A tied arch bridge few support dismantling construction method suitable for navigation restriction

Abstract

The application discloses a tied-arch bridge few-support demolition construction method suitable for navigation restriction, and is suitable for the tied-arch bridge demolition construction which is restricted by navigation and cannot be closed in the whole process, has complex external environment such as surrounding buildings, is limited in demolition operation space, and cannot be implemented by the blasting demolition and integral demolition method. The tied-arch bridge few-support demolition construction method adopts a block demolition method, considers the stress conditions of the steel pipe pile support and the remaining arch bridge structure in each step of demolition according to the reverse sequence segmented hoisting and demolition principle, makes the bridge always in a stable frame type structure state in the demolition process, solves the technical problems currently faced by the tied-arch bridge demolition, is more suitable for the complex external environment restriction, greatly reduces the interference degree of the external environment itself, is more scientific, and is safer.

Description

A construction method for dismantling tie-arch bridges with fewer supports, applicable to navigation restrictions. Technical Field

[0001] This invention relates to the field of bridge demolition technology. More specifically, this invention relates to a method for demolishing tied-arch bridges with minimal supports, suitable for use under navigation restrictions. Background Technology

[0002] A tied arch bridge, also known as a thrustless arch composite system bridge, is a type of bridge that combines the two basic structural forms of arch and beam, integrating the advantages of both. The load is borne jointly by the arch and beam, giving full play to the structural performance and combined effect of the arch under compression and the beam under bending. The horizontal thrust at the arch end is borne by the tie rod, so that no horizontal thrust is generated at the arch end support.

[0003] Simply supported beam-arch composite bridges are used only for under-deck bridges. They are all thrustless composite arch systems with a statically determinate external structure and a highly statically indeterminate internal structure. The arch rib structure is generally made of steel-concrete composite tubular material or reinforced concrete. When the bridge span is small, wind bracing is often not required, while for larger spans, wind bracing is necessary to increase the overall stability of the arch bridge. In addition to the arch ribs, the main load-bearing components include stiffening longitudinal beams, which, together with the transverse beams, form a planar frame connected by suspenders to achieve shared load-bearing. Based on the relative stiffness of the arch ribs and tie rods (beams), thrustless arch composite systems can be divided into three basic systems: flexible tie-rigid arches, rigid tie-flexible arches, and rigid tie-rigid arches.

[0004] Currently, there are two main categories of methods for demolishing tied-arch bridges: blasting demolition and non-blasting demolition. Non-blasting demolition is further divided into two types: integral demolition and segmented demolition. While blasting and integral demolition are highly efficient, they have strict requirements on the surrounding environment. With the upgrading and reconstruction of transportation engineering in my country, a large number of bridge demolition projects have emerged, making the external environment increasingly complex and increasing the demand for construction safety. This has rendered blasting and integral demolition methods unsuitable, leading to the emergence of segmented demolition methods. At present, the system of methods for demolishing prestressed reinforced concrete tied-arch bridges in China is not yet mature, and further experience in the demolition of such bridges is needed, especially for arch bridges with large spans and complex structural stress patterns, where it is necessary to reduce interference with the external environment and lower construction safety risks. Summary of the Invention

[0005] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0006] Another objective of this invention is to provide a method for dismantling tied-arch bridges with fewer supports that is suitable for navigation restrictions, in order to solve the technical problem of high safety risks in the dismantling of tied-arch bridges in the prior art.

[0007] To achieve these objectives and other advantages according to the present invention, a method for dismantling tie-arch bridges with minimal supports suitable for navigation restrictions is provided, comprising the following steps:

[0008] S1. Remove the pedestrian walkway slabs and sleeper beams on the bridge deck;

[0009] S2. Symmetrically select support positions along the length of each tie rod. Install steel pipe pile supports vertically at each support position. The length of the steel pipe pile supports in the longitudinal direction of the bridge is less than the distance between two adjacent crossbeams on the bridge deck. Pre-drill holes in the bridge deck corresponding to the positions of the steel pipe pile supports. The lower end of the steel pipe pile supports extends into the underwater soil for fixation, and the upper end extends upward to directly below the arch rib. The steel pipe pile supports abut against the distribution beams at the bottom of the tie rod and the bottom of the arch rib to form upward support for the tie rod and the arch rib.

[0010] S3. Remove all bridge deck panels and pedestrian walkway cantilever beams;

[0011] S4. Remove the bridge deck crossbeams, and retain the crossbeams and end crossbeams located on both sides of the longitudinal bridge at the front and rear of the steel pipe pile support.

[0012] S5. Divide the arch rib into sections, cut off the lower end of the hanger, and from the middle to both sides, first remove the central wind brace, the middle section of the arch rib and the corresponding hanger, and then remove the side wind brace, the side section of the arch rib and the corresponding hanger.

