EP0314927B1 - Anchoring device for a tensioning member and method of anchoring - Google Patents

Abstract

Fibre composite prestressing element, and method and device to tense and anchor such a prestressing element, in which the ends of the prestressing element are embedded using synthetic-resin mortar in a transversely corrugated anchoring or prestressing sleeve, which is deformed during the tensing and permits cracks caused by stretching the prestressing bars inside the sleeve, which cracks subdivide the anchoring member over part of its length into discs and consequently permit movement of the prestressing bars when subjected to vibratory stresses. After the tensing, the prestressing bars of the prestressing element can be anchored directly in sheath enlargements by means of anchoring mortar. <IMAGE>

Description

The invention relates to an end anchoring of a tendon for prestressed concrete components, ground anchors, rock anchors or the like, which is at least temporarily shifted longitudinally in a cladding tube, which has at least at one end an extension in which a tendon end is embedded with an anchoring mortar. The invention further relates to a method for producing such an end anchor.

For the prestressing of prestressed concrete components tendons with tendons or tendons made of fiber composite materials are used, which have the advantage over tendons with high-strength steel bars or steel wires that they are corrosion-resistant and can also be used in components that are exposed to corrosive liquids or gases . For example, it is advisable to reinforce concrete tanks for chemical liquids with tendons made of fiber composite materials or to use tendons made of fiber composite materials for rock or earth anchors that are exposed to groundwater. With tendons made of fiber composite materials, however, their end anchoring in the concrete of the respective component is difficult, since the tendons or tension wire bundles made of organic or inorganic fiber materials embedded in synthetic resin matrix are sensitive to transverse pressure and are not readily clamped at their ends in the manner known for steel rods and steel wires and under tension can be placed. In addition, the modulus of elasticity of fiber composite materials considerably smaller than the modulus of elasticity of high-strength steels, so that the tendons made of fiber composite materials must be subjected to a large longitudinal expansion in order to achieve a sufficiently high prestress.

An end anchorage for tendons made of fiber composite materials is known (EP-PS 0 025 856), in which the tension wires made of fiber composite materials are held between clamping plates, to which a transverse pressure dependent on the applied tensile force is exerted and at the same time means are provided that the clamping pressure does not rise too high to keep the transverse pressure exerted on the tension wires within permissible limits.

In order to gently grasp tension rods or tension wires made of fiber composite materials at their ends and to apply a tension force, it is also known to accommodate the ends of the tension rods in strong, cylindrical tension or anchor sleeves, where they are embedded in a synthetic resin mortar, which is an adhesive clipper -Connects between the tension rods and the tension or anchor sleeve. In order to transmit the clamping forces introduced into the clamping sleeve by the clamping press to the clamping rods or tensioning wires made of fiber composite materials embedded in the clamping sleeve, a large anchoring length is required so that the rigid clamping or anchor sleeves have a large length. This in turn makes it difficult to wind up the pre-fabricated tendons on the tendon drums that are used to transport the tendons to the construction site.

Above all, however, both known types of anchoring have the disadvantage that the fatigue strength of the tendons is insufficient at the points where the tendons or tendons made of fiber composite materials enter between the clamping plates or into the clamping sleeve of the anchoring.

An end anchorage of the type described in more detail at the outset is also known, in which a tendon is at least temporarily displaceably displaceable in a cladding tube. The cladding tube has an extension at one end in which a tendon end is embedded with an anchoring mortar. (DE-B-1 659 131)

In this known end anchorage, the tendon is coated with plastic at its end to be anchored and anchored with a plastic mortar, which enters into an adhesive connection with the plastic coating of the tendon. Here, polyester or epoxy resins are preferably used, which are mixed with quartz sand, which serves as a filler.

The adhesive connection of the known end anchorage can only be produced in the tensioned state of the tendon. It is therefore only suitable for anchoring the head of a tendon which is stretched with any tensioning device and which is not subjected to any vibration stress. In the case of end anchorages of tendons made of fiber composite materials with a low modulus of elasticity, there is a risk that the tendons will tear off at the beginning of the force transmission path if it is not possible to change the length of the tendon in the plastic mortar. The same problem exists when the tendons are tensioned at their free ends, where they have to be gripped by the tensioning press and somehow clamped in such a way that no excessive transverse pressure is exerted on the fiberglass materials containing glass fibers or carbon fibers.

The object of the invention is to design a tendon made of fiber composite materials so that it can be tensioned and securely anchored with simple means, in particular at the anchoring points it has the required fatigue strength and can also be easily connected to devices for function monitoring.

