Duct element for a structural cable, and construction work equipped with the duct element

Abstract

The duct element is for forming part of a duct around a structural cable with a gap between a periphery of the structural cable and an inner surface of the duct. The duct element comprises a wall extending in a longitudinal direction and spacers protruding from the inner face of the wall by a first height. The first height is lower than an average thickness of the gap between the periphery of the structural cable and the inner surface of the duct. The duct element is suitable for assembling a duct around a structural cable of a construction work, such as a stay cable.

Description

DUCT ELEMENT FOR A STRUCTURAL CABLE, AND CONSTRUCTION WORK EQUIPPED WITH THE DUCT ELEMENTBACKGROUND

[0001] The present document relates to structural cables used in construction works, and more particularly to duct elements that may be installed around structural cables such as stay cables.

[0002] Certain structural cables are disposed within ducts. A main role of such a duct is often to protect the load-bearing armatures of the cable from being exposed to the elements such as wind, rain, heat and cold. The duct also has an aesthetic role, to provide a smooth and elegant aspect to the cables.

[0003] The duct defines a volume around the armatures that may be used to incorporate one or more additional functions in the structural cable. See, e.g., WO 2018 / 142174 A1 . Such additional functions may include structural functions (e.g. dampening, antivibration), thermal functions (e.g. heating to prevent ice formation), deicing functions (see, e.g., WO 2020 / 229867 A1 ), lightning protection functions, electrical functions and lightingfunctions.

[9004] It has become popular to install lighting systems on stay cables. The lighting system is typically mounted on a duct or sheath disposed around the cable. For aesthetic and aerodynamic reasons, it is desirable that the light fixtures do not form significant protrusions on the outer profile of the cable.

[0995] Sometimes, the lighting system is added when retrofitting existing structural cables. For example, the stay cables of the Shangdi bridge, in China, were equipped with sleeves incorporating LED lamps to provide an ornamentation of the landscape around the bridge. See “Research on Difficult Problems in Landscape Lighting Design of Shangdi Cable-stayed Bridge of Beijing-Xinjiang Expressway in Beijing”, LI Li and GUAN Peng, Railway Standard Design, Vol. 58, No. 8, August 2014, pp. 138-140.

[9606] WO 2018 / 020289 A1 discloses a dual sheath for a stay cable, with an inner sheath having the traditional function of protecting the metallic armatures forming the load-bearing part, an outer sheath to be exposed to the environment and a gap between two sheaths. Light modules are disposed in the gap and radiate light through apertures formed in the outer sheath.

[9007] The lighting function may be designed from the outset, together with the sheath that is installed around the load-bearing part of the cable. In this case, it is generally not suitable for retrofitting existing stay cables.

[0006] Installing a duct around an existing cable may be considered to add one or more functions such as those mentioned above. However, the installation of the duct maycause problems. It must be done according to an efficient process that avoids any damages to the existing cable or the functional elements added thereto.SUMMARY

[8999] There is provided a duct element for forming part of a duct around a structural cable, with a gap between a periphery of the structural cable and an inner surface of the duct. The duct element comprises a wall extending in a longitudinal direction and spacers protruding from the inner face of the wall by a first height. The first height is lower than an average thickness of the gap between the periphery of the structural cable and the inner surface of the duct.

[0910] When installing the duct element around the structural cable, the spacers ensure that a proper gap is maintained between the duct element and the periphery of the cable. Still, the spacers do not provide a tight fitting of the duct around the cable (or the protective sheath thereof). Therefore, the duct is allowed to slide smoothly along the cable without causing problems to any equipment present in the gap.

[9011] Depending on the weather conditions, the duct may be exposed to higher or lower temperatures than the rest of the structural cable, and thus the thermal expansion behavior of the components can be different. The configuration of the spacers makes it possible to absorb differences in their thermal expansion.

[8912] In an embodiment, each spacer comprises an elongated contact region having the first height and extending along the longitudinal direction, and curved end regions on both sides of the contact region. A height of the curved end regions is progressively reduced from the first height away from the contact region.

[9013] Embodiments of the duct element further comprise at least one functional unit attached to the wall and protruding from the inner face of the wall by a second height lower than the first height. The at least one functional unit may comprise a light fixture. The wall of the duct element may have at least one aperture through which the at least one functional unit radiates light.

