FR2933718A1 - METHOD FOR MAKING A BRIDGE, IN PARTICULAR A MIXED DECK AND FORMWORK SYSTEM SUITABLE FOR IMPLEMENTING SUCH A METHOD - Google Patents

Abstract

Method for producing a composite bridge the slab 3 of which is prefabricated on a formwork area and placed in place by pushing, characterized in that: - for each beam 2 of the bridge, a longitudinal reservation is formed, preferably in the form of a tunnel 10 in the thickness of said slab, so that the slab is supported, on either side of the reservation, on the upper flange 6 of the beam 2; - A link 11 is formed between portions 4,5 of the slab each of a respective side of the beam, so that said connection 11 allows the passage of the connectors during the pushing of the slab; then, - when the slab has taken its final place on the beam, implementation of a concrete seal in the reservation. The tunnel is advantageously boxed using a formwork retractable transversely using hydraulic, pneumatic or mechanical means.

Description

Method for making a bridge, especially a composite bridge and formwork system adapted to the implementation of such a method

The present invention relates to a method for making a bridge, in particular for producing the slab of a composite bridge, particularly when the slab is carried by the upper flanges of metal girders. These beams generally comprise connectors that allow to secure the slab with the beams, so that such a bridge works in mixed beam. The invention also relates to a formwork system for implementing this method. However, the composite bridge slabs of the prior art have very serious problems of structural quality, particularly transverse cracking problems. The transverse cracking is more specifically due to the embodiments of these slabs, in particular to the mechanical actions resulting from the progressive loading of the metal beams, which causes deformations of the already poured slab concrete, and moreover, to the recesses of the concrete at a young age, hampered by the metal beams to which the slab is connected. Removal at a young age, i.e., the first hours after pouring concrete, substantially immediately after setting, is mainly due to heat shrinkage and endogenous shrinkage. The mechanical actions are due to a setting in traction of the concrete slab, in some sections of slab already poured when the beams are deformed under the weight of the added sections. The consequences of these mechanical actions have been reduced, thanks to a first so-called strumming technique, which consists of phasing the realization of the slab by first making sections located in the middle of the span, thus to load the metal beams. , then finish with keying sections, in the most tense areas, at the point of the beam supports. Even if the consequences of such cracking can be reduced by the use of waterproofing screeds on the slabs, they remain detrimental to the durability and longevity of the structure.

