Construction method of large-span steel structure arch bridge

Abstract

The invention discloses a construction method of a large-span steel structure arch bridge. The construction method comprises the following steps in sequence: S1, foundation construction; s2, mounting a near-shore steel structure: sequentially mounting a near-shore cross beam section, an arched beam combined section, a near-shore main beam section and a side section arch rib section in a sliding and hoisting combined manner; s3, building a midspan system: building a lifting bracket and a middle bearing platform, placing two ends of at least one middle main longitudinal beam on a sliding platform, mounting at least one middle main cross beam on the middle main longitudinal beam to form the middle bearing platform, and erecting an arch rib support frame on the middle bearing platform; s4, middle-section arch rib folding: middle-section arch rib sections are hoisted on arch rib supporting frames and assembled into a middle-section arch rib structure, the middle-section arch rib structure is lifted to a designed position through lifting equipment, and folding construction is carried out; and S5, construction of an accessory structure. The problems of high safety risk, long construction period, high cost and poor installation precision in steel structure arch bridge construction are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge construction, and in particular to a construction method of a steel structure arch bridge. Background Art

[0002] Steel arch bridges do not have piers. The bridge deck is suspended by cables on the arch ribs. They have strong spanning capacity and do not affect navigation. Therefore, they are widely used in the construction of cross-river bridges.

[0003] At present, a common method for the construction of large-span steel arch bridges across rivers is to first use a large floating crane to install the steel arch ribs. After the arch ribs are erected, the longitudinal beams (main beams of the steel structure bridge) and cross beams are hoisted by a floating crane; or the arch ribs are first installed by the lifting method, and then the main beams and cross beams are installed by a floating crane. Both methods have the disadvantages of great difficulty in hoisting, high safety risks, insufficient positioning accuracy, and long construction period. In addition, the construction is difficult and costly. Large floating cranes are easily restricted by the water level of the river during the dry season, and the construction period cannot be guaranteed. In addition, when constructing steel box arch bridges, due to the great difficulties in using large steel components, the method of prefabrication in sections and assembly on site is often used. However, due to the large length and large number of steel segments, the structural force and linear control during the assembly process are more complicated, and the construction is more easily affected by environmental factors, resulting in problems such as the arch ribs cannot be connected and the linearity cannot meet the design goals. Summary of the Invention

[0004] In view of the defects of the above existing technologies, the present invention provides a construction method for a large-span steel arch bridge to solve the problems of high safety risks, long construction period, high cost, and installation accuracy in the construction of traditional steel arch bridges.

[0005] The present invention is achieved by adopting the following technical solutions: A construction method for a long-span steel arch bridge comprises the following steps: S1. Foundation construction: including permanent piers, a water-based work platform, an assembly platform, and a sliding platform connecting the water-based work platform and the assembly platform, with a sliding mechanism on the sliding platform; S2. Installation of nearshore steel structure: Install nearshore cross beam segments, arch-beam joint segments, nearshore main beam segments, and side arch rib segments in sequence through a combination of sliding and hoisting methods; S3. Construction of the mid-span system: This includes the construction of a lifting support and a central load-bearing platform, with the lifting support supported by the piers of the old bridge. The central load-bearing platform is constructed by first placing both ends of at least one central main longitudinal beam on a sliding platform, then installing at least one central main transverse beam on the central main longitudinal beam to form the central load-bearing platform, and then erecting the arch rib support frame on the central load-bearing platform. S4. Closing of the middle arch rib: The middle arch rib segment is hoisted on the arch rib support frame, and then the middle arch rib wind bracing and the lifting arch rib are welded to form the middle arch rib. After that, the middle arch rib is lifted to the designed position by the lifting equipment of the lifting frame, and the constructed side arch ribs are closed with the middle arch ribs; S5. Construction of auxiliary structures: This includes the installation of suspenders, mid-span beams, and cantilever beams, and the gradual removal of lifting supports, old piers, arch rib supports, sliding platforms, assembly platforms, and water work platforms.

[0006] Furthermore, in step S4, the stabilizing cables connecting the lifting supports on both sides are tensioned and pre-tightened, the tensioning steel strands of the lifting section arch ribs are connected, the lifting steel strands between the lifting equipment and the lifting section arch ribs are connected, and then the middle section arch ribs are lifted to a preset height away from the arch rib support frame and then stationary, the patched main longitudinal beam segments are hoisted, the patched main longitudinal beam segments are welded to the middle section main longitudinal beam (50) to form a continuous structure, and then the middle section arch ribs are lifted again to be closed.

[0007] Furthermore, in step S4, before the middle arch rib is lifted, an initial pre-tightening force is applied to the tensioning steel strands and the lifting steel strands respectively, and then pre-tightening force is applied alternately to the tensioning steel strands and the lifting steel strands according to a predetermined plurality of increasing pre-tightening force levels until the final pre-tightening force target value is reached.

[0008] Furthermore, in step S4, the initial preload force is 30%-50% of the final preload force target value, and the multiple increasing preload force levels include four levels, namely 40%, 70%, 90% and 100% of the final preload force target value.

[0009] Furthermore, in step S4, the lifting section arch rib is lifted and positioned to the designed position through the multi-lifting point synchronous lifting system, and the closing arch rib segment is embedded between the lifting section arch rib and the constructed side section arch rib segment using lifting equipment to carry out closing construction. After the closing is completed, the tensioning steel strands of the middle section arch rib are first unloaded, and then the tension of the lifting steel strands is unloaded step by step. After the lifting force is released, the initial tensioning of the hanger is carried out.

[0010] Furthermore, the installation method of the nearshore cross beam segment and the arch beam combined segment is: Using the lifting equipment and the sliding mechanism, for each of the plurality of nearshore beam segments, the following operations are performed: hoisting the segment from the water transport equipment onto the sliding mechanism, driving the segment to move to the shore side to the transfer position by the sliding mechanism, and then transferring the segment to a temporary storage area by the lifting equipment; Subsequently, the arch-beam joint segment is hoisted from the water transport equipment to the sliding mechanism using a lifting device and a sliding mechanism. The sliding mechanism drives the segment to move to the shore to the transfer position. The segment is then positioned on the assembly platform by a lifting device and its posture is adjusted. Afterwards, multiple temporarily stored nearshore beam segments are hoisted to the designed positions in a predetermined sequence using lifting equipment; Wherein, the installation method is performed symmetrically on both sides of the bridge.

[0011] Furthermore, the installation method of the nearshore main beam segment is as follows: (a) For each of the plurality of nearshore girder segments, perform the following operations: Transfer it from the water transport equipment to the skidding mechanism through a lifting system; Driven by the sliding mechanism, the vehicle moves toward the shore to a position close to the design position; Using the three-dimensional positioning system of the sliding mechanism to adjust its spatial posture; Transferring the load from the sliding mechanism to a temporary support frame of the sliding platform; (b) repeating operation (a) in a preset sequence to complete the installation of multiple nearshore main beam segments; (c) Perform operations (a) to (b) symmetrically on both sides of the bridge.

[0012] Furthermore, the installation method of the side arch rib segment is as follows: Perform the following actions symmetrically on both sides of the bridge: (a) installing multiple sets of first arch rib brackets on the shore-side main beam structure and multiple sets of second arch rib brackets on the water-side main beam structure; (b) supplying the arch rib segments of the nearshore side section and the arch rib segments of the waterside section by means of water transport equipment; (c) Performing graded lifting operations using lifting equipment: After hoisting the arch rib segments of the nearshore side section to the water operation platform for temporary storage, adjust the position of the lifting equipment and hoist them in sequence to the designed position of the first arch rib support; After hoisting the arch rib segment of the near-water side section to the water working platform for temporary storage, adjust the position of the lifting equipment and hoist it to the designed position of the second arch rib support; (d) Hoist the wind bracing segments to the temporary storage area on the installed structure, adjust the position of the lifting equipment, and then hoist them to the designed position; (e) Hoist the closed arch rib segments to a temporary storage area on the installed structure.

[0013] Furthermore, the installation method of the mid-span main beam is: (a) First, install several main beams near the shore and apply the first level of initial tension; (b) When the installation completion rate of the main beams on the nearshore side reaches the preset ratio, the remaining main beams in the mid-span will be hoisted simultaneously.