[0013] S6. The tie rod is divided into a mid-span tie rod and an end tie rod. The mid-span tie rod is located between the two crossbeams near the middle of the retained section. The mid-span tie rod and the part of the steel pipe pile support above the tie rod are removed.

[0014] S7. Remove all remaining crossbeams and end tie rods;

[0015] S8. Remove the steel pipe pile support and the substructure at both ends of the arch bridge.

[0016] Preferably, the steel pipe pile support includes four steel pipe columns arranged along the top corner of a square, wherein two steel pipe columns are located outside the tie rod, and the other two steel pipe columns are located inside the tie rod and pass upward through the bridge deck at the corresponding positions. The distribution beam is connected between the two steel pipe columns in the transverse direction of the bridge. The steel pipe pile support provides support to the tie rod through the two lower distribution beams and to the arch rib through the two upper distribution beams. A support frame is connected between the bottom of the distribution beam and the steel pipe column, and a connecting rod is also connected between the steel pipe columns.

[0017] The construction of the steel pipe pile support in step S2 includes the following steps:

[0018] A1. Before setting up the steel pipe pile support, a section of the bridge deck at the corresponding location shall be removed or cut in advance;

[0019] A2. Install all steel pipe columns, with the steel pipe columns connected upwards in segments. The segment length of the steel pipe column is less than the distance between the arch rib at the corresponding position and the tie rod below. Weld connecting rods onto the steel pipe columns.

[0020] A3. Weld the distribution beams to the bottom of the tie rod and the bottom of the arch rib on the steel pipe column respectively, to ensure that the distribution beams are in full contact with the bottom of the tie rod and the bottom of the arch rib.

[0021] A4. Weld a support frame between the bottom of the distribution beam and the steel pipe column.

[0022] Preferably, the two support positions are arranged at the vertical positions where the side wind braces are located on both sides.

[0023] Preferably, when installing the steel pipe pile support, if there is a gap between the tie rod or the arch rib and the corresponding distribution beam, it is filled by setting a thin sheet of iron.

[0024] Preferably, after the steel pipe pile support is installed, a crash bar is installed on the outside of each steel pipe pile support.

[0025] Preferably, the lower distribution beam passes horizontally through the two correspondingly connected steel pipe columns, and the top of the steel pipe column has a groove extending downward along the transverse direction corresponding to the distribution beam. The upper distribution beam is embedded and fixed in a pair of grooves located in the transverse direction, and the two ends of the upper and lower distribution beams extend to the outside of the steel pipe columns.

[0026] Preferably, the arch rib is divided into five segments, which are a central arch rib, two side arch ribs, and two end arch ribs. The central arch rib is connected to the central wind brace, and the side arch ribs are connected to the side wind brace.

[0027] Preferably, the two ends of the two distribution beams on the upper layer of the steel pipe pile support extend to the outer side of the steel pipe column, forming an extension. When removing the side arch rib, a pulley guiding device is installed at the distribution beam on the upper layer of the steel pipe pile support. The pulley guiding device includes:

[0028] A bearing housing, with a bearing at its center, is connected to the two outer extensions of the distribution beam at a higher position via the bearing sleeve.

[0029] A rotating arm, one end of which is fixedly connected to a bearing seat and extends radially along the corresponding distribution beam;

[0030] A telescopic arm is arranged along the transverse direction of the bridge and has a fixed end and a telescopic end, wherein the fixed end is fixedly connected to the other end of the rotating arm and the telescopic end faces the side of the arch rib.

[0031] A clamping plate is fixed to the telescopic end of the telescopic arm, and the side of the clamping plate facing the arch rib is designed to be tightly fitted against the arch rib.

[0032] The receiver includes a base frame, one end of which is fixedly connected to the extension of the lower distribution beam, and the other end is fixedly connected to the steel pipe column below the higher distribution beam. A telescopic airbag is fixed on the base frame near the higher distribution beam. The upper end of the telescopic airbag is connected to a rotating arm. An electric air pump is also fixed on the base frame. The electric air pump is connected to the telescopic airbag and is used to control the size of the telescopic airbag.

[0033] The rotating arm is positioned above the lower-positioned distribution beam and above the side arch rib. Before cutting the side arch rib, the telescopic arms on both sides extend towards the side arch rib until the two clamping plates clamp the side arch rib. The arch bridge is then dismantled by a floating crane. After cutting the side arch rib and connecting it to the side arch rib by the floating crane, the posture of the side arch rib is adjusted, raising the lower end of the side arch rib. Under the action of the clamping plates on both sides, the rib rotates around the bearing. After adjustment, the telescopic airbag is inflated by an electrically controlled air pump. The telescopic airbag supports the rotating arm, and then the telescopic arm is driven to retract, releasing the clamping of the side arch rib. The floating crane removes the side arch rib, the telescopic airbag is deflated, and the rotating arm is placed on the base frame. It is then moved along with the dismantling of the portion of the steel pipe pile support above the tie rod.

