TENSIONING DEVICE

Abstract: A tensioning device (1) adapted for applying tension to a tendon (2), comprising a first coupling (10) adapted for attachment to the tendon (2) adjacent an end (7) thereof, a second coupling (11) adapted for attachment to an anchorage (3) separate from said end (7), tie means (15, 16) extending between and connected to the couplings (10, 11), and load applying means (19, 20) operable to act between the tie means (15, 16) and at least one of the couplings (10, 11) to cause relative movement of the tie means (15, 16) and coupling longitudinally of the tendon (2) such as to urge the one coupling (10) towards the other coupling (11) and thereby urge said end of the tendon (2) towards the anchorage (3) whereby the tendon (2) is tensioned. A method of tensioning a tendon, comprising the steps of applying to the tendon a tensioning device, the first coupling of the tensioning device being attached to the tendon adjacent one end, an opposite end of the tendon being anchored, the second coupling being attached to an anchorage separate from said one end, and operating the load applying means of the tensioning device to cause the one coupling to be urged towards the other so as to tension the tendon.

Description: TENSIONING DEVICE This invention relates to tensioning devices, particularly, but not exclusively, for applying tension to tendons or rods used in, for example, building structures. The term "tendon" is used hereinafter, unless otherwise stated, to include, generally, tendons, bars, rods, tubes, wires, strands, cables, steel rope and other comparable elongate components. Tendons are used in a variety of situations, including architectural and engineering tensioned structures. In these, it is usually necessary to tension the tendons when installed in the structure. Each tendon is usually fixed at one end thereof and connected at its other end via a turnbuckle to another tendon or anchorage. Conventionally, in structures in which tendons are connected by turnbuckles the tendons are brought together, i.e. tensioned by rotating the turnbuckle. It can, however, be difficult to apply sufficient load to the turnbuckle to tension the tendons. A tendon may also be tensioned by means of a heat blanket applied to the tendon such that it expands. During expansion the associated turnbuckle is constantly turned to accommodate lengthening of the tendon. The tendon is then allowed to cool, and, as it does so, it contracts. Since one end of the tendon is fixed and the other is held in position by the turnbuckle, contraction of the tendon causes it to become tensioned. It is normal to heat tendons in such structures for several hours, typically at least three hours, before cooling which is very time consuming ._.-.In addition, it is difficult to control the amount of tensioning applied to the tendon, and if too much or insufficient heat is applied, and the required tension therefore not achieved, the whole process has to be repeated. It can be difficult to position the heat blankets properly on the tendons on site, and issues of the safety of using such devices can arise. There is a need to provide a means of tensioning tendons which is easier to use and may provide more accurate control of the tensioning. According to a first aspect of the present invention there is provided a tensioning device adapted for applying tension to a tendon, comprising a first coupling adapted for attachment to the tendon adjacent an end thereof, a second coupling adapted for attachment to an anchorage separate from said end, tie means extending between and connected to the couplings, and load applying means operable to act between the tie means and at least one of the couplings to cause relative movement of the tie means and coupling longitudinally of the tendon such as to urge the one coupling towards the other and thereby urge said end of the tendon towards the anchorage whereby the tendon is tensioned. The tensioning device may be designed to be left in situ with the tendon when the tendon has been tensioned. Alternatively the tensioning device may be releasably attachable to the tendon and anchorage, and be used in conjunction with tension retaining means which is provided intermediate the said one end of the tendon and the anchorage to hold the tendon under the tension applied by the tensioning device when the device is subsequently removed. The tension retaining means may, for example, be a turnbuckle or shackle, but it may take other suitable forms. Such a tensioning system works on the principle of allowing an axial load or tension to be applied to a tendon causing it to elongate, whereby the turnbuckle is used to take up the elongation thus locking load in the tendon on removal of the tensioning device. The first coupling may be of a generally C-shape so that it can be readily applied laterally to the tendon. The second coupling may be similarly shaped. The coupling may be adapted to bear on abutments on the tendon and anchorage when the load applying means is operated to urge the one coupling towards the other. The abutment on the tendon may comprise a nut or collar or collet fitted on the end of the tendon, e.g. by screw-threaded engagement, or may comprise a shoulder provided on the tendon. If the end of the tendon to which the first coupling is attached is connected to a turnbuckle, the nut or collar may be engaged with the screw-threading of the end provided for engagement with the turnbuckle. The anchorage to which the second coupling is attached may be a fixture. It may be another tendon or component which can thus be tensioned simultaneously with the tendon or the first mentioned tendon. For example, tendons