DK2594700T3

DK2594700T3 - Construction cable and method for anchoring such a cable

Info

Publication number: DK2594700T3
Application number: DK12193091.1T
Authority: DK
Inventors: Ivica Zivanovic; Ronan Solet; François Voyat; Philippe Salmon
Original assignee: Soletanche Freyssinet
Priority date: 2011-11-18
Filing date: 2012-11-16
Publication date: 2017-05-22
Also published as: FR2982890B1; EP2594700B1; EP2594700A1; FR2982890A1; ES2623921T3

Description

CONSTRUCTION CABLE AND PROCESS FOR ANCHORING SUCH A CABLE

This invention relates to construction cables used in building and more particularly methods for anchoring them to building work.

Many systems used for anchoring construction cables made up of multiple reinforcements leave a rear end of the cable accessible, whereby it is possible to hold and/or pull free ends of the reinforcements (contrary to their active portions intended for tensioning and to lock them. The locking is often carried out by means of truncated cone-shaped jaws.

However, the topology of the work to be fitted with the construction cable or other constraints inherent in the design or site can prevent access to the rear end of the anchorage. A technique called embedded anchoring is then used. With such an anchorage, access is gained, on the front (opposite) end, to a cavity formed in the work for accommodating the end of the cable to be anchored and the reinforcements forming the cable are threaded into it.

Embedded anchorages are used in particular in the case of ties used for reinforcing a mass. In this case, access is gained only to a front face of the mass into which a reinforcing cable is inserted. Another case of an application is that of the pre-stressing of a concrete wall cast in situ without access to the lower face of the bed or support accommodating the wall.

French patent no. 693 873 describes an embedded anchoring system for a cable with parallel wires, comprising a cavity in which the ends of the cable wires are inserted, these wires being caused to separate from one another and then cement is injected to fix the whole. Each individual wire subjected to tensile forces is held in the cavity essentially by longitudinal adhesion, which can be insufficient. To obtain sufficient separation of the cable wires, it is also necessary to form a very long cavity. This limits the applications of this anchoring system, particularly when there is not sufficient space for forming a long cavity, in consideration of the type of work, the configuration of the surrounding land, etc. A shorter embedded anchorage is described in European patent no. 0 935 034. To use this anchorage, each reinforcement of the cable must be provided with an end portion in a special form, adapted so that the reinforcement can be pushed all the way to the floor of the cavity despite the presence of other reinforcements already introduced. The reinforcements are introduced one by one so that they find their spaces on the floor of the cavity. Implementing such an anchoring process is lengthy and delicate.

Therefore, there is a need for an embedded anchoring system which is of simplified implementation and which can be of reduced longitudinal dimensions. A construction cable is proposed, comprising: - reinforcements subjected to tensile stressing, each having an end provided with a widened portion; - a cavity formed in a work provided with the construction cable, the cavity having an opening and at least one portion which is of a section larger than the opening transversely to a longitudinal direction of the cavity and a floor opposite the opening following the longitudinal direction, the said reinforcement ends being lodged in the cavity so that the widened portions of the reinforcement ends are distributed in several layers and possibly staggered following the longitudinal direction of the cavity; and - a fixing material with which the cavity containing the reinforcement ends is filled.

The reinforcements can be inserted all together or in groups, whereby it is possible to proceed quite quickly while well controlling the distribution of the reinforcements with their widened portions inside the cavity. Due to the distribution in several layers, it is advantageously possible to limit the transverse dimensions of the bundle of reinforcements when it is introduced, through the conduit, into the cavity.

In one embodiment, the construction cable also comprises at least one separating element protruding from a floor of the cavity situated opposite the opening following the longitudinal direction, so that the reinforcements spread out in the cavity. The separating element separates the ends of the reinforcements on the floor of the cavity, which ensures their being spread out and makes possible a firm anchorage of the cable with the mass of the fixing material injected into the cavity.

The separating element is, for example, of a conical and/or spherical general shape. It can be mounted on a rod fastened to the floor of the cavity or to the bottom wall directly.

The widened portions of the reinforcement ends can have a shoulder forming an abutment in the direction of the cavity opening. Due to this shoulder, the hardened fixing material can present a high force of reaction to the reinforcements subjected to tensile forces.