This object is achieved with the invention in that the tendon made of fiber composite materials has at its end a spacing surrounding it, consisting of a thin-walled corrugated tube or anchoring sleeve, which is filled with an affinity for the fiber composite materials synthetic resin mortar that the adhesive Creates a shear bond between the tendon end and the sleeve, while the anchoring mortar creates the adhesive-shear bond between the tension or anchor sleeve and the cladding tube extension.

The sleeve surrounding the tendon end ensures that the tendon can stretch at its clamped end when the tension is applied by the tensioning device and follows the strains that the tension rods or wires of the tendon suffer when the tension is applied. Here, the synthetic resin mortar adhering to the tie rods can tear at certain longitudinal intervals transversely to the tensile direction, so that the tensile force to be transmitted from the tendon to the concrete is distributed over a larger entry length. The cohesion is not lost here, since the synthetic resin disks formed when the synthetic resin mortar is torn stick to the tendons inside and are held at their outer edge on the cladding tube which surrounds the synthetic resin mortar filling. The resulting mortar discs allow mutual displacement in the direction of force, so that the fatigue strength of the anchor is improved. In addition, the adhesive-shear bond on the inside and outside of the corrugated pipe to the surrounding mortar is considerably higher than with a cylindrical adapter sleeve, and a thin-walled corrugated pipe is much cheaper than thick-walled threaded adapter sleeves or clamp anchoring devices. In addition, the corrugated tube can be easily gripped and clamped by a suitably adapted clamping device.

The clamping or anchor sleeve can be wound from thin-walled sheet metal strips which interlock with folds at their edges. When tightening the windings of the anchor sleeve then give in to the folds.

The clamping or anchor sleeves can be made of sheet steel or aluminum and preferably have a sinusoidal corrugation. The wave crests and troughs of the corrugations expediently run in the circumferential direction of the tensioning or anchor sleeve along a helical line.

The tensioning sleeve of the tensioning element can be gripped by a tensioning device at least on a length corresponding to the working load to be accommodated, which can be screwed onto the tensioning sleeve of the tensioning element with a corrugated pipe threaded socket piece. Here, the corrugated pipe threaded sleeve piece can be glued with a synthetic resin adhesive or mortar in a threaded sleeve of the clamping device. Corrugated pipe threaded sleeve pieces of this type, which can be screwed onto helically shaped corrugated pipes, are commercially available and can be easily obtained and processed.

The cladding tube extensions can be formed from steel, aluminum or plastic corrugated tubes, the inside diameter D of which is greater than the outside diameter of the clamping or anchor sleeves.

When producing an end anchorage according to the invention, the procedure is such that the end of the tendon provided with an anchor sleeve is embedded in the concrete of a component in such a way that the length of the anchor sleeve required for transferring the working load from the tendon to the component is in the concrete and Clamping sleeve with the other end of the tendon fastened therein abuts approximately on the root of the cladding tube extension which passes into the cladding tube, that the prestress is then applied to the tendon by pulling on the clamping sleeve and this is temporarily supported on an abutment part with a support nut, so that at least the Extensions of the cladding tube are filled with the anchoring mortar and that after hardening of the anchoring mortar, the support nut and the abutment part are removed, and the protruding part of the clamping sleeve or the tendon that is pulled out is cut off.

It can be seen that in this method only the length of the anchor sleeve required to transfer the working load from the tendon to the component is in the concrete. The remaining part of the anchor sleeve protrudes into the extension of the cladding tube and, as described above, can follow the expansion of the tie rods which they suffer when the tendon is tensioned, so that in this area the synthetic resin mortar inside the anchor sleeve tears open in disks and that ensures the desired elasticity in the continuous vibration loading of the component.

Instead, however, it is also possible to fully concrete the anchor sleeve at the fixed anchor end of the tendon so that the tie rods or wires are exposed in the region of the cladding tube extension, where they are only after their Tensioning is embedded in the anchoring mortar, which after tensioning is injected at least into the cladding tube extensions at the ends of the tendon in order to produce the adhesive-shear bond between the tendon ends on the one hand and the structure or the cladding tube extension embedded in it.

Since the tie rods are only embedded in the anchoring mortar after they have been tensioned to the working load and until then no relative movement has taken place between the tie rods and the anchoring mortar surrounding them, the bond at the start of the anchoring section is only stressed by the differential stresses resulting from permanent vibration stress and the Stresses result from the working load, so that sufficient fatigue strength is also achieved in this embodiment. In addition, there is the advantage that the anchor sleeve firmly concreted in concrete, which is required to fasten the tie rods during prestressing to the working load, can be kept much shorter, which makes it easier to wind up the tendons prefabricated in the manufacturing plant on transport drums.