[0034] Preferably, a construction passage is provided at the top of the arch rib. The construction passage includes scaffolding bodies spaced apart along the extension direction of the arch rib. Each scaffolding body includes two uprights and two horizontal bars that are fixed to the arch rib on its four sides. Adjacent uprights and horizontal bars are welded together. The two ends of the two horizontal bars of each scaffolding body extend outwards respectively. The ends of the upper and lower horizontal bars on the same side are connected vertically to edge protection pipes. The top of the edge protection pipes is higher than the top of the corresponding cross section of the arch rib. In the extension direction of the arch rib, the upper ends of adjacent edge protection pipes are connected in sequence to protective nets. Walking boards are laid and connected between the upper horizontal bars.

[0035] Construction workers cut and hoisted the arch ribs through the designated construction access channels.

[0036] This invention offers at least the following beneficial effects: A method for dismantling tied-arch bridges with minimal support structures, applicable to navigation restrictions, addresses the challenges of limited waterway access, complex external environments such as surrounding buildings, confined dismantling space, and the inability to implement blasting or overall dismantling methods. This method employs a segmented dismantling approach, based on a reverse-sequence segmented dismantling principle. It considers the stress on the steel pipe pile supports and the remaining arch bridge structure at each dismantling step, ensuring the bridge remains in a stable frame structure throughout the dismantling process. This method solves the current technical difficulties faced in dismantling tied-arch bridges, is more applicable to complex external environments, significantly reduces interference with the external environment, and is more scientific and safer.

[0037] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0038] Figure 1 is a front view structural diagram of the arch bridge, the construction object of this invention;

[0039] Figure 2 is a side view of the main structure of the upper part of the arch bridge, which is the object of construction according to the present invention;

[0040] Figure 3 is a front view of the steel pipe pile support installation corresponding to step S2 of the present invention.

[0041] Figure 4 is a side view of the steel pipe pile support installed in step S2 of the present invention;

[0042] Figure 5 is a side view of the arch bridge construction object of the present invention corresponding to step S3;

[0043] Figure 6 is a front view of the structure after removing the crossbeam and the central arch rib in steps S4-S5 of the present invention.

[0044] Figure 7 is a front view of the structure after removing the side arch ribs and end arch ribs in step S5 of the present invention.

[0045] Figure 8 is a front view structural diagram of the structure after removal in step S6 of the present invention;

[0046] Figure 9 is a front view structural diagram of the structure after removal in step S7 of the present invention;

[0047] Figure 10 is an enlarged front view of a pulley guide device installed on the top of a steel pipe pile support according to an embodiment of the present invention;

[0048] Figure 11 is a side view of an embodiment of the present invention when the anti-collision bar is installed;

[0049] Instruction manual drawing reference numerals:

[0050] 1. Arch rib, 2. Tie rod, 3. Hanger rod, 4. Substructure at both ends of the arch bridge, 5. Pedestrian walkway slab on the bridge deck, 6. Sleeper beam, 7. Steel pipe pile support, 8. Distribution beam, 9. Bridge deck, 10. Pedestrian walkway cantilever beam, 11. Crossbeam, 12. End crossbeam, 13. Mid-span brace, 14. Side brace, 15. Mid-span tie rod, 16. End tie rod, 17. Steel pipe column, 18. Support frame, 19. Connecting rod, 20. Anti-collision bar, 21. Groove, 22. Mid-arch rib, 23. Side arch rib, 24. End arch rib, 25. Extension, 26. Bearing seat, 27. Swing arm, 28. Telescopic arm, 29. Clamping plate, 30. Base frame, 31. Telescopic airbag, 32. Electric air pump. Detailed Implementation

[0051] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0052] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified. In the description of this invention, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0053] As shown in Figures 1-9, this invention provides a method for dismantling tied-arch bridges with fewer supports, applicable to navigation restrictions. This method is suitable for dismantling arch bridges with high-voltage lines on their upstream or downstream side, those requiring reduced channel compression, those in complex environments, and those with large spans. The method includes the following steps:

[0054] S1. As shown in Figure 1-2, a truck crane is used to remove the pedestrian walkway slab 5 on the bridge deck. Then, a wire saw is used to statically cut the sleeper beam 6 and other auxiliary facilities to reduce the load. Finally, a truck crane is used to lift and transport the dismantled structures.

