EP1121492A1

EP1121492A1 - Guy cable deflector

Info

Publication number: EP1121492A1
Application number: EP99947576A
Authority: EP
Inventors: Louis Demilecamps; Cyrille Fargier; Etienne Rousselet
Original assignee: DUMEZ-GTM
Current assignee: Vinci Construction Grands Projets SAS
Priority date: 1998-10-16
Filing date: 1999-10-14
Publication date: 2001-08-08
Anticipated expiration: 2019-10-14
Also published as: JP2002527653A; KR100573995B1; AR020809A1; EP1121492B1; DE69909813D1; PE20000998A1; TW434353B; ATE245727T1; CA2346558A1; KR20010033161A; AU6097399A; JP4104826B2; WO2000023654A1

Abstract

The invention concerns a deflector (7) for guy cable (2) with n separate strands (3), comprising at least a body (14) with two opposite surfaces more or less perpendicular to a longitudinal axis (13) of the body and comprising n passages (8) passing through the body from one of its surface to the other and arranged in a grid system, and wherein each passage (8) has an internal diameter selected so as to define in use a radial clearance just sufficient for one cable (2) strand (3) to pass freely in the passage, the grid system formed by the passages (8) has, on the first of the two opposite surfaces of the body (14), a first mesh dimension (m1) and on the second surface of the body (14) a second mesh dimension (m2) larger than the first mesh dimension, and wherein except for the central passage located on the body (14) longitudinal axis, each passage extends between the first and second body surfaces along a curved path, and the passages (8) which are located at the grid system periphery and which have, among all the passages (8), the curved path with the smallest radius (min. R), have at every point of their path a curvature not greater than a predetermined maximum curvature, and the body (14) is made of a material capable of being formed with thickness levels less than 2 mm and having a compression strength higher than 20 Mpa and a tensile strength higher than 10 Mpa.

Description

GUIDE CABLE DEVIATOR

The present invention relates to a diverter for cable stays with n separate strands, of the type comprising at least one body which has two opposite faces at least approximately perpendicular to a longitudinal axis of the body, and which is pierced with n holes passing through the body. one face to the other thereof and arranged in a mesh network, each hole having an inside diameter corresponding to the outside diameter of a strand of the cable.

In a stay cable, the strands of the cable, seen in cross section, are usually arranged in the form of a mesh network, for example, a triangular mesh network. In the current part of the stay cable, that is to say in the part of the cable extending between two anchors located at the ends of the cable, the mesh should be as small and compact as possible so as to minimize the resistance of the cable in the wind and to reduce the cost of this current part, in particular the cost of the cable sheath and of the material injected into this sheath for the protection of the cable. However, at each anchorage, the strands must be separated from each other so that one can juxtapose the clamping jaws or sleeves which are used to individually attach the strands to the anchor head. A deflector is therefore usually provided which makes it possible to pass the strands from the wide mesh of the anchor head to the compact mesh of the current part of the stay cable.

At the level of the anchor head and at the level of the deflector, the strands must not undergo sudden angular deviation and must not touch each other in order to improve the fatigue behavior of the anchor. More generally, it is sought to limit as much as possible, or even eliminate, the strand-metal contacts because, in service, such contacts are liable to cause wear by small movements, what those skilled in the art call. "fretting corrosion".

A common technique therefore consists in subjecting each strand to a small angular deviation, which is generally less than 2 ° and usually about 1 °. by placing a deflector at a distance from the anchor head such that the deflection of the most deflected strands, i.e. those located at the periphery of the cable, is less than the angle indicated above . In the case of individually sheathed strands, the deflector is usually constituted by a device of the collar type, which clamps the sheathed strands together. The strands then touch by their individual sheath.

In the case of individually unsheathed strands, the deflector is usually constituted by a plastic disc, which is pierced with as many holes as there are strands, each strand passing through a respective hole in the disc and each hole having an axis parallel to the longitudinal axis of the stay cable.

This known deflection technique however has a number of drawbacks. In the case of unsheathed strands, when they are threaded, the strands must be guided from the anchoring head to the deflector, since these two parts are distant from each other and each strand must pass through two holes which correspond in the two parts, that is to say which have the same position in the mesh network. In addition, in all cases, that is to say whether the strands are sheathed or not, the deflector must be placed at a relatively large distance from the anchor head so that the total length of the area of anchoring more the deviation zone is itself important. As will be seen below, with a conventional deflector, the distance between the deflector and the anchor head can reach 3.4 m in the case of a cable composed of 61 strands of the type ^" T15S commonly used for cables of guy ropes, and about 2.6 m in the case of a cable made up of 37 strands. In addition, the coaxiality between the anchor head and the deflector must be guaranteed under penalty of introducing an additional angular deviation. Consequently, the deflector must be maintained by a rigid connection (possibly semi-rigid), which can be constituted for example, by a formwork tube in a pylon or by a tube embedded in a screed. This connection supports significant efforts to " the ultimate limit state ", which requires, in certain anchoring configurations, embedding of the connecting tube that is all the more complex as the deflector is placed far from the anchoring head.

