WO1998027362A1

WO1998027362A1 - Method and device for damping transverse vibrations of staying cables

Info

Publication number: WO1998027362A1
Application number: PCT/FR1997/002290
Authority: WO
Inventors: Bruno Domange; Alfred Krief
Original assignee: Jarret
Priority date: 1996-12-16
Filing date: 1997-12-12
Publication date: 1998-06-25
Also published as: FR2757235B1; JP4071291B2; FR2757235A1; JP2001507108A; AU5489698A

Abstract

The invention concerns the damping of transverse vibrations of staying cables which consists in: winding tightly on the cable (20) to be damped, at the most appropriate places, at least one pipe coil (27) filled with a fluid; enclosing the pipe wound on the cable in a rigid sheath (22) in which the wound coil is enclosed and stressed and making the sheath integral with a fixed point distinct from the part of the cable on which said pipe is wound. The invention is applicable in particular to the damping of vibrating movements of cables for overhead cranes or for holding fast masts.

Description

"METHOD AND DEVICE FOR DAMPING CROSS-SECTION VIBRATIONS IN SHELF CABLES"

The subject of the invention is a method and a device for damping transverse vibrations of guying cables.

Guy lines made up of guy cables are in common use for a number of constructions or holding structures in place, such as suspended deck bridges, ship masts, pylons, etc. One of the problems which arises with this type of construction is that the cables, which sometimes support considerable loads and tensions, can, under the effect of relatively low external stresses, such as the action of the wind, the tremors due to the traffic, rain, being subjected to transverse vibrations which, in particular in the case of additional resonance phenomena, can cause the cables to vibrate transversely very strongly by generating parallel parasitic movements such as for example a vertical excitation of the apron a guyed bridge or twists of a mast foot, causing fatigue and weakening of the elements of the structure subjected to these vibrations.

However, extensive scientific work has made it possible to conclude:

1 °) that an external contribution of damping, even weak, could considerably attenuate this parasitic phenomenon, 2 °) only to be the most effective possible, that is to say, to be able to dampen the greatest number possible resonant frequencies, the damper should be located near a point of attachment of the cable, for example about one meter from one end, the phenomenon being quite similar to that of the vibrating strings. To date, however, it has not been possible to produce effective shock absorbers which, moreover, have a satisfactory service life.

Certain solutions proposed according to the prior art use linear hydraulic shock absorbers, of the type used on trucks, and which are fixed to the cable to be damped, for example at a distance of about one meter from its point d anchoring by orienting it substantially perpendicular to the cable and by fixing the other end to a fixed point distinct from the cable, for example a part of the bridge deck suspended from the cable. Such an embodiment is schematically illustrated in FIG. 1. According to another known solution, neoprene rubber plates are placed around the cable, always at a slight distance from its anchoring point, which is fixed to a deflection foot, for example fixed to the apron. This embodiment is schematically illustrated in FIG. 2.

But in practice, these solutions are not satisfactory, the depreciation being insufficient and the life of the devices too short.

Another difficulty linked to the problem to be solved is that if one wishes to be able to intervene after the fact on a structure to correct poorly damped vibrations, or if one has to change a cable, the operations for installing the damping device can be very complicated if the device requires that it be installed at the same time as the cable, which cannot be added afterwards to the cable installed.

The subject of the invention is a method and a device which make it possible to solve these problems. The method of damping the transverse vibrations of guying cables according to the invention is characterized in that at least one turn of a pipe filled with hose is wound tightly over the cables to be damped. '' a high viscosity fluid of a type used in hydrostatic compression dampers, the hose thus wound on the cable is enclosed in a rigid envelope in which is enclosed and constrained the coiled pipe, and the envelope is made integral with a fixed point distinct from the part of cable on which the above-mentioned pipe is applied.

In a preferred embodiment, after placing the tight winding of the pipe on the cable and placing the casing, the pipe is filled with the aforementioned high viscosity fluid until a pressure is reached. high operating, advantageously of the order of several hundred bars.

When you do this, you get the following advantages:

1 °) The process can be applied to any preexisting construction, and just as well to a new construction, this without any difficulty of installation.

