for example by sealing at least one end in the structure, for example using a resin of sealing.
  • the method can thus include drilling the structure to form at least one housing for receiving one end of the frame, in which the latter is then sealed.
  • the borehole can be perpendicular to the direction of the frame in which case the frame can be bent, especially at a right angle, to extend out of the housing in the desired direction.
  • at least one end of the frame can be bent, preferably substantially at a right angle.
  • the two ends of the frame are each angled, especially both angled at right angles. Each of these ends can then be received in a respective perpendicular housing.
  • the anchoring of at least one end can be obtained other than in a housing obtained by drilling in said structure.
  • the anchoring of one end of the frame can for example be effected by sealing in a surface housing coming into contact with a surface of the structure.
  • Sealing can be achieved by applying sealing resin around the end of the frame in the housing. This makes it possible to immobilize the reinforcement in the structure, thus making it possible to diffuse the mechanical prestressing forces in the structure.
  • the anchoring of the ends can also be done other than by sealing, for example by anchoring techniques similar to those used for active anchors.
  • the anchoring of one end of the frame can thus be done, for example, using a force distribution element bearing against a surface of the structure, in particular a force distribution plate.
  • a force distribution element bearing against a surface of the structure, in particular a force distribution plate.
  • Such anchoring can in particular prove useful when reinforcing a cantilevered balcony slab, the force distribution element resting on the free edge of the slab.
  • retaining means are provided to improve the anchoring of the ends of the shape memory frame to the structure in the anchoring zones.
  • At least one of the ends of the frame can thus be equipped (s) with an anchoring sleeve.
  • This sleeve is preferably metallic and fixed by crimping on the frame.
  • the use of anchoring sleeves makes it possible to ensure retention of the reinforcement despite a relatively small sealing depth and makes it possible to adapt the process to structures of small thickness.
  • the sleeve has a rough internal surface, in particular covered with grains of carborundum. This ensures a strong friction between the sleeve and the frame.
  • the method may include the production of at least one housing with a width greater than that of the groove, for receiving an electric current supply clamp.
  • two housings with a width greater than that of the groove are produced for receiving two current supply clamps, in particular in the vicinity of each anchoring zone. This facilitates the activation step, allowing easy connection of the power supply used for activation.
  • Step a) can be preceded by performing the bleeding, which is done using a grinder or groover.
  • the method may include the step of measuring a stress in the reinforcement, at least after the reinforcement has returned to its initial configuration, using a suitable measuring device. This makes it possible to verify the mechanical tensioning of the shape memory reinforcement and the creation of a corresponding prestress in the structure.
  • the measuring device used can thus comprise one or more strain gauges (strain gauges), a crossbow dynamometer, a long-base strain gauge, an optical fiber strain gauge, a device for vibratory analysis by wave measurements with transmitter / receiver, a sensor sensitive to the magnetostriction of the reinforcement or a device for local measurement of the concrete compression, this list not being exhaustive.
  • the measuring device is a crossbow dynamometer.
  • the method may include measuring the temperature of the free portion of the shape memory frame during step c), in particular by means of a non-contact infrared thermometer.
  • the electric current in the armature can be adjusted as a function of the measured temperature in order to bring the armature to a temperature, preferably between 160 and 300 ° C, without bringing the armature to excessive temperature.
  • the method is advantageously applied to the reinforcement of a cantilever slab, in particular a balcony slab.
  • the subject of the invention is also a reinforced structure comprising a cementitious material, the reinforcement having preferably been obtained by implementing the method according to the invention as defined above, the reinforced structure comprising at least one groove in which is placed at least one shape memory reinforcement made of a material can go from an initial configuration to a stretched configuration and then resume the initial configuration by being brought from room temperature to a sufficient temperature, preferably between 160 and 300 ° C, the reinforcement having its ends anchored in the structure and inducing by its mechanical tension a prestressing in the structure, the reinforcement comprising at least one bent end sealed in a borehole of the structure and / or at least one end anchored using a force distribution element resting on the structure.
  • both ends of the frame can be angled, especially both angled at right angles.
  • At least one end of the shape memory frame may be fitted with an anchor sleeve.
  • the two ends can thus each be equipped with an anchoring sleeve.
  • the sleeve is preferably fixed by crimping on the frame.
  • the sleeve preferably has a rough internal surface, in particular covered with carborundum grains.
  • a filler advantageously surrounds the frame in the groove, coming into contact with it. This on the one hand allows the reinforcement to be sealed in the structure, and on the other hand ensures the continuity of the plan of the reinforced structure.
  • At least one reinforcement transverse to the frame can be placed above the kerf.
  • the reinforcement is preferably a reinforcement comprising one or more strips of fabric, in particular of a fabric of carbon fibers.
  • the structure is advantageously a cantilever slab, in particular a balcony slab.
  • Figure 1 is a schematic and partial section of a structure awaiting reinforcement
  • Figure 2 illustrates the drilling of boreholes in the structure
  • FIG. 3 illustrates the construction of the housing for receiving the electric current supply clamps
  • Figure 4 illustrates the execution of the bleeding
  • Figure 5 illustrates the injection of a sealing resin into the housings defined by the boreholes
  • Figure 6 shows the shape memory frame
  • Figure 7 illustrates the installation of the frame in the groove
  • FIG 8 Figure 8 illustrates the activation of the armature
  • Figure 9 illustrates the measurement of the mechanical stress in the shape memory reinforcement
  • Figure 10 illustrates the filling of the bleeding
  • Figure 11 illustrates the installation of an additional transverse reinforcement of carbon fiber fabric
  • Figure 12 shows in isolation, in perspective, an anchoring sleeve
  • Figure 13 shows an alternative embodiment of anchoring the frame
  • Figure 14 shows an alternative embodiment of anchoring the frame.
  • the structure 10 may correspond to a balcony slab extending cantilevered from a supporting structure, for example a floor slab (not shown).
  • the method comprises a first step of delimiting the area to be prestressed, followed by the making of boreholes 33 using a drill 37 as illustrated in Figure 2.
  • the holes 33 are for example made to a depth pn of between 50 and 100mm, for example of about 75mm.
  • the diameter of the boreholes cpi is for example between 10 and 20mm, for example 14mm.
  • the center distance Li between the boreholes 33 minus a constant b corresponds substantially to the length over which it is desired to exert a prestress, the constant b being of the order of 10 to 20mm, for example 14mm.
  • the bores 33 define receiving housings 34 for the ends of the shape memory frame 40, as described below.
  • 34 housings have a depth pf3 which is preferably at least 10 times the diameter of the reinforcement.
  • the depth pf3 can be between 40mm and 100mm, for example around 60mm.
  • housings 35 for receiving clamps 61 for the electric current supply as shown in Figure 3.
  • These housings 35 are for example produced by coring with a substantially circular cross section, for example with a diameter cpi of between 20 and 50mm, for example of about 40mm and to a depth pf2 of between 10 and 30mm, for example of about 15mm .
  • the method then comprises the execution of a groove 30 in the concrete 14 by means of a groover 39, as illustrated in Figure 4.
  • the groove 30 is delimited axially by the holes 33.
  • the groove 30 is for example made with a substantially rectangular cross section, for example about 8 mm to 10 mm in width and 15 mm in depth, as illustrated in Figure 4.
  • the preparation of the shape memory frame 40 can be done in parallel, or alternatively the frames are delivered to the site already prepared.
  • the shape memory frame 40 is preferably in the form of a notched bar. It has for example a diameter of between 5mm and 20mm, for example 6mm and an ability to restore a force by returning to its initial configuration, for example of around 1000 to 1400 daN.
  • the length of the reinforcement corresponds for example to the center distance Li of the boreholes 33, to which is added a constant c of between 100mm and 200mm, for example of approximately 145mm.
  • This shape memory frame 40 is made of an alloy which can go from an initial configuration to a stretched configuration, in particular by a traction exerted on the material at room temperature, then resume the initial configuration by being brought from room temperature to a temperature between 160 and 300 ° C, for example 250 ° C.
  • Shape-memory reinforcements which can be used are, for example, those described in European patent application EP 2 141 251 A1 and marketed by the company RE-FER.
