Patent Application
20200199831
The present invention relates to devices used to deflect structural cables, in particular stays.
Such cables often comprise a bundle of individual tendons that are tensioned and anchored at their ends.
The design of a construction work, in particular a bridge, can lead to deflecting the cable in one or more areas of the path thereof.
For example, it is known to use pylons through which stays pass that have a path in general inverted V shape. The stays are then deflected in the pylons by means of a saddle.
This saddle aims in particular to deflect the tendons of the cable without altering their mechanical strength, and sometimes to provide sufficient friction between the tendons and the conduits of the saddle that each receive a tendon for an optimal take up by the pylon receiving the saddle of the differential forces acting on the cable on either side of the pylon.
A possible general saddle configuration is based on the anchoring of the cable in the saddle so as to define within the saddle a cable portion subject to a tension that is predetermined and substantially constant over time. This configuration involves anchoring devices in the saddle, suited for this purpose. The document CN 20250087 U illustrates such a configuration.
One of the difficulties encountered relates to the difficulty of designing such anchoring devices which are mechanically optimized and allow an optimal protection of the tendons against corrosion and mechanical action.
An object of the present invention is to improve the mechanical behavior of the cable and of the associated equipment in a deflecting saddle, while also providing optimal protection from the armatures from which it is made.
For this, the invention relates to an assembly comprising:
a structural cable comprising a plurality of tendons anchored at two opposite ends of the structural cable between which they extend without interruption; and
a saddle configured for deflecting the structural cable between the two ends thereof.
The saddle comprises:
a body;
a plurality of conduits formed in the body and each receiving and guiding one of the tendons; and
two anchoring devices configured for anchoring the tendons so as to define a first portion of the structural cable received in the saddle, where the tendons are subject to a prestressed tension that is substantially constant over time, and at least one second portion of the structural cable, where the tendons are subject to tensions that are variable over time.
At least one of the two anchoring devices comprises:
an anchoring plate comprising anchoring openings each receiving one of the tendons, wherein the anchoring plate has a rear surface bearing against the body; and
wedges each received in a respective anchoring opening of the anchoring plate in order to lock one of the tendons of the structural cable therein.
Typically, the body is made of material molded inside a tubular envelope of the saddle.
In an embodiment, each tendon of the structural cable is coated with an individual sheath removed at the anchoring device. The anchoring openings may then have a frustoconical shape through the anchoring plate, the frustoconical shape having a minimum diameter that is strictly greater than the diameter of the tendon coated with the individual sheath.
At least one of the anchoring openings may receive a lining surrounding the wedge so as to define in the anchoring opening a passage having a cross-section smaller than the anchoring opening, by which a tendon passes through the anchoring plate.
Alternatively, for at least one anchoring opening, the wedge is in direct contact with the frustoconical wall of the anchoring opening so as to anchor the tendon in the anchoring plate.
At the anchoring device, the individual sheath of each tendon may be removed over a portion of length less than three times the length of the wedge.
In an embodiment, the anchoring plate has a thickness in a range of 1 to 1.5 times the length of the wedge.
The saddle may be fitted with at least one guiding member comprising a plurality of guiding channels each receiving one tendon and configured to guide angular deviations of the tendons in at least one second portion of the cable.
The saddle may further comprise a sealing system including an axially compressed seal to make a seal around the tendons, the anchoring plate of one of the anchoring devices being located between the sealing system and the body of the saddle.
When the saddle comprises at least one guiding member having a plurality of guiding channels each receiving one tendon and configured to guide angular deviations of the tendons in at least one second portion of the cable, the sealing system may advantageously be placed between the guiding member and the anchoring plate of said anchoring device.
In an embodiment, an O-ring is placed in each conduit formed in the body for receiving a tendon of the structural cable, and a protective material is injected in a volume made tight by the axially compressed seal and the O-rings, and containing the anchoring plate and the wedges. If each tendon of the structural cable is coated with an individual sheath, that sheath may be removed in an area located between the O-ring and the axially compressed seal.
In an embodiment, the anchoring plate has the rear surface thereof bearing against the body, a front surface and a peripheral surface received freely in a housing coaxial with the structural cable at the anchoring device.