Another aspect of this invention relates to building work comprising at least one construction cable as defined above. A further aspect of this invention relates to a process for anchoring a construction cable comprising reinforcements, each having an end provided with a widened portion. The process comprises the following stages: - forming a cavity in building work, the cavity having an opening and at least one portion which is of a section larger than the opening transversely to a longitudinal direction of the cavity; a conduit, joined to the cavity, through which the reinforcements are passed; - introducing the construction cable reinforcements into the conduit following the longitudinal direction, passing the widened portions through the cavity opening; and - filling the anchorage cavity with a fixing material.

In accordance with the invention, the reinforcements are introduced into the conduit (and cavity) in at least one group of several reinforcements, the reinforcements of each group being introduced together into the cavity. In a particular case, all the reinforcements are introduced into the cavity in one single group.

Other particular characteristics and advantages of this invention will appear in the following description of a non-limiting exemplary embodiment, with reference to the attached drawings, in which: - figure 1 is a side view of a pre-stressing reinforcement, one end of which is provided with a widened portion; - figure 2 is a side view of a bundle of such reinforcements; - figure 3 is an axial cutaway view of a part which forms an anchorage cavity; - figure 4 is an axial cutaway view of the part in figure 3, installed in concrete building work; - figures 5 and 6 are views similar to that of figure 4, after introduction of the reinforcements and after the fixing of these in the cavity; and - figures 7 to 10 are views similar to those of figures 3 to 6, illustrating another embodiment of the invention.

Figure 1 illustrates an example of a reinforcement for implementing the invention. The reinforcement 1 consists, in this example, of a strand formed from seven metal wires, of which one end 2 is provided with a widened portion 3. As illustrated in figure 2, reinforcements of this type can be assembled parallel to one another to form a bundle 4 which, once anchored in building work, will form a construction cable.

The widened portion 3 can be created by mechanical treatment directly on the end 2 of the reinforcement if the material and formation of this reinforcement allow. It can also be formed from an end part securely fastened to the end of the reinforcement 1 by, for example, hot-crimping, cold-crimping, welding, bonding, bolting, etc. In the example shown in figures 1 and 2, the end part 3 is in the general form of a cylindrical sleeve, with a shoulder 3' forming an abutment against the active portion of the construction cable, i.e. the portion where the reinforcements work in tension (towards the front end of the anchorage) and another shoulder 3" on the opposite end. The abutments formed by these shoulders 3', 3" are surfaces which are substantially perpendicular to the longitudinal direction X of the reinforcements 1.

In order to limit the dimensions of the cable end and thus assist its introduction into an anchorage cavity, the widened portions 3 of the reinforcements 1 can be distributed in several layers staggered following the longitudinal direction X. In the example shown in figure 2, they are distributed in three layers. This distribution in layers, minimising the total cross section of the bundle 4 of reinforcements, is assisted by the cylindrical form of the sleeves forming the widened portions 3.

Figure 3 shows an example of part 6 which can be used for forming an anchorage cavity 8 in concrete building work. It can consist of a trumplate (a part for diffusing force), of the same type as those commonly used in anchorages of pre-stressing cables, the internal volume of which, of a general truncated cone form about an axis of symmetry Y defines the anchorage cavity 8. This cavity 8 has an opening 9 at its end of smallest section to which is joined the pre-stressing conduit (duct or tube). At the opposite end, of the widest section, it is closed by a bottom plate 10 fastened to the surface of the part 6. This part 6 can have radial or helical ribs 11 which will improve its hold in the surrounding concrete and the transfer of the forces between the cable and structure. The wall or floor 10 of the part 6 can also have one or several injection conduits 12 which can be used for filling the cavity 8 with a fixing product, for example resin, mortar or cement grout.

Figure 4 shows the part 6 after its installation in the concrete building work. The concrete has all been poured (around the conduit and the part 6 and underneath the bottom plate 10), so that the anchorage cavity 8 is accessible only from the opposite end, through the conduit (as for a conventional pre-stressing cable) and up to the opening 9 formed at its end of smallest section.

The pre-stressing duct or conduit 5 is joined to the opening 9 of the cavity 8. This duct 5 shall contain the bundle 4 of reinforcements of the pre-stressing cable (see figures 5 and 6). By way of example, the part 6 can be embedded in the bed of concrete building work, while the prestressing duct 5 is embedded in the concrete wall which is built up above the bed. In this example, the pre-stressing duct 5 and the part 6 are mounted with their longitudinal axis Y parallel to a vertical direction. Before the concrete is poured, care is taken to fit an injection tube 13 which is joined to the injection conduit 12 provided in the part 6, this tube 13 being left accessible from outside once the concrete has been poured. In another example, the injection tube 13 is arranged inside the conduit at the same time as the reinforcements are introduced. In this case, the conduit 12 in the part is closed in advance.

