Patent Application
20200263355
The present invention relates to structural cables used in civil engineering, for instance in cable-stayed bridges. It is applicable, in particular, to the sheath of such cables used for supporting, stiffening or stabilizing structures.
Stay cables are widely used to support suspended structures such as bridge decks or roofs. They can also be used to stabilize erected structures such as towers or masts.
A typical stay cable includes a bundle of tendons, for example wires or strands, housed in a collective sheath. The sheath is intended to protect the metallic tendons of the bundle.
By design, the sheath is destined to be in contact with the surrounding environment. As such, it is susceptible to the formation of frost, rime, ice or snow thereon.
Addressing this phenomenon is important, as the presence of frost, rime, ice or snow on the sheath may significantly alter the aerodynamic properties of the stay cable, which in turn may lead to vibrations of the cable.
Several approaches have been developed to address this specific problem, such as an approach relying on a metallic collar configured to break ice and frost by being moved along the sheath.
However, this is not fully satisfactory, as it tends to erode the sheath, and plainly become unusable in certain circumstances.
In addition, the other known approaches all exhibit drawbacks.
An object of the present invention is to propose a sheath of a structural cable that can prevent ice, frost, rime or snow from forming thereon and/or remove ice, frost, rime or snow therefrom in an improved manner.
To that end, the invention relates to a sheath of a structural cable of a construction work, the structural cable being destined to comprise a bundle of tendons destined to bear a load of the structural cable and to be received within said sheath, the sheath having an outer surface and the sheath being made of a single layer of material over at least a part of the length of the sheath, the sheath comprising heating components arranged within said single layer, the heating components being configured for receiving electrical energy and, using said electrical energy, heating at least the outer surface of the sheath so as to prevent ice, snow, rime or frost from forming thereon or remove ice, snow, rime or frost from the outer surface of the sheath.
According to an aspect of the invention, the heating components are located within a portion of the single layer having a thickness inferior to 30% of the thickness of said single layer.
According to an aspect of the invention, the portion includes the outer surface of the sheath.
According to an aspect of the invention, the portion is at a distance from the outer surface of the sheath.
According to an aspect of the invention, the portion is at a distance from the outer surface inferior or equal to 20% of the thickness of the single layer.
According to an aspect of the invention, the heating components are dispersed within the entirety of said single layer.
According to an aspect of the invention, the heating components include silver or carbon nanoparticles.
According to an aspect of the invention, the heating components include one or more electrical wires.
According to an aspect of the invention, the heating components are arranged so as to define at least one heating sheet within the sheath.
According to an aspect of the invention, the sheet is an openwork sheet.
According to an aspect of the invention, the porosity rate of the openwork sheet is at least 50%, wherein the porosity rate represents the ratio between the open surface of the sheet and the total surface of the sheet.
The invention also relates to a structural cable comprising:
According to an aspect of the invention, the structural cable further comprises a source of energy configured to provide the heating components with electrical energy to heat at least the outer surface of the sheath.
The invention also relates to a method of manufacturing a sheath of a structural cable of a construction work, the structural cable being destined to comprise a bundle of tendons destined to bear a load of the structural cable and to be received within said sheath, the sheath having an outer surface and the sheath being made of a single layer of material over at least a part of the length of the sheath, the method comprising forming the sheath from said material, wherein heating components are arranged within said material, the heating components being configured for receiving electrical energy and, using said electrical energy, heating at least the outer surface of the sheath so as to prevent ice, snow, rime or frost from forming thereon or remove ice, snow, rime or frost from the outer surface of the sheath.
Other features and advantages of the invention disclosed herein will become apparent from the following description of non-limiting embodiments, with reference to the appended drawings, in which:
The cable 10 is configured to take up efforts applied to a structure 12 to which it is anchored. To that end, it extends between two parts 14, 16 of a construction work which includes the structure 12. The first part 14 is for instance at a higher position than the second part 16. For example, the first part 14 belongs to the structure 12, such as a tower, while the second part 16 belongs to a foundation to stabilize the structure. Alternatively, the first part 14 may belong to a pylon, while the second part 16 belongs to some structure suspended from the pylon.
The construction work typically includes a number of structural cables 10, only one of them being shown in
The structural cable 10 comprises a load-bearing part 18 which comprises a bundle of tendons 20 disposed parallel to each other (
The bundle 20 forms the structural core of the cable 10, i.e. a main load-bearing component of the cable.
The cable 10 may have a length of up to several hundred meters. The bundle 20 may include a few tens of tendons.
