DE3925368A1 - Tension application to prestressing cables of concrete structure - using conical wedges to apply and maintain initial partial tension - Google Patents

Abstract

A pre-stressed concrete structure is pre-stressed by means of a bundle of steel cables (19-24) which are threaded one at a time through a tubular housing (1). In order to prevent cables, as they are being inserted, from digging into previously inserted cables, each cable is fed through a hole in a circular plate (9). This circular plate (9) is provided with conical wedges which grip the cable (20) and apply a partial tension. This partial tension is maintained on each cable until all the cables have been threaded into the housing and the full tension is applied to all the cables. USE - Pre-stressed concrete structures.

Description

The invention relates to a method for threading clamping steel for bundle tendons in unidirectionally curved tendons channels according to the preamble of claim 1.

Another aspect of the invention relates to a device for threading prestressing steel into unidirectionally curved prestressing channels according to the preamble of claim 3, for exercise of the method according to claims 1 and 2 is suitable.

The invention has the following background: High pre-stressed concrete tanks for storing liquids or bulk goods are almost always by means of sliding or Climbing formwork made. It is difficult during the Reinforcement work to lay the long tendons. Therefore, in most cases, when manufacturing the Empty walls of the casing are laid after the completion the concrete works are filled with prestressing steel. The walls of low containers or protective cups are often in Segments made to use formwork several times can. With this design, it is essential that the Manufacture the walls to insert empty cladding tubes only after concreting the last segment of the circle Prestressing steel can be filled. For filling the clamping channels, i.e. The following method is known for threading the prestressing steels: The prestressing steels are next to the container or in one Prestressing steel mill cut to length and bundled. The prestressing steel bundle is wound up on a drum and with the crane in front of the Tendon opening raised. At the other tendon end a winch installed. The winch rope is made using a Pilot wire that previously pushed through the tensioning channel was pulled into the tension channel. Then with the winch Prestressing steel bundle drawn into the prestressing channel. - This The procedure is therefore difficult to carry out and is therefore complex.  

In another prior art method according to the method according to the preamble of the claim 1 are therefore the prestressing steels in the prestressing channel with the help of a slot machine that is pushed in front of the tendon opening is installed. The slot machine pulls the instep steel from a prestressing steel ring and presses the prestressing steel in the tension channel. If the prestressing steel on the other side of the tensioning channel has arrived, it will be at the slot Cut off tendon side. Then the slot can automat the next prestressing steel in the prestressing channel in the same Press way. - The latter procedure is less complex and considerably faster than that above known known methods, but here is the possibility speed that the prestressing steels between the Grind prestressed steels already inserted and the prestressing channel To block. The prestressing steels normally fill the cladding tube due to their weight from the bottom up, and during the on the next prestressing steel slides on the already inserted prestressing steel. However, since the instep steels lie in the cladding tube or tensioning channel without tension, a prestressed steel inserted subsequently into a gap get between two adjacent prestressing steels, push these prestressing bars aside and thus between clamp the already inserted prestressing steel, which in is highly undesirable.

Regardless of whether the prestressing steel after the first or second known methods have been threaded for tensioning the prestressing steel bundles all prestressing steels one Bundle simultaneously from the clamping press on the protruding one Gripped end of the tendon, which from the tension channel was pulled out or pushed out. By the successor All tensioning steels lie on the inside  of the cladding tube. The prestressing steels get that rest on the inside of the cladding tube from the start, a greater elongation than the prestressing steels that initially follow pulling in or pushing in further outside in the cladding tube lie and therefore initially inward during the tensioning process be pulled before they get the final tension. As a result, there can be a significant difference in elongation between an originally adjacent to a tension channel Prestressing steel and an outer prestressing steel arise per proportional to the wrap angle of the tendon in the unidirectionally curved clamping channel multiplied by the radi An external prestressing steel is back in the cladding tube before placing it like an inner prestressing steel in the cladding tube on the inside is present.