A similar procedure can also be used when anchoring the tendon end, which is initially movable longitudinally, on which the prestressing press acts to tension the tendon. Here it is possible to stretch the tendon during tensioning to the working load so that the clamping sleeve with the tendon end fastened in it emerges completely from the cladding tube extension surrounding it, and of course it still has to be grasped by the support nut to keep the tendon end on the Stop abutment part until the final bond between this tendon end and the building part is established. After embedding the tension rod ends freely crossing the cladding tube extension in the anchoring mortar and after it has hardened then the tie rods or tension wires between the rear end of the clamping sleeve and the end face of the component are cut off. The tensioning force is then transferred directly from the tensioning rods or tensioning wires through the anchoring mortar to the prestressed part of the building or the cladding tube extension, which is embedded in this component.

In addition, after the clamping sleeve has been cut off, the tendon rod ends protruding from the prestressed component are free, to which the sensors of a monitoring device can then be immediately attached, which monitor the effectiveness of the tendons in use.

In order to increase the adhesive-shear bond between the anchoring mortar and the cladding tube extension, this cladding tube extension as well as the anchor or adapter sleeves can consist of a steel or aluminum corrugated tube.

In order to facilitate the transport of the tendons to the construction site, the tendons can also be cut to suitable lengths on the construction site, provided at their ends with the anchor or tensioning sleeves and connected to them with synthetic resin mortar, which can then be heated by heating the anchor or Adapter sleeves with infrared radiators, microwave devices or the like. is cured on the spot.

The anchoring described above can be used for prestressing with composite, in which the tendon in its cladding tube is pressed over its entire length with a cement mortar or plastic mortar. However, the anchorage can also be used for pre-stressing without a bond, such as for rock anchors or ground anchors. In all cases, it is necessary that the grout or anchoring mortar, which comes into direct contact with the tendons or tendons made of fiber composite material has a high affinity for them in order to transmit the forces from the tendons or tension wires to the surrounding anchoring parts through a good adhesive-shear bond. Of course, the individual tie rods or tension wires of each tendon must also have a sufficient distance from each other so that they can be completely covered by the mortar.

Fig. 1

eine feste Endverankerung nach der Erfindung für ein Spannglied aus Faserverbundwerkstoffen in einem Betonbauteil nach dem Verpressen der Verankerungsstrecke im Längsschnitt,

Fig. 2

das bewegliche, zu spannende Ende eines Spanngliedes nach der Erfindung mit einer am Bauteil angesetzten Spannvorrichtung vor Beginn des Spannens in einem Teillängsschnitt und

Fig. 3

die Endverankerung des beweglichen Spanngliedendes nach dem Spannen und Injizieren des Verankerungsbereiches im Längsschnitt.

Further features and advantages of the invention result from the following description and the drawings, in which preferred embodiments of the invention are explained in more detail by means of examples. It shows:

Fig. 1

a fixed end anchoring according to the invention for a tendon made of fiber composite materials in a concrete component after pressing the anchoring section in longitudinal section,

Fig. 2

the movable, to be tensioned end of a tendon according to the invention with a clamping device attached to the component before the start of tensioning in a partial longitudinal section and

Fig. 3

the end anchoring of the movable tendon end after tensioning and injecting the anchoring area in longitudinal section.

In the drawings, 10 denotes a tendon which is intended for prestressing a concrete component 11 and consists of a plurality of tendons 12 which are guided essentially parallel to one another. The tendon 10 is laid in a cladding tube 13 at its rear end 13a and at its front end 13b each has an extension 14 or 15. The cladding tube 13 can be made of plastic or sheet steel, but the cladding tube extensions 14 and 15 are expediently made of corrugated steel or aluminum tubes.

The tie rods 12 are accommodated at one, rear end 10a of the tendon 10 in an anchor sleeve 16 which surrounds the tie rods 12 at a distance and is connected to them by a synthetic resin mortar 17 which has a high affinity for the fiber composite material of the tie rods 12. In the exemplary embodiment shown here, the anchor sleeve 16 consists of a longitudinally welded corrugated tube made of sheet steel with a sinusoidal corrugation 18, and the outer diameter d of the anchor sleeve 16 is somewhat smaller than the inner diameter D of the cladding tube extension 14.

It can be seen from FIG. 1 that the anchor sleeve 16 protrudes a little way into the interior of the cladding tube extension 14, but is otherwise firmly concreted in the concrete component 11. As long as the tendon is not tensioned, the cladding tube 13 and the cladding tube extension 14 are empty, i.e. they form a free space in which the tie rods 12 of the tendon 10 can expand freely. The rear end 10a of the tendon 10, which is firmly connected to the anchor sleeve 16 by the mortar 17, is held in the concrete of the component 11.

