EP0089861B1 - Method of reinforcing arches or similar constructions - Google Patents

Abstract

1. Process for strengthening an arch (1) comprising the operations consisting in prefabricating a relatively thin vault (2), for example of reinforced concrete, with a profile adapted to that of the arch (1) to be strengthened, in placing it under the intrados of the arch (1), in supporting it therein temporarily or permanently, and in then inserting between the extrados of the prefabricated vault (2) and the intrados of the arch, a suitable filling (5), temporary or permanent, suitable for transmitting the forces of the arch (1) to the prefabricated vault (2), characterized in that the filling (5) inserted between the vault (2) and the arch (1) contains means specially intended to facilitate the relative movements of the vault and of the arch in a direction tangential thereto.

Description

The present invention relates to a method for reinforcing an arch, this term designating a bridge arch, an arch, a vault or the like.

The problem arises of consolidating one or more constructions such as the arches of a bridge, whether they are made of masonry, concrete, or other materials, especially when these constructions are in poor condition; it can then be just as much a permanent reinforcement as a temporary reinforcement, limited to the duration of the restoration work. The same problem arises when one wants, for example, to increase, permanently or temporarily, the carrying capacity of a structure such as a bridge.

Various methods are already known for consolidating structures of the indicated type. They are notably described in: "Annals of the Technical Institute of Building and Public Works", No 373 - June 1979 - pages 14 to 16 and No 411 - January 1983 - page 72. These processes generally use metallic structures, which are expensive, and the installation of which is also costly and time-consuming, which leads to a long-term disruption of normal use of the structure. Such metallic comfort structures, necessarily visible, generally have a deplorable aesthetic effect on the work or construction to which they are applied, and they require at least some monitoring, and possibly some maintenance, even if only discounts periodicals in painting. Finally, such structures have the drawback of necessarily obstructing part of each arch to be reinforced, the free height of which, in particular, is necessarily reduced.

In DE-C-555 819, a method has been proposed for reinforcing the watertightness of a pre-existing bridge vault or the like, according to which a cost of reinforced concrete is poured between a lower formwork and a sealing layer applied against the pre-existing arch. Such a process seems difficult to apply to very long vaults and supporting heavy loads.

Document FR-A-2 126661 describes a process for making a lining of the tunnel consisting of prefabricating a relatively thin vault, of profile adapted to that of the arch formed by the roof and the sides of the tunnel, in placing this vault under the 'intrados of this arch, to maintain it there, then to insert between the extrados of the prefabricated vault and the intrados, an appropriate filling to transmit the forces of the walls of the tunnel to the prefabricated vault.

The method of this document has the disadvantage that the filling, being rigid, transmits to the prefabricated vault not only radial forces, that is to say perpendicular to the vault, but also transverse forces, which requires giving to this arch an appreciable thickness.

The process of the present invention is of the same type as that which has just been indicated, but it is characterized in that the filling inserted between the vault and the arch contains means specially intended to facilitate the relative displacements of the vault and the arch in a direction tangential to it.

This absence of solidarity between the arch and the vault offers the following advantages: it allows temporary reinforcement of the arch, the vault used for this purpose being able to be recovered without difficulty when the reinforcement is no longer necessary, and said arch can then be reused for other comforting operations; on the other hand, the absence of solidarity allows relative movements of the arch and the vault; they can be small tangential movements of various origins, for example due to differences in thermal expansion or to overloads; but it can also be radial movements, the vault being in particular more or less close to the fixed arch, for example by means of jacks placed at the foot of the vault, to allow the vault to collect a fraction more or less significant of the total load of the arch.

According to an advantageous method, the filling inserted between the vault and the arch is formed at least in part by a laminated material in the radial direction, and comprising at least one layer of epoxy resin adhering to the vault or to the arch, thus that one or more smooth films of a flexible synthetic material.

According to another advantageous method, which can be combined with the previous one, the filling inserted between the vault and the arch is formed at least in part by a laminated material in the radial direction, and comprising at least one layer of epoxy resin, adhering arch or arch, as well as one or more smooth films of a flexible synthetic material, for example one or more thin sheets of polyethylene, possibly separated from each other and from the resin layer, by layers lubricant, or a more or less viscous substance.

The reinforcement method according to the present invention is applicable for example to the demolition and / or reconstruction of at least one arch, an arcade, an arch or a similar construction; in this application, the vault placed under the lower surface of the arch serves as protective decking during the demolition of the arch and possibly as formwork or support during its reconstruction.

