EP1887139A1 - Method of removing a tight cable, associated system and devices - Google Patents

Abstract

The method involves extending a cable (1) in a manner that a part of the cable is liberated from anchoring points. The part is liberated from another part of the points. The part is supported and evacuated remote from the anchoring points, where the part is sectioned during its evacuation. The part is supported using a support (18) arranged to raise the part and is maintained using a crane or scaffolding tower type auxiliary structure. An independent claim is also included for a system for dismounting a cable stretched between anchoring points on a structure.

Description

The present invention relates to the dismantling of a cable stretched between two anchor points on a structure.

Such disassembly is often considered problematic, especially when no specific device has been provided during the initial design of the structure in which the cable participates.

First, the fact that the cable is stretched between anchor points prevents it from simply releasing it from the structure.

Then, even once the cable has been released from the structure, it is still likely to damage the structure. If the structure is in use, as in the case of a bridge whose apron is subjected to traffic for example, disassembly of the cable may also cause a relatively long service interruption.

An object of the present invention is to allow easier cable disassembly.

• libérer une partie courante du câble desdits premier et deuxième points d'ancrage;
• supporter ladite partie courante du câble ; et
• évacuer ladite partie courante du câble à distance d'un au moins desdits premier et deuxième points d'ancrage.

The invention thus proposes a method of disassembling a cable stretched between a first and a second anchorage point on a structure comprising the following steps:

• releasing a running portion of the cable from said first and second anchor points;
• supporting said current portion of the cable; and
• discharging said current portion of the cable away from at least one of said first and second anchor points.

According to this method, the support and the evacuation of said current part of the cable are carried out using a plurality of supports distributed along said current part of the cable and forming cradles for said current portion of the cable, maintained each by at least one other cable located higher than said cable, the cradles being connected to each other and being mounted so as to be able to move along said other cable.

Advantageously, the release of the current portion of the cable of said first and second anchor points comprises a release of the cable so that the current portion of the cable is released from one of said first and second anchor points and a release of said portion cable of the other of said first and second anchor points.

Such pre-tensioning of the cable makes it possible to release a large part of it, without endangering the immediate environment of the cable, and the support of the current part of the cable also makes it possible to avoid damaging the structure to which the cable participates.

• une pluralité de berceaux aptes à être répartis le long d'une partie courante du câble pour constituer des appuis pour ladite partie courante du câble ;
• des moyens pour que chaque berceau de la pluralité repose sur au moins un autre câble situé plus haut que ledit câble et puisse se déplacer le long dudit autre câble ; et
• des moyens reliant les berceaux les uns aux autres.

The invention also proposes a support device for a cable stretched between a first and a second anchoring point on a structure. This support device comprises:

• a plurality of cradles adapted to be distributed along a current portion of the cable to form supports for said current portion of the cable;
• means for each cradle of the plurality to rest on at least one other cable located higher than said cable and to move along said other cable; and
• means connecting the cradles to each other.

• une pluralité de berceaux aptes à être répartis le long d'une partie courante du câble pour constituer des appuis pour ladite partie courante du câble ;
• des moyens pour que chaque berceau de la pluralité repose sur au moins un autre câble situé plus haut que ledit câble et puisse se déplacer le long dudit autre câble ; et
• des moyens reliant les berceaux les uns aux autres,

et un dispositif de pontage pour détendre le câble tendu, le dispositif de pontage comprenant :

• deux colliers aptes à être positionnés autour du câble de façon à assurer un contact sensiblement sans glissement le long du câble ;
• des barres de traction reliant lesdits colliers ;
• des moyens de réglage de l'effort de traction transitant dans les barres de traction ; et
• des moyens de surveillance de l'effort de traction transitant dans les barres de traction.

