WO2001014645A1

WO2001014645A1 - Method for constructing a cable-stayed bridge

Info

Publication number: WO2001014645A1
Application number: PCT/FR2000/002350
Authority: WO
Inventors: Michael Robert Mcclenahan; Jérôme Stubler
Original assignee: Freyssinet International (Stup)
Priority date: 1999-08-24
Filing date: 2000-08-21
Publication date: 2001-03-01
Also published as: JP2003507605A; KR20010080281A; KR100732243B1; AU7015100A; PT1125027E; DE60010846D1; JP4436585B2; FR2797893A1; ES2220526T3; EP1125027A1; FR2797893B1; ATE267299T1; EP1125027B1

Abstract

The invention concerns a method for constructing a cable-stayed bridge comprising a floor slab (6), at least a tower (4), and inclined stay cables (7) mounted between the tower and the floor slab. The invention is characterised in that after the tower (4) has been erected, the method consists in fixing at least a support cable (10, 14) to said tower, linking the support cable (10, 14) to a section (6a, 6b) of the floor slab, and thrusting said apron section from one end (2, 3) of the bridge, the support cable (10, 14) providing support for the floor slab section (6a, 6b) while it is being thrust.

Description

CONSTRUCTION METHOD OF A SHAFT BRIDGE

The invention relates to a method of constructing a cable-stayed bridge of the type comprising an apron, at least one pylon, and inclined stay cables mounted between the pylon and the apron.

Among these construction methods, the invention relates more particularly to a method of constructing a cable-stayed bridge by pushing its deck.

Pushing techniques are well known in the field of bridge building. Successive sections of the deck are built or assembled in riparian workshops, from which the deck is pushed as it is built.

In general, the deck rests, during its progression, on the piers of the bridge previously built. A lighter bow attached to the front of the apron prevents it from tipping over at the start of the push, and avoids too much mass overhanging between the stacks. In the case where a relatively long interval must be crossed between two stacks, the front spout is no longer sufficient against such overhangs.

Document FR-A-2 693 492 discloses a method of constructing a cable-stayed bridge by pushing its deck. According to this document, the upper portion of a pylon is erected on the deck and the shrouds are put in place before the push. It is this guyed assembly which is pushed on previously constructed piles, to a position where the upper portion of the pylon is above a pile, which completes the erection of the pylon.

This process seems to be a very delicate implementation. It is unsuitable in the case of relatively massive structures, and in the case where the guyed portions of the bridge cross relatively long distances between the supports on the ground.

The object of the present invention is in particular to facilitate the construction of cable-stayed bridges when the cable-stayed portion must cross a fairly long distance.

For this purpose, the cable-stayed bridge construction method according to the invention is characterized in that after having erected the pylon, at least one support cable is attached to this pylon, the support cable is connected to a section of the deck , and said deck section is pushed from one end of the bridge, the support cable helping to support the deck section during the push. In preferred embodiments of this invention, one and / or the other of the following arrangements are also used:

the support cable is connected to the deck section by means of at least one support to which the support cable is fixed on the one hand and at least one retaining cable anchored towards said end of the bridge, the deck section being arranged to slide relative to the support during the pushing while the support is substantially static; - A longitudinal rail is fixed to the deck having at least one side intended to come to bear slidingly on rollers mounted on the support;

- as the deck section is pushed, static supports are put in place at a front end of the deck section, by connecting them to the pylon by support cables and to a fixed anchor by restraint cables; the support cable retains the section of the deck at a fixed point relative to the section of the deck, the length of this support cable between said fixed point and its point of attachment to the pylon, being made variable by means of adjustment;

- The adjustment means comprise a jack articulated at a front end of the deck which is oriented opposite to said end of the bridge;

- The adjustment means comprise a jack which is fixed to the ground on the side of said end of the bridge so that the support cable goes around from below the front end of the section of deck;

- during the preparation of the pylon, anchoring zones are provided in the pylon for anchoring the shrouds, and the support cable is attached to the pylon in one of these zones.