By way of examples, several embodiments of the invention have been described below and illustrated diagrammatically in the appended drawing.

Figure 1 schematically illustrates the reinforcement of a bridge arch by the method according to the present invention. Figure 2 is a view, at the end and in partial section, of a part of a formwork for the prefabrication of a reinforced concrete vault, intended for the implementation of the reinforcement method according to the present invention. Figure 3 shows on a larger scale the detail III of Figure 2. Figure 4 is a perspective view, partially broken away, of the reinforced concrete vault of Figure 2, its upper surface being covered by a laminated material, surmounted by a layer of injection grout. Figure 5 is a section along line VV of Figure 4. Figure 6 is a diagram illustrating different methods of positioning the reinforced concrete vault below an arch to be reinforced. Figure 7 is a partial view showing, at the end, the reinforced concrete vault in the position of reinforcement of the arch. FIG. 8 is a partial view along arrow VIII of FIG. 7. FIG. 9 shows the detail IX of FIG. 7 on a larger scale.

FIG. 1 schematically illustrates the reinforcement of an arch 1, for example of one of the arches of a masonry or reinforced concrete bridge, by the method according to the present invention: this reinforcement is provided by a vault 2, relatively thin, reinforced concrete in the embodiment considered; this vault 2 has a profile adapted to that of the arch to be reinforced, 1, under the lower surface of which it is placed and maintained by means of which two different embodiments have been illustrated respectively on the right and on the other side of the arch 1; on the right, the foot of the arch 2 rests, for example by means of jacks or wedges, which will be described later in detail, on a die, 3, made of concrete or steel, fixed, by any means, to the corresponding pile of the arch 1, at an appropriate height above its foundation 4. In the embodiment illustrated on the left, the die 3a is not fixed to the corresponding pile of the arch 1, but rests on its foundation 4a, or a special foundation, by means of a support of appropriate height, 3b, in which, moreover, the die 3a can be integrated, in particular if the die 3 and its support 3b are formed by a single piece of reinforced concrete. The height of the die 3 or of the support 3b above the foundation 4 or 4a is chosen so that there remains, between the lower surface of the arch 1 and the upper surface of the arch 2, an annular interval 5, whose radial width is very small compared to the diameter of the arch. It is in this interval that an appropriate filling, an embodiment of which will be described later, will be inserted so as to eliminate any void between the arch 1 and the arch 2, and thus allow the transmission of radial forces from the first to the second.

The first phase of the implementation of the reinforcement method according to the present invention is therefore the prefabrication of a profile vault adapted to that of the arch to be reinforced; in the case of a reinforced concrete vault, this prefabrication can be carried out for example using the adjustable formwork which is illustrated diagrammatically in FIGS. 2 and 3.

This formwork according to the present invention comprises a base frame 6, which rests on the ground by means of adjustable height members 7, for example jacks, sand boxes, wedges, keys or the like. The formwork further comprises sets, parallel and transverse, of sand pits; the end view of FIG. 2 shows some of the sand pits, 8a to 8e, of the first transverse assembly closest to the illustrated end of the formwork, which comprises other similar assemblies, situated in transverse planes, parallel to that of Figure 2. The sand pits of each transverse assembly are hinged one after the other, as visible, in the detail view of Figure 3, for the sand pits 8c and 8d, the ends of which are joined by means of a yoke 9. Each transverse set of sand pits, such as that shown partially in FIG. 2, is supported at its articulations such as 9, by radial props, such as 10, and vertical props, such as 11, of which at least some are of adjustable length, and which all bear on the base frame 6; horizontal stays 12, which can also be of adjustable length, can also be provided to join together the stays 10 and 11. All the stays of adjustable length are constituted for example by screw jacks. The detail view of FIG. 3 further shows that the neighboring sand pits, for example 8c and 8d, are articulated by ball joints 13, which rest on the bottom, 10a, of the fork of the screw jack, constituting the adjustable end of the corresponding radial forestay 10. The sand pits, which can be made of wood or metal, on the other hand support pieces of wood, or pieces, such as 14a to 14e (FIG. 2), each having a flat face, applied on the corresponding sand pit, and an opposite face, curved appropriately. On the sets of valleys such as 14a to 14e rest longitudinal joists such as 15, themselves supporting a formwork skin, made of wood, metal, plastic ... etc., designated by 16. At an appropriate distance of this internal formwork, and in particular of its skin 16, is supported, by means not shown, an external formwork, which can be limited so as to cover only the parts of said internal formwork, the most inclined on the horizontal, as visible on the right-hand part of FIG. 2. The external formwork element which is represented therein also comprises a formwork skin 17, longitudinal joists 18, and transverse elements 19.