The tendons of the bundle 20 are anchored at both ends of the bundle using an upper anchoring device 22 mounted on the first part 14 of the construction work and a lower anchoring device 24 mounted on the second part 16 of the construction work. Between the two anchoring devices 22, 24, the bundle of tendons for instance follows a catenary curve due to the weight of the cable and the tensile force maintained by the anchoring devices. The anchoring devices 22, 24 are positioned on the first and second parts 14, 16 by taking into account the pre-calculated catenary curve of each cable 10.
In reference to
The sheath 26 forms a protective structure for the bundle 20. More precisely, it presents itself in the general form of a tube which internally defines a cavity running along the length of the cable and within which the bundle of tendons is arranged.
The sheath 26 is in particular configured to protect the tendons from the surrounding environment, which would otherwise degrade the tendons rapidly.
In practice, it protects the tendons against mechanical and climatic stresses, such as air, light (in particular UV rays), humidity, rain, frost, snow, that may be combined with wind and/or chemical stresses due to air pollution and so on.
Advantageously, the sheath 26 extends over more than 80% of the length of the bundle of tendons 20 between the anchoring devices 22, 24, or even more than 90% for long stay cables.
In the example illustrated in
The sheath 26 has a cross-section which has any known shape.
For instance, this shape is chosen among polygonal, elliptical or circular. Advantageously, as shown on the Figures, this cross-section is circular.
The shape of the cross-section may vary along the longitudinal direction of the cable. Preferably however, it does not.
In addition, as depicted in
The sheath itself is illustrated in more details in reference to
The sheath 26 has an inner surface 28 and an outer surface 30.
The inner surface 28 faces the bundle of tendons.
The outer surface 30 is opposite to the inner surface 28. The outer surface 30 faces outwardly relative to the cable. It is for instance destined to be in direct contact with the surrounding environment and protect the bundle of tendons from it. In alternative configurations, it is destined to be at least in part in contact with another structure, such as a coating of the cable.
To that end, the outer surface 30 advantageously presents a surface treatment and/or structure destined to increase its resistance to the combined effects of rain and wind. For instance, the outer surface 30 of the sheath 26 may present at least one helical rib 27, and advantageously a double helical rib (not shown), running helically along all or part of the length of the outer surface of the sheath 26.
It should be noted that the outer surface of the sheath advantageously has a color which is designed to absorb solar radiations so as to thereby heat the outer portion of the thickness and prevent snow, ice, rime and frost to form thereon. For instance, the outer surface therefore exhibits a black color. It should be noted that in such a scenario, the matter of the outer surface is nonetheless resistant to UV radiations.
The sheath 26 may be an integral member between its longitudinal extremities. Alternatively, the sheath 26 includes longitudinal segments which are assembled together in an aligned manner, for instance through any known process. For instance, each segment has a length of a few meters, for instance between 6 and 12 m.
Each segment may present itself in the form of an integral piece of tube. Alternatively, one or more segment includes a plurality of sector-shaped elements assembled together.
Advantageously, the thickness 31 of the sheath 26, which corresponds to the radial distance between the inner surface 28 and the outer surface 30, is constant around the axis of the cable. Advantageously, this thickness 31 is comprised between 3 mm and 50 mm, and preferably between 5 mm and 30 mm.
In the context of the invention, at least over part of the length of the sheath 26, the sheath 26 comprises a single integral layer 32 of material which is adapted to generate heat and cause the frost, ice and so on to detach from the sheath, and/or prevent the formation of the latter thereon.
In other words, over the corresponding length of the cable, the sheath 26 is constituted by such a single layer which is capable of generating heat. This layer is made of at least one material which is arranged in a continuous manner radially, and which is integral, which means that it does not define a plurality of strata which are separated from one another.
It should be noted that this does not necessarily mean that the material which makes up the sheath 26 is necessarily the same over the entire thickness 31 of the sheath 26, and/or over the part of the length of the sheath 26 which is considered.
In particular, as discussed below, the sheath 26 may be manufactured so that different materials are made to be integral with one another so that they define the sheath 26 which is then single-layered in the sense of the invention.
As illustrated on the Figures, thus, over at least part of its length, the sheath is formed by the single layer 32, which occupies the entire volume defined between the inner surface 28 and the outer surface 30.
Advantageously, in the context of the invention, the single layer 32 extends over more than 30% of the length of the sheath 26. Preferably, it extends over more than 50% of the length of the sheath.
It should be noted that the sheath may include a plurality of disjoint regions which are distant from one another along the direction of the cable 10 and which together form this single layer 32. For instance, these regions may each correspond to one of the longitudinal segments of the sheath which are assembled together to form the entirety of the latter, although this is not necessarily the case.