Another aspect of the present invention relates to a method for deflecting a structural cable comprising a plurality of tendons. The method comprises:
placing a saddle body in a region located between two ends of the structural cable, wherein the body is formed with a conduit for each tendon of the structural cable;
inserting each tendon in an anchoring opening of a first anchoring plate, in one of the conduits formed in the body and then in an anchoring opening of a second anchoring plate;
tensioning the tendons to a preset prestressed tension in a first portion of the structural cable located between the first and second anchoring plates and locking the tendons in each of the first and the second anchoring plates, while each of the first and second anchoring plates has a rear surface bearing against the saddle body; and
anchoring the structural cable at the two ends thereof such that the tendons experience tensions variable over time in two second portions of the structural cable each located between one end of the structural cable and one of the first and the second anchoring plates.
In an embodiment of the method, each tendon is successively threaded into a guiding channel of a guiding member of a first anchoring device, into a passage formed in a sealing system of the first anchoring device, into the first anchoring plate belonging to the first anchoring device, into one of the conduits formed in the body, into the second anchoring plate belonging to a second anchoring device, into a passage formed in a sealing system of the second anchoring device and into a guiding channel of a guiding member of the second anchoring device.
When each tendon of the structural cable is coated with an individual sheath, it is possible, after inserting a tendon in an anchoring opening, to remove the individual sheath of the tendon at said anchoring opening for inserting therein a wedge for locking the tendon.
In an embodiment of the method, after tensioning the tendons in the first portion to the prestressed tension and locking in the first and second anchoring plates, the tension is released and then the tendons are tensioned in each second portion to a value below the prestressed tension before anchoring the structural cable at both ends thereof.
Tensioning and locking of tendons in one of the first and the second anchoring plates, placed behind a housing formed in a tubular envelope receiving the saddle body, may comprise:
applying a tension over the full length of at least one tendon at at least one of the ends of the structural cable;
arranging an overlocking device comprising at least one jack on a front side of the housing; and
controlling the jack in order to drive, around said tendon, a wedge into an anchoring opening of said anchoring plate.
The invention will be better understood upon reading the following detailed description, given solely as an example and referring to the attached figures, in which:
In this configuration, the work 2 further comprises a deck 6 and a pylon 8 in which the stays 4 are received and deflected. The stays 4 are for example anchored at the ends thereof in the deck 6 and are also configured for suspending the deck.
The pylon 8 comprises, for at least one stay 4 a saddle 10, in which the corresponding stay 4 is received and deflected. Each saddle 10 can receive a single stay 4.
Referring to
The stay 4 comprises a first portion A received in the saddle 10 where the tension is constant over time. This tension corresponds to a prestressed tension for this portion A, which results from tensioning the tendons of the stay to a prestressed tension. Further, the stay 4 comprises at least one second portion B extending away from the first portion A, where the tension is variable over time and is less than the prestressed tension of the portion A. The portion A and the portion B are successive, portion B extending portion A.
For example the stay 4 has two second portions B each extending from one end of the first portion A away from the saddle. These portions B extend from the corresponding end of the portion A to one of the ends 4E of the stay 4.
Thus, in the typical configuration of the invention, the stay comprises three successive portions B, A, B between its ends.
The portions B are substantially straight, but can have a catenary deflection less than or equal to 0.5% of the length of the stay 4. The portion A is advantageously curved.
The stay 4 is anchored and tensioned near opposite ends 4E thereof. The anchoring of these ends is for example done by active type anchors also suited for tensioning the stay.
The stay 4 comprises a sheath 11 and at least one tendon, or armature, 12 that is taut and arranged in the sheath 11.
The sheath 11 is made, for example, of HDPE, high-density polyethylene. The sheath comprises two portions 111, 112 covering respectively at least one part of the two portions B, the sheath 11 is absent in portion A.
Advantageously, the sheath 11 extends cumulatively over the majority of the portions B, for example over a portion of length greater than 80% of the cumulative length of these portions.
Referring to
Advantageously, each sheath portion comprises a connection sleeve 11C forming one end of this portion turned towards the saddle 10 and intended to be fixed to the saddle 10 (and/or to the pylon), as described below.
This sheath portion 111, 112 comprises, near the end thereof adjacent to the saddle, a bending sleeve 11L suited for accommodating the bending of the sheath portion in this region.