forming two parts of a brace connected by a turnbuckle may be tensioned by means of the tensioning device. The tie means may comprise one or more rods extending between and connected to the couplings. Alternatively, the tie means may comprise wire rope, cable or chain. Preferably the load applying means is fluid operated, for example by oil or air. It may be arranged, for example, that the tie means includes a piston or plunger operating in a load cell or cylinder provided in one of the couplings, the piston or plunger being fluid operatedAo move in the load cell or cylinder to cause the required relative movement of the tie means and coupling for tensioning the tendon. The fluid operation may be manually or automatically controlled. Other forms of load applying means may be provided. A screw jack arrangement, for example, may operate between the tie means and at least one of the couplings. Means may be provided for measurement of the tension to which the tendon is subjected as such tensioning takes place. This may be incorporated with the or each coupling. Means may also be provided for checking the tension in the or each coupling after tensioning has taken place. Components of the tensioning device may be coated for protection against corrosion. The tensioning device may be used to apply various tensions to a tendon, according to the tension required for the tendon when it is used in a structure. Tensioning devices of various sizes may be provided for applying tension to tendons of different diameters. Alternatively, the tension device may be arranged or adapted to apply tension to tendons having a range of diameters. According to a second aspect of the present invention there is provided a method of tensioning a tendon, comprising the steps of applying to the tendon a tensioning device in accordance with the foregoing first aspect of the invention, the first coupling of the tensioning device being attached to the tendon adjacent one end, an opposite encLof the tendon being anchored, the second coupling being attached to an anchorage separate from said one end, and operating the load applying means of the tensioning device to cause the one coupling to be urged towards the other so as to tension the tendon. The second coupling may be attached to an anchorage which is tensioned simultaneously with the tendon. The second coupling may be attached to a second tendon which is tensioned simultaneously with the first tendon. When the method of tensioning is applied to a tendon having a turnbuckle, shackle or other tension retaining means attached at the one end, the tension retaining means may be arranged to be continuously adjusted as the tendon is tensioned by the tensioning device. This may be done manually or automatically. In this way the tension retaining means is already set to hold the tendon under the tension applied by the tensioning device immediately operation of the device ceases. According to a third aspect of the present invention there is provided a method of measuring the tension of an already tensioned tendon, the tension in the tendon being retained by a tension retaining means, comprising the steps of applying to the tendon a tensioning device in accordance with the foregoing first aspect of the invention, the first coupling of the tensioning device being attached to the tendon adjacent one end, an opposite end of the tendon being anchored, the second coupling being attached to an anchorage separate from said one end, and operating the load applying means of the tensioning device to cause the one coupling to be urged towards the other until the tension in the tendon is no longer retained by the tension retaining means. The load applied to the tensioning device at the point at which the tension retaining means no longer retains the tension in the tendon, will be indicative of the load or tension of the tendon. The load applying means may be fluid operated, for example by oil or air. Pressure may be applied to the load applying means to operate it. When such a load applying means is used the pressure at which the tension retaining means no longer retains the tension in the tendon is noted, and a look-up chart may be used to determine the tension of the tendon. The anchorage to which the second coupling is attached may be another tendon, and the two tendons may be connected by the tension retaining means, such as a turnbuckle. In such an arrangement, the load applying means may be operated until the turnbuckle no longer retains the tension in the tendons, i.e. works free, and the tension of the tendons determined from the load applied to the load applying means. Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a first embodiment of a tensioning device in accordance with the first aspect of the present invention shown coupled with two tendons; Figure 2 is an end view of the tensioning device of Figure 1 shown detached from one of the tendons; and Figure 3 is a cross-sectional view of another embodiment of the tensioning device in accordance with the first aspect of the present invention, shown coupled with two tendons. Figure 1 shows a first embodiment of a tensioning device 1 coupled with a first tendon 2 and a second tendon 3 for engineering structural use. The inner end 7, 8 of each tendon is externally screw-threaded, and a turnbuckle 4 is threadedly engaged with the inner ends 7, 8 to connect the tendons together. A first collar 5 is also threadedly engaged on the inner end 7 of the first tendon 2. Similarly, a second collar 6 is threadedly engaged on the inner end 8 of the second tendon 3. The collars 5,6 are locked securely on the tendons. Outer ends of the two tendons anchored. The tensioning device 