The front end 10b of the tendon 10 is arranged similar to its rear end in a clamping sleeve 19, in which the tie rods 12 are embedded with a: synthetic resin mortar 17. The clamping sleeve 19 also consists of a corrugated tube with sinusoidal corrugation, the wave crests 20 and troughs 21 of which run along a helix. Like the anchor sleeve 16, the clamping sleeve can consist of a longitudinally welded corrugated steel tube. In the present Trap, however, the corrugated tube is wound from thin-walled sheet metal strips that interlock with folds at their edges.

The clamping sleeve 19 is surrounded by the cladding tube extension 15 at a distance and protrudes to the front a bit beyond the front end face 22 of the concrete component 11. A support nut 23 is screwed onto this protruding, front end 19a of the clamping sleeve 19 and is supported on an annular anchor plate serving as an abutment part 24. On this anchor plate there is also a tensioning device, which is designated in its entirety by 25 and serves to grasp the tensioning member 10 on the tensioning sleeve 19 connected to its front end 10b and to pull it out a little from the cladding tube 13 and thereby pre-tension it.

For this purpose, the clamping device is provided with a threaded sleeve 26 which is screwed onto the front end 19a of the clamping sleeve 19. Since support nuts and threaded sockets, which have a thread fitting on the corrugated pipe thread of the adapter sleeve 19, are not readily available, the support nut 23 and the threaded sleeve 26 are produced in that the threaded opening 28 of a commercially available nut and the threaded opening 29 of a commercially available threaded sleeve Corrugated pipe threaded sleeve pieces 27 are glued in with a synthetic resin adhesive or mortar. The support nut 23 and the threaded sleeve 26 can then be easily screwed onto the free, front end 19a of the clamping sleeve 19, the length L ascertainable by the threaded sleeve 26 and the support nut 23 being as large as the anchoring area l of the anchor sleeve 16, which is the corresponds to the payload to be absorbed.

For tensioning the tendon 10, the clamping sleeve 16 with the tendon rod ends fastened in it is pulled out piece by piece from the cladding tube extension 15. Here, the Clamping sleeve 19 is supported by by adjusting the support nut 23 via an intermediate sliding layer 30, as is known per se when prestressing tendons. Here, the tensioning rods 12 are stretched, this stretching continuing into the inner end 16a of the anchor sleeve and into the inner end 19a of the tensioning sleeve 19. Since the synthetic resin mortar 17 adheres firmly to the tie rods 12, but cannot fully follow the expansion of the tie rods 12, cracks 31 run transversely to the longitudinal direction of the tendon in the synthetic resin mortar and break up the mortar plug at the inner end into more or less thin disks 17 a, but which are held together on their outer circumference by the anchor sleeve 16 or the clamping sleeve 19 (FIGS. 1 and 3). By this disassembly of the synthetic resin mortar plug 17 in disks, the tension rods 12 attain a certain mobility inside the tension sleeve 17 or the anchor sleeve 16, which enables them to elastically absorb vibrations of the concrete component.

After tensioning the tendon 10, the cavities enclosed by the cladding tube extensions 14 and 15 are filled with an anchoring mortar 32, which can also be pressed into the cladding tube 13 if a full bond between the tendon and the concrete component is to be produced. Here, the anchoring mortar 32 indirectly creates an adhesive-shear bond to the corrugated tube of the cladding tube extensions 14 and 15 over almost the entire length of the rear cladding tube extension 14 and in the rear region 33 of the front cladding tube extension 14. In this anchoring area, which is also to be referred to as the “pre-length” and is indicated in FIG. 3 by 33 and in FIG. 1 by 34, the tie rods 12 are only embedded in the anchoring mortar in the already prestressed state. Any dynamic stress that occurs is therefore only slight in this area.

It can be seen that an end anchoring of the front, initially movable end 10b of the tensioning member 10 is also possible in that the tensioning sleeve 19 is completely pulled out of the component 11 until the working load is applied, and then the tensioning rods 12 still located in the cladding tube extension 15 be embedded in the anchor mortar 32. When this anchoring mortar 32 is then completely hardened, the tie rods 12 can be cut through between the pulled-out clamping sleeve 19 and the front end face 22 or the abutment part. You then individually look a little bit beyond the front end face 22 of the concrete component 11 and can then be connected directly to the sensors of a monitoring device, not shown here. Such a sensor connection is of course also possible at the ends 12a of the tension rods 12 if they are embedded in the tension sleeve 19.

