EP3662117A1

EP3662117A1 - Reinforcement anchoring device

Info

Publication number: EP3662117A1
Application number: EP18743048.3A
Authority: EP
Inventors: Julien ERDOGAN; Nicolas DEMEY; Nicolas FABRY
Original assignee: Soletanche Freyssinet SA
Current assignee: Soletanche Freyssinet SA
Priority date: 2017-07-31
Filing date: 2018-07-27
Publication date: 2020-06-10
Also published as: CA3071589A1; FR3069558A1; WO2019025330A1; US20200157818A1

Abstract

The invention relates to a device (10) for anchoring pre-stressing reinforcement(s) (3) or a structural cable such as a guy, for a structure, in particular made of concrete (1), comprising: - an anchoring block (20) having at least one recess (22) configured to receive a clamping jaw (21) for clamping a reinforcement (3), - an anchoring sub-block (30), having a bearing face (32) on which the anchoring block (20) rests and an arched shape, the concave portion of which is oriented towards the structure.

Description

ARMATURE ANCHORING DEVICE

The present invention relates to devices for anchoring prestressing tendons or structural cable such as a stay.

The anchoring devices are intended to allow the locking of the prestressing reinforcement of a concrete structure, this blocking occurring at the end of the reinforcement by which the tensioning is carried out.

The first patent FR 926 505 on an anchoring device was filed by Eugène Freyssinet in 1939 for the realization of an anchor having no projection outside the work to put in compression.

According to this patent, cement reinforced silica sand or asbestos is introduced in the fluid state between two metal shells in which extend the reinforcements to retain and put into compression using a cone mortar pushed by a jack. The outermost metal shell is received in a concrete element with a conical shaped housing surrounded by metal reinforcements.

This type of anchorage has ceased to be used because of the increase in the stress recovery capacity of the prestressing strands, and the market has evolved towards metal anchors of different design.

Current anchoring devices thus conventionally comprise an anchor block, also called an anchor head, and a support element on which the anchor block provides the transfer of the prestressing force in the concrete.

The support element is called tromplaque, when its shape allows it to exert not only the transfer of the prestressing force but also the expansion of the reinforcements connected to the anchor block between the latter and a passage conduit reinforcements within the book.

The anchor block is conventionally made of steel or cast iron so as to be sufficiently strong to withstand concentrated anchoring efforts.

The same is true of the support element.

The frames are engaged in jaws which ensure their jamming in the anchor block.

The concrete of the structure can be reinforced by passive reinforcement called bursting and surface that allow it to withstand the local effort applied by the anchoring device during the tensioning of the reinforcements, and during the life of the structure.

The brochure PRECONTRAINTE FREYSSINET (09/2014 edition CIII 1) describes various anchoring devices commonly used to date.

With the development of high performance concrete, anchors using both metal and cementitious components have been proposed.

Patent EP 0 563 006 B1 thus describes an anchoring device comprising an anchoring block resting on a metal support element having an annular-shaped cavity engaged on a hollow block of annular shape also, made of cementitious material of mechanical strength. greater than that of the concrete of the structure. This block has a peripheral surface of generally conical shape and a face facing the work of generally convex shape towards the work. The block is arranged around a conduit in which the frames pass to put in tension.

Patent EP 0 568 667 B1 discloses an anchoring device comprising an anchor block consisting of a mortar receiving the anchoring jaws. This anchor block is based on a support element housed in a concrete reservation, which is reinforced by reinforcements. The mortar anchor block can be reinforced at its periphery by a metal hoop. The support member may be made with a mortar element disposed within a metal hoop. In such a device, the cementitious material of the anchor block is biased in bending in its lower part. However, the presence of traction zones in a cementitious material is problematic. This device, like the previous one, did not know to the knowledge of the plaintiff of important commercial development.

EP 2 365154 A1 discloses an anchoring device comprising a metal anchor block configured to receive reinforcements. The anchor block rests on a bearing element that can be made with a high strength concrete element disposed within a metal or plastic retaining ring. The anchor block and the support member each have a contact surface of different curvatures to allow pivoting of the anchor block. This device requires the use of a retaining ring.

There is a need to further improve the anchoring devices in particular to overcome the use of complex and expensive metal parts, or to reduce their number, and to offer new possibilities for anchoring the prestressing tendons or structural cable such as a stay.

The invention aims to meet this need and it achieves this through an anchoring device of prestressing frame (s) or structural cable such as a structure stay, especially of concrete, comprising:

- An anchor block having at least one housing configured to accommodate a clamping jaw, also called "anchor jaws", a prestressing frame or structural cable of the structure,

- An anchoring sub-block preferably comprising a cementitious material, having a bearing surface on which rests the anchor block and a vault shape whose concavity is oriented towards the work. This concavity can be centered on the axis according to which the tension of the reinforcement or frames is exerted.

The arch form of the anchoring sub-block makes it possible to avoid the presence of zones in tension that are detrimental to the strength of the material. Its shape can easily be obtained by molding, machining or extruding the cementitious material, in particular of the 3D printing type.

The invention makes it possible to reduce the cost price of the anchor by dispensing with the use of conventional metallic support elements, the high-performance concretes having a lower cost than the metals used to produce them. In addition, this makes it possible to avoid or limit the problems related to the corrosion of metals, and to control the manufacture of the anchoring device, because this can take place, if desired, in a workshop near the construction site.