The present invention is based on the object To further develop methods of the type mentioned at the beginning, that the individual prestressing steels when pressed into the Clamping channel not in the previously pressed clamping steel can dig and that in the subsequent tensioning of the prestressing steel bundle all inserted prestressing steels in evenly pretensioned in the unidirectionally curved tension channel even though all prestressing steels in a bundle are the same be caught in time by the clamping press.

This task is accomplished through further training of the procedure solved according to the characterizing part of claim 1.

The advantages remain through the further development of the process the threading of prestressing steels by pressing in the prestressing steel in the tensioning channel by means of a slide-in machine largely preserved, but also the risk of Is removed and it is ensured that the Applying the final preload simultaneously and tensioned prestressing steels even among themselves  Get tensile stresses and strains.

According to the method according to the invention, each prestressing steel immediately after it was pressed into the tensioning channel, i.e. before the next prestressing steel is pressed into the cladding tube is tensed with a low tension, which here too Primary clamping force is called. The primary clamping force is typically 5-15% of the final preload and is everyone if smaller than this. By applying the primary chip The individual clamping is determined by the primary clamping force after insertion, steel so pulled together that the radially outer side within the unidirectional curved cladding tube or tensioning channel a free sub-channel is kept open. Due to the primary bias of the already inserted prestressing steel can be the following incoming prestressing steel not between the strained prestressing steel digging. Because the prestressing steels are preferred in the prestressing channel are individually strained with the same primary voltage a previously existing different lots of the individual Prestressed steel removed. When applying the final Preload for all prestressing steels in the prestressing channel at the same time, these prestressing steels receive the same final resilience.

A is used to practice the method according to the invention Device according to claim 3, which consists essentially of a Threading chair with the in the characterizing part of claim 3 specified features exists.

The design of the threading chair is uncomplicated and can be realized with little effort. The Handling the threading chair is so simple that the reason additional, known advantages of using an insert automaton, which is used to thread the prestressing steel into the one-way curved clamping channel is used to be preserved.  

In detail, the threading chair has a second wedge carrier - in addition to the usual first wedge carrier, which is support on a pressure distribution plate of a building can - on who is set up to temporarily and supported indirectly on the pressure distribution plate. The Threading chair carries the second wedge carrier, which with the Primary stresses that are charged to the individual the tensioning channel and the threading chair steels are applied. The threading chair supports the second Wedge carrier before the first wedge carrier the primary stresses the individual prestressing steels takes over by the second wedge carrier on the threading chair in the direction of the pressure distributor plate is moved.

The second wedge carrier on the threading chair is so far in Movable towards the pressure distribution plate that the primary clamping force on the threaded tensioned Can put prestressing steels on the first wedge carrier, which the final wedge carrier.

The axial displacement of the second wedge carrier is realized according to claim 5 in an uncomplicated manner, that the threading chair has a tube, the first end is supported on the pressure distribution plate and at the second end, a piece of pipe adjustable in the axial direction is held, which carries the second wedge carrier.

In particular, the pipe section in the pipe by means of a Screw connection according to claim 6 held axially adjustable be. - The pipe section is subject to axial adjustment a helical movement, the circumferential component but is not transferred to the second wedge carrier.

For this purpose, the device is expedient according to claim 7 forms, after which the second wedge carrier is a plate which  is rotatably supported relative to the pipe section. The pipe piece is rotatable relative to the plate, which is on the pipe section supports under the action of the primary clamping force. The swivel speed of the pipe section opposite the plate in which the clamping steels are wedged, can be due to sliding surfaces on the forehead side of the pipe section and the plate can be realized or through a bearing between the pipe section and the plate, the can be round but not necessarily.