Other characteristics and advantages of the invention will appear during the following description of three of its embodiments, given by way of nonlimiting example, with reference to the accompanying drawings. In the drawings:

- Figure 1 is a general schematic view of a cable-stayed bridge shown during the pushing step of a first section of its deck according to a first embodiment of the method of the invention, and during the step of pushing a second section of its deck according to a second embodiment of the invention,

FIG. 2 is a general schematic view of the cable-stayed bridge in FIG. 1, once the final installation of its deck sections has been completed, FIG. 3 is a diagram of the first section of bridge pushed according to an alternative embodiment of the method of FIG. 1,

- Figures 4A and 4B are respectively a side view of the support shown in Figure 1 and a vertical sectional view of this support along the line IV-IV.

The example cable-stayed bridge shown in FIGS. 1 and 2, intended to cross an obstacle 1, comprising for example a watercourse, comprises: - two foundations 2, 3 respectively constructed on the two opposite banks of the area to be crossed (hereinafter left bank for foundation 2 and right bank for foundation 3, with reference to Figures 1 and 2),

- one or more pylons 4 erected in obstacle 1; in the example drawn, the bridge has a general asymmetrical arrangement with a single pylon 4 erected closer to the left bank than to the right bank;

- piers 5 built in obstacle 1 towards the right bank; - an apron 6.

The distance between the pylon 4 and the nearest pile 5 is relatively large and is, in this example, approximately 170 m. This is why a guyed structure is used to support the deck in this area.

The pylon 4 is used for mounting a set of inclined shrouds. These shrouds each have an upper end anchored in a respective anchoring zone arranged on the pylon 4. The shrouds directed towards the right bank have their lower end anchored on the deck. Those, 7, directed towards the left bank have their lower end anchored to the ground, near the foundation 2, in order to balance the efforts of bending applied to the pylon 4 by the shrouds fixed to the deck 6.

In the example considered, the deck 6 has two sections, one 6a extending from the left bank and the other 6b extending from the right bank.

Each of these two sections is pushed from the shore by means of systems 8,9 mounted respectively on the foundations 2,3. These systems 8, 9 are of conventional constitution. Each of them comprises for example one or more jacks installed on the edge of the foundation adjacent to the obstacle 1 and exerting tensile forces on cables connected to a thrust member applied to the rear of the section of the deck.

Each section of deck 6a, 6b is constructed in successive sections in a respective assembly workshop installed on the foundation 2,3. It can be manufactured directly in this workshop, especially in the case of a concrete deck, or simply assembled from prefabricated elements. As it is built, it is pushed horizontally by the 8,9 system to free up the mounting area.

The deck section 6a is shown in its final position in FIG. 2. It extends from the foundation 2 on the left bank, rests on the pylon 4 in which an appropriate passage is provided (for example an inverted Y structure), and protrudes from pylon 4 towards the right bank over a distance di. This distance d _x can be quite large (for example 40 m), one or more inclined cables 10 are provided to support the cantilever portion of the section 6a from the pylon 4.

According to the invention, this inclined cable 10 shown in Figures 1 and 2 supports the section of apron 6a during its push. One can in particular proceed as follows.

After having carried out a portion of the deck section 6a, for example from the foundation 2 to the pylon 4 with an overshoot of d ₀ beyond the pylon (d ₀ <d; ι _. ) As shown in FIG. 1, the cable is installed support 10 by anchoring its upper end in an anchoring zone i formed in the pylon 4, and by connecting it to a jack 11 articulated at a fixed point relative to the section of deck 6a. The jack 11 is controllable in order to adjust the length of the support cable 10 until it is anchored on the pylon 4. When the deck section 6a is pushed from the left bank, the jack 8 is controlled so that the length of the support cable 10 between the pylon 4 and the deck section 6a adapts to the current position of the point of articulation of the jack 11. The deck section 6a is thus pushed into the position shown in FIG. 2.