[0014] Furthermore, the installation of the cantilever beam includes the installation of the nearshore cantilever beam and the installation of the mid-span cantilever beam. The installation of the nearshore cantilever beam is carried out on an above-water working platform using lifting equipment and is installed into place together with the nearshore main beam segment. The installation of the mid-span cantilever beam is directly lifted into place using the floating lifting equipment used when installing the middle section main longitudinal beam.

[0015] Compared with the prior art, the beneficial effects of the present invention include at least: (1) By utilizing the old bridge piers left behind when the old bridge was demolished, the lifting brackets were built after the top surface of the old bridge piers was processed. After all the arch ribs were welded and fixed, the lifting brackets and the old bridge piers were completely removed. Compared with the traditional lifting bracket setup, the old bridge piers were fully utilized, and there was no need to pile and build temporary support columns in the middle of the river, which greatly saved construction costs and shortened the construction period.

[0016] (2) The nearshore structure of the present invention is installed by sliding and hoisting methods, which significantly reduces the impact on the environment and waterways. Since the sliding process is carried out above the water surface or close to the shore, the interference with deep water areas, busy waterways or sensitive aquatic ecological environments (such as fish migration and wetlands) is greatly reduced. During the construction process, there is basically no need to block the waterway or only a short-term partial blockade is required. The hoisting operation can be completed in a short time (such as taking advantage of the night navigation interval), with little impact on shipping, reducing the time and scope of water operations. Sliding only requires the construction of a water operation platform at the starting point, and hoisting only requires hoisting equipment (such as a large crawler crane or a truck crane). Compared with the overall rental cost of traditional massive support frame materials or large floating cranes, the cost and construction period of temporary projects are usually significantly reduced. At the same time, the time of water construction can be shortened, the rental time of expensive large water equipment can be reduced, and the cost of ship operation can be reduced.

[0017] (3) The middle section main longitudinal beam is first placed on the upper sliding platform in a simply supported state, which can effectively release the internal stress of the middle section main longitudinal beam during the construction phase and reduce the risk of structural deformation. Moreover, after the intermediate load is released, the middle section main longitudinal beam rebounds to the original design state and then connects to the nearshore main structure, effectively ensuring the bridge line shape. Since the sliding platform can provide horizontal constraints and controllable displacement capabilities, it ensures the stability of the beam under the assembly load and provides a solid and anti-overturning foundation for the assembly of the middle section arch rib. The middle section main longitudinal beam and main cross beam work together to form a permanent structural load-bearing platform, directly replacing independent large temporary supports and reducing the amount of auxiliary structure erection and dismantling work.

[0018] (4) When the middle arch rib is assembled on the middle main longitudinal beam, the load is directly transferred to the foundation through the sliding bracket, eliminating the risk of stress concentration caused by the middle main longitudinal beam not being closed, and preventing weld cracking or local buckling from the root; since the middle main longitudinal beam itself is a stable, flat platform at the height of the bridge deck, it provides an ideal working surface for on-site assembly, welding, and testing of the middle arch rib, providing a relatively stable, spacious and safe high-altitude working platform for construction personnel, saving the time and cost of setting up a special operating platform. In addition, the use of the middle main longitudinal beam system as a support usually has better rigidity and stability than independent temporary brackets, reducing the high-risk operation of erecting and dismantling large temporary support structures at high altitude, on water or in complex terrain conditions, while reducing the space occupied by the river. During construction, navigation can still be maintained under the middle main longitudinal beam. Since the middle arch rib can be directly hoisted to the predetermined position on the main longitudinal beam for precise adjustment and docking, the erection and dismantling time of large-scale temporary facilities is avoided, the coordination difficulty is reduced, and the overall construction period of the arch rib installation stage can be significantly shortened. The middle main longitudinal beam itself usually has good straightness or a set curve line shape. As the basis for fixing the arch rib segments, it helps to control the assembly accuracy of the entire arch rib and the final bridge line shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is one of the schematic diagrams of a long-span steel arch bridge according to an embodiment of the present invention; Figure 2 is a top view of a large-span steel arch bridge according to an embodiment of the present invention; Figure 3 1 is a left side view of a large-span steel arch bridge according to an embodiment of the present invention; Figure 4 This is one of the schematic diagrams of the foundation construction of an embodiment of the present invention; Figure 5 This is the second schematic diagram of the foundation construction of an embodiment of the present invention; Figure 6 This is the third schematic diagram of the foundation construction of an embodiment of the present invention; Figure 7 This is one of the schematic diagrams for installing a nearshore beam segment according to an embodiment of the present invention; Figure 8 This is the second schematic diagram of the installation of the nearshore beam segment according to an embodiment of the present invention; Figure 9 This is one of the installation diagrams of the arch-beam combination segment according to an embodiment of the present invention; Figure 10 This is the second installation diagram of the arch-beam combination segment according to an embodiment of the present invention; Figure 11 This is the third installation diagram of the arch-beam combination segment according to an embodiment of the present invention; Figure 12This is the fourth installation diagram of the arch-beam combination segment according to an embodiment of the present invention; Figure 13 This is one of the schematic diagrams for installing the nearshore main beam segment according to an embodiment of the present invention; Figure 14 This is the second schematic diagram of the installation of the nearshore main beam segment according to an embodiment of the present invention; Figure 15 This is one of the schematic diagrams for installing the side arch rib segments according to an embodiment of the present invention; Figure 16 This is the second installation diagram of the side arch rib segment according to an embodiment of the present invention; Figure 17 This is the third installation diagram of the side arch rib segment according to an embodiment of the present invention; Figure 18 This is the fourth installation diagram of the side arch rib segment according to an embodiment of the present invention; Figure 19 This is the fifth installation diagram of the side arch rib segment according to the embodiment of the present invention; Figure 20 This is the sixth installation diagram of the side arch rib segment according to an embodiment of the present invention; Figure 21 This is the seventh schematic diagram of the installation of the side arch rib segment according to the embodiment of the present invention; Figure 22 This is the eighth schematic diagram of the installation of the side arch rib segment according to the embodiment of the present invention; Figure 23 This is one of the schematic diagrams of establishing a cross-center system according to an embodiment of the present invention; Figure 24 This is the second schematic diagram of the cross-center system construction according to an embodiment of the present invention; Figure 25 This is the third schematic diagram of the cross-center system construction according to an embodiment of the present invention; Figure 26 This is the fourth schematic diagram of the cross-center system construction according to an embodiment of the present invention; Figure 27 This is one of the schematic diagrams of the middle arch ribs being closed in accordance with an embodiment of the present invention; Figure 28 This is the second schematic diagram of the middle arch rib folding in the embodiment of the present invention; Figure 29 This is the third schematic diagram of the middle arch rib folding in the embodiment of the present invention; Figure 30 This is the fourth schematic diagram of the middle arch rib folding in the embodiment of the present invention; Figure 31 This is the fifth schematic diagram of the middle arch rib folding in the embodiment of the present invention; Figure 32 This is the sixth schematic diagram of the middle arch rib folding in the embodiment of the present invention; Figure 33 This is the seventh schematic diagram of the middle arch rib folding in the embodiment of the present invention; Figure 34 This is the eighth schematic diagram of the middle arch rib folding in the embodiment of the present invention; Figure 35 This is one of the installation diagrams of the auxiliary structure of an embodiment of the present invention; Figure 36 This is the second installation diagram of the auxiliary structure of the embodiment of the present invention; Figure 37 This is the third installation diagram of the auxiliary structure of the embodiment of the present invention; Figure: 1. Permanent bridge pier; 21. Assembly platform; 22. Sliding platform; 23. Slipway trolley; 3. Water working platform; 4. Arch rib support; 5. Lifting support; 51. Stabilizing cable; 52. Lifting steel strand; 6. Old bridge pier; 7. Crash pier; 8. Lifting equipment; 9. Arch rib support frame; 101. End beam DL2 segment; 201. Arch foot main longitudinal beam GJ1 segment; 202. Arch foot and arch beam combined GJ2 segment; 30. Nearshore Main beam segment; 40. Side arch rib segment; 41. Side arch rib GL1 segment; 42. Side arch rib GL2 segment; 43. Side arch rib wind bracing FC3 segment; 44. Side arch rib GL3 segment; 45. Arch rib closing segment; 46. Side arch rib wind bracing FC2 segment; 50. Middle section main longitudinal beam; 51. Middle section main transverse beam; 60. Middle section arch rib; 61. Lifting section arch rib; 62. Tension steel strands; 70. Hanger; 80. Cantilever beam. DETAILED DESCRIPTION

[0020] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concepts of the example embodiments to those skilled in the art. Identical reference numerals in the drawings represent identical or similar structures, and thus repeated descriptions thereof will be omitted.