For all the above reasons, it is desirable to reduce the distance between the deflector and the anchor head. One way to reduce this distance may be to reduce the distance between the adjacent strands in the anchor head, as is done in some anchoring methods in order to reduce the dimensions of the anchor head itself. However, reducing the distance between the strands adjacent, in other words the reduction in the size of the mesh of the mesh network formed by the strands in the anchoring head, is necessarily limited, on the one hand because of the presence of the clamping jaws or of the spun sleeves which serve to individually fix the strands on the anchor head and which must be able to be juxtaposed on the latter, and on the other hand because too close holes in the anchor head would weaken the latter and consequently adversely affect its mechanical strength. It therefore follows that this known solution allows only a limited reduction in the distance between the deflector and the anchoring head.

Cable anchoring systems are also known, in which each of the individual strands of the cable is made to follow a curved path either in a sort of deflector placed immediately before the anchoring head (s) (US - 4,473,915 and FR - 1.328.971), either in the structure of the concrete structure (US-4.442.646, figure 4), or even in the anchor head itself (US-4.442.646, figure 6, US - 4,484,425). In all of these known anchoring systems, which make it possible to substantially reduce the total length of the deflection and anchoring area of the cable strands, the said strands pass individually through curved guide tubes which are embedded in a concrete matrix. or in a cement grout.

In the anchoring systems known from patents US-4,473,915, US-4,442,646 and US-4,484,425, the guide tubes have an inside diameter substantially larger than the outside diameter of the individual strands. An epoxy resin, a mortar or a cement grout is injected so as to fill the empty spaces between each strand and the internal wall of the guide tube which surrounds it. With such a known arrangement, it is not possible to obtain a deflection of the strands such that the strands of the bundle of strands leaving the deflector, on the side of the current part of the cable, are arranged in a mesh network having a very small mesh size. This is due to the accumulation of the thicknesses of the different materials used in the manufacture of the deflector between any two adjacent strands of the cable, and to the fact that the concrete, the mortar and the cement grout are incapable of withstanding significant tensile forces when are used with small thicknesses.

More precisely, in the short anchoring and deflection systems described in the three aforementioned US patents, the minimum mesh size is the sum: . the inside diameter of the strand guide tubes,

. two wall thicknesses of these guide tubes,

. of a minimum thickness of the material coating the guide tubes and keeping them in position, that is to say a cement grout or a concrete according to the description of US Pat. No. 4,473,915.

For a cable made up of T15S strands. commonly used, the inside diameter of the guide tubes must be of the order of 22 mm to allow good injection of the residual space between the strand and the tube with a cement grout.

The thickness of the wall of the guide tubes depends of course on the nature of the material of which they are made and on their type; we can consider that this thickness is between 2 and 3 mm.

To withstand the pressure forces exerted by each strand on the wall of the material coating the guide tubes, due to the curvature and the tension of the strands, a value of 5 mm seems a minimum for the thickness of the concrete or grout. between two adjacent tubes.

By adding these values, it is found that the minimum value of the mesh of a cable formed according to US patent 4,473.15 is 31 mm.

The other known short anchoring and deflection systems and having similar characteristics (US 4,848,425, US 4,462,646, FR 1,328,971) lead to comparable values, and sometimes even higher. It is possible to affirm that with these known systems, it is not possible to obtain a mesh size less than a value close to 30 mm in the current part of the cable.

If we take for example two cables commonly used in guy lines, one of 37 strands T15S, the other of 61 strands T15S, both arranged in an equilateral triangular mesh around a central strand , we find that the first cable fits into a congestion circle of diameter 196 mm, while the second cable fits into a congestion circle of diameter 256 mm.

It follows that. in the current part of the cable, the overall cross section of the bundle of parallel strands forming the cable has a relatively diameter large, requiring the use of a cable protection sheath having itself a relatively large diameter adapted to that of the cable. This leads to a relatively expensive sheathed cable, because of the relatively large diameter sheath and because of the greater quantity of material which must be injected therein for the protection of the cable. In addition, in the case where the cable is a guy cable, it has a relatively high wind resistance because of the relatively large diameter of its sheath. Finally, because an epoxy resin, a mortar or a cement grout is injected into the guide tubes, the strands can no longer be extracted from said tubes after setting of the injected material. As a result, it is not possible to replace a strand by strand if necessary, and the cable must then be replaced in its entirety as well as at least part of its anchoring systems.

In the anchoring system known from the aforementioned patent FR-1,328,971, no material is injected into the guide tubes, so that, in service, the individual strands can slide freely in said tubes. This allows the strands to be re-tensioned later if they have lost some of their tension, and to replace one or more strands of the cable, strand by strand if necessary, without having to replace the entire cable and its anchors. However, in this latter known anchoring system, the strands of the bundle of strands exiting the deflector, on the side of the current part of the cable, are spaced transversely from one another by a relatively large distance relative to their mutual distance in the current part of the cable, in which the strands are much tighter as is desirable. This is obtained by placing a frustoconical ring or sleeve in front of the deflector which tightens the strands in the direction of the current part of the cable and, conversely, allows them to open out in the direction of their respective guide tubes in the deflector. The ring or frustoconical sleeve therefore also acts as a deflector and this known anchoring system therefore actually comprises two deflectors placed end to end.