  • the frame 40 is placed in the groove 30 in its stretched configuration.
  • the ends 41 are bent over a radius r c of between 10mm and 20mm, for example of around 15mm.
  • the frame 40 thus has two ends 41 bent at right angles.
  • the ends 41 of the frame 40 are advantageously provided with anchoring sleeves 50, making it possible to seal the frame to relatively shallow depths.
  • the anchor sleeves are preferably hollow hard steel cylinders about 28 mm in length.
  • the external diameters cp mi and internal cp m 2 of each sleeve 50 are for example approximately 10mm and 7mm respectively.
  • the sleeves 50 are preferably fixed by crimping on the ends of the frames 40.
  • the crimping operation consists in crushing the sleeve 50 between two treated steel jaws of a suitable crimping press (not shown).
  • the crushing pressure can be between 5 and 8 tons.
  • Each sleeve 50 preferably has a rough inner surface 52.
  • Such an internal surface is obtained, in the illustrated embodiment, by covering the internal surface with carborundum grains of a size of about 0.3mm to 0.5mm.
  • the sleeves Prior to the application of the carborundum grains, the sleeves are preferably degreased and the internal surface 52 is coated with a thin layer of resin of between 0.1mm and 0.4mm, for example 0.2mm.
  • the excess carborundum is preferably removed and the sleeves are blown with compressed air.
  • the housings 34 are filled with a sealing resin 32 using a resin cartridge 36, as illustrated in Figure 5.
  • the sealing resin 36 is for example an epoxy resin.
  • the ends of the frame equipped with anchor sleeves are then anchored in the housings 34 before the resin sets, while leaving a free portion 42 of the frame 40 without adhesion to the structure 10 within the groove 30.
  • the rise in temperature can be obtained by the Joule effect by the passage of an electric current using an electric current generator 60 of which the terminals equipped with clamps 61 are connected to the ends of the free portion 42 in the housings 35.
  • the temperature in the free portion is advantageously monitored during activation by means of a non-contact infrared thermometer (not shown).
  • Raising the temperature to the values indicated causes the frame 40 to return to its initial configuration. Since the contact between frame 40 and structure 10 is limited, heat losses are reduced.
  • a filler 18 can be injected around the frame 40 under mechanical tension in the groove 30, so as to seal the frame 40 over its entire length and restore the continuity of the plane of the reinforced structure.
  • additional reinforcement 80 for example strips of fabric of carbon fibers, for example Foreva ® TFC (Carbon Fiber Fabrics) as shown in Figure 11.
  • the bands 80 are preferably arranged transversely to the frame.
  • the implementation of the reinforcing strips 80 is preferably carried out at least 24 hours after the sealing of the reinforcements 40 in the groove 30.
  • anchoring of the ends 41 can be done other than by sealing in the housings 33.
  • the anchoring of one end 41 of the frame 40 can be carried out using a force distribution element 54 bearing against a surface of the structure, this element distribution being for example a force distribution plate allowing the diffusion of the prestressing forces in the concrete 14.
  • the distribution plate 54 is for example a rectangular steel plate provided with a bore in its center, to the passage of the frame. This force distribution plate 54 is preferably positioned so that the frame 40 is centered therein.
  • the anchoring of the ends 41 can be carried out other than by resting on the distribution element.
  • the distribution plate can be replaced by a surface housing 90 disposed on the edge of a surface of the structure, and which is filled with a sealing resin.
  • the anchoring of the frame 40 is effected by sealing a right end of the frame 40 provided with the anchoring sleeve 50 in the surface housing 90.
  • the anchoring by sealing the The assembly consisting of the frame 40 and the sleeve 90 in the housing is obtained by applying the sealing resin around the end of the frame in the housing.
  • the reinforcement is made integral with the structure, which makes it possible to diffuse the mechanical prestressing forces in the concrete 14 when the reinforcement returns to its initial position.

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  • Engineering & Computer Science (AREA)
  • Architecture (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Mechanical Engineering (AREA)
  • Reinforcement Elements For Buildings (AREA)
  • Working Measures On Existing Buildindgs (AREA)

Abstract

The invention relates to a method for reinforcing a structure (10) comprising a cementitious material (14), the method comprising the steps of: a) placing, in a recess (30) made in the structure (10), at least one shape-memory reinforcement (40) made of a material that can change from an initial configuration to a stretched configuration and then return to the initial configuration by being brought from ambient temperature to a high enough temperature, preferably between 160°C and 300°C; b) with the reinforcement (40) in its stretched configuration, anchoring the ends (41) of the reinforcement (40) to the structure (10) leaving a free portion (42) of the reinforcement (40) without bonding to the structure (10) within the recess (30); and c) raising the temperature, at least of the free portion (42), to a value, preferably between 160°C and 300°C in order to cause the reinforcement (40) to return to its initial configuration and generate a prestress in the structure (10).

Description

Description Description
Titre : Procédé de renforcement d’une structure. Title: Method of strengthening a structure.
Domaine technique Technical area
La présente invention concerne les travaux de réparation et/ou de renforcement de structures en béton dans le domaine de la construction. Plus particulièrement, l’invention concerne les procédés de réparation et/ou de renforcement de structures mettant en œuvre des armatures à mémoire de forme. The present invention relates to repair and / or reinforcement of concrete structures in the field of construction. More particularly, the invention relates to methods for repairing and / or reinforcing structures using shape memory reinforcements.
Technique antérieure Prior art
Il est connu d’utiliser des armatures à mémoire de forme dans la réparation d’une structure fissurée au moyen des techniques rappelées ci-après. It is known to use shape memory reinforcements in the repair of a cracked structure by means of the techniques recalled below.
L’un des procédés connus consiste à sceller l’armature à mémoire de forme dans une saignée que l’on remplit d’un mortier de scellement après installation de l’armature. L’ensemble constitué de l’armature et du mortier de scellement est ensuite mis en tension mécanique par élévation de la température de l’armature. Un inconvénient de ce procédé est que la mise en tension mécanique de l’armature encastrée dans le mortier de scellement est fortement consommatrice d’énergie du fait de la dissipation thermique engendrée par conduction en raison du contact de l’armature avec le mortier de scellement. En outre, lors de la mise en tension mécanique de l’armature, le béton est soumis localement à une température élevée à cause de réchauffement de l’armature, risquant de générer des fissurations locales pouvant être préjudiciables à la tenue à long terme de la structure. One of the known methods is to seal the shape memory framework in a groove that is filled with a sealing mortar after installation of the framework. The assembly consisting of the framework and the sealing mortar is then placed in mechanical tension by raising the temperature of the framework. A drawback of this method is that the mechanical tensioning of the reinforcement embedded in the sealing mortar consumes a lot of energy due to the heat dissipation generated by conduction due to the contact of the reinforcement with the sealing mortar. . In addition, during the mechanical tensioning of the reinforcement, the concrete is locally subjected to a high temperature because of the heating of the reinforcement, risking generating local cracks which can be detrimental to the long-term resistance of the reinforcement. structure.
Un second procédé connu consiste à placer des armatures à mémoire de forme de section aplatie sur le parement de la structure et à les maintenir par des fixations aux extrémités, telles que des clous en acier plantés dans le béton au moyen d’un pistolet à cartouches explosives. Un inconvénient de cette technique réside notamment dans son incompatibilité avec l’utilisation d’un renfort externe complémentaire. En effet, un tel renfort est soit posé par-dessus l’armature à mémoire de forme préalablement tendue et par conséquent non adhérente à la structure, soit posé préalablement pour être au contact de la structure. Dans ce dernier cas, le risque est que le renfort soit endommagé par la température de l’armature lors de son activation. De plus, en réparation, il est rare que le besoin en renforcement de la structure se limite à une seule direction et l’on est souvent confronté à des besoins de renforcements multiaxiaux, donc faisant appel à de tels renforts externes complémentaires. A second known method consists in placing shape memory reinforcements of flattened section on the facing of the structure and in maintaining them by fasteners at the ends, such as steel nails driven into the concrete by means of a cartridge gun. explosives. A drawback of this technique lies in particular in its incompatibility with the use of an additional external reinforcement. In fact, such a reinforcement is either placed on top of the shape memory frame stretched beforehand and therefore not adherent to the structure, or placed beforehand to be in contact with the structure. In the latter case, the risk is that the reinforcement is damaged by the temperature of the reinforcement during its activation. In addition, in repair, it is rare that the need for reinforcement of the structure is limited to a single direction and one is often confronted with the needs of multiaxial reinforcements, therefore calling on such additional external reinforcements.