In the context of the invention, each tendon 12 extends from one end 4E of the stay to the other end 4E, and does so without interruption. It is anchored in the end anchors of the stay 12.
Consequently, the stay 4 does not have a coupler between disjoint segments of a tendon.
Each tendon 12 has a metal strand 14 forming the main structural part of the tendon. In one embodiment, each tendon 12 also comprises an individual sheath 16 which surrounds the tendon 14 over at least one part of the length thereof. This sheath is for example of a plastic material such as HDPE.
This sheath extends over a part of the portion A within the saddle 10. Further, the sheath 16 of the tendon 12 extends over at least one region of the portions B of the stay, and preferably over the entirety of the portions B.
The tendon 12 for example has an outer diameter in a range of 15 to 22 mm on its sheathed part, and equal for example to 19.5 mm. Further, the strand 14, i.e. the tendon 12 over a portion without sheath 16, has a diameter in a range of 12 to 17 mm, and equal for example to 15.7 mm.
Each tendon 12 optionally comprises an anti-corrosion protective material coating the strand 14 and contained within the sheath 16. Advantageously, this material is lubricating. For example, the material is, or comprises, wax, grease or a polymer resin.
Referring to
The saddle 10 comprises a body 18, a tubular envelope 22 and two anchoring devices 20 for anchoring the tendons 12 of the stay 4 in the saddle 10 and defining the portions A and B of the stay.
The envelope 22 forms the frame of the saddle 10. It is arranged in the saddle 10 and delimits on the inside, i.e. in the inner volume thereof, the body of saddle 18.
The cross-section of this envelope 22 is for example polygonal, such as rectangular. Alternatively, this cross-section is circular.
The envelope 22 advantageously comprises diaphragms (not shown) orthogonal to the direction along which the envelope 22 extends. This direction corresponds to the mean line of the envelope 22 which matches the deflected path of the stay 4 received in the saddle 10. The diaphragms are configured to strengthen the saddle. They define successive body regions 18 within the envelope 22. These diaphragms are bored at least for the passage of the tendons 12 of the stay. They materialize the position of the conduits laid out through the body 18 and locally define their cross-section.
The body of saddle 18 comprises a plurality of individual conduits 24. Each conduit 24 passes through the body and is intended for receiving and guiding a single tendon 12 of the stay 4 associated with the saddle 10 from one end of the body 18 to the other. Each tendon 12 bears on the walls of the corresponding conduit 24 over at least one part of the length thereof, which guides the tendon along the curve of the saddle. Advantageously, the walls the conduits 24 are smooth, with the geometry minimizing the friction between the sheath 16 of the tendons and the walls of the conduits 24. Alternatively, these walls are configured to allow a high friction between the tendons and the saddle 10.
The respective directions, or mean lines, of the conduits 24 are advantageously parallel to each other. These directions have a curved trajectory, comprising for example a circular arc shaped central segment thus conferring this trajectory on the portion A of the stay.
The body 18 is preferably made of molded material such as concrete. The concrete in question has an appropriate mechanical strength for supporting the bearing and guiding of each tendon 12 in an individual conduit 24 without damaging its sheath 16. With the goal of limiting the metal reinforcing required for this strength, the type of concrete used is advantageously UHPFRC (Ultra-High-Performance Fiber-Reinforced Concrete).
Advantageously, the body 18 and the envelope 22 define a housing 26 coaxial to the structural stay near one of the anchoring devices 20 at at least one of the longitudinal ends of the body and the envelope. Advantageously, this is the case for each of the longitudinal ends of the envelope 22. In other words, the saddle 10 comprises, near each of the ends thereof, a housing 26 for receiving one of the anchoring devices 20.
The anchoring devices 20 are configured for anchoring the tendons 12 of the stay 4 such that the portion of stay A located between these two anchoring devices 20 is subject to a so-called prestressed tension that is substantially constant over time. Thus, the stay portion experiences a tension made independent of the governing tension in the portions of stay B located beyond these anchoring devices, which may vary, in particular under the effect of the passage of convoys on the bridge, wind effects, thermal expansion phenomena, etc.
