Method for dismantling swivel of extradosed cable-stayed bridge

Abstract

The invention provides an extradosed cable-stayed bridge swivel dismantling method which comprises the steps that an annular sliding rail foundation concentric with a main pier is arranged on a main pier bearing platform around the main pier, an annular swivel sliding rail is installed on the sliding rail foundation, and two steel arches are hung on the swivel sliding rail through a deck crane to support a bridge. Releasing a closure section of the main span and the side span of the cable-stayed bridge, integrally cutting off the main pier of the cable-stayed bridge along a plane flush with the swivel slide rail by using a rope saw, so that the whole upper structure load of the main span of the cable-stayed bridge is independently supported by the steel arch instead of being jointly supported by the pier and the steel arch, and pulling the upper structure of the main span of the cable-stayed bridge to horizontally rotate by a certain angle along the swivel slide rail to avoid a main channel under the bridge; and then dismantling the main span of the cable-stayed bridge section by section. Safe and stable conversion of the main span load of the bridge can be achieved, and safety guarantee is provided for bridge swivel dismantling construction.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge construction and relates to a rotation and dismantling method for a low-tower cable-stayed bridge. Background Art

[0002] A low-tower cable-stayed bridge is usually a reinforced concrete structure with a single tower and a single cable plane. As the bridge ages, it may suffer from irreparable damage or need to be dismantled and rebuilt due to the low navigation clearance under the bridge that cannot adapt to the development of navigation. If the conventional bridge dismantling method is used to dismantle it in situ, the construction period will be long and the navigation under the bridge will be greatly affected.

[0003] Patent CN117947717A discloses a method for rotating and dismantling a continuous beam. The technical solution is to first set a ball joint on the top of the main span pier, then dismantle the side span and the side span joint section to form a T-structure for the main span, then dismantle the permanent support on the top of the main span pier, transfer the load of the main span beam section to the ball joint, and finally use the ball joint to rotate the main span beam section for dismantling, thereby avoiding affecting the road traffic under the bridge during the dismantling of the bridge.

[0004] CN116289672 discloses a rotation and dismantling device and method for a continuous rigid frame bridge across a railway. The technical solution is to first set a circle of pile foundations around the main span piers, set a temporary rotation platform and rotation support on the pile foundations, and also set a pile foundation in the middle of the pier as a rotation axis. Then, the piers are dismantled, the bridge load is transferred to the rotation support, and then the main beam of the upper railway is cut off to form two T-frames. Finally, the two T-frames are rotated separately and then dismantled, thereby avoiding affecting the road traffic under the bridge during the bridge dismantling process.

[0005] The above two technical solutions for bridge rotation and dismantling have certain reference significance for the dismantling of low-tower cable-stayed bridges. However, the former solution requires a spherical hinge to be set at the top of the pier, so it is only applicable to continuous box-beam bridges with separate structures of piers and beams and bearings at the top of the piers. The latter solution requires pile foundations to be set around the piers and in the middle of the piers, and the piers must be removed. Therefore, it is only applicable to bridges on land with thin-walled hollow piers. For low-tower cable-stayed bridges, the piers, beams and cable towers are cast as one, so it is impossible to set a rotation hinge at the top of the pier, nor to set a pile foundation in the water outside the pier column and in the middle of the pier column. Moreover, these two technical solutions require the removal of the pier top bearing or the removal of the piers when transferring the load of the bridge structure to the rotation hinge. They are only applicable to continuous beam bridges with a small T-structure weight. For low-tower cable-stayed bridges, due to the large main span and the cable towers on the main span, the entire main span structure is heavy, and the load transfer construction by removing the piers is extremely difficult and risky. Therefore, these two technical solutions cannot be directly applied to the dismantling of low-tower cable-stayed bridges. Summary of the invention

[0006] The object of the present invention is to provide a rotation and dismantling method suitable for a low-tower cable-stayed bridge in view of the above problems.