Il existe par conséquent un besoin pour améliorer les méthodes de renforcement de structure mettant en œuvre des armatures à mémoire de forme, en particulier pour rendre ces méthodes compatibles avec G utilisation de systèmes complémentaires de renforcement tels que des renforts en tissu de fibres de carbone fixés par collage. There is consequently a need to improve the methods of structural reinforcement using shape memory reinforcements, in particular to make these methods compatible with the use of complementary reinforcement systems such as reinforcements made of fixed carbon fiber fabric. by gluing.
Exposé de l’invention Disclosure of the invention
L’invention vise à répondre à ce besoin et a pour objet, selon l’un de ses aspects, un procédé de renforcement d’une structure comportant un matériau cimentaire, ce procédé comportant les étapes consistant à: The invention aims to meet this need and its subject, according to one of its aspects, is a method for reinforcing a structure comprising a cementitious material, this method comprising the steps of:
a) placer, dans une saignée réalisée dans la structure, au moins une armature à mémoire de forme réalisée dans un matériau pouvant passer d’une configuration initiale à une configuration étirée, puis reprendre la configuration initiale en étant porté depuis la température ambiante à une température suffisante, de préférence comprise entre 160°C et 300°C, par exemple 250°C, a) placing, in a groove made in the structure, at least one shape memory frame made of a material capable of passing from an initial configuration to a stretched configuration, then resuming the initial configuration by being brought from room temperature to a sufficient temperature, preferably between 160 ° C and 300 ° C, for example 250 ° C,
b) l’armature étant dans sa configuration étirée, ancrer les extrémités de l’armature sur la structure tout en laissant une portion libre de l’armature sans adhérence à la structure au sein de la saignée, b) with the reinforcement in its stretched configuration, anchor the ends of the reinforcement to the structure while leaving a free portion of the reinforcement without adhesion to the structure within the groove,
c) élever la température, au moins de la portion libre, à une valeur, de préférence comprise entre 160 et 300°C, pour provoquer le retour de l’armature vers sa configuration initiale et générer une précontrainte (un effort de compression) dans la structure. c) raise the temperature, at least of the free portion, to a value, preferably between 160 and 300 ° C, to cause the reinforcement to return to its initial configuration and generate a prestress (a compressive force) in the structure.
L’invention, en réduisant le transfert thermique entre l’armature à mémoire de forme et la structure du fait que l’activation se fait avant rebouchage de la saignée, facilite la montée en température de l’armature et limite la dissipation de chaleur au sein de la structure, réduisant ainsi les pertes d’énergie et le risque de fragilisation de celle-ci par la chaleur lors de l’activation. The invention, by reducing the heat transfer between the shape memory reinforcement and the structure due to the fact that the activation takes place before filling the groove, facilitates the rise in temperature of the reinforcement and limits the heat dissipation to the surface. within the structure, thus reducing energy losses and the risk of its weakening by heat during activation.
De préférence, l’armature à mémoire de forme passe de sa configuration initiale vers sa configuration étirée par une traction exercée sur l’armature à température ambiante. Le passage dans la configuration étirée peut se faire en usine par exemple, avant livraison de l’armature sur le chantier. De préférence, l’armature se présente sous la forme d’une barre crantée. Celle-ci peut présenter une section transversale de forme sensiblement circulaire ou rectangulaire. En variante, l’armature se présente sous forme de plat. D’une façon générale, toute armature à mémoire de forme apte à être tendue lorsqu’ activée et générant une précontrainte (un effort de compression) dans la structure, peut convenir. Preferably, the shape memory frame passes from its initial configuration to its stretched configuration by a traction exerted on the frame at room temperature. Switching to the stretched configuration can be done in the factory, for example, before delivery of the reinforcement to the site. Preferably, the reinforcement is in the form of a notched bar. The latter may have a cross section of substantially circular or rectangular shape. As a variant, the frame is in the form of a flat. In general, any shape memory reinforcement capable of being tensioned when activated and generating a prestress (a compressive force) in the structure, may be suitable.
Par exemple, le matériau de l’armature à mémoire de forme est un alliage comprenant un alliage de base constitué de manganèse, de silicium, de chrome et de nickel ainsi que d'une proportion massique complémentaire de fer. For example, the material of the shape memory frame is an alloy comprising a base alloy consisting of manganese, silicon, chromium and nickel as well as a complementary proportion by mass of iron.
Des armatures à mémoire de forme utilisables sont par exemple celles décrites dans la demande de brevet européen EP 2 141 251 Al et commercialisées par la société RE-FER. De préférence, le procédé selon l’invention comporte l’étape consistant à injecter un produit de remplissage autour de l’armature dans la saignée, après le retour de l’armature vers sa configuration initiale. Le produit de remplissage peut être une résine ou tout autre matériau de remplissage, par exemple un coulis cimentaire. Shape-memory reinforcements which can be used are, for example, those described in European patent application EP 2 141 251 A1 and marketed by the company RE-FER. Preferably, the method according to the invention includes the step of injecting a filler around the frame in the groove, after the frame has returned to its initial configuration. The filling product can be a resin or any other filling material, for example a cementitious grout.
L’invention permet d’utiliser des matériaux qui seraient incompatibles avec la température d’activation de l’armature si l’activation avait lieu alors que la saignée est déjà rebouchée. Le rebouchage de la saignée permet notamment d’assurer une continuité de surface permettant la pose ultérieure d’un ou plusieurs renforts externes additionnels, ces renforts pouvant parfaitement adhérer à la structure. The invention makes it possible to use materials which would be incompatible with the activation temperature of the framework if the activation took place while the kerf is already closed. The filling of the groove makes it possible in particular to ensure a continuity of surface allowing the subsequent installation of one or more additional external reinforcements, these reinforcements being able to adhere perfectly to the structure.
Le procédé peut ainsi avantageusement comporter la pose, au-dessus de la saignée, d’au moins un renfort transversal à l’armature, de préférence un renfort comportant une ou plusieurs bandes de tissu, notamment un Tissu de Fibres de Carbone (TFC) ou plus généralement un tissu de Polymère Renforcé de Fibres (FRP). De préférence, le renfort transversal est appliqué sur le matériau de remplissage, après durcissement de ce dernier. Le ou les renforts transversaux apportent une résistante additionnelle en traction et en cisaillement à la structure. The method can thus advantageously comprise the installation, above the groove, of at least one reinforcement transverse to the frame, preferably a reinforcement comprising one or more strips of fabric, in particular a carbon fiber fabric (TFC). or more generally a Fiber Reinforced Polymer (FRP) fabric. Preferably, the transverse reinforcement is applied to the filling material, after the latter has hardened. The transverse reinforcement (s) provide additional strength in traction and in shear to the structure.
Lors de l’étape c), l’élévation de la température dans la portion libre est avantageusement obtenue par le passage d’un courant électrique dans celle-ci, mais d’autres méthodes peuvent être utilisées pour réchauffer l’armature à mémoire de forme, telles que l’exposition de l’armature au rayonnement d’une source de lumière UV. Le courant électrique circule entre des points espacés des zones de l’armature ancrées dans la structure, et cela évite de chauffer excessivement les zones ancrées. L’ancrage des extrémités de l’armature dans la structure peut s’effectuer de multiples façons, notamment par ancrages passifs, par exemple par scellement d’au moins une extrémité dans la structure, par exemple à l’aide d’une résine de scellement. During step c), the rise in temperature in the free portion is advantageously obtained by passing an electric current through the latter, but other methods can be used to heat the memory armature from shape, such as exposing the frame to radiation from a UV light source. The electric current flows between points spaced from the zones of the reinforcement anchored in the structure, and this avoids excessively heating the anchored zones. The ends of the reinforcement can be anchored in the structure in many ways, in particular by passive anchoring, for example by sealing at least one end in the structure, for example using a resin of sealing.