The invention further proposes a system for dismounting a cable stretched between a first and a second anchor point on a structure. This system includes a support device comprising:

• a plurality of cradles adapted to be distributed along a current portion of the cable to form supports for said current portion of the cable;
• means for each cradle of the plurality to rest on at least one other cable located higher than said cable and to move along said other cable; and
• means connecting the cradles to each other,

and a bridging device for expanding the tensioned cable, the bridging device comprising:

• two collars adapted to be positioned around the cable so as to ensure a substantially non-slip contact along the cable;
• pull bars connecting said collars;
• means for adjusting the traction force transiting the traction bars; and
• means for monitoring the traction force passing through the drawbars.

• la figure 1 est un schéma représentant un exemple de câble tendu à démonter ;
• la figure 2 est un schéma illustrant des dispositifs de pontage utilisés pour détendre le câble de la figure 1 ;
• les figures 3 à 5 sont des schémas montrant des étapes successives de la détension d'un câble selon un mode de réalisation avantageux de l'invention ;
• la figure 6 est un schéma montrant un mode de support du câble de la figure 1 une fois détendu ;
• la figure 7 est un schéma montrant un autre mode de support du câble de la figure 1 une fois détendu ;
• la figure 8 est une vue transversale d'une partie du dispositif d'appui utilisé selon le mode de support de la figure 7 ;
• la figure 9 est un schéma montrant une étape intermédiaire de l'évacuation du câble de la figure 1 selon un mode de réalisation avantageux de l'invention.

Other features and advantages of the present invention will become apparent in the following description of nonlimiting exemplary embodiments, with reference to the appended drawings, in which:

• Figure 1 is a diagram showing an example of tensioned cable to be dismantled;
• Figure 2 is a diagram illustrating bridging devices used to relax the cable of Figure 1;
• Figures 3 to 5 are diagrams showing successive steps of the detension of a cable according to an advantageous embodiment of the invention;
• Fig. 6 is a diagram showing a support mode of the cable of Fig. 1 when relaxed;
• Figure 7 is a diagram showing another support mode of the cable of Figure 1 when relaxed;
• Figure 8 is a transverse view of a portion of the support device used according to the support mode of Figure 7;
• Figure 9 is a diagram showing an intermediate step of the evacuation of the cable of Figure 1 according to an advantageous embodiment of the invention.

The invention is hereinafter described in the nonlimiting example of a stay cable. However, it also applies to any other type of cable stretched between two anchor points on a structure (cable carrying a suspension bridge, prestressing cable, etc.).

FIG. 1 shows a stay cable 1 stretched between two anchoring points on a cable-stayed bridge 2. The first anchoring point 5 is located on a pylon 3 of the deck 2, while the second anchoring point 6 is located on deck 4 of deck 2.

Although this has not been shown in FIG. 1, other cables substantially parallel to the cable 1 can be stretched between corresponding anchoring points on the bridge 2.

The present invention aims to dismantle the cable 1 without damaging either the bridge 2 or any other cables anchored on the bridge 2.

For this purpose, it is possible to relax the cable 1 so that a current part of this cable is released from the anchor 5 and / or the anchor 6 which binds it to the structure 2.

It is recalled that the release of a linear structural element composed of one or more metal strands and stretched between two points considered relatively fixed, as is the case of the cable 1 of FIG. 1, is often problematic, especially when no specific device was planned during initial design.

In particular, a reduction of the resistant section of such a cable by cutting, without taking special precautions, would increase the stresses in the remaining section until the breaking stress of the material. The resulting fracture would be abrupt and produce harmful dynamic effects, since the sudden release of stored energy in the cable could lead to rapid, large and uncontrolled deformations ("whipping effect"), extremely dangerous for the immediate environment of the cable. cable, that is to say for the structure in which the cable participates, but also for the staff responsible for cutting the cable.

A detension of the cable 1 advantageously makes it possible to limit these disadvantages. It can for example be achieved by placing, near the top anchoring point 5 and / or the lower anchoring point 6 of the cable 1, a bridging device 7 capable of taking up the pulling force of the cable on a portion of it (see Figure 2).