[0055] S2. As shown in Figure 3-4, a bottom support system is established. Support positions are symmetrically selected along the length of each tie rod 2. At each support position, a steel pipe pile bracket 7 is installed vertically. The longitudinal length of the steel pipe pile bracket 7 is less than the distance between two adjacent crossbeams 11 on the bridge deck. Holes are pre-drilled in the bridge deck 9 corresponding to the positions of the steel pipe pile bracket 7. The steel pipe pile bracket 7 has an overall frame structure. A truck crane combined with a vibratory hammer is used to install the steel pipe piles. The lower end of the steel pipe pile bracket 7 extends into the underwater soil for fixation, and the upper end extends upwards to directly below the arch rib 1. Distribution beams 8 are respectively installed at the bottom of the tie rod 2 and the bottom of the arch rib 1 to provide upward support for the tie rod 2 and the arch rib 1. The arch rib 1 and tie rod 2 are then connected vertically by the steel pipe pile bracket 7, forming a stable triangular support structure.

[0056] S3. As shown in Figure 5, all bridge deck panels 9 and pedestrian cantilever beams 10 are statically cut using a wire saw to further unload the load. Then, the bridge deck panels 9 and pedestrian cantilever beams 10 are lifted and transported away using a truck crane in a backward manner. The load is removed sequentially from the middle of the bridge to the abutments on both sides. First, the bridge deck panels 9 are removed, and then the pedestrian cantilever beams 10 are removed. The truck crane must not stand on the crossbeams 11 after the cantilever beams have been cut.

[0057] S4. As shown in Figure 6, the floating crane enters the site and removes the bridge deck crossbeam 11. The crossbeam 11 and the end crossbeam 12 located on the front and rear sides of the steel pipe pile support 7 in the longitudinal direction of the bridge are retained to play a stabilizing role in the lateral connection.

[0058] S5. As shown in Figures 6-7, the arch rib 1 is segmented, and the lower end of the hanger rod 3 is cut off. Starting from the middle and moving towards both sides, first remove the central wind brace 13, the middle section of the arch rib 1, and the corresponding hanger rod 3. Then remove the side wind braces 14, the side sections of the arch rib 1, and the corresponding hanger rod 3. During dismantling, first use a wire saw to statically cut at the segmentation nodes of the arch rib 1, and then use a floating crane to dismantle it. After cutting off the connection between the lower end of the hanger rod 3 and the tie rod 2, it is dismantled along with the arch rib 1, hoisted to the shore, broken at a low speed, and transported off-site.

[0059] S6. As shown in Figures 7-8, tie rod 2 is divided into mid-span tie rod 15 and end tie rod 16. Mid-span tie rod 15 is located between the two remaining crossbeams 11 near the middle. The mid-span tie rod 15 and the portion of the steel pipe pile support 7 above tie rod 2 are removed. Static cutting with rope saws is also used, and the removal and transportation are carried out using a floating crane.

[0060] S7. As shown in Figures 8-9, remove all remaining crossbeams 11 and end tie rods 16. First, use a floating crane to remove the remaining crossbeams 11, and then remove the end tie rods 16.

[0061] S8. As shown in Figure 9, the steel pipe pile support 7 and the lower structure 4 such as the piers and abutments at both ends of the arch bridge are dismantled using a floating crane, thereby completing the demolition of the entire arch bridge.

[0062] For ease of explanation, taking the left and right extension directions of Figure 1 as the longitudinal direction of the bridge, the original bridge in its completed state had a downward deflection at mid-span. After the arch rib 1 was cut off, the deformation increased and the bending moment increased. The stability of the arch rib 1 structure was the worst after disintegration. By setting up steel pipe pile support 7 and distribution beam 8 to provide upward support for the arch rib 1 and tie rod 2, the bending resistance of the structure that has not yet been demolished can be significantly improved.

[0063] When the bridge deck structure is first removed to reduce the load, the remaining arch rib 1, the wind bracing between arch rib 1, tie rod 2, and the horizontal beams 11 on both sides of the steel pipe pile support 7 and the end horizontal beam 12 are left. The main structure is a frame structure. After cutting the middle arch rib 22, the part above tie rod 2 is retained on the left and right sides to form a symmetrical and structurally stable frame structure through the connection between the pair of side arch ribs 1, the side wind bracing 14, the side arch rib 23 and the tie rod 2. The side arch rib 23 is supported by the distribution beam 8 at the upper end of the steel pipe pile support 7. The frame structure is maintained at the height of tie rod 2 through the end horizontal beam 12 and the horizontal beams 11 on both sides of the steel pipe pile support 7. At this time, the maximum deformation and bending moment exist at the tie rod 15 in the middle of the span.

[0064] Then, when the arch ribs 1 on both sides are removed, the frame structure at the height of tie rod 2 is retained as a whole. After the arch ribs 1 are removed, the part of the steel pipe pile support 7 above tie rod 2 is also removed. At this time, the maximum deformation and bending moment still exist at tie rod 15 in the middle of the span.

