EP1606456A1

EP1606456A1 - Construction cable

Info

Publication number: EP1606456A1
Application number: EP03740531A
Authority: EP
Inventors: Benoít Lecinq; Jean-Pierre Messein
Original assignee: Freyssinet SAS
Current assignee: Soletanche Freyssinet SA
Priority date: 2003-03-24
Filing date: 2003-03-24
Publication date: 2005-12-21
Anticipated expiration: 2023-03-24
Also published as: ES2338779T3; JP4335151B2; DE60331372D1; SI1606456T1; ATE458089T1; WO2004094730A1; AU2003304059A1; US7124460B2; JP2006514179A; PT1606456E; EP1606456B1; US20050252675A1

Abstract

The cable, in particular of the stay cable type, comprises a set of traction reinforcements, two devices for anchoring the reinforcements in two respective zones of the construction, the reinforcements being spaced apart from one another at the anchoring devices, means for deviating the reinforcements in order to cause the reinforcements to converge toward a running part of the cable into a substantially parallel bundle which is more compact than at the anchoring devices, and a guide member which is in closely set contact around the set of reinforcements. This member has an inner surface, the cross section of which is adapted to the peripheral shape of the parallel bundle and the longitudinal section of which has a convex curvature which, over the length of the guide member, allows angular deflections of the reinforcements which are substantially greater than the maximum angle of convergence of the reinforcements between the anchoring device and the running part of the cable.

Description

CABLE OF STRUCTURE OF ART WORK

The present invention relates to the field of cables used in construction to participate in the structure of certain structures.

It relates more particularly to arrangements of such cables which give them good properties in case of earthquake.

The invention is particularly applicable to stays used to suspend portions of work such as bridge decks. In a current embodiment, such a stay includes a beam of parallel reinforcements extending between two anchoring zones, one on a pylon of the structure, and the other on the suspended part. In the anchoring zone, the individual reinforcements of the stay have a slight divergence in order to be able to block them individually.

When a cable-stayed structure undergoes an earthquake, the suspended part, for example the bridge deck, undergoes abrupt and potentially important displacements with respect to the pylons. This results in high tensile and flexural variations in the shrouds.

The bending stresses are reflected in the anchoring zones, and may damage the reinforcement and / or the anchoring devices.

WO 00/75453 discloses an anchoring device for a structural cable such as a stay, provided with guide means comprising an individual guide duct for each armature, this duct flaring towards the running portion of the cable so as to allow angular deflection of the armature. This anchoring device has the advantage of ensuring a gradual recovery of the bending forces due to the convergence of the reinforcements towards the current part, or certain transverse actions undergone by the stay. But this recovery of effort may prove insufficient in the presence of sudden stress variations suffered in the event of an earthquake.

An object of the present invention is to propose an arrangement allowing the structural cables and the structures of which they form part of withstand the heavy demands that occur in the event of an earthquake.

The invention thus proposes a structure structure cable, comprising:

- a set of tensile plates; two reinforcing anchoring devices in two respective zones of the structure, the reinforcements being mutually spaced at the anchoring devices; and

means for deflecting the reinforcements to make the reinforcements converge towards a running portion of the cable in a substantially parallel beam that is more compact than at the level of the anchoring devices.

According to the invention, the structural cable comprises at least one guide member in close contact around the armature assembly, having an inner surface whose cross section is adapted to the peripheral shape of the parallel beam and whose longitudinal section has a convex curvature which, over the length of the guide member, admits angular deflections of the reinforcements substantially greater than the maximum angle of convergence of the reinforcements between the anchoring device and the current part of the cable.

The shape of the guide member allows it to absorb strong angular deflections of the armature assembly, with a controlled radius of curvature to avoid damaging the reinforcements and the anchoring device.