As shown in FIGS. 3 to 5, this bridging device 7 may comprise two clamps 12 positioned around the cable 1 to provide a structural connection therewith. Each of these collars 12 preferably has the capacity to withstand the tensile force F of the cable 1 substantially without sliding along it. In particular, if the cable 1 is provided with a sheath surrounding the metal strands that constitute it, this sheath will advantageously be removed at the right of the collars 12.

In addition, in the example illustrated in FIGS. 3 to 5, pull bars 13 connect the collars 12 in order to carry out the actual bridging. These drawbars are preferably at least two in number and are preferably arranged so that their center of gravity is substantially at the same location as that of the cable 1 to be relaxed. They are chosen to be able to withstand the tensile force F to which the cable 1 is initially subjected.

In the example illustrated in FIGS. 3 to 5, adjustment means 14 for the traction force passing through the traction bars 13 have been represented. These adjustment means 14 may for example comprise cylinders.

In addition, means of monitoring (or monitoring) 15 the traction force transiting in the drawbars can also be used. In the figures, the adjustment means 14 and the means 15 for monitoring the tensile force have been shown near opposite ends of the pull rods 13. However, it will be understood that such means can be positioned differently, for example on the same side of the drawbars.

In the step illustrated in Figure 3, the cable 1 is subjected to the tensile force F which corresponds to the initial tension of the cable over its entire length between the anchors 5 and 6. At this point, the tensile force in the bridging device is zero or almost zero.

Subsequently, the traction bars 13 of the bridging device 7 are put into tension - which is symbolized in FIG. 4 by the voltage f - until the sum of their voltages reaches a value greater than or equal to assumed value of the tensile force F of the cable 1. Of course, if the value the tensile force F is known, the pull rods 13 can be tensioned to reach precisely this value.

At the end of this operation, the force F has been totally transferred from the portion considered 11 of the cable 1 to the corresponding bridging device 7. The portion 11 of the cable is then subjected to almost no effort.

Therefore, said portion 11 of the cable placed between the clamps 12 can then be cut safely, as shown in Figure 5. The sectioning of the portion 11 of the cable in two sub-portions 11a and 11b can be realized in different ways, for example by successive cutting of each strand of the cable 1 or localized and intensive heating of this cable portion to rupture.

During the step of severing the cable, it can advantageously be verified by means of monitoring means 15 that the tensile force in the bridging device varies relatively little. This ensures that the bridging device has taken locally all the traction force F to which the cable 1 was initially subjected.

Once the cable 1 is cut, the tensile force in the bridging device can be released gradually until canceled by means of adjustment means 14. This has the effect of relaxing the cable 1 as a whole. The means 15 for monitoring the traction force can advantageously be used to control this operation.

It will thus be understood that the cable 1 has been relaxed without any sudden variation of effort has been encountered, since the sectioning of the cable has taken place in a portion where its state of stress was almost zero.

At the end of the advantageous operations described above, the current portion of the cable 1 is released from the top anchor 5 and / or the bottom anchor 6. When the detension has been performed near a single point anchoring, for example the lower anchor point 6 which is the most accessible, then releases the current portion of the cable from the other anchor point, for example the anchor point 5. This second release can be for example by simply cutting said portion of cable near the other anchor point. No bridging device is needed for this cutting which is safe, as the cable has already been relaxed. Alternatively, the release of the current portion of the cable from the other anchor point could result from a withdrawal of the cable from said other anchor. The current part of the cable is then completely released from the top 5 and bottom anchors 6 (as symbolized by the crosses near these anchors in FIGS. 6 and 7).

The current part of the cable 1 is then supported so as not to collapse under the effect of its own weight, which could damage the deck 4 of the bridge 2 and any other cables located under the cable 1.

In an example illustrated in FIG. 6, the current part of the cable 1, once relaxed, is supported by means of a support 10 on which it rests in part, this support 10 being itself held by an auxiliary structure 15 type crane or tower scaffold for example. Thus, the current portion of the cable is lifted locally at the support 10, which ensures its maintenance pending its evacuation.

