Corrosion-protected tension member and plastically deformable disc of corrosion protection material for such a tension member

Abstract

A corrosion-protected tension member (10) comprises a plurality of tension elements (14) and an anchor device (44) with an anchor element (16) which is designed to transmit tension forces from the tension elements (14) to a superior structure (12), at least one elastically compressible sealing disc (28), and a supporting device (26) which is arranged on that side of the at least one sealing disc (28) which faces away from the anchor element (16). According to the invention, when the tension member (10) is in a state in which it is preassembled but not yet placed under tensile stress, at least one plastically deformable disc (30) of corrosion protection material is arranged between the anchor element (16) and the at least one sealing disc (28).

Claims

1. A method for providing a corrosion-protected tension member, the method comprising: providing tension elements and an anchor device including an anchor element, at least one resiliently compressible sealing ring arranged on a side of the anchor element facing away from free ends of the tension elements after the tension elements have been passed through the anchor device, a support device arranged on a side of the at least one sealing ring facing away from the anchor element, and at least one plastically deformable disc made of an anti-corrosion material and arranged between the anchor element and the at least one sealing ring; passing the tension elements through the anchor element, the at least one resiliently compressible sealing ring, the support device and the at least one plastically deformable disc while the tension member is in a first state in which the tension member is pre-assembled but not yet under tensile stress such that the anchor element is in contact with the tension elements to absorb tensile forces therefrom when the tension member is in a second state in which the tension member is fully assembled and stressed; and exerting a tensile force on the tension elements in a longitudinal extension direction of the tension elements which compresses the sealing ring and the at least one plastically deformable disc resulting in the anti-corrosion material being pressed into gaps and cavities in the tension member, wherein providing the tension elements and the anchor device further includes providing the at least one plastically deformable disc having no through-holes, and passing the tension elements through the anchor element, the at least one resiliently compressible sealing ring, the support device and the at least one plastically deformable disc further includes penetrating the at least one plastically deformable disc resulting the tension elements being wetted with the anti-corrosion material on a surface thereof.

2. The method of claim 1, wherein providing the tension elements and the anchor device further includes providing the anchor device such that the at least one plastically deformable disc rests directly on the anchor element when the tension member is in the first state.

3. The method of claim 1, wherein providing the tension elements and the anchor device further includes providing the at least one plastically deformable disc being made of microcrystalline wax.

4. The method of claim 1, wherein providing the tension elements and the anchor device further includes providing the at least one plastically deformable disc, wherein the volume of the anti-corrosion material per tension element is at least equal to the product of the length of the anchor element in the longitudinal extension direction of the tension elements and the surface area of an annulus between each tension element and a through-hole in the anchor element through which each tension element is passed.

5. The method of claim 1, wherein providing the tension elements and the anchor device further includes providing the at least one plastically deformable disc, wherein the modulus of elasticity of the at least one sealing ring and the resistance of the at least one plastically deformable disc to plastic deformation, respectively based on a compression force acting in the longitudinal direction of the tension elements, are matched to each other such that boundary surfaces of through-holes in the at least one sealing ring are in sealing contact on the tension elements before the at least one plastically deformable disc has been deformed by more than 5% of a thickness thereof measured in the longitudinal direction of the tension elements.

6. The method of claim 5, wherein providing the tension elements and the anchor device further includes providing at least one resistance element embedded in the at least one plastically deformable disc which increases a resistance of said plastically deformable disc to plastic deformation.

7. The method of claim 1, wherein providing the tension elements and the anchor device further includes providing the anchor element including a stamp portion which, when the tension member is in the first state, engages in a sleeve in which the at least one plastically deformable disc, the at least one sealing ring and the support device are received.

Description

(1) The invention will be described in further detail in the following, on the basis of the accompanying drawings and with reference to two embodiments. In the drawings:

(2) FIG. 1 is a longitudinal section through a tension member according to the invention which can be used as a tendon, in particular for prestressed concrete structures, when in the fully assembled and stressed state;

(3) FIG. 2 is a longitudinal section of the tension member according to FIG. 1 when in the pre-assembled but not yet stressed state;

(4) FIGS. 3 and 4 are longitudinal sections similar to FIGS. 1 and 2 of another tension member according to the invention which can be used as a stay cable, in particular for cable-stayed structures.

(5) FIG. 1 shows a tendon 10, such as can be used in particular for prestressed concrete structures such as bridges, tanks or towers, as a first embodiment of a corrosion-protected tension member according to the invention, in the state thereof when fully assembled and stressed in the concrete of the prestressed concrete structure 12.

