Large-span framing type steel box girder assembling method

Abstract

The invention belongs to the technical field of steel box girders, and particularly relates to a large-span framing type steel box girder assembly method which comprises the steps that S1, construction preparation is conducted; s2, the steel box girder is spliced in a segmented mode; s3, guide beam installation and pushing starting, specifically, a guide beam is additionally arranged at the front end of the steel box beam, two sets of walking type pushing jacks are started to form double circulation to alternately push the steel box beam to continuously advance along a sliding way, and when the two sets of walking type pushing jacks switch pushing, buffers are synchronously and alternately pushed to synchronously rise to provide switching buffering; s4, dynamic deviation correction and precision control are conducted, specifically, transverse deviation of the steel box girder is dynamically adjusted in the pushing process of the walking type pushing jacks, one set of walking type pushing jacks form supporting, and the other set of walking type pushing jacks conduct deviation correction; s5, beam falling and system conversion: a walking type pushing jack lifts a beam body, a slide way and temporary constraint are removed, and the beam body finally falls on a permanent pier to complete structural system conversion; s6, subsequent construction and quality detection; impact on the steel box girder when the two hydraulic cylinders are switched can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of steel box girders, and in particular relates to an assembly method of a large-span framed steel box girder. Background Art

[0002] The assembly construction of steel box girders mainly includes the hoisting method, the jacking method, the dragging method and the cantilever assembly method. The jacking method is mainly used in the construction of large-span steel box girders. The jacking method of steel box girder construction is an advanced construction technology widely used in large-span bridge projects. It is especially suitable for complex terrain conditions such as crossing deep valleys, rivers or busy traffic areas where it is difficult to erect supports. The basic principle of this method is to assemble the prefabricated steel box girder segments in sections on the assembly platform behind the abutment, and use jacking equipment such as hydraulic jacks to gradually push the beam forward along the bridge axis to the designed position, and finally complete the erection of the entire span structure. Compared with the traditional scaffolding cast-in-place or overall hoisting method, the jacking method does not require the large-scale erection of temporary support structures, significantly reducing the impact on the navigation, traffic or natural environment below. It has the advantages of high construction safety, low environmental interference, and controllable construction period.

[0003] The construction of long-span steel box girders requires a long construction time, and traditional walking-type jacking relies on a single-point, cyclic operation, resulting in frequent starts and stops during the jacking process. During construction, the walking-type jacking system uses a vertical jacking cylinder to lift the steel box girder, then a horizontal jacking cylinder pushes it forward. The beam is then lowered to a temporary support and the hydraulic cylinder resets. This cyclic process, completed by a single set of hydraulic cylinders, involves a "lift-forward-lower-reset" cycle. This results in continuous interruptions in the jacking process: the hydraulic cylinder reset phase not only consumes idle time but also forces the steel box girder to remain suspended periodically, impacting structural stability and limiting the possibility of continuous operation. While conventional jacking systems utilize two hydraulic cylinders alternately, when the two hydraulic cylinders switch, one stops jacking and resets while the other begins jacking, potentially resulting in brief interruptions or fluctuations in the jacking force output. This sudden change in pressure can cause uneven jacking speeds for the steel box girder, leading to uneven structural stress or localized impacts, compromising construction accuracy and linear control.

[0004] In order to improve construction efficiency and shorten construction time while reducing the impact of switching between two hydraulic cylinders, a method for assembling large-span split-frame steel box girders was proposed. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a method for assembling a large-span framed steel box girder.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A method for assembling a large-span framed steel box girder according to the present invention comprises the following steps: S1: Construction preparation: Build an assembly platform behind the abutment, erect temporary supports, and install two sets of walking-type jacking jacks on several temporary supports; S2: Segmental assembly of steel box beams: hoist the prefabricated steel box beam segments to the assembly platform, adjust the elevation and alignment, and then assemble and weld them; S3: Guide beam installation and jacking start: A guide beam is added to the front end of the steel box girder to guide it through the pier top. Two sets of walking jacking jacks are activated to form a double cycle to alternately push the steel box girder forward along the slideway. When the two sets of walking jacking jacks switch to jacking, the buffers are synchronously and alternately pushed up to provide switching buffering. S4: Dynamic deviation correction and precision control: The lateral deviation of the steel box girder is dynamically adjusted during the jacking process by using walking jacks. One set of walking jacks provides support, while the other set of walking jacks corrects the deviation. S5: Beam drop and system conversion: After the steel box girder is pushed to the designed position, the girder is lifted using a walking jack, and the slideways and temporary restraints are removed. Finally, the girder is dropped onto the permanent piers to complete the structural system conversion. S6: Subsequent construction and quality inspection: Conduct steel box girder connection and bridge deck load tests to ensure overall structural safety and functional integrity.