[0021] The words expressing positions and directions described in the present invention are all explained with reference to the accompanying drawings as examples, but can be modified as needed, and all such modifications are within the scope of protection of the present invention.

[0022] This steel arch bridge, based on a major bridge project, is described. The main span of this bridge is a through-type steel box-type tied arch bridge with a main span of 215 meters. The standard width of the main bridge is 47 meters, and the total length is 222 meters. The bridge comprises a main girder structure, arch ribs, arch feet, crossbeams, wind bracing, and cantilever structures. The main girder is a steel-concrete composite beam structure, with a total deck width of 47 meters. The standard section main longitudinal beam is 4 meters high, and the deck has a 2.0% transverse slope in both directions. The main girder is a double-girder system consisting of a main longitudinal beam (a closed-side box beam), a middle crossbeam, end crossbeams, secondary end crossbeams, and small longitudinal beams. The longitudinal beams are segmented every 7.2 meters, with crossbeams spaced every 3.6 meters. Three small longitudinal beams are located between every two crossbeams. The standard section composite beam is made of Q345qD steel, while the arch-beam junction is made of Q420qD steel.

[0023] The bridge features two parallelogram-shaped main longitudinal beams, with a center-to-center distance of 37.06m. The standard section has a beam height of 4m, and the arch footings range from 4m to 5.45m. The top plate of the standard section is 2.56m wide and 24mm thick, while the bottom plate is 2.55m wide and 22mm thick. 16mm-thick diaphragms are installed every 3.6m, corresponding to the crossbeam positions. The diaphragms are 36mm thick at the suspension points, and 12mm thick at non-crossbeam locations. The intermediate section consists of two main longitudinal beams, measuring 81m x 2.5m.

[0024] The arch ribs are steel box arches with a calculated span of 215m, a rise of 49m on the arch slope, and a rise-to-span ratio of 1 / 4.39. The two arch ribs are inclined 11° inward, and the arch axis follows a quadratic parabola. The arch ribs are fully welded rectangular sections, arranged at equal heights, with a 4m high and 2.5m wide arch ribs. The arch top wind bracing utilizes a "straight" structure with a trapezoidal steel box cross-section. The standard arch rib sections are made of Q345qD and Q420qD materials, while the arch-beam junction section utilizes Q420qD. The intermediate arch rib consists of a single piece, measuring 55.24m by 22m.

[0025] The bridge is equipped with six straight-line wind braces with a trapezoidal cross-section. The arch wind braces are constructed of steel, made of Q345qD. The F1 and F2 wind braces have top and bottom plates 25mm thick, webs 25mm thick, and stiffeners 18mm thick. The F3 wind brace has top and bottom plates 28mm thick, webs 28mm thick, and stiffeners 20mm thick. All members are welded together, and all plates are aligned using the outer surface alignment method.

[0026] This invention divides the structure into segments based on the main bridge's structural form and on-site construction methods. The segmentation is symmetrically arranged in the north and south directions, primarily into main beam sliding segments, intermediate main longitudinal beams, side arch rib segments, and intermediate arch ribs. The overall construction sequence is to construct the main beam first, then the arch ribs, and finally the cantilever beam 80 structure, starting with the south bank, then the north bank, and finally the middle. After completion and acceptance, the structure is shipped according to site requirements.

[0027] like Figures 1 to 37 As shown, a construction method of a large-span steel arch bridge provided by the present invention includes the following steps in sequence: S1 foundation construction: including a permanent pier 1, a water working platform 3, an assembly platform 21 and a sliding platform 22 connecting the water working platform 3 and the assembly platform 21, the sliding platform 22 is provided with a sliding mechanism; S2. Installation of the nearshore steel structure: The nearshore cross beam segment, arch-beam joint segment, nearshore main beam segment 30, and side arch rib segment 40 are sequentially installed through a combination of sliding and hoisting; S3. Construction of the mid-span system: This includes the construction of the lifting support 5 and the central load-bearing platform, wherein the lifting support 5 is supported by the old piers 6 retained from the old bridge. The central load-bearing platform is constructed by first placing both ends of at least one central main longitudinal beam 50 on the sliding platform 22, then installing at least one central main transverse beam 51 on the central main longitudinal beam 50 to form the central load-bearing platform, and then erecting the arch rib support frame 9 on the central load-bearing platform. S4. Closing of the middle arch rib 60: The middle arch rib segment is hoisted on the arch rib support frame 9, and then the middle arch rib wind bracing and the lifting arch rib 61 are welded to form the middle arch rib 60. After that, the middle arch rib 60 is lifted to the designed position by the lifting equipment of the lifting bracket 5, and the constructed side arch ribs are closed with the middle arch rib 60; S5. Construction of auxiliary structures: This includes the installation of suspenders 70, mid-span main beams, and cantilever beams 80, and the gradual removal of lifting brackets 5, old bridge piers 6, arch rib support frames 9, sliding platforms 22, assembly platforms 21, and water work platforms 3.

[0028] In step 1, the longitudinal beams of the assembly platform 21 are connected to the permanent bridge pier 1. The water-based work platform 3 is preferably a steel trestle. The sliding platform 22 includes a sliding bracket and a sliding track located on top of the sliding bracket. The sliding mechanism is preferably a slipway trolley 23, which is configured to slide the steel segment components from the far-shore end of the sliding bracket to the near-shore end. Specifically, the slipway trolley 23 uses a computer-controlled synchronous drive system during translation. The servo motor transmission acceleration is extremely small and controllable, effectively ensuring the stability and safety of the entire installation process. The slipway trolley 23 has strong maneuverability, is easy to transport and install, has bidirectional travel capability, and has a small horizontal load during translation. The hydraulic bearing system of the slipway trolley 23 can adjust the position of the components, and the component installation accuracy and quality can be controlled.

[0029] The present invention utilizes a synchronous translational construction process using a trolley 23. The trolleys are controlled by a PLC system that synchronizes the operation of the trolley drive motors and hydraulic systems. The trolley 23 is an automated device that integrates electrical, hydraulic, and mechanical systems. The hydraulic load-bearing system and drive travel system are controlled by a computer.

[0030] In the above technical solution, given the busy waterway and a river width of approximately 200m, at the beginning of construction, the old bridge piers 6 were retained to support temporary measures (lifting brackets 5) during the construction of the new bridge, so as not to affect navigation. This greatly reduced the investment in temporary measures. The old bridge piers 6 were connected to the bottom of the lifting brackets 5 by planting steel bars, improving the lifting brackets 5's ability to resist overturning. By utilizing the old bridge piers 6, which were deliberately left behind when the old bridge was demolished, as the support base for the lifting brackets 5, the lifting brackets 5 were constructed after the top surface of the old bridge piers 6 was treated. After all the arch ribs were welded and fixed, the lifting brackets 5 and the old bridge piers 6 were completely removed. Compared with the traditional lifting bracket setup, the old bridge piers 6 were fully utilized, eliminating the need to pile temporary support columns in the middle of the river, greatly saving construction costs and shortening the construction period.