[0065] When dismantling the structure at tie rod 2, the mid-span tie rod 15 is first cut out in sections. At this time, the end tie rods 16 on both sides, the end crossbeams 12, and the crossbeams 11 on both sides of the steel pipe pile support 7 are retained to form a frame structure. The maximum deformation and bending moment exist on the two crossbeams 11 near the center of the arch bridge. Finally, all the remaining structures at the corresponding height are dismantled in sequence according to the height direction.

[0066] In response to the challenges of dismantling the Tie-Arch Bridge 2, including navigation restrictions, the inability to completely close off the waterway, complex external environments such as surrounding buildings, limited demolition space, and the impracticality of blasting or overall demolition methods, this embodiment adopts a segmented demolition method. Based on the principle of reverse-sequential segmented dismantling, it considers the stress on the steel pipe pile support 7 and the remaining arch bridge structure at each step of the demolition process. During the demolition, the bridge remains in a stable frame structure state, solving the technical difficulties currently faced in the dismantling of the Tie-Arch Bridge 2. This method is more applicable to complex external environmental constraints, significantly reduces interference with the external environment itself, and is more scientific and safer.

[0067] In another technical solution, as shown in FIGS. 3-4, the steel pipe pile bracket 7 includes four steel pipe columns 17 arranged at the square vertices. The center-to-center distance of the steel pipe columns 17 is 2.5 m. P630×7 mm spiral steel pipes are used with an embedded depth of 10 m. Two of the steel pipe columns 17 are located outside the tie rod 2, and the other two steel pipe columns 17 are located inside the tie rod 2 and pass upward through the bridge deck 9 at the corresponding positions. The distribution beam 8 is connected transversely between the two steel pipe columns 17. The steel pipe pile bracket 7 provides support for the tie rod 2 through the two lower distribution beams 8 and provides support for the arch rib 1 through the two upper distribution beams 8. A support frame 18 is connected between the bottom of the distribution beam 8 and the steel pipe column 17 to reduce the span of the distribution beam 8. Double-pinned I25a is used. A connecting rod 19 is also connected between the steel pipe columns 17. One set of diagonal bracing horizontal bracing (channel 25) can be provided for the connecting rod 19, and the vertical distance between the upper and lower layers of the horizontal bracing is 1.5 m.

[0068] In step S2, the construction of the steel pipe pile bracket 7 includes the following steps:

[0069] A1. Before setting the steel pipe pile bracket 7, remove or cut a piece of the bridge deck 9 at the corresponding position in advance;

[0070] A2. Install all the steel pipe columns 17. The steel pipe columns 17 are continuously connected upward in segments. The segment length of the steel pipe columns 17 is less than the distance between the arch rib 1 and the lower tie rod 2 at the corresponding position. The connecting rod 19 is welded on the steel pipe columns 17;

[0071] A3. Weld the distribution beam 8 on the steel pipe columns 17 corresponding to the bottom of the tie rod 2 and the bottom of the arch rib 1 respectively, ensuring that the distribution beam 8 is in full contact with the bottom of the tie rod 2 and the bottom of the arch rib 1;

[0072] A4. Weld the support frame 18 between the bottom of the distribution beam 8 and the steel pipe column 17.

[0073] Use a 25t-class truck crane and a DZ120-type vibratory hammer to clamp and install the steel pipe columns 17. Use the bridge deck 9 as the construction passage. The bridge deck 9 above the steel pipe pile bracket 7 is cut and removed in advance to facilitate the lowering of the steel pipes from the bridge deck. The length of the steel pipe extension of the steel pipe column 17 < the height between the arch rib 1 and the tie rod 2, so that the steel pipe can pass through and be installed under the arch rib 1. Keep a distance of more than 1 m between the boom of the truck crane and the arch rib 1. Each steel pipe pile is 1 segment per 6 m, and the connection time < 15 min. The exciting force of the vibratory hammer > the dynamic side friction resistance of the steel pipe pile. The dynamic side friction resistance of the steel pipe column 17 with an embedded depth of 10 m is 367 KN < the exciting force of the DZ120-type vibratory hammer is 775 KN, meeting the requirements.

[0074] Q

[0074] , st ,

[0073] , , = u×πd×∑(h×fs )=0.25×(3.14×0.63)×(96.3×2+68.6×8)=367KN

[0075] In another technical solution, as shown in Figure 3, the two support positions are arranged at the vertical positions where the side wind braces 14 are located on both sides.

[0076] In the longitudinal direction of the bridge, the two steel pipe pile supports 7 on the left or the two steel pipe pile supports 7 on the right are vertically connected to the corresponding side arch ribs 23 and end tie rods 16, forming a three-dimensional stable frame structure together with the side wind brace 14, the end crossbeam 12, and the crossbeams 11 on the left and right sides of the steel pipe pile support 7.