Other techniques have further reduced cracking. A second technique is to use prefabricated slabs, then placed side by side on the beams. These slabs include reservations for their sealing on the connectors. This technique nevertheless has disadvantages, in particular the presence of transverse joints between each slab, a discontinuous connection with the framework, at the right of each seal, and a risk of corrosion of the upper face of the sole vis-à-vis the underside of each slab, outside the reservations, duly completed. A third technique, called pushed slabs, consists of prefabricating the slab in successive sections, generally of a length of 5 to 10 meters, on a formwork area, comprising a fixed formwork, then pushing the slab longitudinally on the frame, as and when prefabrication, and finally connect the slab to the frame, only when it has taken its final place. This third technique has the advantage of a delayed connection, thus eliminating the cracking due to the progressive loading of the frame and the annoying withdrawals. However, in this third technique of the prior art, to allow the pushing of the slab, the connectors are generally welded to the frame after pushing, in reservations provided for this purpose and in particularly uncomfortable conditions. This third technique therefore has the disadvantage of a discontinuous connection, associated with the disadvantage of making welds on site, in poor working conditions. A first object of the invention is therefore to provide a method for making a bridge, including a composite bridge, which allows a substantially continuous connection of the slab on the frame and avoids soldering connectors on site. A second object of the invention is to provide a formwork device for making a bridge according to such a method. According to a first object of the invention, such a method for making a bridge comprising a reinforced concrete slab and at least one longitudinal beam provided to support the slab, the beam comprising an upper flange and connectors extending upwardly since the soleplate, comprises steps for: - prefabricating the slab on a formwork area in at least one section; and, - longitudinally pushing a part of already prefabricated slab after completion of each section and before, if necessary, the realization of a section adjacent to said previously pushed slab portion. This method is characterized in that: - for each beam, a longitudinal reservation, open downwards, is formed in the thickness of said slab, so that the slab comes to bear, on both sides of the reservation , on the sole of the beam; - A connection is made and maintained between slab portions each of a respective side of the beam, so that said connection allows the passage of the connectors during the pushing of the slab; then, - when the slab has taken a final place on said beam, implementation of a concrete in said reservation for the sealing of said slab on said beam. Such a method is particularly applicable for the realization of a mixed bridge, that is to say particularly in a case where the at least one longitudinal beam is metallic. The bridge thus manufactured may be a composite bridge and the at least one beam may be a metal beam. In a particular mode of implementation of the method: for each beam, the longitudinal reservation is a longitudinal tunnel formed in the thickness of said slab, so that said tunnel is open downwards and that the slab comes to bear, of on both sides of said tunnel, on said sole of said beam and so that the tunnel forms a vault serving as a reinforced concrete link over said connectors; For each tunnel, at least one well is formed through said vault, between an upper surface of said slab and said tunnel; - After the slab has taken its final place on said beam, implementation of a self-placing concrete through said well in said tunnel for sealing said slab on said beam. In this particular mode of implementation, the slab may comprise several wells distributed along the length of each tunnel. The walls of the tunnel tunnel may advantageously comprise reliefs for longitudinal gripping of the prefabricated concrete of the slab with the sealing concrete. These reliefs may be grooves extending substantially perpendicular to the sole. In this particular embodiment, conventional reinforcing cages for sealing concrete may advantageously be arranged on each beam, prior to pressing, so that said cages do not interfere with said stuffing, and that the connectors extend inside said cages. Thus, these frames can be arranged before pushing the slab, under particularly favorable implementation conditions. Reinforcing concrete reinforcements may be placed in the wells after the slab has taken its final place. According to the second object of the invention, a formwork system for carrying out the method in its particular embodiment is characterized in that it comprises two shoes leaving a space between them, actuating means 25 for the transverse displacement of said shoes between a formwork position, wherein said shoes are spaced from each other and a retracted position, wherein said shoes are close to one another, and a plate bearing longitudinally on each of said shoes, said tray being provided for formwork of a part of the connection above said space, so that in the retracted position, the tray escapes their longitudinal support, and can be deconstructed, vertically downwards; .

Such a formwork system advantageously comprises a fixed shim extending longitudinally and the actuating means advantageously comprise two inflatable tubes arranged longitudinally on either side of the shim, a first pipe being disposed between an inner wall of the shim and a wall of the shoe vis-à-vis the inner wall, the second pipe being disposed between an outer wall of the wedge and a wall of the shoe vis-à-vis the outer wall. Other features and advantages of the invention will emerge from the description below, relating to a non-limiting example.

In the accompanying drawings: FIG. 1 is a schematic transverse section of a double-girder composite bridge according to a preferred first embodiment of a method according to the invention, before sealing the slab on the beams, the half left cut-out illustrating a current half-section of the slab, and the right half-section illustrating a half section of the slab at the location of a concreting well; FIG. 2 illustrates detail II of the left half-section of FIG. 1; FIG. 3 illustrates detail III of the right half-section of FIG. 1; FIG. 4 is a figure similar to FIG. 2, further illustrating the reinforcement; - Figure 5 is a figure similar to Figure 3, further illustrating the reinforcement; FIG. 6 is a diagrammatic detail view illustrating a second embodiment of a method according to the invention; and - Figure 7 is a schematic detail view illustrating a third embodiment of a method according to the invention. - Figure 8 shows two half-sections of a formwork for the implementation of a method according to the invention; the upper half-section illustrating the formwork position and the lower half-section illustrating a retracted position. The examples illustrated in the figures relate to the production of a composite bridge 1 consisting mainly of two metal beams 2 supporting a slab 3 made of reinforced concrete. A method according to the invention provides for the prefabrication of the slab 3, in one or more sections, on a prefabrication area and then pushing the slab, from the prefabrication area to the beams 2, before sealing the slab on the beams. Prefabrication and pushing of the slab are not illustrated in the figures. They can be made by known or new techniques. The figures illustrate the slab in place on the beams 2 after stuffing and before sealing. The slab 3 comprises a central portion 4 formed between the beams and corbels 5 formed on either side of the central portion, beyond the beams. The beams have an I-shaped cross-section, comprising two substantially horizontal flanges 6,7 and interconnected by a substantially vertical core 8. As particularly illustrated in FIG. 1, the slab 3 rests on the upper flanges 6 of the beams 2 In a first step, a first, preferred embodiment of a method according to the invention will be described with reference to FIGS. 1 to 5. In this example, and as particularly illustrated in FIG. bridge 1 is a twin beam that does not have a slope. It is substantially symmetrical about a longitudinal plane P. Figure 1 is a composite illustration. It is formed on the one hand, in its left part, of a current half-section of which a detail II is illustrated in FIG. 2, and on the other hand in its right part, of a singular semi-section of which a detail III is illustrated in FIG. 3. As illustrated in FIGS. 2 and 3, each beam 2 comprises connectors 9 welded to the upper flange 6. The connectors have the form of studs which extend upwards, substantially vertically from the sole 6. They are arranged in several longitudinal rows. In this example, the rows are four in number.