Although the anchoring system known from patent FR-1,328.91 does not have the aforementioned drawbacks of the anchoring systems described in the three aforementioned US patents, it nevertheless has the drawback that the deflection of the strands must be ensured by two successive deflectors so that the cable and its protective sheath have a diameter as small as possible in the current part of the cable. In addition, with reference to FIG. 1 of patent FR-1,328,971, it can be seen that at least the strands located at the periphery of the cable undergo two relatively abrupt angular bending or deviations (> 5 °) respectively in the regions of the two end faces of the frustoconical sleeve. In addition, as the strands are not kept spaced from each other in the region of the smaller diameter end of the frustoconical sleeve. the relatively sudden bending which they undergo at this place causes them to come into contact with each other at least as regards the strands located in the peripheral layers of the cable. Due to these relatively sudden flexions and the resulting contacts between the strands located in said peripheral layers, as well as between the outermost strands of the cable and the smaller diameter end edge of the frustoconical sleeve and between the strands and the edge of the openings of the curved guide tubes, and because of the inevitable small displacements of the strands under the effect of the dynamic loads to which they are subjected in service, the strands are subject to fatigue and wear by small deflections ("fretting corrosion ") in the regions indicated above.

The present invention therefore aims to provide a deflector making it possible to obtain both a substantial reduction in the total length of the deflection and anchoring area of the strands of a stay cable, a mesh size as small as possible for the mesh network formed by the strands in the current part of the cable, and the possibility of replacing one or more strands of the cable, strand by strand, and while avoiding subjecting said strands to unacceptable localized angular deviations.

To this end, the invention provides a diverter for guy cable with n separate strands, comprising at least one body which has two opposite faces at least approximately perpendicular to a longitudinal axis of the body and which comprises n channels passing through the body of a facing each other and arranged in a mesh network, and in which each channel has an internal diameter chosen so as to define in service a radial clearance just sufficient for a strand of the cable to pass freely in the channel , the mesh network formed by the channels has, on a first of the two opposite faces of the body, a first dimension of mesh and on the second face of the body a second dimension of mesh larger than the first mesh size, and in which with the exception of a central channel located on the longitudinal axis of the body, each channel extends between the first and second faces of the body along a curved path, characterized in that the channels which are located at the periphery of the mesh network and which have. among all the channels, the curved path having the smallest radius of curvature, have at any point in their path a curvature at most equal to a predefined maximum curvature, and in that the body is made of a material capable of being form with thicknesses less than 2 mm and having a compressive strength greater than 20 MPa and a tensile strength greater than 10 MPa. The curved path of each channel of the deflector has a predefined curvature, constant or not constant, which is compatible with the mechanical resistance of the strand and its resistance to fatigue, and which makes it possible to pass the strands from the first dimension of mesh to the second dimension of mesh, respectively at the level of the first and second faces of the body of the deflector, over a length of deflection which, as will be seen later, is much less than that which is necessary with the conventional deflectors placed at a distance from the head anchor. For strands of type T15, T15S or T16, which are commonly used to form guy cables, the radius of curvature (min. Of R) of the deflector channels which are located at the periphery of the mesh network have a higher value or equal to 1 m, preferably greater than or equal to 2 m and less than or equal to 5 m, preferably less than or equal to 4 m, for example, the value (min. of R) is equal to 2.5 m.

Preferably, said first dimension of mesh (mi) has a value which satisfies the relationship:

in which Φ is the value of the internal diameter of the channels which itself satisfies the relation: φ + 0.4 mm <Φ <φ + 2 mm

in which φ is the value of the diameter of a strand of the cable.

In a first embodiment of the deflector according to the invention, usable with an anchoring head whose holes have axes parallel to the longitudinal axis of the cable, each curved path of the channels of the deflector comprises two parts successive curved in opposite directions, namely, starting from the first face of the body of the deflector, a first part having a concavity turned towards the outside of the body, followed by a second part having a concavity turned towards the inside of the body. In another embodiment of the deflector according to the invention, usable with an anchoring head whose holes have axes which converge towards the longitudinal axis of the cable, each curved path of the channels of the deflector is bent monotonously from the first to second face of the deflector body.

In both cases, the dimension of the mesh of the mesh network formed by the channels of the deflector on the second face of the latter (second dimension of mesh) can be chosen so as to correspond to the dimension of mesh of the holes of the head. anchor. Under these conditions, the diverter can be attached to the anchor head to form a very compact assembly. In addition, as each channel of the deflector adjoins a corresponding hole in the anchor head and forms with it a continuous path for the strand passing through them, threading the strands through the holes in the head. anchoring and the deflector channels is greatly facilitated and one can do without the guide tubes which, with certain known deflectors located at a distance from the anchor head, had to be provided between the deflector and the anchor head to guide the strands from one to the other of these two elements. In addition, in the deflector according to the invention, each strand is in contact with the interior surface of the corresponding channel of the deflector over a relatively long length compared to a conventional deflector. Because of this relatively large contact length, and because of the curved shape of the path followed by each strand in the deflector. each strand is subjected in service, when stretched, to a frictional force in the corresponding channel of the deflector. In the case where the strands are fixed to the anchoring head by means of clamping jaws, the frictional forces applied to the strands by the deflector make it possible to reduce the amplitude of the fatigue stresses undergone by the strands in the clamping jaws of the anchor head. In this respect, the diverter according to the invention therefore acts as a filter. Other characteristics and advantages of the invention will appear during the following detailed description of various exemplary embodiments of the diverter, given with reference to the appended drawings in which:

- Figure 1 is a view partly in elevation and partly in longitudinal section showing an anchoring for guy cable using a conventional deflector;

- Figures 2 and 3 are cross-sectional views respectively along lines A-A and B-B of Figure 1;

FIG. 4 is a diagram making it possible to explain the calculation of the length of the deflection zone which is necessary for deviating transversely by a predetermined quantity a strand of a cable in the case of the conventional deflector of FIG. 1:

- Figure 5 is a view similar to Figure 1 showing an anchor for stay cable using a deflector according to the invention, Figure 5 further showing a first form of the curved path of the channels of the deflector in the case where the holes of the anchor head have axes parallel to the longitudinal median axis of the cable;

- Figure 6 is a figure similar to Figure 5, also with a deflector according to the invention, showing a second form of the curved path of the channels of the deflector in the case where the holes of the anchor head have axes which converge towards the longitudinal median axis of the cable;

- Figure 7 is a diagram for explaining the calculation of the length of the deflection zone which is necessary to deviate transversely from said predetermined amount a strand of a cable in the case of the deflector of Figure 6;

- Figures 8 to 1 1 are views in side elevation, with cutaway, showing four concrete embodiments of a diverter according to the invention according to Figure 6.

Figure 1 shows a conventional anchor 1 for a multi-strand stay cable 2.

Although for reasons of simplification and clarity of FIG. 1. this only shows two strands 3, the stay cable 2 usually has a large number of strands, for example 37 strands 3 as shown in Figures 2 and 3. The anchor 1 comprises an anchor head 4, which is pierced with n holes 5 (37 holes in the example shown) in each of which the strands 3 of the stay cable 2 are individually anchored in a known manner, for example by means of keys or conical jaws 6, in which case the holes 5 are partly cylindrical and partly conical. The holes 5 of the anchor head 4 are arranged in an arrangement forming a mesh network, for example with an equilateral triangular mesh (FIG. 3), which has a given dimension of mesh, for example 33 mm in the case where one uses T15S strands of class 1770 or 1860 MPa (corresponding to a guaranteed breaking strength of 265,500 or 279,000 N) which have a diameter of 15.7 mm. The mesh size corresponds to the distance between the axes of any pair of adjacent holes.

The anchor 1 represented in FIG. 1 further comprises a deflector 7 pierced with n holes 8 (n = 37 in the example shown), which makes it possible to convert the arrangement of the strands 3 in the anchor head 4 into a arrangement forming a mesh network (FIG. 2) which has a smaller mesh size than that of the mesh network of the holes 5 of the anchor head 4, for example a mesh size of 18 mm, for the current part of the cable stay cable 2. The current part of the stay cable 2 is the part which extends between the anchor 1 shown in FIG. 1 and another anchor (not shown) situated at the other end of the stay cable 2, and which usually passes through a sheath 9 (only a very small part of this sheath is visible in Figure 1) constituted for example by a high density polyethylene (HDPE) tube.

The diverter 7. produced for example in HDPE, is fixed to one end of a metal tube 11, itself fixed or embedded in a part 12 of a bracing work. The tube 1 1 supports and maintains the deflector 7 at a predefined distance 1 | (Figure 4) of the anchor head 4. This distance li is usually chosen so that the angular deviation α produced by the deflector 7 remains less than or equal to a predefined value usually at 1 to 2 ° for all the strands 3 so that, in service, these are not subjected to excessive fatigue at the place where they exit from the deflector 7. that is to say at the outlet orifices of the holes 8 oriented towards the anchoring head 4, and possibly also where they enter the head anchor 4, that is to say at the inlet orifices of the holes 5 oriented towards the deflector 7 if the axes of the holes 5 are parallel to the longitudinal median axis 13 of the anchor 1.

Referring to Figure 4, if we denote by d the transverse offset undergone by any of the strands 3 of the cable 2 between the deflector 7 and the anchoring head 4, by ei the distance between the axis 13 and the axis of the hole 8 through which the strand 3 passes through the deflector 7, and by e ₂ the distance between the axis 13 and the axis of the hole 5 through which the strand passes through the anchoring head 4, the distance 1 | is then given by the following equation:

e-> -

(D tgα tgα

The distances ei and e ₂ are themselves given by the following equations:

e ₂ = rm ₂ (3) in which mi and m are respectively the mesh dimensions of the networks formed by the holes 8 and 5 respectively in the deflector 7 and in the anchoring head 4, and r is a number corresponding to the rank of the hole 8 or 5 considered with respect to the axis 13. From equations (1) to (3), the distance l _\ can be expressed by the following equation: r (m ₂ - ιτi |)

1. = (4) tgα

Since the strands 3 which undergo the greatest angular deviation α are those which are at the periphery of the mesh network of holes, in particular those which pass through the holes which are situated at the vertices of the hexagon formed by the network of holes and which have the highest rank (the rank 3 holes in the example shown in Figure 3), the distance 1 | must therefore be calculated for the holes with the highest rank. For a cable 2 of 37 strands of type T15S. with a mesh size mid of 18 mm, a mesh size m? 33 mm. an angular deviation α of 1 ° and a value of r equal to 3, we obtain a distance 1 | equal to 2.56 m. For a cable 2 of 61 strands, r is equal to 4 and with the same values of the parameters mi. m ₂ and α, we obtain for the distance for the distance 1 | worth 3.44 m. From the above, it can therefore be seen that, in the conventional anchor 1 shown in FIG. 1, the distance li must be relatively large. Thanks to the present invention, this distance can be considerably reduced as will now be seen.