The invention can also make it possible to give the sub-block the desired shape to withstand the induced forces, without using bursting frames such as metal and surface frets, or reducing their number.

The cementitious material of the anchoring sub-block is preferably BHP or

UHPFRC. A high performance BHP concrete results in a compressive strength greater than or equal to 50 MPa, which is higher than that of a conventional concrete with a strength of around 30 to 35 MPa. Ultra-high performance fiber reinforced concrete BFUHP results in a compressive strength greater than or equal to 110 MPa, or even 150 or 250 MPa. According to the invention, the compressive strength in question is that defined by the NF EN 206-1 standard, and corresponds to the 28-day resistance measured on a cylindrical specimen. For the purposes of the invention, the fibers contained in the BFUHP are not considered as reinforcements, this term being reserved for macroscopic elements not dispersed randomly in the cementitious material but occupying a predefined position.

The anchoring device may comprise a force distribution element in the structure, comprising a cementitious material, on which the anchoring sub-block rests, the distribution element and the sub-anchor block having surfaces. in mutual support of sufficient extent for transmitting the forces of the sub-anchor block to the distribution element. Alternatively, if the strength of the cementitious material of the structure allows, the distribution element is replaced by a corresponding complementary shape made within the structure. In this case, the anchor sub-block comes directly into contact with this complementary form made in the book.

The cementitious material of the sub-block can be directly in contact with the cementitious material of the distribution element. The surfaces in contact may be of generally complementary forms, or even exactly complementary. One way among others, which is however advantageous in its simplicity, to ensure a good complementarity of shapes, is to mold one of the sub-block and the distribution element in contact with the other of the sub-unit. block and distribution element.

It is also possible to produce at least one of the sub-block and the distribution element with small, relatively fragile, so-called "fuse" reliefs, which will collapse under the effect of the compression of the sub-block. block on the distribution element, and in crushing will allow more intimate contact between the sub-block and the distribution element. Such reliefs are for example made in the form of thin ribs, for example corrugations or radial striations.

It is also possible to interpose between the sub-block and the distribution element at least one non-cementing material which will collapse under the effect of the compression of the sub-block on the distribution element; it is for example at least a thickness of a metal material, preferably ductile, such as a lead strip for example, or a sheet of a polymeric material.

Where appropriate, the non-cementitious material or materials present at the interface between the cementitious material of the sub-block and that of the distribution element correspond to the envelope of one or more lost molds used to mold the sub-block. block and / or the distribution element. The surfaces of the sub-block and the distribution element intended to bear on one another can be given a shape which makes it possible to ensure that, despite the manufacturing tolerances, the distribution of the stresses remains favorable. the good mechanical strength of the sub-block and the distribution element. For example, the nominal angle given to the surface of the sub-block intended to bear on the distribution element can be chosen such that by integrating the manufacturing tolerances one always has a first contact which takes place at the placing of the parts, in the zone which is furthest from the concave face of the sub-block.

The opening angle of the concavity of the sub-block, defined by the half-angle (a) at the top of the cone which rests on the (inner) edge of the concave face farthest from the anchor block and which is perpendicular at this edge to the concave face, is preferably between 15 and 90 °, better between 30 and 90 °

Preferably, the interface between the sub-block and the distribution element is made so that the sub-block can slide into the distribution element under the effect of the compression and become more jammed in it. . Thus, the compression related to the tension of the reinforcement or reinforcement is accompanied by an increased tightening of the sub-block by the distribution element, which tends to maintain the sub-block in compression and to maintain the possible subject areas to tensile stresses within the limit of the maximum tensile stresses allowed by the material.

It is possible to have at the interface between the cementitious material of the sub-block and that of the distribution element at least one intermediate element intended to facilitate this sliding, preferably of coefficient of friction less than or equal to 0.5.

The interface between the sub-block and the distribution element is preferably inclined relative to the normal to the concave face, the angle (b) formed between the interface and the tangent to the concave face at the the interface being acute, preferably between 15 and 90 ° upper bound excluded, better between 15 and 50 °, in particular of the order of 30 °.

The face of the sub-block intended to bear against the distribution element can thus be part of a cone whose half-angle (a ') at the top is strictly less than 90 °. In the presence of an intermediate element made of a non-cementitious material between the sub-block and the distribution element, it is preferably that the sliding occurs in a cone whose orientation is as given above.

In exemplary embodiments, the sub-block is made with a cementitious material surface intended to bear on the distribution element or the structure itself if the strength of the cementitious material of the latter allows it, which is conical acute angle with the tangent to the concave face at its end located at said support face. Such a conical shape provides compression of the sub-block material and can avoid to provide around the sub-block a metal containment ring.

It is also possible to arrange between the sub-block and the distribution element a spacer element made of a material other than cementitious, in particular metal, which has a wedge shape, in which case the bearing faces of the sub-block and the element of distribution may have different angles, the difference preferably corresponds to the angle at the top of the corner wedge element.

The distribution element advantageously has a compressive strength greater than that of the concrete of the structure, better intermediate between that of the material of the anchoring sub-block and that of the concrete of the structure, preferably being BHP. The distribution element preferably has a shape widening towards the structure, preferably being traversed by an opening for the passage of the prestressing tendons, widening towards the anchoring sub-block. The distribution element may be without reinforcing reinforcement, such as for example a bursting frame.