As particularly illustrated in Figure 2, the slab 3 is formed so as to achieve, in the thickness of the slab, a longitudinal tunnel-shaped reservation 10. The tunnel has a substantially trapezoidal cross section. It is open downwards. It is designed to form a vault over the connectors, this vault forming a mechanical link 11, made of reinforced concrete, between the two parts 4,5 of the slab adjacent to the beam. On the other hand, the side walls 12 of the tunnel 10 each bear on a respective edge 14 of the sole 6. As particularly illustrated in FIG. 3, for each tunnel, at least one well 16 is formed through the link 11, from the surface 18 of the slab 3 to the tunnel 10. Preferably, several wells 16 are provided, substantially regularly spaced along each tunnel. These wells are designed to allow sealing concrete to be introduced into the tunnel 10, from the surface 18 of the slab 3. A self-placing sealing concrete is preferably used, which makes it possible to ensure the correct filling of the tunnel 10 between two wells 16 neighbors. It is noted that self-compacting concrete means fluid concretes, homogeneous and stable, implemented without vibration, the compaction of which is carried out solely by the gravitational effect.

Embossments 20 are formed in the lateral faces 12 of the tunnel 10. In the illustrated example, these reliefs are vertical grooves 20. These grooves allow the precast concrete of the slab 3 and the sealing concrete to come into mutual engagement, ensuring thus a reinforced transmission of the longitudinal forces between these two concretes.

FIGS. 4 and 5 illustrate possible arrangements for the reinforcement respectively corresponding to the current and singular zones of FIGS. 2 and 3. In the current zone of the tunnel, common reinforcement cages comprise transverse frames 22 and pins 24, supporting 26. The connectors 9 extend through the common reinforcements. The current zone further comprises two superposed beds of connecting reinforcements 28 extending transversely and horizontally in the thickness of the connection 11, and beyond, in the adjacent parts 4.5 of the slab 3. The reinforcements current 22,24,26 are substantially continuous and pass through each singular zone of a well. The link 11 being interrupted by the well 16, the singular zone does not comprise binding armature. Well frames are constituted by pins 30 so the lower part of the loop is substantially level with the lower part of the frames 22, and whose ends 32 are folded substantially horizontally, close to the surface 34 (shown in phantom ) sealing concrete.

The current reinforcement cages are intended to be put in place on each beam 2 before pushing the prefabricated slab 3. Thus, the transverse dimensions of each tunnel are provided so that the thrust of the slab 3 is not hindered by the current reinforcing cages and a distance is maintained around the reinforcements for their sufficient coating by the sealing concrete. The well frames 30 are put in place after pushing the prefabricated slab 3 to its final place and before implementation of the concrete seal. The embodiment of FIGS. 1 to 5 is particularly advantageous, since it does not generally require temporary reinforcement of the prefabricated slab 3, in particular during its pushing, before its sealing on the beams 2. A second embodiment will now be described. implementation of a method according to the invention, with reference to Figure 6, only in that it differs from the first embodiment. FIG. 6 is similar to FIG. 4, that is to say that it presents a current zone of a prefabricated slab according to the invention resting on the sole plate 6 of a metal beam 2. In the example illustrated in Figure 6, the prefabricated slab 3 is interrupted by a longitudinal reservation 36, traversing the entire thickness of the slab 33.