[0077] In another technical solution, as shown in Figure 3, when installing the steel pipe pile support 7, if there is a gap between the tie rod 2 or the arch rib 1 and the corresponding distribution beam 8, a thin sheet of iron is used to fill the gap, so that the steel pipe pile support 7 is in close contact with the tie rod 2 and the arch rib 1, forming a good support.

[0078] In another technical solution, as shown in Figure 11, after the steel pipe pile support 7 is installed, a crash barrier 20 is installed on the outside of each steel pipe pile support 7. The crash barriers 20 are installed 2.5m upstream and downstream and front and rear of the steel pipe pile support 7. The crash barriers 20 are made of P630×7mm spiral steel pipe, with an insertion depth of 5m. The crash barriers are painted with black and yellow warning paint and are equipped with signs (2.5m×2.5m) and 1KW warning lights.

[0079] In another technical solution, as shown in Figures 3-4 and 10, the lower distribution beam 8 passes horizontally through the two corresponding steel pipe columns 17. The top of each steel pipe column 17 has a groove 21 extending downwards along the transverse direction corresponding to the distribution beam 8. The upper distribution beam 8 is respectively embedded and fixed in a pair of grooves 21 located in the transverse direction. Both ends of the upper and lower distribution beams 8 extend to the outer sides of the steel pipe columns 17. The grooves 21 facilitate the installation and fixation of the upper distribution beam 8, maintaining direct and stable structural stress and force transmission.

[0080] In another technical solution, as shown in Figures 3 and 6, the arch rib 1 is divided into five sections. These five sections consist of a central arch rib 22, two side arch ribs 23, and two end arch ribs 24. The central arch rib 22 connects to the central wind brace 13, and the side arch ribs 23 connect to the side wind braces 14. When dismantling the arch rib 1 in sections, using a double floating crane to lift it as a whole can easily lead to lateral instability. Therefore, the arch rib 1 is divided into five sections according to its length. The central arch rib 22 section is dismantled first, followed by the side arch ribs 1 section and the end arch ribs 24 section. This approach also reduces the impact on surrounding high-voltage lines.

[0081] In another technical solution, as shown in Figure 10, the two ends of the two distribution beams 8 on the upper layer of the steel pipe pile support 7 extend to the outer side of the steel pipe column 17, forming an extension 25. When removing the side arch rib 23, a pulley guide device is installed at the distribution beams 8 on the upper layer of the steel pipe pile support 7. The pulley guide device includes:

[0082] The bearing housing 26 has a bearing at its center and is connected to the two extensions 25 of the distribution beam 8 at a higher position by means of the bearing sleeve.

[0083] A rotating arm 27, one end of which is fixedly connected to a bearing seat 26 and extends radially along the corresponding distribution beam 8;

[0084] The telescopic arm 28 is arranged along the transverse bridge direction and has a fixed end and a telescopic end, wherein the fixed end is fixedly connected to the other end of the rotating arm 27 and the telescopic end faces the side of the arch rib 1.

[0085] The clamping plate 29 is fixed to the telescopic end of the telescopic arm 28, and the side of the clamping plate 29 facing the arch rib 1 is designed to be tightly fitted to the arch rib 1.

[0086] The receiver includes a base frame 30, one end of which is fixedly connected to the extension 25 of the lower distribution beam 8, and the other end is fixedly connected to the steel pipe column 17 below the higher distribution beam 8. A telescopic airbag 31 is fixedly mounted on the base frame 30 near the higher distribution beam 8. The upper end of the telescopic airbag 31 is connected to the rotating arm 27. An electric air pump 32 is also fixedly mounted on the base frame 30. The electric air pump 32 is connected to the telescopic airbag 31 and is used to control the size of the telescopic airbag 31.

[0087] The slewing arm 27 is positioned above the lower-positioned distribution beam 8 and the side arch rib 23. Before cutting the side arch rib 23, the telescopic arms 28 on both sides extend towards the side arch rib 23 until the two clamping plates 29 clamp the side arch rib 23. The arch bridge is then dismantled by a floating crane. After cutting the side arch rib 23 and connecting it to the floating crane, the posture of the side arch rib 23 is adjusted, raising the lower end of the side arch rib 23. Under the action of the clamping plates 29 on both sides, the rib rotates around the bearing. After adjustment, an electrically controlled air pump inflates the telescopic airbag 31, which supports the slewing arm 27. Then, the telescopic arms 28 are driven to retract, releasing the clamping of the side arch rib 23. The floating crane removes the side arch rib 23, and the telescopic airbag 31 deflates, allowing the slewing arm 27 to rest on the base frame 30. Subsequently, it moves along with the dismantling of the portion of the steel pipe pile support 7 above the tie rod 2.