(6) The tendon 10 comprises a plurality of tension elements 14, each of which can be formed of a steel wire strand coated with synthetic resin. Epoxy resin, for example, can be used as the synthetic resin, the tension elements 14 in this case being referred to for short in technical language as epoxy-coated strands.

(7) The tension elements 14 are in tensile-force transmitting contact with an anchor disc 16 which is manufactured from steel for example. For this purpose, the anchor disc 16 is provided with a plurality of through-holes 18 which each have an inner cylindrical portion 18a which transitions into a conical portion 18b on the side facing away from the prestressed concrete structure 12. Each of the conical portions 18b is used to receive a multipart tapered collar 20 which encompasses the associated tension element 14 with a positive and non-positive fit and transmits the tensile forces from the tension element 14 to the anchor disc 16.

(8) The anchor disc 16 is supported on the outer surface 12a of the structure 12 by means of an abutment flange 22a of a substantially tubular anchor body 22 which is embedded in concrete in the structure 12 and can be manufactured for example as a cast part, in particular made of cast iron. The anchor body 22 forms a tubular covering for the tension elements 14 extending from the surface 12a of the structure 12 towards the inside of the structure 12, which covering can be lengthened, if desired, towards the inside of the structure 12 by means of a further tube 24. A smooth or profiled plastics tube for example, in particular a polyethylene tube, a sheet metal tube or the like, can be used as the further tube 24.

(9) The tension elements 14 which extend inside the structure 12 slightly obliquely relative to the tension axis A of the tension member 10 are deflected by means of a spacer disc 26 arranged inside the anchor body 22 so as to penetrate the anchor disc 16 in a manner extending substantially in parallel with the tension axis A. For this purpose, the spacer disc 26 is provided with a plurality of correspondingly formed through-holes 26a. The spacer disc 26 can be manufactured for example from plastics material, in particular polyethylene.

(10) Furthermore, a sealing ring 28 is arranged on the side of the spacer disc 26 facing the anchor disc 16, which ring in turn comprises a plurality of through-holes 28a for the tension elements 14 to pass through. The sealing ring 28 can be manufactured for example from a soft rubber, for example nitrile butadiene rubber or chloroprene rubber.

(11) When the tension member 10 according to the invention is in the state in which it is fully assembled and stressed, the sealing ring 28 is supported on the spacer disc 26. In order to be able to provide the support for the sealing ring 28, the spacer disc 26 can in turn be indirectly or directly supported on the anchor body 22. In the embodiment shown, said disc is supported on an inner annular shoulder 22b of the anchor body 22 for example. If the internal stability of the spacer disc 26 were not sufficient for this, for example due to too large a diameter, a further support disc, preferably manufactured from metal, could in addition be provided between the spacer disc 26 and the annular shoulder 22b.

(12) As can be seen in particular from FIG. 2, according to the invention a plastically deformable disc 30 made of anti-corrosion material is further arranged between the sealing ring 28 and the anchor disc 16 during assembly of the tension member 10. This plastically deformable disc 30 made of anti-corrosion material can also comprise a plurality of through-holes for the tension elements 14. However, this is not necessarily required. Rather, the plastically deformable disc 30 can also be formed as a complete disc, meaning that the tension elements 14 have to be pushed through the plastically deformable material of the disc 30 during assembly, as a result of which the surface of said elements is, at this time, already wetted with anti-corrosion material.

(13) When stressing the tension member 10, a stamp portion 16a of the anchor disc engages in the anchor body 22 and presses against the plastically deformable disc 30. Since said plastically deformable disc is clamped between the anchor disc 16 and the sealing ring 28 it plastically deforms such that the anti-corrosion material is automatically, i.e. as part of the stressing process, pressed into all the cavities still present in the tension member 10 when said member is unstressed, in particular into the cavities present between the tension elements 14 and the inner walls of the through-holes 18 and in the tapered collars 20. Since these cavities are thus substantially completely filled with anti-corrosion material, penetration of moisture and dirt can be reliably prevented. In order to achieve the same aim, up to now in the prior art the anti-corrosion material has had to be injected later, after stressing the tension member. This was laborious and complex in particular due to the fact that the anti-corrosion material had to be injected into each of the tapered collars in succession, resulting in high assembly costs due to the associated requirement for staff.