In a general embodiment, however, the region of the sheath which is made by the single layer 32 extends continuously along the cable 10.
In a specific embodiment, regardless of the percentage of the length of the cable the layer 32 stretches over or not, the layer 32 stretches only over all or part of the region of the sheath which is located above a predetermined height. This height may be chosen as a minimum altitude of interest, a predetermined distance above the ground and/or a predetermined distance above a component of the structure the cable is coupled to, e.g. the deck of the bridge.
The single layer 32 for instance includes high density polyethylene (known as PEHD or HDPE) as its main component.
It should be noted that this single-layered configuration for the sheath does not exclude the use of a coating 35 (depicted in
In further view of
Due to their arrangement within the layer 32 which defines the entire thickness of the sheath over the considered portion, in the sense of the invention, the components 34 are embedded within the sheath. This embedded configuration is to be opposed to a coating or surface configuration in general, whereby the heating is obtained using a complex structure which is coupled to the sheath after the latter has been manufactured.
The heating components 34 are configured for receiving electrical energy and convert at least part of this energy into heat so as to heat the outer surface 30 of the sheath 26.
Typically, they are configured to do so by Joule Effect.
As indicated above, this heat is configured to prevent ice, snow, rime or frost from forming thereon and/or remove ice, snow, rime or frost from the outer surface of the sheath 26.
For this purpose, the heating components 34 have a chosen electrical conductivity which is configured to cause the heating at least of the outer surface 30 of the sheath 26.
In effect, each heating component 34 is configured to generate heat locally, this heat propagating within the matter of the layer 32 and reaching the outer surface of the sheath. In practice, although the components 34 may result in a particular region of the sheath being heated, such as a surface layer at the inner surface, heating the outer surface 30 of the sheath 26 is the intended effect.
Advantageously, the heating components 34 are configured so as to obtain a thermal power of at least 0.2 kW/m2 at the outer surface 30 of the sheath. Advantageously, the obtained thermal power is equal to or greater than 0.5 kW/m2.
In addition, the heating components are configured to prevent any damage to the components of the cable caused by the heat. In particular, they are configured to prevent any melting or burning of the sheath itself.
In a given embodiment, one or more of the following factors may be adjusted to reach the desired thermal power at the outer surface:
Advantageously, the percent by weight of the heating components 34 comprised in the layer 32 is at least 2%. Advantageously, this percent is equal or greater than 5%.
Advantageously, the heating components 34 are located in a portion 36 of the layer 32 which only stretches over part of the thickness 31 of the layer 32.
In other words, the heating components 34 are only present within part of the thickness 31 of the layer 32.
The portion 36 advantageously defines a connected space radially (relative to the axis of the cable). Preferably, it forms a single layer within the layer 32, as opposed to multiple layers which are apart and which need to be considered together.
However, the layer 32 may include a plurality of portions 36 which include components 34. These portions are for instance spread apart radially and optionally cover common longitudinal regions of the cable.
Advantageously, the portion 36 extends along the entirety of the layer 32.
Advantageously, the portion 36 is an external portion of the sheath.
In other words, the portion 36 includes the outer surface 30 of the sheath 26.
In other words, the heating components 34 are concentrated in the outer part of the thickness 31 of the layer 32.
However, as illustrated on
In such a configuration, the radial distance between the outer surface 30 of the sheath 26 and the portion 36 is advantageously inferior to 40%, and preferably to 20% of the thickness of the layer 32. For instance, it is at a distance to the outer surface 30 which is inferior or equal to 2 mm. This distance is for instance measured between the outer surface and the boundary of the portion 36 which is proximal to the latter.
This configuration may be advantageous when the outer surface 30 of the sheath 26 is to exhibit specific properties such as light-protection properties, in particular against UV rays. In effect, this outer surface 30 of the sheath 26 may then be made of a correspondingly-designed material which does not include components 34.
Regardless of the configuration, advantageously, the portion 36 has a thickness 37 inferior to 50% of the thickness 31 of the layer 32. Preferably, this thickness 37 is inferior to 30% of the thickness of the layer 32.
In an alternative general configuration, however, the heating components 34 may be present in the entire thickness 31 of the layer 32 of the sheath 26.
Advantageously, within the space the heating components 34 are present in (e.g. the portion 36 above if they are present only over part of the thickness of the layer 32, otherwise the layer 32 itself at least locally), the heating components 34 are evenly distributed. In other words, the heating components 34 are spatially distributed so as to prevent hot spots having a significantly higher temperature than other regions within the sheath 26, and/or cold spots having a significantly lower temperature than other regions within the sheath 26.