The adaptation of the interior formwork which has just been described, and in particular of its formwork skin 16, to the profile of the arch to be reinforced, results in particular from the adjustment of the lengths of the various props, such as 10, 11 and possibly 12, as well as the choice of dimensions and shape, in particular of the curvature of the external surface of the valleys, such as 14a to 14e. After solidification of the concrete poured on the internal formwork and in the annular interval between the latter and its parts covered by the external partial formwork, the reinforced concrete vault, 2, rests by its feet, such as 2a, on a support 21. To carry out the decoupling, it then suffices to lower the base frame 6 by reducing the height of the members 7, for example jacks, so that the arch 2 no longer rests on its supports such as 21; these can be provided for example with rolling members making it possible to transfer the arch 2 from its molding position to the foot of the structure to be reinforced, or at least to its place of loading on an appropriate means of transport to transport it to the foot of the structure.

Before, and preferably after transporting the prefabricated vault at the foot of the structure to be reinforced, a laminated material is applied to the upper surface of said vault, an embodiment of which will be described using FIGS. 4 and 5. Before the deposition of this laminated material, the upper surface of the prefabricated vault is prepared by cleaning it by brushing and / or sanding, then it is applied directly to the upper surface, for example by spraying with a spray gun, or by coating with a brush. , a layer of epoxy resin, 22, having a very low surface friction coefficient, and an average thickness of the order of 0.30 mm; to constitute this layer, one can use for example the material UTAREP 105 (mark registered by Laboratoires UETTWILLER).

Over the layer of epoxy resin, 22, a very thin layer 23 is then deposited, for example of a mineral, vegetable or synthetic grease, or of an equivalent substance, more or less viscous.

Above the layer of grease 23, a polyethylene sheet 24 is finally deposited, having for example a thickness of 0.45 mm, like that which is sold under the name "BTP" by PO-LYANE ISOCHANTIER. It is essential that this polyethylene sheet is impermeable in the radial direction for the injection grout which will be mentioned later, and this over the entire surface of the upper surface of the vault 2; consequently, in the case of a large vault, this sheet may be formed by several juxtaposed strips, the edges of which are welded or glued together so as to provide impermeability for the injection grout. In the embodiment considered, a second layer of grease, 25, for example identical to the layer 23 previously described, is deposited over the polyethylene sheet 24. Of course, the laminated material which has just been described could have several polyethylene sheets such as 24, separated by an appropriate number of grease layers such as 23 and 25. These are also optional.

The prefabricated vault, the upper surface of which was covered with the laminated material previously described, can then be put in place by one of the following two methods, which will be described with the aid of FIG. 6.

1. The dice 3 are first of all implemented by one of the two techniques illustrated in FIG. 1 and previously indicated (in FIG. 6, it has been assumed that they are fixed directly to the corresponding stack of the bridge, as on the right side of figure 1). With suitable lifting gear, which can rest on the ground and / or possibly on the structure itself, if its strength is sufficient, lift the vertical vault, according to arrow F1, the prefabricated vault with the upper surface covered by the laminated material described above, until its two feet, such as 2a, are located substantially at the level of the upper faces of the two corresponding dice, 3. With the aid of the lifting devices previously mentioned, we then communicate to the arch 2 a horizontal translational movement, along arrow F2, which brings it below the arch 1 to be reinforced, in the position illustrated in front view in FIG. 1.

2. As a variant, the prefabricated vault 2, covered by the laminated material, is deposited at the foot of the structure on a rolling track 26, extending as far as below the arch to be reinforced 1; before the implementation of the dice such as 3, the arch 2 is moved horizontally by rolling or sliding on the track 26, along the arrow F3, so as to be brought below the arch 1; it is then lifted to the level of the arch 1 by appropriate lifting devices, along arrow F4, and maintained at the correct height by said devices during the laying of the dice, 3, intended to support it.

Before the installation of the prefabricated vault, it is possibly possible to prepare the lower surface of the arch 1, in particular by cleaning it by brushing and / or sanding, and possibly by picketing it, to promote the attachment of the grout d injection, the installation of which will now be described.