The anchor block may have a plurality of conical shaped receiving receptacles for reinforcing jaws.

The anchoring block may be of cementitious material, preferably BFUHP, preferably comprising conical metal inserts for receiving the clamping jaws, and preferably also comprising a bursting frame.

The bearing face of the anchoring sub-block on which the anchoring block rests may be concave towards the anchoring block, in particular when the latter is made of cementitious material, and the anchor block has in this case advantageously a convex lower bearing surface of complementary shape. One may have been counter-molded on the other, as has been detailed above concerning the support of the sub-block on the distribution element. A spacer element made of a non-cementitious material, such as a thickness of metal or plastic, can also be used at the interface between the anchor block and the sub-block.

Alternatively, the anchor block is metallic. In this case, the aforementioned abutment face may be flat.

The anchoring sub-block is preferably made without reinforcement.

The invention also relates to a structure, in particular made of concrete, comprising at least one prestressing frame or anchored structure cable (or "held in tension") with the aid of an anchoring device according to the invention as defined above.

The structure may comprise a concrete structure in which the above-mentioned distribution element is advantageously embedded. The concrete of the structure may have a compressive strength of less than or equal to 40 MPa, in particular of the order of 30 to 35 MPa, or even less, for example less than or equal to 35 MPa, for example of the order of 20. at 25 MPa.

This concrete structure may comprise a conduit opening through a flared portion on the distribution element.

Another subject of the invention is, according to another of its aspects, a method of anchoring at least one prestressing reinforcement or structural cable of a structure, in particular made of concrete, comprising the anchoring of the reinforcement within an anchor block of an anchoring device according to the invention, as defined above.

This method may include tensioning the reinforcement (s) with a jack resting on the anchor block or the sub-block.

Another subject of the invention is, according to another of its aspects, a method of manufacturing a device for anchoring prestressing reinforcement (s) or structural structure cable, in particular made of concrete, in particular of a device as defined above, this device comprising:

- An anchor block having at least one housing configured to receive a clamping jaw of a prestressing frame of the structure,

an anchoring sub-block comprising a cementitious material, having a bearing surface on which the anchoring block rests and preferably an arch form whose concavity is oriented towards the structure,

method in which the sub-block anchor is made by means of a molding equipment or extrusion of cementitious material. The anchorage sub-block can be realized in an on-site workshop.

The anchoring sub-block can be arranged at least partially in a reservation of the work.

The anchoring device according to the invention can be put in place in place of an anchoring boss.

One of the anchoring sub-block and the aforesaid distribution element can be molded in contact with the other, so as to obtain bearing surfaces of complementary shapes.

If necessary, the anchoring sub-block can be made in a lost mold, this mold being for example made of thermoplastic material. It is also possible to make the distribution element in a lost mold.

The anchor block, when made at least partially of a cementitious material, can also be made in a lost mold. It can still be counter-molded on the sub-block, or vice versa.

The invention also relates, independently or in combination with the foregoing, to an anchoring system for prestressing tendons or structural cables, in particular for an anchoring device as defined above, comprising gripping jaws. tightening (also called "anchor jaws") reinforcements and an anchor block made of BFUHP, having conical shaped housing for receiving the jaws and ensure the binding of the reinforcements under the effect of the tension in them , the anchor block having a face by which the forces are transmitted to the structure, of convex shape towards the structure.

Such a system may have all or some of the features set out above. In particular, the jaw receiving housings may comprise metal inserts, in particular having at least one portion of conical shape. The anchor block can have as many passages for the frames as there are reinforcements. The system may comprise a bursting armature on the periphery of the anchor block, on the opposite side to the face that transmits the forces. The anchoring block may have an outer surface widening towards the face which transmits the forces to the structure of the structure, in particular of frustoconical shape.

The invention also relates, independently or in combination with the foregoing, to an anchoring sub-block, in particular for an anchoring device as defined above, made in BHP or BFUHP, comprising a bearing surface for receiving an anchor block of prestressing tendons or structural cable, including an anchor block of a system as defined above , passages for said armatures, a peripheral force transmission portion and a central portion defining, on the opposite side to the bearing face, a concavity. The peripheral portion may have an end face connecting substantially perpendicular to the concave surface of the central portion, better forming an acute angle with the tangent to said concave surface at its outer edge. The sub-block may be of external shape of revolution about the axis in which the tension in the reinforcements is applied. The abovementioned abutment face may be of concave shape, in particular complementary to that of the anchor block. In a variant, said support face is flat. The sub-block may consist exclusively of BFUHP, without integrated reinforcement. The surface of the central portion of concave shape may be spherical, and better non-constant curvature, decreasing away from the top, being for example parabolic.

The sub-block may comprise a casing made of a non-cementing material constituting a lost mold. The sub-block may comprise on at least one of its faces intended to be compressed, for example the support face for the anchor block or that intended to rest on the distribution element, reliefs intended for s crush under effort, for example a set of thin ribs and low height.

The sub-block may comprise sheaths through which the reinforcements pass through the cementitious material. These sheaths can protrude into the concavity of the sub-anchor block, which can facilitate their cutting by allowing a straight cut. These sheaths can be closed during the molding of the anchoring sub-block.