[0007] Furthermore, in step S3, the buffer is arranged between two groups of walking-type pushing jacks, and the buffer includes a rotating drum and a fixed rod. The rotating drum is sleeved on the fixed rod, and the side wall of the fixed rod is surrounded by corrugations. The inner wall of the rotating drum is provided with a convex rod, and the convex rod is slidably provided in the corrugations. The rotating drum rotates and rises and falls with the sliding of the convex rod and the corrugations. Two groups of rocker rods are provided on the outer side wall of the rotating drum. The two groups of walking-type pushing jacks push alternately and push the rocker rod synchronously to make the rotating drum rotate and rise and fall.

[0008] Furthermore, a rubber buffer pad is provided on the top of the rotating drum.

[0009] Furthermore, in step S1, the two groups of walking-type pushing jacks are respectively a left jack and a right jack, and the left jack and the right jack both include a frame and a propulsion hydraulic cylinder, and the propulsion hydraulic cylinder is horizontally arranged in the frame, and the first inlet and outlet oil ports of the propulsion hydraulic cylinder of the left jack are connected to the second inlet and outlet oil ports of the propulsion hydraulic cylinder of the right jack, and the second inlet and outlet oil ports of the propulsion hydraulic cylinder of the left jack are connected to the first inlet and outlet oil ports of the propulsion hydraulic cylinder of the right jack.

[0010] Furthermore, the left jack and the right jack also include a lifting hydraulic cylinder, a correcting hydraulic cylinder and a control device, and the control device is electrically connected to the lifting hydraulic cylinder, the correcting hydraulic cylinder and the propulsion hydraulic cylinder respectively. The bottom of the lifting hydraulic cylinder is slidingly arranged in the frame and is connected to the movable end of the propulsion hydraulic cylinder. The correcting hydraulic cylinder is horizontally slidably arranged on the frame, and the movable end of the correcting hydraulic cylinder is connected to the side of the fixed end of the lifting hydraulic cylinder. The control device controls the lifting hydraulic cylinder and the propulsion hydraulic cylinder to alternately lift and propel.

[0011] Furthermore, in step S3, the control device controls the actions of the jacking hydraulic cylinder and the propulsion hydraulic cylinder, so that the top of the jacking hydraulic cylinder moves in a parabolic trajectory when pushing the steel box girder, and moves in an inverted parabolic trajectory when retracting and returning to its original position.

[0012] Furthermore, in step S3, the push hydraulic cylinder abuts against the swing arm of the drum in the descending section of the parabolic trajectory and pushes the drum to rotate and rise.

[0013] Furthermore, when the two groups of walking type jacking jacks are raised and lowered to a distance of 20 mm from the staggered height, the speed of the two lifting hydraulic cylinders of the walking type jacking jacks is reduced to half of the normal state.

[0014] Furthermore, in step S4, a laser locator is set on the permanent bridge pier and electrically connected to the control device. Detection points are respectively set on the front guide beam and the rear end of the steel box girder. The laser locator determines the distance between the detection points and the posture of the steel box girder by locating the distance, and transmits the detection data to the control device. The control device instructs the correction hydraulic cylinder to dynamically adjust the posture of the steel box girder.

[0015] Furthermore, a bidirectional distance sensor is provided on the frame, and the bidirectional distance sensor is electrically connected to the control device. The two detection directions of the bidirectional distance sensor are perpendicular to each other, and the horizontal detection direction is toward the jacking hydraulic cylinder, and the vertical detection direction is toward the steel box girder.