1 comprises first and second reaction bodies 10 and 11 respectively which constitute couplings of the device. The reaction bodies 10, 11 are generally frusto-conical in shape but with a C-shaped cross-section (Figure 2), a radial portion being removed to provide a lateral entry 12 into the centre of the bodies to allow them to be coupled with the tendons adjacent the collars 5, 6. At the apex of each frusto-conical reaction body 10, 11 , a portion of the body is removed to form a substantially cylindrical recess 13, 14 with a shoulder 28,29. The reaction bodies are connected together by tie rods 15, 16, which pass through plain holes 15 J 16' in the reaction bodies and are retained thereto by reaction nuts 17,18 threadedly engaged on the tie rods 15,16 respectively. Other types of locking device may be used in place_ of reaction nuts 17, 18. The first reaction body 10 contains load cells 19,20 housing pistons 21,22, which are oil loaded by a common hydraulic oil supply at inlets 23. Seals 24,25 are provided in each of the cells, and there are four cells in total. The second reaction body 11 is not provided with load cells. For use, the collars 5,6 are fully tightened and locked on the threading of the inner ends 7, 8 of the tendons 2,3 and the inner ends are then connected together by the turnbuckle 4. Next the tensioning device 1 is coupled with the tendons 2,3 by locating the reaction bodies 10, 11 on the tendons, each tendon being received through the entry 12 of its respective reaction body, such that the tendon is centred within the reaction body. Each reaction body is then moved along its respective tendon until the collar on the tendon is located within the recess 13, 14 of the reaction body. The reaction nuts 17, 18 are tightened on the tie rods 15, 16 to pull the reaction bodies 10, 11 towards one another, ensuring that the shoulder 28, 29 of each recess 13, 14 abuts its respective collar, and that the pistons 21 , 22 of the load cells 19,20 in the first reaction body 10 abut the reaction nuts 17. To tension the tendons 2,3, oil is pumped from the hydraulic supply by way of the inlet 23 into the load cells of the first reaction body 10. Supplying the oil to the cells attempts to push the pistons out of the cells against the reaction nuts 17. However, these reaction nuts are threadedly engaged with the tie rods 15, 16, and any attempt to force the reaction nuts away from the first reaction body 10 is resisted by the reaction nuts 18 which abut the second reaction body 11 which, in turn, abuts the collar 6 locked in engagement with the second tendon 3. Pumping hydraulic oil into the load cells of the first reaction body 10 therefore forces this body to move towards the turnbuckle 4 which, in turn, forces the tendon 2 towards the turnbuckle thereby tensioning it. At the same time, the second reaction body 11 is similarly being forced towards the turnbuckle, and hence tendon 3 is tensioned. The turnbuckle 4 is turned continuously to accommodate the lengthening of each tendon. When the required tension has been applied to each tendon, the pressure in the hydraulic oil is released allowing the reaction bodies to move away from the turnbuckle, and the tensioning device to be de-coupled from the tendons. The turnbuckle maintains the tension in the tendons. Fitting of the tensioning device to the tendons and the tensioning of the tendons by the device can be carried out quickly and relatively easily so that there can be a substantial saving in the time involved in tensioning the tendons in an engineering application. Figure 3 shows another embodiment of a tensioning device 30, coupled to tendons 31 ,32. The tensioning device comprises a first reaction body 33, coupled to the tendon 31 , and a second reaction body 34, coupled to the tendon 32. The reaction bodies 33,34 again constitute couplings of the device and are joined screw threadedly together, as shown. Each reaction body includes a load cell 35 housing a piston 36 and a seal 37. Each piston 36 is threadedly engaged with a respective one of the tendons 31 ,32 and a locking nut 38. Hydraulic fluid is supplied to the load cells from hydraulic supplies at inlets 39. In use, the tensioning device 30 is coupled to the tendons 31,32, such that the pistons 36 are engaged with the tendons, as shown. Hydraulic fluid such as oil is pumped into the load cells 35 of the reaction bodies 33,34 , forcing the pistons 36 towards each other. This forces the tendons 31 ,32 towards each other, thereby tensioning them. When the required tension has been applied to the tendons, the locking nuts 38 are tightened on the pistons 36 against internal bearing shoulders 40 in the reaction bodies, holding them in their final positions. Access openings 41 are provided in the walls of the reaction bodies for tightening the locking nuts by tommy bars. The hydraulic pressure in the load cells is then released, the tensioning device being left in place on the tendons. The locking nuts and the pistons maintain the tension in the tendons. The first embodiment of the tensioning device, as shown in Figures 1 and 2, may also be used to measure the tension of a tendon or tendons. For measuring the tension of two tendons connected together by a turnbuckle, the tensioning device is applied to the tendons as shown in Figure 1 , and oil pumped into the load cells of the first reaction body 10 until the turnbuckle 4 works free and no longer retains the tension in the tendons. Pumping of oil is stopped at that point and the pressure applied to the load cells noted. The pressure of the load cells is directly proportional to the tension of the tendons, and the tension of the tendons can thus be determined.