[8914] While the wall of a duct element may cover its full circumference, it may be convenient to have the wall span only an angular sector of at most 180°. Then several duct elements will be assembled around the structural cable. The wall may have longitudinal edges configured for assembling the duct element with at least one other duct element when forming the duct. The at least one other duct element may comprise a wall having identically configured longitudinal edges. In particular, the duct element may comprise a first coupling part along a first longitudinal edge of the wall and a second coupling part along a second longitudinal edge of the wall. The first and second coupling parts correspond to each other such that, when assembling the duct element with an adjacent duct element whose wall has identically configured longitudinal edges to formthe duct, the first coupling part snap fits with the second coupling part of the adjacent duct element. Such fitting of the first coupling part of the duct element with the second coupling part of the adjacent duct element may allow relative sliding of the duct element and the adjacent duct element along the longitudinal direction.

[9815] Where the angular sector spanned by the wall of the duct element is 180°, the duct element may be assembled, along the longitudinal edges, with another duct element of which the wall has the same shape.[S01G] In an example, the wall of the duct element has a semi-cylindrical shape, and it is provided with spacers separated angularly by an angle in a range of 70° to 110°.

[0017] The spacers may have a length in a range of 5 to 80 centimeters along the longitudinal direction where the duct element has a length of at least 3 meters.

[9018] In an embodiment, the wall of the duct element includes voids within the wall thickness.

[0019] Another aspect of the present disclosure is about a construction work comprising a structural cable and a duct arranged around the structural cable with a gap between a periphery of the structural cable and an inner surface of the duct. The duct comprises an assembly of duct elements as mentioned above.

[0020] The duct may comprise a plurality of duct segments each made of at least two duct elements, the duct segments being welded to each other at longitudinal ends thereof.

[0021] Embodiments of the construction work further comprise a locking system arranged at an end portion of the duetto prevent rotation of the duct around the structural cable. That end portion of the duct may be connected to at least one transition tube fixed to an anchoring device of the structural cable, the locking system being disposed between the transition tube and the duct. The at least one transition tube may comprise an anti-vandalism tube.BRIEF DESCRIPTION OF THE DRAWINGS

[0822] Fig. 1 is a very schematic side view of a stay cable.

[0823] Fig. 2 is a perspective view of an example of light fixture.

[0824] Figs. 3-5 are perspective views showing components of the light fixture of Fig. 2 being assembled.

[0625] Fig. 6 is a perspective view illustrating how the light fixture of Fig. 2 may be mounted on a portion of a duct.

[9026] Fig. 7 is a perspective view of the light fixture once mounted on the portion of the duct.

[9027] Fig. 8 is a cross-sectional view of the light fixture mounted on the portion of the duct.

[0028] Fig. 9 is a longitudinal view of a structural cable equipped with a lighting system.

[0029] Fig. 10 is a perspective view of an assembly of a duct element and a few light fixtures.

[0030] Fig. 11 is a cross-sectional view of a pair of duct elements to be assembled.

[0031] Fig. 12 is a cross-sectional view of another embodiment of a duct element.

[0032] Fig. 13 is an enlarged cross-sectional view illustrating how to assemble duct elements as shown in Fig. 12.

[8033] Fig. 14 is a longitudinal view of a duct element.

[8834] Fig. 15 is a partial cross-sectional view of the duct element of Fig. 14.

[8035] Fig. 16 is a perspective view of a lower portion of a stay cable.

[0036] Fig. 17 is a cross-sectionalview of the lower portion shown in Fig. 16.DESCRIPTION OF EMBODIMENTS

[9637] Fig. 1 shows a structural cable 10 that may be equipped with light fixtures 15 according to an embodiment.

[0638] The cable 10 is, for example, a stay extending along an oblique path between first and second parts 12, 14 where it is anchored using respective anchoring devices 16, 18. The stay cable shown is used to suspend the second part 14 (e.g., a bridge deck) from the first part 12 (e.g., a pylon), or to stabilize a tall structure forming the first part 12 from the ground or some lower structure forming the second part 14. It will be appreciated that the lighting systems presented here are applicable to other types of structural cables.