After installation of the conduit 5 and of the part 6 in the concrete building work, it will be possible to proceed with introducing the bundle 4 of reinforcements after concreting. This bundle 4 of reinforcements is introduced from the conduit 5 into the cavity 8 following the longitudinal direction Y, passing the widened portions 3 through the opening 9 until the cable substantially reaches the floor 10 of the internal anchorage cavity 8. This stage is illustrated by figure 5. It can be seen that the arrangement recommended for the widened portions 3 situated at the ends of the reinforcements 1 is such that these reinforcements can be collectively introduced through the opening 9. Due to this, installation of the pre-stressing cable can be relatively rapid while the geometric distribution of the reinforcements 1 in the cavity 8 can be controlled.

In a variant of the process, the bed is concreted first, the opening 9 of the anchorage cavity remaining accessible on the upper face of this bed. In a second stage, the bundle 4 of reinforcements is brought in, surrounded by the duct The lower portion of the bundle 4 of reinforcements is inserted into the cavity 8 through the opening 9, then the duct 5 is joined to the opening 9. Next, the duct 5 is positioned in the mould where the concreting of the wall to be prestressed is to be carried out.

The following stage of the process (figure 6) consists of filling the cavity 8 with a fixing material injected: - by means of the injection tube 13 provided in the concrete of the bed and the injection conduit 12 formed in the wall of the part 6; or - by a tube following the cable conduit up to the active anchorage; or - by a tube installed in the cable conduit, for example placed in the bundle of reinforcements before its threading (introduction of the cable into the conduit).

In general, the fixing product is limited in height as illustrated in figure 6, up to the opening 9 for example, so as to have the free length for subsequent tensioning of the construction cable, the free length then being injected with a product for filling and for protection from corrosion. In the case of the use of individually sheathed and sliding strands (reinforcements), the fixing product can cover the full length of the cable, given that, in the portion limited to the fixing, the reinforcements are stripped and cleaned to make their adhesion possible upon the subsequent tensioning of the construction cable as in the usual case.

Once the fixing product has hardened, the construction cable can be tensioned conventionally, it being pulled at its end opposite the end anchored in the cavity 8. The tensile force on a reinforcement 1 at the anchorage is transmitted to the mass of hardened fixing product by means of the shoulder 3' of its widened portion 3, which forms an abutment in the direction of the cavity opening 9. In view of the section, greater than that of the opening 9, which this mass of hardened fixing product 15 has, the cable's tensile force is diffused to the structure concrete via the part 6. Once the construction cable is tensioned, the conduit 5 above the limited height is then injected with a filling or fixing product.

As indicated above, the form of the internal anchoring cavity 8 has at least one portion of a larger section than the opening 9 transversely to a longitudinal direction Y. To promote the adhesion of the cable to the fixing product further still, it can be useful to spread out the bundle 4 of reinforcements in the cavity 8. One possibility for doing this is to have recourse to the variant illustrated by figures 7 to 10.

In this variant, the part 6 defining the anchorage cavity 8 is modified to comprise a separating element 16, protruding into the said cavity. In the example shown in figures 7 to 10, there is a separating element 16 on the floor of the cavity 8, mounted on the axis Y. This element 16, positioned in the cavity 8, is fastened at the centre of the bottom plate 10 closing the cavity 8 opposite its opening 9.

Upon the introduction of the bundle 4 of reinforcements (figure 9), the element 16 deflects the reinforcements 1 so that they spread out in the cavity 8. The outcome of this is firmer anchoring of the cable after injection and hardening of the fixing product 15, for example resin, mortar or cement grout, (figure 10). In the variant shown in figures 9-10, the bundle 4 consists of the individually sheathed and sliding strands 17. To assist presentation, the reinforcements 1 of the bundle 4 are illustrated in a quantity of three.

The separating element 16 has an upper portion 14 directed towards the opening 9 of the anchorage cavity 8. This upper portion 14 can be of a spherical and/or conical form to assist the separation of the reinforcements in the bundle. The separating element 16 can be in one single spherical or conical part or be mounted on top of a rod fastened to the centre of the anchorage cavity floor, as illustrated in figures 7-10. It can also be positioned higher, in the direction of the opening 9.

It is also possible to provide several separating elements 16 distributed on the floor 10 or along the anchorage cavity 8 in order to sub-divide and spread out the ends 2 of the bundle reinforcements further still.