In preferred embodiments of the cable according to the invention:

the angular deflections admitted by the guide member are at least 100 milliradians; the angular deflections admitted by the guiding member are at least double the maximum angle of convergence of the reinforcements between the anchoring device and the current part of the cable;

the radius of curvature of the longitudinal section of the internal surface of the guide member is at least 3 meters in the portion where this member is in close contact around the set of reinforcements; - The radius of curvature of the longitudinal section of the inner surface of the guide member decreases from the portion where the member is in close contact around the set of reinforcements to the current portion of the cable; - The guide member is mounted with a transverse movement capacity relative to one of the anchoring devices;

means for damping transverse vibrations of the reinforcement bundle with respect to one of the anchoring devices are provided, and the guiding member is placed on the set of reinforcement between the damping means and said device anchor;

- The guide member is mounted with limited transverse movement capacity relative to said anchoring device so as to provide a determined stroke damping means;

- The anchoring device bears longitudinally against a tube connected to the structure of a portion of the structure and through which the reinforcements, the damping means comprise a damper arranged between the bundle of reinforcements and a support mounted to the end of said tube opposite to the anchoring device, and the mounting of the support at the end of the tube is effected by a link adapted to break when it is subjected to a force exceeding a predefined threshold;

the deflection means comprise a collar clamped around the set of reinforcements at a distance from an anchoring device, and in which the guide member is placed on the set of reinforcements between said collar and said device anchor; inserts are housed with the reinforcements in the guide member so as to maintain a spacing between the reinforcements inside the guide member;

said inserts comprise plastic sleeves placed individually around the reinforcements inside the guiding member, the internal surface of the guiding member preferably having a hexagonal cross-section; - The guide member belongs to the deflection means, helping to converge the armatures to the current part of the cable;

- The guide member comprises a plastic resin body molded around a metal reinforcing tube, this plastic resin may in particular be a polyurethane resin.

Another aspect of the present invention relates to a guide member for a structural cable as defined above. This member has a tubular general shape with an inner surface to be applied in close contact around a set of tensile reinforcements, the set of reinforcements converging between an anchoring device and a running part of the cable where the reinforcements are gathered in a parallel beam more compact than at the anchoring device, said inner surface having a cross section adapted to the peripheral shape of said beam and a longitudinal section having a convex curvature which, along the length of the guidance, admits angular deflections of the reinforcements substantially greater than the maximum convergence angle of the reinforcements between the anchoring device and the current part of the cable. Said inner surface preferably has a hexagonal or circular cross section.

Other features and advantages of the present invention will appear in the following description of a nonlimiting exemplary embodiment, with reference to the accompanying drawings, in which:

- Figure 1 is a schematic side view of a cable-stayed bridge to which the invention can be applied;

- Figure 2 is a schematic longitudinal sectional view of a portion of a guy according to the invention; and

- Figures 3 to 5 are cross-sectional views of the stay, respectively taken along the planes III-III, IV-IV and V-V shown in Figure 2.

The invention is described below, without being limiting, in the case of a structural cable consisting of a bridge stay.

A cable-stayed bridge is schematically illustrated in Figure 1. The deck 1 of the bridge is supported by sheets of guy 2 at one or more pylons 3 erected in the area crossed by the bridge. Each stay 2 follows a determined path between a low anchoring device 4 mounted on the deck 1 and a high anchoring device 5 mounted on the tower 3.

FIG. 2 shows in more detail the structure of the stay in the area of the deck where the anchoring device 4 is located.

The stay 2 comprises a set of traction plates 10 constituted, in the example in question, by metal strands each coated with an individual sheath of plastic material. In the current part of the stay, extending over most of its path between the deck and the pylon, the strands 10 are gathered in a compact parallel beam. The transverse disposition of the strands 10 in the running part is for example that illustrated in FIG. 5, where the compactness is maximal since the strands, of circular outer shape, are in contact with each other in a hexagonal mesh.

To form this compact bundle of strands, a deflector collar 11 disposed remote from the anchor 4 is clamped around the set of strands to make them converge.

The anchoring device 4 comprises a metal block 15 shown in cross section in FIG. 3. The block 15 is traversed by parallel orifices 16, cylindrical towards the current portion of the stay and frustoconical towards the opposite direction. Each orifice 16 receives a strand strand and an anchor jaw constituted by several wedges in the form of truncated cone sector. The orifices 16 have a certain spacing between them in order to have room for housing the anchoring jaws and to obtain a sufficiently robust block. The transverse mesh of these orifices is homothetic of that of the strands in the current part of the cable. This is why the strands converge from the anchoring device 4 to the current part.