According to claim 8 is the first in the tube of the threading chair Wedge carrier slidable and lockable. The wedge carrier will so long in a position between the pressure distribution plate and the second wedge carrier locked until all prestressing steels are threaded and the prestressing steels with the second wedge carrier are wedged. The prestressing steels run through without wedging through the first wedge carrier. Only when all prestressing steel after Application of the individual but equal primary clamping forces are wedged in the second wedge carrier, the first Wedge carrier in its position adjacent to the pressure distributor after the lock has been released. After the prestressing bars in the first, final wedge beam are wedged, the second wedge carrier is released, see above that the primary clamping force on the final wedge beam is discontinued. Then the wedges on the second Wedge carrier removed and the second wedge carrier removed will. The entire threading chair is reusable, after it has been detached from the pressure distribution plate.

In one variant, the threading chair can be used instead of the one Thread rotatable pipe section according to claim 10 with a Hollow piston press be formed, the pistons in one extended position to support the second wedge carrier serves on the pressure distribution plate when the individual Primary forces are applied and the tense with it Prestressing steels are wedged in the second wedge carrier. The  individual primary clamping forces are in each variant of the Threading chair applied with a single wire tensioner. - The first wedge carrier is between the hollow piston press and the pressure distribution plate locked. After all instep steels wedged in the second wedge carrier under primary tension and the first wedge carrier after releasing the lock the pressure distribution plate is pushed, and the prestressing steels are wedged to the first, final wedge carrier, the Hollow piston of the hollow piston press are withdrawn so that here too the primary clamping force on the final wedge carrier is discontinued.

To thread the individual prestressing steels into the second To facilitate wedge supports are the hollow in the hollow piston Piston press according to claim 11 useful pipes in parallel arranged to each other, in each of which thread a prestressing steel is cash. The pipes can be at the end where the Prestressing steels are introduced to be expanded.

So that the hollow piston of the hollow piston press to release the Wedges on the second wedge carrier retracted sufficiently can be, the hollow piston press is advantageous with a hydraulic return.

The threading chair is, as described, on a tendon arranged at the end, which is a slide-in tendon side is opposite.

If necessary, the threading chair can also be useful on the insert tendon side. this applies especially if the wedge carrier is offset on this side should be because at the prestressing steel end of the stranded wire formed prestressing steel a shoe should be applied so the stranded wire when inserted into and through the  Tension channel not unraveled or the tension channel damaged.

Two embodiments of the threading chair according to the invention are based on a drawing with three figures explained. Show it:

FIG. 1 is a horizontal section through a first form of exporting approximately Einfädelstuhls, wherein the Einfädelstuhl above and below a center line of a center line is shown in two different operating phases;

FIG. 2 shows a cross section through the threading chair along the sectional plane AA in FIG. 1, a situation corresponding to that in the upper part of FIG. 1 being shown on the right of a vertical plane BB and a situation on the left of the vertical plane BB which corresponds to that in the lower part of FIG. 1, and

Fig. 3 shows a second embodiment of the threading chair each above and below a center line also in two different phases.

The illustrated in Fig. 1 and Fig. 2 of the first embodiment Einfädelstuhls is generally indicated 1. It comprises a tube 2 , in which mounting openings 3 are cut. The tube is fixed to a pressure distribution plate 4 which abge on a not shown insertion machine facing side clamping member is embedded in a structure. 5 Contrary to this fastening end of the threading chair, the tube 2 is provided with a thread 6 , into which a tube piece 7 is screwed, which has a corresponding thread. At the end of the pipe section 7 , a round plate 9 is attached with a detachable holder 8 , which has receiving holes 10 for wedges 11 . The round plate 9 is attached to the pipe section 7 so that the pipe section can rotate relative to the support plate. For this purpose, the contact surfaces of the pipe section and the round plate are designed as sliding surfaces 12 , which represent a sliding joint.

The round plate 9 forms a second wedge carrier in addition to a first wedge carrier 13 , which absorbs the final prestressing force. As shown in the upper part of FIG. 1 above a center line 14 , the first wedge carrier can be locked between a stop 15 and a screw 16 . The wedge carrier and the wedge receiving openings 17 let into it can be reached through the mounting openings 3 .