Regarding the heating components 34 themselves, in a first general configuration illustrated on
The heating components 34 may have a characteristic transverse dimension inferior to that, such as one close to 10−9 m.
For example, the heating components 34 are nanoparticles.
In a given embodiment, the heating components 34 are silver nanoparticles. In another embodiment, the heating components 34 are carbon nanoparticles. In another embodiment, the heating components include both silver and carbon nanoparticles.
In a second general configuration, the components 34 are not in the form of dispersed particles. In such a scenario, they define at least one structure which is arranged within the thickness 31 of the layer 32 and which is configured to generate the heat referred to above.
For example, in the embodiment of
For instance, the electrical wire(s) 38 has a solenoid arrangement. In other words, the electrical wire 38 is helically arranged along the longitudinal direction of the cable within the thickness of the sheath.
For instance, the wires 38 are then arranged regularly along this direction so as to prevent hot spots and/or cold spots as discussed above.
Advantageously, the wire 38 includes an alloy of Nickel and Chrome and/or Nickel and Copper. These alloys allow for a refined control of the heat thereby generated.
In another embodiment of this second general configuration, in the example illustrated in
Advantageously, as can be seen in
Due to the sheet being openwork, the presence of the sheet 40 does not alter the continuity of matter within the single layer 32.
The sheet 40 includes a matrix, which forms the main component of the sheet, as well as the components 34 per se which are loaded in the matrix.
Advantageously, the matrix is made of PEHD.
According to another embodiment, the matrix may be made of a plastic material more flexible than PEHD.
According to yet another embodiment, the matrix may be made of a composite material. In this case, it may include carbon fibers.
As for the components 34 of the sheet, they are advantageously of the particle type and are thus dispersed in the matrix. They may be silver or carbon particles, such as nanoparticles.
Regardless of the specific materials which are considered, the ratio between the open surface of the sheet 40 and the total surface of the sheet is known as the porosity rate. Advantageously, the porosity rate of the sheet is at least 50%. This configuration helps prevent delamination phenomena within the sheath 26.
The electrical energy based on which the heating components 34 operate is provided by the source of energy 11. This source of energy 11 is configured to cause the electrical energy to flow through the heating components 34 and cause the above generation of heat, typically by Joule effect.
The source of energy 11 may take the form of a battery. Alternatively, and preferably, this source of energy 11 includes a connection to an electrical grid via which electrical energy is supplied. For instance, this connection includes a transformer adapted to shape the electrical energy provided by the grid into a format adapted for the heating needs of the cable 10 using the components 34.
For instance, the source of energy 11 may be located near an extremity of the cable 10.
It should be noted that the cable 10 may include a plurality of such sources 11, which can be seen as various components of an energy supply apparatus of the cable 10.
The source of energy 11 may be coupled to electrical paths which stretch along the longitudinal direction of the cable, which include one or more electrical conductors, which are configured to supply the components 34 with the electrical energy provided by the source(s) of energy 11. For example, the electrical paths include electrodes 39 which are inserted in the matter of the sheath 26, as illustrated in
Advantageously, the electrical paths are separated from the tendons by at least one wall. The wall is in particular configured to protect the electrical paths from any damage that may otherwise occur during the insertion of the tendons of the bundle within the sheath 26. Advantageously, this wall also acts as a thermal barrier. Optionally, a further thermal barrier may be added between the wall and the sheath.
Advantageously, when the heating components 34 are arranged as one or more wire 38, the electrical paths may not include electrodes 39. Indeed, in that case, the electrical paths include by the wire(s) 38 itself. In other words, the wire 38 is directly supplied with the electrical energy by the source(s) 11.
A method of manufacturing the sheath 26 will now be described in reference to the Figures, in particular to
In a general sense, the method comprises forming the sheath 26 from its material.
During this formation, the heating components 34 are arranged within this material, where they can be later used to heat at least the outer surface 30 of the sheath 26 so as to prevent ice, snow, rime or frost from forming thereon or remove ice, snow, rime or frost from the outer surface 30 of the sheath 26.
In effect, to that end, the heating components 34 are introduced into the material or a precursor of the latter.
In more details, during the manufacturing, the material is at least shaped, and optionally transformed as well from a precursor, for instance through a polymerization process.
In reference to
Then, in a following step 52, the material and the resistive components 34 are extruded. In effect, they are heated and given the desired shape using an adapted piece of equipment, which is for instance known per se. The sheath 26, and advantageously, the various longitudinal segments thereof, is then formed.