2) The damping is effective for a very wide frequency range, since the damping can be effective over a significant length of cable, as large as desired, requiring only to consequently increase the number of turns which surround the cable, and consequently, damping the vibration from its birth at any point whatsoever of this length of application. 3 °) Due to the use of a fluid with high viscosity under pressure, and as will appear more clearly from the description which follows, a very significant damping is obtained due to the viscous friction created by the displacement of the fluid at high viscosity in the pipe which deforms when the cable vibrates. 4) Due to the high pressures that can be applied to the fluid, the effects of variation in the efficiency of the system are considerably limited as a function of the variations in temperature to which the guying can be subjected. The invention also relates to a device allowing the implementation of the above-mentioned method, a device which is characterized in that it comprises:

- At least one length of a pipe capable of being filled with a high viscosity fluid and of withstanding high operating pressures, of at least several tens of bars, the length being sufficient to form at least one turn winding on the cable to be damped,

- at least one valve type system fitted to at least one end of the pipe, allowing the filling of the pipe by means of the high viscosity fluid under the operating pressure of the device,

- at least one rigid envelope, the dimensions of which: diameter / length, are adapted to closely match the outside surface of the hose wound in place on the cable,

- end boxes laterally closing the device in place around the cable, and joining the casing while holding the two ends of the pipe in place.

The invention and its implementation will appear more clearly with the aid of the detailed description which follows, made with reference to the appended drawings, in which: FIGS. 1 and 2 very schematically show two systems proposed by the prior art ;

Figure 3 is a longitudinal sectional view of a shroud damping device according to the invention;

Figure 4 is an enlarged view of the part of Figure 3 surrounded in IV;

Figure 5 is an enlarged view of the V-shaped portion of Figure 3;

Figure 6 is a sectional view taken along the plane VI-VI of Figure 4; Figure 7 is a view similar to that of Figure 6 but showing the device in another position in which the cable is moved out of its centering position in the device;

Figure 8 is a sectional view taken along the plane VIII-VIII of Figure 4;

Figure 9 is a sectional view taken along the plane LX-LX of Figure 4;

Figure 10 is a sectional view taken along the plane X-X of Figure 8; Figure 11 is a sectional view taken along the plane XI-XI of Figure 4;

Figure 12 is a view cut away to illustrate a two-stage damping variant.

Referring to the drawings, firstly to Figures 1 and 2, there is schematically illustrated a portion of a bridge deck 10 supported by a cable or guy 11 anchored at 12 on an anchor 13 secured to the apron 10. To obtain the damping of the vibrations of the cable, a hydraulic linear damper schematized at 14 is provided, of the type used on trucks, one end of which is fixed at 15 to the apron 10, and the other end of which is fixed at 16 around the cable 11. Advantageously, the point 16 is located about one meter from the anchor point 12 of the guy 11 on the deck, so that the damping is as effective as possible. Studies have shown that it is towards the anchoring end of the guy 11 that the damping effect is most effective, the cable 11 reacting like a vibrating cord.

In practice, however, this device is damaged by being subjected to excessive fatigue.

In Figure 2 there is shown another damping device known from the prior art in which the damping device 17 is constituted by rubber plates of the neoprene type shown diagrammatically at 18 which take the cable 11 at the same level as the damper of FIG. 1 and which are fixed to a support leg 19 secured to the deck 10.

Again, this device has not been shown to be very effective and its lifespan is reduced. FIG. 3 schematically illustrates the constitution of a damping device according to the invention.

Referring to this figure, there is shown at 20 the cable whose vibration movements must be damped. Around the cable, there has been fixed, according to a procedure which will be described in detail below, a damping device according to the invention referenced as a whole 21. The device 21 occupies on the cable substantially the position of the damping devices illustrated in Figures 1 and 2. The device itself is fixed for example to the deck 10 of the bridge either by a base similar to the base 19 of FIG. 2, which will then come to rest on the casing 22 of the device, or at the level for example of an elongated tube 23 which will be fixed to one of the housings 24 terminating the device on one side, and at its other end (not shown) to the anchoring part such as the part 13 illustrated in FIGS. 1 and 2.

The device 21 comprises the cylindrical envelope 22 with circular section retained between the two end boxes 24, 25 of the device. The shape and constitution of these parts will appear more clearly during the description which follows of the figures which show them in detail.

In the example illustrated, around the cable 20 has been mounted a spacer wedge 26 on which we see wound a pipe 27 which forms several juxtaposed turns. In the example illustrated in FIG. 3, there are about ten turns of the pipe 27 wound on the spacer 26. The pipe 27 ends at its two ends 27a, 27b with two end pieces 28, 29 respectively, which end pieces are wedged respectively in the housing 24 and in the housing 25 as will be described in more detail below. At its end opposite to the fixing tube 23, the device is closed, over the housing 25, by a cover 30, the seal being produced for example by a rubber O-ring 31 or by a seal of the type lips 32. Referring to FIG. 4, we will describe in more detail certain parts of the device on this side referenced IV in FIG. 3.