The subject of the invention is, independently or in combination with the foregoing, a distribution element, in particular for an anchoring device as defined above, comprising a BHP body traversed by a central opening for the passage of prestressing tendons or structural cable, having a receiving surface of an anchoring sub-block and an outer peripheral surface which widens away from the surface, in particular of frustoconical shape.

The central opening may have a section that increases closer to the sub-anchor block. The distribution element may have a face to the opposite of the anchoring sub-block which is flat and perpendicular to the axis of the central opening.

The distribution element is preferably made with a conduit for injecting a cement slurry or a grease or wax.

The distribution element can be made with a lost mold.

The invention also relates, independently or in combination with the foregoing, to an anchoring device for a concrete structure, comprising an anchor block serving to anchor prestressing reinforcements, an anchoring sub-block on which the anchor block and a distribution element are at least partially embedded in the concrete structure of the structure, the anchoring sub-block and the distribution element being made at least partially of cementitious resistance materials at the compression greater than that of the concrete of the structure, the compressive strength of the anchoring sub-block being greater than that of the distribution element. Such an arrangement makes it possible to distribute the forces in the structure without exceeding the mechanical strength of each component, the distribution element being able to be made with a larger size than that of the sub-block, in a less expensive material. We can give each component the shape that allows it to work mainly in compression.

The anchoring sub-block is preferably made of BFUHP. The distribution element may be made of a material of lesser mechanical strength than BFUHP, in particular be made of BHP.

The anchor block may be made of a cementitious material, in particular

UHPFRC.

Such a device may comprise a system as defined above, an anchor sub-block as defined above, and / or a distribution element as defined above. At least one intermediate element which is not made of cementitious material, in particular in the form of a metal strip or of a thickness of plastic material, can be interposed between the anchor block and the sub-block, or between the latter and the distribution element.

The mold or molds used to make the anchor block, the sub-block and / or the distribution element can be made by 3D printing. The invention will be better understood on reading the detailed description which follows, examples of non-limiting implementation thereof, and on examining the appended drawing, in which:

FIG. 1 schematically and partially shows a concrete structure provided with an anchoring device according to the invention,

FIG. 2 represents in axial section a variant of anchoring device according to the invention,

FIG. 3 shows an alternative embodiment of a sub-block, with the anchor block represented on it,

FIG. 4 is a view similar to FIG. 2 of an alternative embodiment of the anchoring device,

FIG. 5 illustrates an example of relief that can be made on the face of the sub-anchor block intended to bear on the distribution element,

FIG. 6 illustrates the use of an intermediate element at the interface between the anchorage sub-block and the distribution element,

FIG. 7 is an example of a lost mold that can be used for molding the sub-anchor block and,

- Figure 8 illustrates the possibility of replacing the distribution element by a corresponding form made directly on the structure.

FIG. 1 shows partially a structure comprising a concrete structure 1 within which is integrated at least one anchoring device 10 according to the invention.

This anchoring device 10 serves to maintain in tension ("anchor") reinforcements 3 constituting cables, for example cables formed of a bundle of substantially parallel strands, of all steel grades, galvanized, greased and / or individually sheathed. Each strand of the cable may itself consist of multiple wires. The cable formed by the reinforcements 3 connected to the same anchoring device may consist for example of 1 to 61 strands, better 2 or 3 to 61, each strand being for example of the T15.7 type. The number of reinforcement can still be higher for a stay, for example up to 200. The reinforcements 3 are not limited to cable strands, and may be threads or threaded bars, in which case they are energized by tightening a nut engaged on the thread of the bar.

The frames 3 may be adherent or not to the structure 1, depending on whether the prestressing is adherent or not.

The armatures 3 pass through the structure 1 in favor of a conduit 8, which may be internally covered with a sheath 58, for example a thermoplastic material or corrugated metal strip (annealed). The reinforcements 3 may be embedded in the duct in a grease, in the case of a non-adherent preload, or in a cementitious grout setting in the case of an adhesive prestressing.

The book 1 preferably has, as illustrated, a reservation 2 to accommodate a sealing or a not shown cowling, protection of the anchoring device 10, after installation and tensioning of the frames 3.

The concrete of structure 1 has a conventional compressive strength, typically of the order of 30 to 35 MPa, for example between 20 MPa and 45 MPa.

The anchoring device 10 comprises in the illustrated example an anchor block 20, a sub-block 30 and a distribution element 40, also called "tromplaque" by analogy with the existing distribution elements.

The anchor block 20 serves to retain the ends 3a of the frames 3, by means of jaws 21 of conical shape, each formed of keys and a retaining ring 59, in a conventional manner.

The jaws 21 are received in metal inserts 22, themselves arranged in housings 29 of complementary shape of the anchor block 20. The inserts 22 have a conical shape where the jaws 21 are received, so that a traction on the armature 3 engaged in the jaw 21 is accompanied by a radial clamping and an indentation of the jaw 21 on the frame, the stronger the traction is intense.

In the example shown, only three armatures 3 are apparent, the invention not being limited to a number of particular prestressing reinforcements, nor to a particular arrangement of these armatures with respect to the X axis of the device. anchorage 10. The anchoring block 20 is made in the example of Figure 1 in BFUHP, with a bursting frame 23 in the upper part, at its periphery, in the form of a metal hoop.

