Patent Publication Number: US-2023148435-A1

Title: Damping arrangement for a cable

Description:
The invention relates to a damping arrangement for a cable extending in a tensioned manner from an anchorage, said damping arrangement comprising at least one damping device. 
     Such damping devices may, for example, be used for cables for suspending and/or supporting structural units of super-ordinate structures, e.g. buildings, towers, bridges, and the like. 
     Damping devices for reducing vibrations in cables, e.g. stay cables of cable-stayed bridges, are particularly effective if they are installed as far away as possible from the anchorage of the cable. For example, the damping device may be connected to the cable at a predetermined distance amounting to about 4% of the overall length of the cable. Taking into account that the overall length of the cable may amount to several hundred meters, this will result in the connection point of the damper to the cable being located several meters above the superstructure supported by the cable, e.g. the driving deck of the cable-stayed bridge. As a consequence, the damping devices either have to be very long or they have to be mounted far above the superstructure using an expensive framework, which in addition may reduce the effectiveness of the damping device due to its inherent elastic deformability. Furthermore, such frameworks have considerable aesthetic drawbacks. 
     Damping arrangement of the afore-mentioned time are well-known to those skilled in the art. In particular, reference is made to U.S. Pat. No. 10,081,921 B2. Furthermore, it is referred to U.S. Pat. No. 9,617,697 B2, US 2016/0319499 A1 and EP 1 512 794 B1. 
     In view of the above, it is an object of the present invention to provide an improvement to damping arrangements of the afore-mentioned type. 
     According to the invention, this object is achieved by a damping arrangement for a cable extending in a tensioned manner from an anchorage, said damping arrangement comprising a rigid damping action transfer device which is positively connected to the cable at a predetermined distance from said anchorage, and at least one damping device extending in a damping manner between said damping action transfer device and a constructional element rigidly connected to said anchorage, and connected to said damping action transfer device at a further predetermined distance from said anchorage, said further predetermined distance being shorter than said predetermined distance. 
     According to the invention, the effective connection point, which is relevant for the technical design of the damping arrangement, can still be located far away from the anchorage, namely at the predetermined distance, while the damping device itself is not directly attached to the cable but to the damping action transfer device at a position between the connection point thereof to the cable and the anchorage, namely at the further predetermined distance. Accordingly, the damping device may have a shorter length, and no framework is required. The lack of necessity of providing a framework results in considerably lower costs and an improved aesthetic appearance. Furthermore, the maintenance and/or inspection of the damping device are/is easier due to its better accessibility. 
     In the case of a stay cable, the damping device can also be mounted steeper, i.e. not orthogonal to the cable. It can thus be made even shorter. In addition, an overlap of the base point attachment of the damping device with the neighboring cable can be avoided. 
     A further cost reduction may be achieved, if an element already being a part of the damping arrangement&#39;s design assumes the function of the damping action transfer device. For example, said rigid damping action transfer device may be formed by a rigid transition pipe surrounding the cable adjacent to the anchorage. Such transition pipes are usually surrounding the cable close to the anchorage as a further protection against external influences. 
     For effectively transmitting the damping forces between the cable and the damping action transfer device a force transmitting device may be located between the cable and the damping action transfer device for positively connecting the cable to the damping action transfer device. Although any elastically deformable connection between the cable and the damping action transfer device could reduce the effectiveness of the damping device, it turned out that, according to a simple and cost-effective design, the force transmitting device may include a resilient element adapted and configured to be compressed between two compression plates so as to be expanded in a direction orthogonal to the plate planes of the compression plates, as a resilient element compressed in the afore-described manner shows a sufficient rigidity. The resilient element may, for example, be constituted by a rubber element. 
