AU2004266277A1

AU2004266277A1 - Tie device for arch elements and arch thus obtained

Info

Publication number: AU2004266277A1
Application number: AU2004266277A
Authority: AU
Inventors: Jean-Marc Jailloux; Fahim Ziai
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-08-06
Filing date: 2004-07-26
Publication date: 2005-03-03
Anticipated expiration: 2024-07-26
Also published as: FR2858640B1; WO2005019539A1; ES2312270B1; JP2007501345A; JP4680192B2; FR2858640A1; ES2312270A1

Description

I, Susan Jane Woolley BA DipTST MCIL, of 11 Sterry Drive, Thames Ditton, Surrey KT7 OYN, GB, fully conversant with the French and English languages, hereby declare that to the best of my knowledge and belief the attached is a correct and true translation into English of the text of the International Patent Application no. PCT/FR02/01992 Signed this 3rd day of January 2006 Tie device for arch elements and arch thus obtained The invention relates to a tie device for prefabricated arch elements which are currently used to carry out civil engineering works of the backfilled arch type, e.g. in certain tunnels. It also relates to the arch obtained from prefabricated arch elements and from a tie device according to the invention. A conventional method of realising structures of this type is to place in mutual abutment prefabricated curved arch elements, each forming part of the arch section, so as to obtain a complete section, and then to link the sections thus obtained over the whole length of the structure. To realise the foundations of the arch, throughout the length of the structure two concrete footings are cast in advance, on which the elements of the arch forming the feet of the arch will come to bear. To complete the operation, the structure thus obtained is then backfilled. Generally, only two arch elements placed on the footings are used to form an arch section. This is known as a tri-articulated arch: two articulations between the arch elements and the footings as well as a third between the two arch elements. However, there is another embodiment also in which it is preferred to use three arch elements to form the arch section. Each of the two lateral arch elements is rigidly connected at one of its ends with a footing, whereas its other end receives one of the ends of a central arch element. Each of the mutual abutments between the arch elements forms an articulation. This is known as a bi-articulated arch. In numerous configurations of the structure, loads are applied to one section of the arch which are not balanced due to their asymmetry: there is therefore a resultant load acting on the articulations and harming their stability as well as the strength of the structure. Thus, a resultant horizontal longitudinal load may arise due for example to a variable backfilling thickness over the length of the structure or to a structure formed on a slope. This load may lead to dislocation of the structure. There may also be a vertical resultant load which shears the articulations, sometimes giving rise to cracks or flaking, more particularly in the case of tri articulated arches. Poor ground subject to differential subsidence or an asymmetrical lateral thrust produces such a load. To balance a resultant horizontal longitudinal load, one solution is to carry out longitudinal tying of the arch elements by casting one or two concrete girders over the length of the structure. In the case of a single girder, cast over the entire length of the structure, any rotation of the arch about its longitudinal axis or about its transverse axis is prohibited. Similarly, this solution prevents any vertical displacement. Compared to the previous solution, the casting of two longitudinal girders along the structure has the advantage of permitting rotation about the longitudinal axis. Rotation about a transverse axis and the vertical displacement remain impossible. However, these movements, in particular rotations, must be possible in order that the structure can adapt to the external configuration of the structure (interaction between structure and ground). Moreover, by carrying out tying of the arch elements by casting concrete girders is difficult to implement, e.g. because it is then necessary to set up casings over the entire length of the structure.

3 The object of the invention is in particular to overcome the above-mentioned disadvantages. To this end, the invention proposes a tie device of the type defined below, which comprises at least one tie element formed from a longitudinal core composed of a strong material and of which part of the surface is covered by at least one deformable element made of a ductile material having a high capacity of friction, and being contrived to be inserted longitudinally between the respective lips of at least two arch elements in mutual abutment, and in that the longitudinal core extends over at least the length of one of the lips and comprises means for fixing to the core of at least one adjacent tie element in order to effect tying over the entire length of the arch. The principle of the invention is on the one hand to use the friction present in the articulations to create a load capable of balancing a horizontal longitudinal load and on the other hand to allow at the articulations only the movements which are useful for adapting the structure to the external environment. Furthermore, the tie thus obtained is particularly easy to implement in particular because it does not entail the casting of concrete over the entire length of the structure. The core of the tie element is formed, preferably, from a metal material, in particular steel, so as to provide good rigidity. In one embodiment, the fixing means comprise welding means enabling continuity of tying to be achieved over the entire length of the arch by means of a simple operation. In another embodiment, the fixing means are capable of being joined with fishplates, which forms another simple means of forming strong tying.

