WO2021013765A1 - Method for measuring the residual prestress in a reinforcement - Google Patents

Method for measuring the residual prestress in a reinforcement Download PDF

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Publication number
WO2021013765A1
WO2021013765A1 PCT/EP2020/070380 EP2020070380W WO2021013765A1 WO 2021013765 A1 WO2021013765 A1 WO 2021013765A1 EP 2020070380 W EP2020070380 W EP 2020070380W WO 2021013765 A1 WO2021013765 A1 WO 2021013765A1
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WO
WIPO (PCT)
Prior art keywords
frame
reinforcement
traction
exerted
claw
Prior art date
Application number
PCT/EP2020/070380
Other languages
French (fr)
Inventor
Bernard Basile
Nicolas DEQUIREZ
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 WO2021013765A1 publication Critical patent/WO2021013765A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
    • G01L5/0028—Force sensors associated with force applying means
    • G01L5/0033—Force sensors associated with force applying means applying a pulling force
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
    • G01L5/0047—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes measuring forces due to residual stresses
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
    • G01L5/04—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring tension in flexible members, e.g. ropes, cables, wires, threads, belts or bands
    • G01L5/10—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring tension in flexible members, e.g. ropes, cables, wires, threads, belts or bands using electrical means
    • G01L5/102—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring tension in flexible members, e.g. ropes, cables, wires, threads, belts or bands using electrical means using sensors located at a non-interrupted part of the flexible member
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
    • G01L5/04—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring tension in flexible members, e.g. ropes, cables, wires, threads, belts or bands
    • G01L5/10—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring tension in flexible members, e.g. ropes, cables, wires, threads, belts or bands using electrical means
    • G01L5/107—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring tension in flexible members, e.g. ropes, cables, wires, threads, belts or bands using electrical means for measuring a reaction force applied on an element disposed between two supports, e.g. on a plurality of rollers or gliders
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
    • G01M5/0041—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress
    • G01M5/005—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress by means of external apparatus, e.g. test benches or portable test systems
    • G01M5/0058—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress by means of external apparatus, e.g. test benches or portable test systems of elongated objects, e.g. pipes, masts, towers or railways

Definitions

  • the present invention relates to measuring methods and devices used in the field of civil engineering.
  • the invention aims more particularly to measure a residual stress in a shape memory reinforcement.
  • Shape memory materials have the particularity of regaining an initial shape when they are heated and then cooled, the initial shape having been modified by cold deformation.
  • Such materials can be used to produce prestressing reinforcements when, for example, a linear embodiment of this material in strip, strip, ribbon, wire or bar, previously cold drawn while retaining a residual elongation, is fixed by its ends to a structure and that in this locked position it is heated to a temperature activating its memory effect but that the corresponding shortening is prevented by the fixings, a force then appearing and, by equilibrium, inducing an equal and opposite force in the structure, thus achieving its prestressing.
  • This technique produces an effect identical to that obtained by tensioning and locking a conventional prestressing reinforcement and a comparable benefit.
  • the residual stress in the rebar resulting from the prevented shrinkage is not directly known as it cools. It is considered that the value of final stress in the material and therefore said force, is related to the maximum temperature reached.
  • temperature control is the indication of residual voltage.
  • this is an indirect and delayed result, which prejudges performance but does not establish it.
  • part of the shrinkage is not hampered, if for example there is an anchoring play or if the reinforcement presents a yawn when it is fixed before heating.
  • the final force results from a lower constrained shrinkage for the same temperature range, and therefore the performance provided to the structure is insufficient although the target temperature may have been respected.
  • there are devices for measuring tensioned reinforcement, wire, tape, strap known by the term crossbow and which make it possible, by analyzing the stiffness of the transverse deformation of said reinforcement, to determine the force of voltage.
  • the invention aims to meet this need, and it achieves this by proposing a method for measuring the residual tension in a prestressing reinforcement, the reinforcement having its ends anchored in a structure and comprising a free portion not adhering to this structure, the method comprising the steps of:
  • the invention allows the measurement of the tension force in the tensioned reinforcement after activation, and to verify compliance with the objective.
  • the measurement is possible in the same way then at any time of the life of the structure, and thus authorizes its monitoring.
  • the invention performs the direct measurement of the tension in the tensioned reinforcement by analyzing the balance of an additional force introduced and its length between anchors, most often without any other need for shape characteristics or inertia.
  • the prestressing reinforcement is a shape memory reinforcement, made of a material which 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, from preferably between 160 and 300 ° C.
  • the tensile force which is exerted and measured is a transverse force in the middle of the reinforcement, this force being seen by the tensioned reinforcement as a point load causing a bending deformation between the fixing points, of which the deflection, that is to say the displacement of the reinforcement, related to the force, becomes directly an indicator of the tensile force.
  • the invention allows, because the traction device rests on the structure, the deflection of the reinforcement over a relatively large length, in particular equal to the length between its anchors. This makes it possible to reduce the measurement uncertainty and to reduce the influence of the bending stiffness, in particular for reinforcements of lengths less than 50m, thus improving the precision of the measurement.
  • the residual tension is preferably determined by calculating the slope AF / d representative of the variation AF of the tensile force exerted, as a function of the variation Ad of the corresponding displacement observed.
  • the traction is preferably exerted at mid-length of the free portion.
  • This length L ’ preferably corresponds to the length L of the free portion of the reinforcement, that is to say the length of the reinforcement between anchors.
  • the traction device includes any system for exerting a controlled force on the frame, for example a screw jack, hydraulic, pneumatic or electric, preferably a hydraulic or screw jack.
  • the traction device rests on the structure on either side of the frame.
  • the device may include a frame comprising a base resting on the structure.
  • the longitudinal axis of the frame extends in a median plane of the frame of the traction device.
  • the traction is exerted by means of a claw placed under the frame.
  • the claw can be slid under the frame, for example using a mallet.
  • the claw may be integral at one end of a frame, comprising at least one articulated upright, mounted to pivot between a raised position for inserting the claw under the frame and a folded position cooperating with the claw to transmit part of the claw to it. tensile forces exerted on the frame by the traction device. Thus, when the frame is closed, the tensile forces are transmitted to the claw at its two ends located on either side of the frame.
  • the traction device comprises two claws forming a clamp which is closed on the frame when the traction is to be exerted.
  • Such a variant is particularly suitable when the frame has a round cross section.
  • the jack is preferably removably connected to the frame or to the clamp. This can facilitate the assembly of the clamp or the frame without being hampered by the presence of the cylinder.
  • the tensile force is measured using a sensor integrated into the device.
  • a sensor integrated into the device. Any suitable sensor is suitable, the chosen sensor being able in particular to depend on the type of cylinder used and the required precision.
  • the displacement of the frame is measured using a displacement sensor integrated into the device.
  • the displacement of the claw or the gripper is measured relative to a frame supporting the jack and resting on the structure.
  • a further subject of the invention is a method of prestressing a structure, the latter comprising a shape memory prestressing reinforcement, made of a material capable of passing from an initial configuration to a stretched configuration, then resuming the configuration.
  • initial temperature by being brought from room temperature to a sufficient temperature, preferably between 160 and 300 ° C, the method comprising anchoring the ends of the reinforcement in the structure by leaving a free portion not adhering to this structure, the tensioning of the reinforcement by heating that here, then the measurement after cooling of the residual tension in the reinforcement by the implementation of the measurement method according to the invention, as defined above.
  • a further subject of the invention is a method for monitoring the residual tension of a prestressing reinforcement, in particular with shape memory, made of a material capable of changing from an initial configuration to a stretched configuration, then resuming the initial configuration in being brought from ambient temperature to a sufficient temperature, preferably between 160 and 300 ° C, the method comprising the release of a free portion of the reinforcement then the measurement of the residual tension in the reinforcement by setting implementation of the measurement method according to the invention, as defined above.
  • the subject of the invention is also a device for measuring the residual tension in a prestressing reinforcement extending in a structure, in particular for the implementation of the method according to the invention as defined above, this device comprising:
  • a frame comprising a base allowing it to rest on the structure, at least one claw configured to engage with the frame, at least one jack carried by the frame, to move the claw relative to the frame and exert traction on the frame frame,
  • the device may include all or part of the characteristics presented above in relation to the measurement method, and in particular:
  • the claw can be configured to be placed under the frame, especially when the latter is flat,
  • the claw may be integral at one end of a frame, comprising at least one articulated upright, mounted to pivot between a raised position for inserting the claw under the frame and a folded position cooperating with the claw to transmit to it part of the tensile forces exerted on the frame by the traction device,
  • the traction device may include two claws forming a clamp which is closed on the frame when the traction must be exerted, the jack is removably connected to the frame or to the clamp, the device comprises an integrated tensile force sensor, the device comprises an integrated displacement sensor, to measure the displacement of the reinforcement, in particular to measure the displacement of the claw or the clamp relative to a frame supporting the jack and resting on the structure.
  • the base of the frame may be substantially U-shaped. This may have two uprights connected to each other by a central bar.
  • the two uprights can be separated by a wheelbase (measured between the axes of the legs) of between 10 and 50cm, better still between 15 and 35cm, for example of the order of 25cm.