     Said resilient element may, for example, have an annular shape and/or may be arranged to surround the cable. In this case, the radially inner expanded portion of the resilient element may positively abut against the cable or an element connected thereto, while the radially outer expanded portion of the resilient element may positively abut against the damping action transfer device. 
     For increasing the effectiveness of the positive connection between the cable and the damping action transfer device, it is further suggested that the force transmitting device engages a compacting clamp unit adapted and intended for compacting a plurality of wires and/or strands of said cable to a side-by-side arrangement. By this compacting clamp any, in particular radial, movements of the wires and/or strands of said cable relative to each other may be excluded, thus eliminating any elastic deformability jeopardizing the effectiveness of the force transfer. 
     In order to ensure that the damping device is able to effectively dampen the cable&#39;s vibrations, the damping action transfer device must be able to freely follow the cable&#39;s movements. This may, for example be achieved by pivotably supporting the damping action transfer device at its anchorage end. 
     In case the damping action transfer device is formed by the transition pipe, this may be realized by a resilient ring arranged between the axial end surface of the anchorage end of the transition pipe and a corresponding support surface of the anchorage. 
     Furthermore, the anchorage end of the transition pipe may be in sliding contact with at least one socket element allowing a pivoting movement of the transition pipe around its anchorage end. To this end, the at least one socket element may have a convex surface pointing towards the outer surface of the transition pipe. 
     According to a further embodiment, an angle formed between the at least one damping device and the cable may amount to less than 90°. In this way, the damping device may be arranged steeper than with conventional damping arrangements and thus be shorter. 
     If the damping device were to be connected directly to the cable as in the prior art, an angle different from 90° would cause a longitudinal force on the polyethylene sheath of the strands of the cable, which in turn would lead to a displacement of the compaction clamp. Therefore, in the prior art the damping device is always arranged orthogonal to the cable. Only because of the connection of the damping device with the damping action transfer device according to the invention, it is possible to arrange the damping device steeper and therefore shorter, since the damping action transfer device dissipates the longitudinal force via the anchorage. 
     In order to increase the damping effect, a plurality of damping devices may be connected to the rigid damping action transfer device. 
     Furthermore, the damping devices do not necessarily have to be connected at one and the same further predetermined distance. Rather, at least two damping devices are connected at different further predetermined distances to the rigid damping action transfer device. 
     This allows further specific configurations to be realized. For example, at least two damping devices, when seen along the cable&#39;s longitudinal direction, may be crossing each other between their respective two ends, i.e. extend in analogy to skew lines. In particular, this configuration allows a more effective dampening of lateral vibrations of the cable, i.e. vibrations in a direction orthogonal to both the longitudinal direction of the cable and the vertical direction. 
     According to a further embodiment of the invention, at least one damping device may be formed as one of a passive fluidic damper, a semi-active fluidic damper, a friction damper and an elastomer damper. 
     It should be noted that merely the at least one damping device, the rigid damping action transfer device, and optionally the force transmitting device, constitute elements of the damping arrangement according to the invention, while the cable, the anchorage and the constructional element rigidly connected to said anchorage do not constitute elements of the damping arrangement according to the invention. However, the damping arrangement according to the invention may be used in combination with such cable, anchorage and constructional element. 
    