Figure 7 illustrates another example in which a plurality of supports 18 support the current part of the cable 1 waiting for its evacuation. These supports 18 are advantageously distributed, possibly uniformly, over the entire length of the running portion of the cable 1.

The supports 18 advantageously form cradles receiving the current part of the cable 1 as illustrated in FIG. 8. They are held by one or more cables 20 situated higher than the cable 1, to which they are connected by means of lines 17 by example. In the example illustrated in FIG. 8, the cradles 18 are thus suspended to rest on two cables 20 located on either side of the cable 1.

The cradles 18 are advantageously connected to each other and mounted so as to be able to move along the cables 20. In the illustrated example, this displacement is ensured by rollers 16 to which the lines 17 are connected and which are capable of rolling. on the cables 20.

The cables 20 which maintain the cradles 18 may be constituent cables of the structure 2, for example cables with cable stayed permanently between the pylon 3 and the deck 4 of the bridge 2, like the cable 1.

Alternatively, these cables 20 may be temporarily mounted on the structure 2 to allow the support of the cable 1 to be disassembled. In this case, the cables 20 may be anchored in anchor blocks temporarily connected to the pylon 3 and the deck 4, rather than directly in the pylon 3 and the deck 4. These anchor blocks are then placed near the points anchoring 5 and 6 of the cable 1. Thus, the temporary cables 20 can be removed from the structure 2, once the cable 1 disassembled.

When the support device described with reference to FIGS. 7 and 8 is used, the disassembling sequence of the relaxed cable 1 can then proceed in the following manner.

The set composed of the current part of the cable 1 and the cradles 18 on which this part of the cable 1 rests is progressively lowered. The progressive descent is advantageously carried out using retaining means 19 capable of holding the current part of the cable 1, as illustrated in FIG. 9. A controlled flow cable connected to the cable 1 may for example constitute such retaining means. 19. Alternatively or in addition, retaining means may be arranged to control the descent of the cradles 18.

During the descent, the rollers 16 roll on the cables 20, which causes the cradles 18 and the running part of the cable 1 that they support towards the deck 4 of the deck 2. This ensures the evacuation of the current portion of the cable 1 away from the high anchor 5 by which the cable 1 was initially attached to the pylon 3 of the bridge 2.

Note also that the parts of the cable 1 remained attached to the top 5 and bottom anchors 6, after release of the current portion of the cable 1, will be advantageously removed from their respective anchors to be evacuated.

Advantageously, the current part of the cable 1 can be cut during its evacuation. This can be done by cutting the cable 1 into elements of reduced length, preferably easily transportable by road, as the cable is lowered to the deck 4 of the bridge 2.

FIG. 9 illustrates an intermediate step of disassembling the cable 1, in which a new element 21 has been obtained by cutting off the portion of the cable 1 that has just reached the apron 4. The elements 22 represent, in turn, elements of the cable 1 previously cut and grouped substantially in the same place for possible final evacuation at a distance from the bridge 2.

The disassembly process is then continued in the same manner until the current portion of the cable 1 has been fully lowered to the deck 4 of the bridge 2 and possibly cut into elements of reduced length 22. The elements 22 obtained can then be evacuated at a distance from bridge 2.

At the end of these operations all the supports 18, the lines 17 and the rollers 16 are grouped near the deck 4 of the bridge 2. They can then be recovered to serve during the disassembly of another cable. When the cables 20 are temporary, they can in turn be removed from their anchors.

This results in easy disassembly of the cable 1, which does not damage the structure 2, or any other shrouds of the sheet to which the cable 1 belongs. In addition, the discomfort of the traffic on the bridge 2 is minimized during the dismantling of the cable 1. Moreover, the dismantling can be carried out without any means having been provided for this purpose during the design of the structure 2 .