  • the uprights can be fitted with height-adjustable feet, for example feet screwed into the uprights.
  • the uprights can each be substantially perpendicular to the central bar.
  • the device may comprise a frame on which is mounted, in particular in a removable manner, the base of the frame, said frame being able to rest on the frame.
  • the frame may also be able to lean on the structure.
  • Another subject of the invention is a method for monitoring the residual tension of a prestressing reinforcement, in particular a shape memory reinforcement, made of a material which can pass from an initial configuration to a stretched configuration, then resume the configuration. initial by being brought from room temperature to a sufficient temperature, preferably between 160 and 300 ° C, the process comprising the steps of:
  • Figure 1 shows a schematic and partial section of a prestressing reinforcement anchored in a structure
  • FIG 2 is a perspective view, schematic and partial, of the frame of Figure 1 on which is installed a traction device according to the invention
  • Figure 3 shows a schematic and partial section of the reinforcement subjected to a transverse tensile force
  • Figure 4a is an example of a traction device
  • FIG 4b Figure 4b illustrates the traction device of Figure 4a when it is actuated
  • Figure 5a Figure 5a is an example of a variant of the traction device
  • FIG 5b Figure 5b illustrates the traction device of Figure 5a when it is actuated
  • Figure 6a Figure 6a illustrates the location of a force sensor according to the invention
  • FIG 6b Figure 6b illustrates the location of a force sensor according to the invention
  • Figure 6c illustrates the location of a force sensor according to a variant of the invention
  • Figure 6d illustrates the location of a force sensor according to a variant of the invention
  • FIG 7a Figure 7a illustrates the installation of the traction device on a flat frame
  • Figure 7b illustrates the installation of the traction device on the flat frame
  • Figure 7c illustrates the installation of the traction device on the frame
  • Figure 7d illustrates an example of measurement and display of the value of the tension and the corresponding displacement
  • FIG 8a Figure 8a illustrates the installation of a variant of the traction device on the frame
  • FIG 8b Figure 8b illustrates the installation of a variant of the tension device on the frame
  • FIG. 9 is a diagram and graph showing schematically examples of the evolution of the tensile force applied to the free portion of the reinforcement, as a function of the transverse displacement of the reinforcement
  • FIG. 10 is a diagram and graph schematically showing examples of the evolution of the tensile force applied to the free portion of the reinforcement, as a function of the transverse displacement of the reinforcement
  • Figure l ia is a diagram and graph showing schematically examples of the evolution of the tensile force applied to the free portion of the reinforcement, as a function of the transverse displacement of the reinforcement,
  • Figure 11b is a diagram and graph showing schematically examples of the evolution of the tensile force applied to the free portion of the reinforcement, as a function of the transverse displacement of the reinforcement, and
  • Figure 12 is a perspective view, schematic and partial, of the frame on which is installed a traction device according to an alternative embodiment.
  • the prestressing reinforcement is a shape memory reinforcement.
  • the frame 40 is anchored at its ends 45 in a concrete structure 30 34, as illustrated in Figure 1.
  • the frame 40 has a free portion 42 that does not adhere to the structure 30.
  • the measurement of the residual tension T is obtained by analyzing the balance of an additional transverse force introduced on its free portion of length L.
  • This force corresponds to a traction force F exerted on the free portion 42 in a direction perpendicular (or transverse) thereto.
  • the traction is exerted using a traction device 1, as illustrated in FIG. 2.
  • the traction force F is a transverse force applied to the middle of the reinforcement 40. This force is seen by the reinforcement 40 as a point load causing a bending deformation between the anchors 45, as illustrated in Figure 3.
  • the traction device 1 rests on the structure 30 on either side of the frame 40, as illustrated in FIG. 2.
  • the traction device 1 comprises a frame 10 equipped with a base 11 allowing it to rest on the structure 30.
  • the base 11 of the frame 10 may be U-shaped.
  • the latter may include two uprights 19 connected to each other by a central bar 18.
  • the two uprights 19 can be spaced apart by a wheelbase D (measured between the axes of the feet) of between 10 and 50cm, better still between 15 and 35cm, for example of the order of 25cm, as illustrated in FIG. 2.
  • the uprights 19 can be equipped with feet 29 adjustable in height, for example feet screwed into the uprights, as illustrated in Figure 12.
  • the traction device 1 may include a screw jack, as illustrated in Figures 4a and 4b.
  • the screw jack consists of a screw 16 moved by a crank 17.
  • the device 1 comprises a hydraulic cylinder 15 which can be actuated by hydraulic pressure, as illustrated in FIGS. 5a and 5b.
  • the traction F can be exerted by means of a claw 13 placed under the frame 40, and connected to the jack by a rod 14.
  • the claw 13 can be secured to one end of a frame 50, comprising two articulated uprights 55.
  • the uprights can pivot between a raised position for inserting the claw 13 under the frame 40 and a folded position cooperating with the claw 13 to transmit to it part of the tensile forces exerted on the frame by the traction device 1.
  • the tensile force F is transmitted to the claw 13 at its two ends 13a and 13b located on either side and other of the frame 40.
  • the traction device comprises two claws 13 forming a clamp 20 which is closed on the frame when the traction F is exerted.
  • a variant is particularly suitable when the frame is of round cross section, as illustrated in Figures 8a and 8b.
  • the jack 15 is preferably removably connected to the frame 50 or to the clamp 20, as illustrated in FIGS. 7c and 8b.
  • the tensile force F is measured using a sensor 25 integrated into the device 1.
  • a sensor 25 integrated into the device 1. Any suitable sensor is suitable, the sensor 25 chosen being able in particular to depend on the type of jack 15 used and on the desired precision.
  • the sensor 25 can thus be a traction sensor, placed for example on the rod 14 above the claw 13.
  • the sensor can also be a compression sensor, placed for example under the rotation nut of the rod 14, as illustrated in FIG. 6b.
  • the sensor is a bending sensor, for example placed under the reaction support of the rod 14.
  • the senor 15 is based on a calibrated measurement of the pressure in the jack 15, when the latter is a hydraulic jack.
  • the traction exerted by the traction device 1 on the frame causes it to deflect transversely from a "neutral” position shown in Figure 1 to a "loaded” position shown in Figure 3, by a displacement d.
  • the displacement of the reinforcement is measured using a displacement sensor integrated into the device 1.
  • the displacement of the claw 13 or of the clamp 20 is measured using the displacement sensor. relative to the frame 10.
  • the traction device 1 is equipped with a screen 60 allowing the display of the value of the traction force and / or the displacement d of the frame 40, as illustrated in FIG. 7d.
  • the measurement of the displacement of the reinforcement 40 is carried out for a plurality of values of the tensile force L.
  • Figure 9 illustrates the curve C obtained in the case where the frame 40 is flat. This may have an initial portion I extending substantially along a very steep straight line DI, then a curved portion II, and finally a final portion III which extends substantially along a less steep straight line D2, as illustrated on figure 9.
  • the curve C is obtained for a flat reinforcement with a width of about 100mm and a thickness of about 1.5mm.
  • the first part I can correspond to the catching up of the movement of the frame already obtained by interposing the claw 13 between it and the structure 30 because of its thickness. As long as the force deployed by the invention is not greater than that which corresponds to this movement, there is no or very little additional movement. When this force is reached and then exceeded in portion II of curve C, the force becomes directly proportional to the movement as revealed by portion III of curve C.
  • the curve C may have a single straight line D3, as illustrated in Figure 10. This curve C is calculated for a reinforcement of approximately 6mm diameter.
  • the tensile force F deployed by the invention balances the reaction of reinforcement 40. That - this can include two components:
  • a first component, illustrated in FIG. 11a, results from the tension of the reinforcement; the calculation of the force F T is accessible by simple observation of the balance of the forces by considering in particular that the displacement d is small relative to the length F between the anchorages 45 of the reinforcement 40.
  • Fa force F T when the force of traction F is exerted at mid-length, is given by the following formula:
  • a second component F F results from the flexural stiffness of the reinforcement 40, the calculation of which, when the tensile force F is exerted at mid-length (center) is obtained using the formula below:
  • F F 192 * EI * d / F 3 , E and I being the Young's modulus and the bending inertia of the reinforcement, respectively.
  • the residual tension T can then be determined by calculating the slope AF / d representative of the variation AF of the tensile force exerted as a function of the variation Ad of the corresponding displacement observed.
  • the measurement of the residual tension in the prestressing reinforcement can also be carried out at any time during the life of the structure.
  • the traction device 1 may include a frame 70 on which the base 11 of the frame rests as illustrated in FIG. 12. More precisely , the legs of the frame rest on the long sides 75 of the frame.
  • the central bar 18 of the frame 10 is oriented parallel to the short sides 73.
  • the frame 70 has a rectangular shape, and is based on the open portion. By resting on the reinforcement by its short sides 73, the frame 70 determines the length L'of the deflection thereof, which depends on the length of the long sides 75.