Le procédé peut ainsi comporter le forage de la structure pour former au moins un logement de réception d’une extrémité de l’armature, dans laquelle celle-ci est ensuite scellée. The method can thus include drilling the structure to form at least one housing for receiving one end of the frame, in which the latter is then sealed.
Le forage peut être perpendiculaire à la direction de l’armature auquel cas l’armature peut être coudée, notamment à angle droit, pour s’étendre en dehors du logement dans la direction souhaitée. Ainsi, au moins une extrémité de l’armature peut être coudée, de préférence sensiblement à angle droit. De préférence, les deux extrémités de l’armature sont chacune coudée, notamment toutes deux coudées à angle droit. Chacune de ces extrémités peut alors être reçue dans un logement perpendiculaire respectif. The borehole can be perpendicular to the direction of the frame in which case the frame can be bent, especially at a right angle, to extend out of the housing in the desired direction. Thus, at least one end of the frame can be bent, preferably substantially at a right angle. Preferably, the two ends of the frame are each angled, especially both angled at right angles. Each of these ends can then be received in a respective perpendicular housing.
L’ancrage d’au moins une extrémité peut s’obtenir autrement que dans un logement obtenu par forage dans ladite structure. The anchoring of at least one end can be obtained other than in a housing obtained by drilling in said structure.
L’ancrage d’une extrémité de l’armature peut par exemple s’effectuer par scellement dans un logement de surface venant au contact d’une surface de la structure. The anchoring of one end of the frame can for example be effected by sealing in a surface housing coming into contact with a surface of the structure.
Le scellement peut être obtenu par application de résine de scellement autour de l’extrémité de l’armature dans le logement. Cela permet d’immobiliser l’armature dans la structure, permettant ainsi de diffuser les efforts de précontrainte mécanique dans la structure. Sealing can be achieved by applying sealing resin around the end of the frame in the housing. This makes it possible to immobilize the reinforcement in the structure, thus making it possible to diffuse the mechanical prestressing forces in the structure.
L’ancrage des extrémités peut encore s’effectuer autrement que par scellement, par exemple par des techniques d’ancrage similaires à celles utilisées pour les ancrages actifs. The anchoring of the ends can also be done other than by sealing, for example by anchoring techniques similar to those used for active anchors.
L’ancrage d’une extrémité de l’armature peut ainsi s’effectuer par exemple à l’aide d’un élément de répartition d’effort venant en appui contre une surface de la structure, notamment une plaque de répartition d’effort. Un tel ancrage peut notamment s’avérer utile lors du renforcement d’une dalle de balcon en porte à faux, l’élément de répartition d’effort venant en appui sur le bord libre de la dalle. The anchoring of one end of the frame can thus be done, for example, using a force distribution element bearing against a surface of the structure, in particular a force distribution plate. Such anchoring can in particular prove useful when reinforcing a cantilevered balcony slab, the force distribution element resting on the free edge of the slab.
De préférence, des moyens de retenue sont prévus pour améliorer l’ancrage des extrémités de l’armature à mémoire de forme à la structure dans les zones d’ancrage. Preferably, retaining means are provided to improve the anchoring of the ends of the shape memory frame to the structure in the anchoring zones.
Au moins l’une des extrémités de l’armature, mieux les deux extrémités, peuvent ainsi être équipée(s) d’un manchon d’ancrage. Ce manchon est de préférence métallique et fixé par sertissage sur l’armature. L’utilisation de manchons d’ancrage permet d’assurer une retenue de l’armature malgré une profondeur de scellement relativement faible et permet d’adapter le procédé à des structures de faible épaisseur. De préférence, le manchon comporte une surface interne rugueuse, notamment recouverte de grains de carborundum. Cela permet d’assurer une forte friction entre le manchon et l’armature. At least one of the ends of the frame, better still the two ends, can thus be equipped (s) with an anchoring sleeve. This sleeve is preferably metallic and fixed by crimping on the frame. The use of anchoring sleeves makes it possible to ensure retention of the reinforcement despite a relatively small sealing depth and makes it possible to adapt the process to structures of small thickness. Preferably, the sleeve has a rough internal surface, in particular covered with grains of carborundum. This ensures a strong friction between the sleeve and the frame.
Le procédé peut comporter la réalisation d’au moins un logement de largeur supérieure à celle de la saignée, de réception d’une pince d’alimentation en courant électrique. De préférence, on réalise deux logements de largeur supérieure à celle de la saignée pour la réception de deux pinces d’alimentation en courant, notamment au voisinage de chaque zone d’ancrage. Cela facilite l’étape d’activation, en permettant une connexion facile de l’alimentation électrique utilisée pour l’activation. The method may include the production of at least one housing with a width greater than that of the groove, for receiving an electric current supply clamp. Preferably, two housings with a width greater than that of the groove are produced for receiving two current supply clamps, in particular in the vicinity of each anchoring zone. This facilitates the activation step, allowing easy connection of the power supply used for activation.
L’étape a) peut être précédée par la réalisation de la saignée, qui se fait à l’aide d’une disqueuse ou rainureuse. Step a) can be preceded by performing the bleeding, which is done using a grinder or groover.
Le procédé peut comporter l’étape consistant à mesurer une contrainte dans l’armature, au moins après le retour de l’armature vers sa configuration initiale, à l’aide d’un dispositif de mesure adapté. Cela permet de vérifier la mise sous tension mécanique de l’armature à mémoire de forme et la création d’une précontrainte correspondante dans la structure. The method may include the step of measuring a stress in the reinforcement, at least after the reinforcement has returned to its initial configuration, using a suitable measuring device. This makes it possible to verify the mechanical tensioning of the shape memory reinforcement and the creation of a corresponding prestress in the structure.
Le dispositif de mesure utilisé peut ainsi comporter une ou plusieurs jauges (extensométriques) de contrainte, un dynamomètre arbalète, un extensomètre à base longue, un extensomètre à fibre optique, un dispositif d’analyse vibratoire par mesures d’ondes avec émetteur/récepteur, un capteur sensible à la magnétostriction de l’armature ou un dispositif de mesure locale de la compression du béton, cette liste n’étant pas limitative. De préférence, le dispositif de mesure est un dynamomètre arbalète. The measuring device used can thus comprise one or more strain gauges (strain gauges), a crossbow dynamometer, a long-base strain gauge, an optical fiber strain gauge, a device for vibratory analysis by wave measurements with transmitter / receiver, a sensor sensitive to the magnetostriction of the reinforcement or a device for local measurement of the concrete compression, this list not being exhaustive. Preferably, the measuring device is a crossbow dynamometer.
Le procédé peut comporter la mesure de la température de la portion libre de l’armature à mémoire de forme lors de l’étape c), notamment au moyen d’un thermomètre infrarouge sans contact. Le courant électrique dans l’armature peut être réglé en fonction de la température mesurée afin d’amener l’armature à une température, de préférence comprise entre 160 et 300°C, sans pour autant amener l’armature à température excessive. The method may include measuring the temperature of the free portion of the shape memory frame during step c), in particular by means of a non-contact infrared thermometer. The electric current in the armature can be adjusted as a function of the measured temperature in order to bring the armature to a temperature, preferably between 160 and 300 ° C, without bringing the armature to excessive temperature.
Le procédé est avantageusement appliqué au renforcement d’une dalle en porte-à-faux, notamment d’une dalle de balcon. The method is advantageously applied to the reinforcement of a cantilever slab, in particular a balcony slab.
