A clamping device, detensioning system and a method thereof for clamping an object such as structural elements or tensioning elements

Abstract

Present invention relates to a clamping device, a detensioning system and their methods thereof for clamping an object, wherein the clamping device (100) comprises a body (20) and a stressing means (40); wherein the body (20) of the clamping device (100) comprises at least two wedge-like elements (22), and structural support elements such as backing elements (21) and / or closing plates (23) for supporting the at least two wedge-like elements (22), wherein the wedge-like elements (22) are housed at least partially within the body (20), arranged next to each other for forming a cavity with an opening for receiving an object (50) to be clamped, wherein the wedge-like elements (22) are movable by the stressing means (40) in at least one degree of freedom relative to each other; wherein the stressing means (40) is either mounted directly on the clamping device (100), or on a stressing chair which in turn is bearing against the body (20) in order to exert a force to the clamping device (100) such that the resulting movement of the wedge-like elements (22) against the surface of the object (50) to be clamped induces a clamping force.

Description

[0001] A clamping device, detensioning system and a method thereof for clamping an object such as structural elements or tensioning elements

[0002] Technical field of the invention

[0003] The present invention relates to the field of civil engineering involving structural elements or tensioning elements such as external post-tensioning tendons, stay cables, guy wires or bridge hangers, which are to be detensioned, demounted or replaced.

[0004] Background of the invention

[0005] Structural elements or tensioning elements of civil engineering structures such as bridges, buildings or towers need to be maintained or replaced from time to time in order to ensure their safety. These pre-tensioned structural elements or tensioning elements need to be detensioned in a controlled manner before being demounted and replaced completely.

[0006] These structural elements are made from a bundle of tensile elements, such as steel wires, strands or bars covered by a corrosion protection material usually with a cementitious base. It is therefore necessary to remove the protection layer before accessing to the tensile elements.

[0007] The usual procedure involves cutting the tensile elements after having transferred the load to a bridging device composed of clamps, auxiliary tensile elements such as post-tensioning bars and hydraulic jacks that allow detensioning in a controlled manner.

[0008] For that purpose, the clamps must be solidly connected to the structural element, withstand the force, and avoid any slippage of the tensile elements. One possible solution consists of installing two or more collars that are tightened against the tensile elements by means of bolts. The tightening force generates a friction that must be bigger than the remaining force of the tensile elements in order to prevent any slippage.

[0009] However, it is not always possible to access all the tensile elements of the tendon and it may not be possible or practical to apply a sufficient tightening force to create the necessary friction with the use of dry friction clamps.

[0010] Patent document EP3808899 A1 discloses a method and a system for detensioning guy lines by incorporating, or replacing with, improved filler material. Specifically, the method consists of removing in one area the sheath and the cement grout covering the guy line and leaving it clean, placing a formwork around it wherein the improved filler material is injected, which enables, once set, having an area with improved strength and adhesion in order to be able to locate thereon clamps at the ends and starting from them yoke-shaped structures joined to each other by post-tensioning bars or tendons, whereon hydraulic cylinders act in order to release the tension from the guy line and pass it to the post-tensioning bars or tendons and thus be able to cut the strands or wires of the guy lines, in order to subsequently relax the hydraulic cylinders in stages until the guy line is completely detensioned.

[0011] Another patent document DE102017201907 A1 discloses a method for de-tensioning tensioning element of a large civil structure such as tendons or stay cables. However, installation of the de-tensioning devices and access to each individual tensioning element may be difficult, in particular when they are surrounded by neighbouring tensioning elements. In addition, the method may be dangerous if some of the tensioning elements are damaged. Moreover, the solution is only suitable to detension certain types of structural elements or tensioning elements such as the one described therein.

[0012] A “window cutting method” is also known in the art for the detensioning of structural elements or tensioning elements of a civil structural. This de- tensioning method consists of providing several windows along the tendon (tension element), where the protecting sheathing and grout surrounding the tensile elements (e.g., strands) are removed. The tensile elements of the tendon (tension element) are then cut by gas torch or remote-controlled diamond wire strand by strand in one or two windows. As the strands are cut, the force in the remaining strands increases and eventually lead to their rupture due to overstress. The sudden rupture of the remaining strands with a high residual force releases an energy which cannot be fully controlled and might cause an impact to the surrounding structure. The impact of the sudden residual force release may be reduced by providing additional damping; however, the force release is not fully controlled and there remains a degree of uncertainty to the implications to the surrounding structure. The above description covers the usual case of a tendon (tension member) formed by a set of individual strands, but it is also applicable to other types of tendons (tension members), e. g. tendons composed of wires or ropes.

[0013] However, it remains several limitations in the above-explained examples. For instance, the apparatuses and methods named above are not only complicated to be set up, as filler materials are required to be introduced to the formworks (either in pre-cast form or in situ injection), the bridges or roads have to therefore be closed for an extended time in order to carry out the maintenance works.

[0014] Therefore, it remains a need to find an improved system and improved method for a fully controlled de-tensioning method and complete force release of the tension element to enable the replacement of structural elements and / or tensioning elements that are being pre-tensioned or pre-stressed.

[0015] Summary of the invention

[0016] In the present invention, one clamping device is proposed in its simplest form, for clamping an object on only one of its sides. Nevertheless, it is also feasible that the clamping device is provided on both sides of the portion of the structural element or the tensioning element to be detensioned. The clamping device and the detensioning system according to the present invention are used to clamp an object without the need to provide a filler material into the clamping device or the detensioning system. Thanks to the wedge-like elements provided at least partially to the body of the clamping device, the force exerted by the stressing means causes the wedge-like elements to move towards the surface of the object to be clamped, thereby inducing a clamping force.

[0017] A first aspect of the invention is therefore to provide a clamping device for clamping an object, wherein the clamping device comprises a body and a stressing means; wherein the body of the clamping device comprises at least two wedge-like elements, and structural support elements such as backing elements, closing plates and / or rotation axis for supporting the at least two wedge-like elements, wherein the wedge-like elements are housed at least partially within the body, arranged next to each other for forming a cavity with an opening for receiving an object to be clamped, wherein the wedge-like elements are movable by the stressing means in at least one degree of freedom relative to each other; wherein the stressing means is either mounted directly on the clamping device, or on a stressing chair which in turn is bearing against the body in order to exert a force to the clamping device such that the resulting movement of the wedgelike elements against the surface of the object to be clamped induces a clamping force.