Figure 5 shows an anchor 10 using a diverter 7 according to a first embodiment of the invention. The elements of the anchor 10 of FIG. 5 which are identical or which play the same role as those of the conventional anchor 1 of FIG. 1 are designated by the same reference numbers and will not be described again in detail. The deflector 7 of the anchor 10 of FIG. 5 is in the form of a body 14, for example cylindrical, which has an axial length greater than that of the deflector 7 of the conventional anchor 1 of FIG. 1, and which has as many channels 8 as there are strands 3 in the cable 2. Each channel 8 preferably has an internal diameter Φ which satisfies the relationship: φ + 0.4 mm ≤ Φ <φ + 2 mm in which φ is the outside diameter of a strand 3.

On the face of the body 14 oriented towards the sheath 9, the mesh network formed by the channels 8 of the deflector 7 of FIG. 5 has a first dimension of mid mesh which may be the same as that of the mesh network formed by the holes of the deflector 7 of FIGS. 1 and 2. On the opposite face of the body 14, which faces the anchoring head 4, the mesh network formed by the channels 8 of the deflector 7 of FIG. 5 has a second dimension of mesh m which is larger than the first mesh dimension mid and which is preferably equal to the mesh dimension of the network formed by the holes 5 of the anchor head 4. Under these conditions, the deflector 7 and the anchor head 4 can be joined together as shown in Figure 5.

With the exception of the central channel 8 of the deflector 7, which is located on the longitudinal axis of the body 14 and which is straight, all the other channels 8 of the deflector 7 of FIG. 5 extend between the two faces of the body 14 following a curved path, which has at all points a curvature more equal to a predefined maximum curvature. In this embodiment, the curved path of the channels located at the periphery of the mesh network have a greater curvature than that of the paths of the channels closer to the longitudinal axis of the body 14, while however remaining less than the predefined maximum curvature. As indicated above, this predefined maximum curvature is chosen so as to be compatible with the mechanical resistance of the strands 3 and with their resistance to fatigue. With strands 3 of the T15S type which are most commonly used for stay cables, the minimum radius of curvature of the curved path of the channels 8 is at least equal to 1 m, preferably at least equal to 2 m, for example equal at 2.5 m.

In the embodiment shown in Figure 5, in which the axes of the holes 5 of the anchor head 4 are parallel or substantially parallel to the longitudinal median axis 13 of the anchor 10, the curved path of each channel 8 of the deflector 7 has two successive parts curved in opposite directions. More precisely, starting from the face of the body 14 which is turned towards the sheath 9, each channel 8 has a curved path which comprises a first part whose concavity is turned radially towards the outside of the body 14, and a second part whose concavity is turned radially inward of said body 14, the two parts connecting to each other continuously.

In the embodiment shown in FIG. 5, the length of the deflection area of the strands 3 of the cable 2 is equal to the axial length of the body 14 of the deflector 7. If we compare FIGS. 1 and 5, in which the anchors 1 and 10 were drawn on the same scale, it can be seen that the length of the area of the deflection of the strands 3 in the anchor 10 is significantly shorter than the length of the zone of the deflection of the strands 3 in the conventional anchor 1, the length of the latter zone corresponding to the distance 1 |.

If an anchor head 4 having holes 5 is used whose axes converge towards the longitudinal median axis 13 of the anchor 10 in the direction of the deflector 7, as shown in FIG. 6, the length of the deflection zone of the strands 3, that is to say the length of the body 14 of the deflector 7, can be further reduced. In the embodiment of FIG. 6, with the exception of the central channel which has a straight path, the other channels 8 of the deflector 7 have a curved path which is curved monotonically from one of the end faces from the body 14 to its opposite end face, each curved path having a concavity oriented radially towards the outside of the body 14. Preferably, each curved path has the shape of an arc of a circle, that is to say that it has a constant curvature, without this constituting an imperative limitation of the invention. Indeed, each curved path could have a curvature which varies from an end face to the opposite end face of the body 14. provided, however, that at each point of each curved path the curvature remains less than the curvature predefined maximum mentioned above.