[9639] The stay cable 10 shown in Fig. 1 comprises a load-bearing part 22 which typically includes tendons 24, best seen in Figs. 9 and 16, disposed parallel to each other, and contained in a collective sheath 26. For example, the tendons 24 may be steel strands each protected by a substance such as grease or wax and individually contained in a respective plastic sleeve. The collective sheath 26 forms a protective cover for the tendons 24. It is made of plastic material such as high-density polyethylene (HOPE), and internally defines a cavity running along the length of the cable 10 and within which the tendons 24 are arranged. The cross-section of the sheath 26 is typically circular. Other shapes, e.g. polygonal, elliptical, etc., are possible. The cable 10 may have a length of upto several hundred meters. The load-bearing part 22 may include a few tens of tendons 24.

[9040] The stay cable 10 is equipped with a lighting system which includes the light fixtures 15 mounted on a duct 20.

[0041] There may be large numbers of light fixtures 15 on the stay cables of the structure. The light patterns that may be generated with the lighting system are selected by the project owner or architect based on the desired visual effects. This determines the number of light fixtures 15, their locations on the ducts 20 of the different stay cables of the structure, their light intensity and colors, etc.

[0042] The duct 20 is disposed around the stay cable 10 consisting of the bundle of tendons 24 fitted with its protective sheath 26 (if any). An annular gap G is present between the inner surface of the duct 20 and the periphery of the structural cable 10, i.e. the outer surface of the protective sheath 26. Typically, the protective sheath 26 has a circular cross-section, and so has the duct 20. It is desirable to keep the gap G relatively thin, preferably with a thickness smaller than 20% of the diameter of the stay cable 10.

[8043] The duct 20 may have dimples or helical ribs formed on its outer surface, to mitigate the combined effects of rain and wind. Such arrangement to reduce weather- induced vibrations of stay cables is well known in the art.

[0044] An example of light fixture 15 is illustrated in Figs. 2-5. It includes a cover 30, a light module 40 and a support member 50.

[0045] The cover 30 is in the form of a plate having a curved shape. It may be made of a corrosion-resistant metal such as aluminum. An aperture 31 is formed centrally in the cover 30. When mounting the light fixture 15 on a portion of the duct 20 (Fig. 6), the aperture 31 of the cover 30 is aligned with an aperture 21 which is formed in the wall 23 of the duct 20. In the example illustrated in Fig. 6, the alignment of the apertures 21 , 31 is along a radial direction A of the duct 20.

[9046] The cover 30 has holes 33 near its periphery to receive screws 34 used to secure the light module 15 to the duct 20. In the illustration, the cover has a generally rectangular shape and four holes 33 near its corners. To install the light fixture 15, four screws 34 are inserted into those holes 33 and in four corresponding holes 35 formed in the duct 20 around the aperture 21. The screws 34 engage threaded holes 36 formed in mounting members 32 having an elongated shape and disposed at the inner side of the duct 20. There may be a pair of mounting members for each light fixture 15, in the form of two rods 32 disposed longitudinally on both sides of the aperture 21 .

[9047] Each rod 32 may be preinstalled in the duct 20 using screws 44inserted into holes 45 formed through the wall 23 of the duct 20 near the aperture 21 between the holes 35 used to attach the light fixture 15. The screws 44 are inserted from the outside into the holes 45 and they engage respective threaded holes 46 provided in the rods 32 betweenthe threaded holes 36 used to attach the light fixture 15. The holes 45 of the duct 20 taper outwardly so that the heads of the screws 44 do not protrude at the outer surface of the duct 20. The heads of the screws 44 are overlapped by the cover 30 once the light fixture is in place.

[9848] The curvature of the inner surface of the cover 30 matches that of the outer face of the duct 20. Thus, the cover 30 does not form a substantial protrusion when it is installed on the duct. As shown in Figs. 2 and 5-9, the periphery of the cover 30 has a beveled or rounded edge to avoid steps at the surface of the duct 20. It is also possible to provide a recessed portion in the thickness of the wall 23 of the duct around the aperture 21 , to receive the cover 30 so that it is flush with the outer face of the duct 20 once the light fixture is in place.

[9849] The light module 40 is disposed at the rear, concave side of the cover 30. Its front part is housed in the aperture 31 of the cover 30, so that light will be radiated from the apertures 21 and 31 once the light fixture 15 is in place on the stay cable 10.