[0088] For the side arch rib 23 that is about to be cut and dismantled, it is prone to violent swaying when it is close to the height of the high-voltage line and is in a non-suspended balance state. It is not easy to adjust the balance position smoothly. When installing the steel pipe pile support 7, the pulley guide device is installed on the top of the steel pipe pile support 7 in advance. When dismantling the middle arch rib 22, it is kept away from the arch rib 1. Before cutting the side arch rib 23, the side arch rib 23 is clamped and then cut. This can be used in conjunction with the floating crane to ensure the safety of the overall structural support connection during the cutting of the side arch rib 23. After the cutting is completed, the lower end of the side arch rib 23 is lifted by the floating crane. The higher end of the side arch rib 23 is still abutting against the upper distribution beam 8 and is prevented from falling by the clamping action of the clamp plate 29. With the rotation, the side arch rib 23 reaches the balance position at the highest point of the center. Then the clamping action is released and it is transported away by the floating crane, avoiding the unsafe factor of swaying during the lifting of the side arch rib 23 by the floating crane.

[0089] In another technical solution, as shown in Figure 1, a construction passage is provided at the top of the arch rib 1. The construction passage includes scaffolding bodies spaced apart along the extension direction of the arch rib 1. Each scaffolding body includes two uprights and two horizontal bars that are fixed to the arch rib 1 on its four sides. Adjacent uprights and horizontal bars are welded together. The two ends of the two horizontal bars of each scaffolding body extend outwards respectively. The ends of the two horizontal bars on the same side are connected vertically to edge protection pipes. The top of the edge protection pipes is higher than the top of the corresponding cross section of the arch rib 1. In the extension direction of the arch rib 1, the upper ends of adjacent edge protection pipes are connected in sequence to protective nets. Walking boards are laid and connected between the upper horizontal bars.

[0090] Construction workers cut and hoisted the arch rib 1 through the set-up construction channel.

[0091] The scaffolding is wrapped with an arch rib 1, which is continuously laid from the arch foot to the highest working point on the arch top. The construction passage is 3.0m wide, the uprights are spaced 60cm apart, and the steel pipes for edge protection on both sides are 1.2m high. 18cm high kickboards and protective nets are installed.

[0092] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for dismantling scaffolding in tie-arch bridges with limited support structures, applicable to navigation restrictions, characterized in that, The steps include: S1, removing the bridge deck pedestrian walkway slabs and sleeper beam ancillary facilities; S2, symmetrically selecting support positions along the length of the tie rods on each side, and installing steel pipe pile supports vertically at each support position. The length of the steel pipe pile supports in the longitudinal direction of the bridge is less than the spacing between two adjacent crossbeams of the bridge deck. Holes are pre-drilled in the bridge deck corresponding to the positions of the steel pipe pile supports. The lower end of the steel pipe pile supports extends into the underwater soil for fixation, and the upper end extends upward to directly below the arch rib. Distribution beams are installed at the bottom of the tie rods and the bottom of the arch ribs respectively to form upward support for the tie rods and arch ribs; S3, removing all bridge deck slabs and pedestrian walkway cantilever sections. S4. Remove the bridge deck crossbeams, retaining the crossbeams and end crossbeams located on both sides of the longitudinal bridge along the steel pipe pile supports; S5. Divide the arch ribs into sections, cut off the lower ends of the hangers, and from the middle to both sides, first remove the central wind brace, the middle section of the arch rib and the corresponding hangers, then remove the side wind braces, the side section of the arch rib and the corresponding hangers; S6. Divide the tie rods into mid-span tie rods and end tie rods. The mid-span tie rod is located between the two remaining crossbeams near the middle. Remove the mid-span tie rod and the part of the steel pipe pile supports above the tie rod; S7. Remove all remaining crossbeams and end tie rods; S8. Remove the steel pipe pile supports and the substructure at both ends of the arch bridge.

2. The construction method for dismantling tie-arch bridges with fewer supports as described in claim 1, characterized in that, The steel pipe pile support includes four steel pipe columns arranged along the apex of a square. Two steel pipe columns are located outside the tie rod, and the other two steel pipe columns are located inside the tie rod and pass upward through the bridge deck at the corresponding position. The distribution beam is connected between the two steel pipe columns in the transverse direction of the bridge. The steel pipe pile support provides support to the tie rod through the two lower distribution beams and to the arch rib through the two upper distribution beams. A support frame is connected between the bottom of the distribution beam and the steel pipe column. Connecting rods are also connected between the steel pipe columns. The construction of the steel pipe pile support in step S2 includes the following steps: A1. Before setting up the steel pipe pile support, a piece of the bridge deck at the corresponding position is removed or cut in advance; A2. Install all steel pipe columns, with the steel pipe columns continuing upward in segments. The segment length of the steel pipe column is less than the distance between the arch rib at the corresponding position and the tie rod below. Connecting rods are welded on the steel pipe columns. A3. Weld the distribution beams to the bottom of the tie rod and the bottom of the arch rib on the steel pipe column respectively, to ensure that the distribution beams are in full contact with the bottom of the tie rod and the bottom of the arch rib. A4. Weld a support frame between the bottom of the distribution beam and the steel pipe column.