Claims: CLAIMS 1. A tensioning device adapted for applying tension to a tendon (2) , comprising a first coupling (10) adapted for attachment to the tendon (2) adjacent an end (7) thereof, a second coupling (11) adapted for attachment to an anchorage (3) separate from said end (7) , tie means (15,16) extending between and connected to the couplings (10, 11) , and load applying means (19,20) operable to act between the tie means (15, 16) and at least one of the couplings (10, 11) to cause relative movement of the tie means (15,16) and coupling longitudinally of the tendon (2) such as to urge the one coupling (10) towards the other (11) and thereby urge said end of the tendon (2) towards the anchorage (3) whereby the tendon (2) is tensioned. 2. A tensioning device according to claim 1 , adapted to be left in situ with the tendon (2) when the tendon has been tensioned. 3. A tensioning device according to claim 1 , adapted to be releasably attachable to the tendon (2) and anchorage (3). 4. A tensioning device according to claim 3, adapted to be used in conjunction with tension retaining means (4) which is provided intermediate the said one end of the tendon (2) and the anchorage (3) to hold the tendon (2) under the tension applied by the tensioning device when the device is subsequently removed. 5. A tensioning device according to claim 4, characterised in that the tension retaining means is a turnbuckle (4) or shackle. 6. A tensioning device according to any preceding claim, characterised in that first and/or second coupling (10, 11) is of a generally C-shape. 7. A tensioning device according to any preceding claim, characterised in that the coupling (10) is adapted to bear on abutments on the tendon (2) and anchorage (3) when the load applying means is operated to urge the one coupling towards the other. 8. A tensioning device according to claim 7, characterised in that the abutment comprises a nut or collar (5,6) fitted on the end of the tendon. 9. A tensioning device according to claim 7, characterised in that the abutment comprises a shoulder provided on the end of the tendon (2) . 10. A tensioning device according to any preceding claim, characterised in that the second coupling (11) is adapted to be attached to an anchorage which is a component tensioned simultaneously with the tendon. 11. A tensioning device according to claim 10, characterised in that the component is a second tendon (3) . 12. A tensioning device according to any preceding claim, characterised in that the tie means comprises one or more rods (15,16) extending between and connected to the couplings. 13. A tensioning device according to any preceding claim, characterised in that the load applying means (19,20) is fluid operated, for example by oil or air. 14. A tensioning device according to claim 12, characterised in that the tie means includes a piston or plunger operating in a load cell (19,20) or cylinder provided in one of the couplings, the piston or plunger being fluid operated to move in the load cell or cylinder to cause the required relative movement of the tie means and coupling for tensioning the tendon. 15. A tensioning device according to any of claims 1 to 12, characterised in that the load applying means is a screw jack arrangement operable between the tie means and at least one of the couplings. 16. A tensioning device according to any preceding claim, characterised in that means are provided for measurement of the tension to which the tendon is subjected as such tensioning takes place. 17. A tensioning device according to claim 16, characterised in that the tension measurement means is incorporated with one or each of the couplings (10, 11) . 18. A tensioning device according to any preceding claim, characterised in that means is provided for checking the tension in the or each coupling (10, 11) after tensioning has taken place. 19. A tensioning device according to any preceding claim, arranged or adapted to apply tension to tendons having a range of diameters. 20. A method of tensioning a tendon, comprising the steps of applying to the tendon (2) a tensioning device in accordance with any of claims 1 to 19, the first coupling (10) of the tensioning device being attached to the tendon adjacent one end (7) , an opposite end of the tendon being anchored, the second coupling (11) being attached to an anchorage separate from said one end, and operating the load applying means of the tensioning device to cause the one coupling to be urged towards the other so as to tension the tendon (2). 21. A method according to claim 19, characterised in that the second coupling (11) is attached to the anchorage, and the anchorage is tensioned simultaneously with the tendon (2) . 22. A method according to claim 20, characterised in that the second coupling (11) is attached to a second tendon (3) , and the second tendon (3) is tensioned simultaneously with the first tendon (2). 23. A method according to any of claims 20 to 22, applied to a tendon having a tension retaining means (4) attached at the one end, the tension retaining means (4) being continuously adjusted as the tendon is tensioned by the tensioning device. 24. A method of measuring the tension of an already tensioned tendon, the tension is the tendon being retained by a tension retaining means, comprising the steps of applying to the tendon a tensioning device in accordance with the foregoing first aspect of the invention, the first coupling of the tensioning device being attached to the tendon adjacent one end, an opposite end of the tendon being anchored, the second coupling being attached to an anchorage separate from said one end, and operating the load applying means of the tensioning device to cause -the one coupling to be urged towards the other until the tension in the tendon is no longer retained by the tension retaining means.

Inventors: EGGINTON PAUL RAYMOND, GETHINGS MICHAEL SHAUN BRIAN, EGGINTON, PAUL, RAYMOND, GETHINGS, MICHAEL, SHAUN, BRIAN
Applicants: EGGINTON PAUL RAYMOND, GETHINGS MICHAEL SHAUN BRIAN, HYDRAULIC TENSIONING TECHNOLOG, EGGINTON, PAUL, RAYMOND, GETHINGS, MICHAEL, SHAUN, BRIAN, HYDRAULIC TENSIONING TECHNOLOGY LIMITED
Application year: 1998
Main classification: E04C5
IPC codes: E04C5, E04G21