[0016] The beneficial effects of the present invention are: (1) In step S3, when the two groups of walking jacking jacks push the steel box girder, one of the walking jacking jacks first lifts the steel box girder and moves it forward, while the other walking jacking jack is lowered and reset. When the walking jacking jack moves forward, it pushes the buffer to rise until the first walking jack is lowered and the second walking jack is raised and reaches the position for switching to push the steel box girder. The buffer is synchronously raised to the bottom of the steel box girder and forms a supporting role, which is used to provide switching buffer for the steel box girder, thereby preventing the two groups of walking jacking jacks from interrupting the pushing of the steel box girder due to the asynchronous switching action, thereby causing uneven distribution of the pushing force. (2) In the initial state, due to the action of gravity, the convex rod in the rotating drum is at the lowest point of the corrugation. At this position, the rocker arm on the rotating drum is perpendicular to the propulsion direction of the two groups of walking jacking jacks. When one of the walking jacking jacks moves forward, it will push the rotating drum to rotate and rise until the convex rod moves to the top of the corrugation to support the steel box girder. At this time, the two groups of walking jacking jacks are in the state of switching to push. The support of the rotating drum to the steel box girder can provide part of the supporting force to avoid the interruption of pushing when the two groups of walking jacking jacks switch to push. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] To facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0018] Figure 1 is a flow chart of the steps of the present invention; Figure 2 It is a schematic diagram of the overall structure of the present invention; Figure 3 Schematic diagram of the internal structure of the present invention; Figure 4 This is a schematic diagram of the internal structure of the buffer of the present invention when it is descending; Figure 5 This is a schematic diagram of the internal structure of the buffer of the present invention when it is raised; Legend: 1. Left jack; 2. Right jack; 3. Propulsion hydraulic cylinder; 31. First oil inlet and outlet; 32. Second oil inlet and outlet; 4. Frame; 5. Correction hydraulic cylinder; 6. Lifting hydraulic cylinder; 7. Bidirectional distance sensor; 8. Rotating drum; 9. Rocker arm; 10. Rubber buffer pad; 11. Fixing rod; 12. Corrugation; 13. Protruding rod. DETAILED DESCRIPTION

[0019] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0020] like Figure 1-Figure 5 As shown, a method for assembling a large-span framed steel box girder of the present invention comprises the following steps: S1: Construction preparation: Build an assembly platform behind the abutment, erect temporary supports, and install two sets of walking jacks on several temporary supports; there are several temporary supports, each of which has two sets of walking jacks; S2: Segmental assembly of steel box beams: hoist the prefabricated steel box beam segments to the assembly platform, adjust the elevation and alignment, and then assemble and weld them; S3: Guide beam installation and jacking start: A guide beam is added to the front end of the steel box girder to guide it through the pier top. Two sets of walking jacking jacks are activated to form a double cycle to alternately push the steel box girder forward along the slideway. When the two sets of walking jacking jacks switch to jacking, the buffers are synchronously and alternately pushed up to provide switching buffering. S4: Dynamic deviation correction and precision control: The lateral deviation of the steel box girder is dynamically adjusted during the jacking process by using walking jacks. One set of walking jacks provides support, while the other set of walking jacks corrects the deviation. S5: Beam drop and system conversion: After the steel box girder is pushed to the designed position, the girder is lifted using a walking jack, and the slideways and temporary restraints are removed. Finally, the girder is dropped onto the permanent piers to complete the structural system conversion. S6: Subsequent construction and quality inspection: Conduct steel box girder connection and bridge deck load tests to ensure overall structural safety and functional integrity; Because the two hydraulic cylinders alternately push the steel box girder, one stops pushing and resets while the other begins pushing. This switching between the two cylinders can cause brief interruptions or fluctuations in the thrust output. This sudden change in pressure can cause uneven advancement of the steel box girder, leading to uneven stress on the structure or localized impacts, affecting construction accuracy and alignment control. Furthermore, the coordination of the two hydraulic cylinders' alternating thrust is difficult to control. Inconsistent pressure response speed or flow distribution (for example, due to differences in pipeline resistance or control delays) can lead to uneven thrust distribution. For example, if pressure is not established in one hydraulic cylinder before the other begins, this can easily cause the steel box girder to shift laterally or become stuck, requiring additional correction and adjustment.

[0021] Therefore, in step S3, when the two groups of walking jacking jacks push the steel box girder, one of the walking jacking jacks will first lift the steel box girder and move it forward, and the other walking jacking jack will be lowered and reset. When the walking jacking jack moves forward, it will push the buffer to rise until the previous walking jacking jack is lowered and the next walking jacking jack is raised and reaches the position for switching to push the steel box girder. The buffer will rise synchronously to the bottom of the steel box girder and form a supporting role, which is used to provide switching buffer for the steel box girder to prevent the two groups of walking jacking jacks from interrupting the pushing of the steel box girder due to the asynchronous switching action, and then causing uneven distribution of the pushing force.