[0031] In the above technical solution, the nearshore steel structure is mainly installed by combining sliding and hoisting. The lifting equipment 8 of the water working platform 3 lifts the steel segment components on the flatbed ship to the sliding mechanism of the sliding platform 22, and slides it from the water to the shore with the help of the sliding mechanism. The lifting equipment 8 changes its position and hoists the steel segment components on the sliding mechanism to the designed position. Compared with the traditional large-scale support method or floating crane integral hoisting method, the nearshore structure of the present invention adopts the sliding method and hoisting method for installation, which has the following advantages: (1) Significantly reduce the impact on the environment and waterways: Since the sliding process takes place above the water surface or close to the shore, the interference with deep water areas, busy waterways or sensitive aquatic ecological environments (such as fish migration and wetlands) is greatly reduced. During the construction process, there is basically no need to block the waterway or only a short-term partial blockade is required. The lifting operation can be completed in a short time (such as taking advantage of the night navigation interval), with little impact on shipping, reducing the time and scope of water operations.

[0032] (2) Improve construction safety: The assembly work is carried out on a relatively safe and stable ground or platform (water operation platform 3 or assembly platform 21), which greatly reduces the risk of workers working in deep water or at high altitude for a long time.

[0033] (3) Strong controllability: The sliding and lifting processes are controllable and carried out step by step, making it easier to implement process monitoring and safety control.

[0034] (4) Improved construction economy: Sliding only requires the construction of a water-based working platform 3 at the starting point, and lifting only requires lifting equipment (such as a large crawler crane or truck crane). Compared with the traditional large-scale support frame materials or the overall rental cost of a large floating crane, the cost and construction period of temporary projects are usually significantly reduced. At the same time, it can shorten the time for water-based construction, reduce the rental time of expensive large-scale water-based equipment (floating cranes, barges), and reduce the cost of ship operation.

[0035] (5) Improve construction efficiency and controllability of construction period: The sliding method allows the bridge structure to slide while the next section is assembled. The sections of the hoisting method can be prefabricated in parallel at multiple sites in the factory or on the shore, greatly shortening the total construction period on site.

[0036] (6) Strong site adaptability: Suitable for situations where the construction site is limited, the shore space is narrow, or the underwater foundation is complex (such as deep water and soft foundation).

[0037] In the above technical solution, the present invention places at least one middle main longitudinal beam 50 at both ends on the sliding platform 22, placing it in a simply supported state (allowing the component to rotate freely at the support, but restricting its movement in a direction perpendicular to the support surface). The middle main longitudinal beam 50 is also supported by the main cross beam to form a middle bearing platform. Finally, an arch rib support frame 9 is set up on the middle bearing platform to assemble the middle arch rib 60. This has the following advantages: The middle main longitudinal beam 50 is initially placed on the upper sliding platform 22 in a simply supported state. This effectively releases internal stress during the construction phase of the middle main longitudinal beam 50 and reduces the risk of structural deformation. Because the sliding platform 22 provides horizontal constraints and controllable displacement, it ensures the stability of the beam under assembly loads, providing a solid, anti-overturning foundation for the assembly of the middle arch ribs 60. The middle main longitudinal beam 50 and the main cross beams work together to form a permanent structural load-bearing platform (central bearing platform), directly replacing independent large temporary supports and reducing the amount of auxiliary structure erection and dismantling work. The arch rib support frame 9 is erected on a stable bearing platform, providing a safe working surface and avoiding the high risks of scaffolding in complex terrain such as deep valleys and water bodies.

[0038] Using the middle main longitudinal beam 50 as a temporary support beam and assembly platform for the middle arch rib has the following advantages: When the middle arch rib 60 is assembled on the middle main longitudinal beam 50, the load is directly transferred to the foundation through the sliding bracket, eliminating the risk of stress concentration caused by the middle main longitudinal beam 50 not being closed, and preventing weld cracking or local buckling from the root; Because the middle main longitudinal beam 50 itself is a stable, flat platform located at bridge deck height, it provides an ideal working surface for on-site assembly, welding, and testing of the middle arch ribs 60. This provides construction workers with a relatively stable, spacious, and safe aerial work platform, eliminating the time and cost of setting up a dedicated operating platform. Furthermore, the use of the middle main longitudinal beam 50 system as a support generally offers superior rigidity and stability to independent temporary supports, reducing the high-risk tasks of erecting and dismantling large temporary support structures at high altitudes, over water, or in complex terrain. Because the middle arch ribs 60 can be directly hoisted to the predetermined position on the main longitudinal beam for precise adjustment and docking, the time required to erect and dismantle large-scale temporary facilities is avoided, coordination difficulties are reduced, and the overall construction period of the arch rib installation phase can be significantly shortened.

[0039] In addition, the middle main longitudinal beam 50 is located within the space occupied by the bridge structure itself, eliminating the need for, or significantly reducing the need for, large, high-strength temporary supports or full-height scaffolding under the bridge (such as in a river, a valley, or above a busy road). It does not occupy any additional valuable space under or around the bridge, making it particularly suitable for crossing sites with limited space, such as rivers, canyons, roads, or built-up areas. It also reduces the large amount of material investment in supporting steel pipes, Bailey plates, pile foundations, and the corresponding labor costs for installation and removal.

[0040] The middle main longitudinal beam 50 typically possesses excellent straightness or a predetermined curved shape. As the foundation for securing the arch rib segments, it helps control the accuracy of the entire arch rib assembly and the final bridge shape. The middle main longitudinal beam 50 is not only a crucial component of the final bridge structure, but also serves as a temporary support and platform during critical construction phases. This maximizes the load-bearing capacity and spatial location of the permanent structure, significantly reducing reliance on independent, costly temporary facilities.

[0041] As a preferred embodiment, in step S4, the stabilizing cable 51 connected to the lifting bracket 5 is tensioned and pre-tightened, the tensioning steel strands 62 of the lifting section arch rib 61 are connected, the lifting steel strands 52 between the lifting equipment and the lifting section arch rib 61 are connected, and then the middle arch rib 60 is lifted to a preset height away from the arch rib support frame 9 and then stationary, and then the patched main longitudinal beam segment is hoisted and welded to the middle main longitudinal beam 50 to form a continuous structure, and then the middle arch rib 60 is lifted and closed.

[0042] In this embodiment, after the middle arch rib segment is transported to the site by transport ship, the length of the steel wire rope is accurately calculated and set according to the setting of the lifting point. It is then hoisted to the middle load-bearing platform by an 800T floating crane and erected on the arch rib support frame 9. Then, the lifting section arch rib 61 and the middle arch rib wind brace are extended on the arch rib support frame 9. After the welding of the middle arch rib 60 is completed, the stabilizing cable 51 connected to the lifting bracket 5 is tensioned and pre-tightened. This makes the lifting bracket 5 more stable when it is subsequently subjected to loads and resists deformation and shaking. The tensioning steel strands 62 connected to the lifting section arch rib 61 allow the horizontal thrust generated by the middle arch rib 60 to be directly borne by the temporary tensioning steel strands 62, ensuring the integrity and stability of the arch rib during the lifting process and preventing the arch rib from displacement, tilting, etc. The lifting equipment (such as a jack, etc.) is a device used to lift the lifting section arch rib 61 to a specified position. The lifting device is connected to the lifting section arch rib 61 through the lifting steel strand 52. When the lifting device is working, the pulling force can be transmitted to the arch rib through the steel strand to realize the lifting operation of the arch rib.

[0043] In this solution, before the middle arch rib 60 is joined to the side arch ribs, it is first raised to a predetermined height and stationary, freeing it from the arch rib support frame 9. The middle main longitudinal beam 50 is then welded. Once the intermediate load is released, the middle main longitudinal beam 50 rebounds to its original design state and is then connected to the nearshore main structure, effectively maintaining the alignment of the completed bridge. This lifting of the middle arch rib 60 frees up workspace, allowing workers to weld the middle main longitudinal beam 50 in an unobstructed environment. The arch rib support frame 9 can then be removed after completing its support mission for the middle arch rib 60.

[0044] As a preferred embodiment, in step S4, before the middle arch rib 60 is lifted, an initial pre-tightening force is first applied to the tensioning steel strands 62 and the lifting steel strands 52 respectively, and then pre-tightening force is applied alternately to the tensioning steel strands 62 and the lifting steel strands 52 according to a predetermined plurality of increasing pre-tightening force levels until the final pre-tightening force target value is reached.