  • the measurement of the residual tension T can thus be carried out as described above, by replacing the length L between the anchorages 45 by the deflected length L '.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Force Measurement Appropriate To Specific Purposes (AREA)
  • Bridges Or Land Bridges (AREA)

Abstract

Method for measuring the residual prestress in a reinforcement. Method for measuring the residual tension (T) in a prestressing reinforcement (40), the reinforcement (40) having its ends (45) anchored in a structure (30) and comprising a free portion (42) not adhering to said structure (30), the method comprising the steps of: - measuring the displacement (d) of the reinforcement in response to a tensile force (F) exerted on its free portion (42) in a direction perpendicular thereto, the tensile force (F) being exerted using a tensile device bearing on the structure, - calculating the residual tension in the reinforcement (40) on the basis of said force and the corresponding displacement.

Description

Description Description
Titre : Procédé de mesure de la précontrainte résiduelle dans une armature Title: Method of measuring the residual prestressing in a reinforcement
Domaine technique Technical area
La présente invention concerne les procédés et dispositifs de mesure utilisés dans le domaine du génie civil. L’invention vise plus particulièrement à mesurer une contrainte résiduelle dans une armature à mémoire de forme. The present invention relates to measuring methods and devices used in the field of civil engineering. The invention aims more particularly to measure a residual stress in a shape memory reinforcement.
Technique antérieure Prior art
Dans l’état de l’art, il a été proposé de renforcer une structure en utilisant une armature en alliage à mémoire de forme, ancrée à ses deux extrémités sur la structure. In the state of the art, it has been proposed to reinforce a structure using a shape memory alloy reinforcement, anchored at both ends to the structure.
Les matériaux à mémoire de forme présentent la particularité de retrouver une forme initiale quand ils sont chauffés puis refroidis, la forme initiale ayant été modifiée par une déformation à froid. Shape memory materials have the particularity of regaining an initial shape when they are heated and then cooled, the initial shape having been modified by cold deformation.
De tels matériaux peuvent être utilisés pour réaliser des armatures de précontrainte quand par exemple une réalisation linéaire de ce matériau en bande, lamelle, ruban, fil ou barre, préalablement étirée à froid en conservant un allongement rémanent, est fixée par ses extrémités à une structure et que, dans cette position bloquée elle est chauffée à une température activant son effet mémoire mais que le raccourcissement correspondant est empêché par les fixations, un effort apparaissant alors et, par équilibre, induisant un effort égal et opposé dans la structure, réalisant ainsi sa précontrainte. Such materials can be used to produce prestressing reinforcements when, for example, a linear embodiment of this material in strip, strip, ribbon, wire or bar, previously cold drawn while retaining a residual elongation, is fixed by its ends to a structure and that in this locked position it is heated to a temperature activating its memory effect but that the corresponding shortening is prevented by the fixings, a force then appearing and, by equilibrium, inducing an equal and opposite force in the structure, thus achieving its prestressing.
Cette technique produit un effet identique à celui procuré par une mise en tension et un blocage d’une armature de précontrainte classique et un bénéfice comparable. This technique produces an effect identical to that obtained by tensioning and locking a conventional prestressing reinforcement and a comparable benefit.
Cependant, l’effort résiduel dans l’armature résultant du rétrécissement empêché n’est pas directement connu à l’issu de son refroidissement. On considère que la valeur de contrainte finale dans le matériau et donc ledit effort, est en relation avec la température maximum atteinte. However, the residual stress in the rebar resulting from the prevented shrinkage is not directly known as it cools. It is considered that the value of final stress in the material and therefore said force, is related to the maximum temperature reached.
En général, c’est le contrôle de la température qui constitue l’indication de la tension résiduelle. Il s’agit toutefois d’un résultat indirect et différé, qui préjuge de la performance mais ne l’établit pas. En réalité, il est possible qu’une partie du retrait ne soit pas gêné, si par exemple il existe un jeu d’ancrage ou si l’armature présente un bâillement quand elle est fixée avant chauffage. Dans ce cas, l’effort final résulte d’un retrait gêné plus faible pour une même température portée, et donc la performance apportée à la structure est insuffisante bien que la température cible ait pu être respectée. D’autre part, il existe des dispositifs de mesure d’armature tendue, fil, ruban, sangle, connus sous le terme d’arbalète et qui permettent en analysant la raideur de la déformation transversale de ladite armature, de déterminer l’effort de tension. Ces dispositifs et leur mode de mise en œuvre sont bien connus de l’homme de l’art et font l’objet de nombreuses recommandations et publications, notamment dans le domaine d’activité de la précontrainte du béton. Les Cahiers Interactifs FicheC4-3-Guide_Auscultation_Ouvrage_Art- Cahier_Interactif de l’Ifsttar constituent un exemple d’une telle publication. Les dispositifs de mesure connus sont conçus pour ne dévier qu’une partie définie de l’armature tendue, en s’appuyant sur deux points de celle-ci. Usually, temperature control is the indication of residual voltage. However, this is an indirect and delayed result, which prejudges performance but does not establish it. In reality, it is possible that part of the shrinkage is not hampered, if for example there is an anchoring play or if the reinforcement presents a yawn when it is fixed before heating. In this case, the final force results from a lower constrained shrinkage for the same temperature range, and therefore the performance provided to the structure is insufficient although the target temperature may have been respected. On the other hand, there are devices for measuring tensioned reinforcement, wire, tape, strap, known by the term crossbow and which make it possible, by analyzing the stiffness of the transverse deformation of said reinforcement, to determine the force of voltage. These devices and their mode of implementation are well known to those skilled in the art and are the subject of numerous recommendations and publications, particularly in the field of concrete prestressing activity. The Interactive Notebooks FicheC4-3-Guide_Auscultation_Ouvrage_Art- Cahier_Interactif of Ifsttar constitute an example of such a publication. Known measuring devices are designed to deflect only a defined part of the tensioned reinforcement, by relying on two points thereof.
Il existe un besoin pour pouvoir mesurer la tension résiduelle dans une armature à mémoire de forme, d’une façon qui soit précise et relativement aisée à mettre en œuvre. There is a need to be able to measure the residual tension in a shape memory frame, in a way that is precise and relatively easy to implement.
Résumé de l’invention Summary of the invention
L’invention vise à répondre à ce besoin, et elle y parvient en proposant un procédé pour mesurer la tension résiduelle dans une armature de précontrainte, l’armature ayant ses extrémités ancrées dans une structure et comportant une portion libre non adhérente à cette structure, le procédé comportant les étapes consistant à: The invention aims to meet this need, and it achieves this by proposing a method for measuring the residual tension in a prestressing reinforcement, the reinforcement having its ends anchored in a structure and comprising a free portion not adhering to this structure, the method comprising the steps of:
Mesurer le déplacement de l’armature en réponse à une force de traction exercée sur sa portion libre dans une direction perpendiculaire à celle-ci, la traction étant exercée à l’aide d’un dispositif de traction prenant appui sur la structure, Measure the displacement of the reinforcement in response to a tensile force exerted on its free portion in a direction perpendicular to it, the traction being exerted using a tensile device supported on the structure,
calculer, à partir de la connaissance de cette force et du déplacement correspondant, la tension résiduelle dans l’armature. calculate, from the knowledge of this force and the corresponding displacement, the residual tension in the reinforcement.
L’invention permet la mesure de l’effort de tension dans l’armature tendue après activation, et de vérifier la conformité à l’objectif. La mesure est possible de la même façon ensuite à tout moment de la vie de la structure, et autorise ainsi sa surveillance. The invention allows the measurement of the tension force in the tensioned reinforcement after activation, and to verify compliance with the objective. The measurement is possible in the same way then at any time of the life of the structure, and thus authorizes its monitoring.
L’invention réalise la mesure directe de la tension dans l’armature tendue par analyse de l’équilibre d’un effort supplémentaire introduit et de sa longueur entre ancrages, le plus souvent sans autre besoin de caractéristiques de forme ou d’inertie. The invention performs the direct measurement of the tension in the tensioned reinforcement by analyzing the balance of an additional force introduced and its length between anchors, most often without any other need for shape characteristics or inertia.
De préférence, l’armature de précontrainte est 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. De préférence, la force de de traction qui est exercée et mesurée est un effort transversal au milieu de l’armature, cet effort étant vu par l’armature tendue comme une charge ponctuelle provoquant une déformation de flexion entre les points de fixation, dont la flèche, c’est-à- dire le déplacement de l’armature, rapportée à l’effort, devient directement un indicateur de l’effort en tension. Preferably, the prestressing reinforcement is a shape memory reinforcement, made of a material which 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, from preferably between 160 and 300 ° C. Preferably, the tensile force which is exerted and measured is a transverse force in the middle of the reinforcement, this force being seen by the tensioned reinforcement as a point load causing a bending deformation between the fixing points, of which the deflection, that is to say the displacement of the reinforcement, related to the force, becomes directly an indicator of the tensile force.
L’analyse de la relation entre la force de traction exercée et la déformation de l’armature, connaissant la longueur entre ancrages, suffit en général à calculer l’effort de tension au moment de la mesure, et donc la tension résiduelle. Analysis of the relationship between the tensile force exerted and the deformation of the reinforcement, knowing the length between anchors, is generally sufficient to calculate the tensile force at the time of measurement, and therefore the residual tension.