The individual sheath of the strands 10 is interrupted in a chamber 17 at the rear of the anchor block 15. The residual interstices of the block and the chamber

17 are filled with a corrosion protection material such as a fat. A sealing system 18, for example of the stuffing-box type as described in the European patent 0 323,285, closes the chamber 17 opposite the block 15 by sealing around the individual sheaths of the strands 10. anchoring 4 may further comprise individual guide ducts of the strands, as described in WO 00/75453, flaring towards the running portion of the cable so as to allow angular deflection of the individual strands.

The anchoring device 4 bears longitudinally against a tube 20 connected to the structure of the deck 1 or the pylon 3 in order to transmit the tensile force of the stay.

The stay shown in FIG. 2 is equipped with a vibration damping device 21, which is on the deck side at a distance (a few meters) from the anchoring device 4. This device 21 serves to damp the transverse vibrations of the stay 2 relative to the tube 20 and the anchoring device 4, due to dynamic variations, load related to traffic on the bridge or aerodynamic forces. It is for example of the type described in European Patent 0 914521, with an annular chamber between the deflector collar 11 and a support tube 22 fixed to the end of the tube 20, this chamber containing a viscous material providing the damping effect. Alternatively, the viscous damping device could be mounted on an arm extending transversely between the stay and the deck 1 (see European Patent 0 343 054).

The stay thus equipped has a certain capacity to admit overall displacements of the strands with respect to the structure. The lever arm between the exit of the anchoring device 4 and the collar 11 gives a certain transverse travel to the damper 21, which allows angular movements, preferably in connection with the individual guide ducts of the strands present at the exit anchoring. These angular movements have a limited amplitude, typically about 25 milliradians. Larger deflections could damage the strands by imposing too much curvature on the anchor. However, the angular deflections occurring in the event of an earthquake can be much greater. However, in order to confer seismic properties on the stay cable according to the invention, a guide member 30 is installed between the anchoring device 4 and the collar 11 before setting up the strands 10.

This guide member 30 is of generally cylindrical shape. As shown in FIGS. 2 and 4, it may consist of a plastic resin body molded around a reinforcing tube of steel 31. The molded plastics material is advantageously a polyurethane resin, which has the advantages of being easily moldable, which allows the member 30 to be shaped accurately, to have excellent mechanical strength properties (hardness, resistance to shear and tensile stresses), and to behave well in environments aggressive sailors.

The inner surface 32 of the guide member 30 is in close contact around the strands once they are installed. The cross section of this inner surface 32, visible in FIG. 4, is adapted to the peripheral shape of the bundle of parallel strands. In the example shown, it is a hexagonal section which circumscribes the strands assembled in hexagonal mesh. When the strands thus assembled are in a number equal to 1 + 3n. (N + 1), that is to say 7, 19, 37, 61, etc., the compact beam has a hexagonal outer profile, corresponding to n full concentric layers around a central strand. If the number of strands intended to support the load of the stay is not one of these values, as it is the case in the drawn example where the stay has 43 strands (figure 5), the bundle is completed by dummy strands 12 at the deflection member 30. These dummy strands 12 may extend to the collar 11 beyond which they are interrupted. They are not anchored in the device 4. In the example considered, there are 61 - 43 = 18 dummy strands 12, represented in black in FIG. 4.

Since the member 30 is located at an intermediate position between the anchor 4 and the collar 11, the strands 10 have at its level a gap corresponding to a fraction of that which they have in the anchor block 15. To position them accurately by ensuring a good support on the guide member 30 and to prevent them from disorganizing in case of sudden bending stresses, inserts are housed inside the member 30 with all of the strands 10, 12. These inserts may consist of individual plastic sleeves 13 into which the part of the strands 10, 12 is threaded. through a member 30. A stop plate 35 is placed on the back of the anchoring device 4 to prevent this device being disturbed by the ends of the sleeves 13 or dummy strands 12.

I

If it is not required that the strands have maximum compactness in the current portion of the stay, the cross section of the inner surface 32 of the guide member 30 may also be circular.

The longitudinal section of the inner surface 32 of the member 30 is shown in FIG. 2. It has a convex curvature which, along the length L of the guide member 30, admits substantially greater angular deflections of the reinforcements (typically minus two times greater) than the maximum convergence angle of the strands 10 between the anchor 4 and the current part of the stay. These admitted angular deflexions are, for example, up to α = 100 milliradians or more, while the maximum convergence angle, that is to say that of the peripheral strands, is of the order of 25 milliradians.