[0045] In this embodiment, before closing, an initial preload is applied to each of the tension strands 62 and the lifting strands 52. This initial preload provides initial tension to the strands, preparing them for subsequent application of preload and also eliminating any slack that may have occurred during installation. Preload is then applied alternately to the tension strands 62 and the lifting strands 52 according to a pre-set, increasing number of preload levels. For example, a first level of preload may be applied to the tension strands 62, followed by a first level of preload to the lifting strands 52, and then a higher level of preload to the tension strands 62. This cycle continues, gradually increasing the preload until the preload on both strands reaches a pre-set, final preload target value. This target value is determined based on factors such as the design requirements and load-bearing capacity of the mid-section arch rib 60, and analysis of the forces acting during the lifting process. Once the final preload target value is reached, the strands can provide stable and reliable tensile support for the lifting of the arch rib structure.

[0046] As a preferred embodiment, in step S4, the initial preload force is 30%-50% of the final preload force target value, and the multiple incremental preload force levels include four levels, namely 40%, 70%, 90% and 100% of the final preload force target value.

[0047] As a preferred embodiment, in step S4, the lifting section arch rib 61 is lifted and positioned to the designed position by a multi-lifting point synchronous lifting system, and the closing arch rib segment is embedded between the lifting section arch rib 61 and the constructed side section arch rib segment 40 by using a lifting equipment 8 to carry out closing construction. After the closing is completed, the tensioning steel strands 62 of the middle section arch rib 60 are first unloaded, and then the tension of the lifting steel strands 52 is unloaded step by step. After the lifting force is released, the initial tensioning of the hanger 70 is carried out.

[0048] In this embodiment, the arch section height is 10.4m, the span is 84.5m, and the lifting height is about 40m. The middle arch rib 60 is lifted to the designed elevation for closure through a multi-hanging point synchronous lifting system. The multi-hanging point synchronous lifting system can ensure that the arch rib is evenly stressed and rises steadily during the lifting process, avoiding tilting or shaking, and ensuring lifting accuracy. After the middle arch rib 60 is closed, the tensioning steel strands 62 of the middle arch rib 60 are first removed, and then the tension of the lifting steel strands 52 is unloaded step by step. The tension of the lifting steel strands 52 is gradually reduced in a certain order and steps, so that the middle arch rib 60 gradually adapts to its own stress state, avoiding structural deformation or damage due to sudden release of tension. After the lifting force is completely released, the suspender 70 is initially tensioned. The suspender 70 is an important component connecting the arch rib and the bridge deck. The initial tensioning can enable the suspender 70 to withstand a certain tension, providing necessary structural support for subsequent bridge deck construction and normal use of the bridge.

[0049] As a preferred embodiment, the installation method of the nearshore cross beam segment and the arch beam combined segment is: Using the lifting equipment 8 and the sliding mechanism, for each of the plurality of nearshore beam segments, the following operations are performed: hoisting it from the water transport equipment onto the sliding mechanism, driving it to move shoreward to the transfer position by the sliding mechanism, and then transferring it to the temporary storage area by the lifting equipment 8; Subsequently, the arch-beam combination segment is hoisted from the water transport equipment to the sliding mechanism using the lifting equipment 8 and the sliding mechanism, and is driven by the sliding mechanism to move to the shore side to the transfer position. Then, the arch-beam combination segment is positioned on the assembly platform 21 by the lifting equipment 8 and the posture is adjusted. Afterwards, the multiple temporarily stored nearshore beam segments are hoisted to the designed positions in a predetermined sequence by means of the lifting equipment 8; Wherein, the installation method is performed symmetrically on both sides of the bridge.

[0050] In this embodiment, by integrating the collaborative process of the sliding mechanism and the lifting equipment 8, the streamlined operation of the nearshore beam segments and the arch-beam combination segments is achieved: the nearshore beam segments adopt the batch pre-processing of "water lifting → sliding transportation → temporary storage", avoiding the frequent scheduling and idleness of the large lifting equipment 8, so that the installation of the arch-beam combination segments can be carried out simultaneously; the arch-beam combination segments are accurately positioned on the assembly platform 21 by the sliding mechanism and the posture is directly adjusted without the need for secondary transportation, which shortens the construction period by about 30% compared with the traditional step-by-step installation method.

[0051] The arch-beam combination segment is preferentially positioned and its posture adjusted, providing a rigid reference coordinate system for subsequent nearshore beam segments, overcoming the defect of cumulative error amplification during the simultaneous installation of multiple segments; the temporarily stored nearshore beam segments are hoisted according to a predetermined sequence, coordinated with the symmetrical construction on both sides of the bridge, balanced the main beam load distribution, and controlled the structural stress deviation within ±5% of the design value, greatly improving the installation accuracy and structural stability.

[0052] The sliding mechanism replaces high-altitude lifting on the water, reducing high-risk suspended operations; the near-shore beam segments are pre-processed in a temporary storage area on the shore, avoiding the interference of tides, wind and waves on direct installation on the water, reducing the accident rate, and significantly reducing construction safety risks.

[0053] In the above scheme, lifting equipment 8 is used only for fixed-point lifting (transfer location → storage area / assembly platform 21), improving equipment utilization. The sliding mechanism repeatedly drives multiple types of segments, allowing a single device to cover two phases of the task, reducing equipment investment costs and significantly optimizing resource utilization. Furthermore, in narrow nearshore or waterway-restricted areas, a "sliding transfer + temporary storage buffer" strategy is implemented: large components are divided into smaller segments for land transportation, overcoming the tonnage limitations of water transportation. The temporary storage area serves as an installation buffer, decoupling the strong temporal dependence of transportation and installation, ensuring construction continuity during flood season.

[0054] Traditional near-shore installation requires a large floating crane to be stationed for a long time, which is costly and restricted by hydrological conditions. The present invention transforms high-risk operations on water into controllable operations on land through a sliding mechanism shore-side transfer system, solving the problem of interference from tides, wind and waves on direct installation on water. As a preferred embodiment, the installation method of the nearshore main beam segment 30 is as follows: (a) For each of the plurality of nearshore main beam segments 30, perform the following operations: Transfer it from the water transport equipment to the skidding mechanism through a lifting system; Driven by the sliding mechanism, the vehicle moves toward the shore to a position close to the design position; Using the three-dimensional positioning system of the sliding mechanism to adjust its spatial posture; Transfer the load from the sliding mechanism to the temporary support frame of the sliding platform 22; (b) repeating operation (a) in a preset order to complete the installation of multiple nearshore main beam segments 30; (c) Perform operations (a) to (b) symmetrically on both sides of the bridge.

[0055] The method for installing the nearshore main beam segment 30 of this embodiment, through the dynamic transfer of the sliding mechanism and the closed-loop design of static load conversion, produces a breakthrough effect: The sliding mechanism's three-dimensional positioning system enables simultaneous fine-tuning of segment elevation, planar position, and inclination (with an accuracy of ±0.5mm), overcoming elevation errors caused by tidal fluctuations. During the load transfer process, temporary support frames evenly transmit stress (reducing stress concentration by 70%), preventing structural rebound deformation during unloading of the sliding mechanism. Compared to traditional direct lifting from water, which requires multiple recalibrations, this invention reduces posture adjustment time and significantly improves the installation and positioning qualification rate.

[0056] Through the cyclic reuse and sequential installation mechanism of the sliding mechanism, the "one-time positioning, continuous operation" mode of the sliding mechanism is utilized to save equipment reset time; batch installation is carried out in a preset sequence to achieve assembly line operation, and symmetrical execution on both sides of the bridge shortens the main beam closure period by 50%. This embodiment transfers the segment load from the sliding mechanism to the static support (temporary support frame), eliminating the risk of sudden breakage of the lifting rigging and solving the impact load problem when unloading large segments; workers do not need to operate on the shaking segments, reducing the exposure time of high-altitude operations and lowering the accident rate; the lifting system is only responsible for the short-distance transfer from "water to sliding mechanism", reducing equipment rental costs, and the three-dimensional adjustment and load conversion functions of the sliding mechanism are reused, reducing the investment in dedicated adjustment equipment and significantly reducing overall costs.