[0007] The technical solution of the present invention is as follows:

[0008] A method for dismantling a rotating structure of a low-tower cable-stayed bridge, characterized in that it comprises the following steps:

[0009] Step 1: Remove the main beam flange within the range of the first inclined cable closest to the main tower to the tower body, lay bridge crane tracks on both sides of the main beam top surface, and set a bridge crane in the transverse direction of the bridge on both sides of the main tower, with the cantilevers at both ends of the bridge crane extending to the outside of the two sides of the bridge; the two bridge cranes can move along the bridge along the bridge crane tracks;

[0010] Step 2: a circular slide rail foundation concentric with the main pier is arranged around the main pier on the main pier cap, and a circular swivel slide rail is installed on the slide rail foundation;

[0011] Step 3: transport the two pre-processed steel arch frames to the two sides of the main pier under the bridge through two transport ships;

[0012] Step 4: Use a bridge crane to lift the two steel arch frames, and the two bridge cranes move toward the main tower along the bridge crane tracks respectively, and place the two steel arch frames symmetrically on the rotating slide rails, with the two arch feet of each steel arch frame supported on the rotating slide rails;

[0013] Step 5: Remove the bridge crane and bridge crane track; install wall connecting parts between the steel arch frame and the main pier to improve the lateral stability of the steel arch frame; insert steel wedges between the top surface of the steel arch frame and the bottom surface of the main beam, and tighten the steel wedges against the bottom surface of the main beam;

[0014] Step 6: Release the joint section between the main span and the side span of the cable-stayed bridge, and the main span forms a T-structure;

[0015] Step 7: Use a rope saw to cut off the main pier of the cable-stayed bridge along a plane flush with the rotating slide rail, so that the deadweight load of the entire upper structure of the main span of the cable-stayed bridge is converted from being supported jointly by the pier and the steel arch frame to being supported solely by the steel arch frame;

[0016] Step 8: Pull the entire upper structure of the main span of the cable-stayed bridge along the rotating slide rail to rotate a certain angle to avoid the main channel under the bridge, and then dismantle the main span of the cable-stayed bridge section by section.

[0017] The present invention adopts a steel arch frame of a steel box concrete structure as the main bearing structure for load conversion on the main span of the cable-stayed bridge, which has high bearing capacity and low cost. The main pier is integrally sawed off to smoothly convert the load on the main span structure to the steel arch frame, which can ensure construction safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the overall construction flow chart of the present invention;

[0019] Figure 2 This is a transverse schematic diagram of the bridge after the removal of the main beam wing plate between the first stay cable and the main tower;

[0020] Figure 3 This is a schematic diagram along the bridge direction of removing the main beam wing plate;

[0021] Figure 4 This is a cross-bridge schematic diagram of the arrangement of the bridge crane and the slideway foundation;

[0022] Figure 5 This is a schematic diagram of the installation method of the bridge crane and the slideway foundation along the bridge;

[0023] Figure 6 It is a schematic diagram of the plan structure of the slide foundation and the rotating slide;

[0024] Figure 7 is a schematic diagram of the cross-sectional structure of the rotary slide;

[0025] Figure 8 This is a schematic diagram of the steel arch frame being transported under the bridge;

[0026] Fig. 9 It is a side view structural diagram of the steel arch;

[0027] Fig.10 It is a schematic diagram of the cross-sectional structure of the steel arch;

[0028] Fig.11 Schematic diagram of the bridge crane hoisting the steel arch frame;

[0029] Fig.12 It is a schematic diagram of the steel arch frame installed on the rotating slideway along the bridge;

[0030] Fig.13 It is a transverse schematic diagram of the steel arch frame installed on the rotating slideway;

[0031] Fig.14 It is a schematic diagram of the state of a steel arch supporting a separate main span superstructure;

[0032] Fig.15 It is a schematic diagram of the rotation method of the main span superstructure. DETAILED DESCRIPTION

[0033] Figure 1 It is the overall construction flow chart of the present invention, and the specific construction method is as follows:

[0034] Step 1: If Figure 2 , Figure 3 As shown, firstly, the main beam flange 3 within the range from the first inclined cable 2 closest to the main tower 1 to the tower body is removed to provide space for the installation and operation of the bridge crane.

[0035] In order to improve the local bearing capacity of the main beam at the root of the main tower, plain concrete 5 may be filled in the box chamber of the main beam 4 where the flange of the main beam is removed.

[0036] like Figure 4 , Figure 5 As shown, after the main beam flange is removed, bridge crane tracks 6 are laid on both sides of the top surface of the main beam 4, and a bridge crane 7 is set in the transverse direction of the bridge on both sides of the main tower. The cantilevers at both ends of the bridge crane 7 extend to the outside of the two sides of the bridge respectively; the two bridge cranes 7 can move along the bridge direction along the bridge crane tracks 6.

[0037] When laying the bridge crane track, in order to ensure the bearing capacity of the bridge crane track, the bridge crane track can be laid along the web of the main beam.