Contrairement aux dispositifs de l’état de l’art qui ne dévient qu’une faible partie de l’armature, correspondant à l’empattement du dispositif, l’invention permet, du fait que le dispositif de traction repose sur la structure, la déviation de l’armature sur une longueur relativement importante, notamment égale à la longueur entre ses ancrages. Cela permet de diminuer l’incertitude de mesure et de réduire l’influence de la raideur en flexion, notamment pour des armatures de longueurs inférieures à 50m, améliorant ainsi la précision de la mesure. Unlike the devices of the state of the art which deflect only a small part of the frame, corresponding to the wheelbase of the device, the invention allows, because the traction device rests on the structure, the deflection of the reinforcement over a relatively large length, in particular equal to the length between its anchors. This makes it possible to reduce the measurement uncertainty and to reduce the influence of the bending stiffness, in particular for reinforcements of lengths less than 50m, thus improving the precision of the measurement.
La tension résiduelle est de préférence déterminée en calculant la pente AF/ d représentative de la variation AF de l’effort de traction exercé, en fonction de la variation Ad du déplacement correspondant observé. The residual tension is preferably determined by calculating the slope AF / d representative of the variation AF of the tensile force exerted, as a function of the variation Ad of the corresponding displacement observed.
Comme indiqué plus haut, la traction est de préférence exercée à mi-longueur de la portion libre. As indicated above, the traction is preferably exerted at mid-length of the free portion.
La tension résiduelle T est alors donnée par la formule T = (AF/ Ad - a)*b, a et b étant des constantes dépendant de la longueur L’ déviée de l’armature. Cette longueur L’ correspond de préférence à la longueur L de la portion libre de l’armature, c’est-à-dire de la longueur d’armature entre ancrages. The residual voltage T is then given by the formula T = (AF / Ad - a) * b, a and b being constants depending on the length L ’deviated from the reinforcement. This length L ’preferably corresponds to the length L of the free portion of the reinforcement, that is to say the length of the reinforcement between anchors.
Le dispositif de traction comporte tout système permettant d’exercer une force contrôlée sur l’armature, et par exemple un vérin à vis, hydraulique, pneumatique ou électrique, de préférence un vérin hydraulique ou à vis. The traction device includes any system for exerting a controlled force on the frame, for example a screw jack, hydraulic, pneumatic or electric, preferably a hydraulic or screw jack.
De préférence, le dispositif de traction repose sur la structure de part et d’autre de l’armature. A cet effet, le dispositif peut comporter un châssis comportant un piétement reposant sur la structure. Preferably, the traction device rests on the structure on either side of the frame. To this end, the device may include a frame comprising a base resting on the structure.
De préférence, l’axe longitudinal de l’armature s’étend dans un plan médian du châssis du dispositif de traction. Cela confère une stabilité accrue au dispositif, et permet de répartir les efforts exercés par le dispositif sur la structure. Il est possible d’exercer la traction sur l’armature en la soulevant ponctuellement, en la prenant par-dessous et/ou sur les côtés, la surface du dispositif qui vient en appui sur l’armature ayant de préférence une forme adaptée à celle de l’armature, pour minimiser le risque d’endommagement de cette dernière et faciliter la mise en place et l’enlèvement du dispositif. Preferably, the longitudinal axis of the frame extends in a median plane of the frame of the traction device. This confers increased stability on the device, and makes it possible to distribute the forces exerted by the device on the structure. It is possible to exert traction on the frame by lifting it punctually, by taking it from below and / or on the sides, the surface of the device which bears on the frame preferably having a shape adapted to that of the frame, to minimize the risk of damaging the latter and facilitate the installation and removal of the device.
Dans un exemple de mise en œuvre de l’invention, convenant plus particulièrement à une armature plate, la traction est exercée par l’intermédiaire d’une griffe mise en place sous l’armature. L’armature étant plate, la griffe peut être glissée sous l’armature en s’aidant par exemple d’un maillet. In an exemplary implementation of the invention, more particularly suitable for a flat frame, the traction is exerted by means of a claw placed under the frame. As the frame is flat, the claw can be slid under the frame, for example using a mallet.
La griffe peut être solidaire à une extrémité d’un cadre, comportant au moins un montant articulé, monté pivotant entre une position relevée d’insertion de la griffe sous l’armature et une position rabattue coopérant avec la griffe pour lui transmettre une partie des efforts de traction exercés sur le cadre par le dispositif de traction. Ainsi, lorsque le cadre est refermé, les efforts de traction sont transmis à la griffe à ses deux extrémités situées de part et d’autre de l’armature. The claw may be integral at one end of a frame, comprising at least one articulated upright, mounted to pivot between a raised position for inserting the claw under the frame and a folded position cooperating with the claw to transmit part of the claw to it. tensile forces exerted on the frame by the traction device. Thus, when the frame is closed, the tensile forces are transmitted to the claw at its two ends located on either side of the frame.
Dans une variante de mise en œuvre, le dispositif de traction comporte deux griffes formant une pince qui est refermée sur l’armature lorsque la traction doit être exercée. Une telle variante convient en particulier lorsque l’armature est de section transversale ronde. In an alternative embodiment, the traction device comprises two claws forming a clamp which is closed on the frame when the traction is to be exerted. Such a variant is particularly suitable when the frame has a round cross section.
Le vérin est de préférence relié de façon amovible au cadre ou à la pince. Cela peut faciliter le montage de la pince ou du cadre sans être gêné par la présence du vérin. The jack is preferably removably connected to the frame or to the clamp. This can facilitate the assembly of the clamp or the frame without being hampered by the presence of the cylinder.
De préférence, la force de traction est mesurée à l’aide d’un capteur intégré au dispositif. Tout capteur adapté convient, le capteur choisi pouvant notamment dépendre du type de vérin utilisé et de la précision recherchée. Preferably, the tensile force is measured using a sensor integrated into the device. Any suitable sensor is suitable, the chosen sensor being able in particular to depend on the type of cylinder used and the required precision.
De préférence, le déplacement de l’armature est mesuré à l’aide d’un capteur de déplacement intégré au dispositif. Par exemple, on mesure à l’aide du capteur de déplacement le déplacement de la griffe ou de la pince relativement à un châssis supportant le vérin et prenant appui sur la structure. Preferably, the displacement of the frame is measured using a displacement sensor integrated into the device. For example, using the displacement sensor, the displacement of the claw or the gripper is measured relative to a frame supporting the jack and resting on the structure.
L’invention a encore pour objet un procédé de mise en précontrainte d’une structure, cette dernière comportant une armature de précontrainte 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, le procédé comportant l’ancrage des extrémités de l’armature dans la structure en ménageant une portion libre non adhérente à cette structure, la mise en tension de l’armature en chauffant celle-ci, puis la mesure après refroidissement de la tension résiduelle dans l’armature par la mise en œuvre du procédé de mesure selon l’invention, tel que défini ci-dessus. A further subject of the invention is a method of prestressing a structure, the latter comprising a shape memory prestressing reinforcement, made of a material capable of passing from an initial configuration to a stretched configuration, then resuming the configuration. initial temperature by being brought from room temperature to a sufficient temperature, preferably between 160 and 300 ° C, the method comprising anchoring the ends of the reinforcement in the structure by leaving a free portion not adhering to this structure, the tensioning of the reinforcement by heating that here, then the measurement after cooling of the residual tension in the reinforcement by the implementation of the measurement method according to the invention, as defined above.
L’invention a encore pour objet un procédé de surveillance de la tension résiduelle d’une armature de précontrainte, notamment 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, le procédé comportant le dégagement d’une portion libre de l’armature puis la mesure de la tension résiduelle dans l’armature par la mise en œuvre du procédé de mesure selon l’invention, tel que défini ci-dessus. A further subject of the invention is a method for monitoring the residual tension of a prestressing reinforcement, in particular with shape memory, made of a material capable of changing from an initial configuration to a stretched configuration, then resuming the initial configuration in being brought from ambient temperature to a sufficient temperature, preferably between 160 and 300 ° C, the method comprising the release of a free portion of the reinforcement then the measurement of the residual tension in the reinforcement by setting implementation of the measurement method according to the invention, as defined above.
L’invention a encore pour objet un dispositif pour mesurer la tension résiduelle dans une armature de précontrainte s’étendant dans une structure, notamment pour la mise en œuvre du procédé selon l’invention tel que défini ci-dessus, ce dispositif comportant : The subject of the invention is also a device for measuring the residual tension in a prestressing reinforcement extending in a structure, in particular for the implementation of the method according to the invention as defined above, this device comprising:
un châssis comportant un piétement lui permettant de reposer sur la structure, au moins une griffe configurée pour venir en prise avec l’armature, au moins un vérin porté par le châssis, pour déplacer la griffe relativement au châssis et exercer une traction sur l’armature, a frame comprising a base allowing it to rest on the structure, at least one claw configured to engage with the frame, at least one jack carried by the frame, to move the claw relative to the frame and exert traction on the frame frame,
au moins un capteur de mesure de l’effort de traction, et at least one tensile force measurement sensor, and
au moins un capteur de déplacement de la griffe relativement au châssis. at least one movement sensor of the claw relative to the frame.