L’invention a encore pour objet une structure renforcée comprenant un matériau cimentaire, le renforcement ayant de préférence été obtenu par la mise en œuvre du procédé selon l’invention tel que défini plus haut, la structure renforcée comportant au moins une saignée dans laquelle est placée au moins une armature à mémoire de forme réalisée dans un matériau pouvant passer d’une configuration initiale à une configuration étirée puis reprendre la configuration initiale en étant porté depuis la température ambiante à une température suffisante, de préférence comprise entre 160 et 300°C, l’armature ayant ses extrémités ancrées dans la structure et induisant par sa tension mécanique une précontrainte dans la structure, l’armature comportant au moins une extrémité coudée scellée dans un forage de la structure et/ou au moins une extrémité ancrée à l’aide d’un élément de répartition d’effort en appui sur la structure. The subject of the invention is also a reinforced structure comprising a cementitious material, the reinforcement having preferably been obtained by implementing the method according to the invention as defined above, the reinforced structure comprising at least one groove in which is placed at least one shape memory reinforcement made of a material can go from an initial configuration to a stretched configuration and then resume the initial configuration by being brought from room temperature to a sufficient temperature, preferably between 160 and 300 ° C, the reinforcement having its ends anchored in the structure and inducing by its mechanical tension a prestressing in the structure, the reinforcement comprising at least one bent end sealed in a borehole of the structure and / or at least one end anchored using a force distribution element resting on the structure.
Comme mentionné plus haut, les deux extrémités de l’armature peuvent être coudées, notamment toutes deux coudées à angle droit. As mentioned above, both ends of the frame can be angled, especially both angled at right angles.
Comme indiqué précédemment, dans le but d’améliorer l’ancrage de l’armature dans la structure, au moins une extrémité de l’armature à mémoire de forme peut être équipée d’un manchon d’ancrage. Les deux extrémités peuvent ainsi être équipées chacune d’un manchon d’ancrage. Le manchon est de préférence fixé par sertissage sur l’armature. Le manchon comporte de préférence une surface interne rugueuse, notamment recouverte de grains de carborundum. As previously indicated, in order to improve the anchoring of the frame in the structure, at least one end of the shape memory frame may be fitted with an anchor sleeve. The two ends can thus each be equipped with an anchoring sleeve. The sleeve is preferably fixed by crimping on the frame. The sleeve preferably has a rough internal surface, in particular covered with carborundum grains.
Un produit de remplissage entoure avantageusement l’armature dans la saignée, en venant à son contact. Cela permet d’une part le scellement d’armature dans la structure, et d’autre part assure la continuité du plan de la structure renforcée. A filler advantageously surrounds the frame in the groove, coming into contact with it. This on the one hand allows the reinforcement to be sealed in the structure, and on the other hand ensures the continuity of the plan of the reinforced structure.
Au moins un renfort transversal à l’armature peut être posé au-dessus de la saignée. Le renfort est de préférence un renfort comportant une ou plusieurs bandes de tissu, notamment d’un tissu de fibres de carbone. At least one reinforcement transverse to the frame can be placed above the kerf. The reinforcement is preferably a reinforcement comprising one or more strips of fabric, in particular of a fabric of carbon fibers.
La structure est avantageusement une dalle en porte-à-faux, notamment d’une dalle de balcon. The structure is advantageously a cantilever slab, in particular a balcony slab.
Brève description des dessins Brief description of the drawings
L’invention pourra être mieux comprise à la lecture de la description détaillée qui va suivre, d’exemples de mise en œuvre non limitatifs de celle-ci, et à l’examen du dessin annexé, sur lequel : The invention may be better understood from reading the detailed description which follows, of non-limiting examples of implementation thereof, and by examining the appended drawing, in which:
[Fig 1] la figure 1 est une coupe schématique et partielle d’une structure en attente de renforcement, [Fig 1] Figure 1 is a schematic and partial section of a structure awaiting reinforcement,
[Fig 2] la figure 2 illustre la réalisation des forages dans la structure, [Fig 2] Figure 2 illustrates the drilling of boreholes in the structure,
[Fig 3] la figure 3 illustre la réalisation des logements de réception des pinces d’alimentation en courant électrique, [Fig 4] la figure 4 illustre l’exécution de la saignée, [Fig 3] FIG. 3 illustrates the construction of the housing for receiving the electric current supply clamps, [Fig 4] Figure 4 illustrates the execution of the bleeding,
[Fig 5] la figure 5 illustre l’injection d’une résine de scellement dans les logements définis par les forages, [Fig 5] Figure 5 illustrates the injection of a sealing resin into the housings defined by the boreholes,
[Fig 6] la figure 6 représente l’armature à mémoire de forme, [Fig 6] Figure 6 shows the shape memory frame,
[Fig 7] la figure 7 illustre l’installation de l’armature dans la saignée, [Fig 7] Figure 7 illustrates the installation of the frame in the groove,
[Fig 8] la figure 8 illustre l’activation de l’armature, [Fig 8] Figure 8 illustrates the activation of the armature,
[Fig 9] la figure 9 illustre la mesure de la contrainte mécanique dans l’armature à mémoire de forme, [Fig 9] Figure 9 illustrates the measurement of the mechanical stress in the shape memory reinforcement,
[Fig 10] la figure 10 illustre le remplissage de la saignée, [Fig 10] Figure 10 illustrates the filling of the bleeding,
[Fig 11] la figure 11 illustre la pose d’un renforcement additionnel transversal de tissu de fibres de carbone, [Fig 11] Figure 11 illustrates the installation of an additional transverse reinforcement of carbon fiber fabric,
[Fig 12] la figure 12 représente isolément, en perspective, un manchon d’ancrage, [Fig 12] Figure 12 shows in isolation, in perspective, an anchoring sleeve,
[Fig 13] la figure 13 représente une variante de réalisation d’ancrage de l’armature, et [Fig 13] Figure 13 shows an alternative embodiment of anchoring the frame, and
[Fig 14] la figure 14 représente une variante de réalisation d’ancrage de l’armature. [Fig 14] Figure 14 shows an alternative embodiment of anchoring the frame.
Description détaillée detailed description
On va décrire en référence aux figures 1 à 11 un exemple de procédé de renforcement selon l’invention, appliqué à une structure fissurée 10 en béton 14, notamment en béton armé. La structure 10 peut correspondre à une dalle de balcon s’étendant en porte à faux à partir d’une structure porteuse, par exemple une dalle de plancher (non représentée). With reference to Figures 1 to 11, an example of a reinforcement method according to the invention, applied to a cracked structure 10 made of concrete 14, in particular reinforced concrete, will be described. The structure 10 may correspond to a balcony slab extending cantilevered from a supporting structure, for example a floor slab (not shown).
Le procédé comporte une première étape de délimitation de la zone à précontraindre, suivie par la réalisation de forages 33 à l’aide d’une perceuse 37 comme illustré à la figure 2. The method comprises a first step of delimiting the area to be prestressed, followed by the making of boreholes 33 using a drill 37 as illustrated in Figure 2.
Dans l’exemple considéré, les forages 33 sont par exemple réalisés sur une profondeur pn comprise entre 50 et 100mm, par exemple d’environ 75mm. Le diamètre des forages cpi est par exemple compris entre 10 et 20mm, par exemple de 14mm. L’entraxe Li entre les forages 33 moins une constante b correspond sensiblement à la longueur sur laquelle on souhaite exercer une précontrainte, la constante b étant de l’ordre de 10 à 20mm, par exemple de 14mm. In the example considered, the holes 33 are for example made to a depth pn of between 50 and 100mm, for example of about 75mm. The diameter of the boreholes cpi is for example between 10 and 20mm, for example 14mm. The center distance Li between the boreholes 33 minus a constant b corresponds substantially to the length over which it is desired to exert a prestress, the constant b being of the order of 10 to 20mm, for example 14mm.
Les forages 33 définissent des logements de réception 34 pour les extrémités de l’armature à mémoire de forme 40, comme décrit plus loin. Les logements 34 ont une profondeur pf3 qui est de préférence au moins 10 fois le diamètre de l’armature. La profondeur pf3 peut être comprise entre 40mm et 100mm, par exemple d’environ 60mm. The bores 33 define receiving housings 34 for the ends of the shape memory frame 40, as described below. 34 housings have a depth pf3 which is preferably at least 10 times the diameter of the reinforcement. The depth pf3 can be between 40mm and 100mm, for example around 60mm.
Une fois les forages 33 percés, on peut réaliser des logements 35 de réception de pinces 61 d’alimentation en courant électrique, comme illustré à la figure 3. Once the boreholes 33 have been drilled, it is possible to make housings 35 for receiving clamps 61 for the electric current supply, as shown in Figure 3.