This process is carried out for each longitudinal segment of the sheath if they are initially separate. Alternatively, this is done for the entire length of the sheath if it is formed to be integral right from the start.
In an optional step 55, which occurs if the sheath is not produced as an integral member in the previous step, the longitudinal segments of the sheath are assembled together to form the sheath 26.
In reference to
In a first embodiment of this configuration, in a step 51, a first part of the layer 32 which does not comprise the portion 36 is first formed, for instance by extrusion. For instance, a first internal cylindrical portion of the layer 32 which is not to include the components 34 is made.
In a step 53, the portion 36 is then coupled to the part so-obtained.
In a first way of proceeding, to that end, the portion (or portions) 36 is formed directly onto this part of the layer obtained in step 51. For instance, it is then formed by extrusion. Due to the heat of the portion 36, its material fuses together with that of the part obtained beforehand. In some embodiments, a dedicated heating of this part may be carried out, for instance if its temperature is below a certain predetermined value.
In a second way of proceeding, the portion 36 is initially made then placed onto the part obtained in step 51.
The portion 36 may be made by extrusion, for instance along the process described in reference to
It should be noted that the core material of the portion 36 may be different from that of all or part of the rest of the layer 32. For instance, any plastic material may be used, such as a plastic material more flexible than PEHD.
Once the portion 36 has been placed onto the part obtained beforehand, the assembly obtained may optionally be heated so as to cause the portion 36 to fuse with to the part made beforehand at least in part. Advantageously, it is then made integral entirely with this part if the assembly is to form the entirety of the considered longitudinal segment of the sheath (or the entire sheath), i.e. if the assembly defines the entire thickness of the corresponding segment/of the sheath.
Regardless of the way of proceeding which is employed, if the assembly does not define the entirety of the considered segment of the sheath or of the entire sheath, the remaining part of the segment (or sheath) is then coupled to the assembly so that its material is made integral therewith.
For instance, this is done by extrusion, whereby this remaining matter is extruded directly onto the assembly.
In optional step 55, if the steps above were carried out for each longitudinal segment, the segments are assembled together to form the sheath.
In a second embodiment of this configuration, the portion 36 is made simultaneously with the rest of the layer 32, whereby their respective materials of these parts fuse together directly. For instance, this is done by co-extrusion, whereby the different parts of the layer are extruded simultaneously in a superposed manner.
The extrusion of the portion 36 itself typically includes the process of mixing the base material of the layer 32 with the components 34, as detailed in reference to
In another embodiment of the manufacturing of the sheath, for components 34 of the second general configuration, a first thickness of the sheath is made, for instance by extrusion, the structure (wire(s)s or sheet(s)) defined by the heating components 34 is arranged thereon, e.g. the sheet 40 or one or more wires 38, and the rest of the thickness of the layer 32 is then made on top thereof, for instance by extrusion (possibly co-extrusion if different materials are to be present in this remaining thickness).
The structure in question itself is for instance made beforehand. For instance, for a sheet 40, the matrix is loaded with the components. As for wires, they are made by any known process, then wound around the first thickness of the sheath.
It should be noted that these embodiments may be hybridized. For instance, a subassembly formed by the portion 36 and a first radial portion of the sheath may be formed in a given manner, this subassembly then being coupled to the remaining part of the sheath (or segment thereof), for instance by co-extrusion.
The invention presents several advantages.
It does not require the use of a costly mechanic-based device which furthermore tends to scratch the outer surface of the sheath. In addition, it is efficient energy-wise, and cost-efficient as well.
Moreover, as the heating components are themselves protected from the environment as they are within the matter of the sheath, the technical solution remains viable over prolonged periods of time without any heavy maintenance.
Further embodiments of the invention are envisaged.
In particular, in the description above, the various types of heating components 34 have been depicted as somewhat exclusive embodiments. In an obvious manner, they can however be combined.
For instance, the sheath may include particle-type components 34 dispersed in the matter of the sheath, as well as one or more sheet and/or electrical wire.
The manufacturing process of the sheath may then be formed by hybridizing the corresponding embodiments above.
Regarding the embodiments of the manufacturing process, they can be combined. For instance, a given process is implemented for some longitudinal segments of the sheath, another process is implemented for some other segments, and so on.
This application is a National Stage Application of International Application No. PCT/IB2017/001357, filed on Sep. 29, 2017, which is hereby incorporated by reference in its entirety for all purposes as if fully set forth herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2017/001357 | 9/29/2017 | WO | 00 |