Le dispositif peut comporter tout ou partie des caractéristiques ci-dessus présentées en relation avec le procédé de mesure, et en particulier : The device may include all or part of the characteristics presented above in relation to the measurement method, and in particular:
la griffe peut être configurée pour être mise en place sous l’armature, notamment lorsque cette dernière est plate, the claw can be configured to be placed under the frame, especially when the latter is flat,
la griffe peut être solidaire à une extrémité d’un cadre, comportant au moins un montant articulé, monté pivotant entre une position relevée d’insertion de la griffe sous l’armature et une position rabattue coopérant avec la griffe pour lui transmettre une partie des efforts de traction exercés sur le cadre par le dispositif de traction, the claw may be integral at one end of a frame, comprising at least one articulated upright, mounted to pivot between a raised position for inserting the claw under the frame and a folded position cooperating with the claw to transmit to it part of the tensile forces exerted on the frame by the traction device,
le dispositif de traction peut comporter deux griffes formant une pince qui est refermée sur l’armature lorsque la traction doit être exercée, le vérin est relié de façon amovible au cadre ou à la pince, le dispositif comporte un capteur de force de traction intégré, le dispositif comporte un capteur de déplacement intégré, pour mesurer le déplacement de l’armature, notamment mesurer le déplacement de la griffe ou de la pince relativement à un châssis supportant le vérin et prenant appui sur la structure. the traction device may include two claws forming a clamp which is closed on the frame when the traction must be exerted, the jack is removably connected to the frame or to the clamp, the device comprises an integrated tensile force sensor, the device comprises an integrated displacement sensor, to measure the displacement of the reinforcement, in particular to measure the displacement of the claw or the clamp relative to a frame supporting the jack and resting on the structure.
Le piétement du châssis peut être sensiblement en forme de U. Celui-ci peut comporter deux montants reliés l’un à l’autre par une barre centrale. The base of the frame may be substantially U-shaped. This may have two uprights connected to each other by a central bar.
Les deux montants peuvent être distants d’un empattement (mesuré entre les axes des pieds) compris entre 10 et 50cm, mieux entre 15 et 35cm, par exemple de l’ordre de 25cm. Les montants peuvent être équipés de pieds réglables en hauteur, par exemple de pieds vissés dans les montants. The two uprights can be separated by a wheelbase (measured between the axes of the legs) of between 10 and 50cm, better still between 15 and 35cm, for example of the order of 25cm. The uprights can be fitted with height-adjustable feet, for example feet screwed into the uprights.
Les montants peuvent chacun être sensiblement perpendiculaires à la barre centrale. The uprights can each be substantially perpendicular to the central bar.
Le dispositif peut comporter un cadre sur lequel est monté, notamment de manière amovible, le piétement du châssis, ledit cadre étant apte à s’appuyer sur l’armature. The device may comprise a frame on which is mounted, in particular in a removable manner, the base of the frame, said frame being able to rest on the frame.
Le cadre peut être également apte à s’appuyer sur la structure. The frame may also be able to lean on the structure.
L’invention a encore pour objet un procédé de surveillance de la tension résiduelle d’une armature de précontrainte, notamment 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, le procédé comportant les étapes consistant à: Another subject of the invention is a method for monitoring the residual tension of a prestressing reinforcement, in particular a shape memory reinforcement, made of a material which can pass from an initial configuration to a stretched configuration, then resume the configuration. initial by being brought from room temperature to a sufficient temperature, preferably between 160 and 300 ° C, the process comprising the steps of:
dégager une portion libre de l’armature, clear a free portion of the frame,
placer le cadre du dispositif selon l’invention sur la portion libre de l’armature, de manière à délimiter une zone de l’armature à dévier, place the frame of the device according to the invention on the free portion of the frame, so as to delimit an area of the frame to be deflected,
mesurer le déplacement de l’armature en réponse à une force de traction exercée sur sa portion libre dans une direction perpendiculaire à celle-ci, la traction étant exercée à l’aide du dispositif, measure the displacement of the reinforcement in response to a tensile force exerted on its free portion in a direction perpendicular to it, the traction being exerted using the device,
calculer à partir de la connaissance de cette force et du déplacement correspondant la tension résiduelle dans l’armature. calculate from the knowledge of this force and the corresponding displacement the residual tension in the reinforcement.
Brève description des dessins 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 : Brief description of the drawings The invention may be better understood on reading the detailed description which follows, of non-limiting examples of implementation thereof, and on examining the appended drawing, in which:
[Fig 1] la figure 1 représente une coupe schématique et partielle d’une armature de précontrainte ancrée dans une structure, [Fig 1] Figure 1 shows a schematic and partial section of a prestressing reinforcement anchored in a structure,
[Fig 2] la figure 2 est une vue en perspective, schématique et partielle, de l’armature de la figure 1 sur laquelle est installé un dispositif de traction selon l’invention, [Fig 2] Figure 2 is a perspective view, schematic and partial, of the frame of Figure 1 on which is installed a traction device according to the invention,
[Fig 3] la figure 3 représente une coupe schématique et partielle de l’armature soumise à une force de traction transversale, [Fig 3] Figure 3 shows a schematic and partial section of the reinforcement subjected to a transverse tensile force,
[Fig 4a] la figure 4a est un exemple de dispositif de traction, [Fig 4a] Figure 4a is an example of a traction device,
[Fig 4b] la figure 4b illustre le dispositif de traction de la figure 4a lorsqu’il est actionné, [Fig 5a] la figure 5a est un exemple de variante de dispositif de traction, [Fig 4b] Figure 4b illustrates the traction device of Figure 4a when it is actuated, [Fig 5a] Figure 5a is an example of a variant of the traction device,
[Fig 5b] la figure 5b illustre le dispositif de traction de la figure 5a lorsqu’il est actionné, [Fig 6a] la figure 6a illustre l’emplacement d’un capteur d’effort selon l’invention, [Fig 5b] Figure 5b illustrates the traction device of Figure 5a when it is actuated, [Fig 6a] Figure 6a illustrates the location of a force sensor according to the invention,
[Fig 6b] la figure 6b illustre l’emplacement d’un capteur d’effort selon l’invention, [Fig 6b] Figure 6b illustrates the location of a force sensor according to the invention,
[Fig 6c] la figure 6c illustre l’emplacement d’un capteur d’effort selon une variante de l’invention, [Fig 6c] Figure 6c illustrates the location of a force sensor according to a variant of the invention,
[Fig 6d] la figure 6d illustre l’emplacement d’un capteur d’effort selon une variante de l’invention, [Fig 6d] Figure 6d illustrates the location of a force sensor according to a variant of the invention,
[Fig 7a] la figure 7a illustre l’installation du dispositif de traction sur une armature plate, [Fig 7b] la figure 7b illustre l’installation du dispositif de traction sur l’armature plate, [Fig 7a] Figure 7a illustrates the installation of the traction device on a flat frame, [Fig 7b] Figure 7b illustrates the installation of the traction device on the flat frame,
[Fig 7c] la figure 7c illustre l’installation du dispositif de traction sur l’armature, [Fig 7c] Figure 7c illustrates the installation of the traction device on the frame,
[Fig 7d] la figure 7d illustre un exemple de mesure et d’affichage de la valeur de la traction et du déplacement correspondant, [Fig 7d] Figure 7d illustrates an example of measurement and display of the value of the tension and the corresponding displacement,
[Fig 8a] la figure 8a illustre l’installation d’une variante du dispositif de traction sur l’armature, [Fig 8a] Figure 8a illustrates the installation of a variant of the traction device on the frame,
[Fig 8b] la figure 8b illustre l’installation d’une variante du dispositif de traction sur l’armature, [Fig 8b] Figure 8b illustrates the installation of a variant of the tension device on the frame,
[Fig 9] figure 9 est un schéma et graphe montrant schématiquement des exemples d'évolution de la force de traction appliquée à la portion libre de l’armature, en fonction du déplacement transversal de l’armature, [Fig 10] figure 10 est un schéma et graphe montrant schématiquement des exemples d'évolution de la force de traction appliquée à la portion libre de l’armature, en fonction du déplacement transversal de l’armature, [Fig 9] FIG. 9 is a diagram and graph showing schematically examples of the evolution of the tensile force applied to the free portion of the reinforcement, as a function of the transverse displacement of the reinforcement, [Fig 10] FIG. 10 is a diagram and graph schematically showing examples of the evolution of the tensile force applied to the free portion of the reinforcement, as a function of the transverse displacement of the reinforcement,
[Fig l ia] figure l ia est un schéma et graphe montrant schématiquement des exemples d'évolution de la force de traction appliquée à la portion libre de l’armature, en fonction du déplacement transversal de l’armature, [Fig l ia] Figure l ia is a diagram and graph showing schematically examples of the evolution of the tensile force applied to the free portion of the reinforcement, as a function of the transverse displacement of the reinforcement,
[Fig 11b] figure 11b est un schéma et graphe montrant schématiquement des exemples d'évolution de la force de traction appliquée à la portion libre de l’armature, en fonction du déplacement transversal de l’armature, et [Fig 11b] Figure 11b is a diagram and graph showing schematically examples of the evolution of the tensile force applied to the free portion of the reinforcement, as a function of the transverse displacement of the reinforcement, and
[Fig 12] la figure 12 est une vue en perspective, schématique et partielle, de l’armature sur laquelle est installé un dispositif de traction selon une variante de réalisation. [Fig 12] Figure 12 is a perspective view, schematic and partial, of the frame on which is installed a traction device according to an alternative embodiment.