[0057] As a preferred embodiment, the installation method of the side rib segment 40 is as follows: Perform the following actions symmetrically on both sides of the bridge: (a) installing a plurality of first arch rib supports 4 on the shore-side main beam structure, and installing a plurality of second arch rib supports 4 on the water-side main beam structure; (b) supplying the nearshore side arch rib segments (including the side arch rib GL1 segment 41 and the side arch rib GL2 segment 42) and the waterside side arch rib segments (including the side arch rib GL3 segment 44, the side arch rib GL4 segment, and the side arch rib GL5 segment) by water transport equipment; (c) Performing staged lifting operations using lifting equipment 8: After the arch rib segments of the nearshore side section are hoisted to the water working platform 3 for temporary storage, the position of the lifting equipment 8 is adjusted and hoisted to the designed position of the first arch rib support 4 in sequence; After the arch rib segment of the near-water side section is hoisted to the water working platform 3 for temporary storage, the position of the lifting equipment 8 is adjusted and hoisted to the designed position of the second arch rib support 4; (d) Hoist the wind bracing segments (including the side arch rib wind bracing FC3 segment 43 and the side arch rib wind bracing FC2 segment 42) to the temporary storage area on the installed structure, adjust the lifting equipment to the 8-station position, and then hoist them to the designed position; (e) Hoisting and lowering the closed arch rib segments to a temporary storage area on the installed structure; The side arch rib installation method implemented by the present invention has the following significant effects: This embodiment adopts a buffer mechanism of staged hoisting operation + water working platform 3. Compared with traditional arch rib hoisting, which requires an ultra-large floating crane to be stationed in deep water, exposing personnel and equipment to the risk of wind and waves for a long time, the present invention uses the water working platform 3 as a temporary storage buffer zone, allowing the lifting equipment 8 to adjust its position in the nearshore stable area, keeping high-risk workers away from deep water. Staged hoisting realizes "single equipment multi-objective step-by-step operation" (arch rib → wind bracing → closure section), avoiding continuous operation of hoisting equipment in the surge area and ensuring construction safety. The main beam is anchored in advance by the first / second arch rib bracket, providing a positioning base for the arch rib segment. Symmetrical hoisting on both sides offsets the structural eccentricity caused by the unilateral construction load. Through the preset bracket system and segment classification supply, the arch rib-wind bracing modular flow operation is realized, shortening the single-span arch rib installation cycle.

[0058] The present invention utilizes a dynamic adjustment strategy for the eight positions of the lifting equipment, which is completed in stages: arch rib storage → position adjustment → arch rib installation → wind bracing transportation, thereby improving equipment utilization. Traditional water transport equipment supplies different types of segments in batches, decoupling the transportation and installation sequences, reducing the rental fees of large floating cranes, and lowering the equipment investment costs. By storing the closing section in the installed structure in advance, the temporary lifting of the closing mouth is avoided from being disturbed by wind and waves.

[0059] As a preferred embodiment, the installation method of the mid-span main beam is: (a) First, hoist several main beams near the shore and apply the first level of initial tension to the horizontal tie rods; (b) When the installation completion rate of the nearshore main beams reaches the preset ratio, the remaining main beams in the mid-span will be hoisted simultaneously; (c) After all mid-span main beams are installed, perform secondary tension adjustment on the horizontal tie rods to the target internal force value.

[0060] The invention's intelligent zoned installation of the mid-span main beam and closed-loop tensioning of the horizontal tie rods triggers the synchronous lifting of the mid-span main beams when the installation ratio of the near-shore main beams reaches 70%, shortening the critical path construction period (traditional linear installation requires waiting for 100% completion on the shore side). The secondary tensioning of the horizontal tie rods is completed synchronously with the installation of the main beams, eliminating the downtime of separate tensioning.

[0061] As a preferred embodiment, the installation of the cantilever beam 80 includes the installation of the nearshore cantilever beam 80 and the installation of the mid-span cantilever beam 80. The installation of the nearshore cantilever beam 80 is carried out on the water working platform 3 using the lifting equipment 8 and is installed into place together with the nearshore main beam segment 30. The installation of the mid-span cantilever beam 80 is directly lifted into place using the floating lifting equipment used when installing the middle section main longitudinal beam 50.

[0062] The nearshore cantilever beam 80 of the present invention is hoisted into place simultaneously with the main beam segment on the water working platform 3, eliminating the need for a separate hoisting process. The mid-span cantilever beam 80 is "incidentally hoisted" using the floating hoisting equipment of the middle main longitudinal beam 50 (no additional equipment needs to be dispatched), shortening the construction period of the cantilever beam 80; the nearshore cantilever beam 80 and the main beam segment are pre-assembled on the ground working platform to avoid high-altitude bolt tightening operations, and the mid-span cantilever beam 80 is hoisted using the existing floating crane route to avoid the risk of secondary ship repositioning and collision; the mid-span cantilever beam 80 reuses the main longitudinal beam floating crane, reducing the floating crane rental fee and lowering the comprehensive installation cost of the cantilever beam 80.

[0063] In the present invention, the nearshore cross beam segment includes a plurality of end cross beam segments (denoted by DL1-DL3) and a plurality of secondary end cross beam segments (denoted by CDL1-CDL3), the arch-beam junction segment includes an arch foot main longitudinal beam segment (GJ1) and an arch foot arch-beam junction segment (denoted by GJ2), the nearshore main beam segment 30 includes a plurality of main beam segments including cross beams (denoted by C1-C3 and B6-B10), the side arch rib segment 40 includes a side arch rib segment 40 (denoted by GL1-GL5), a side arch rib wind bracing segment (denoted by FC2-FC3), and a side arch rib closing segment (denoted by QB); The specific construction steps of the steel structure arch bridge of the present invention are as follows: (1) The steps for foundation construction are as follows: refer to Figure 4-Figure 6The steel trestle (water platform 3) and crash pier 7 were constructed using a "fishing method" using a truck crane. A 650t truck crane was used to construct the north and south bank assembly brackets (temporary support structure for assembly platform 21) and sliding brackets (temporary support structure for sliding platform 22) on the steel trestle and on the shore. Only the brackets below the main longitudinal beams were constructed on the two banks of the assembly brackets; the crossbeam assembly brackets were not constructed.

[0064] (2) Reference Figure 8-Figure 9 , the installation of the nearshore cross beam segment and the arch beam combination segment is as follows: Use a 650t truck crane on the steel trestle to lift the end beam DL2 segment 101 from the flatbed ship to the sliding support; The end cross beam DL2 segment 101 slides from the water toward the shore to the root of the sliding bracket.

[0065] The 650t truck crane transfers the end beam DL2 segment 101 from the sliding bracket to the assembly bracket.

[0066] The truck crane changes its position and transfers the end cross beam DL2 segment 101 to the shore for temporary storage on the ground several times. Repeat the above operation to complete the end cross beam DL1 segment, end cross beam DL3 segment and secondary end cross beams CDL1-CDL3 to the temporary storage area on shore for temporary storage.

[0067] Construction is symmetrical on the left and right sides of the north and south banks.

[0068] refer to Figure 10-12 , using a 650t truck crane on the steel trestle in a single-lift manner, the arch foot main longitudinal beam GJ1 segment 201 was lifted from the flatbed ship to the sliding bracket.

[0069] The arch foot main longitudinal beam GJ1 segment 201 slides from the water toward the shore to the root of the sliding bracket.

[0070] A 650t truck crane was used to transfer the arch foot main longitudinal beam GJ1 segment 201 from the sliding support to the top of the permanent pier 1, and a 150t positioning jack on the pier top was used to complete the beam segment posture adjustment.

[0071] Construction is symmetrical on the north and south banks.

[0072] A 650t truck crane was used to hoist the horizontally arranged arch foot and arch beam combined with the GJ2 segment 202 onto the sliding bracket from the flatbed ship in a single-lift manner on the steel trestle.

[0073] The arch foot and arch beam combined with the GJ2 segment 202 slide from the water toward the shore to the root of the sliding bracket.

[0074] A 650t truck crane was used to transport the arch foot and arch beam together with the GJ2 segment 202 to the ground, and then hoisted and transported to the designed position after completion of the turnaround.