Referring to FIG. 7, which schematically illustrates the deflection of a strand 3 by the deflector 7 of FIG. 6 in the case where the curved path of the channels 8 has an arc shape, the length 1 ₂ of the deflector 7 is given by the following equation:

= R sinβ (5)

in which R is the radius of the circular arc of the curved path followed by the strand 3 in the deflector 7, and β is the angle at the center of said circular arc. In this case, the transverse offset d undergone by the strand 3 between the input and the output of the deflector 7 is given by the following equation:

in which ei represents the distance between the axis 13 and the center of the orifice of the channel 8, sheath side 9, and e ₂ represents the distance between the axis 13 and the center of the orifice of the channel 8. head side 4. Taking into account that the values of ei and e ₂ are again given by equations (2) and (3) indicated above, and that the sum of the squares of the sine and the cosine of the angle β is equal to 1, the length 1 of the deflector 7 is then given by the following equation:

1 ₂ = [2 r R (m ₂ - m,) - r ² (m ₂ - m,) ² ] ^{l 2} (7)

For a cable 2 composed of 37 strands 3 of the T15S type, assuming that the value of the radius R is chosen equal to 2.5 m and with the same values of r, mi and m? than those indicated above with regard to the conventional anchor 1 in FIG. 1, a value of 0.47 m is obtained for the length 1 of the deflector 7 of FIG. 6. For a stay cable 2 composed of 61 strands 3. on similarly, for the length 1 _2, a value of 0.54 m is obtained. To facilitate comparison between the anchor Conventional 1 in Figure 1 and the anchor according to the invention in Figure 6, the values of 1] and h are summarized in the following table:

As can be seen from the table above, for a cable of 37 strands, the length 1 ₂ of the diverter 7 according to the invention (Figure 6) is 5.4 times shorter than the length lι of the area of deviation from the conventional anchor 1 and, for a cable of 61 strands, the length 1 ₂ is 6.4 times shorter than the length 1 |. In the case of the embodiment of Figure 5, the length 1 of ₂ of the deflector 7 is approximately equal to twice that of the deflector 7 in Figure 6, the values obtained

in this case remaining, however, significantly lower than those of the length _\ .

7 with the diverter according to the invention, the length of the metal tube 11 which supports and keeps the deflector can be greatly reduced, since its length may be equal to length 1 ₂ of the deflector as shown in Figures 5 and 6. In two embodiments of FIGS. 5 and 6, the functions of the diverter 7 according to the invention are as follows:

- guide the strands 3. during their threading, from the current zone of the stay cable 2 in the sheath 9 where the strands 3 are arranged parallel to one another in a narrow mesh network, as far as the holes 5 of the head anchor 4, which are arranged in a relatively wide mesh network, or, vice versa, from the holes 5 of the anchor head 4 into the current area of the stay cable 2;

- impose on the stretched strands a curved path inside the deflector 7;

- And transfer the radial forces (created by the tension of the strands of the cable and the curvature of their path inside the deflector) to a fixed point of the structure to be braced, via the tube 1 1 , while being able to withstand the tensile and compressive forces to which the deflector is subjected in service due to the tension of the strands and the dynamic loads applied to the cables or transmitted by them. In addition, the deflector 7 according to ^the invention is designed so as not to generate likely to cause contacts, in use, a detrimental wear of the strands 3, by friction in small displacements, particularly where the strands 3 are not sheathed individually. For this purpose, the interior surface of each channel 8. at least in its zone where a strand 3 once stretched comes into contact with said interior surface, can be made up:

- a polymer or a resin, for example HDPE, an Epoxy resin, polyamides, polytetrafluroethylene (PTFE), etc. ;

- or a metal less hard than steel, and such that the oxidation or wear particles are not abrasive with respect to steel, preferably a more electropositive metal than steel, for example zinc or an aluminum alloy.

The matrix, that is to say the material of the body 14. can be constituted:

- of the same material as the surface of the channels 8, provided that this material has the required mechanical properties, in particular a mechanical strength sufficient to withstand the above-mentioned forces, in particular a compressive strength greater than 20 MPa and a tensile strength greater than 10 MPa (in the case of using resins for formal matrix body 14, the resins may contain suitable fillers such as silica particles or the zinc powder, _the size of silica particles or of zinc then being less than the quantity (sorting | - Φ) / 4);

- Or a material different from that which constitutes the surface of the channels 8, for example steel.

The diverter 7 according to the invention (Figure 5 or 6) can be manufactured in different ways, which will now be described with reference to Figures 8 to 11.

In the embodiment of Figure 8, the body 14 of the deflector 7 is made of a flowable and curable plastic. such as for example a resin possibly containing fillers or a resin-based mortar. The channels 8 are defined by cores, for example by curved tubes (not shown) and which respectively have predefined curvatures corresponding to the desired curvature of the path of each channel 8. The tubes can be made of plastic or metal. A sheet 15 of a metal which is less hard and more electropositive than the steel constituting the strands of the cable, is placed around each elongated tube or core serving to form each channel 8 and the tubes are placed inside a mold ( not shown), which can itself be formed in part by the tube 1 1 shown in FIG. 5 or 6. The sheet 15 can be for example made of zinc or aluminum alloy and it has for example a thickness of about 5/10 mm (this thickness has been greatly exaggerated in Figure 8 for clarity of the drawing).

The flowable and curable resin intended to form the body 14 is then cast or injected into the mold. The tubes serving as cores for molding are removed from the body 14 after it has been removed from the mold, while the sheets 15 remain in the channels 8 in order to double their internal surface.