In the example shown, the anchoring zone M _x comprises, in a manner known per se, a metal tube which is subject to the pylon 4 at the time of the preparation of the latter, this tube being intended to receive, by its end directed towards the right bank, the upper end of the support cable 10. The strands of the upper end of the cable 10 are clamped respectively in the jaws of an anchoring head arranged in a conventional manner on the other side of the metal tube. In order to allow the required angular travel of the support cable 10 between the initial and final positions of the deck section 6a shown in FIGS. 1 and 2, the bottom wall of the tube in the anchoring zone Mi is convex, preferably with a radius of constant curvature in a vertical plane passing through the axis of the tube.

In the example above, the deck section 6a is built up to the pylon 4 by other means, for example by cantilevering, or by pushing on temporary piers erected between the foundation 2 and the pylon 4. But it it should be noted that the progression of the section of apron 6a to the pylon 4 can also take place with support cables and a thrust system if the anchoring zone Mi of the support cable 10 allows sufficient angular movement, or otherwise by providing two support cables 10 successively used (one for the push to the pylon 4 and the other beyond).

In FIG. 3 is shown diagrammatically the progression of the section of apron 6a according to a variant of the method according to the invention, between its initial position represented in solid lines and corresponding to that of FIG. 1, and its final position represented in dashed lines and corresponding to that of FIG. 2. This example differs from the previous one in that the jack 11 to which the support cable 10 is connected is no longer articulated at a fixed point relative to the deck, but to a support 12 anchored to the soil near the foundation 2. This jack 11 is arranged in such a way that the support cable 10 extends between the anchoring zone M ₁ and the jack 11, bypassing a return member 13 from below, for example roller, mounted on the deck section 6a. This member 13 can in particular be placed at the front end of the deck section 6a so as to retain the latter from the front during the thrust. In the same way as in the previous example, the jack 11 can be controlled in order to adjust the length of the support cable 10 up to its anchoring on the pylon 4. When the deck section 6a is pushed from the left bank, the actuator 11 is controlled so that the lengths of the support cable 10 between the pylon 4 and the deck section 6a and between the section of the apron 6a and the articulation point of the jack 11 adapt to the current position of the return member 13. The section of the apron 6a is thus pushed into the position shown in phantom in FIG. 3.

As regards the deck section 6b, this is also shown in its final position in FIG. 2. It extends from the foundation 3 on the right bank to the front end of the deck section 6a where the two sections are assembled. The deck section 6b has a part which rests on the piles 5, and a part which protrudes by a distance i from the pile 5 closest to the pylon 4. Taking into account the fact that this distance i can be fairly large (for example more than 100 m) and that the cantilever portion of the section 6b from the stack 5 above can also be relatively massive, provision is made, as in the case of the thrust of the section of deck 6a, one or more inclined cables 14, preferably several, to support the cantilever portion of the deck section 6b. These cables 14 are connected to static supports 15 from which extend respective horizontal cables 16 anchored in the vicinity of the foundation 3 to retain the cantilever portion of the deck section 6b.

According to the invention, the deck section 6b is, during its push, not only supported by the inclined cables 14, but also retained by the horizontal cables 16, as shown diagrammatically in FIG. 2. It should be noted that the thrust of the deck section 6b can be carried out either before or after the thrust of the deck section 6a, or even at the same time as the latter. In the example considered, the procedure is as follows.

During a first step shown in FIG. 1, a portion of the deck section 6b is made and put in place on the stacks 5, with an overshoot of o beyond the stack 5 closest to the pylon 4 (from _D <from i). The installation of the portion of the deck section 6b can be carried out conventionally by pushing towards the left bank, the underside of the portion of the deck section 6b sliding on appropriate saddles installed at the tops of the piles 5 (see for example FR-A-2 758 835).