[0018] A second aspect of the invention is to provide a detensioning system for detensioning a portion of an object to be detensioned, such as a structural element or a tensioning element to be detensioned, comprising

[0019] - At least one clamping device according to any one of the preceding claims, arranged on at least one side of the portion of the object to be detensioned;

[0020] - Two or more stressbars arranged to connect between an anchored structure and the clamping device which is arranged on one side of the portion of the object to be detensioned, or arranged to connect between the clamping devices arranged on both sides of the object to be detensioned;

[0021] - Two or more stressbar hydraulic cylinders, wherein each of the stressbar hydraulic cylinder is either mounted directly on the clamping device, or on a stressing chair which in turn is bearing against the clamping device located on at least one side of the object to be detensioned.

[0022] A third aspect of the invention is to provide a method to clamp an object, comprising the steps of a) Providing an object to be clamped to a cavity of the clamping device according to the invention; b) Exerting a force to the clamping device to clamp the object.

[0023] A fourth aspect of the invention is to provide a method to detension structural elements and / or tensioning elements, such as a structural element or a tensioning element to be detensioned, comprising the following steps: a) Removing of sheath and / or grout covering the portion of the structural element or the tensioning element in case such sheath and / or grout is present, thereby exposing a core element of the structural element of the tensioning element; b) Placing at least one clamping device according to the invention on the exposed core element, wherein the at least one clamping device is positioned on at least one side of the portion of the object to be detensioned if another side of the portion is anchored to an anchored element, or placing the clamping devices in between the portion of the object to be detensioned; c) Joining the one or more clamping devices arranged on at least one side of the portion of the object to be detensioned with at least two stressbars; d) Exerting a longitudinal force to the clamping device until the stressing means reaches approximately the same load carried by the object; e) Cutting the core element of the object to be detensioned; f) Releasing the force of the stressbars. A fifth aspect of the invention is to provide a use of the detensioning system for detensioning a portion of an object to be detensioned, such as a structural element or a tensioning element to be detensioned, without providing a filler material or a pre-cast moulded element to the cavity of the clamping device for filling up the cavity before exerting the clamping force.

[0024] According to an embodiment of the invention, the clamping device is formed by at least two half clamps, wherein the two half clamps are joined together by mechanical fixing means around the object to be clamped. This allows easier insertion of the object to be clamped or its subsequent removal.

[0025] According to an embodiment of the invention, the wedge-like element is formed by a plurality of plates. These plates increases the contact area with the object to be clamped, thereby increasing the gripping force as well as the clamping force.

[0026] According to an embodiment of the invention, the wedge-like element is an integrated element with the body, formed by a plurality of plates, wherein the plates (24) are provided in the same shape and / or size. For instance, the plates may be provided in the same shape but different size, wherein the resulting wedging effect could enhance the clamping force initiated by the stressing means.

[0027] According to an embodiment of the invention, the body is substantially elongated such that the wedge-like element is at least partially accommodated thereto, the thickness of the plate is substantially less than its length, having a thickness of between about 2 mm and 50 mm, more preferably between about 5 mm and 30 mm, or more preferably between about 8 mm and 20 mm. Moreover, the plates preferably have a constant thickness.

[0028] According to an embodiment of the invention, sides or edges of the plates are provided with a toothed surface and / or an additional material for increasing gripping force to the object to be clamped. According to an embodiment of the invention, the plate is provided in form of a triangular, trapezoidal, angular, half-circular, circular, “V” or “U”-shape for accepting the object to be clamped. Such geometry of the plate allows an easy placement of the object to be clamped e.g., initial placement of the object before being clamped.

[0029] According to an embodiment of the invention, the wedge-like element is formed by a plurality of plates stacked parallel to each other, either horizontally or vertically side by side in contact, wherein the plates are push-able or movable by the stressing means towards the object to be clamped. This allows the clamping force to be exerted optimally.

[0030] According to an embodiment of the invention, the object to be clamped is sandwiched by two or more plates arranged in the same plane, or more than one object to be clamped are sandwiched by two or more plates and further with one or more spacer elements, arranged in the same plane. This allows one or more objects e.g., multiple cables, can be clamped simultaneously by the clamping device.

[0031] According to an embodiment of the invention, a backing elements and / or closing plates are provided to an end of the wedge-like element and / or a rotation axis is provided to the body of the clamping device supporting the wedgelike element, wherein a plurality of plates which made up the wedge-like element are arranged in such a way that when the force is exerted by the stressing means, the plurality of plates are consequently exerted towards the object to be clamped, either by the backing element or through the rotation axis. Depending on the variant of the invention, backing elements and / or closing pates and / or rotation axis can be provided to the wedge-like element.

[0032] According to an embodiment of the invention, the body of the clamping device comprises a plurality of backing elements, wherein the backing elements are provided in form of a blade, arranged to be in contact with the plates such that when the force is exerted by the stressing means, the force is transferred from the backing elements to the corresponding plates. This allows for instance almost each, if not each, of the plates are supported or controlled by its corresponding backing elements such that the plates are push-able to or retractable from the targeted object.

[0033] According to an embodiment of the invention, the body is provided with a backing element with a gradually declining width. As the wedge-like elements can be provided to the body of the clamping device within the space, this geometry allows a wedging effect to be achieved, therefore enhancing the clamping force initiated by the stressing means.

[0034] According to an embodiment of the invention, when the clamping device is clamped, the wedge-like elements are consequently exerted towards the object to be clamped, wherein the cavity of the body corresponds predominantly to the shape of the object to be clamped. For instance, when the wedge-like element is formed by a plurality of plates, larger contact area with the object can be realised when the plates are becoming less thick.

[0035] According to an embodiment of the invention, the plates and the backing element are provided substantially perpendicular to a longitudinal axis of the object to be clamped, such as a tendon, wherein the plates may be supported by a chassis element, or without. The plates may be provided in form of a triangular, trapezoidal, angular, half-circular, circular, “V” or “U”-shape for accepting the object to be clamped.