Ces logements 35 sont par exemple réalisés par carottage avec une section transversale sensiblement circulaire, par exemple de diamètre cpi compris entre 20 et 50mm, par exemple d’environ 40mm et sur une profondeur pf2 comprise entre 10 et 30mm, par exemple d’environ 15mm. These housings 35 are for example produced by coring with a substantially circular cross section, for example with a diameter cpi of between 20 and 50mm, for example of about 40mm and to a depth pf2 of between 10 and 30mm, for example of about 15mm .
Le procédé comporte ensuite l’exécution d’une saignée 30 dans le béton 14 au moyen d’une rainureuse 39, comme illustré à la figure 4. La saignée 30 est délimitée axialement par les forages 33. The method then comprises the execution of a groove 30 in the concrete 14 by means of a groover 39, as illustrated in Figure 4. The groove 30 is delimited axially by the holes 33.
La saignée 30 est par exemple réalisée avec une section transversale sensiblement rectangulaire, par exemple d’environ 8 mm à 10mm de largeur et sur 15 mm de profondeur, comme illustré à la figure 4. The groove 30 is for example made with a substantially rectangular cross section, for example about 8 mm to 10 mm in width and 15 mm in depth, as illustrated in Figure 4.
La préparation de l’armature à mémoire de forme 40 peut s’effectuer en parallèle, ou en variante les armatures sont livrées sur le chantier déjà préparées. The preparation of the shape memory frame 40 can be done in parallel, or alternatively the frames are delivered to the site already prepared.
L’armature à mémoire de forme 40 est de préférence sous forme d’une barre crantée. Elle a par exemple un diamètre compris entre 5mm et 20mm, par exemple de 6mm et une capacité à restituer une force par retour vers sa configuration initiale par exemple d’environ 1000 à 1400 daN. La longueur de l’armature correspond par exemple à l’entraxe Li des forages 33, auquel on ajoute une constante c comprise entre 100mm et 200mm, par exemple d’environ 145mm. The shape memory frame 40 is preferably in the form of a notched bar. It has for example a diameter of between 5mm and 20mm, for example 6mm and an ability to restore a force by returning to its initial configuration, for example of around 1000 to 1400 daN. The length of the reinforcement corresponds for example to the center distance Li of the boreholes 33, to which is added a constant c of between 100mm and 200mm, for example of approximately 145mm.
Cette armature à mémoire de forme 40 est réalisée dans un alliage pouvant passer d’une configuration initiale à une configuration étirée, notamment par une traction exercée sur le matériau à température ambiante, puis reprendre la configuration initiale en étant porté depuis la température ambiante à une température comprise entre 160 et 300°C, par exemple 250°C. This shape memory frame 40 is made of an alloy which can go from an initial configuration to a stretched configuration, in particular by a traction exerted on the material at room temperature, then resume the initial configuration by being brought from room temperature to a temperature between 160 and 300 ° C, for example 250 ° C.
Des armatures à mémoire de forme utilisables sont par exemple celles décrites dans la demande de brevet européen EP 2 141 251 Al et commercialisées par la société RE-FER. Dans le mode de réalisation illustré, l’armature 40 est posée dans la saignée 30 dans sa configuration étirée. Comme illustré à la figure 6, on réalise un cintrage des extrémités 41 sur un rayon rc compris entre 10mm et 20mm, par exemple d’environ 15mm. L’armature 40 présente ainsi deux extrémités 41 coudées à angle droit. Shape-memory reinforcements which can be used are, for example, those described in European patent application EP 2 141 251 A1 and marketed by the company RE-FER. In the illustrated embodiment, the frame 40 is placed in the groove 30 in its stretched configuration. As illustrated in FIG. 6, the ends 41 are bent over a radius r c of between 10mm and 20mm, for example of around 15mm. The frame 40 thus has two ends 41 bent at right angles.
Les extrémités 41 de l’armature 40 sont avantageusement munies de manchons d’ancrage 50, permettant d’assurer le scellement de l’armature sur des profondeurs relativement faibles. Les manchons d’ancrage sont de préférence des cylindres creux en acier dur d’environ 28 mm de longueur. Les diamètres externe cpmi et interne cpm2 de chaque manchon 50 sont par exemple d’environ 10mm et 7mm respectivement. The ends 41 of the frame 40 are advantageously provided with anchoring sleeves 50, making it possible to seal the frame to relatively shallow depths. The anchor sleeves are preferably hollow hard steel cylinders about 28 mm in length. The external diameters cp mi and internal cp m 2 of each sleeve 50 are for example approximately 10mm and 7mm respectively.
Les manchons 50 sont de préférence fixés par sertissage sur les extrémités des armatures 40. L’opération de sertissage consiste à écraser le manchon 50 entre deux mâchoires en acier traité d’une presse de sertissage adaptée (non représentée). La pression d’écrasement peut être comprise entre 5 et 8 tonnes. The sleeves 50 are preferably fixed by crimping on the ends of the frames 40. The crimping operation consists in crushing the sleeve 50 between two treated steel jaws of a suitable crimping press (not shown). The crushing pressure can be between 5 and 8 tons.
Chaque manchon 50 comporte de préférence une surface interne 52 rugueuse. Une telle surface interne est obtenue, dans le mode de réalisation illustré, par recouvrement de la surface interne de grains de carborundum d’un calibre d’environ 0.3mm à 0.5mm. Each sleeve 50 preferably has a rough inner surface 52. Such an internal surface is obtained, in the illustrated embodiment, by covering the internal surface with carborundum grains of a size of about 0.3mm to 0.5mm.
Préalablement à l’application des grains de carborundum, les manchons sont de préférence dégraissés et la surface interne 52 est enduite d’une couche mince de résine comprise entre 0.1mm et 0.4mm, par exemple 0.2mm. Prior to the application of the carborundum grains, the sleeves are preferably degreased and the internal surface 52 is coated with a thin layer of resin of between 0.1mm and 0.4mm, for example 0.2mm.
Après durcissement de la résine, l’excédent de carborundum est de préférence retiré et les manchons sont passés au soufflage à air comprimé. After the resin has hardened, the excess carborundum is preferably removed and the sleeves are blown with compressed air.
Les logements 34 sont remplis d’une résine de scellement 32 à l’aide d’une cartouche de résine 36, comme illustré à la figure 5. La résine de scellement 36 est par exemple une résine époxyde. The housings 34 are filled with a sealing resin 32 using a resin cartridge 36, as illustrated in Figure 5. The sealing resin 36 is for example an epoxy resin.
Les extrémités de l’armature équipées des manchons d’ancrage sont ensuite ancrées dans les logements 34 avant prise de la résine, tout en laissant une portion libre 42 de l’armature 40 sans adhérence à la structure 10 au sein de la saignée 30. The ends of the frame equipped with anchor sleeves are then anchored in the housings 34 before the resin sets, while leaving a free portion 42 of the frame 40 without adhesion to the structure 10 within the groove 30.
Une fois les extrémités 41 scellées, on procède à la mise en tension mécanique de l’armature 40. Celle-ci est obtenue par élévation de la température de la portion libre entre 160 et 300°C, ce qui provoque le retour de l’armature vers sa configuration initiale, générant ainsi une précontrainte dans la structure. Once the ends 41 are sealed, one proceeds to the mechanical tensioning of the frame 40. This is obtained by raising the temperature of the free portion between 160 and 300 ° C, which causes the return of the. reinforcement towards its initial configuration, thus generating a prestress in the structure.
Comme illustré à la figure 8, l’élévation de la température peut être obtenue par effet Joule par le passage d’un courant électrique à l’aide d’un générateur de courant électrique 60 dont les bornes équipées de pinces 61 sont branchées aux extrémités de la portion libre 42 dans les logements 35. As illustrated in FIG. 8, the rise in temperature can be obtained by the Joule effect by the passage of an electric current using an electric current generator 60 of which the terminals equipped with clamps 61 are connected to the ends of the free portion 42 in the housings 35.
La température dans la portion libre est avantageusement, suivie durant l’activation, au moyen d’un thermomètre infrarouge sans contact (non illustré). The temperature in the free portion is advantageously monitored during activation by means of a non-contact infrared thermometer (not shown).