FIGS. 7 and 8 show on a larger scale the method of fixing a die 3, of the type represented on the right of FIG. 1. It can be seen in particular that the die, 3, is fixed to the corresponding pile of the arch 1 by prestressing bars 27, each having one end passing through or sealed in the corresponding pile of the arch 1, while its other end passes through a hole in the die 3 and has a thread on the unobstructed face thereof, onto which a nut such as 28 can be screwed, possibly with the interposition of a clamping plate (not shown). The prestressing bars 27 could also be replaced by prestressing cables. The opposite faces of the die, 3, and of the corresponding foot, 2a, of the arch 2 are reinforced by steel plates 29 and 30, intended to ensure a good distribution of the forces. Each plate such as 29 can in particular facilitate the rolling or sliding of the prefabricated vault 2 on track 26 (FIG. 6). In the embodiment illustrated on a large scale in FIGS. 7 and 8, the dice such as 3 are fixed to the arch 1 in positions such that there remains, between the steel plates 29 and 30, an interval in which are arranged vertical actuators, 31, the role of which will be explained later; the number and arrangement of said jacks along each of the dice such that 3 are chosen to ensure the stability of the arch 2. As already indicated, a narrow annular interval, 5, then remains between the lower surface of the arch 1 and upper surface of the roof 2, covered by the laminated material; during manufacture, pipes, generally metallic, such as 32, were embedded for example in the feet 2a of the vault 2, so as to open into the annular interval 5. The radial width of the latter is then adjusted to a predetermined value by the action of the jacks 31 and one then proceeds to the caulking of the ends of the annular gap 5, on the front faces of the arch 1 and of the arch 2, which are respectively in the same plans; this caulking can be achieved by any suitable means, for example by means of planks and / or cement mortar. One then proceeds to the injection of a solidifiable grout through the tubes such as 32; this grout, which can be of the STUP or LSPI type, fills the annular gap 5, made watertight by the caulking. The injection pressure has a value chosen so that, after solidification of the grout, the vault 2 optionally collects at least part of the load of the arch 1. It is understood that the layer of solidified grout (which has been designated by 33 in Figures 4 and 5) fills all the inequalities of the lower surface of the arch to be reinforced and ensures its continuity with the upper surface of the arch 2, or at least with the outermost layer, 25, of the laminated material , which covers it. Finally, the arch 2 is clamped against the arch 1 by the action of the jacks 31, bearing on the dice 3, so as to ensure good transmission of the loads from the arch 1 to the arch 2, via of the filling constituted by the superposition of the laminated material 22 to 25 and of the layer 33 of solidified grout.

The loads, generally variable over time, which are applied to the arch 1, reinforced by the arch 2, can however produce a certain reduction in the clamping pressure of the arch against the arch. This clamping pressure can be restored to its initial value by actuating the jacks 31 and / or by reinjecting, under a determined pressure, solidifiable grout, via the pipes 32.

For certain applications, it is possible to interpose between the jacks 31 (FIG. 8) shims such as 34, made of concrete, wood or steel. In this case, after reducing the height of the jacks 31, so that the arch 2 is no longer supported except by the shims such as 34, it is possible to recover the jacks 31 for other uses. In this case, the possible restoration of the clamping pressure requires either the replacement of the jacks 31, or the reinjection of solidifiable grout.

The process of reinforcing a bridge arch, which has just been described, offers the important advantage of allowing the eventual removal of the reinforcement arch, in particular in the case where the feet, such as 2a, of the arch 2 rest on jacks, such as 31; after removal of the shims such as 34, it suffices to reduce the height of the jacks 31 so that the arch descends slightly below the arch 1; the separation is generally carried out at the level of the grease layer 25 (FIGS. 4 and 5), the solidifiable grout layer remaining adherent to the lower surface of the arch 1, while the laminated material, or at least its layers 22 to 24, follow the downward movement of the roof 2; the latter can obviously be reused to reinforce another arch of the same dimensions, thanks to the repetition of the positioning operations described above.

The present invention is not limited to the embodiments previously described. It encompasses all their variants. The reinforcement method according to the present invention is particularly advantageous when it is necessary to demolish and / or reconstruct at least one arch of a structure such as a bridge; in this case, in fact, the vault placed under the lower surface of the arch can serve as protective decking during the demolition of the arch, which avoids any interruption in service, in particular of circulation below the arch during the demolition operation. In the case of the reconstruction of the arch, in particular by concreting, the prefabricated vault can serve as formwork, or even as a support, in particular for a formwork. The method according to the present invention is applicable to reinforce vaults of any shape, such as for example domes or similar constructions. The filling inserted between the upper surface of the prefabricated vault and the lower surface of the arch to be reinforced can be carried out in such a way that the laminated material (22 to 25 in Figures 4 and 5) is applied to the lower surface of the arch to be reinforced, while the grout is injected between this laminated material and the upper surface of the prefabricated vault. Of course, the prefabricated vault can be made lighter by interior voids; to consolidate a very deep arch, several prefabricated vaults can be used, juxtaposed one after the other.