Then installed between two points 17a, 17b, for example fixed to the deck sections 6a, 6b, a temporary cable 18 which is passed through a pulley 19 mounted at the top of the pylon 4. The cable 18 is located in a vertical plane laterally offset from the plane (s) in which the inclined support cables will extend 14. The role of this cable 18 is to carry a shuttle 20. One end of a support cable 14 is anchored in an area appropriate M ₂ formed at the top of the pylon 4, and its opposite end is hooked to the shuttle 20 brought near the pylon. By moving the shuttle 20 towards point 17b, the cable of the support 14 is allowed to cross the interval separating the two deck sections 6a, 6b. This operation will be repeated for each of the support cables 14 successively installed. Note that the temporary cable 18 is optional, other means that can be used for laying cables 14.

The lower end of the cable 14 is fixed to a support 15 shown in Figures 4A and 4B. In the example shown, the lower end of the cable 14 is fixed by means of an anchoring block 21 to a plate 22 connected to a yoke 23 by bolts 24 making it possible to adjust the distance between the plate 22 and the yoke 23. The yoke 23 is articulated on the support 15 around an axis X. The support 15 comprises for example two parallel flanges 25 assembled by bolts 26. Spacers 27 are placed around the bolts 26 between the two flanges 25 to maintain the spacing of these. At the axis X, located in the upper part of the support 15, the yoke 23 is placed between the flanges 25, an axial rod not shown ensuring the articulation. Between the two sides of the yoke 23, a cylindrical spacer 28 is placed in alignment with the axis X and crossed by the articulation rod. This spacer 28 is provided with holes 29 used for fixing the horizontal cables 16.

In the lower part of the support 15, the interior of each flange 25 supports a bearing 30 which can be in the form of a roller pivoting about an axis Y perpendicular to the flanges. As shown in Figure 4B, the bearings 30 cooperate with a rail 31 fixed to the deck section 6b. The rail 31 has the shape of an I-shaped profile arranged parallel to the direction of the deck, the central part of the I being erected vertically and coming to be placed between the two bearings 30. The upper edges of the I-shaped profile are supported on the top bearings 30 in order to support the section of deck 6b while allowing it to slide in the direction of the left bank. Once the lower end of the cable 14 has been fixed to the support 15, the latter is engaged on the rail 31, then the horizontal cable or cables are fixed. The opposite end of these cables 16 is anchored to the ground at proximity to the foundation 3. To avoid disturbing the area of the deck assembly workshop, an angular deflection device 32 can be provided at the front of the foundation 3, the anchor points 33 of the horizontal cables 16 being situated laterally with respect to the foundation 3. Once the mounting of the first support 15 has been completed, the thrust of the section of deck 6b continues, which then slides relative to the static support 15.

When the cantilever mass at the front of the deck section 6b is again fairly large, new support cables 14, supports 15 and horizontal cables 16 are installed in the same manner as above. Along the direction of the deck, the interval between two consecutive supports 15 is for example of the order of 10 meters. The horizontal cables 16 can pass inside the supports 15 previously installed (between the spacers 27, 28), or next to these supports 15 if appropriate deflectors are put in place.

The inclined support cables 14 successively put in place exert on the pylon 4 bending forces in the direction of the right bank. To compensate for this, as these cables 14 are put in place, one installs on the other side of the pylon 4, towards the left bank, retaining shrouds 7 anchored to the ground and to the pylon (FIG. 1 and 2). These retaining shrouds 7 may be the final shrouds of the structure. After completing the pushing operations of the two deck sections 6a, 6b, they are secured in the central span of the bridge.

In general, the inclined support cables 10, 14 used during the thrust of the deck will be temporary cables, replaced by the final shrouds of the structure after the assembly of the two sections of decks

6a, 6b. The inclined cables 10, 14 are replaced one by one, or small groups by small groups, so that the cables and stay cables remaining in place continue to support the deck.