[0075] After the arch foot and arch beam were hoisted together with GJ2 segment 202, the remaining structure of the arch foot assembly bracket was hoisted. The end beam and secondary end beam, which were originally stored on the shore, were hoisted to the designed position in the order of CDL2-CDL1-CDL3-DL2-DL1-DL3. The beam segment posture was adjusted using the 150t adjustment jack on the top of the sliding bracket.

[0076] Symmetrical construction on the left and right sides of the north and south banks (3) Reference Figure 13-14 , the installation steps of the nearshore main beam segment 30 are as follows: Two 650t truck cranes on the left and right sides are used to lift the main beam segment C3 including the cross beam from the flatbed ship to the sliding bracket.

[0077] The main beam segment C3 slides from the water toward the shore to a position close to the design position, and is lifted by a truck crane to the sliding bracket at the design position. The beam segment posture is adjusted through the adjustment function of the 150t three-way jack on the sliding bracket, and the force is transferred to the sliding bracket.

[0078] Repeat the above operations to perform sliding hoisting of main beam segment C3, where main beam segment C2 can be directly slid to the designed position. After sliding into place, the beam segment posture adjustment is completed through the adjustment function of the 150t three-way jack on the slipway trolley 23 and the force is transferred to the sliding support frame.

[0079] Repeat the above operations to complete the unloading and hoisting of main beam segments C1 and B10 into place. Segments B9-B7 are directly hoisted into place as main longitudinal beam and cross beam segments respectively. Segment B6 is used as the main beam patching segment. Only the main longitudinal beam segment is hoisted to the bridge deck near the shore for storage, and the corresponding cross beam is not installed.

[0080] Construction is symmetrical on the left and right sides of the north and south banks.

[0081] (4) Reference Figure 15-18 , the steps for installing the side arch rib segment 40 are as follows: Use a 650t truck crane to lift three sets of first arch rib supports on the nearshore side of the main beam.

[0082] The truck crane adopts a single-lift mode on the steel trestle to lift the side arch rib GL1 segment 41 from the flatbed ship and temporarily store it on the steel trestle.

[0083] The position of the mobile crane is changed, and the side arch rib GL1 segment 41 is transported by the mobile crane multiple times until it reaches the designed position. The above operations are repeated to complete the lifting of the side arch rib GL2 segment 42.

[0084] Construction is symmetrical on the left and right sides of the north and south banks.

[0085] Two truck cranes on the left and right sides of the steel trestle lifted the side arch rib wind bracing FC3 segment 43 from a flatbed barge and temporarily stored it on the bridge deck beam. FC3 can be placed directly on the arch rib support 4 pad beam. The truck cranes were repositioned and repeatedly moved until the side arch rib wind bracing FC3 segment 43 reached its designed position. Construction was carried out symmetrically on the north and south banks.

[0086] refer to Figure 19-20 , use a 650t truck crane to lift two sets of second arch rib supports on the nearshore side of the main beam close to the water.

[0087] A truck crane, using a single lift configuration, lifted side arch rib GL3 segment 44 and side arch rib GL4 from a flatbed ship and temporarily stored them on the steel trestle. The truck crane's position was changed, and secondary transport was performed until side arch rib GL3 segment 44 and side arch rib GL4 reached their designed locations. Construction was carried out symmetrically on both the north and south banks.

[0088] refer to Figure 21-22 A 650t truck crane, using a single lift configuration on the trestle, lifted the side arch rib GL5 segment from a flatbed barge and directly hoisted it into the designed position. The above operation was repeated to lift the arch rib closure segment 45 and temporarily store it on the bridge deck longitudinal beams. Construction was carried out symmetrically on the north and south banks. Two 650t truck cranes on the left and right sides of the steel trestle, using a lifting configuration, lifted the side arch rib wind bracing segment FC2 segment 46 from a flatbed barge and temporarily stored it on arch rib support 4. Construction was carried out symmetrically on the north and south banks.

[0089] refer to Figure 23 The steps to build the Kuazhong system are as follows: A 650t truck crane is used to install the lifting bracket 5 on the steel trestle, including the bracket bottom pad beam, steel columns, flat connection system and top distribution beam.

[0090] The construction is carried out symmetrically on the north and south banks. After the lifting support 5 is erected, the stabilizing cable 51 between the lifting support 5 and the ground anchor on the permanent pier 1 on the same side is connected. Figures 24-25 , an 800t floating crane hoisted the 84m middle section main longitudinal beam 50 in the upstream side span downstream of the channel, and the middle section main longitudinal beam 50 was placed on both ends of the sliding support in a simply supported state. 800t floating crane hoisted the 84m middle section main longitudinal beam 50 in the downstream side span downstream of the channel, and the middle section main longitudinal beam 50 was placed on both ends of the sliding support in a simply supported state. Figures 26-28 , 800t floating crane hoisting span 6 main cross beams, floating crane hoisting arch rib support frame 9 is on the middle main longitudinal beam 50; floating crane hoisting well-shaped middle arch rib 60 is on the arch rib support frame 9.

[0091] refer to Figures 29-30 The steps for closing the middle arch rib 60 are as follows: An 800t floating crane installed the arch rib 61 of the upstream lifting section, and then installed the arch rib 61 of the downstream lifting section on the same side. 650t truck cranes on both sides of the bridge installed the wind bracing of the lifting section. Construction was carried out symmetrically on the north and south banks. Figures 31-32 , connect the steel strand wind cables between the lifting supports 5 on both sides and pre-tighten them, and pre-tighten the stabilizing cables 51 between the lifting supports 5 and the permanent bridge. Connect the tensioning steel strands 62 between the lifting section arch ribs 61. Connect the lifting steel strands 52 between the lifting jacks (lifting equipment) and the lifting section arch ribs 61. After pre-tightening the tensioning steel strands 62 with 40% pre-tightening force, pre-tighten the lifting steel strands 52 with 40% pre-tightening force. Thus, the tensioning steel strands 62 and the lifting steel strands 52 are alternately pre-tightened according to the pre-tightening force values ​​of 40%, 70%, 90%, and 100%. After all the lifting section arch ribs 61 are 920cm away from the arch rib support frame, they are stationary. Hoist the patched main longitudinal beam segments stored on the nearshore side of the bridge deck into place, and weld the patched main longitudinal beam segments to the middle section main longitudinal beam 50. Install the main bridge's horizontal permanent tie rods.

[0092] refer to Figure 33 During the lifting process, the arch rib bracket 4 that interferes with the pulling steel strand 62 during the lifting process is cut off. The lifting section arch rib 61 is lifted to the designed position by the four-point synchronous lifting of the lifting bracket 5.

[0093] The closing arch rib segment 45 is hoisted by a 650t truck crane and inserted between the lifting section arch rib 61 and the constructed side section arch rib segment 40 to carry out the closing construction.

[0094] refer to Figures 34-35 After the arch ribs are closed, the horizontal tension of the arch ribs is completely released. The arch rib support 4 closest to the midspan is disengaged, and the connecting pads between the arch ribs and the arch rib support 4 are cut away, while the main structure of the arch rib support 4 remains. The internal force of the lifting steel strands 52 is gradually released (10% release in stages). After the lifting force is released, the tie rods are initially tensioned according to monitoring instructions. The remaining connecting pads between the arch rib support 4 and the arch ribs are removed, while the main structure of the support remains.

[0095] The construction steps of the auxiliary structure are as follows: Install the nearshore arch rib segment's hanger 70 from the shore toward the waterside, applying 30% initial tension. Install the nearshore bridge deck system from the shore toward the waterside, tensioning the hanger 70 to 65% of its initial tension. Remove lifting bracket 5. Use 650t truck-mounted cranes on both sides to lift the three sets of crossbeams that interfere with lifting bracket 5. Install the corresponding hanger 70 and tension them to 30% initial tension.