Description détaillée detailed description
On va décrire en référence aux figures 1 à 3 un exemple de procédé pour mesurer la tension résiduelle T dans une armature de précontrainte 40. De préférence, l’armature de précontrainte est une armature à mémoire de forme. An example of a method for measuring the residual tension T in a prestressing reinforcement 40 will be described with reference to FIGS. 1 to 3. Preferably, the prestressing reinforcement is a shape memory reinforcement.
L’armature 40 est ancrée à ses extrémités 45 dans une structure 30 en béton 34, comme illustré à la figure 1. Dans l’exemple illustré, l’armature 40 présente une portion libre 42 non adhérente à la structure 30. The frame 40 is anchored at its ends 45 in a concrete structure 30 34, as illustrated in Figure 1. In the example illustrated, the frame 40 has a free portion 42 that does not adhere to the structure 30.
La mesure de la tension résiduelle T est obtenue par analyse de l’équilibre d’un effort transversal supplémentaire introduit sur sa portion libre de longueur L. The measurement of the residual tension T is obtained by analyzing the balance of an additional transverse force introduced on its free portion of length L.
Cet effort correspond à une force de traction F exercée sur la portion libre 42 dans une direction perpendiculaire (ou transversale) à celle-ci. La traction est exercée à l’aide d’un dispositif de traction 1, comme illustré à la figure 2. Dans l’exemple illustré, la force de traction F est un effort transversal appliqué au milieu de l’armature 40. Cet effort est vu par l’armature 40 comme une charge ponctuelle provoquant une déformation de flexion entre les ancrages 45, comme cela est illustré à la figure 3. This force corresponds to a traction force F exerted on the free portion 42 in a direction perpendicular (or transverse) thereto. The traction is exerted using a traction device 1, as illustrated in FIG. 2. In the example illustrated, the traction force F is a transverse force applied to the middle of the reinforcement 40. This force is seen by the reinforcement 40 as a point load causing a bending deformation between the anchors 45, as illustrated in Figure 3.
De préférence, le dispositif de traction 1 repose sur la structure 30 de part et d’autre de l’armature 40, comme illustré à la figure 2. Dans l’exemple illustré, le dispositif de traction 1 comporte un châssis 10 équipé d’un piétement 11 lui permettant de reposer sur la structure 30. Preferably, the traction device 1 rests on the structure 30 on either side of the frame 40, as illustrated in FIG. 2. In the example illustrated, the traction device 1 comprises a frame 10 equipped with a base 11 allowing it to rest on the structure 30.
Le piétement 11 du châssis 10 peut être en forme de U. Celui-ci peut comporter deux montants 19 reliés l’un à l’autre par une barre centrale 18. Les deux montants 19 peuvent être distants d’un empattement D (mesuré entre les axes des pieds) compris entre 10 et 50cm, mieux entre 15 et 35cm, par exemple de l’ordre de 25cm, comme illustré à la figure 2. Les montants 19 peuvent être équipés de pieds 29 réglables en hauteur, par exemple de pieds vissés dans les montants, comme illustré à la figure 12.The base 11 of the frame 10 may be U-shaped. The latter may include two uprights 19 connected to each other by a central bar 18. The two uprights 19 can be spaced apart by a wheelbase D (measured between the axes of the feet) of between 10 and 50cm, better still between 15 and 35cm, for example of the order of 25cm, as illustrated in FIG. 2. The uprights 19 can be equipped with feet 29 adjustable in height, for example feet screwed into the uprights, as illustrated in Figure 12.
Afin d’exercer la force de traction F, le dispositif de traction 1 peut comporter un vérin à vis, comme illustré aux figures 4a et 4b. Dans cet exemple, le vérin à vis est constitué d’une vis 16 mue par une manivelle 17. In order to exert the traction force F, the traction device 1 may include a screw jack, as illustrated in Figures 4a and 4b. In this example, the screw jack consists of a screw 16 moved by a crank 17.
En variante, le dispositif 1 comporte un vérin hydraulique 15 pouvant être actionné par une pression hydraulique, comme illustré aux figures 5a et 5b. As a variant, the device 1 comprises a hydraulic cylinder 15 which can be actuated by hydraulic pressure, as illustrated in FIGS. 5a and 5b.
Dans un mode de réalisation, illustré aux figures 7a à 7d, convenant plus particulièrement à une armature plate 40, la traction F peut être exercée par l’intermédiaire d’une griffe 13 mise en place sous l’armature 40, et reliée au vérin par une tige 14. In one embodiment, illustrated in Figures 7a to 7d, more particularly suitable for a flat frame 40, the traction F can be exerted by means of a claw 13 placed under the frame 40, and connected to the jack by a rod 14.
La griffe 13 peut être solidaire à une extrémité d’un cadre 50, comportant deux montants articulés 55. Les montants peuvent pivoter entre une position relevée d’insertion de la griffe 13 sous l’armature 40 et une position rabattue coopérant avec la griffe 13 pour lui transmettre une partie des efforts de traction exercés sur le cadre par le dispositif de traction 1. Ainsi, lorsque le cadre est refermé, la force de traction F est transmise à la griffe 13 à ses deux extrémités 13a et 13b situées de part et d’autre de l’armature 40. The claw 13 can be secured to one end of a frame 50, comprising two articulated uprights 55. The uprights can pivot between a raised position for inserting the claw 13 under the frame 40 and a folded position cooperating with the claw 13 to transmit to it part of the tensile forces exerted on the frame by the traction device 1. Thus, when the frame is closed, the tensile force F is transmitted to the claw 13 at its two ends 13a and 13b located on either side and other of the frame 40.
Dans une variante de mise en œuvre, le dispositif de traction comporte deux griffes 13 formant une pince 20 qui est refermée sur l’armature lorsque la traction F est exercée. Une telle variante convient en particulier lorsque l’armature est de section transversale ronde, tel qu’illustré aux figures 8a et 8b. In an alternative embodiment, the traction device comprises two claws 13 forming a clamp 20 which is closed on the frame when the traction F is exerted. Such a variant is particularly suitable when the frame is of round cross section, as illustrated in Figures 8a and 8b.
Le vérin 15 est de préférence relié de façon amovible au cadre 50 ou à la pince 20, comme illustré aux figures 7c et 8b. The jack 15 is preferably removably connected to the frame 50 or to the clamp 20, as illustrated in FIGS. 7c and 8b.
De préférence, la force de traction F est mesurée à l’aide d’un capteur 25 intégré au dispositif 1. Tout capteur adapté convient, le capteur 25 choisi pouvant notamment dépendre du type de vérin 15 utilisé et de la précision recherchée. Preferably, the tensile force F is measured using a sensor 25 integrated into the device 1. Any suitable sensor is suitable, the sensor 25 chosen being able in particular to depend on the type of jack 15 used and on the desired precision.
Le capteur 25 peut ainsi être un capteur de traction, placé par exemple sur la tige 14 au- dessus de la griffe 13. The sensor 25 can thus be a traction sensor, placed for example on the rod 14 above the claw 13.
Le capteur peut également être un capteur de compression, placé par exemple sous l’écrou de rotation de la tige 14, comme illustré à la figure 6b. En variante, le capteur est un capteur de flexion, par exemple placé sous l’appui de réaction de la tige 14. The sensor can also be a compression sensor, placed for example under the rotation nut of the rod 14, as illustrated in FIG. 6b. As a variant, the sensor is a bending sensor, for example placed under the reaction support of the rod 14.
Dans une autre variante, le capteur 15 repose sur une mesure étalonnée de la pression dans le vérin 15, quand celui-ci est un vérin hydraulique. In another variant, the sensor 15 is based on a calibrated measurement of the pressure in the jack 15, when the latter is a hydraulic jack.
La traction exercée par le dispositif de traction 1 sur l’armature provoque sa déviation transversale d’une position « neutre » illustrée à la figure 1 à une position « chargée » illustrée à la figure 3, d’un déplacement d. The traction exerted by the traction device 1 on the frame causes it to deflect transversely from a "neutral" position shown in Figure 1 to a "loaded" position shown in Figure 3, by a displacement d.
L'analyse de la relation entre la force de traction L et le déplacement d de l’armature 40, connaissant la longueur L entre ancrages 45, permet de calculer la tension résiduelle T dans l’armature 40. The analysis of the relationship between the tensile force L and the displacement d of the reinforcement 40, knowing the length L between anchors 45, makes it possible to calculate the residual tension T in the reinforcement 40.
De préférence, le déplacement de l’armature est mesuré à l’aide d’un capteur de déplacement intégré au dispositif 1. Par exemple, on mesure à l’aide du capteur de déplacement le déplacement de la griffe 13 ou de la pince 20 relativement au châssis 10. Preferably, the displacement of the reinforcement is measured using a displacement sensor integrated into the device 1. For example, the displacement of the claw 13 or of the clamp 20 is measured using the displacement sensor. relative to the frame 10.