This recovery of large angular deflections is performed with a controlled radius of curvature to avoid excessive stresses bending strands out of the anchor. This radius of curvature R of the longitudinal section of the inner surface 32 of the member 30 is advantageously at least 3 meters in the rear portion of the member where it is in close contact around the set of strands. In an embodiment with strands with a diameter of 15.7 mm, the radius of curvature R in this rear portion will typically be 4 meters.

This radius of curvature R can be constant over the length L of the member 30. In this case, the angular deflection in radians admitted by the member 30 is α ≈ tg α = L / R. The length L can thus be of the order of 40 cm for R = 4 m and α = 100 milliradians

To reduce the bulk of the guide member 30, it is possible to forming its inner surface 32 so that the radius of curvature of its longitudinal section decreases going from the rear portion where the member is in close contact around the strands 10 towards the current part of the stay. This is possible without much risk of damage to the strands since the largest angular deflections in the event of an earthquake tend to occur when the axial stress is not very strong on the stay: it can then be assumed that a strand less axially stressed follows a curvature a little tighter. The smallest radius of curvature at the front end of the member 30 is for example of the order of 2.5 meters.

In a particularly advantageous embodiment, the guide member 30 is mounted floating relative to the anchor 4. It can thus be seen in FIG. 2 that the member 30 has a transverse movement capacity with respect to the tube 20 and the device. Anchoring 4. This avoids reducing the stroke available for the operation of the damper 21 and thus to degrade its dynamic behavior. This transverse movement capacity of the guide member 30 is limited so as to provide a determined travel of the damper 21.

The floating guide member 30 is in principle held longitudinally because it is in close contact around the set of strands. To avoid, however, that it undergoes significant displacements, it can be extended axially by spacers 33, 34, for example of tubular shape, which respectively abut against the damper 21 and the stop plate 35 in case of longitudinal movements .

An earthquake causes sudden variations in bending moment in the anchoring zones of the stays. These sudden variations are poorly filtered by the damper 21. This may result in serious deterioration of the anchoring zone, including the tube 20, requiring heavy repairs with disassembly of the anchor or the stay. To limit this risk, it is advantageously provided that the connection between the tube 20 and the support 22 of the damper is adapted to break when it is subjected to a force exceeding a predefined threshold. In the example shown in Figure 2, this connection is provided by bolts 40 which axially clamp flanges 38, 39 respectively formed at the ends vis-à-vis the tube 20 and the support 22. The diameter of these bolts 40 is selected so that they break before the transverse force reaches 4% of the axial force, which limits the bending moment transferred to the tube 20 and allows operation of the guide member 30 under optimal conditions.

The possible rupture of these bolts 40 is relatively benign because they are easily replaced.

It will be understood that the embodiment which has just been described does not limit the scope of the invention and that many variations can be made thereto. In particular, a guide member 30 as described above may be placed at a high anchor towards the pylon. It can also be put in place without there is a vibration damping device on the stay.

On the other hand, the guide member 30 may belong to the deflection means reinforcements which converge in a compact beam. It can in particular replace the collar 11 shown in Figure 2 if the constraints of space in the anchoring zone allow.

Claims

EVENDICATI

1. Structural structure cable, comprising:

- a set of traction armatures (10);

- two devices (4, 5) for anchoring the reinforcements in two respective zones of the structure, the reinforcements being mutually spaced at the level of the anchoring devices; and

^' - means (11) for deflecting the reinforcements to make the reinforcements converge towards a running part of the cable in a substantially parallel bundle more compact than at the level of the anchoring devices, characterized in that it comprises at least one member guide (30) in closely set contact around the set of reinforcements, having an inner surface (32) whose cross section is adapted to the ^one peripheral shape of the parallel bundle and the longitudinal section of which has a convex curvature which, on the length (L) of the guide member, allows angular deflections of the reinforcements substantially greater than the maximum angle of convergence of the reinforcements between the anchoring device and the current part of the cable.

2. Structural cable according to claim 1, in which the angular deflections admitted by the guide member (30) are at least double the maximum angle of convergence of the reinforcements (10) between the anchoring device (4) and the current part of the cable.

3. Structural cable according to claim 1, wherein the angular deflections admitted by the guide member (30) are at least 100 milliradians.