In this figure, we can see more precisely, and also referring in parallel to FIG. 6, how the first winding turn of the pipe 27 with its end piece is formed. We also see, more particularly in FIG. 6, how is held and wedged in the housing 24, the end of the pipe 27 by its end piece 28. In the end piece 28 is screwed a bolt 33, which is advantageously equipped with an injection valve (not shown) for the rubber silicone forming the high viscosity fluid with which the pipe 27 will be filled for its operation. Such bolts equipped, generally in their axis, with a ball valve or the like, are conventional in the art. In FIG. 6, only a ball 34 in the bolt 33 has only been suggested for the record.

In the same FIG. 6, it can be clearly seen that the spacer wedge 26 is in fact formed by two symmetrical half-shims 26a, 26b, which of course facilitates mounting around the cable 20. These shims 26a, 26b are made of a material incompressible, such as for example a suitable metal alloy, and provision is advantageously provided around the cable 20 for an intermediate protective coating 35 which prevents the cable from being injured, for example made of a suitable synthetic material. It can also be observed, as can be seen in FIGS. 3 and 6, that the housing 24 is constituted by two half-housings, respectively referenced 24a, making it possible to accommodate the end piece 28 and the bolt 33 and 24b not provided with such an inlet for fixing the end of the hose 27.

Returning to FIG. 4, we also see how the envelope 22, made up of two cylindrical half-cylinders 22a, 22b, engages and fits by its end cheeks 36, 37, also visible in FIG. 3, on returns conformed in accordance 38, 39 of the housing 24. At 40, 41, the fixing lines of bolts (not shown) which will allow the envelope 22 to be secured to the housing 24. Likewise, at 42, 43 (see FIGS. 3 and 4), the bolt fixing axes (not shown) which will allow securing, after assembly, the housing 24 to the fixing tube 23. Like the housing 24, like the envelope 22, the fixing tube 23 is also formed in two parts 23a, 23b respectively, as will appear more clearly in FIGS. 8 and 9. Referring to FIG. 5, at the other end of the device 21, we can see the end piece 29 which has been fixed similarly to the end piece 28, in a cooperating inlet provided in the housing 25 and more precisely in the half 25a of the housing 25 which has this input. It will be observed that in FIG. 3, the part 25a is located towards the bottom of the figure, while in FIG. 5, the part 25a is situated at the top of the figure. In fact, as will be explained below, when the hose has been wound on the support wedge 26, more precisely on the two half-shims 26a, 26b, the housing 25 is rotated relative to the housing 24 so as to ensure a correct winding of the pipe on the shim, whatever the length of the pipe, to within a few millimeters, this operation being carried out without difficulty as long as the pipe has not been filled with the viscous fluid under pressure which it will contain for its operation. In Figure 5, we also see the cover 30 also formed of two halves 30a, 30b, fixed by bolts (not shown), only a fixing axis 44 of the bolts having been shown in Figure 5. It is observed that l 'envelope 22 engages with the housing 25 in the same way with the housing 24 through the cheeks 45, 46 of the half-envelopes 22a, 22b which come under the protruding edges 47, 48 of the half-housings 25a, 25b, la fixing being again ensured by bolts of which only the fixing axes 48, 49 have been referenced (Figure 5). Referring now to Figures 8, 9 and 10, there is illustrated a practical embodiment of the fixing tube 23 for fixing the damping device 21 according to the invention, for example to the anchor 13 cable 11 (see figures 1 and 2). The tube 23 is formed of two parts 23a, 23b. To facilitate assembly and assembly, on the side of the head of the tube, before the enlarged part which comes to cover the housing 24, and as seen in FIG. 8, the tube has a substantially square section allowing the cable 20 to play freely inside him. At this level, the two housings 23a, 23b of the tube have cheeks 23c, 23d respectively in which holes 50 are formed for fixing by means of bolts (not shown). A little further from the device, that is to say by approaching the cable anchoring, the tube 23 advantageously has a circular cylindrical shape formed by the two half-parts 23a, 23b, the cable 20 playing freely with the inside the tube. FIG. 10 shows more precisely the shape of the assembly cheeks 23c.