Thus, a connection 38 between the two parts 4, 5 of the slab 3 is constituted only by transverse reinforcement 28. The lateral walls 12 of the reservation 36 each bear on a respective edge 14 of the sole 6.

As in the previous example, the transverse frames 28 are arranged in two superposed beds. One of the transverse reinforcement beds is disposed near the surface 18 of the slab and the surface 34 of the sealing concrete. The other of the beds is in the vicinity and above the connectors 9, so that the connectors do not interfere with the pushing of the prefabricated slab 3. The upper bed carries upper longitudinal reinforcements 39. Connection frames 40 extend from each part 4.5 of the slab, through the base of the respective side wall, and are folded upwards.

Complementary reinforcements are formed by transverse U's 42 and by a bed of longitudinal reinforcements 44 carried by the base of the U's. The complementary reinforcements 42, 44 are mounted suspended before pushing, so that they do not come into interference with the connectors 9, during pushing. The suspended position of complementary reinforcement is shown in solid lines. When the prefabricated slab 3 is in place on the beams 2, the complementary reinforcements are lowered in a low position, resting on the connection steels 40, so that the connectors extend vertically through meshes formed by the bases of the U and the longitudinal reinforcement 44. The low position of the complementary reinforcement is illustrated in phantom. Once the slab 3 and its reinforcements 42,44 in place, the sealing concrete is implemented in the reservation 36. This sealing concrete can be vibrated since its surface is directly accessible all along the reservation 36. We will now describe a third embodiment of a method according to the invention, with reference to Figure 7, only in that it differs from the first and second modes of implementation. Figure 7 is similar to Figure 4. The third embodiment is very close to the second in that the longitudinal reservation 36 is also a reservation open up and down, completely crossing the thickness of the slab 3.

The embodiment of FIG. 7 is particularly suitable for producing a composite bridge whose thickness of the slab 3 is small relative to the width of the reservation 36. In order for the link 38 to be sufficiently strong, the lower bed transverse steels is replaced by a transverse metal section 46, for example H-shaped section or I. Another metal section 48, whose section is here provided in the form of I, is arranged longitudinally on the sole 6, in the extension of the core 8, so that it forms an intermediate support for the transverse section 46, especially during stuffing. In this example, the U-shaped reinforcements of the complementary steels are replaced by pins 50. These pins are open downwards, so that their descent to their lower position is not hindered by the longitudinal profile 48. sealing is provided on each side 14 between the upper flange 6 and the underside of the slab 6. This seal avoids flows of laitance during the implementation of the concrete seal. With reference to FIG. 8, a formwork device 100 for a tunnel 10 of the type illustrated in FIGS. 1 to 4 will now be described. FIG. 8 represents two superimposed half-cross sections, each schematically representing the left half of the formwork device. 100. In the upper half-section, the system 100 is in its formwork position, that is to say in the position provided during the pouring of concrete slab. In the lower half-section, the system 100 is a retracted position, allowing the slab 3 to be pushed. In its formwork position, the formwork device 100 is symmetrical with respect to a symmetry plane S of the tunnel 10. following only the visible elements on each half-cut. Each of these elements has its symmetrical relative to the plane S.