3. The construction method for dismantling tie-arch bridges with fewer supports as described in claim 2, characterized in that, The two support positions are arranged at the vertical positions where the side wind braces are located on both sides.

4. The construction method for dismantling tie-arch bridges with fewer supports as described in claim 2, characterized in that, When installing the steel pipe pile support, if there is a gap between the tie rod or the arch rib and the corresponding distribution beam, it can be filled by setting thin iron sheets.

5. The construction method for dismantling tie-arch bridges with fewer supports as described in claim 2, characterized in that, After the steel pipe pile support is installed, a crash bar is installed on the outside of each steel pipe pile support.

6. The construction method for dismantling tie-arch bridges with fewer supports as described in claim 2, characterized in that, The lower layer of the distribution beam passes horizontally through the two correspondingly connected steel pipe columns. The top of the steel pipe column has a groove extending downwards along the transverse direction corresponding to the distribution beam. The upper layer of the distribution beam is embedded and fixed in a pair of grooves located in the transverse direction. The two ends of the upper and lower layer of the distribution beam extend to the outside of the steel pipe column, respectively.

7. The construction method for dismantling tie-arch bridges with fewer supports as described in claim 2, characterized in that, The arch rib is divided into five sections, which are a central arch rib, two side arch ribs, and two end arch ribs. The central arch rib is connected to the central wind brace, and the side arch ribs are connected to the side wind brace.

8. The construction method for dismantling tie-arch bridges with fewer supports as described in claim 7, characterized in that, The two ends of the two distribution beams on the upper layer of the steel pipe pile support extend to the outer side of the steel pipe column, forming an extension. When removing the side arch rib, a pulley guide device is installed at the distribution beam on the upper layer of the steel pipe pile support. The pulley guide device includes: a bearing seat with a bearing at its center, the bearing seat being sleeved and connected to the two extensions of the higher distribution beam; a rotating arm, one end of which is fixedly connected to the bearing seat and extends radially along the corresponding distribution beam; a telescopic arm, which is arranged in the transverse direction and has a fixed end and a telescopic end, wherein the fixed end is fixedly connected to the other end of the rotating arm, and the telescopic end faces the arch rib; a clamping plate, which is fixed to the telescopic end of the telescopic arm, and the side of the clamping plate facing the arch rib is used to fit tightly against the arch rib; a receiver, which includes a base frame, one end of which is fixedly connected to the extension of the lower distribution beam, and the other end is fixedly connected to the steel pipe column below the higher distribution beam. A telescopic airbag is fixed to one side of the distribution beam at a higher position. The upper end of the telescopic airbag is connected to the rotating arm. An electric air pump is also fixed on the base frame and is connected to the telescopic airbag to control its volume. The rotating arm is positioned above the side arch rib above the lower distribution beam. Before cutting the side arch rib, the telescopic arms on both sides are extended toward the side arch rib until the two clamping plates clamp the side arch rib. The arch bridge is then dismantled by a floating crane. After cutting the side arch rib and connecting it to the side arch rib by the floating crane, the posture of the side arch rib is adjusted, raising the lower end of the side arch rib. Under the action of the clamping plates on both sides, the rib rotates around the bearing. After adjustment, the telescopic airbag is inflated by an electric air pump. The telescopic airbag supports the rotating arm, and then the telescopic arm is driven to retract, releasing the clamping of the side arch rib. The floating crane removes the side arch rib, the telescopic airbag is deflated, and the rotating arm is placed on the base frame. It is then moved along with the dismantling of the portion of the steel pipe pile support above the tie rod.

9. The construction method for dismantling tie-arch bridges with fewer supports as described in claim 7, characterized in that, A construction passage is provided at the top of the arch rib. The construction passage includes scaffolding structures spaced apart along the extension direction of the arch rib. Each scaffolding structure includes two uprights and two horizontal bars fixed to the arch rib on its four sides. Adjacent uprights and horizontal bars are welded together. The two ends of the two horizontal bars of each scaffolding structure extend outwards. The ends of the upper and lower horizontal bars on the same side are vertically connected to edge protection pipes. The top of the edge protection pipes is higher than the top of the corresponding cross-section of the arch rib. In the extension direction of the arch rib, the upper ends of adjacent edge protection pipes are connected in sequence with protective netting. Walking boards are laid and connected between the upper horizontal bars. Construction workers use the construction passage to cut and lift the arch rib.

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