Each anchoring device 20 is arranged in one of the housings 26 located at the longitudinal ends of the saddle 10 and are held in place there.
Each housing 26 occupies the entirety of the volume radially delimited by the tubular envelope 22. Further, each housing 26 is longitudinally delimited between the body 18 and the end of the saddle 10, which is advantageously located at one of the surfaces of the pylon.
Still with reference to
The anchoring plate 28 is configured for receiving the wedges 30 of various tendons 12 in order to anchor them in the saddle 10.
The rear surface of the anchoring plate 28 is applied against the end of the body 18 delimiting the housing 26.
The anchoring plate 28 bears against the body 18. More specifically, when the anchoring plate 28 is flat, it is bearing against a flat surface of the body, advantageously formed by an end surface of the body.
In a first configuration, the plate 28 bears directly against the molded and hardened material of the body 18.
Alternatively, in a second configuration, the plate 28 bears against the body via a flat wall 34 interposed between the body 18 and the anchoring plate 28. This wall 34, which corresponds to an end diaphragm of the tubular envelope 22, may have served as a form, with the envelope 22, during molding of the UHPFRC or other material of the body 18. It is perforated to allow the passage of form elements used to form the conduits 24 through the body 18. The form elements forming the conduits 24 can be in the form of tubes or cylinders of elastomer. They are engaged in the holes present in the walls 34 of the two anchoring devices 20 on either side of the saddle and in the intermediate diaphragms. Once the material of the body 18 has been poured and hardened, they are extracted by pulling on the ends thereof exceeding past the walls 34. During their extraction, they separate from the molded material because of the reduction of their cross-section caused by the applied traction and their elasticity.
Since the anchoring plate 28 is placed bearing against the body 18 (directly or via the wall 34), it is almost unstressed in bending when the prestressed tension is applied to the tendons in the portion A of the stay.
Advantageously, the bearing of the rear surface of the anchoring plate 28 against the body 18 is done such that the region of the anchoring plate 28, in which the anchoring openings 36 described below are formed, is bearing against the body 18 over substantially the full rear surface area thereof In other words, the net cross-section of the anchoring plate 28 is completely bearing against the body 18, meaning entirely in contact with the body 18 or the wall 34. In particular, as in the configuration shown in
The rear surface of the anchoring plate 28 and the surface against which this rear surface bears (front surface of the body 18 or of the wall 34) have a good flatness. In some implementations, a bedding product that sets is placed between these two surfaces so as to form an interface joint providing stable bearing. For example, this product is a grout or resin.
The anchoring plate 28 has an outer cross-section whose shape advantageously matches that of the inner cross-section of the envelope 22 near the housing 26, for example polygonal or circular. To further provide a good bearing for the rear surface of the anchoring plate 28 on the body 18, it is desirable that its peripheral surface be freely received in the housing formed by the envelope 22, for example by having a radial clearance as can be seen in
The anchoring plate 28 is advantageously made of metal, for example steel. The steel in question has a grade providing sufficient mechanical resistance against bursting stresses induced in the anchoring plate 28 by the radial tightening exerted by the wedges 30 on the tendons 12 for anchoring them.
The anchoring plate 28 comprises anchoring openings 36 each intended for the passage of one tendon 12 and receiving the wedge 30 serving to anchor this tendon in the plate 28.
Each anchoring opening 36 extends perpendicularly to the bearing surface of the anchoring plate 28 by being aligned with one of the conduits 24 of the body 18.
Each anchoring opening 36 is aligned with the local direction of the corresponding tendon 12, with possibly a small angle with the direction of the conduit 24 at the outlet thereof, as shown in
Each anchoring opening 36 has a general conic frustum shape and inside defines a conic frustum passage from the rear surface to the front surface of the anchoring plate 28 for the passage of a tendon 12. The smallest cross-section of the anchoring opening 36 is turned towards the body 18.
The minimum diameter of the anchoring opening 36 is strictly greater than the diameter of the tendon 12 provided with the individual sheath 16. The tendon individually provided with sheath 16 can thus be threaded into the anchoring opening without coming into contact with the anchoring plate. For example, this minimum diameter is in a range of 21 mm to 26 mm.
The anchoring openings 36 have a maximum diameter in a range of 31 mm to 36 mm, for example. The anchoring openings 36 can all be identical in shape and size.