    
     
       In the following, the present invention will be explained in more detail referring to specific embodiments shown in the attached drawing, in which 
         FIG.  1    shows a partially sectional view of a stay cable equipped with a first embodiment of a damping arrangement according to the present invention; 
         FIG.  2    shows an enlarged view of detail II in  FIG.  1   ; 
         FIG.  3    shows an enlarged view of detail Ill in  FIG.  1   ; 
         FIG.  4    shows a partially sectional view taken according to line IV-IV in  FIG.  1    of a damping arrangement having one damping device; 
         FIG.  5    shows a view similar to  FIG.  4    of a damping arrangement having two damping devices, i.e. of a second embodiment of a damping arrangement; 
         FIG.  6    shows a partially sectional view similar to  FIG.  1    of a stay cable equipped with a third embodiment of a damping arrangement according to the present invention; and 
         FIG.  7    shows a partially sectional view according to line VII-VII in  FIG.  6    of the embodiment of  FIG.  6   . 
     
    
    
       FIG.  1    shows a damping arrangement  100  which is applied to a stay cable  102  of a cable-stayed bridge  104  which is schematically represented by its driving and/or walking deck  106  and the anchorage  108  for the stay cable  102 . The stay cable  102  extends in a tensioned manner from the anchorage  108  to a corresponding anchorage (not shown) of a pylon (not shown) of the cable-stayed bridge  104  so as to contribute to supporting the driving deck  106 . 
     The damping arrangement  100  comprises a damping device  110  and a rigid transition pipe  112  surrounding the cable  102 . 
     At a predetermined distance L 1  from the anchorage  108 , the rigid transition pipe  112  is positively connected to the outer surface of the cable  102 , or to the outer surface of a compacting clamp  114  compacting a plurality of wires and/or strands  116  of the cable  102  to a side-by-side arrangement, to be precise, via a force transmitting device  118 . 
     As may be seen in more detail from  FIG.  2   , the force transmitting device  118  may include a resilient element  120  which is compressed between two compression plates  122 ,  124  so as to be expanded in a direction orthogonal to the plate planes of the compression plates  122 ,  124 . In this way, the radially inner expanded portion of the resilient element  120  may positively abut against the cable  102  or the compacting clamp  114  connected thereto, while the radially outer expanded portion of the resilient element  120  may positively abut against the inner surface of the transition pipe  112 . The resilient element  120  may, for example, have an annular shape and may be arranged to surround the cable  102 . 
     In this way, any vibrational movement of the cable  102  is transmitted to the transition pipe  112 . 
     In order to allow the transition pipe  112  to freely follow vibrational movements of the cable  102 , it is pivotably supported at its anchorage end  112   a . For this purpose, as may be seen from  FIG.  3   , the axial end surface  112   b  of the transition pipe  112  is supported by a resilient ring  126  arranged between the axial end surface  112   b  of the transition pipe  112  and a corresponding support surface  108   a  of the anchorage  108 . Furthermore, an outer surface  112   c  of the transition pipe  112  is slidingly guided in a socket ring  128  having a convex surface  128   a  slidingly abutting against the outer surface  112   c  of the transition pipe  112 . 
     Due to the afore-described design, any vibrational movement of the cable  102  is transferred to a pivoting movement of the transition pipe  112  around its anchorage end  112   a.    
     In order to dampen the vibrational movement of the cable  102 , i.e. the pivoting movement of the transition pipe  112 , the damping device  110  is connected to the transition pipe  112  at a second predetermined distance L 2  from the anchorage  108 , which is shorter than the first predetermined distance L 1 . As a consequence, the effective connection point, which is relevant for the technical design of the damping arrangement  100 , may be located far away from the anchorage  108 , namely at the first predetermined distance L 1 , while the damping device  110  needs not to be directly attached to the cable  102 , but may be attached to the transition pipe  112  at a position closer to the anchorage  108 , namely at the second predetermined distance L 2 . As may be easily understood, due to its rigidity, the transition pipe  112  thus fulfills the function of a damping action transfer device. 
     As may be seen from  FIG.  1   , the damping device  110 , on the one side, and the cable  102  or the transition pipe  112 , respectively, on the other side, form an angle α between them, which amounts to less than 90°. In this way, the damping device  110  can be arranged steeper than with conventional damper arrangements and thus be shorter. 
     As far as the damping device is concerned, several alternative embodiments are conceivable. 
     According to a first alternative embodiment shown in  FIG.  4   , one single damping device  110  may extend between the driving deck  106  and the transition pipe  112 . 
     According to a second alternative shown in  FIG.  5   , two damping devices  110 - 1 ,  110 - 2  may extend between the driving deck  106  and the transition pipe  112 . The two damping devices  110 - 1 ,  110 - 2  may form an angle β between them, which is different from 0°. In this way lateral movements of the transition pipe  112  indicated by arrows L may be dampened as well. 
     While the two damping devices  110 - 1 ,  110 - 2  are attached to the transition pipe  112  at the same predetermined distance L 2  from the anchorage, this needs not necessarily to be the case, as is shown by the third alternative of  FIGS.  6  and  7    for the damping devices  110 - 3 ,  110 - 4 . While damping device  110 - 3  is attached to the transition pipe  112  at a predetermined distance L 2   a  from the anchorage  108 , damping device  110 - 4  is attached to the transition pipe  112  at a predetermined distance L 2   b  from the anchorage  108 , still being shorter than the first predetermined distance L 1 . 
     The different distances L 2   a  and L 2   b  provide for a further flexibility in the design of the damping arrangement  100 . For example, the two damping devices  110 - 3  and  110 - 4 , when seen along the cable&#39;s longitudinal direction A, may be crossing each other between their respective two ends, i.e. extend in analogy to skew lines. This configuration allows an even more effective dampening of lateral vibrations of the cable  102 . 
     Finally, it is to be emphasized that the invention isn&#39;t restricted to a specific type of damper. Rather, at least one damping device may be constituted by a passive fluidic damper or a semi-active fluidic damper or a friction damper or an elastomer damper.