The threading chair 1 is mounted on the pressure distribution plate 4 in such a way that the center line 14 of the threading chair is aligned with a center line of a tensioning channel 18 .

In a drawing part of FIG. 1 above the center line 14 , the situation on the threading chair during the pushing of individual prestressing steels, of which prestressing steels 19 and 20 are numbered, is shown. The prestressing steels are designed here as tension wire strands. - Before inserting the prestressing steel, the first wedge carrier 13 , which serves for the final anchoring of the prestressing steel, is pushed up to the stop 15 and secured by the screw 16 . The pipe section 7 is turned out of the pipe 2 . In this form, the threading chair 1 was attached to the pressure distribution plate 4 .

Now the prestressing steels are inserted one after the other from the end of the tensioning channel 18 , not shown, so that they emerge from the pressure distribution plate 4 and can be threaded through the first wedge carrier 13 and the round plate 9 . The end of the prestressing steel emerging from the plate is tightened with a single wire tensioning device 21 , so that first a lot of the prestressing steel, here the prestressing steel 20 , is eliminated in the curved tensioning channel 18 and then tensioned under further tension by the tensioning device with a primary tension, which is significantly less than the final preload. The primary tension is maintained in the prestressing steel until further notice by inserting a wedge 11 into the receiving hole 10 of the round plate 9 as a second wedge carrier. This situation is shown in conjunction with the prestressing steel 19 . Then another prestressing steel can be threaded, and tightened with the single-wire clamping head, whereby a primary tension is retained after the slack has been removed. After all prestressing steels are threaded and primarily prestressed - this situation is shown for part of the prestressing steels in the right part of FIG. 2 - the first wedge carrier 13 is pushed onto the pressure distribution plate 4 and wedges 22 are in this position of the wedge carrier 13 in this assembled. After all prestressing steels, of which prestressing steels 23 , 24 are designated in FIGS . 1 and 2, are wedged in the first wedge carrier 13 - see also left part of FIG. 2 - the primary clamping force is released onto the wedge carrier 13 by the pipe section 7 is screwed into the tube 2 . As a result of the primary tension, the round plate 9 is not rotated, but only moves in the axial direction towards the primary wedge carrier 13 . The primary clamping force is thus converted onto the wedge carrier 13 . This situation is shown in the lower part in FIG. 1.

The wedges 11 on the round plate 9 can then be dismantled and the threading chair 1 can be dismantled overall.

The final prestressing force is applied in a conventional manner to the prestressing steel ends which protrude from the first wedge carrier 13 .

In Fig. 3, a second embodiment of the threading chair 1 a is shown, which is constructed using a hollow piston press 25 . The same parts are provided with the same reference numerals in FIG. 3 as in FIG. 1.

The hollow piston press comprises a piston 26 which is displaceable in a cylinder which is not designated. The hollow piston press 25 is fastened by a support part 27 at a distance from the pressure distribution plate 4 on this. Between the hollow piston press 25 and the pressure distribution plate, the first wedge carrier 13 is displaceable and can be locked in the situation shown in the upper part of FIG. 2 between a stop 28 and a screw 29 . In the hollow piston there is an arrangement of tubes 30-33 lying parallel to one another with an enlarged end facing the tensioning channel 18 , which serve for easier threading of the prestressing steels. The tubes lead to wedge receiving holes, for example 10 , in the plate 9 , which is attached to the end face of the hollow piston 26 by means not shown.

As in the first embodiment, the prestressing steels, for example the prestressing steel 19 , are tightened immediately after threading through the threading chair and in particular the hollow piston 26 with the wire tensioning device 21 and slightly tensioned under a primary tensioning force. This situation is shown in the upper part of FIG. 3 above the center line 14 .