Each anchoring plate 28 delimits one end of portion A of the stay.
Thus, in
Each wedge 30 anchors one tendon 12 to the anchoring plate 28 by conical wedging.
For example, each wedge 30 is composed of three keys in the shape of frustoconical sectors, assembled around the strand 14 by means of a ring inserted in a circumferential groove provided near the larger end thereof. These three keys are placed around the strand 14 after installation of the tendon 12 in the saddle 10. In order to receive the strand 14, the wedge 30 formed by assembly of the three keys has an axial bore whose inner surface may have striations serving to increase the tendon-wedge friction.
Each wedge 30 has a length indicated by Lm. This length, corresponding to the size of the wedge along the axis of its frustoconical shape, is identical for all the wedges 30 of a given anchoring device and advantageously between the various anchoring devices 20.
The anchoring plate 28 has a thickness between 1 and 3 times the length Lm of a wedge 30. Preferably, this thickness is between 1 and 1.5 times Lm.
In an implementation of the invention, the anchoring device 20 comprises a lining, or sleeve 38 in each anchoring opening 36. This lining 38 is arranged between the wedge 30 and the frustoconical surface of the anchoring opening in order to reduce the dimensions of the passage in the anchoring plate receiving the corresponding tendon and defined on the inside in this anchoring opening 36.
Each lining 38 has a general frustoconical configuration. The end of the lining with the smallest dimensions is turned towards the body 18. This end is advantageously located substantially at the opening of the anchoring plate 28 or else recessed therefrom in the anchoring opening 36. In other words, this end does not project outside the anchoring plate 28 towards the body 18. At this end, the lining 38 has an inner diameter for example in a range of 14 to 21 mm.
The end region of the lining 38 is optionally beveled in the area of the inner surface of the lining to get the preferred dimension.
The lining 38 has an outer conic frustum surface with shape complementary to the inner conic frustum surface of the anchoring opening 36, and an inner conic frustum surface with shape complementary to the outer conic frustum surface of the wedge 30.
Each lining 38 is mobile and can be arranged on the associated tendon by lateral engagement before placement of the wedge 30 or at the same time. The lining can also be formed by assembly of several (for example two or three) segments each covering an angular sector of the frustoconical shape.
The linings 38 are advantageously made from metal, for example from steel, in order to support the force for wedging the tendons.
As a variant, the linings 38 are not used. In these configurations, the wedge 30 which engages with the tendon 12 passing into the anchoring opening 36 is in direct contact with the anchoring opening 36 (meaning the anchoring plate 28). The two configurations can be used together, for example with one being used for one of the anchoring devices 20 and the other for the other device 20.
The retaining plate 32 prevents the withdrawal of the wedges 30 from the anchoring openings 36 of the anchoring plate 28. Such a withdrawal could for example occur in case of accidental excess tension or dynamic effect in a portion B. Further, the retaining plate 32 contributes to the leveling of the wedges 30.
For this purpose, the retaining plate 32 is located across from the front surface of the anchoring plate 28. It is arranged against the rear ends of the wedges.
For example, the retaining plate 32 is made of plastic. In some configurations, it is made of thermostable plastic, such as polyetheretherketone, PEEK. Its cross-section covers all of the wedges 30 of the adjacent anchoring plate 28.
The retaining plate 32 comprises a passage for each tendon 12. These passages are aligned with the anchoring openings 36. Preferably, they are sized such that the tendons do not come into contact with the retaining plate 32 during the operational life of the saddle 10. For example, these passages have a diameter in a range of 16 to 23 mm.
In an alternative configuration, instead of the passages, the retaining plate 32 has a general comb configuration in which the openings are configured for lateral engagement of this plate on the bundle of tendons 12 subsequent to the threading of the tendons 12 in the anchoring plate 28.
Still referring to
The sealing system 40 can be of the stuffing-box type, with a deformable seal 42 sandwiched between the guiding member 46 and a bearing plate 44. Tightening the seal 42 by axial compression seals the housing 26 and thus blocks penetration of water into the environment of the anchoring device 20 and into the conduits 24.