L’élévation de la température aux valeurs indiquées produit le retour de l’armature 40 vers sa configuration initiale. Du fait que le contact entre l’armature 40 et la structure 10 est limité, les pertes thermiques sont réduites. Raising the temperature to the values indicated causes the frame 40 to return to its initial configuration. Since the contact between frame 40 and structure 10 is limited, heat losses are reduced.
Il est possible de mesurer la contrainte mécanique dans l’armature 40 à l’aide d’un dynamomètre arbalète 70, par exemple, tel que sur la figure 9. Cela permet de s’assurer de l’application de la précontrainte dans la structure et donc du respect de conformité. It is possible to measure the mechanical stress in the frame 40 using a crossbow dynamometer 70, for example, as in FIG. 9. This makes it possible to ensure the application of the prestress in the structure. and therefore respect for compliance.
Ensuite, on peut injecter un produit de remplissage 18 autour de l’armature 40 sous tension mécanique dans la saignée 30, de manière à sceller l’armature 40 sur toute sa longueur et rétablir une continuité du plan de la structure renforcée. Then, a filler 18 can be injected around the frame 40 under mechanical tension in the groove 30, so as to seal the frame 40 over its entire length and restore the continuity of the plane of the reinforced structure.
Si approprié, on peut mettre en place un renforcement additionnel 80, par exemple de bandes de tissu de fibres de carbone, par exemple Foreva® TFC (Tissu de Fibres de Carbone), comme illustré à la figure 11. If appropriate, one can establish additional reinforcement 80, for example strips of fabric of carbon fibers, for example Foreva ® TFC (Carbon Fiber Fabrics) as shown in Figure 11.
Fes bandes 80 sont de préférence disposées dans le sens transversal à l’armature. Fa mise en œuvre des bandes de renfort 80 s’effectue de préférence au moins 24 heures après le scellement des armatures 40 dans la saignée 30. The bands 80 are preferably arranged transversely to the frame. The implementation of the reinforcing strips 80 is preferably carried out at least 24 hours after the sealing of the reinforcements 40 in the groove 30.
Bien entendu, l’invention n’est pas limitée à l’exemple qui vient d’être décrit. Of course, the invention is not limited to the example which has just been described.
Par exemple, l’ancrage des extrémités 41 peut s’effectuer autrement que par scellement dans les logements 33. For example, the anchoring of the ends 41 can be done other than by sealing in the housings 33.
Comme illustré à la figure 13, l’ancrage d’une extrémité 41 de l’armature 40 peut s’effectuer à l’aide d’un élément de répartition d’effort 54 venant en appui contre une surface de la structure, cet élément de répartition étant par exemple une plaque de répartition d’effort permettant la diffusion des efforts de précontrainte dans le béton 14. Fa plaque de répartition 54 est par exemple une plaque d’acier de forme rectangulaire munie d’un perçage en son centre, pour le passage de l’armature. Cette plaque de répartition d’effort 54 est de préférence positionnée afin que l’armature 40 soit centrée dans celle-ci. As illustrated in FIG. 13, the anchoring of one end 41 of the frame 40 can be carried out using a force distribution element 54 bearing against a surface of the structure, this element distribution being for example a force distribution plate allowing the diffusion of the prestressing forces in the concrete 14. The distribution plate 54 is for example a rectangular steel plate provided with a bore in its center, to the passage of the frame. This force distribution plate 54 is preferably positioned so that the frame 40 is centered therein.
F’ancrage des extrémités 41 peut s’effectuer autrement que par appui sur l’élément de répartition. Dans l’exemple illustré à la figure 14, la plaque de répartition peut être remplacée par un logement de surface 90 disposé sur le bord d’une surface de la structure, et que l’on remplit d’une résine de scellement. The anchoring of the ends 41 can be carried out other than by resting on the distribution element. In the example illustrated in FIG. 14, the distribution plate can be replaced by a surface housing 90 disposed on the edge of a surface of the structure, and which is filled with a sealing resin.
Dans ce mode de réalisation, l’ancrage de l’armature 40 s’effectue par scellement d’une extrémité droite de l’armature 40 munie du manchon d’ancrage 50 dans le logement de surface 90. L’ancrage par scellement de l’ensemble constitué de l’armature 40 et du manchon 90 dans le logement est obtenu par application de la résine de scellement autour de l’extrémité de l’armature dans le logement. Ainsi, l’armature est rendue solidaire de la structure, ce qui permet de diffuser les efforts de précontrainte mécanique dans le béton 14 lors du retour de l’armature vers sa position initiale. In this embodiment, the anchoring of the frame 40 is effected by sealing a right end of the frame 40 provided with the anchoring sleeve 50 in the surface housing 90. The anchoring by sealing the The assembly consisting of the frame 40 and the sleeve 90 in the housing is obtained by applying the sealing resin around the end of the frame in the housing. Thus, the reinforcement is made integral with the structure, which makes it possible to diffuse the mechanical prestressing forces in the concrete 14 when the reinforcement returns to its initial position.
Les variantes décrites aux figures 13 et 14, s’avèrent utile lors du renforcement d’une dalle de balcon en porte à faux, l’élément de répartition d’effort venant en appui sur le bord libre de la dalle. The variants described in Figures 13 and 14 are useful when reinforcing a cantilevered balcony slab, the force distribution element resting on the free edge of the slab.

Claims

Revendications Claims
1. Procédé de renforcement d’une structure (10) comportant un matériau cimentaire (14), le procédé comportant les étapes consistant à : 1. Method for reinforcing a structure (10) comprising a cementitious material (14), the method comprising the steps of:
a) placer, dans une saignée (30) réalisée dans la structure (10), au moins une armature à mémoire de forme (40) réalisée dans un matériau pouvant passer d’une configuration initiale à une configuration étirée, puis reprendre la configuration initiale en étant porté depuis la température ambiante à une température suffisante, de préférence comprise entre 160 et 300°C, a) placing, in a groove (30) made in the structure (10), at least one shape memory frame (40) made of a material that can pass from an initial configuration to a stretched configuration, then resume the initial configuration by being brought from room temperature to a sufficient temperature, preferably between 160 and 300 ° C,
b) l’armature (40) étant dans sa configuration étirée, ancrer les extrémités (41) de l’armature (40) sur la structure (10) tout en laissant une portion libre (42) de l’armature (40) sans adhérence à la structure (10) au sein de la saignée (30), b) the frame (40) being in its stretched configuration, anchor the ends (41) of the frame (40) to the structure (10) while leaving a free portion (42) of the frame (40) without adhesion to the structure (10) within the bleeding (30),
c) élever la température, au moins de la portion libre (42), à une valeur, de préférence comprise entre 160 et 300°C, pour provoquer le retour de l’armature (40) vers sa configuration initiale et générer une précontrainte dans la structure (10). c) raising the temperature, at least of the free portion (42), to a value, preferably between 160 and 300 ° C, to cause the reinforcement (40) to return to its initial configuration and generate a prestress in structure (10).
2. Procédé selon la revendication 1, comportant l’étape consistant à injecter un produit de remplissage (18) autour de l’armature (40) dans la saignée (30), après le retour de l’armature 2. The method of claim 1, comprising the step of injecting a filler (18) around the frame (40) in the groove (30), after the return of the frame
(40) vers sa configuration initiale. (40) to its initial configuration.
3. Procédé selon la revendication 1 ou 2, comportant la pose, au-dessus de la saignée (30), d’au moins un renfort (80) transversal à l’armature (40), de préférence un renfort (80) comportant une ou plusieurs bandes de tissu, notamment d’un tissu de fibres de carbone. 3. The method of claim 1 or 2, comprising the installation, above the groove (30), at least one reinforcement (80) transverse to the frame (40), preferably a reinforcement (80) comprising one or more strips of fabric, in particular a fabric of carbon fibers.
4. Procédé selon l’une quelconque des revendications précédentes, l’élévation de la température dans la portion libre (42) étant obtenue par le passage d’un courant électrique dans celle-ci ou par exposition de l’armature (40) au rayonnement d’une source de lumière UV. 4. Method according to any one of the preceding claims, the rise in temperature in the free portion (42) being obtained by the passage of an electric current therein or by exposure of the armature (40) to the radiation from a UV light source.