The anchoring block 20 has a base 25 widening towards an inner face 24 convex towards the structure 1. The base 25 is for example a frustoconical outer peripheral surface, with or without a revolution around the X axis, preferably with axial symmetry. The frames 3 may be arranged in a hexagonal configuration around a central frame (or a central triplet), for example.

The lower face 24 has for example a spherical cap shape. The sub-block 30 is made of BFUHP also, in the example illustrated.

It has a body traversed by as many holes 31 as reinforcements 3. These holes are each coated with a sheath 57 in the example shown.

The sub-block 30 has a bearing surface 32 of concave shape, complementary to the convex face 24 of the anchoring block 20, for example in the form of a spherical cavity of revolution about the axis X.

The sub-block 30 has a generally vault shape, and is supported by a peripheral portion 33 on the distribution element 40.

The arched face 34 of the sub-block 30, internal to the peripheral portion 33, has a concave shape towards the distribution element 40 and defines under the central part of the sub-block 30 a cavity 38, into which the holes 31 of passage of reinforcement 3.

The distribution element 40 is hollow and has a central opening 41 flaring towards the sub-block 30, which is traversed by the cables 3. In the example, the opening 41 is frustoconical.

The arched face 34 is for example, as illustrated, spherical of revolution of axis X, but may advantageously be otherwise concave, as will be described later.

The peripheral portion 33 bears on a surface 49 of the distribution element 40 by an annular bearing surface 36 which converges towards the structure 1 and which is for example frustoconical, as illustrated. The bearing surface 36 is for example oriented substantially perpendicular to the arched face 34, as illustrated. The concavity 38 may be aperture given by the half-angle at the apex of the cone passing through the outer edge of the concavity 38 and perpendicular to the concave surface 34 at this edge, between 15 and 90 °, and preferably between 30 and 90 °.

The surface 49 of the distribution element has the same orientation as the surface 36 of the sub-block, being of complementary shape, being at least as wide as the surface 36.

The edge 53 of the opening 41 can be located, as illustrated, substantially at the junction between the arched face 34 and the bearing surface 36.

The distribution element 40 has a shape that widens, ie by expanding, within the structure 1, with for example an outer surface 46 of frustoconical shape, in the extension of the sub-block 30 to the inside the structure 1.

The distribution element 40 may be made of a material of compressive strength intermediate between that of the concrete of the structure 1 and that of the sub-block 30, preferably high-strength concrete BHP. Thus, between the anchoring block 20 and the concrete of the structure 1, there are a plurality of force transmission elements whose resistance is degressive from the reinforcements 3 to the element 40 in contact with the concrete of the structure, and the size (especially the largest dimension) may be increasing, as shown.

The distribution element 40 may have an end face 47 perpendicular to the axis X, as illustrated in FIG. 1, that is to say perpendicular to the direction in which the stress is exerted in the structure 1 .

To implement the device of FIG. 1, the distribution element 40 is positioned in the extension of the conduit 8, then the concrete of the structure 1 is poured. The opening 41 of the distribution element 40 can be connected to a sheath 52 covering the conduit 8 by a transition element (not shown) of generally conical shape, also called "trumpet", which may be a simple flared tube. After pouring, setting and stripping of the concrete of the structure 1, the reinforcement 3 is threaded into the pipe 8 and through the distribution element 40.

The sub-block 30 and the anchoring block 20 are then put in place with the jaws 21. A jack, preferably hydraulic, is then used to tension the reinforcements 3 which are anchored in tension in the anchor block 20 by wedging the jaws 21 on each armature 3.

The BFUHP sub-block 30 and the BHP distribution element 40 may be cast or extruded on site, that is, in a workshop located near the construction site (typically less than 50 km). It is the same if appropriate anchor block 20 when it is made of BFUHP. The various metal inserts can be placed in a suitable formwork, then pour or extrude the concrete and put in an oven.

In order to obtain a good complementarity of shape of the bearing surfaces 36 of the sub-block 30 and 49 of the distribution element 40, one can be molded in contact with the other.

The dimensions of the anchoring block 20, the sub-block 30 and the distribution element 40 can be parameterized as a function of the strength and the geometry of the structure 1 to which the anchoring device 10 is intended, for a given effort of prestressing to diffuse in this one.

In particular when the size of the distribution element 40 is sufficient, it may not be necessary to integrate in the structure 1 passive frames, in particular diffusion and hooping, near the anchoring device 10, in particular under the and around the distribution element 40.

However, it is possible to integrate in the structure 1 around the duct 8 a helical reinforcement 51, as illustrated, to take account of the fact that the reinforcements 3 can be constrained radially by the duct 8.

The shapes given to the anchoring block 20, to the sub-block 30 and to the distribution element 40 make it possible to stress the cementitious material which constitutes them mainly in compression under the effect of the tension force prevailing in the reinforcement elements. In particular, the tensile stresses in the cementitious material of these elements preferably never exceed 1/20 of the compressive strength of the cementitious material concerned.

The sub-block 30 transmits, by its internal vault shape, the force received from the anchor block 20 via internal stresses, mainly compression. The distribution element 40 and the structure 1 may be molded with a conduit 60 for the passage of a pipe for injecting a grease or a grout into the conduit 8.