Advantageously, the bearing plate 44 is located between the seal 42 and the retaining plate 32. The bearing plate 44 is, for example, made of metal, such as steel. It comprises a passage for each tendon.
The seal 42 is for example made of neoprene and also comprises passages aligned to receive the tendons.
The bearing plate 44 is for example displaceable in the housing 26 in order to compress and deform the seal 42, for example via one or more tightening screws accessible from the front surface of the saddle 10 (not shown).
In another implementation, the bearing plate 44 is in a fixed position, with its rear surface in contact with the front surface of the retaining plate 32. In this case, compression of the seal 42 is performed by pushing the deflecting member 46 towards the inside of the tubular envelope 22.
Still referring to
The guiding member 46 comprises a plurality of guiding channels 48, each intended for receiving and guiding a tendon 12. Here, guiding is understood to mean that the tendons 12 are able to come into contact with the walls of the channels 48.
The guiding channels 48 are aligned with the passages in the seal 42, themselves aligned with the anchoring openings 36 and with the conduits 24.
Each guiding channel 48 has a widening towards the running part of the stay formed by the corresponding portion B, as described in the patent EP 1 181 422 B1. This widening is, for example, intended to accommodate angular deflections of the tendons 12 in particular dynamic deflections, resulting for example from vibrations of the stay under the effect of wind, passage of vehicles over the bridge, etc.
The guiding member 46 is for example made of HDPE.
Still referring to
This attachment device 50 comprises an attachment module 52 configured for the attachment of the associated sheath portion 11 to the saddle 10.
This module 52 advantageously includes a flange 53 delimiting a space for receiving and holding in place a portion of the connection sleeve 11C of the sheath 11 bearing against the saddle 10. The portion in question corresponds for example to a peripheral collar arranged at the end of this connection sleeve 11C. The flange itself is for example screwed in place in the pylon.
Advantageously, the attachment module 52 further comprises a bearing element 55 forming a counter-flange for the flange 53. This bearing element 55 bears against the corresponding surface of the pylon, and the sleeve 11C of the sheath 11 is inserted between the flange 53 and this bearing element. This element 55 comes for example in the shape of a lip or flange applied against the surface of the pylon.
The bearing element 55 is advantageously part of the envelope 22 itself, at the end of which it is located.
The attachment device 50 further comprises a plate 54 against which the anchoring device 20 bears in order to keep it in the housing 26. For example, it is the guiding block 46 that is bearing against the plate 54.
This plate 54 is located near the corresponding opening of the envelope. For example, it is located outside the envelope 22.
This plate 54 is for example held in place by the flange 53 jointly at the end of the sheath 11. For example, it is then in contact with the bearing element 55. Alternatively it is in direct contact with the pylon.
This plate 54 advantageously has an annular configuration defining the central opening for passage of the set of tendons 12.
Alternatively, this central opening is replaced by perforations which are located facing guiding channels 48 and which have a diameter greater than or equal to that of the channels 48 near the opening thereof turned towards the plate 54.
Optionally, the region of the surface of the pylon 8 where the attachment device 50 is located has a region in which the attachment device 50 is housed. This region can be configured in order to prevent water run-off against the surface of the attachment device 50.
Referring to
In the context of the invention, for at least one anchoring device 20, and advantageously for both, the sheath 16 of a given tendon 12 is removed over a portion of the tendon labeled 12P which is received in the anchoring opening 36 and which extends on both sides of the anchoring opening 36. It is near this portion 12P that the wedge 30 holds the strand 14 of the corresponding tendon.
Advantageously this portion 12P has a length less than three times the length Lm of the wedges 30. It has for example one end located in the thickness of the seal 42 and an opposite end in the conduit 24 of the body 18.
In this configuration, the stripped portion 12P of the strand 14 is directly received in the seal 42, the bearing plate 44, the retaining plate 32, the anchoring plate 28 and the beginning of the corresponding conduit 24. Advantageously, except for the anchoring plate 28 at which the strand 14 is in contact with the wedges 30, the strand 14 remains spaced from the structural elements of the anchoring device 20, in particular from the walls of the passages in which the portion 12P is received.
Along the portion 12P, a protective material 56 is brought into contact with the stripped strand 14, in order to protect the steel of the strands 14 against corrosion, as well as with the other metal elements of the anchoring device 20.