Once the reinforcements 1 of the bundle 4 are well distributed in the cavity 8, the cavity 8 and the conduit 5 can be filled with the fixing product in a single operation. This filling is carried out in the direction of the arrow F as illustrated in figure 9, via the injection tube or tubes 13 arranged in the conduit 5, at the same time as the reinforcements are introduced. The fixing product covers all of the bundle (from the floor of the part 6 to the upper end of the slidably sheathed strands). After hardening, the construction cable can be tensioned as shown above.

Irrespective of the embodiment adopted, a relatively short embedded anchorage is finally and effectively obtained and there is also the benefit of introducing all of the cable into the anchorage cavity 8 in a single operation.

In a variant of the process, collective introduction of the reinforcements into the anchorage cavity 8 is retained but this introduction is carried out successively in several groups, not now one single one. In this case, each group, or sub-bundle, of reinforcements is assembled, the spatial distribution of the widened portions 3 being provided at their ends (figure 2), before being introduced into the cavity. This way of proceeding brings some supplementary stages into creating the anchorage but by means of this it is possible to reduce the section of the opening 9, which can improve the strength of the anchorage, depending on its configuration.

Of course, this invention is subject to many variants with regard to its implementation. Although some embodiments have been described, it is understood that it is not conceivable to identify exhaustively all the possible embodiments. These embodiments described are simple illustrations of this invention. Various different modifications can be made to them without departing from the framework of the invention which emerges from the attached claims.

Claims

A construction cable comprising: - reinforcements (1) to which a stress load is applied, each having an end (2) provided with an extended portion (3); a portion (6) serving to form an anchoring cavity (8) disposed in an element provided with the structural cable, the cavity having an aperture (9) and at least one cross-section larger than the aperture transverse to a longitudinal direction (Y) of the cavity, and a bottom facing opening in the longitudinal direction where the ends of the reinforcements are disposed in the cavity; and - a sealing material (15) which fills the cavity containing the ends of the reinforcements, characterized in that the expanded portions (3) of the ends (2) of the reinforcements (1) are divided into several layers displaced in the longitudinal direction (Y). of the cavity (8).

A construction cable according to claim 1, further comprising: at least one spacer (16) projecting into the cavity located opposite the opening (9) in the longitudinal direction (Y) so that the reinforcements unfold within the cavity.

Construction cable according to claim 2, wherein the spacer (16) is attached to the bottom of the cavity (8).

Construction cable according to any one of the preceding claims, wherein the extended portions (3) of the ends (2) of the reinforcements (1) have a shoulder (3 ') adjacent to the opening (9) of the cavity (8). ).

Construction cable according to any one of the preceding claims, wherein the extended portions (3) of the ends (2) of the reinforcements (1) are in a general form of a cylindrical sleeve.

A building structure including at least one structural cable according to any one of the preceding claims.

A method of anchoring a structural cable comprising reinforcements (1), each having an end (2) provided with an extended portion (3), comprising the steps of: - forming a cavity (8) in a building, said cavity has an aperture (9) and at least one portion larger than the aperture transverse to the longitudinal direction (Y) of the cavity; - introducing the reinforcements of the structural cable into the cavity relative to the longitudinal direction by passing the extended portions through the aperture; and - filling the anchoring cavity (8) with a sealing material (15), characterized in that the insertion of the reinforcements into the cavity is carried out in at least one group of several reinforcements, the reinforcements of each group being inserted together into the cavity and by the expanded parts (3). ) of the ends (2) of the reinforcements (1) is divided into several layers displaced in the longitudinal direction (Y) of the cavity (8).

The method of claim 7, wherein the reinforcements (1) are all introduced as a single group into the cavity (8).

The method of claim 7 or 8, further comprising: dividing the extended portions (3) of the ends (2) of the reinforcements (1) into multiple layers displaced relative to the longitudinal direction (Y) prior to insert the reinforcements into the cavity (8).

The method of any of claims 7 to 9, further comprising: - unfolding the reinforcements (1) during their introduction into the cavity (8) by deflecting them with at least one spacer member (16) projecting into the cavity located in the cavity. the area between the opening (9) and the bottom in the longitudinal direction (Y).

A method according to any one of claims 7 to 10, wherein the extended portions (3) of the ends (2) of the reinforcements (1) have a shoulder (3 ') adjacent to the opening (9) of the cavity ( 8) when the reinforcements are introduced.

A method according to any of claims 7 to 11, wherein the expanded portions (3) of the ends (2) of the reinforcements (1) are in a general form of a cylindrical sleeve.