[0038] Step 2: If Figure 4 , Figure 5 As shown, a slide rail foundation 10 is arranged on the main pier cap 8 around the main pier 9, and an annular swivel slide rail 11 is installed on the slide rail foundation 10;

[0039] The slide rail foundation can be cast with reinforced concrete, and the bottom of the slide rail foundation is consolidated with the pedestal by embedding reinforcement on the surface of the pedestal. The slide rail foundation should be higher than the highest water level, and the cross section of the slide rail foundation 10 is a circular ring concentric with the main pier.

[0040] When constructing the slide rail foundation, you can choose to carry out construction when the lowest water level is lower than the top surface of the pedestal; if the lowest water level is higher than the pedestal, it is necessary to set up a water retaining cofferdam outside the pedestal.

[0041] The slide rail foundation can be constructed simultaneously with step one.

[0042] The swivel rail 11 is made of welded steel plates and fixed on the rail base. Figure 6 As shown, it is a circular ring concentric with the slide rail base; Figure 7 As shown, the cross section of the swivel rail 11 is set to be U-shaped. In order to reduce the friction of the swivel rail, a polytetrafluoroethylene plate can be laid inside the swivel rail.

[0043] Step 3: If Figure 8 As shown, two pre-processed steel arch frames 12 are transported to the two sides of the main pier under the bridge through two transport ships.

[0044] The steel arch frame is used to provide support for the load transfer of the bridge structure and is pre-processed in the factory. Fig. 9 , Fig.10 As shown, the steel arch frame 12 adopts a steel box concrete structure, wherein the top plate 121, the bottom plate 122 and the two side plates 123 are all welded by steel plates to form the outer shell of the steel structure, and concrete is poured inside the steel arch frame.

[0045] In order to ensure the bearing capacity of the steel arch frame, stiffening ribs 124 can be welded on the top plate, bottom plate and inner sides of both side plates of the steel arch frame; further, a prestressed structure is arranged in the steel arch frame. Before pouring concrete, a corrugated pipe is arranged axially inside the steel arch frame, and prestressed tendons are passed through the corrugated pipe. After the concrete pouring is completed, the prestressed tendons are tensioned.

[0046] In order to avoid deformation of the steel arch frame under stress and ensure its bearing capacity, a tie rod is used to pull 125 degrees between the two arch feet of the steel arch frame. Four tie rods are provided, made of 200mm 40Cr steel, and fixed at both ends with nuts. In order to improve the stress bearing capacity of the tie rod installation at the arch foot of the steel arch frame, horizontal and vertical steel pipe meshes can be set in the concrete of the arch foot.

[0047] Step 4: If Fig.11 , Fig.12 As shown, the two steel arch frames 12 are lifted by the bridge crane 7, and the two bridge cranes are respectively moved along the bridge crane tracks toward the main tower, and the two steel arch frames are symmetrically placed on the swivel slide rail 11, and the two arch feet of each steel arch frame are supported in the swivel slide rail 11.

[0048] To facilitate the connection between the bridge crane and the steel arch frame, when the bridge crane lifts the steel arch frame, two triangular hangers 13 can be welded at both ends of the steel arch frame 12 respectively, and the bridge crane 7 lifts the steel arch frame 12 by connecting the triangular hangers 13.

[0049] Step 5: If Fig.13 , 14 As shown, after the steel arch frame 12 is hoisted, the bridge crane and the bridge crane track are removed; a wall connecting member 14 is set between the steel arch frame 12 and the main pier 9 to improve the lateral stability of the steel arch frame; a steel wedge block 15 is inserted between the top surface of the steel arch frame 12 and the bottom surface of the main beam 4, and the steel wedge block is pressed tightly against the bottom surface of the main beam.

[0050] The steel wedge 15 can be a steel plate with a slope, inserted between the steel arch frame and the main beam and in close contact with the bottom of the beam.

[0051] Step 6: Release the joint section between the main span and the side span of the cable-stayed bridge, and the main span forms a T-structure;

[0052] Step 7: Use a rope saw to cut the main pier 9 of the cable-stayed bridge along a plane flush with the swivel slide rail, so that the deadweight load of the entire upper structure of the main span of the cable-stayed bridge is converted from being supported jointly by the pier 9 and the steel arch frame 12 to being supported solely by the steel arch frame 12, completing the load force system conversion.

[0053] Step 8: Pull the entire upper structure of the main span of the cable-stayed bridge along the rotating slide rail to rotate at a certain angle to avoid the main channel under the bridge. Fig.15As shown, during the rotation, the steel arch 12 slides along the rotating track 11 in a circular direction, and rotates with the main span upper structure it carries. After the rotation is completed, the main span of the cable-stayed bridge is dismantled section by section and transported away by a transport ship. Since the main channel is given up, the river navigation is not affected during the bridge dismantling process.