[0050] The support member 50 may be made of a piece of molded material, for example HDPE. It comprises a recess 52 configured to receive and hold the light module 40. At the upper edges of the recess 52, the support member 50 has two flaps 53 extending outwardly and shaped to be in contact with the inner face of the cover 30 on both sides of the aperture 31 . Corresponding holes 38, 58 are formed in the cover 30 and in the flaps 53 in order to secure the support member 50 to the cover using screws 39 and nuts 59. As best seen in Fig. 8, the screws 39 are short and the nuts are accommodated in the holes 21 within the thickness of the duct 20.

[8951] Power supply lines 42A-B are connected to the light module 40 of the light fixture 15. The power supply lines 42A-B may be provided together with the light modules 40 or separately. As shown in Fig. 3, the power supply lines 42A-B may emerge from outlets 48A-B formed in the waterproof casing of the light module 40. Each power supply line 42A-B extends between the light module 40 and a respective coupling part 43A-B located out of the support member 50 (see Fig. 10). The coupling parts 43A and 43b are complementary, thus allowing several light fixtures 15 to be mounted and supplied with power via the interconnected coupling parts 43A-B.

[8052] The support member 50 of the light fixture 15 comprises two ports 55A-B receiving the power supply lines 42A-B. The ports 55A-B are oriented parallel to the longitudinal direction of the duct 20, and diametrically opposite to each other, to receive the outlets 48A-B and guide the power supply lines 42-A-B outside the support member 50. Each port 55A, 55B has an upper part which is open to receive the power supply line.[Q853] Figs. 3-5 illustrate steps for assembling a light fixture 15. First, the light module 40 is brought towards the top part of the support member 50. The light module 40 is pressed into the support member 50 (thick arrows in Fig. 3). The outlets 48A-B of the power supply lines cause the ports 55A-B of the support member to flex open and thenclose again to snap fit the light module in the support member 50 (Fig. 4). Afterwards, the cover 30 is brought and fixed to the support member 50 by means of the nuts 59 and the screws 39 inserted into the holes 38 and 58 (thick arrows in Fig. 5).

[9654] Many light fixtures 15 can be produced in this manner, for example thousands of light fixtures to be installed on a cable-stayed structure. If different models of light modules are used in the installation, different molds are used to make support members adapted to the shape and dimensions of the different models.

[6955] In the embodiment discussed below, the duct 20 is made by assembling several identical duct elements 60. Each duct element 60 has a wall 23 extending in the longitudinal direction over a length of typically 3 m or more, for example 5 to 10 m. The cross-section of the duct 20 comprises a number N of duct elements (N > 2). The wall 23 of the duct element 60 thus spans over an angular sector a = 360° / N of at most 180°, i.e. a = 180° if N = 2, a = 60° if N = 3, etc.

[9056] The drawings illustrate the most typical case where N = 2 and an angular sector of a = 180° is spanned bya duct element 60. While it is advantageous to provide such duct elements 60 whose walls 23 are identically shaped, for manufacturing simplicity, it will be noted that different shapes are possible too.

[9057] Fig. 10 shows a duct element 60 which has been equipped with light fixtures 15, forming an assembly according to the present disclosure. Each light fixture 15 is at the level of an aperture 21 formed in the wall of the duct element 60. The attachment of the cover 30 on the outer face of the duct element 60 makes it possible to have a significant proportion of the light module 40 and of the support member 50 confined within the wall thickness, which is advantageous to limit the thickness of the gap G.

[9058] The holes 21 formed in the wall 23 of the duct element 60 may have a generally circular shape with a diameter sufficient to accommodate the support members 50 of the light fixtures 15. Figs. 6, 9 and 10 show extensions 28 of the holes 21 on both sides thereof along the longitudinal direction. The extensions 28 allow the power supply lines 42-A-B to bend smoothly at the exit of the support member 50. The holes 21 and their extensions 28 are overlapped by the covers 30 of the light fixtures 15 so that they are not apparent once the light fixtures 15 are in place.

[9059] Orienting the ports 55A-B diametrically opposite to each other along the longitudinal direction, and disposing likewise the extensions 28 longitudinally on both sides of the holes 21 , provides an optimal configuration to house the cables 42A-B and their connectors within the relatively narrow gap G.

[9060] It also facilitates the removal and replacement of a light fixture if maintenance is needed. The light fixture 15 can be removed from the outer side of the duct 20, i.e. the convex side of the duct element 60, by removing the screws 34 and lifting the cover 30. Some length of the power supply lines 42A-B can then be pulled to disconnect them fromthose of the adjacent light fixtures. The rods 32 remain in place within the duct 20 and so a new light fixture can be installed to replace the previous one.