[0036] According to an embodiment of the invention, the clamping device further comprises a transfer beam, wherein the stressing means is either mounted directly on the transfer beam, or is mounted on the stressing chair which in turn is bearing against the transfer beam in order to exert a force to the clamping device. In some cases, it may be advantageous to divide the clamping device into lighter individual components with smaller weight or dimensions. In particular, one of these elements may be a transfer beam receiving the force of the stressing means and transferring it to the body of the clamping device. This transfer beam may also be assembled on site around the element to be clamped and be composed of plates, stiffeners and bolts. According to an embodiment of the invention, one or more clamping devices are provided to each side of the portion of the object to be detensioned such as the structural element or the tensioning element.

[0037] According to an embodiment of the invention, the body of the clamping device comprises structural support elements such as backing elements and / or closing plates and / or rotation axis to resist the clamping force connected by bolts and / or closing plates and defining an inner cavity to receive at least two wedgelike elements, wherein a second cavity is provided in between the wedge-like elements for receiving an object to be clamped.

[0038] According to a further embodiment of the invention, the wedge-like element may be individual plates stacked horizontally and / or vertically to form the mass of the wedge-like element.

[0039] According to a further embodiment of the invention, the wedge-like elements may also be a plurality of plates assembled to a framing structure and / or chassis.

[0040] According to yet a further embodiment of the invention, (cylindrical) rotation axes and closing plates may be provided to the body of the clamping device, with wedge-like elements able to rotate around the cylindrical rotation axes to provide the necessary clamping force.

[0041] According to an embodiment, the wedge-like element is an integrated element with the body, formed by a plurality of plates, wherein the plates are provided in the same shape and / or size. Alternatively, the plates may be provided in similar shape but may be offered with varying sizes to accommodate the object to be clamped.

[0042] By “about” or “approximately” in relation to a given numerical value, it is meant to include numerical values within 10% of the specified value. All values given in the present disclosure are to be understood to be complemented by the word “about”, unless it is clear to the contrary from the context. The indefinite article “a” or “an” does not exclude a plurality, thus should be treated broadly.

[0043] It should be understood that the various embodiments of the present invention can be combined, forming further embodiments which is well within the capability of the skilled person in the art.

[0044] To this end, it is disclosed that the stressbar and its associated anchorage (e.g. stressnut) can be replaceable with other similar component or element having similar function. For instance, instead of stressbar, one or more strands or ropes and its associated anchorages can be used instead of the stressbars.

[0045] The term “structural element” as used herein refers to a basic component of a building structure which forms a structural frame building structure such as beams, pillars, roof terraces, slabs, columns, girders and / or other structural members and connections.

[0046] The term “tensioning element” as used herein refers to an element which carries tension and no compression. The tensioning element may be provided to such as bridge cable in order to support the main deck where the traffics flow. The tensioning element described herein may be for instance a tendon.

[0047] The term “wedge-like element” refers to an object which resembles a wedge having one thick end and one thin end, which may be tapered to a thin edge, that for instance is driven between two objects or parts of an object to secure or fill in a space / cavity between them. As an example, the wedge-like element (which may be formed by a plurality of plates) is provided to the body of the clamping device. The wedge-like element may taper or be provided to a thin edge between backing elements, or between backing element and an object to be clamped e.g., tendon (such as embodiments shown in the Figures 1 , 3 and 4). In another example, the wedge-like elements may be provided with a shape presenting an increasing width having e.g., half circular shape, wherein said two wedge-like elements are provided to sandwich an object to clamped (such as embodiment shown in the Figures 2). Thanks to the at least two wedge-like elements provided to the body, the resulting wedging effect could enhance the clamping force initiated by the stressing means.

[0048] The terms “at least one” or “one or more” are used interchangeably and means one, two, three, four, five and above, and usually up to about ten.

[0049] Brief description of the figures

[0050] Figure 1A shows a schematic perspective view of a detensioning system comprising two clamping devices according to a first embodiment of the present invention.

[0051] Figure 1 B shows a schematic side view of the detensioning system according to the first embodiment shown in the Figure 1 A.

[0052] Figures 1 C shows a schematic horizontal cross-sectional view of a detensioning system, comprising two clamping devices according to the first embodiment.

[0053] Figures 1 D shows a schematic vertical cross-sectional view perpendicular to the longitudinal axis of the detensioning system according to the dotted line “W” of the Figure 1 B.

[0054] Figure 1 E is a magnified view of the Figure 1 C showing a wedging effect of the clamping device, wherein the wedge-like elements are interposed in between the object to be clamped and the backing elements.

[0055] Figure 1 F shows a schematic perspective view of one of the clamping devices according to the first embodiment shown in the Figure 1 A that is formed by a body, and stressing means, wherein a transfer beam may alternatively be provided in between them. Figure 1 G shows a schematic perspective view of one of the clamping devices according to a variant of the first embodiment shown in the Figure 1A that is formed by a body and a transfer beam.

[0056] Figure 2A shows a schematic perspective view of a detensioning system, comprising two clamping devices according to a second embodiment.

[0057] Figures 2B shows a schematic side view of a detensioning system, according to the second embodiment shown in the Figure 2A.

[0058] Figures 2C shows a schematic horizontal cross-sectional view at the longitudinal axis of the detensioning system according to the second embodiment, wherein the clamping device comprises a body having two wedgelike elements, wherein each wedge-like element comprises plates assembled on an eccentric rotation axis.

[0059] Figure 2D shows a cross-sectional view perpendicular to the longitudinal axis of the detensioning system according to the dotted line “W” of the Figure 2B.

[0060] Figure 2E shows a schematic perspective view of one of the clamping devices according to the second embodiment shown in the Figure 2A that is formed by a body, and stressing means, wherein a transfer beam may alternatively be provided in between them.

[0061] Figure 2F shows a schematic perspective view of one of the clamping devices according to the second embodiment shown in the Figure 2A that comprises alternatively also with a transfer beam.

[0062] Figure 3A shows a schematic perspective view of a wedge-like element of the clamping device according to a third embodiment, comprising a plurality of plates supported by an internal chassis, wherein the plates have a side having a groove shape (or dent) where the object to be clamped can be placed thereto. Figure 3B shows a schematic perspective view of the detensioning system according to a third embodiment, comprising two clamping devices.