It will be noted in particular that the support device described with reference to FIGS. 7 to 9 is particularly advantageous since it comprises light means capable of contributing to the support and also to the evacuation of a large part of the cable, in spite of the large mass of this cable and the high height of the high anchor 5 to which the cable 1 was initially fixed.

Claims (14)

A method of disassembling a cable (1) stretched between a first (5) and a second (6) anchor point on a structure (2), comprising the steps of: - Release a current portion of the cable of said first and second anchor points; - support said current portion of the cable; and - evacuate said current portion of the cable away from at least one of said first and second anchor points, wherein the support and the evacuation of said current part of the cable (1) are effected by means of a plurality of supports (18) distributed along said current part of the cable and forming cradles for said current part. of the cable, each held by at least one other cable (20) located higher than said cable, the cradles (18) being connected to each other and being mounted so as to be able to move along said other cable (20). The method of claim 1, wherein said other cable (20) is stretched between anchor points on said structure. The method of claim 2, wherein said other cable (20) is provisionally anchored near said first (5) and second (6) anchor points for the purpose of maintaining the cradles (18). A method according to any one of the preceding claims, wherein the movement of cradles (18) along said other cable (20) is provided by rollers (16). A method as claimed in any one of the preceding claims, wherein the first anchor point (5) is located higher than the second anchor point (6) and wherein the discharge of said running portion of the cable (1) remote from at least one of said first and second anchor points comprises lowering said current portion of the cable substantially up to the height of the second anchor point, the descent of said current portion of the cable being controlled by means of retaining means (19) of said current portion of the cable and / or cradles. A method as claimed in any one of the preceding claims, wherein said current portion of the cable (1) is severed during its evacuation. A method as claimed in any one of the preceding claims, wherein releasing the running portion of the cable from said first and second anchor points comprises detenting the cable so that the running portion of the cable is released from one of said first and second anchoring points and releasing said current portion of the cable from the other of said first and second anchor points. The method of claim 7, wherein the detension of the cable (1) comprises the following steps, performed near the first (5) and / or the second anchoring points (6): - Place on a portion (11) of the cable a bridging device (7) capable of taking up the tensile force (F) of the cable on said portion; - Tensioning the bridging device to a value greater than or equal to an assumed value of the tensile force of the cable, so as to cancel the tensile force of the cable on said portion; and - Cut off said portion of the cable. The method of claim 8, wherein the voltage is then canceled in the bridging device (7). A method according to claim 8 or 9, wherein the placement of the bridging device (7) comprises positioning two collars (12) of the bridging device around the cable so as to provide substantially non-slip contact of the collars along the cable and wherein the tensioning of the bridging device comprises tensioning traction rods (13) of the bridging device connecting said collars. A method according to any one of claims 8 to 10, wherein the tensile force in the bridging device is controlled by means of a monitoring means (15) when the bridging device is tensioned and / or during the cutting of said portion of the cable. A method as claimed in any one of the preceding claims, wherein said cable (1) is a stay cable. Support device for a cable (1) stretched between a first (5) and a second (6) anchoring point on a structure (2), the support device comprising: - A plurality of cradles (18) adapted to be distributed along a current portion of the cable (1) to form supports for said current portion of the cable; - means for each cradle of the plurality rests on at least one other cable (20) located higher than said cable and can move along said other cable; and - Means connecting the cradles to each other. System for dismounting a cable (1) stretched between a first (5) and a second (6) anchoring point on a structure (2), including a support device comprising: - A plurality of cradles (18) adapted to be distributed along a current portion of the cable (1) to form supports for said current portion of the cable; - means for each cradle of the plurality rests on at least one other cable (20) located higher than said cable and can move along said other cable; and means connecting the cradles to one another, and a bridging device (7) for expanding the tensioned cable (1), the bridging device comprising: - Two collars (12) adapted to be positioned around the cable so as to ensure substantially no sliding contact along the cable; - Traction rods (13) connecting said collars; - Adjustment means (14) of the traction force passing through the traction bars; and - Monitoring means (15) of the traction force passing through the drawbars.

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