[0061] In an alternative embodiment of the light fixture 15 (not shown in the drawings), the support member 50 comprises only one port receiving the two power supply lines 42- A-B. In that case, it is possible to provide only one (broader) extension 28 of the hole 21 .

[0062] Duct elements as shown in Fig. 10 can be equipped with their light fixtures in the factory, and then transported to the construction site for installation on stay cables 10. Thus, a minimum number of process steps need to be performed on the construction site, which is advantageous from the point of view of costs. It also reduces the need to block the traffic to carry out the retrofitting.

[0063] The duct elements are assembled with each other around a stay cable 10 once they are received at the construction site. The longitudinal edges of a duct element 60 are configured for assembling it with a paired duct element 60’ when forming the duct 20 around the stay cable 10. The walls 23 of the paired duct elements 60, 60’ have the same dimensions. The shapes of their longitudinal edges are also the same. Thus, the duct elements 60, 60’ can be produced in series to equip the construction work. They are, for example, produced by an extrusion process.[6G64] In the example shown in Fig. 11 , a duct element 60, 60’ has a longitudinal edge shaped as a male coupling part 62, and the other longitudinal edge shaped as a female coupling part 63. The male and female coupling parts 62, 63 extend over the whole length of the duct elements 60, 60’. On the inner side of the wall 23 and along the longitudinal edges, the male coupling part 62 has a projection while the female coupling part 63 has a hook portion that can flex and engage the projection to provide snap fitting of the paired duct elements 60, 60’. In this example, the wall 23 of the duct elements 60, 60’ has no voids.

[9665] In the alternative embodiment illustrated in Figs. 12 and 13, the wall 23 of each duct element has voids 66. The wall 23 comprises an outer layer 67 and an inner layer 68 concentrically positioned and separated from the outer layer 67 by stiffeners 69 which extend radially and longitudinally. Such a configuration of the wall 23 may be obtained by extruding plastic. The extrusion process can also define the matching shapes of the longitudinal edges of the duct elements. In the example of Figs. 12 and 13, the male coupling part 62 along one longitudinal edge has an arrowhead-shaped cross-section that remains within the thickness of the wall 23, while the female coupling part 63 along the other longitudinal edge comprises a complementary recess that has the same width at the voids 66 with a narrow channel to receive the arrowhead-shaped male coupling part 62 in a snap-fitting engagement.

[0066] Duringthe installation, paired duct elements are brought together around a stay cable 10 and snap-fitted together. This step is carried out near the lower end of the stay cable. The duct segmentthus formed is pushed upwardly to slide alongthe stay cable 10.

[9067] The embodiment of Figs. 12 and 13 allows the paired duct elements 60 to slide along each other, which may facilitate the installation of the duct 20 around the stay cable 10 in certain cases. For example, a front end of the male coupling part 62 may be introduced into the rear end of the female coupling part 63 of the paired duct element to initiate the assembly around the stay cable 10. Then, by pushing one of the paired duct elements towards the other, causing them to slide relatively to each other along the longitudinal direction of the stay cable, the remaining length of the male coupling part will be progressively inserted into the female coupling part of the paired duct element. Once the assembly of the paired duct elements is completed, the duct segment is pushed upward, and the next segment form can be assembled in a similar manner.[06SS] Consecutive segments of the duct 20 can be butt-welded at their longitudinal ends using a conventional hot mirror technique.

[8869] Figs. 10 and 11 show spacers 70 protruding from the inner face of the wall 23 of the duct. The spacers 70 may be welded to the inner face of the wall 23 or fixed using screws or some other type of connectors.

[9970] The spacers 70 are provided to ensure that a sufficient gap G is maintained between the inner face of the duct 20 and the outer face of the sheath 26 of the stay cable so as to accommodate the light fixtures and the connectors formed by interconnecting the coupling parts 43A-B. As mentioned earlier, it is desirable to keep the gap G relatively thin.

[8071] In the process of installing the duct 20 around the stay cable 10, the duct elements or segments should slide longitudinally. However, shocks or friction with the lighting system during installation should be minimized, especially when the duct elements are caused to slide. The trajectory of a stay cable is not a straight line but a catenary curve due to its own weight (see Fig. 1 ). After a few segments of the duct have been assembled and pushed upwards, it becomes more and more difficult to push the other segments that are assembled next.