Advantageously, this product has lubricating properties. It is for example a grease, wax or gel having equivalent properties.
The protective material 56 is for example injected into the housing 26. The conduits 24 are advantageously each provided with an 0-ring 57 near the end of the portion 12P in order to prevent the material 56 from penetrating farther forward in the conduit 24.
The seal 42 further prevents leakage of the material 56 from the housing 26 when it is deformed.
The method for deflecting a stay by means of the saddle 10 according to the invention will now be described with reference to
The first step consists of molding the body 18 of the saddle 10 in the way previously indicated; the UHPFRC, or other sufficiently strong moldable material, is injected into the space delimited by the tubular envelope 22, the walls 34 against which the anchoring plates 28 come to bear on either side of the body 18, and the elastomer molding elements corresponding to the conduits 24. After setting of the UHPFRC, the elastomer molding elements are extracted by pulling.
This step of molding the body 18 does not need to be done on the worksite. The envelope 22 and the body 18 can be prefabricated in factory. It is conceivable that the body 18 is formed with the envelope 22 without molding operation, although molding is the most convenient and most reliable method for mastering the interface that the conduits 24 provide to sheathed tendons 12. If the body 18 is prefabricated, it is raised to its location on the pylon before installation of the stay 4.
Once the stay 4 has been lifted to the location of the saddle 10 on the pylon 8, each tendon 12, provided with the individual sheath 16 thereof over the full length thereof, is threaded through a portion 111 of the general sheath 11 for the stay, the conduit 24 thereof formed in the body 18 of the saddle 10, and also the elements composing the anchoring device 20, and then in the other portion 112 of the general sheath 11 of the stay. At the saddle 10, the tendon 12 is threaded into these elements in the order they are intended to have once the saddle is completed, namely:
It is possible to also place the wedges 30 and/or their linings 38 around the tendons 12 between their threading in the retaining plate 32 of one or the other anchoring devices 20 and their threading in the associated anchoring plate 28 if the strand 14 with its sleeve 16 can be received in the wedges in the untightened state.
Beyond the saddle 10, the tendons 12 of the stay 4 are collectively threaded in the second section of the sheath 11 in order to go back down to the second end of the path of the stay. At this stage, the sheaths 11 on either side of the pylon 8 are separated therefrom, as are the guiding members 46, the not yet compressed seals 42, the bearing plates 44 and the retaining plates 32, in order to make the housing 26 accessible and to free sufficient space to perform the anchoring with the help of the wedges 30.
The ends of the tendon 12 are provisionally anchored near the ends of the stay 4, for example at the deck 6, a roof, a retaining mass, etc.
The individual sheath 16 of the tendon 12 is removed over its two portions 12P (one for each anchoring device 20), so as to bare the strand 14.
The tendon 12 is then tensioned at the temporary anchors thereof. For example, this tensioning is done substantially simultaneously near the two active anchors located at the ends 4E of the stay.
The tension in the tendon 12 is brought to a tension corresponding to the selected prestressed tension. This value is for example in a range of 0.5 to 0.7 GUTS (“Guaranteed Ultimate Tensile Strength”) of the tendon. For example this tensioning is implemented by a standard device for tensioning tendons, for example a single-tendon hollow jack.
Next, the tendon 12 is anchored in the anchoring plate 28 of both anchoring devices 20 such that the tension applied to the tendon 12 during the previous step, equal to the prestressed tension, will permanently remain in the portion A located in the body 18.
In each of the two anchoring devices 20, the wedges 30 are assembled around the tendons 12 (if they were not already put in place during threading of the tendons), and also the linings 38 thereof if they are used, and then driven into the openings 38 around the bare portions 12P. Each wedge can be overlocked in this configuration by application of a calibrated pressure.
The overlocking consists of applying a force on the rear of the wedge 30 configured for driving the wedge into the anchoring opening 36 thereof, beyond the simple penetration induced by a passive locking of the wedge.
An additional unwanted penetration, sometimes known under the name of “wedge passive return,” of each wedge 30 into its anchoring opening 36 during the release of the tension applied to the active anchors of each tendon 12 during the following step can be prevented or significantly limited with this overlocking.