Referring to FIG. 11, it has also been shown more precisely how the winding shim 26 formed of the two half-shims 26a, 26b, for example made of a metallic alloy, comprising cheeks such as 26c, can be made up. 26d, drilled with holes 51 allowing the fixing of the two half-shims around the cable 20, for example by means of bolts and nuts (not shown).

We will now quickly describe the installation of the device. As explained previously, the tube 23, the housing 24, the casing 22, the housing 25, the shim 26 and the cap 30 are formed in two halves respectively 23, 23b for the tube, 24a, 24b for the housing 24, 22a, 22b for the casing 22, 25a, 25b for the housing 25, 26a, 26b for the shim 26, and 30a, 30b for the cover 30. Under these conditions, a cable 20 being in place, it is possible to assemble the device over him without any disassembly, always extremely delicate, of the cable. We can for example proceed as follows. Firstly, the pipe 27 is wound approximately at the desired location around the cable, forming the number of turns required, for example ten in the example illustrated. In the example illustrated in fact, the pipe is not wound on the cable, but on the shim 26. Under these conditions, the two half shims 26a, 26b are first positioned on the cable at the desired location , possibly having previously protected the cable with an adequate coating as illustrated in 35 (see FIG. 6) and the shims are assembled by their fixing bolts which join the two half-shims 26a, 26b to form the shim complete. The two fixing half-tubes 23a, 23b are then engaged, then the two half-housings 25a, 25b which are positioned and assembled correctly. Then, over the flexible hose which is empty of fluid, the two half-envelopes 22a, 22b are engaged by correctly engaging the cheeks 36, 37 under the protruding projections 38, 39 of the housing 24, the two half-envelopes being assembled by compressing the winding of the pipe slightly, the two half-shells 25a, 25b of the housing 25 are correctly positioned over it. The two are correctly adjusted in the inlet of the half-housing 24a and in the inlet of the half-housing 25a ends of the pipe, fitted at each end with a closing bolt such as 33, at least one of which is fitted with a valve, for example a ball 34 for introducing the fluid. The housing 25 is then rotated relative to the housing 24 so as to bring the pipe 27 into the suitable working position in which the turns must be slightly ovalized, as illustrated in the drawings, that is to say slightly flattened between wedges and envelope, the turns being contiguous. This is easily obtained due to the flexibility of the hose, empty of any product. This operation being carried out, it only remains to tighten all the bolts of the assembly and to put in place the cover formed by the two halves 30a, 30b with interposition of the seal. If an O-ring 31 is used, it is of a formed type of a windable turn so that it can also be mounted around the cable 20 without difficulty.

With the device in place, all that remains is to introduce into the tube, under the required working pressure, the high viscosity fluid most suitable for the application in question.

If it is desired to maintain the operation of the device within a pressure range almost independent of the temperature to which the device can be subjected, it is advantageous to provide (not shown) an external source of a reserve of pressurized fluid in communication with the interior space of the pipe, for example by the valve 34 for admitting the fluid.

The operation of the device will now be quickly explained.

Referring to FIGS. 6 and 7, and comparing these figures, it can be seen that in FIG. 6, the cable 20 is centered relative to the housing 24.

In FIG. 7, there is a slight shift, in other words the cable 20 has moved slightly to the right of the figure in FIG. 7 relative to the position that the cable occupied in FIG. 6. This creates a certain crushing, shown in 27 ', of the pipe 27 on the right, and a slight loosening resulting in a rounding of the pipe as illustrated in 27 ". The circular section being of greater volume than the flattened section, taking into account the non- expandable from the hose used, the fluid is forced to move in the hose, from the flattened part to the rounded part, which creates an imbalance in the preload and therefore a resistant force and viscous friction originating in the high viscosity fluid and prestressed under operating pressure.

In the embodiment shown diagrammatically in FIG. 12, the shim 26 has been eliminated and around the cable 20 two successive stages of coiled pipes, respectively referenced 57 between cable 20 and casing 58, and hose 59 coiled between casing have been used 58 and envelope 60. In such construction, the casing 58 plays, for the pipe 59, the role played by the wedge 26 in the embodiment of the previous figures, while the casing 60 plays the role of the casing 22 of the previous embodiment. The use of a two-stage device, which can be generalized to a greater number of stages, has the advantage of being able to wind pipes of smaller diameter which are more resistant and can therefore be filled with a viscous fluid under higher pressure. This also makes it possible to increase the amplitudes of movement of the cable and / or to reduce the fatigue of the pipes used. And it is known that the higher the working pressure, the greater the damping effect and the less sensitive the action of a variation in temperature.