[8072] Hence, while a spacer function is useful, it is desirable to avoid a firm coupling of the duct 20 with respect to the stay cable 10 or its protective sheath 26.

[8873] To address this issue, the spacers 70 protruding from the inner face of the wall 23 of the duct 20 have a height hi which is less than the average thickness of the gap G between the periphery of the stay cable 10 and the inner surface of the duct 20 (Figs. 10- 11 and 14-15).

[9074] In the case where the sheath 26 and the duct 20 have circular cross-sections, the thickness of the gap G may be defined as the difference Ar between the inner radius of the duct 20 and the outer radius of the sheath 26. Once the duct 20 is installed on the inclined stay cable 10, however, the gap is thicker below than above the sheath 26 because of the weight of the duct 20 and the light fixtures 15. Still the average gapthickness is Ar. For other geometries of the duct 20 or sheath 26, the spacers 70 should also be dimensioned with the height hi less than the average thickness of the gap G.

[9075] The spacers 70 shown in Figs. 10 and 14-15 do not extend continuously over the whole length of the duct elements 60. They have a certain length along the longitudinal direction of the duct, for example 5 to 80 cm, which is better to preserve the bending flexibility of the duct 20.

[8576] In the illustration, the spacers 70 have an elongated contact region 71 representing about a third of their length and two curved end regions 72 on both sides of the contact region 71 along the longitudinal direction. The height hi of the spacer 70 is the height of the central region 71 . Startingfrom the central region 71 along the longitudinal direction, the height of the end regions 72 is progressively reduced from the height hi. This provides a smooth transition between the regions 71 and 72 and gives to the spacers 70 the general shape of a ski.

[9077] That shape of the spacers 70 is suitable for them to slide smoothly on the sheath 26 of the stay cable 10 when the duct 20 is installed. The height hi of the spacers 70 is larger than the height h2(indicated in Figs 8 and 10) by which the light fixtures 15 protrude at the inner face of the wall 23. Thus, the spacers 70 protect the light fixtures 15 from shocks or friction when the duct 20 slides alongthe stay cable 10.

[0078] In Figs. 10, 11 and 14, a duct element 60 having a semi-cylindrical shape (a = 180°) comprises two spacers 70 disposed symmetrically with an angular separation P between them. The angle is in a range of 70° to 110°. It may be a right angle (90°). Once the two duct elements are assembled on the stay cable 10, the duct segment thus formed bears on the sheath 26 by two of the four spacers 70 of the provided in its cross-section and it can slide at the contact regions 71 of those two spacers 70.[S079] The interval between two other spacers 70 and the sheath 26 is also useful to allow the sheath 26 and the duct 20 to expand differently when there are substantial temperature variations in the environment of the cable-stayed construction.

[9088] There can also be more or less than four spacers 70 in the cross-section of the duct 20. Additionally, the spacers 70 may be offset with respect to each other along the longitudinal direction.

[8881] Fig. 16 shows an end portion of the duct 20 and the stay cable 10. Reference is made here to the lower portion at the second part 14 of the construction, e.g. bridge deck. A similar arrangement may also be provided at the upper portion.

[0082] From the anchoring device 18, the stay cable 10 passes successively through transition tubes including a formwork tube 80, a guide tube 82 and an anti-vandalism tube 84 which covers the guide tube 82 at the transition with the duct 20. The transition tubes 80, 82, 84 are fixed to the second part 14. Fig. 16 has a torn off part to expose the tendons 24, the sheath 26, as well as electrical cables 86 that extend in the tubes 80 and 82 to beconnected to the power supply lines of the light fixtures 15. Before the anchoring device 18, the cables 86 emerge to be connected to a power source.

[0083] In order to prevent rotation of the duct 20 around the structural cable 10, a locking system 90 is arranged at the end portion of the duct 20. An example of such locking system, or anti-rotation system, is illustrated in Fig. 17. The anti-rotation system is useful to ensure the proper orientation of the light patterns generated by the light fixtures 15. For example, if the light fixtures 15 are designed to radiate horizontally on both sides of the stay cables, even a small rotation of the duct could significantly change the visual effects produced by the lighting system.