In order to convert the primary clamping force from the plate 9 to the first wedge carrier 13 , the hollow piston 26 is retracted so that the wedges 11 can then be released from the plate 9 .

In the lower part of FIG. 3, the latter situation is Darge.

The threading chairs described and those exercised with them Procedures can be used for all bundle tendons either consist of tension wire strands or tension wires will.

The arrangement of the threading chair on the Tendon end, which is the tendon side on which the Slot machine stands, is opposite. In many cases, in which the prestressing steels on the side of the automatic slide-in unit not be anchored directly in the wedge beam on the structure use of the threading chairs is also recommended on the side of the slot machine. The latter applies if the prestressing steels at the transition from a transition pipe to can get caught in a cladding tube or the prestressing steel with a Be provided shoe, which the final wedge carrier too is to move.

Claims (14)

1. A method for threading prestressing steels for bundle tendons into unidirectionally curved prestressing channels, in which the prestressing steels are pressed into the prestressing channel, characterized in that the prestressing steel (for example 20 ) is strained with a primary tension after the pressing in and before the pressing in of the next prestressing steel is, which is smaller than the final preload applied later and is maintained until the final preload is brought up. 2. A method for threading according to claim 1, characterized in that the prestressing steels ( 19 , 20 , 23 , 24 ) are individually strained with the same primary tension. 3. Means for threading prestressing steel for bundle tendons in unidirectionally curved tensioning channels in connection with a first wedge carrier which can be supported on a pressure distribution plate of a building under the tensioning force of the prestressing steel, characterized in that the device has at least one threading chair ( 1 ) with a second wedge carrier ( 9 ), the distance to the pressure distribution plate ( 4 ) under a primary clamping force, which is smaller than the final biasing force, can be supported and arbitrarily displaced in the direction of the pressure distribution plate ( 4 ). 4. Device according to claim 3, characterized in that the second wedge carrier ( 9 ) on the threading chair ( 1 ) so far in the direction of the pressure distribution plate ( 4 ) is displaceable that the primary clamping force of the first, on the pressure distribution plate ( 4 ) applied wedge carrier ( 13 ) is added. 5. Device according to claim 3 or 4, characterized in that the threading chair ( 1 ) has a tube ( 2 ), the first end of which can be supported on the pressure distribution plate ( 4 ) and at the second end a tube piece ( 7 ) adjustable in the axial direction is held, which carries the second wedge carrier ( 9 ). 6. Device according to claim 5, characterized in that the tube piece ( 7 ) in the tube by means of a screw connection (thread 6 ) is held axially adjustable. 7. Device according to one of claims 3-5, characterized in that the second wedge carrier (9) is a plate which is rotatable relative to the pipe piece (7) and extending piece on the tube (7) is supported. 8. Device according to one of claims 5-6, characterized in that in the tube ( 2 ) of the threading chair ( 1 ) the first wedge carrier ( 9 ) is displaceable and lockable. 9. Device according to claim 8, characterized in that at least one assembly opening ( 3 ) is cut into the tube ( 2 ). 10. The device according to claim 3, characterized in that the second wedge carrier ( 9 ) on a hollow piston ( 26 ) of a hollow piston press ( 25 ) is attached, which can be attached to the pressure distribution plate ( 4 ), and that the first wedge carrier ( 13 ) between the hollow piston press ( 25 ) and the pressure distribution plate ( 4 ) can be locked and after releasing the lock ( 28 , 29 ) on the pressure distribution plate can be moved. 11. The device according to claim 10, characterized in that in the hollow piston ( 26 ) tubes are arranged parallel to each other, into each of which a prestressing steel can be threaded. 12. Device according to claim 10 or 11, characterized, that the hollow piston press with a hydraulic return is provided. 13. Device according to one of claims 3-12, characterized in that the threading chair ( 1 ) is arranged at a tendon end, which is opposite an insert tendon ent. 14. Device according to one of claims 3-13, characterized, that the threading chair on the insert tendon side is arranged.