The detail view of FIG. 9 shows that the sealing of the injection space, 5, of the solidifiable grout can be notably improved by providing layers of an appropriate adhesive, on the one hand (layer 35), between the collar 32a of each grout injection pipe, 32, and the polyethylene sheet 24, and, on the other hand (layer 36), between each lower edge, 24a, of said sheet 24, and the corresponding foot of the arch 2 or the edge of the steel plate 29.

Claims (11)

1. Process for strengthening an arch (1) comprising the operations consisting in prefabricating a relatively thin vault (2), for example of reinforced concrete, with a profile adapted to that of the arch (1) to be strengthened, in placing it under the intrados of the arch (1), in supporting it therein temporarily or permanently, and in then inserting between the extrados of the prefabricated vault (2) and the intrados of the arch, a suitable filling (5), temporary or permanent, suitable for transmitting the forces of the arch (1) to the prefabricated vault (2), characterized in that the filling (5) inserted between the vault (2) and the arch (1) contains means specially intended to facilitate the relative movements of the vault and of the arch in a direction tangential thereto.

2. Process according to Claim 1, characterized in that the filling (5) inserted between the vault (2) and the arch (1) consists at least partially of solidifiable injection grout (33).

3. Process according to either of Claims 1 and 2, characterized in that the filling (5) inserted between the vault (2) and the arch (1) consists at least partially of a material laminated in the radial direction, and comprising of at least one layer of epoxide resin (22) adhering to the vault (2) or to the arch (1), as well as one or more smooth films of a flexible synthetic material.

4. Process according to Claim 3, characterized in that the material of which the said film (or films) (24) consist is polyethylene.

5. Process according to Claim 4, characterized in that the said polyethylene films (24) are separated from each other and from the layer of resin (22) by layers of lubricant (23, 25) or of a more or less viscous substance.

6. Process according to one of Claims 1 to 6, characterized in that solidifiable grout (33) is injected between, on the one hand, a laminated material (22-25), applied to the extrados of the vault (2) and, on the other hand, the intrados of the arch (1), the laminated material (22-25) being made impervious to this grout beforehand by virtue of a sheet (24) of synthetic material, in a single piece or made up by welding or adhesive bonding of a number of adjoining widths.

7. Process according to any one of Claims 1 to 6, characterized in that, after the installation of the filling (5) and, if desired, of the injection grout (33), the vault (2) is clamped against the arch (1), by the action of jacks (31) bearing, for example, on the supports (3, 3a) of the said vault (2), so that the vault takes up at least a part of the load of the arch, the said jacks (31) making it possible to adjust subsequently the bearing pressure of the arch (1) on the vault (2), or else being subsequently replaced with fitted wedges (34).

8. Process according to either of Claims 6 and 7, characterized in that, while the vault (2) is supported under the intrados of the arch (1) by means of suitable supports (3, 3a) the solidifiable grout (33) is injected under a suitable pressure so that, after solidification of the grout (33), the latter provides a perfect distribution of the forces of the arch (1) on the vault (2).

9. Process according to Claim 8, characterized in that the means for injecting (32) the grout are left in place to make it possible to restore or to increase subsequently the bearing pressure of the arch (1) on the vault (2), by reinjecting grout.

10. Application of the process according to one of Claims 1 to 9 to the demolition and/or the reconstruction of an arch, the vault (2) placed under the intrados of the arch (1) being used as a protective flooring during the demolition of the arch and, if desired, as coffering or as a support during its reconstruction.

11. Coffering for the prefabrication of reinforced concrete arches comprising a base frame (6) resting on the ground through the intermediacy of members (7) of adjustable height for centre striking, parallel and transverse sets of stringers (8a-8e) articulated abutting each other and supported, in the region of their articulations (9), by props (10, 11, 12) of adjustable length, bearing on the base frame (6), an internal coffering made up essentially of lengthwise joists (15) supported by the transverse sets of stringers (8a ... 8e) through the intermediacy of components (14a ... 14e) profiled so that the said internal coffering is adapted for a suitable adjustment of the lengths of the props (10, 11, 12) to the intrados of the vault (2) to be prefabricated, as well as an external coffering (19), supported at a suitable distance above the parts of the internal coffering, which are the most inclined to the horizontal, characterized in that it contains means especially intended to facilitate relative movements of the coffering and of the arch in a direction tangential to these.

Images