4. Structural cable according to any one of the preceding claims, in which the radius of curvature of the longitudinal section of the internal surface (32) of the guide member (30) is at least 3 meters in the portion where this member is in tight contact around the set of frames (10).

5. The structural cable according to claim 4, in which the radius of curvature of the longitudinal section of the internal surface (32) of the guide member (30) decreases from the portion where the member is in tight contact. around the set of reinforcements (10) towards the current part of the cable.

6. Structural cable according to any one of the preceding claims, in which the guide member (30) is mounted with a capacity for transverse movement relative to one of the anchoring devices (4).

7. Structural cable according to any one of the preceding claims, further comprising means (21) for damping transverse vibrations of the armature bundle (10) relative to one of the anchoring devices (4), and wherein the guide member (30) is placed on the set of frames between the damping means and said anchoring device.

8. structural cable according to claim 7, wherein the guide member (30) is mounted with a limited transverse movement capacity relative to said anchoring device (4) so as to provide a determined stroke of the means of depreciation (21).

9. A structural cable according to claim 7 or 8, in which the anchoring device (4) bears longitudinally against a tube (20) connected to the structure of a part (1) of the structure and crossed by the reinforcements (10), in which the damping means comprise a damper (21) disposed between the bundle of reinforcements and a support (22) mounted at the end of said tube opposite the anchoring device, and in which the mounting support at the end of the tube is effected by a link (40) adapted to rupture when it is subjected to a force exceeding a predefined threshold.

10. Structural cable according to any one of the preceding claims, in which the deflection means comprise a collar (11) tightened around the set of reinforcements (10) at a distance from an anchoring device (4) , and wherein the guide member (30) is placed on the set of frames between said collar and said anchoring device.

11. A structural cable according to claim 10, in which inserts (13) are housed with the armatures (10) in the guide member (30) so as to maintain a spacing between the armatures inside the guide member.

12. A structural cable according to claim 11, in which said inserts comprise plastic sheaths (13) placed individually around the frames (10) inside the guide member (30).

13. A structural cable according to claim 12, wherein the inner surface (32) of the guide member (30) has a hexagonal cross section.

14. Structural cable according to any one of the preceding claims, in which the guide member (30) belongs to the deflection means, helping to make the reinforcements (10) converge towards the current part of the cable.

15. A structural cable according to any one of the preceding claims, in which the guide member (30) comprises a body of plastic resin molded around a metal reinforcing tube (31).

16. A structural cable according to claim 15, in which the plastic resin is a polyurethane resin.

17. Guide member for a structural cable according to any one of the preceding claims, this member (30) having a shape. general tubular with an internal surface (32) to be applied in close contact around a set of traction reinforcements (10), the set of reinforcements converging between an anchoring device (4) and a running part of the cable where the reinforcements are gathered in a more compact parallel beam than at the level of the anchoring device, said internal surface having a cross section adapted to the peripheral shape of said beam and a longitudinal section having a convex curvature which, over the length (L ) of the guide member, admits angular deflections of the armatures substantially greater than the maximum angle of convergence of the armatures between the anchoring device and the running part of the cable.

18, A guide member according to claim 17, wherein said accepted angular deflections are at least double the maximum angle of convergence of the reinforcements (10) between the anchoring device (4) and the current part of the cable.

19. Guide member according to claim 17 or 18, wherein said angular deflections allowed are at least 100 milliradians.

20. Guide member according to any one of claims 17 to

19, in which the radius of curvature of the longitudinal section of said internal surface (32) is at least 3 meters in the portion where the member (30) is in close contact around the set of reinforcements (10 ).

21. Guide member according to any one of claims 17 to

20, in which the radius of curvature of the longitudinal section of said internal surface (32) decreases from the portion where the member (30) is in close contact around the set of reinforcements (10) towards the part cable current.

22. Guide member according to any one of claims 17 to

21, wherein said inner surface (32) has a hexagonal or circular cross section.

23. Guide member according to any one of claims 17 to 22, comprising a plastic resin body molded around a metal reinforcement tube (31).

24. Guide member according to claim 23, in which the plastic resin is a polyurethane resin.

ARTICLE 19

PCTYFR03 / 00921

AMENDED CLAIMS received by the International Bureau on March 22, 2004 (22.03.2004) original claims 1-24 are replaced by amended claims 1 to 16 (3 pages)