(14) In order to be able to prevent the anti-corrosion material from not only being pressed into the above-mentioned cavities but also being able to escape through those cavities between the tension elements 14 and the inner walls of the through-holes 28a in the sealing ring 28 and the through-holes 26a of the spacer disc 26, care must be taken to ensure that the material of the sealing ring 28 is first placed in a sealing manner around the tension elements 14 before the disc 30 made of anti-corrosion material is significantly plastically deformed. This can be achieved for example in that the modulus of elasticity of the sealing ring 28 and the resistance of the plastically deformable disc 30 to plastic deformation, respectively based on a compression force acting in the longitudinal direction of the tension elements 14, are matched to each other with a view to achieving this aim.

(15) FIGS. 3 and 4 show a second embodiment of a tension member according to the invention. In this case, the embodiment according to FIGS. 3 and 4 differs from the embodiment according to FIGS. 1 and 2 mainly in that it does not relate to a tendon 10 such as is used in particular for prestressed concrete structures, but relates to a stay cable such as is used in particular in cable-stayed structures, for example cable-stayed bridges, extradosed bridges or arched bridges. Therefore, in FIGS. 3 and 4 similar parts are provided with the same reference signs as in FIGS. 1 and 2, but increased by 100. In addition, the tension member or the stay cable 110 is described in the following only to the extent that it differs from the tendon 10 of FIGS. 1 and 2, to the description of which reference is otherwise explicitly made hereby.

(16) The tension member or stay cable 110 comprises a plurality of individual tension elements 114, each of which can be formed for example as monostrands. In this case, a monostrand is understood as a single strand formed from seven wires and surrounded by a cladding of plastics material, preferably polyethylene, the intermediate space between the wires and the cladding being filled with anti-corrosion material, for example anti-corrosion grease.

(17) The tension elements 114 are in tensile force-transmitting contact with an anchor disc 116 manufactured from steel for example. For this purpose, the anchor disc 116 is provided with a plurality of through-holes 118, like the anchor disc 16 of the embodiment according to FIGS. 1 and 2. Conical portions 118b of the through-holes 118, which are connected to cylindrical portions 118a, are used to receive tapered collars 120 which encompass the tension elements 114 with a positive and non-positive fit. In order to be able to prevent the cladding of the tension elements 114 from adversely affecting the engagement of the tapered collars 120 with said tension elements, in practice the cladding of the tension elements 114 is removed at the point at which the tapered collars 120 are arranged. This can be seen in FIGS. 3 and 4 from the fact that, in the portions of the tension elements 114 (on the left-hand side in FIGS. 3 and 4) in which the cladding has been removed, the torsion of the wires of the strands is indicated by oblique lines, whereas the tension elements 114 in the clad portions (on the right-hand side in FIGS. 3 and 4) are shown having smooth walls. In addition, it has been found to be advantageous to arrange spacer sleeves 140 on the strands, between the end of the cladding and the tapered collars 120.

(18) The outer peripheral surface of the anchor disc 116 is provided with a thread 116b, on which a ring nut 142 is screwed. The anchor disc 116 and the ring nut 142 together form an anchor device 144 which is supported on the outer surface 112a of the structure 112 via a bearing plate 122. More precisely, the anchor device 144 is supported on the bearing plate 122 by means of the ring nut 142. The bearing plate 122 can be manufactured from steel for example. Furthermore, said plate can be inserted in a recess in the structure 112 provided for this purpose, or can be embedded in concrete in the structure 112. In principle, however, the anchor device 144 can also be directly supported on the structure 112.

(19) Regarding the embodiment of FIGS. 1 and 2, it should also be added that the anchor device 44 there consists purely of the anchor disc 16.

(20) A tube 124 can be connected to the bearing plate 122 inside the structure 112, which tube protects the tension elements 114 from the concrete of the structure 112. The tube 124 can be a smooth or profiled plastics tube for example, in particular a polyethylene tube, a smooth or profiled metal tube, in particular a steel tube, or the like.

(21) It should further be noted that the anchor disc 116 is connected to a further tube 146 inside the concrete of the structure 112. The further tube 146 can be screwed onto the anchor disc 116 for example or welded thereto. A spacer disc 126 is received in this further tube, which spacer disc deflects the tension elements 114, which extend slightly obliquely relative to the tension axis A of the tension member 110 inside the concrete of the structure 112, such that said tension elements penetrate the anchor disc 116 in a manner extending substantially in parallel with the tension axis A. For this purpose, the spacer disc 126 is provided with a plurality of correspondingly formed through-holes 126a. The spacer disc 126 can be manufactured from plastics material for example, in particular polyethylene.