4 In a preferred embodiment, the deformable elements comprise two veneers, between which the longitudinal core is inserted. Each of the veneers comes into contact with the lip of an arch element and induces friction between the tie element and the arch elements. The longitudinal core of the tie element is, in an advantageous configuration, a profile having a selected cross-sectional shape, e.g. T-shaped or L-shaped, having one arm part of whose surface is covered with one or more deformable elements and at least one arm projecting to the exterior of the arch in order to facilitate fixing of the longitudinal core to the adjacent core. Furthermore, the deformable elements are connected to the longitudinal core of the tie element, e.g. by adhesion. The deformable elements are preferably formed from a material selected from elastomer materials, e.g. rubber, which are easily deformable, strong and easy to implement. Moreover, the longitudinal core of the tie element comprises at least one centring element capable of engaging in respective seats formed in the lips opposite one another in order to ensure provisional centring of the arch elements. The centring element preferably has substantially the shape of two inverted frustoconi extending respectively on either side of the longitudinal core. Advantageously, the deformable elements only cover part of the surface of the longitudinal core so as to incorporate grooves capable of receiving a slurry of a strong material, e.g. a slurry of cement, in order to consolidate the arch and to ensure fire protection.

5 The invention also proposes an arch composed of arch elements and at least one tie element according to the invention. In a particularly preferred configuration, the arch elements have an upper face which, in the vicinity of the lip, has a recess for housing the arm left free of a T or L-shaped profile. Further features and advantages of the invention will appear from a study of the detailed description given below and from the attached drawings, which show: Figure 1, a general perspective view of an arch section according to the invention, Figure 2, a front view of the arch section in Figure 1, Figure 3, a general plan view of an arch according to the invention, Figure 4, an enlarged view of the detail IV in Figures 2 and 3, Figure 5, a diagram having loads applied at the abutment between the arch elements of Figure 2, Figure 6, an enlarged view of the detail VI in Figure 3, Figure 7, a transverse section through a tie element according to the invention, Figure 8, a transverse section through a tie element according to the invention in another embodiment, Figure 9, a perspective view of fixing means according to the invention, 6 Figure 10, a perspective view of fixing means according to the invention in another embodiment, Figure 11, a perspective view of fixing means according to the invention in another embodiment, Figure 12, a detailed view in transverse section of the abutment between the arch elements according to the invention in another embodiment, Figure 13, a transverse section through a tie element according to the invention in an advantageous configuration, Figure 14, a transverse section through a tie element according to the invention in another advantageous configuration, Figure 15, a perspective view of an arch according to the invention, Figure 16, is a perspective view of a completed arch according to the invention, and Figure 17 is a perspective view of an arch according to the invention in a different configuration from that of Figure 1. The attached drawings may serve not only to supplement the invention but also to contribute to its definition if necessary. The detailed description below considers a civil engineering structure of the backfilled arch type, e.g. a tunnel. An arch section according to the invention (Figures 1, 2 and 3) is conventionally formed by two curved arch elements 1 and 3 prefabricated from concrete, placed in mutual abutment, each resting on the other hand on footings 5 and 7 previously cast in concrete. To form the arch, arch sections are disposed over the entire length of the structure (Figure 3). Once the arch is obtained, the structure is backfilled by means of a backfill R (Figure 16). In the case of an arch according to the invention, a tie element 9 (Figure 4) of length substantially equal to the length of the arch section constituting the tie device according to the invention is inserted between arch elements 1 and 3. It happens in numerous configurations of the structure that the forces applied to one arch section are not balanced. In particular, when the structure is formed on a slope or when the thickness of the backfill R varies over the length of the structure, a longitudinal horizontal load Fm (Figure 5) is generated at the abutment between the arch elements. If this load Fm is not compensated, it will not be possible to achieved static equilibrium of the arch section. In some cases, this imbalance leads to dislocation of the structure. To ensure stability and strength of the structure, it is therefore necessary to balance the arch