A device 58 such as shown in
The device 58 comprises an overlocking seat 60 attached to the saddle 10 and provided with one or more jacks 62 intended to bear on the wedge 30 for overlocking it in the anchoring opening 36.
Advantageously, this connection is implemented via the retaining plate 32 brought close to the housing 26 and an overlocking spacer 63 placed between the retaining plate 32 and the wedge 30 in order to transfer the force generated by the jacks 62 to the wedge 30 and also to press the wedge 30 into the anchoring opening 36.
The retaining plate 32 can be fixed to the seat 60 by a plate 64 connected to the jacks 62.
During this step, the bearing plate 44 can be placed against the retaining plate 32, the seat coming to bear against the retaining plate 32 via the bearing plate 44.
The overlocking spacer 63 has for example a generally hollow cylindrical shape in which the tendon 12 is received. It is adapted for being brought onto the tendon by lateral engagement and also being released laterally. It can have a Y-shaped cross-section, meaning with the region of V or U general configuration supplemented by a rib extending from the central part of this region. This rib increases the bending stiffness and the cross-section bearing on the plate 32.
The device 58 is advantageously attached to the saddle 10 via the attachment device 50, since the sheath 11 is not yet attached to it.
Once the wedge 30 is ready to be overlocked into the anchoring opening 36 thereof, the jacks of the device 58 push the retaining plate 32 towards anchoring opening 36, which presses the wedges 30 into the anchoring opening under the force which the spacer 63 passes on to it.
The jacks 62 are then released, the plates 32 and 44 are pulled back and the spacer 63 is released from the tendon 12. The wedge 30 remains firmly anchored in place in the anchoring opening 36 thereof under the effects of the steady tension in the portion A and of the overlocking operation.
The device 58 is kept in position until the installation of the last tendon as described above.
The overlocking of the two wedges associated with the tendon 12 has the consequence of freezing the tension in the portion of the tendon located between the two anchoring devices 20 at the prestressed tension which will next remain substantially constant.
The overlocking operation can be done tendon by tendon, group of tendons by group of tendons, or collectively for all the tendons 12 of the stay 4. It could possibly be sufficient to do this operation on only one side of the pylon 8.
Next, the temporary anchor of the ends of the stay 4 is released, and then the ends of each tendon 12 are anchored in their permanent anchor at the tension desired in the portions B. For each tendon, this tension, for example in a range of 0.2 to 0.6 GUTS, is less than the prestressed tension in portion A.
The device 58 is dismantled before or after execution of the final anchors of the ends of the stay 4.
For each of the first and second anchoring devices 20 on both sides the pylon 8, the retaining plate 32 and the tightening plate 34 are placed in the housing 26, as are the seal 42 and the guiding member 46. The portions 111, 112 of the sheath 11 can then be fixed to the saddle 10 via the attachment devices 50.
During this attachment, the plate 54 bears on the guiding member 46 which comes to compress the seal 42 and achieve the sealing of the inner volumes of the saddle 10.
The protective material 56 is injected into the housings 26 on each side of the pylon 8 such that it protects the strands 14 of the tendons 12 over the portions 12P without sheath 16. For the injection, the openings 70 prepared radially in the envelope 22 near the housing 26, for example next to the retaining plate 32 can be used.
The invention avoids making use of couplers for the tendons in the area of the pylon, such couplers are devices of large volume and high cost, whose mechanical strength (in particular dynamic) can prove to be critical and which require taking tricky measures for guaranteeing their proper protection and that of the tendons against corrosion.
The disposition of the anchoring plate 28 bearing against the body of molded material 18 avoids the exposure of this plate 28 to flexural forces during operation. The anchoring plate 28 can, therefore, be relatively thin and thus allow the implementation of a compact saddle 10 only slightly extending past, or even not at all, the surface of the pylon 8 even if a sealing system 40 and a guiding member 46 can be integrated therein. The mechanical performance of the saddle can be optimized with the invention while remaining compact. It is possible for the saddle to not make any projection from the pylon 8, which is aesthetically pleasing.
The embodiments described above are a simple illustration of the present invention. Various modifications can be made to them without departing from the scope which results from the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 17 57264 | Jul 2017 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2018/051862 | 7/20/2018 | WO | 00 |