[0063] Figure 3C shows a schematic side view of a detensioning system, comprising two clamping devices according to the third embodiment shown in the Figure 3B.

[0064] Figure 3D shows a horizontal cross-sectional view of a detensioning system at the axis of the object to be clamped, comprising two clamping devices according to the third embodiment shown in the Figure 3B.

[0065] Figure 3E shows a schematic cross-sectional view perpendicular to the longitudinal axis of the object to be clamped according to the third embodiment where the dotted line “W” is shown in the Figure 3C.

[0066] Figure 3F shows a schematic perspective view of one of the clamping devices according to the third embodiment shown in the Figure 3B that is formed by a body, and stressing means, wherein a transfer beam may alternatively be provided in between them.

[0067] Figure 3G shows a schematic perspective view of one of the clamping devices according to the third embodiment shown in the Figure 3B that comprises alternatively also with a transfer beam.

[0068] Figure 4A shows a schematic perspective view of a detensioning system for two objects to be clamped, comprising two clamping devices, formed by a body and alternatively also by a transfer beam, according to a fourth embodiment of this invention.

[0069] Figure 4B shows a schematic top view of a detensioning system for two objects to be clamped, comprising two clamping devices according to the fourth embodiment shown in the Figure 4A. Figure 4C shows a cross-sectional view perpendicular to the longitudinal axis of the detensioning system according to the dotted line “Y” of the Figure 4B.

[0070] Detailed description of the invention

[0071] The inventors of the present invention propose a clamping device and a method for a clamping an object. In addition, the present invention is suitable for a detensioning system, and its application includes a method of controlling detensioning of the structural elements or tensioning elements (e.g., tendons) which have previously been pre-tensioned, involving one or more clamping devices of the detensioning system described herein. The clamping devices are mounted for example in between the cutting location, and both the clamping devices are stressed via stressbars against one another to a force close to the remaining force in the object to be detensioned, preferably above for instance to 90 % of the tendon force before cutting the tendon. The detensioned tendon section (in between the clamping devices) can then be cut by for instance a diamond wire cutting machine, and subsequently the tendon can be de-tensioned in a controlled manner by de-tensioning the stressbars with hydraulic cylinders (e.g., jacks) until the entire tendon force of the tendon is released.

[0072] According to an application of the present invention, the detensioning system comprises at least one clamping device arranged on at least one side of the portion of the structural element or the tensioning element to be detensioned, wherein the clamping device having a cavity with an opening for accepting the structural element or the tensioning element to be detensioned.

[0073] In some of the existing clamping devices or detensioning systems, an inner element is placed within the cavity of the clamping device in order to increase friction with the object to be detensioned. The said inner element may be a grout or a filler material that is introduced into the space within the cavity formed by the clamping device and the structural element or the tensioning element to be detensioned. The clamping device or a part of it may act as a formwork for the filler hardening material that will encircle the structural element to be detensioned. However, such devices or methods are not ideal as longer down time is required for the filler material to be placed or achieve the required strength. The present invention is therefore proposed to overcome the aforementioned drawback.

[0074] Figures 1A to 1 G demonstrate a first embodiment of the present invention which may be used in a detensioning system 1000, for instance two clamping devices 100 are provided in between an object 50 to be clamped e.g., tendon, wherein stressbars 300 are temporarily employed to connect the two clamping devices 100. The clamping device 100 comprises a body 20 and a stressing means 40 which may alternatively be connected to a transfer beam 200. The body 20 comprises at least two wedge-like elements 22 and structural support elements, wherein the wedge-like elements 22 are arranged at least partially within the body 20, in such a way that a cavity with an opening exists between the wedge-like elements 22, wherein an object to be clamped 50 is provided to the cavity. According to this embodiment, the wedge-like elements 22 may comprise a plurality of plates 24 that are stacked on planes that are parallel to the longitudinal axis of the object 50 to be clamped on top of each other (that is horizontally, as shown on the drawings, or vertically if the clamping device 100 is rotated 90°). The object 50 may be clamped on each longitudinal side by the wedge-like elements 22. A total of four stressing means 40 are provided to exert a force to the clamping device 100 such that the resulting movement of the wedge-like elements 22 against the surface of the object 50 to be clamped induces a clamping force. Of course, the number of stressing means can be adjusted accordingly, depending on the actual need in each application.

[0075] To this end, it is disclosed that the wedge-like elements 22 may be made up of a plurality of plates 24, wherein each of the plates 24 according to the present invention may be elongated, flat, disc-like, with a thickness of between about 2 mm and 50 mm, preferably between about 5 mm and 30 mm, more preferably between around 8 mm and 20 mm. The plates 24 generally have a constant thickness throughout its entire flat surface. Moreover, the edges or sides of the plates 24 can be provided with a profiled surface, such as a rough surface or a toothed surface in order to further increase the gripping force to the object 50 to be clamped. In this connection, it is foreseen that only the region which is in contact with the object 50 to be clamped is provided with such profiled surface (e.g., toothed surface). It is also foreseen that additional elements, such as ceramics, sand, metal grit or others can be added to further increase the friction between the plates and the object to be clamped. In addition, it is disclosed that the plates 24 may deform and adapt to the object 50 to be detensioned in such a way that the edges of the plates oppose to the sliding movement of the object 50 to be clamped and increase the clamping force. Moreover, the plates 24 can be stacked parallel to each other, placed horizontally in contact from bottom to top, or placed vertically in contact side by side, such that the sides or edges of the plates 24 leave a space to form a cavity, and can be in contact with the object 50 to be clamped. When the clamping device 100 is stressed, the reduced cavity corresponds predominantly to the shape of the object 50 to be clamped.

[0076] According to the present invention, the body 20 of the clamping device 100 may comprise at least one assembly of backing elements 21 formed by a plurality of plates providing one or more inclined planes to the plates 24. In this embodiment, the declining width of the backing elements 21 contribute to the clamping effect of the wedge-like elements 22, wherein the wedge-like elements 22 are provided at least partially to the body 20.