In the embodiment of FIG. 9, the body 14 of the deflector 7 is produced by molding in the same manner as the embodiment of FIG. 8, except that, in this case, the channels 8 are not lined internally with '' a sheet or other metallic coating. In the embodiments of FIGS. 8 and 9, the cores used to form the channels 8 in the body 14 can have a skin and / or be coated with a material facilitating their removal from the body 14 after molding thereof.

In the embodiment of FIG. 10, each channel 8 is machined in the material of the body of the deflector 7, for example using a tool 16 in the form of a semi-diabolo, which has a curved profile corresponding to the desired curvature of the curved path of the channel 8. In this case, the deflector 7 is preferably constituted by several bodies, for example three bodies 14a, 14b. and 14c. drilled with n holes and arranged successively on the same longitudinal axis and preferably juxtaposed, the homologous holes of the three bodies 14a. 14b and 14c each time defining a continuous curved channel 8 for a strand 3 of the cable 2. Each hole or channel 8 of the intermediate body 14b, which has an axial length greater than that of the two end bodies 14a and 14c can be drilled at using ^the tool 16 from each of the two end faces of the intermediate member 14b, in such a way that the two holes thus formed meet in the middle of the intermediate body 14b. In this case, the shoulders which appear at the interfaces of the three bodies 14a, 14b and 14c, due to the differences in diameter of the holes 8 at these locations, can be cut down by milling, as shown in 17, so as not to hinder the threading of the strand in the aligned holes of the three bodies 14a-14c. These three bodies can be made of metal, preferably in a less hard and more electropositive metal than the steel constituting the strands, for example aluminum or an aluminum alloy. However, the three bodies 14a to 14c can also be made of steel, but in this case the surface of the channels 8 will preferably be lined with a layer of less hard material than the steel constituting the strands of the cable. If this layer is itself metallic, it may be deposited for example by an electrolytic deposition process or by any other suitable process. In the embodiment of Figure 1 1, the diverter 7 is obtained by a mixed method combining the methods described above. For example, the deflector 7 can be constituted by two juxtaposed bodies 14a and 14d. The body 14a, the holes 8 of which are closest to each other, may be made of metal or of thermoplastic material, for example a material chosen from the range of HDPE or polyamides 6. The body 14a can then be produced according to the machining technique by removal of material described with reference to FIG. 10, or according to a pressure injection technique. The body 14d can be produced according to the technique of molding a thermosetting plastic material described with reference to FIG. 8 or 9. With the deflector according to the invention, and when T15S strands are used, it is possible to adopt a mid mesh size as small as 18mm. For two cables consisting respectively of 37 and 61 strands, it is found that the first cable is part of a congestion circle with a diameter of 124 mm, while the second cable is part of a congestion circle with a diameter of 160 mm. The gain in size on the current section of the cable obtained thanks to the invention is therefore considerable, of the order of 37% in diameter, or 60% in section compared to cables provided with anchoring and deflection systems. described in US patents 4,442,646, 4,473,915 and 4,484,425.

It goes without saying that the embodiments of the present invention, which have been described above, have been given by way of purely indicative and in no way limiting example, and that numerous modifications can be made by those skilled in the art. art without departing from the scope of the invention. For example, it is not absolutely essential that the deflector 7 according to the invention be attached to the anchoring head 4, although this arrangement is particularly favorable from the point of view of the guidance of the strands 3 and from the point of view of the total length of the anchoring 10 In addition, in the case where the deflector 7 is composed of several successive bodies, these are not necessarily contiguous to each other, but they can be slightly spaced from each other, for example a few tens of centimeters. In addition, the body 14 or the bodies 14a to 14c are not necessarily cylindrical, but they can be frustoconical or partly cylindrical and partly frustoconical, or they can have a non-circular section, for example a polygonal section.

Nor is it essential that the curved path of each channel 8 have a constant curvature (arc of a circle) over its entire length. The curvature of each curved path can indeed vary over all or part of the length of the path, provided that at any point of said path the value (min. Of R) of the radius of curvature remains within the limits indicated above. Likewise, it is not essential that the curved path of the channels situated at the periphery of the mesh network have a greater curvature than that of the channels closer to the middle of said mesh network. Indeed, for example, with the exception of the central channel of the mesh network, each channel can have a curved path portion, with an identical curvature for all the channels, but different curved path lengths (the channels located at the periphery of the mesh network having the longest curved path portions, and the channels located near the middle of the mesh network having the shortest curved path portions), and a rectilinear path portion following the curved path portion.

In addition, if desired, the free spaces between each strand and the wall of the corresponding channel of the deflector can be filled with a corrosion protection agent such as, for example, a flexible visco-elastic resin, a petroleum wax, grease, or other flexible materials which do not hinder the possibility of replacing one or more strands, strand by strand.