In the application illustrated in FIG. 12, it is clear that the lengths of the pipes 57, 59 will increase as the diameter of the winding increases. It may therefore be advantageous in certain cases to mount at least two stages of pipe winding turns one on top of the other, the envelope of stage n constituting the winding surface of the floor of the next row n + 1.

Advantageously, the casing 22 will be made of steel, so as to be able to withstand the pressures of the pipe which it encloses, while the housings 24, 25 may also be made of steel or another resistant metal such as cast iron for example. . The nature of the pipe will be such that it can withstand the operating pressures envisaged, which can range, as the case may be, between 0 bar and 1000 bars, pressures which can easily be envisaged preferably between a few tens of bars and a few hundreds of bars. Hoses of rubber or equivalent, suitably reinforced, braided in synthetic textile fibers, glass fibers, possibly metallic, may be suitable. By guying cables is meant by extension any elongated structure liable to vibrate such as in particular flexible mast or mast hanger for which the invention applies equally well.

The fluids used will advantageously be fluids of the silicone type with high viscosity, for example greater than 10 million centistokes, such fluids being conventionally used in dampers of the hydrostatic compression type.

Claims

1. A method of damping transverse vibrations of guying cables, characterized in that at least one turn of a pipe (27) filled with a hose is wound tightly on the cables to be damped, in the most suitable places. high viscosity fluid of a type used in hydrostatic compression dampers, the hose thus wound is enclosed on the cable in a rigid envelope (22) in which the wound hose is enclosed and constrained, and the envelope is secured (22) from a fixed point distinct from the part of cable on which the above-mentioned pipe is applied.

2. Method according to claim 1, characterized in that after setting up the tight winding of the pipe (27) on the cable (20) and setting up the casing (22), the pipe is filled with medium of the aforementioned high viscosity fluid, until a high operating pressure is reached, advantageously of the order of several hundred bars.

3. Method according to claim 1 or claim 2, characterized in that interposed between the pipe (27) and the cable (20) to absorb shims (26) of incompressible material increasing the diameter of winding of the pipe on the cable.

4. Method according to any one of the preceding claims, characterized in that at least two stages of pipe winding turns (57, 59) are mounted in series one above the other, the casing ( 58) of the stage of row n constituting the winding surface of the stage of row according to n + 1.

5. Device for implementing the method according to any one of the preceding claims, characterized in that it comprises:

- At least one length of a tube (27) capable of being filled with a high viscosity fluid and of withstanding high operating pressures, of at least several tens of bars, the length being sufficient to form at minus a winding turn on the cable to amortize,

- at least one valve type system (34) equipping at least one end (33) of the pipe allowing the filling of the pipe by means of the high viscosity fluid under the operating pressure of the device, - at least one rigid envelope (22 ) whose dimensions: diameter / length, are adapted to closely fit the outside surface of the pipe 27 wound in place on the cable 20,

- End boxes (24, 25) laterally closing the device in place around the cable and joining the casing (22) while holding in place the two ends of the pipe (27).

6. Device according to claim 5, characterized in that it further comprises spacer shims (26) of incompressible material adapting to the cable (20) and receiving the winding turns of the pipe (27).

7. Device according to claim 5 or claim 6, related to the process claim 4, characterized in that it comprises several lengths going from crescent to pipes (57, 59) above intended to form several superimposed windings in a device multi-stage depreciation.

8. Device according to any one of claims 5 to 7, characterized in that the envelopes (22), the housings (24, 25) and the optional shims (26) consist of at least two separable parts, advantageously two parts substantially symmetrical assembled around their central axis through which the cable passes in the operating position of the device.

9. Device according to any one of claims 5 to 8, assembled in the operating position on a cable, characterized in that it comprises several turns of pipe (27) wound tightly slightly constrained in ovalization, flattened between cable (20) or shim (26) for winding and envelope (22) of stress in the centered rest position of the device, and at least one fastening clip (23) of the device at a fixed point outside the cable (20) such as cable anchoring, adjacent part of a bridge deck or other part of the cable-stayed structure.

10. Device according to claim 9, characterized in that the pipe or pipes filled with high viscosity fluid are connected to an external source of a reserve of pressurized fluid.