[0077] The plates 24 may be provided in different forms e.g., a triangular or a “V”-, or a “U”-shape. A first cavity (e.g., a space) is provided to the body 20, wherein the first cavity can be provided with the wedge-like element 22. A second cavity (e.g., a space) is created in between the plates 24 or in between the wedgelike element 22 such that the object 50 to be clamped can be inserted in said second cavity. The individual plates 24 can be pushed against the backing element 21 and be activated against the object 50 to be clamped. They can also be activated passively when the clamping device 100 moves as a result of the force applied on the stressbars 300. In other words, two assemblies of plates 24 (which form the two wedge-like elements 22) can be provided at least partially within the body 20 of the clamping device 100 such that the wedge-like elements function in tandem to clamp the object 50.

[0078] Figure 1A illustrates an application where two clamping devices 100 are used in tandem to serve as a detensioning system 1000. Each clamping device 100 is formed by a body 20 and optionally a transfer beam 200. A number of stressbars 300 may for instance be arranged to connect between the transfer beams 200 of the clamping devices 100 arranged on both sides of the object 50 to be detensioned. The stressing means 40 may be provided to the transfer beams 200 of the clamping device 100 to exert a force, which is then transformed to a clamping force. To this end, it is foreseen that one clamping device 100 can also be sufficient to be served as a detensioning system 1000. For example, the clamping device 100 can be arranged to be connected by means of stressbars 300 to an anchored structure. This enables the portion of the object 50 between the clamping device 100 and the said anchored structure to be detensioned.

[0079] Figure 1 B shows a schematic side view of the detensioning system 1000 comprising the stressing means 40 and the body 20 of the clamping device of the first embodiment, wherein two wedge-like elements 22 are arranged at least partially within the body 20 of the clamping device 100. A further variant of this is that a transfer beam 200 can be provided to the clamping device, in particularly between the stressing means 40 and the body 20. The said body 20 comprises a backing element 21 formed by a plurality of plates that may be connected by bolts. The body 20 may also comprise top and bottom closing plates 23 linking the backing elements 21 . A cavity is provided to the body 20 of the clamping device 100 for accepting the wedge-like elements 22. A cavity is provided to the wedge-like elements 22 for accepting an object 50 to be clamped, which in the present case is represented by a tendon. When the stressing means 40 exerts a force to the clamping device 100, the wedge-like elements are moved or pushed consequently towards the surface of the object 50 to be clamped, thereby inducing a clamping force. It is disclosed herein that the wedge-like elements 22 may be formed by a plurality of plates 24, wherein the plates 24 are for instance flat, disc-like having a constant thickness. Furthermore, the plates 24 may have different shape and / or size to accommodate the object 50 to be clamped. As each of the plates 24 are being exerted towards the surface of the object 50 to be clamped, part of these plates 24 may subsequently be protruded outwardly from the body 20 of the clamping device 100 while these plates 24 exert a clamping force towards the object 50 e.g., tendon.

[0080] Figure 1 C is a horizontal cross-sectional view along the longitudinal axis AB of the detensioning system 1000 as shown in the Figure 1 B. The cross section of the body 20 shows that the backing elements 21 may also be provided to the body 20, wherein the plates of the backing element 21 are connected by assembly bolts 27. The backing elements 21 comprise a declining width along the longitudinal axis AB of the object 50 (and body 20) such that the space (e.g., first cavity) is filled by the wedge-like elements 22. In other words, the wedge-like elements are located at least partially within the body 20. Due to the form of the backing elements 21 , the two wedge-like elements 22 (which is formed by a plurality of plates 24 having e.g., triangular shape) are able to exert an increasing force opposing to the movement of the object 50 to be clamped. As it can be seen in the Figure 1 C, two wedge-like elements 22 are provided on each clamping device 100 to sandwich the object 50 to be clamped. In order to increase the gripping force, two plates 24 located on the same horizontal plane of the two- opposing wedge-like elements 22 are provided to sandwich the object 50 to be clamped.

[0081] Figure 1 D is a vertical cross-section view perpendicular to the longitudinal axis of the object to be clamped, along the line “W” as shown in the Figure 1 B. Figure 1 D shows the body 20 of the clamping device 100 comprising at least two wedge-like elements 22, wherein the said wedge-like elements 22 are formed by a plurality of plates 24. A cavity is provided in between the two wedge-like elements 22 that corresponds predominantly to the outline of the object 50 that will be clamped when the stressing means exerts a force on the transfer beams 200 and, as a consequence to the body 20 of the clamping device 100. It can also be seen in the Figure 1 D that the body 20 may comprise closing plates 23 which are provided to the top and bottom, linking the backing elements 21 in order to resist the clamping force. Moreover, the backing element 21 may be formed by a stack of plates connected by assembly bolts 27. Each of the plates of the backing element 21 corresponds to a wedge-like element 22. This allows that most of the wedge-like element 22, if not all, are movable by the stressing means in at least one degree of freedom relative to each other such that the resulting movement of the wedge-like element 22 against the surface of the object 50 to be clamped induces a clamping force.

[0082] Figure 1 E is a magnified view of the Figure 1 C showing a wedging effect which is provided by the first embodiment. In this embodiment, the two wedge-like elements 22 are formed by plates 24 that are being stacked on top of each other, wherein the plates 24 are provided generally in form of an acute triangle shape (e.g., seesaw), whereby the plates 24 have an increasing width (E1 and E2, wherein E1 < E2). To this end, it can be seen that the backing elements 21 comprise a similar geometry of having an increasing width (D2 and D1 , wherein D2 < D1 ). The wedge-like elements 22 are interposed in between the object 50 to be clamped and the backing elements 21 , and the wedge-like elements 22 are provided at least partially within the body 20 of the clamping device 100. When the stressing means 40 exerts a clamping force, a few, or a majority, if not all, of the plates 24 are moved or pushed towards the surface of the object 50 to be clamped such that they are in contact with the surface of the object 50 accordingly. A better gripping force (or clamping force) can thus be reached thanks to the wedging effect provided by the configuration of this first embodiment.

[0083] Figure 1 F shows a view of one of the clamping devices depicted in Figure 1A, comprising a body 20, and the stressing means 40. A transfer beam 200 may in a preferred example be provided to the clamping device 100.

[0084] Figure 1 G shows a view of one of the clamping devices depicted in Figure 1A, comprising a body 20 and a transfer beam 200.