In the example of Figure 1, the anchor block 20 is BFUHP. In the variants of Figures 2 to 4, the anchor block 20 is metallic, being for example steel, and its face 24 bearing on the sub-anchor block 30 is flat and perpendicular to the axis X.

In this case, the anchoring sub-block 30 also has a flat bearing surface 32 perpendicular to the axis X.

FIG. 2 illustrates the possibility for the concave face 34 to be non-spherical, in this parabolic case. The concavity 38 is thus deeper, which makes it possible to accentuate the vault operation, thus preventing the appearance of tensile stresses in the sub-block 30.

The angle α 'defined as the half-angle at the apex of the cone in which the face 36 is inscribed is less open than the angle α of the example of FIG.

The face 36 of the peripheral portion 33 makes an acute angle b with the tangent to the concave surface 34 taken at the outer edge of the concavity 38. This angle b is for example of the order of 30 °, being preferably included between 15 and 90 ° upper limit excluded, better between 20 and 60 °.

FIG. 3 illustrates the possibility for the sheaths 57 to project beyond the concavity 38. It is indeed not necessary to cut them to the exact profile of the concavity, since these sheaths 57 are closed during the casting the cementitious material of the sub-block 30.

The variant of Figure 4 differs from that of Figure 2 in that the distribution element 40 is shallower, and the shape of the concavity 38.

In this case, the structure 1 may comprise surface and / or burst reinforcements, under the distribution element 40.

It is desirable that the sub-block 30 bears on the distribution element 40 relatively homogeneously over the entire width of the surface 36.

However, manufacturing tolerances can lead to irregularity or inclination defects that hinder a uniform transmission of forces. To avoid disparities in the shape of the surfaces 36 and 49, the sub-block 30 can be counter-molded on the distribution element 40, or vice versa. Likewise, the anchoring block 20 can be counter-molded on the sub-block 30 or vice versa.

In the absence of counter-molding, can be made on the sub-block 30 and / or the distribution element 40 streaks 65 as shown in Figure 5. These grooves 65 have fragile edges that break under the pressure exerted and crushing where the stresses are locally the strongest tend to level the stress level over the entire surface and compensate for manufacturing tolerances. It is a form of matting of one or both surfaces vis-à-vis.

It is still possible, as illustrated in FIG. 6, to insert between the sub-block 30 and the distribution element 40 at least one intermediate element 70.

This intermediate element 70 can be crushed under the bearing pressure of the sub-block 30 on the distribution element 40 and thus absorb by local deformation the strongest stresses by redistribution effect.

The spacer element 70 may be a strip of a ductile metal, for example lead, or a sheet of a polymeric material.

The intermediate element 70 may also promote the sliding of the sub-block 30 relative to the distribution element 40 when an acute cornering angle b exists.

FIG. 7 illustrates the possibility of making the sub-block 30 with a lost mold 80. The latter may have an opening 81 on the side for its filling. In this case, the wall of the mold 80 is an element that interposes between the cementitious material surface of the sub-block and that of the distribution element 40 and which can play the role of the aforementioned spacer element.

The distribution element 40 can also be made with a lost mold, as can the anchoring block 20.

Of course, the invention is not limited to the examples which have just been described.

For example, one can modify the shape of the anchor block, the sub-anchor block and the distribution element to give them another shape, nevertheless allowing to solicit the cementitious material which composes them mainly in compression. The anchoring sub-block may have a shape that is not symmetrical with revolution, with or without axial symmetry, with for example multiple arches, substantially radial or not, starting from the central body.

The arched face 34 of the sub-block 30 may be with one or more edges or not, with one or more facets, shaped ogive, cone, quadric, broken arc. Preferably, however, the presence of ridges will be avoided.

More preferably, the shape of the arched face is such that it has an inclination (slope) with respect to the normal plane (orthogonal) to the X axis at its apex, which increases away from this plane, preferably continuously. The variation of the slope is thus monotonous. The curvature (not inverting) may be regular or not.

The anchoring sub-block 30 can be made with a peripheral portion 33 which is not solid and continues annular but has openings, which extend for example to the distribution element 40 to form separate support legs on the latter.

The surface 36 of the sub-block 30 can be indented, and the distribution element 40 is then advantageously indented in a complementary manner. Such a complementarity of shapes can be relatively easy to create when the sub-block 30 is molded in contact with the distribution element or vice versa.

The bearing face 32 of the sub-block intended to receive the anchor block 20 may be non-spherical, for example be cone-shaped, ogive, quadric, in particular paraboloid

The outer peripheral surface of the block or sub-anchor block may be of revolution or not, being preferably axially symmetrical. For example, the shape of the block, the sub-block or the distribution element is generated by n repetitions of the same pattern by rotation of an angle of 360 ° / n, with for example n equal to 3, in particular in the case of a hexagonal mesh for the reinforcement beam 3.

FIG. 8 illustrates the possibility of replacing the distribution element 40 with a corresponding complementary shape made directly within the structure 1. This is possible when the cementitious material of the structure has sufficient mechanical strength, for example example is a concrete of resistance class C80 / 95 or higher. The complementary shape has as illustrated a receiving cone of the anchoring sub-block 30, against which the face 36 of the sub-anchor block bears.

Although the invention is particularly suitable for a concrete structure, the invention can still be applied to a masonry or mixed structure, for example steel / concrete.