5. Procédé selon l’une quelconque des revendications précédentes, comportant le forage de la structure (10) pour définir au moins un logement (33, 34) de réception d’une extrémité de l’armature (40) dans laquelle celle-ci est scellée. 5. Method according to any one of the preceding claims, comprising drilling the structure (10) to define at least one housing (33, 34) for receiving one end of the frame (40) in which the latter. is sealed.
6. Procédé selon l’une quelconque des revendications précédentes, au moins une extrémité 6. Method according to any one of the preceding claims, at least one end
(41) de l’armature (40) étant coudée, de préférence sensiblement à angle droit, les deux extrémités (41) de l’armature (40) étant de préférence chacune coudée, notamment toutes deux coudées à angle droit. (41) of the frame (40) being bent, preferably substantially at a right angle, the two ends (41) of the frame (40) being preferably each bent, in particular both bent at right angles.
7. Procédé selon l’une quelconque des revendications précédentes, l’ancrage d’une extrémité (41) de l’armature (40) s’effectuant à l’aide d’un élément de répartition d’effort (54) venant en appui contre une surface de la structure, notamment une plaque de répartition d’effort.7. Method according to any one of the preceding claims, the anchoring of one end (41) of the frame (40) being effected by means of a force distribution element (54) coming in. bearing against a surface of the structure, in particular a force distribution plate.
8. Procédé selon l’une quelconque des revendications précédentes, l’ancrage d’une extrémité (41) de l’armature (40) s’effectuant par scellement de ladite extrémité (41) dans un logement de surface (90) venant au contact d’une surface de la structure (10). 8. Method according to any one of the preceding claims, the anchoring of one end (41) of the frame (40) being effected by sealing said end (41) in a surface housing (90) coming to the contact of a surface of the structure (10).
9. Procédé selon l’une quelconque des revendications précédentes, au moins l’une des extrémités (41) de l’armature (40), mieux les deux extrémités (41), étant équipée(s) d’un manchon d’ancrage (50), ce manchon (50) étant de préférence fixé par sertissage sur l’armature (40), comportant de préférence une surface interne (52) rugueuse, notamment recouverte de grains de carborundum. 9. Method according to any one of the preceding claims, at least one of the ends (41) of the frame (40), better still the two ends (41), being equipped (s) with an anchoring sleeve. (50), this sleeve (50) being preferably fixed by crimping on the frame (40), preferably comprising a rough internal surface (52), in particular covered with carborundum grains.
10. Procédé selon l’une quelconque des revendications précédentes, comportant la réalisation d’au moins un logement (35) de largeur supérieure à celle de la saignée (30), de réception d’une pince (61) d’alimentation en courant électrique. 10. Method according to any one of the preceding claims, comprising the production of at least one housing (35) of greater width than that of the groove (30), for receiving a clamp (61) for supplying current. electric.
11. Procédé selon l’une quelconque des revendications précédentes, l’étape a) étant précédée par la réalisation de la saignée (30). 11. Method according to any one of the preceding claims, step a) being preceded by performing the bleeding (30).
12. Procédé selon l’une quelconque des revendications précédentes, comportant l’étape consistant à mesurer une contrainte dans l’armature (40) au moins après le retour de l’armature (40) vers sa configuration initiale, notamment à l’aide d’un dynamomètre arbalète (70). 12. Method according to any one of the preceding claims, comprising the step of measuring a stress in the reinforcement (40) at least after the return of the reinforcement (40) to its initial configuration, in particular using a crossbow dynamometer (70).
13. Procédé selon l’une quelconque des revendications précédentes, comportant la mesure de la température de la portion libre (42) lors de l’étape c), notamment au moyen d’un thermomètre infrarouge sans contact. 13. Method according to any one of the preceding claims, comprising measuring the temperature of the free portion (42) during step c), in particular by means of a non-contact infrared thermometer.
14. Procédé selon l’une quelconque des revendications précédentes, étant appliqué au renforcement d’une dalle en porte-à-faux, notamment d’une dalle de balcon. 14. Method according to any one of the preceding claims, being applied to the reinforcement of a cantilevered slab, in particular of a balcony slab.
15. Structure renforcée comprenant un matériau cimentaire, le renforcement ayant de préférence été obtenu par la mise en œuvre du procédé selon l’une quelconque des revendications précédentes, la structure renforcée comportant au moins une saignée (30) dans laquelle est placée au moins une armature à mémoire de forme (40) réalisée dans un matériau pouvant passer d’une configuration initiale à une configuration étirée, puis reprendre la configuration initiale en étant porté depuis la température ambiante à une température suffisante, de préférence comprise entre 160 et 300°C, l’armature (40) ayant ses extrémités (41) ancrées dans la structure et induisant par sa tension mécanique lors du retour à la configuration initiale une précontrainte dans la structure (10), l’armature (40) comportant au moins une extrémité (41) coudée scellée dans un forage (33) de la structure (10) et/ou au moins une extrémité (41) ancrée à l’aide d’un élément de répartition d’effort (54) en appui sur la structure (10) et/ou au moins une extrémité (41) scellée dans un logement de surface (90) venant au contact d’une surface de la structure. 15. Reinforced structure comprising a cementitious material, the reinforcement having preferably been obtained by the implementation of the method according to any one of the preceding claims, the reinforced structure comprising at least one groove (30) in which is placed at least one. shape memory reinforcement (40) made of a material capable of changing from an initial configuration to a stretched configuration, then returning to the initial configuration by being brought from room temperature to a sufficient temperature, preferably between 160 and 300 ° C , the frame (40) having its ends (41) anchored in the structure and inducing by its mechanical tension during the return to the initial configuration a prestressing in the structure (10), the reinforcement (40) comprising at least one bent end (41) sealed in a borehole ( 33) of the structure (10) and / or at least one end (41) anchored using a force distribution element (54) resting on the structure (10) and / or at least one end (41) sealed in a surface housing (90) contacting a surface of the structure.
16. Structure selon la revendication 15, les deux extrémités (41) de l’armature (40) étant chacune coudée, notamment toutes deux coudées à angle droit. 16. Structure according to claim 15, the two ends (41) of the frame (40) each being bent, in particular both bent at right angles.
17. Structure selon l’une quelconque des revendications 15 et 16, au moins un renfort (80) transversal à l’armature (40) étant posé au-dessus de la saignée (30), de préférence un renfort 17. Structure according to any one of claims 15 and 16, at least one reinforcement (80) transverse to the frame (40) being placed above the groove (30), preferably a reinforcement
(80) comportant une ou plusieurs bandes de tissu, notamment d’un tissu de fibres de carbone.(80) comprising one or more strips of fabric, in particular a fabric of carbon fibers.
18. Structure selon l’une quelconque des revendications 15 à 17, un produit de remplissage (18) entourant l’armature dans la saignée (30), en venant à son contact. 18. Structure according to any one of claims 15 to 17, a filler (18) surrounding the frame in the groove (30), coming into contact with it.
19. Structure selon l’une quelconque des revendications 15 à 18, au moins l’une des extrémités (41) de l’armature (40), mieux les deux extrémités (41), étant équipée(s) d’un manchon d’ancrage (50), ce manchon (50) étant de préférence fixé par sertissage sur l’armature, comportant de préférence une surface interne (52) rugueuse, notamment recouverte de grains de carborundum. 19. Structure according to any one of claims 15 to 18, at least one of the ends (41) of the frame (40), better still the two ends (41), being equipped (s) with a sleeve d anchoring (50), this sleeve (50) preferably being fixed by crimping on the frame, preferably comprising a rough internal surface (52), in particular covered with carborundum grains.
20. Structure selon l’une quelconque des revendications 15 à 19, la structure (10) étant une dalle en porte-à-faux, notamment une dalle de balcon. 20. Structure according to any one of claims 15 to 19, the structure (10) being a cantilever slab, in particular a balcony slab.
PCT/EP2020/064049 2019-05-23 2020-05-20 Method for reinforcing a structure WO2020234341A1 (en)

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