[0096] The remaining 23 beams of the main beam in the middle of the span were hoisted from the shore to the water side using a 300t small floating crane. The six groups of beams near the shore were installed with the corresponding hanger rods 70 and tensioned with 30%. When the fourth group of beams corresponding to hanger rods 70 near the shore were installed, the remaining 11 beams in the middle of the span were hoisted from the shore to the water side using a 300t small floating crane, with the construction being symmetrical on the north and south banks. After all beams were installed, the horizontal tie rods were tensioned a second time to an internal force of 2450kN. Figures 36-37 A 650t truck crane was used to install the cantilever beam 80° of the mid-span main girder on the steel trestle. The mid-span main girder corresponding to the bridge deck system was installed from the shore toward the waterside, with the corresponding hanger 70° tensioning 65% of the internal force. The bridge deck arch rib supports 4, the sliding supports, the assembly supports, and the steel trestle were gradually removed. Symmetrical construction was completed on the north and south banks.

[0097] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limiting the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the invention without departing from the principles and purpose of the present invention. All such changes shall fall within the scope of protection of the claims of the present invention.

Claims

1. A construction method for a long-span steel arch bridge, characterized in that: The following steps are involved: S1. Foundation construction: including permanent piers (1), an above-water working platform (3), an assembly platform (21), and a sliding platform (22) connecting the above-water working platform (3) and the assembly platform (21), wherein the sliding platform (22) is provided with a sliding mechanism; S2. Installation of the nearshore steel structure: The nearshore cross beam segment, the arch beam segment, the nearshore main beam segment (30) and the side arch rib segment (40) are sequentially installed by a combination of sliding and hoisting; S3. Construction of the mid-span system: including the construction of a lifting bracket (5) and a middle bearing platform, wherein the lifting bracket (5) is supported by the old piers (6) retained from the old bridge; the construction order of the middle bearing platform is to first place both ends of at least one middle main longitudinal beam (50) on the sliding platform (22), then install at least one middle main transverse beam (51) on the middle main longitudinal beam (50) to form a middle bearing platform, and set up an arch rib support frame (9) on the middle bearing platform; S4. Closing of the middle arch rib (60): The middle arch rib segment is hoisted on the arch rib support frame (9), and then the middle arch rib wind support and the lifting arch rib (61) are welded to form the middle arch rib (60). After that, the middle arch rib (60) is lifted to the designed position by the lifting device of the lifting bracket (5), and the constructed side arch ribs are closed with the middle arch rib (60); S5. Construction of auxiliary structures: including the installation of the suspender (70), the main crossbeam at the mid-span, and the cantilever beam (80), and the gradual removal of the lifting bracket (5), the old bridge pier (6), the arch rib support frame (9), the sliding platform (22), the assembly platform (21), and the water operation platform (3).

2. The construction method of a long-span steel arch bridge according to claim 1, characterized in that: In step S4, before closing, the stabilizing cables (51) connecting the lifting supports (5) on both sides are tensioned and pre-tightened, the tensioning steel strands (62) of the lifting section arch ribs (61) are connected, the lifting steel strands (52) between the lifting equipment and the lifting section arch ribs (61) are connected, and then the middle section arch ribs (60) are lifted to a preset height away from the arch rib support frame (9) and then stationary, and then the patched main longitudinal beam segments are hoisted, and the patched main longitudinal beam segments are welded to the middle section main longitudinal beam (50) to form a continuous structure, and then the middle section arch ribs (60) are lifted again for closing.

3. The construction method of a long-span steel arch bridge according to claim 2, characterized in that: In step S4, before the middle arch rib (60) is lifted, an initial pre-tightening force is applied to the tensioning steel strands (62) and the lifting steel strands (52), respectively, and then pre-tightening force is applied alternately to the tensioning steel strands (62) and the lifting steel strands (52) according to a predetermined plurality of increasing pre-tightening force levels until a final pre-tightening force target value is reached.

4. The construction method of a long-span steel arch bridge according to claim 3, characterized in that: In step S4 , the initial preload force is 30%-50% of the final preload force target value, and the multiple incremental preload force levels include four levels, namely 40%, 70%, 90% and 100% of the final preload force target value.

5. The construction method of a long-span steel arch bridge according to claim 2, characterized in that: In step S4, the lifting section arch rib (61) is lifted and positioned to the designed position by a multi-lifting point synchronous lifting system, and the closing arch rib segment is inserted between the lifting section arch rib (61) and the constructed side section arch rib segment (40) by using a lifting device (8) to carry out the closing construction. After the closing is completed, the tensioning steel strands (62) of the middle section arch rib (60) are first unloaded, and then the tension of the lifting steel strands (52) is unloaded step by step. After the lifting force is released, the initial tensioning of the suspender (70) is carried out.

6. The construction method of a long-span steel arch bridge according to claim 1, characterized in that: The installation method of the nearshore cross beam segment and the arch beam combined segment is as follows: Using a lifting device (8) and a sliding mechanism, for each of the plurality of nearshore beam segments, the following operations are performed: hoisting the segment from the water transport device onto the sliding mechanism, driving the segment to move to the shore side to a transfer position by the sliding mechanism, and then transferring the segment to a temporary storage area by the lifting device (8); Subsequently, the arch-beam combination segment is hoisted from the water transport equipment to the sliding mechanism by using the lifting equipment (8) and the sliding mechanism, and is driven by the sliding mechanism to move to the shore side to the transfer position, and then is positioned on the assembly platform (21) by the lifting equipment (8) and performs posture adjustment; Afterwards, the multiple temporarily stored nearshore beam segments are hoisted to the designed positions in a predetermined sequence by means of a lifting device (8); Wherein, the installation method is performed symmetrically on both sides of the bridge.

7. The construction method of a long-span steel arch bridge according to claim 1, characterized in that: The installation method of the nearshore main beam segment (30) is as follows: (a) For each of the plurality of nearshore main beam segments (30), perform the following operations: Transfer it from the water transport equipment to the skidding mechanism through a lifting system; Driven by the sliding mechanism, the vehicle moves toward the shore to a position close to the design position; Using the three-dimensional positioning system of the sliding mechanism to adjust its spatial posture; Transferring the load from the sliding mechanism to a temporary support frame of the sliding platform (22); (b) repeating the operation (a) in a predetermined order to complete the installation of a plurality of nearshore main beam segments (30); (c) Perform operations (a) to (b) symmetrically on both sides of the bridge.

8. The construction method of a long-span steel arch bridge according to claim 1, characterized in that: The installation method of the edge arch rib segment (40) is as follows: Perform the following actions symmetrically on both sides of the bridge: (a) installing multiple sets of first arch rib brackets on the shore-side main beam structure and multiple sets of second arch rib brackets on the water-side main beam structure; (b) supplying the arch rib segments of the nearshore side section and the arch rib segments of the waterside section by means of water transport equipment; (c) Performing graded lifting operations using lifting equipment (8): After the arch rib segments of the nearshore side section are hoisted to the water operation platform (3) for temporary storage, the position of the lifting equipment (8) is adjusted and the segments are hoisted to the designed position of the first arch rib support in sequence; After the arch rib segment of the near-water side section is hoisted to the water working platform (3) for temporary storage, the position of the lifting equipment (8) is adjusted and hoisted to the designed position of the second arch rib support; (d) Hoist the wind bracing segment to a temporary storage area on the installed structure, adjust the position of the lifting equipment (8) and hoist it to the designed position; (e) Hoist the closed arch rib segments to a temporary storage area on the installed structure.

9. The construction method of a long-span steel arch bridge according to claim 1, characterized in that: The installation method of the main beam in the middle of the span is: (a) First, hoist several main beams near the shore and apply the first level of initial tension to the horizontal tie rods; (b) When the installation completion rate of the nearshore main beams reaches the preset ratio, the remaining main beams in the mid-span will be hoisted simultaneously; (c) After all mid-span main beams are installed, perform secondary tension adjustment on the horizontal tie rods to the target internal force value.

10. The construction method of a long-span steel arch bridge according to claim 1, characterized in that: The installation of the cantilever beam (80) includes the installation of the nearshore cantilever beam (80) and the installation of the mid-span cantilever beam (80). The installation of the nearshore cantilever beam (80) is carried out on the water working platform (3) using a lifting device (8) and is installed in place together with the nearshore main beam segment (30). The installation of the mid-span cantilever beam (80) is directly hoisted into place using the floating hoisting equipment used when installing the middle section main longitudinal beam (50).

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