De préférence, le dispositif de traction 1 est équipé d’un écran 60 permettant l’affichage de la valeur de la force de traction et/ou du déplacement d de l’armature 40, comme illustré à la figure 7d. Preferably, the traction device 1 is equipped with a screen 60 allowing the display of the value of the traction force and / or the displacement d of the frame 40, as illustrated in FIG. 7d.
De préférence, la mesure du déplacement de l’armature 40 est réalisée pour une pluralité de valeurs de la force de traction L. Preferably, the measurement of the displacement of the reinforcement 40 is carried out for a plurality of values of the tensile force L.
Ainsi, il est possible de tracer avec plusieurs points de mesure, correspondant à des couples de valeurs (d, L), obtenus de façon ponctuelle ou continue, selon le moyen de collecte des mesures issues des capteurs d’effort et de déplacement, une courbe C associant la force de traction exercée L et le déplacement d correspondant observé. Un exemple d’une courbe C obtenue selon l’invention est donné aux figures 9 et 10. Thus, it is possible to plot with several measurement points, corresponding to pairs of values (d, L), obtained punctually or continuously, depending on the means of collecting the measurements from the force and displacement sensors, a curve C associating the tensile force exerted L and the corresponding displacement d observed. An example of a curve C obtained according to the invention is given in Figures 9 and 10.
La figure 9 illustre la courbe C obtenue dans le cas où l’armature 40 est plate. Celle-ci peut présenter une portion initiale I s'étendant sensiblement selon une droite DI très pentue, puis une portion courbe II, et enfin une portion finale III qui s'étend sensiblement selon une droite D2 moins pentue, tel qu’illustré à la figure 9. Dans cet exemple, la courbe C est obtenue pour une armature plate de largeur d’environ 100mm et d’épaisseur d’environ 1,5mm. Figure 9 illustrates the curve C obtained in the case where the frame 40 is flat. This may have an initial portion I extending substantially along a very steep straight line DI, then a curved portion II, and finally a final portion III which extends substantially along a less steep straight line D2, as illustrated on figure 9. In this example, the curve C is obtained for a flat reinforcement with a width of about 100mm and a thickness of about 1.5mm.
La première partie I peut correspondre au rattrapage du mouvement de l’armature déjà obtenu par interposition de la griffe 13 entre elle et la structure 30 du fait de son épaisseur. Tant que l’effort déployé par l’invention n’est pas supérieur à celui qui correspond à ce mouvement, il n’y a pas ou très peu de mouvement supplémentaire. Lorsque cet effort est atteint puis dépassé dans la portion II de la courbe C, l’effort devient directement proportionnel au mouvement comme le révèle la portion III de la courbe C.The first part I can correspond to the catching up of the movement of the frame already obtained by interposing the claw 13 between it and the structure 30 because of its thickness. As long as the force deployed by the invention is not greater than that which corresponds to this movement, there is no or very little additional movement. When this force is reached and then exceeded in portion II of curve C, the force becomes directly proportional to the movement as revealed by portion III of curve C.
En variante, dans le cas d’une armature ronde, la courbe C peut présenter une seule droite D3, comme illustré à la figure 10. Cette courbe C est calculée pour une armature de diamètre d’environ 6mm As a variant, in the case of a round reinforcement, the curve C may have a single straight line D3, as illustrated in Figure 10. This curve C is calculated for a reinforcement of approximately 6mm diameter.
À tout moment de la portion III de la courbe C de la figure 9 ou de la portion IV de la courbe C de la figure 10, la force de traction F déployée par l’invention, équilibre la réaction de l’armature 40. Celle-ci peut comprendre deux composantes : At any time of portion III of curve C of FIG. 9 or of portion IV of curve C of FIG. 10, the tensile force F deployed by the invention, balances the reaction of reinforcement 40. That - this can include two components:
Une première composante, illustrée à la figure l ia, résulte de la tension de l’armature ; le calcul de la force FT est accessible par simple constat de l’équilibre des efforts en considérant notamment que le déplacement d est faible relativement à la longueur F entre les ancrages 45 de l’armature 40. Fa force FT, lorsque la force de traction F est exercée à mi-longueur, est donnée par la formule suivante : A first component, illustrated in FIG. 11a, results from the tension of the reinforcement; the calculation of the force F T is accessible by simple observation of the balance of the forces by considering in particular that the displacement d is small relative to the length F between the anchorages 45 of the reinforcement 40. Fa force F T , when the force of traction F is exerted at mid-length, is given by the following formula:
FT= 4*T*(d/F) F T = 4 * T * (d / F)
Une deuxième composante FF, illustrée à la figure 1 lb, résulte de la raideur en flexion de l'armature 40 dont le calcul, lorsque la force de traction F est exercée à mi-longueur (centre) est obtenu à l’aide de la formule ci-dessous : A second component F F , illustrated in FIG. 1 lb, results from the flexural stiffness of the reinforcement 40, the calculation of which, when the tensile force F is exerted at mid-length (center) is obtained using the formula below:
FF=192*EI*d/F3, E et I étant le module d’Young et l’inertie en flexion de l’armature, respectivement. F F = 192 * EI * d / F 3 , E and I being the Young's modulus and the bending inertia of the reinforcement, respectively.
Fa tension résiduelle T peut être alors déterminée en calculant la pente AF/ d représentative de la variation AF de l’effort de traction exercé en fonction de la variation Ad du déplacement correspondant observé. The residual tension T can then be determined by calculating the slope AF / d representative of the variation AF of the tensile force exerted as a function of the variation Ad of the corresponding displacement observed.
Celle-ci est alors donnée, quand la force de traction est appliquée au centre de la portion libre de l’armature, par la formule T = (AF/ Ad -192EFF3)*F/4. This is then given, when the tensile force is applied to the center of the free portion of the reinforcement, by the formula T = (AF / Ad -192EFF 3 ) * F / 4.
Fa mesure de la tension résiduelle dans l’armature de précontrainte peut être également effectuée à tout moment de la vie de la structure. The measurement of the residual tension in the prestressing reinforcement can also be carried out at any time during the life of the structure.
Fors de la surveillance de cette tension résiduelle, une portion de l’armature est d’abord dégagée. Fa longueur de cette portion dégagée peut ne pas correspondre à la longueur F entre les ancrages 45. Dans ce cas, le dispositif de traction 1 peut comporter un cadre 70 sur lequel repose le piétement 11 du châssis comme illustré à la figure 12. Plus précisément, les pieds du châssis reposent sur les grands côtés 75 du cadre. Fa barre centrale 18 du châssis 10 est orientée parallèlement aux petits côtés 73. Dans l’exemple illustré, le cadre 70 a une forme rectangulaire, et s’appuie sur la portion dégagée. En s’appuyant sur l’armature par ses petits côtés 73, le cadre 70 détermine la longueur L’de la déviation de celle-ci, qui dépend de la longueur des grands côtés 75. La mesure de la tension résiduelle T peut ainsi être effectuée comme décrit plus haut, en remplaçant la longueur L entre les ancrages 45 par la longueur déviée L’. During the monitoring of this residual voltage, a portion of the reinforcement is first released. The length of this unobstructed portion may not correspond to the length F between the anchors 45. In this case, the traction device 1 may include a frame 70 on which the base 11 of the frame rests as illustrated in FIG. 12. More precisely , the legs of the frame rest on the long sides 75 of the frame. The central bar 18 of the frame 10 is oriented parallel to the short sides 73. In the example illustrated, the frame 70 has a rectangular shape, and is based on the open portion. By resting on the reinforcement by its short sides 73, the frame 70 determines the length L'of the deflection thereof, which depends on the length of the long sides 75. The measurement of the residual tension T can thus be carried out as described above, by replacing the length L between the anchorages 45 by the deflected length L '.
Bien entendu, l’invention n’est pas limitée aux exemples qui viennent d’être décrits. On peut par exemple exercer la traction à l’aide d’autres types de vérins. Of course, the invention is not limited to the examples which have just been described. For example, traction can be exerted by other types of cylinders.

Claims

Revendications Claims
1. Procédé pour mesurer la tension résiduelle (T) dans une armature de précontrainte (40), l’armature (40) ayant ses extrémités (45) ancrées dans une structure (30) et comportant une portion libre (42) non adhérente à cette structure (30), le procédé comportant les étapes consistant à: 1. Method for measuring the residual tension (T) in a prestressing reinforcement (40), the reinforcement (40) having its ends (45) anchored in a structure (30) and comprising a free portion (42) not adhering to this structure (30), the method comprising the steps of:
Mesurer le déplacement (d) de l’armature en réponse à une force de traction (F) exercée sur sa portion libre (42) dans une direction perpendiculaire à celle-ci, la traction (F) étant exercée à l’aide d’un dispositif de traction (1) prenant appui sur la structure, Measure the displacement (d) of the reinforcement in response to a tensile force (F) exerted on its free portion (42) in a direction perpendicular to it, the traction (F) being exerted using a traction device (1) resting on the structure,
calculer à partir de la connaissance de cette force et du déplacement correspondant la tension résiduelle dans l’armature (40). calculate from the knowledge of this force and the corresponding displacement the residual tension in the reinforcement (40).