[0085] Figures 2A to 2D illustrate a second embodiment of the clamping device 100. The clamping device 100 comprises a body 20 having two wedge- like elements 22 provided at least partially to the body 20, wherein the wedgelike elements 22 are formed for instance by a plurality of plates 24, wherein the plates 24 are horizontally stacked up on top of each other, wherein the body 20 of the clamping device 100 comprises a cavity for accepting an object 50 to be clamped.

[0086] Figure 2A is a schematic perspective view of a detensioning system 1000, comprising two clamping devices 100 joined by four stressbars 300 and an object 50 i.e. , a tendon to be detensioned. The clamping device 100 comprises a body 20 and a stressing means 40, wherein the clamping force is exerted by the wedge-like elements 22 that are activated by the stressing means 40. Similar to the previous example, the plates 24 are stacked on top of each other within the body 20, as it can be seen in the Figure 2B. The body 20 of the clamping device 100 comprises two rotation axis 28 linked by closing plates 23. The two wedgelike elements 22 are brought together and installed on the rotation axis 28.

[0087] Figure 2C shows a horizontal cross section of the detensioning system 1000, wherein the tendon is clamped in between two wedge-like elements 22 from a clamping device 100. In this embodiment, the object 50 i.e., tendon is sandwiched by two clamping devices 100. The wedge-like element 22 comprises a curved side that can have a profiled (toothed) surface where said side is capable of clamping the object 50 when being stressed by the stressing means 40. The wedge-like elements 22 is formed by a plurality of plates 24 that are pivotally connected to an eccentric rotation axis 28 such that each of the plates 24 of the assembly is capable of rotating. Due to the eccentricity of the plates 24 relative to the rotation axis 28, the clamping force exerted by each plate 24 increases as the plate rotates. Due to the wedge-like geometry, the rotation axis 28 receives the clamping force from the plates 24 and performs the same function as the backing element 21 of the previous embodiment (Figures 1 A-1 D). The two rotation axes 28 may be linked by closing plates 23 to resist the clamping force. When the stressing means 40 exerts a force, a few, or a majority, if not all, of the plates 24 are moved or pushed rotationally towards the object 50 to be clamped such that they are in contact with the surface of the object 50 accordingly. It is reiterated that the plates can be semi-circular or other curved shape which is capable of rendering wedging effect to the object 50 to be clamped. To this end, it is mentioned that the wedging effect is provided also in this embodiment due to the fact that the distance between the eccentric rotation axis 28 and the sides or edges of the wedge-like elements 22 i.e. , the plates 24 increases, when the plates 24 rotate as the result of the force exerted by the stressing means 40.

[0088] To this end, it is emphasized that the plurality of plates 24 and / or backing plates 21 according to each embodiment of the invention may be provided in the same shape and / or size or present different shapes to accommodate the object 50 to be clamped.

[0089] Figure 2D shows a vertical cross section of the detensioning system 1000 perpendicular to the longitudinal axis AB of the tendon from the dotted line “W” depicted in the Figure 2C. The two wedge-like elements 22 which are formed by two assembly of plates 24 rotate around two rotation axes 28 and thereby clamp the object 50. Closing plates 23 may be provided to link the two rotation axes 28 in order to resist the clamping force.

[0090] Figure 2E shows a view of one of the clamping devices depicted in Figure 2A, comprising a body 20, a transfer beam 200, and the stressing means 40.

[0091] Figure 2F shows a view of one of the clamping devices depicted in Figure 2A, comprising a body 20 and a transfer beam 200.

[0092] Figures 3A to 3D relate to a third embodiment of the de-tensioning system 1000.

[0093] Figure 3A shows a wedge-like element 22 which may be formed by an assembly of plates 24 that are installed within an internal chassis 25 and are placed vertically side by side in contact parallel to each other on planes forming an angle (perpendicular or with an orthogonal component) with the axis of the object 50 to be clamped. The plates 24 comprise a groove, such as a “U”-shape for receiving the object 50 to be clamped. The body 20 of the clamping device 100 may comprise two internal chassis 25 for receiving two wedge-like elements 22, which are formed by vertically positioned plates 24. These wedge-like elements 22 are provided to the cavity of the body 20 such that the wedge-like elements 22 are left with a cavity for receiving the object 50 to be clamped i.e., tendon.

[0094] Figure 3B shows a detensioning system 1000, comprising two clamping devices 100 joined by a number of stressbars 300, wherein each of the clamping devices 100 comprises two wedge-like elements 22 according to the third embodiment of the invention. To this end, it can be foreseen that the tendon 50 is sandwiched in between the two assemblies 30 of plates.

[0095] Figure 3C is a side view of the detensioning system 1000 according to the third embodiment, which can be better visualised in the Figure 3D.

[0096] Figure 3D shows a horizontal cross-sectional view of a detensioning system at the axis of the object 50 to be clamped, comprising two clamping devices according to the third embodiment shown in the Figure 3B, wherein a lower half and an upper half of the body 20 are sandwiching the object 50 i.e., tendon. The body 20 of the clamping device 100 according to this embodiment comprises backing elements 21 that are formed by a plurality of plates that define the inclined plane on which the chassis 25 and the assembly of plates 24 slide, creating the necessary clamping force. Besides the backing element 21 , the body 20 of the clamping device 100 may further comprise assembly bolts 27, distancing elements 29 for assembling the backing elements 21 , as well as top and bottom closing plates 23 to link the backing elements 21 in order to resist the clamping force transmitted by the at least two wedge-like elements 22.

[0097] Figure 3E shows a schematic cross-sectional view perpendicular to the longitudinal axis of the object to be clamped according to the third embodiment, wherein the clamping device comprises a body receiving two wedge-like elements 22, wherein the wedge-like elements are formed by a plurality of plates 24 provided vertically parallel to each other and assembled on a chassis 25. Figure 3F shows a view of one of the clamping devices depicted in Figure 3B, comprising a body 20, a transfer beam 200, and the stressing means 40.

[0098] Figure 3G shows a view of one of the clamping devices depicted in Figure 3B, comprising a body 20 and a transfer beam 200.

[0099] To this end, it is disclosed that the third embodiment also provides a wedging effect similar to the first embodiment, as explained the Figure 1 E. In this connection, as can be seen in the Figure 3D, the plates 24 as well as the backing elements 21 provided with an increasing diameter / width such that the wedge-like elements 22 are tapered in between the backing elements 21 and the object 50 to be clamped, thereby rendering the wedging effect from the clamping.