The system 100 has a substantially identical section for the entire length of the tunnel, including the singular areas, in which specific formwork means are used for the wells. This device is intended to be used on the prefabrication area of the sections of the slab. Typically, for each tunnel, the formwork system is substantially the length of a section of slab to be cast. The system 100 comprises a base 101, substantially flat. In the example shown, the base is substantially horizontal. The base 101 also serves as a formwork base for the underside of the slab, on either side of the tunnel. The device 100 comprises a longitudinal shim 102, a lateral shoe 103 and a plate 104, as well as actuating means 106, 107 for the shoe 103. The shim is of substantially rectangular section. It has two 108,109 longitudinal and vertical faces. A face 108, the closest to the plane S, is said to be internal, the other face 109 being said to be external. The shoe is placed in abutment on the base 101, away from the plane S, that is to say that a space 110 exists transversely between the two shoes of the system. In the formwork position, the plate 104 is in longitudinal support on each of the shoes, so that it allows the formwork on the underside of the link 11, above the space 110. The shoe comprises a top formwork face 112 having a clearance angle A112 for its transverse formwork. The upper formwork face 112 is provided for the formwork on the underside of the link 11, beyond, transversely, the plate 104. Each longitudinal edge of the plate forms a longitudinal support 113, extending downwards beyond the underside 114 of the tray. A counter-support 116 is formed in a corresponding bank, proximal to the plane S, of the shoe 103. This counter-support extends upwards relative to the upper formwork face 112. The support 113 and the counter-support 116 together form a forming strip 118 whose draft angle A118 is greater than the draft angle A112 of the upper formwork face 112. The shoe comprises a distal and substantially vertical formwork face, the farthest relative to the plane S. This formwork side forms against-splines 120, for the formwork of the splines 20 of the slab 3. The depth D120 of the counter-splines corresponds to the depth of the splines 20.

The shoe 103 forms an arch 122 extending longitudinally. The arch forms an arch above the hold 102 and bears on the base 101, on either side of the hold, so that an inner face 124 of the arch is vis-à- screw with the inner face 108 of the wedge 102, and an outer face 126 of the arch is vis-à-vis the outer face 109 of the arch.

The stripping of the tunnel is provided by transverse displacement shoe 103 of a DC value, in the direction of the plane S. During the stripping of the tunnel, the shoe passes from its formwork position to the retracted position, as shown in FIG. 8. The value of the displacement DC is greater than that of the depth D120 against the splines 120, so that during the longitudinal thrust of the slab 3, the grooves 20 and counter-splines 120 do not come into contact. A non-zero clearance J120 is thus provided, equal to the difference between the displacement DC and the depth D120. During the removal of the shoe 103, that is to say during its movement according to DC, the support 113 of the plate 104 escapes the support against the support 116. The counter-support 116 is then vis-à-vis of the underside 114 of the tray. A game J104 appears between this sub-face 114 and the counter-support 116, so that the plate can be removed vertically, the underside 114 bearing against the abutment 116. The actuating means 106,107 are of preferably means for locking which allow the displacement DC of the formwork shoe 103. These means 106,107 are engaged with both the wedge and the shoe. In the illustrated example, these braking means comprise two pipes 106, 107. These pipes are preferably chosen to be flexible, but not substantially elastically deformable. They are advantageously chosen from those used by firefighters. A formwork pipe 106 is disposed longitudinally between the outer face 109 of the shim 102 and the outer face 126 of the arch 122. A formwork pipe 107 is disposed longitudinally between the inner face 108 of the shim 102 and the inner face 124 from the arch 122. The pipes are inflated, that is to say put under pressure with a fluid that can be air or water. The pipes work together like a double acting cylinder. Thus, the pressurizing of the shuttering pipe 106, and the venting of the stripping pipe 107 inflates the shuttering pipe 106. This causes both the separation of the respective external faces 109, 126 of the shim and of the the arch and crushing of the formwork pipe 107 between their inner faces 108,124. Thus, the shoe is brought or held in the formwork position, preferably in abutment, symbolized by the reference 128.

Conversely, the pressurizing of the stripping pipe 107, and the venting of the shuttering pipe 106 causes the stripping pipe 107 to inflate. This causes both the separation of the respective internal faces 108, 124 of the wedge and arch and crushing of the formwork pipe 106 between their outer faces 109,126. Thus, the shoe is brought or maintained in the retracted position. It is then sufficient to ensure that the plate is lowered, to push the prefabricated slab and release the system 100 for the formwork of a possible next section of the slab 3. Of course, the invention is not limited to the example just described and many adjustments can be made to this example without departing from the scope of the invention. In particular, the bridge may have a cant and a curvature. Instead of including two beams, as in the illustrated examples, the bridge may comprise only one beam, or more than two beams. The number of rows of connectors and the spacing of the connectors may vary, in particular as a function of the forces to be transmitted between the slab and the corresponding beam.