Although a cementitious material is preferred for producing the anchoring sub-block, it is also possible alternatively to use less expensive materials than steel, such as cast iron, or a composite material based on polymers.

Claims

1. Device (10) for anchoring reinforcement (s) (3) of prestressing or structural cable such as a stay, for structure, in particular of concrete (1), comprising:

an anchoring block (20) having at least one housing (22) configured to receive a clamping jaw (21) of an armature (3),

an anchoring sub-block (30) having a bearing surface (32) on which the anchoring block (20) rests and a vault shape whose concavity (38) is oriented towards the structure,

an element (40) for distributing the forces in the structure on which the anchoring sub-block (30) rests.

2. Device according to claim 1, the anchoring sub-block comprising a cementitious material.

3. Device according to claim 2, the cementitious material of the anchoring sub-block (30) being BHP (High Performance Concrete) or BFUHP, preferably BFUHP (Ultra High Performance Concrete Fibré).

4. Device according to any one of claims 1 to 3, the element (40) of distribution of forces in the structure comprising a cementitious material.

5. Device according to claims 2 to 4, the cementitious material of the sub-block (30) being directly in contact with the cementitious material of the distribution element (40).

6. Device according to claim 5, the contacting surfaces being of generally complementary shapes, more exactly complementary, one of the sub-block and the distribution element being preferably molded in contact with the other of the sub-block. and the distribution element.

7. Device according to claim 4, at least one of the sub-block and the distribution element being made with small reliefs (65) which will collapse under the effect of the compression of the sub-block. block on the distribution element, and in crushing will allow a more intimate contact between the sub-block and the distribution element, such reliefs being preferably made in the form of thin ribs, including corrugations or striations radials.

8. Device according to claim 4, comprising at least one element (70) interposed between the sub-block (30) and the distribution element (40), this element (70) being made of a non-cementing material, chosen for crushing under the effect of the compression of the sub-block (30) on the distribution element (40), in particular at least one thickness of a metallic material, preferably ductile, such as a lead strip, or a sheet of a polymeric material.

9. Device according to claim 8, the non-cementitious material or materials present at the interface between the cementitious material of the sub-block (30) and that of the distribution element (40) correspond to the envelope of one or several lost molds used to mold the sub-block or distribution element.

10. Device according to any one of claims 4 to 9, the opening angle of the concavity (38) of the sub-block (30), defined by the half-angle (a) at the top of the cone which s' presses on the edge (53) of the concave face (34) farthest from the anchor block (20), and which is perpendicular to the concave surface (34) at this edge, being between 15 and 90 °, better between 30 and 90 °.

11. Device according to any one of claims 4 to 10, wherein the interface is made between the sub-block (30) and the distribution element (40) so that the sub-block (30) can sliding in the distribution element (40) under the effect of the compression and further jamming in it, and it is available at the interface between the cementitious material of the sub-block and that of the distribution element at minus an intermediate element (70) intended to facilitate this sliding, preferably with a coefficient of friction less than or equal to 0.5.

12. Device according to any one of claims 4 to 11, the interface between the sub-block and the distribution element having an inclination such that the angle (b) formed between the interface and the tangent to the face concave (34) at the interface is acute, preferably between 15 and 90 ° upper limit excluded, better between 15 and 50 °, in particular of the order of 30 °.

13. Device according to any one of claims 4 to 12, wherein is given to the surfaces (36, 49) of the sub-block and the distribution element intended to bear on one another a shape which makes it possible to ensure that, despite the manufacturing tolerances, the distribution of the stresses remains favorable to the good mechanical strength of the sub-block and the distribution element, and preferably the nominal angle given to the surface the sub-block intended to bear on the distribution element is chosen so that by integrating the manufacturing tolerances there is always a first contact which is made, at the placing of the parts, in the zone which is farthest from the concave face of the sub-block.

14. Device according to any one of claims 4 to 13, the distribution element (40) having a compressive strength greater than that of the concrete structure, better intermediate between that of the material of the sub-block anchor and that of the concrete of the structure, preferably being BHP.

15. Device according to any one of claims 4 to 14, the distribution element (40) having a shape widening towards the structure, in particular frustoconical, preferably being traversed by an opening (41) for the passage of reinforcements (3) widening towards the anchoring sub-block.

16. Device according to any one of claims 4 to 15, the distribution element (40) being without reinforcing reinforcement.

17. Device according to any one of the preceding claims, the bearing face (32) of the anchoring sub-block (30) being concave towards the anchor block (20) and the anchor block (20). having an inner face (24) convex, of complementary shape, in particular spherical.

18. Device according to any one of the preceding claims, the anchoring block (20) being made of cementitious material, preferably BFUHP, preferably comprising metal inserts (22) for receiving the clamping jaws (21), comprising preferably also a bursting frame (23).

19. Device according to any one of claims 1 to 16, the anchor block (20) being metallic and the bearing face (32) being flat.

20. Device according to any one of the preceding claims, the anchoring sub-block (30) being without reinforcement.

21. Device according to any one of the preceding claims, the anchor block (20) having a plurality of receiving receptacles (29) receiving jaws (21) for clamping reinforcements (3).

22. Concrete structure comprising at least one prestressing reinforcement (3), to the concrete structure (1) of the structure, maintained in tension by means of an anchoring device (10) as defined in any one of the preceding claims.