section by creating at the abutment between the arch elements 1 and 3 a longitudinal horizontal force Fr opposite to Fm and of greater intensity. The invention consists in using the horizontal transverse loads N, due in particular to the thrust of the backfill R on the arch, by creating friction in the abutment between the arch elements 1 and 3. The friction associated with the transverse loads N generates a longitudinal horizontal force Fr capable of balancing Fm. A first function of the tie element 9 according to the invention is therefore to create friction at the abutment between the arch elements 1 and 3. In order to be adapted to the external environment, the arch section must be able to deform within reasonable limits. At the abutment between an arch element 1 and a footing 5 (Figure 6), chamfers 61 and a clearance e formed between the edge of the footing 5 and the arch element 1 permit certain movements, in particular rotation about the longitudinal axis. The link between the footing 5 and the element 1 is thus known as an articulation. In order to prevent a vertical load in the section of the arch due in particular to different backfilling on either side of the structure or to a different ground composition under the footings 5 and 7, it is also necessary to allow at the abutment between the arch elements 1 and 3 certain displacements, in particular rotation about a transverse axis and vertical translation of one arch element 1 relative to the other 3. In this case, an articulation is also involved between the arch elements 1 and 3. The tie element 9 of the tie device according to the invention must therefore permit the abovementioned displacements. The whole of these degrees of freedom makes it possible to impart to the structure a curved alignment, both in the vertical plane and in the horizontal plane. A first embodiment (Figure 7) of the tie element 9 of the tie device according to the invention comprises a metal core 75 formed by means of a profile having a general inverted L shape. On the two faces of the larger arm of the metal core 75 are disposed or adhered two deformable veneers 71 and 73, the other arm being left free. A second embodiment (Figure 8) provides that the metal core 77 may be formed by means of a profile having a general T shape. Once the tie element 9 is inserted between the arch elements 1 and 3, the respective faces of the arch elements 1 and 3, the lips 41 and 43, are in contact with the deformable veneers 71 and 73. This contact in fact creates the friction being sought. In parallel, the veneers 71 and 73 permit rotation about a transverse axis and vertical translation since they are deformable. For optimum functioning of the tie device according to the invention, it is advantageous to make the deformable veneers 71 and 73 from a material having both good deformability and having an adapted coefficient of friction with concrete. Thus preferably a material of the elastomer type such as rubber or neoprene is used. In order the ensure stability and strength of the arch in its entirety, it is necessary to tie the tie elements 9 so as to balance the resultant horizontal 9 longitudinal loads over the entirety of the arch. To this end, it is necessary to fix the core 75 of the tie element 9 to the core of an adjacent tie element. A first configuration (Figures 9 and 10) uses metal fishplates 90 to connect the metal cores 75. A metal plate 91 is disposed astride the upper faces of the two metal cores 75. The metal plate 91 is either screwed to each of the metal cores 75 by means of screws 93 (Figure 9) or is welded (Figure 10) by means of weld seams 94. It is also possible in a second configuration (Figure 11) to form a weld seam 100 directly between the upper faces of two metal cores 77. In order to facilitate the positioning of the tie element 9 on the faces of the arch elements 1 and 3, there may be provided on the tie element 9 a centring device 110 (Figure 12). Two centring elements 113 and 115 of frustoconical form fit together at their bases on either side of the metal core 75, in this case provided with a suitable perforation by means of a male/female device not shown. Centring recesses 111, whose shape is complementary to that of the centring elements 113 and 115, are formed in the lips 41 and 43 of the arch elements 1 and 3. The centring device 110 is optionally formed to be not very rigid. On the one hand its centring function is temporary, and on the other hand the centring device 110 must not prevent movements at the articulation between the arch elements 1 and 3. Although the movements at the articulation between the arch elements 1 and 3 must be allowed in order to permit the arch to adapt to the external environment (ground/structure interaction), it is advantageous once this adaptation is ensured to consolidate the arch in order to make it stronger in particular against fires. To this end, an improvement of the tie element 9 according to the invention provides to form cavities 150, 160 in which it is possible to inject a slurry of a suitable material, e.g. with a cement base (Figures 13 and 14).