Claims

1. A method for dismantling a rotating structure of a low-tower cable-stayed bridge, characterized in that: The following steps are involved: Step 1: Remove the main beam flange within the range of the first inclined cable closest to the main tower to the tower body, lay bridge crane tracks on both sides of the main beam top surface, and set a bridge crane in the transverse direction of the bridge on both sides of the main tower, with the cantilevers at both ends of the bridge crane extending to the outside of the two sides of the bridge; the two bridge cranes can move along the bridge along the bridge crane tracks; Step 2: a circular slide rail foundation concentric with the main pier is arranged around the main pier on the main pier cap, and a circular swivel slide rail is installed on the slide rail foundation; Step 3: transport the two pre-processed steel arch frames to the two sides of the main pier under the bridge through two transport ships; Step 4: Use a bridge crane to lift the two steel arch frames, and the two bridge cranes move toward the main tower along the bridge crane tracks respectively, and place the two steel arch frames symmetrically on the rotating slide rails, with the two arch feet of each steel arch frame supported on the rotating slide rails; Step 5: Remove the bridge crane and bridge crane track; install wall connecting parts between the steel arch frame and the main pier to improve the lateral stability of the steel arch frame; insert steel wedges between the top surface of the steel arch frame and the bottom surface of the main beam, and tighten the steel wedges against the bottom surface of the main beam; Step 6: Release the joint section between the main span and the side span of the cable-stayed bridge, and the main span forms a T-structure; Step 7: Use a rope saw to cut off the main pier of the cable-stayed bridge along a plane flush with the rotating slide rail, so that the deadweight load of the entire upper structure of the main span of the cable-stayed bridge is converted from being supported jointly by the pier and the steel arch frame to being supported solely by the steel arch frame; Step 8: Pull the entire upper structure of the main span of the cable-stayed bridge along the rotating slide rail to rotate a certain angle to avoid the main channel under the bridge, and then dismantle the main span of the cable-stayed bridge section by section.

2. The method for dismantling a rotating short-tower cable-stayed bridge according to claim 1, characterized in that: In the step 1, plain concrete is filled in the main beam box room where the main beam flange is removed to improve the local bearing capacity of the main beam at the root of the main tower.

3. The method for dismantling a rotating short-tower cable-stayed bridge according to claim 1 is characterized in that: The bridge crane track on the top surface of the main beam is laid along the web of the main beam.

4. The method for dismantling a rotating structure of a low-tower cable-stayed bridge according to claim 1, characterized in that: The slide rail foundation is cast with reinforced concrete, the bottom of the slide rail foundation is consolidated with the pedestal by embedding reinforcement on the surface of the pedestal, the slide rail foundation is higher than the highest water level, and the cross-section of the slide rail foundation is a circular ring.

5. The method for dismantling a rotating structure of a low-tower cable-stayed bridge according to claim 1 is characterized in that: When constructing the slide foundation on the pedestal, when the water level is higher than the top surface of the pedestal, a steel cofferdam is set outside the pedestal to cast the slide foundation.

6. The method for dismantling a rotating short-tower cable-stayed bridge according to claim 1, characterized in that: The swivel slide rail is welded from steel plates and fixed on the slide rail base. The cross section of the swivel slide rail is U-shaped, and a polytetrafluoroethylene slide plate is laid inside the slide rail.

7. The method for dismantling a rotating short-tower cable-stayed bridge according to claim 1, characterized in that: The steel arch frame is a steel box concrete structure. The outer shell of the steel arch frame includes a top plate, a bottom plate and two side plates, all of which are welded with steel plates. Concrete is poured inside the steel arch frame, and tie rods are used to pull the two arch feet of the steel arch frame.

8. The method for dismantling a rotating short-tower cable-stayed bridge according to claim 7, characterized in that: Stiffening ribs are welded on the top plate, bottom plate and inner sides of both side plates of the steel arch frame. A corrugated pipe is arranged axially inside the steel arch frame, and prestressed tendons are passed through the corrugated pipe and pre-tensioned.

9. The method for dismantling a rotating low-tower cable-stayed bridge according to claim 1, characterized in that: When the bridge crane lifts the steel arch frame, two triangular hoists are respectively welded at both ends of the steel arch frame, and the bridge crane lifts the steel arch frame through the triangular hoists.

10. The method for dismantling a rotating short-tower cable-stayed bridge according to claim 1, characterized in that: The steel wedge is a steel plate with a slope, which is inserted between the steel arch frame and the main beam and is in close contact with the bottom of the beam.

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