[9684] In the example of Fig. 17, the anti-rotation system 90 comprises notches (or holes) 91 formed in the end portion of the duct 20 through its wall 23, and lugs 92 inserted in the notches 91 . The lugs 92 are attached to one of the transition tubes, typically the anti-vandalism tube 84, using bolts 94.

[9085] It will be appreciated that the embodiments described above are illustrative of the invention disclosed herein and that various modifications can be made without departing from the scope as defined in the appended claims.

Claims

CLAIMS1 . A duct element for forming part of a duct (20) around a structural cable (10), with a gap (G) between a periphery of the structural cable and an inner surface of the duct, the duct element (60) comprising: a wall (23) extending in a longitudinal direction; and spacers (70) protruding from the inner face of the wall (23) by a first height (h 1 ), wherein the first height (hi) is lower than an average thickness of the gap (G) between the periphery of the structural cable (10) and the inner surface of the duct (20).

2. The duct element of claim 1 , wherein each spacer (70) comprises: an elongated contact region (71 ) havingthefirst height (hi) and extendingalongthe longitudinal direction; and curved end regions (72) on both sides of the contact region (71 ), and wherein a height of the curved end regions (72) is progressively reduced from the first height (hi) away from the contact region (71 ).

3. The duct element of any one of the preceding claims, further comprising at least one functional unit (15) attached to the wall (23) and protruding from the inner face of the wall by a second height (h2) lower than the first height (hi).

4. The duct element of claim 3, wherein the at least one functional unit comprises a light fixture (15).

5. The duct element of claim 4, wherein the wall (23) has at least one aperture (21 ), and wherein the at least one functional unit (15) is arranged to radiate light through the at least one aperture (21 ).

6. The duct element of any one of the preceding claims,wherein the wall (23) spans over an angular sector of at most 180°, and wherein the wall (23) has longitudinal edges configured for assembling the duct element (60) with at least one other duct element (60’) when forming the duct (20), the at least one other duct element comprising a wall having identically configured longitudinal edges.

7. The duct element of claim 6, comprising a first coupling part (62) along a first longitudinal edge of the wall (23) and a second coupling part (63) along a second longitudinal edge of the wall (23), wherein the first and second coupling parts (62, 63) correspond to each other such that, when assembling the duct element (60) with an adjacent duct element (60’) whose wall has identically configured longitudinal edges to form the duct (20), the first coupling part (62) snap fits with the second coupling part (63) of the adjacent duct element.

8. The duct element of claim 7, wherein the fitting of the first coupling part (62) of the duct element (60) with the second coupling part (63) of the adjacent duct element (60’) allows relative sliding of the duct element and the adjacent duct element alongthe longitudinal direction.

9. The duct element of any one of claims 6 to 8, wherein the angular sector is 180° and the duct element (60) is assembled with another duct element (60’) alongthe longitudinal edges, the walls (23) of the duct element and of the other duct element having the same shape.

10. The duct element of claim 9, wherein the wall (23) has a semi-cylindrical shape and is provided with spacers separated angularly by an angle (P) in a range of 70° to 110°.11 . The duct element of any one of the preceding claims, wherein, alongthe longitudinal direction, the spacers (70) have a length in a range of 5 to 80 centimeters and the duct element (60) has a length of at least 3 meters.

12. The duct element of any one of the preceding claims,wherein the wall (23) includes voids (66) within the wall thickness.

13. A construction work, comprising: a structural cable (10); and a duct (20) arranged around the structural cable with a gap (G) between a periphery of the structural cable and an inner surface of the duct, wherein the duct (20) comprises an assembly of duct elements (60) as claimed in any one of the preceding claims.

14. The construction work of claim 13, wherein the duct (20) comprises a plurality of duct segments each made of at least two duct elements (60), and wherein the duct segments are welded to each other at longitudinal ends thereof.

15. The construction work of any one of claims 13 and 14, further comprising a locking system (90) arranged at an end portion of the duct (20) to prevent rotation of the duct around the structural cable (10).

16. The construction work of claim 15, wherein the end portion of the duct (20) is connected to at least one transition tube (80, 82, 84) fixed to an anchoring device (18) of the structural cable (10), and wherein the locking system (90) is disposed between the transition tube and the duct.

17. The construction work of claim 16, wherein the at least one transition tube comprises an anti-vandalism tube (84).

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