23. Work according to claim 22, comprising a concrete structure (1) in which is embedded the distribution element (40).

24. The structure of claim 23, the concrete structure (1) having a conduit (8) opening through a flared portion on the distribution element (40).

25. Method for anchoring at least one reinforcement (3) of prestressing or structural cable of a structure, in particular of concrete, in particular one or more strands (3) of cable, comprising the anchoring of the reinforcement (3) within an anchor block (20) of an anchoring device (10) as defined in any one of claims 1 to 21.

26. The method of claim 25, comprising the tensioning of the or reinforcements (3) with a jack bearing on the anchor block (20) or on the sub-block (30).

27. A method of manufacturing an anchoring device (10) of reinforcement (s) (3) for prestressing or structural cable, for a structure in particular made of concrete, of a device (10) according to any one of Claims 1 to 21, this device comprising:

- An anchor block (20) having at least one housing (22) configured to receive a jaw (21) for clamping a prestressing reinforcement (3) or structural cable, in particular a stay,

an anchoring sub-block (30) comprising a cementitious material, having a bearing face (32) on which the anchoring block (20) rests and a vault shape whose concavity (38) is oriented towards the 'work,

method in which the anchoring sub-block (30) is made by means of a cement material molding or extrusion equipment.

28. The method of claim 27, the anchoring sub-block (30) being made in an on-site workshop.

29. Method according to one of claims 27 and 28, the anchoring sub-block (30) being disposed at least partially in a reservation (2) of the structure.

30. Method according to one of claims 27 to 29, wherein against-mold one of the anchor block and the sub-block on the other.

31. Method according to any one of claims 27 to 30, the anchoring device comprising a distribution element (40), in which method is counter-molded one of the sub-block (30) and the element of distribution (40) on the other.

Anchoring system for prestressing reinforcements, for anchoring device (10) according to any one of claims 1 to 21, comprising reinforcement clamping jaws (21) and an anchoring block (20). made in BFUHP, having housings, in particular having at least one portion of conical shape, to receive the jaws (21) and ensure the jamming of the reinforcements under the effect of the tension in them, the anchor block (20). ) having a face (24) through which the forces are transmitted to the structure, of convex shape towards the structure.

33. System according to claim 32, the jaw receiving housings (21) comprising metal inserts (22) having at least one portion of conical shape.

34. System according to one of claims 32 and 33, comprising as many housing (22) for the frames as there are reinforcements.

35. System according to any one of claims 32 to 34, the anchor block having a bursting armature (23) at its periphery, the opposite side to the face (24) which transmits the forces.

36. System according to any one of claims 32 to 35, having an outer surface (25) widening towards the face (24) which transmits the forces, in particular of frustoconical shape.

37. Anchorage sub-block (30) for an anchoring device (10) for prestressing reinforcement (3) or structural cable such as a stay, for a structure, in particular made of concrete (1). ), this device comprising:

the sub-block being made of BHP or BFUHP, comprising a bearing face (32) for receiving the anchoring block (20) of prestressing reinforcements (3), passages for the prestressing reinforcements, a part a force-transmitting peripheral (33) and a central portion defining a concavity (38) on the opposite side to the bearing face (24), the peripheral portion (33) having a connecting end face (36) forming an acute angle (b) with the tangent to the concave surface (34) having the concavity (38).

38. Sub-block according to claim 37, being of external shape of revolution or axially symmetrical around the axis (X) according to which the tension in the reinforcements (3) applies.

39. Sub-block according to one of claims 37 and 38, the bearing face (32) being of concave shape, in particular complementary to that of the anchor block (20).

40. Sub-block according to any one of claims 37 and 38, the bearing face (32) being flat.

41. Sub-block according to any one of claims 37 to 40, consisting exclusively of BFUHP, without integrated reinforcement.

42. A distribution element (40) for an anchoring device (10) as defined in any one of claims 1 to 21, comprising a BHP body, through which a central opening (41) for the passage of prestressing frames (3), having a surface (49) for receiving an anchoring sub-block (30) and an outer peripheral surface (46) which widens away from the surface (49), in particular frustoconical shape.

43. Distribution element (40) according to claim 42, the central opening (41) having a section which increases towards the anchoring sub-block (30) and preferably having a face (47) opposite the anchoring sub-block (30) which is flat and perpendicular to the axis (X) of the central opening (41).

44. Anchoring device (10) for a concrete structure, comprising an anchor block (20) for maintaining in tension prestressing tendons (3) or structural cable, in particular a stay, a sub-block of anchorage (30) on which the anchor block (20) is supported and a distribution element (40) to be drowned at least partially in the concrete structure (1) of the structure, the anchoring sub-block ( 30) and the distribution element (40) being made at least partially of cementitious materials of greater compressive strength than the concrete of the structure (1), the compressive strength of the anchoring sub-block ( 30) being greater than that of the distribution element (40), the anchoring sub-block (30) being preferably made of BFUHP, the distribution element preferably being made of BHP, the anchoring block (20) being preferably made of a cementitious material, in particular BFUHP, comprising a system as defined in any one of claims 32 to 36, the sub-block anchor (30) being as defined in any one of claims 37 to 41, and / or the distribution member being as defined in one of claims 42 and 43.