10 Once the arch is in place (Figure 15), by placing the arch elements opposite one another by inserting the tie element 9 and all the tie elements 9 connected by welding or by means of fishplates, it is advantageous to ensure the sealing tightness of the arch before backfilling the same. To this end, conventionally a sealing foil (181) is placed over the entire upper surface of the arch (Figure 16) or at least over the joints. It is therefore necessary that the tie elements 9 do not exceed the upper face of the arch. Thus (Figure 12) a recess 117 is formed on the upper face of the arch elements 1 and 3 close to the lips 41 and 43. The tie device according to the invention has been described above in the case of tri-articulated arches. It is transposable as such to the case of bi-articulated arches. In the same way, a configuration has been described in which the arch elements 1 and 3 are disposed opposite one another. In the case (Figure 17) where the arch elements 1 and 3 are disposed in a staggered manner, i.e. each arch element 1 is in abutment with two others 3 and 11, the tie device according to the invention may also be used. Finally, longitudinal cores have been described above which are formed by means of profiles of general inverted L or T shape, but it is conceivable to use other shapes, in particular a profile of circular section. In this case, an elastomer sheath, which is cylindrical or flange-shaped, surrounds the cylindrical core over only part of its length. This configuration therefore makes it necessary to provide the lips of the arch elements with semi-cylindrical recesses over their entire length. The invention is not limited to the embodiments described above given purely by way of example, but includes all the modifications which the person skilled in the art may conceive within the scope of the claims below.

Claims

1. Tie device for arch elements, the arch elements being connected together so as to form an arch, characterised in that it comprises at least one tie element (9) formed from a longitudinal core (75,77) composed of a strong material and of which part of the surface is covered by at least one deformable element (71, 73) made of a ductile material having a high capacity of friction, and contrived to be inserted longitudinally between the respective lips (41, 43) of at least two arch elements (1, 3) in mutual abutment, and in that the longitudinal core (75, 77) extends over at least the length of one of the lips and comprises means (90, 100) for fixing to the core of at least one adjacent tie element in order to effect tying over the entire length of the arch.

2. Device according to one of the preceding claims, characterised in that the core of the tie element (9) is formed from a metal material, in particular steel.

3. Device according to claim 2, characterised in that the fixing means comprise welding means (100).

4. Device according to either of claims 1 or 2, characterised in that the fixing means comprise fishplates (90).

5. Device according to one of the preceding claims, characterised in that the deformable elements comprise two veneers (71, 73) between which the longitudinal core (75, 77) is inserted.

6. Device according to one of the preceding claims, characterised in that the longitudinal core (75, 77) of the tie element (9) is a profile having a cross section of selected shape, e.g. T- or L-shaped, having one arm part of the surface of which is covered by one or plural deformable elements and at least one arm projecting towards the exterior of the arch. 12

7. Device according to one of the preceding claims, characterised in that the deformable elements (71, 73) are connected to the longitudinal core (75, 77) of the tie element, e.g. by adhesion.

8. Device according to one of the preceding claims, characterised in that the deformable elements (71, 73) are formed from a material selected from the elastomer materials, e.g. rubber.

9. Device according to one of the preceding claims, characterised in that the longitudinal core (75, 77) of the tie element (9) comprises at least one centring element (110) capable of engaging in respective recesses (111) formed in the lips (41, 43) opposite one another in order to ensure provisional centring of the arch elements.

10. Device according to claim 9, characterised in that the centring element (110) substantially has the shape of two inverted frustoconi (113, 115) extending respectively on either side of the longitudinal core.

11. Device according to one of the preceding claims, characterised in that the deformable elements (71, 73) only cover part of the surface of the longitudinal core (75, 77) so as to house seats (150, 160) capable of receiving a slurry of a strong material, e.g. a cement slurry.

12. Arch composed of arch elements (1, 3) and of at least one tie device according to one of the preceding claims.

13. Arch according to claim 12 in combination with claim 6, characterised in that the arch elements (1, 3) have an upper face (119) which in the vicinity of the lip (41, 43) has a recess (117).