(22) In the embodiment shown, three sealing rings 128 are arranged on the side of the spacer disc 126 facing the anchor disc 116, which sealing rings likewise comprise a plurality of through-holes 128a for the tension elements 114 to pass through. The sealing rings 128 can be manufactured for example from a soft rubber, for example nitrile butadiene rubber or chloroprene rubber. In principle, however, it is also conceivable to use fewer or more than three sealing rings.

(23) In the fully assembled and stressed state of the tension member 110 according to the invention, the sealing ring 128 which is furthest from the anchor disc 116 is supported on the spacer disc 126. In order to thus be able to act as an abutment for the three sealing rings 128, the spacer disc 126 is in turn supported on a support disc 148 which is preferably manufactured from metal. The support disc 148 is in turn held on the anchor disc 116 by means of a plurality of threaded rods 152 fitted with threaded nuts 150, 151.

(24) As can be seen in particular from FIG. 4, during assembly of the tension member 110 according to the invention, a plastically deformable disc 130 made of anti-corrosion material is further arranged between the sealing ring 128 closest to the anchor disc 116 and the anchor disc 116. This plastically deformable disc 130 made of anti-corrosion material can also comprise a plurality of through-holes for the tension elements 114. However, in the same way as in the embodiment of FIGS. 1 and 2, this is not necessarily required. Rather, the plastically deformable disc 130 can also be formed as a complete disc, meaning that the tension elements 114 have to be pushed through the plastically deformable material of the disc 130 during assembly, as a result of which the surface thereof is wetted with anti-corrosion material.

(25) A further difference between the embodiments of FIGS. 1 and 2 on the one hand and FIGS. 3 and 4 on the other hand consists in the fact that, in the case of the tension member or stay cable 110, the process of stressing the tension elements 114 is separated from the process of activating the sealing rings 128 and the plastic deformation of the disc 130 made of anti-corrosion material, whereas both processes take place simultaneously according to the above description of the tension member or tendon 10 of FIGS. 1 and 2.

(26) After the tension member 110 has been stressed, the sealing rings 128 can be activated and the disc 130 made of anti-corrosion material can be plastically deformed, whereby the threaded nuts 151 of the threaded rods 152 are tightened. Since the disc 130 is clamped between the anchor disc 116 and the sealing rings 128, said disc plastically deforms such that the anti-corrosion material is automatically, i.e. as part of this second stressing process, pressed into the cavities still present in the tension member 110 when said member is unstressed, in particular into the cavities present between the tension elements 114 and the inner walls of the through-holes 118 and in the tapered collars 120. Again, the subsequent injection of anti-corrosion material after the tension member has been stressed, which has been necessary up to now in the prior art, can be eliminated in this manner.

(27) Furthermore, in this case, in the embodiment of FIGS. 3 and 4 there is also the risk that the anti-corrosion material is not only pressed into the above-mentioned cavities but is also able to escape through those cavities between the tension elements 114 and the inner walls of the through-holes 128a in the sealing rings 128 and the through-holes 126a of the spacer disc 126. Again, this can be prevented in that care is taken to ensure that the material of the sealing rings 128 is first placed in a sealing manner around the tension elements 114 before the disc 130 made of anti-corrosion material is significantly plastically deformed. This again can be achieved for example in that the modulus of elasticity of the sealing rings 128 and the resistance of the plastically deformable disc 130 to plastic deformation, respectively based on a compression force acting in the longitudinal direction of the tension elements 114, are matched to each other with a view to achieving this aim. However, it is also possible to embed at least one resistance element 154 in the plastically deformable disc 130, which element increases the resistance of said disc to plastic deformation, in a manner which is adapted to the modulus of elasticity of the sealing rings 128.

(28) Of course, at least one resistance element of this kind can also be used in the embodiment according to FIGS. 1 and 2.

(29) Regarding both embodiments, it should also be added that the free ends 14a and 114a, respectively, of the tension elements 14 and 114, respectively, projecting out of the anchor disc 16 and 116, respectively, can be protected from external influences, in particular weather-related influences, by means of a cap (not shown) which can preferably be filled with anti-corrosion material. The fixing points for said cap are provided on the abutment flange 22a in the embodiment of FIGS. 1 and 2 and are denoted by 56 therein, whereas they are provided on the ring nut 142 in the embodiment of FIGS. 3 and 4 and are denoted by 156 therein.