2. Procédé selon la revendication précédente, la tension résiduelle (T) étant déterminée en calculant la pente AF/ d représentative de la variation AF de l’effort de traction (F) exercé en fonction de la variation Ad du déplacement correspondant de l’armature (40) observé. 2. Method according to the preceding claim, the residual tension (T) being determined by calculating the slope AF / d representative of the variation AF of the tensile force (F) exerted as a function of the variation Ad of the corresponding displacement of the frame (40) observed.
3. Procédé selon la revendication 2, la traction (F) étant exercée à mi-longueur de la portion libre (42), la tension résiduelle (T) étant donnée par la formule T = (AF/ Ad - a)*b, a et b étant des constantes dépendant de la longueur (L’) déviée de l’armature, la longueur (L’) correspondant de préférence à la longueur (L) de la portion libre (42). 3. Method according to claim 2, the traction (F) being exerted at mid-length of the free portion (42), the residual tension (T) being given by the formula T = (AF / Ad - a) * b, a and b being constants depending on the length (L ') deviated from the reinforcement, the length (L') preferably corresponding to the length (L) of the free portion (42).
4. Procédé selon l’une des revendications 1 à 3, l’armature de précontrainte (40) étant 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. 4. Method according to one of claims 1 to 3, the prestressing reinforcement (40) being a shape memory reinforcement, made of a material which 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.
5. Procédé selon l’une des revendications 1 à 4, le dispositif de traction (1) comportant un vérin à vis (16 ; 17), hydraulique, pneumatique ou électrique, de préférence un vérin hydraulique ou à vis. 5. Method according to one of claims 1 to 4, the traction device (1) comprising a screw jack (16; 17), hydraulic, pneumatic or electric, preferably a hydraulic or screw jack.
6. Procédé selon l’une quelconque des revendications précédentes, le dispositif de traction (1) reposant sur la structure (30) de part et d’autre de l’armature (40). 6. Method according to any one of the preceding claims, the traction device (1) resting on the structure (30) on either side of the frame (40).
7. Procédé selon l’une quelconque des revendications précédentes, la traction (F) étant exercée par l’intermédiaire d’une griffe (13) mise en place sous l’armature (40). 7. Method according to any one of the preceding claims, the traction (F) being exerted by means of a claw (13) placed under the frame (40).
8. Procédé selon la revendication précédente, l’armature (40) étant plate et la griffe (13) étant glissée sous l’armature (40). 8. Method according to the preceding claim, the frame (40) being flat and the claw (13) being slid under the frame (40).
9. Procédé selon la revendication précédente, la griffe (13) étant solidaire à une extrémité d’un cadre (50) comportant au moins un montant articulé (55), monté pivotant entre une position relevée d’insertion de la griffe (13) sous l’armature (40) et une position rabattue coopérant avec la griffe (13) pour lui transmettre une partie des efforts de traction (F) exercés sur le cadre (50) par le dispositif de traction (1). 9. Method according to the preceding claim, the claw (13) being integral with one end of a frame (50) comprising at least one articulated upright (55), mounted to pivot between a raised position for inserting the claw (13). under the frame (40) and a folded position cooperating with the claw (13) to transmit to it part of the tensile forces (F) exerted on the frame (50) by the traction device (1).
10. Procédé selon l’une quelconque des revendications 1 à 7, le dispositif de traction (1) comportant deux griffes formant une pince (20) qui est refermée sur l’armature (40) lorsque la traction (F) doit être exercée. 10. A method according to any one of claims 1 to 7, the traction device (1) comprising two claws forming a clamp (20) which is closed on the frame (40) when the traction (F) is to be exerted.
11. Procédé selon la revendication 4 et l’une des revendications 9 et 10, le vérin (15) étant relié de façon amovible au cadre (50) ou à la pince (13). 11. The method of claim 4 and one of claims 9 and 10, the cylinder (15) being removably connected to the frame (50) or to the clamp (13).
12. Procédé selon l’une quelconque des revendications précédentes, la force de traction (F) étant mesurée à l’aide d’un capteur (25) intégré au dispositif (1). 12. Method according to any one of the preceding claims, the tensile force (F) being measured using a sensor (25) integrated into the device (1).
13. Procédé selon l’une quelconque des revendications précédentes, le déplacement de l’armature à mémoire de forme étant mesuré à l’aide d’un capteur de déplacement intégré au dispositif (1). 13. Method according to any one of the preceding claims, the displacement of the shape memory frame being measured using a displacement sensor integrated into the device (1).
14. Procédé de mise en précontrainte d’une structure, cette dernière comportant une armature de précontrainte (40) 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, le procédé comportant l’ancrage des extrémités de l’armature dans la structure en ménageant une portion libre (42) non adhérente à cette structure, la mise en tension de l’armature en chauffant celle-ci, puis la mesure après refroidissement de la tension résiduelle dans l’armature par la mise en œuvre du procédé de mesure telle que défini dans l’une quelconque des revendications précédentes. 14. Method of prestressing a structure, the latter comprising a prestressing reinforcement (40) with shape memory, made of a material which 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, the method comprising anchoring the ends of the reinforcement in the structure by leaving a free portion (42) not adhering to this structure, the tensioning of the armature by heating it, then the measurement after cooling of the residual tension in the armature by implementing the measurement method as defined in any one of the preceding claims.
15. Procédé de surveillance de la tension résiduelle (T) d’une armature de précontrainte (40), notamment 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, le procédé comportant le dégagement d’une portion libre (42) de l’armature (40) puis la mesure de la tension résiduelle (T) dans l’armature (40) par la mise en œuvre du procédé de mesure telle que défini dans l’une quelconque des revendications 1 à 13. 15. Method for monitoring the residual tension (T) of a prestressing reinforcement (40), in particular with shape memory, made of a material which 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, the method comprising the release of a free portion (42) of the reinforcement (40) then the measurement of the residual tension (T ) in the frame (40) by implementing the measurement method as defined in any one of claims 1 to 13.
16. Dispositif (1) pour mesurer la tension résiduelle (T) dans une armature de précontrainte (40) s’étendant dans une structure (30), le dispositif comportant : 16. Device (1) for measuring the residual tension (T) in a prestressing reinforcement (40) extending in a structure (30), the device comprising:
un châssis (10) comportant un piétement (11) lui permettant de reposer sur la structure (30), a frame (10) comprising a base (11) allowing it to rest on the structure (30),
au moins une griffe (13) configurée pour venir en prise avec l’armature (40), au moins un vérin (15) porté par le châssis, pour déplacer la griffe (13) relativement au châssis (10) et exercer une traction (F) sur l’armature (40), au moins un capteur (25) de mesure de l’effort de traction (F), au moins un capteur de déplacement de la griffe (13) relativement au châssis (10), et at least one claw (13) configured to engage with the frame (40), at least one cylinder (15) carried by the frame, to move the claw (13) relative to the frame (10) and exert traction ( F) on the frame (40), at least one sensor (25) for measuring the tensile force (F), at least one displacement sensor of the claw (13) relative to the frame (10), and
- un cadre (70) sur lequel est monté, notamment de manière amovible, le piétement (11) du châssis (10), ledit cadre (70) étant apte à s’appuyer sur l’armature. - A frame (70) on which is mounted, in particular in a removable manner, the base (11) of the frame (10), said frame (70) being able to rest on the frame.
17. Procédé de surveillance de la tension résiduelle (T) d’une armature de précontrainte (40), notamment 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, le procédé comportant les étapes consistant à: 17. Method for monitoring the residual tension (T) of a prestressing reinforcement (40), in particular a shape memory reinforcement, made of a material which can pass from an initial configuration to a stretched configuration, then resume the configuration. initial by being brought from room temperature to a sufficient temperature, preferably between 160 and 300 ° C, the process comprising the steps of:
dégager une portion libre de l’armature (40), release a free portion of the frame (40),
placer le cadre (70) du dispositif selon la revendication 17 sur la portion libre de l’armature (40), de manière à délimiter une zone de l’armature à dévier, mesurer le déplacement (d) de l’armature en réponse à une force de traction (F) exercée sur sa portion libre dans une direction perpendiculaire à celle-ci, la traction (F) étant exercée à l’aide du dispositif (1) selon la revendication 17, et placing the frame (70) of the device according to claim 17 on the free portion of the frame (40), so as to delimit an area of the frame to be deflected, measuring the displacement (d) of the frame in response to a tensile force (F) exerted on its free portion in a direction perpendicular thereto, the traction (F) being exerted using the device (1) according to claim 17, and
calculer à partir de la connaissance de cette force (F) et du déplacement (d) correspondant la tension résiduelle (T) dans l’armature. calculate from the knowledge of this force (F) and the corresponding displacement (d) the residual tension (T) in the reinforcement.
PCT/EP2020/070380 2019-07-19 2020-07-17 Method for measuring the residual prestress in a reinforcement WO2021013765A1 (en)

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FR3098909A1 (en) 2021-01-22
FR3098909B1 (en) 2022-07-22

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