Seals may also be provided on the edges of the flanges also for the first and second embodiments. Although less advantageous, the grooves can be replaced by a lost formwork, for example by a metal lattice type Nerlat, the company Metal Expanded.

To form keys for the recovery of longitudinal forces, other forms of formwork may nevertheless be used than the grooves, which allow a mutual engagement, along a longitudinal axis, of the concrete placed in the tunnel with the precast concrete of the slab. 5 15 20 25 30

Claims (10)

REVENDICATIONS1. Method for producing a bridge (1) comprising at least one slab (3) of reinforced concrete and a longitudinal beam (2) intended to support said slab (3), said beam comprising an upper flange (6) and connectors (9) extending upwardly from said sole (6), said method comprising steps for: - prefabricating the slab (3) on a formwork area in at least one section; and, - longitudinally pushing a part of already prefabricated slab after completion of each section and before, if necessary, the realization of a section adjacent to said previously pushed slab portion; characterized in that: - for each beam (2), a longitudinal reservation (10,36), open downwardly, is formed in the thickness of said slab, so that the slab comes to bear, on both sides, another of said reservation, on said sole (6) of said beam (2); a link (11, 38) is made and maintained between portions (4, 5) of the slab (3) each of a respective side of the beam, so that said connection allows the passage of the connectors (9) during pushing the slab (3); then, - when the slab has taken a final place on said beam, implementation of a concrete in said reservation (10,36) for sealing said slab on said beam. 2. Method according to claim 1 characterized in that the bridge is a composite bridge and in that the at least one beam (2) is metallic. 3. Method according to claim 1 or 2, characterized in that: - for each beam, the longitudinal reservation is a longitudinal tunnel (10) formed in the thickness of said slab, so that said tunnel is open downwards and that the slab is supported on both sides of said tunnel on said sole of said beam and so that the tunnel forms a vault (11) serving as a reinforced concrete connection above said connectors; for each tunnel, at least one well (16) is formed through said vault, between an upper surface (18) of said slab and said tunnel; - After the slab has taken its final place on said beam, implementation of self-placing concrete through said well in said tunnel for sealing said slab on said beam. 4. Method according to claim 3, characterized in that the slab comprises several wells distributed over the length of each tunnel. 5. Method according to claim 3 or 4, characterized in that walls (12) of the tunnel comprise reliefs (20) for a longitudinal grip of precast concrete of the slab with the sealing concrete 25 6. Method according to claim 5, characterized in that the reliefs are grooves (20) extending substantially perpendicular to the sole. 7. Method according to one of claims 3 to 6, characterized in that common reinforcing cages (22,24,26) for the sealing concrete are arranged on each beam, prior to pressing, so that That said cages do not interfere with said stuffing, and that the connectors extend inside said cages. 8. Method according to claim 7, characterized in that reinforcements (30) for the sealing concrete are arranged in the wells after the slab has taken its final place. 9. shuttering system (100) for carrying out a method according to claim 3, characterized in that it comprises two shoes (103) leaving between them a space (110), actuating means for moving transversely of said shoes (103) between a formwork position, wherein said shoes (103) are spaced from each other and a retracted position, wherein said shoes (103) are close to one another, and a plate (104) bearing longitudinally on each of said shoes, said plate (104) being provided for the formwork of a portion of the link (11) above said space (110), so that in the retracted position , the tray escapes their longitudinal support, and can be removed, vertically downwards. 10. System according to claim 9, characterized in that it comprises a fixed shim (103) extending longitudinally and in that the actuating means (106,107) comprises two inflatable tubes (106,107) arranged longitudinally on both sides. another of said shim (102), a first pipe (107) being disposed between an inner wall (108) of the shim and a wall of the shoe facing said inner wall (108), the second pipe ( 106) being disposed between an outer wall (109) of the shim and a wall of the shoe opposite said outer wall (109).