Claims

1) Deflector for stay cable (2) with n separate strands (3), comprising at least one coφs (14) which has two opposite faces at least approximately perpendicular to a longitudinal axis (13) of the coφs and which comprises n channels ( 8) crossing the coφs from one face to the other of it and arranged in a mesh network, and in which each channel (8) has an internal diameter chosen so as to define in service a radial clearance just sufficient for that a strand (3) of the cable (2) can pass freely in the channel, the mesh network formed by the channels (8) has, on a first of the two opposite faces of the coφs (14), a first mesh dimension ( m _t ) and on the second face of the coφs (14) a second mesh dimension (m ₂ ) larger than the first mesh dimension, and in which with the exception of a central channel located on the longitudinal axis of the coφs (14), each channel (8) extends between the first and second faces of the coφs following a curved path, characterized in that the channels (8) which are located at the periphery of the mesh network and which have, among all the channels (8), the curved path having the smallest radius of curvature (min. of R), have at any point of their path a curvature at most equal to a predefined maximum curvature, and in that the coφs (14) is made of a material capable of being shaped with thicknesses less than 2 mm and having a compressive strength greater than 20 MPa and a tensile strength greater than 10 MPa.

2) Deflector according to claim 1, characterized in that said smallest radius of curvature has a value (min. of R) which satisfies the relationship:

1 m < (min. of R) < 5 m.

3) Deflector according to claim 1, characterized in that said smallest radius of curvature (min. of R) satisfies the relationship:

2 m < (min. of R) < 4 m.

4) Deflector according to any one of claims 1 to 3, characterized in that said first mesh dimension (mi) has a value which satisfies the relationship: Φ + 1.5 mm < mi < Φ + 5 mm in which Φ is the value of the internal diameter of the channels (8) which itself satisfies the relation: φ + 0.4 mm < Φ < φ + 2 mm in which φ is the value of the diameter of a strand (3) of the cable (2).

5) Deflector according to any one of claims 1 to 4. characterized in that the coφs (14) is made of a castable and hardenable resin, which is cast or injected into a mold, and in that the channels (8) are defined by elongated and curved cores, which respectively have predefined curvatures and which are embedded in the material of the body (14) during molding and removed from the coφs after its demolding.

6) Deflector according to claim 5, characterized in that the resin contains a filler.

7) Deflector according to claim 6, characterized in that the filler consists of silica particles or zinc powder, the silica or zinc particles having a size less than the quantity (mi - Φ)/4.

8) Deflector according to any one of claims 5 to 7, characterized in that the interior surface of each channel (8), at least in its zone where a strand (3) once stretched comes into contact with said interior surface, is lined with a sheet (15) of a metal less hard and more electropositive than steel, said sheet being placed around the elongated core used to form the corresponding channel and being left in place in said channel after molding of the coφs ( 14) and removal of said elongated core.

9) Deflector according to claim 8, characterized in that said metal sheet is made of zinc or aluminum alloy and has a thickness of approximately 5/10 mm.

10) Deflector according to any one of claims 1 to 4, characterized in that the channels (8) are machined in the material of the coφs (14).

11) Deflector according to claim 10, characterized in that the coφs (14) is made of a metal that is less hard and more electropositive than the steel constituting the strands (3) of the cable (2).

12) Deflector according to claim 10, characterized in that the body (14) is made of steel and in that the interior surface of the channels (8) is lined ^with a layer of material less hard than the steel constituting the strands ( 3) of the cable (2).

13) Deflector according to any one of claims 1 to 12, characterized in that it comprises several coφs (14a- 14c) pierced with n holes and arranged successively on the same longitudinal axis (13).

14) Deflector according to claim 13, characterized in that the coφs (14a- 14c) are two by two in contact and their corresponding holes define each time a continuous curved channel (8) for a strand (3) of the cable (2 ). 15) Deflector according to claim 14, characterized in that a first coφs

(14a) of the coφs (14a and 14d) is made of metal and its holes are made by machining, and in that a second (14d) of the bodies (14a and 14d) is made by molding a plastic material.

16) Deflector according to claim 14, characterized in that a first coφs (14a) of the coφs (14a and 14d) is made of thermoplastic material and is produced by one of the two techniques including pressure injection and machining by removal of material, and in that a second (14d) of the coφs (14a and 14d) is produced by molding a thermosetting plastic material.

17) Deflector according to any one of claims 1 to 16, characterized in that it further comprises a holding tube (11), of the same length as the coφs

(14), which closely surrounds said coφs and which serves to fix it on a structure (12) to which the stay cable (2) is anchored.

18) Deflector according to one of claims 1 to 17, characterized in that each channel (8) has a curved path which comprises two successive parts curved in opposite directions, namely, starting from the first face of the coφs (14), a first part having a concavity facing the outside of the body, followed by a second part having a concavity facing the inside of the body.

19) Deflector according to any one of claims 1 to 17, characterized in that each channel (8) has a path which is curved monotonically from the first to the second face of the body (14). 20) Deflector according to claim 19 characterized in that each curved path has the shape of an arc of a circle.

21) Device for anchoring a multi-strand stay cable, comprising an anchoring head (4) which has n holes (5) in each of which the strands (3) of the stay cable (2) are anchored individually , and which are arranged in an arrangement forming a mesh network which has a given mesh size, and a deflector (7) making it possible to convert the arrangement of the strands (3) in the anchoring head (4) into an arrangement forming a mesh network which has a mesh size smaller than said given mesh size, for a current part of said cable (2), characterized in that the deflector (7) is a deflector according to any one of claims 1 to 20.

22) Stay comprising a cable (2) composed of several separate strands (3), and two anchoring devices (1) located at the ends of the cable, characterized in that at least one of the two anchoring devices (1 ) is an anchoring device according to claim 21.