The final shrouds have their upper ends respectively fixed in anchoring zones of the pylon 4 having preferably served for anchoring the inclined support cables 10, 14. Their lower ends are fixed to the deck, for example by means of respective anchor blocks placed under the deck, which is crossed by guide tubes receiving the shrouds as is usual.

The construction process which has just been described above has in particular the advantage of a good adaptation in particular in the case where the gap which separates the two sections of deck to be joined is significant or in the case where the access to the area separating the two banks is difficult or prohibited.

As goes without saying, and as follows sufficiently from the foregoing, the invention is in no way limited to those of its embodiments which have been more specifically explained above: on the contrary, it embraces all variants thereof , especially :

- in cases where the cantilever portion of the deck section 6a would prove to be too large, one could use, instead of a single support cable

10, a plurality of cables 10, so as to distribute the support force at various points of the deck section 6a during its horizontal thrust. Each cable 10 would then be attached, by its upper end, in a corresponding anchoring zone arranged in the pylon 4, and fixed, by its lower end, to a corresponding jack 11, articulated at a fixed point relative to the section of deck 6a (FIGS. 1 and 2) or relative to the ground with reference to a member 13 (FIG. 3),

- In the process version described with reference to the right-hand side of FIGS. 1 and 2, the inclined support cable 14 and the horizontal retaining cable 16 could consist of two portions of the same cable angularly deflected at the level of the support 15 ,

- depending on the dimensions and the mass of the deck section 6a, 6b, at least part of the support cables

10, 14 could be duplicated and juxtaposed on the width of the deck, thus facilitating the balancing of the assembly,

- in certain cases, the inclined cables used to support the section of deck 6b could be designed to constitute the final stay cables of the bridge, which would make it possible not to have to dismantle them once the construction of the bridge is completed; in this case, the final anchoring of these shrouds on the deck portion 6b is carried out at the end of the thrust, after having dismantled the supports 15 one by one.

Claims

1. A method of constructing a cable-stayed bridge comprising an apron (6), at least one pylon (4), and inclined shrouds (7) mounted between the pylon (4) and the apron (6), characterized in that 'after having erected the pylon (4), at least one support cable (10; 14) is attached to this pylon, the support cable (10; 14) is connected to a section of the deck (6a; 6b), and said deck section is pushed from one end (2; 3) of the bridge, the support cable (10; 14) helping to support the deck section (6a; 6b) during the pushing.

2. Method according to claim 1, characterized in that the support cable (14) is connected to the deck section (6b) by means of at least one support (15) to which are fixed on the one hand the support cable (14) and on the other hand at least one retaining cable (16) anchored towards said end of the bridge (3), the deck section (6b) being arranged to slide relative to the support (15) during of the thrust while the support is substantially static.

3. Method according to claim 2, characterized in that fixed to the deck section (6b) a longitudinal rail (31) having at least one side intended to come to bear slidingly on rollers (30) mounted on the support ( 15).

4. Method according to claim 2 or 3, in which as the deck section (6b) is pushed, static supports (15) are put in place at a front end of the deck section, in them connecting to the pylon (4) by support cables (14) and to a fixed anchor (33) by retaining cables (16).

5. Method according to claim 1, characterized in that the support cable (10, -14) retains the deck section (6a; 6b) at a fixed point relative to the deck section, the length of this support cable , between said fixed point and its point of attachment to the pylon (4), being made variable by adjustment means.

6. Method according to claim 5, characterized in that the adjustment means comprise a jack (11) articulated at a front end of the deck (6a) which is oriented opposite to said end (2) of the bridge.

7. Method according to claim 5, characterized in that the adjustment means comprise a jack (11) which is fixed to the ground on the side of said end (2) of the bridge so that the support cable (10) bypasses the below the front end of the deck section (6a).

8. Method according to any one of claims 1 to 7, characterized in that during the preparation of the pylon (4), anchoring zones are formed in the pylon for anchoring the shrouds, and in that that the support cable (10; 14) is attached to the pylon (4) in one of these areas.