[0100] When a force is exerted by the stressing means 40 the clamping devices 100 move and the backing element 21 activates the wedge-like elements 22 comprising plates 24 towards the surface of the object 50 to be clamped.

[0101] The advantage of providing such wedge-like volumetric shape of the body is obvious. Similar to the first embodiment, the reducing distance between the two opposed backing elements 21 enables the wedge-like elements 22 to exert an increasing gripping force to the object 50 to be clamped i.e. , tendon.

[0102] Figures 4A to 4C relate to a fourth embodiment of the de-tensioning system 1000.

[0103] Figure 4A illustrates an application where the clamping devices 100 are used in tandem to serve as a detensioning system 100 for two objects 50 to be clamped. The clamping devices 100 are formed by a body 20 and a transfer beam 200 connected to stressing means 40. Similar to the invention presented in figures 3A to 3D, the body 20 of the clamping device comprises backing elements 21 linked by closing plates 23. The body 20 comprises a space for receiving two wedge-like elements 22, positioned between the said backing elements 21 and one of the objects 50 to be clamped, and one spacer element 26, positioned between the two objects 50 to be clamped. When a force is exerted by the stressing means 40, the clamping devices 100 move and the backing elements 21 activate the wedge-like elements 22 against the objects 50 to be clamped. The objects 50 to be clamped are not free to move laterally but are instead clamped by a spacer element 26.

[0104] To this end, it is disclosed that the same principle may be used to detension more than two objects 50 to be clamped. In particular, it may be used to de-tension more than two parallel tendons, providing spacer elements 26 between each two adjacent tendons. It is also disclosed that the spacer element 26 may have toothed surfaces in the areas that are in contact with the objects 50 to be clamped. It is also disclosed that the spacer element 26 may have constant or declining width to increase the clamping effect.

[0105] Figures 4A to 4C present a configuration of wedge-like elements 22 analogue to the one presented in embodiment 3 of this invention, with an assembly of plates 24 installed on a chassis 25, as depicted in figure 3A. Similarly, the spacer elements 26 may also be formed by two assemblies of plates 24 installed on both sides of a chassis 25.

[0106] Figure 4B shows a horizontal top view of the de-tensioning system comprising two clamping devices 100, wherein a set of two wedge-like elements 22 plus one spacer element 26 are provided in the body 20 of the clamping device 10 to clamp two objects 50 to be clamped.

[0107] Figure 4C is a vertical cross-section of the detensioning system perpendicular to its longitudinal axis across the dotted line “Y” depicted in the Figure 4B. It shows the two components of the wedge-like body, formed by the backing elements 21 and the closing plates 23. It also shows the elements that are arranged in the same plane, that includes the axis of the objects 50 to be clamped and the median planes of the two wedge-like elements 22 and the spacer element 26.

[0108] It is also disclosed that the wedge-like elements 22 used in embodiment 4 of this invention may also be formed by a stacking of parallel plates as depicted on figures 1 D and 2D. In addition, the spacer elements 26 may be formed by a solid metal piece or by a stacking of parallel plates 24.

[0109] To this end, it is disclosed that present invention is especially suitable to be used on a detensioning system, for example used on a civil structure i.e. , bridge where the bridge structure comprises one or more tendons 50 to be replaced that are being installed within a box girder anchored at one or both ends. In order to replace or to repair the tendon, workers may enter into box through a manhole to install the detensioning system 1000 according to the present invention.

[0110] The structural elements or the tensioning elements to be repaired or replaced e.g., tendon, in the present context are usually pre-tensioned at a very high tension. Before cutting the aged or damaged tendon, a relevant portion of the tendon has to be de-tensioned in a controlled manner and its force has to be transferred to auxiliary elements such as the stressbars and the associated stressnuts. Once a portion of the tendon has a very low or no force, it can be safely cut. The auxiliary elements can then be de-tensioned safely and the full tendon, free of tension, can be dismantled. In doing so, at least one clamping device is arranged on one side of the structural element or the tensioning element to be detensioned.

[0111] The present invention successfully eliminates the needs of providing an inner element, either in form of a preform having a pre-determined shape, or by injecting filler material into the cavity of the clamping device, which the inner element is sandwiched in between a tendon and the clamping device. This allows for a quicker and easier process of detensioning tendon and its replacement.

[0112] A number of stressing means such as hydraulic cylinders (or bar jacks) may be used in the present invention that is not limited to certain jacks. For instance, double-acting hollow core bar jacks (also called centre hole bar jacks) can be mounted on top of a stressing chair, which in turn is bearing against the back of the clamping devices. The bar jacks are used to stress as well as to detension the stressbars after cutting of the tendon. Ideally, the bar jacks should be calibrated before use. Alternatively, other tensile elements such as strands or wires and its associated anchoring elements and jacks may be used in lieu of the stressbars.

[0113] The method of detensioning a pre-stressed tendon is generally known, such as similar to those disclosed in the international patent application PCT / EP2021 / 076418, except that no inner element is required in the present invention.

[0114] Reference numbers

[0115] 20 body (of the clamping device)

[0116] 21 backing element

[0117] 22 wedge-like element 23 closing plates

[0118] 24 plates

[0119] 25 chassis

[0120] 26 spacer element

[0121] 27 assembly bolts

[0122] 28 rotation axis

[0123] 29 distancing elements

[0124] 30 assembly (of plates)

[0125] 40 stressing means

[0126] 50 object to be clamped

[0127] 100 clamping device

[0128] 200 transfer beam

[0129] 300 stressbars

[0130] 1000 de-tensioning system

Claims

Claims1. A clamping device (100) for clamping an object, wherein the clamping device (100) comprises a body (20) and a stressing means (40); wherein the body (20) of the clamping device (100) comprises at least two wedge-like elements (22), and structural support elements such as backing elements (21 ), closing plates (23) and / or rotation axis (28) for supporting the at least two wedge-like elements (22), wherein the wedge-like elements (22) are housed at least partially within the body (20), arranged next to each other for forming a cavity with an opening for receiving an object (50) to be clamped, wherein the wedge-like elements (22) are movable by the stressing means (40) in at least one degree of freedom relative to each other; wherein the stressing means (40) is either mounted directly on the clamping device (100), or on a stressing chair which in turn is bearing against the body (20) in order to exert a force to the clamping device (100) such that the resulting movement of the wedge-like elements (22) against the surface of the object (50) to be clamped induces a clamping force.