The invention is not limited to the exemplary embodiments described and illustrated, but several changes and additions are possible without leaving the scope of the invention. For example, the anchor sleeve 16 at the rear end 10a of the tendon 10, which is to be firmly concreted in, can also be so long that it almost completely fills the cladding tube extension 14. Cracks 31 then appear in the synthetic resin mortar 17 in that region of the anchor sleeve which is located in the interior of the cladding tube extension 14.

Claims (11)

1. An end anchorage of a stressing element for prestressed concrete structural components, ground anchors, rock anchors or the like, which is laid at least temporarily longitudinally displaceably in an encasement tube, which has at least at one end a widening in which a stressing element end is embedded by means of an anchorage mortar, characterised in that the stressing element (10) consisting of fibre composite materials has a stressing or anchoring sleeve (16, 19) at its end (10a, 10b) which consists of a thin-walled corrugated tube and which surrounds this end at a distance, which stressing or anchoring sleeve is filled with a synthetic resin mortar (17) with an affinity for the fibre composite materials and which mortar produces the adhesion-shear bond between the stressing element end (10a, 10b) and the sleeve (16, 19), whilst the anchorage mortar (32) produces the adhesion-shear bond between the stressing or anchoring sleeve (16, 19) and the encasement tube widening (14, 15).
2. An anchorage according to claim 1, characterised in that the stressing or anchoring sleeve (19; 16) is wound from thin-walled sheet metal strips which interlock at their edges by means of seams.
3. An anchorage according to claim 1 or 2, characterised in that the stressing or anchoring sleeve (19; 16) consists of sheet steel, sheet aluminium or plastic.
4. An anchorage according to any one of claims 1 to 3, characterised in that the stressing or anchoring sleeve (19; 16) has a sinusoidal corrugation.
5. An anchorage according to claim 4, characterised in that the corrugation crests (20) and corrugation troughs (21) of the corrugation (18) run in the circumferential direction of the stressing or anchoring sleeve (19; 16) along a spiral line.
6. An anchorage according to claim 5, characterised in that the stressing sleeve (19) of the stressing element (10) can be gripped by a stressing device (25), at least over a length (l) corresponding to the working load to be borne, which stressing device can be screwed on to the stressing sleeve (19) of the stressing element (10) by means of a corrugated tube threaded collar piece (27).
7. An anchorage according to claim 6, characterised in that the corrugated tube threaded collar piece (27) is adhesively bonded by means of a synthetic resin adhesive or mortar in a threaded collar (26) of the stressing device (25).
8. An anchorage according to any one of claims 1 to 5, characterised in that the encasement tube widenings (14, 15) are formed from steel, aluminium or plastic corrugated tubes, the inside diameter (D) of which is greater than the outside diameter (d) of the stressing or anchoring sleeves (19; 16).
9. A process for producing an end anchorage according to any one of claims 1 to 8, characterised in that one end (10a) of the stressing element (10), which end is provided with an anchoring sleeve (16), is embedded in the concrete of a structural component (11) so that the length (l) of the anchoring sleeve (16) which is necessary to transfer the working load from the stressing element (10) to the structural component (11) is situated within the concrete (8), and the stressing sleeve (19) with the other end (10b) of the stressing element (10) fastened in it is seated approximately against the root of the encasement tube widening (15) extending into the encasement tube (13), that the prestress is then applied to the stressing element (10) by pulling on the stressing sleeve (19) and the stressing element is temporarily supported on an abutment part (24) by means of a supporting nut (23), that at least the widening (14, 15) of the encasement tube (13) are then filled with the anchorage mortar (32), and that after the hardening of the anchorage mortar (32) the supporting nut (23) and the abutment part (24) are removed and the pulled-out, projecting part of the stressing sleeve (19) and of the stressing element (10), respectively, are cut off.
10. A process according to claim 9, characterised in that the stressing element (10) is stretched during stressing to such an extent that the stressing sleeve (19) with the stressing element end (10b) disposed within it completely emerges from the encasing tube widening (15) surrounding it, and that the stressing bars or stressing wires (12) are cut off between the stressing sleeve (19) and the structural component (11) after the embedding in the anchorage mortar (32) and after the hardening of the latter.
11. A process according to claim 9 or 10, characterised in that the stressing elements (10) are cut to suitable lengths on the construction site, are provided at their ends (10a, 10b) with the anchoring or stressing sleeves (16, 19) and are bonded to the latter by synthetic resin mortar (17), which is then set in situ by heating the anchoring or stressing sleeves (16; 19).

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