2. The clamping device (100) according to claim 1 , wherein the clamping device (100) is formed by at least two half clamps, wherein the two half clamps are joined together by mechanical fixing means around the object (50) to be clamped.

3. The clamping device (100) according to claim 1 or claim 2, wherein the wedge-like element (22) is formed by a plurality of plates (24).

4. The clamping device (100) according to any one of the preceding claims, wherein the wedge-like element (22) is an integrated element with the body (20), formed by a plurality of plates (24), wherein the plates (24) are provided in the same shape and / or size.

5. The clamping device (100) according to any one of the preceding claims, wherein the body (20) is substantially elongated such that the wedge-like element (22) is at least partially accommodated thereto, the thickness of the plate (24) is substantially less than its length, having a thickness of between about 2 mm and 50 mm, more preferably between about 5 mm and 30 mm, or more preferably between about 8 mm and 20 mm.

6. The clamping device (100) according to any one of the preceding claims, wherein sides or edges of the plates (24) are provided with a toothed surface and / or an additional material for increasing gripping force to the object (50) to be clamped.

7. The clamping device (100) according to any one of the preceding claims, wherein the plate (24) is provided in form of a triangular, trapezoidal, angular, half-circular, circular, “V” or “U”-shape for accepting the object (50) to be clamped.

8. The clamping device (100) according to any one of the preceding claims, wherein the wedge-like element (22) is formed by a plurality of plates (24) stacked parallel to each other, either horizontally or vertically side by side in contact, wherein the plates (24) are push-able or movable by the stressing means (40) towards the object (50) to be clamped.

9. The clamping device (100) according to any one of the preceding claims, wherein the object (50) to be clamped is sandwiched by two or more plates (24) arranged in the same plane, or more than one object (50) to be clamped are sandwiched by two or more plates (24) and further with one or more spacer elements (26), arranged in the same plane.

10. The clamping device (100) according to any one of the preceding claims, wherein a backing element (21 ) is provided to an end of the wedge-like element (22), or a rotation axis (28) is provided to the body (20) of the clamping device (100) supporting the wedge-like element (22), wherein a plurality of plates (24) which made up the wedge-like element (22) are arranged in such a way that when the force is exerted by the stressing means (40), the plurality of plates (24)are consequently exerted towards the object (50) to be clamped, either by the backing element (21 ) or through the rotation axis (28).11 . The clamping device (100) according to any one of the preceding claims, wherein the body (20) of the clamping device (100) comprises a plurality of backing elements (21 ), wherein the backing elements (21 ) are provided in form of a blade, arranged to be in contact with the plates (24) such that when the force is exerted by the stressing means, the force is transferred from the backing elements (21 ) to the corresponding plates (24).

12. The clamping device (100) according to any one of the preceding claims, wherein the body (20) is provided with a backing element (21 ) with a gradually declining width.

13. The clamping device (100) according to any one of the preceding claims, wherein when the clamping device (100) is clamped, the wedge-like elements (22) are consequently exerted towards the object (50) to be clamped, wherein the cavity of the body (20) corresponds predominantly to the shape of the object (50) to be clamped.

14. The clamping device (100) according to any one of the preceding claims, wherein the plates (24) and the backing element (21 ) are provided substantially perpendicular to a longitudinal axis of the object (50) to be clamped, such as a tendon.

15. The clamping device (100) according to any one of the preceding claims, further comprises a transfer beam (200), wherein the stressing means (40) is either mounted directly on the transfer beam (200), or is mounted on the stressing chair which in turn is bearing against the transfer beam (200) in order to exert a force to the clamping device (100).

16. A detensioning system (1000) for detensioning a portion of an object (50) to be detensioned, such as a structural element or a tensioning element to be detensioned, comprising- At least one clamping device (100) according to any one of the preceding claims, arranged on at least one side of the portion of the object (50) to be detensioned;- Two or more stressbars (300) arranged to connect between an anchored structure and the clamping device (100) which is arranged on one side of the portion of the object (50) to be detensioned, or arranged to connect between the clamping devices (100) arranged on both sides of the object (50) to be detensioned;- Two or more stressbar hydraulic cylinders, wherein each of the stressbar hydraulic cylinder is either mounted directly on the clamping device (100), or on a stressing chair which in turn is bearing against the clamping device (100) located on at least one side of the object (50) to be detensioned.

17. The detensioning system (1000) according to claim 16, wherein one or more clamping devices (100) are provided to each side of the portion of the object (50) to be detensioned such as the structural element or the tensioning element.

18. Use of the detensioning system (1000) according to any one of the preceding claims 16 or 17 for detensioning a portion of an object (50) to be detensioned, such as a structural element or a tensioning element to be detensioned, without providing a filler material or a pre-cast moulded element to the cavity of the clamping device (100) for filling up the cavity before exerting the clamping force.

19. A method for clamping an object, comprising the steps of a) Providing an object (50) to be clamped to a cavity of the clamping device (100) according to any one of the preceding claims 1 to 15; b) Exerting a force to the clamping device (100) to clamp the object(50).

20. A detensioning method for detensioning a portion of an object (50) to be detensioned, such as a structural element or a tensioning element to be detensioned, comprising the following steps: a) Removing of sheath and / or grout covering the portion of the structural element or the tensioning element in case such sheath and / or grout is present, thereby exposing a core element of the structural element of the tensioning element; b) Placing at least one clamping device (100) according to any one of the preceding claims 1 to 15 on the exposed core element, wherein the at least one clamping device (100) is positioned on at least one side of the portion of the object (50) to be detensioned if another side of the portion is anchored to an anchored element, or placing the clamping devices (100) in between the portion of the object (50) to be detensioned; c) Joining the one or more clamping devices (100) arranged on at least one side of the portion of the object (50) to be detensioned with at least two stressbars (300); d) Exerting a longitudinal force to the clamping device (100) until the stressing means (40) reaches approximately the same load carried by the object (50); e) Cutting the core element of the object (50) to be detensioned; f) Releasing the force of the stressbars (300).

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