[0022] Specifically, in step S3, a buffer is set between the two groups of walking-type pushing jacks. The buffer includes a rotating drum 8 and a fixed rod 11. The rotating drum 8 is sleeved on the fixed rod 11. The side wall of the fixed rod 11 is surrounded by a corrugation 12. The inner wall of the rotating drum 8 is provided with a protruding rod 13. The protruding rod 13 is slidably provided in the corrugation 12. The rotating drum 8 rotates and rises and falls with the sliding of the protruding rod 13 and the corrugation 12. Two groups of rocker rods 9 are provided on the outer wall of the rotating drum 8. The two groups of walking-type pushing jacks alternately push and synchronously push the rocker rods 9 to rotate and rise and fall the rotating drum 8. The rocker arm 9 on the drum 8 is horizontally positioned, and in the buffer installation position, the rocker arm 9 extends to a distance that allows contact with the two walking jacking jacks during propulsion. The fixed rod 11 is provided with a corrugation 12 that circulates and rises. After the drum 8 is mounted on the fixed rod 11 and the protruding rod 13 inside the drum 8 is located within the corrugation 12, in the initial state, due to the action of gravity, the protruding rod 13 inside the drum 8 is at the lowest point of the corrugation 12. In this position, the rocker arm 9 on the drum 8 is perpendicular to the propulsion direction of the two sets of walking jacking jacks. When one of the walking jacking jacks propels forward, it pushes the drum 8 to rotate and rise until the protruding rod 13 reaches the top of the corrugation 12, supporting the steel box girder. At this point, the two walking jacking jacks are in a state of switching propulsion. The drum 8 can provide some support for the steel box girder, preventing propulsion interruptions when the two walking jacking jacks switch propulsion. And after drum 8 reaches apex, as the walking type jacking jack after pushing resets, swing rod 9 also gradually resets after convex rod 13 slides off corrugation 12. After the walking type jacking jack on the other side pushes forward, drum 8 rises again and provides support, and the cycle repeats.

[0023] In order to provide effective buffering through the buffer between the alternating jacking actions of the two sets of walking jacking jacks, in one embodiment, a rubber buffer pad 10 is provided on the top of the rotating drum 8; by providing the rubber buffer pad 10, it can contact the bottom of the steel box girder just before the two sets of walking jacking jacks switch to jacking, and provide flexible contact by squeezing the rubber buffer pad 10 while the rotating drum 8 continues to move upward, until the rotating drum 8 rises to the highest point to provide the maximum supporting force for the steel box girder.

[0024] Since in the above embodiment, the buffer is used to temporarily support the two groups of walking jacking jacks when switching the jacking action, in order to ensure that the two groups of walking jacking jacks are in corresponding positions at the moment of switching, the synchronization of the actions of the two groups of walking jacking jacks becomes a necessary condition. In order to achieve the synchronization of the pushing and retracting actions of the two groups of walking jacking jacks, in one embodiment, in step S1, the two groups of walking jacking jacks are respectively the left jack 1 and the right jack 2, and the left jack 1 and the right jack 2 include a frame 4 and a propulsion hydraulic cylinder 3, and the propulsion hydraulic cylinder 3 is horizontally arranged in the frame 4, and the first inlet and outlet oil port 31 of the propulsion hydraulic cylinder 3 of the left jack 1 is connected to the second inlet and outlet oil port 32 of the propulsion hydraulic cylinder 3 of the right jack 2, and the second inlet and outlet oil port 32 of the propulsion hydraulic cylinder 3 of the left jack 1 is connected to the first inlet and outlet oil port 31 of the propulsion hydraulic cylinder 3 of the right jack 2; The left and right jacks 1 and 2 have identical structures. Their thrust cylinders 3 form two front and rear chambers, each equipped with a first oil inlet and outlet 31 and a second oil inlet and outlet 32. Hydraulic oil is supplied to these two inlets and outlets to drive the thrust cylinders 3 to advance and retract. In the aforementioned embodiment, the two groups of walking jacks need to advance alternately and maintain synchronization. Therefore, the first and second oil inlet and outlet 31, 32 of the two thrust cylinders 3 are interconnected, with one of the thrust cylinders 3 connected to an external hydraulic oil pump. When hydraulic oil is supplied to the first oil inlet and outlet 31 of the left jack 1 via the hydraulic oil pump, the thrust cylinder 3 of the left jack 1 advances, while hydraulic oil is simultaneously supplied to the second oil inlet and outlet 32 ​​of the right jack 2, causing the thrust cylinder 3 of the right jack 2 to retract. Conversely, the thrust cylinder 3 of the left jack 1 retracts while the thrust cylinder 3 of the right jack 2 advances. By connecting the two propulsion hydraulic cylinders 3 , the actions of the two propulsion hydraulic cylinders 3 can be synchronized.

[0025] Furthermore, the left jack 1 and the right jack 2 also include a lifting hydraulic cylinder 6, a deviation-correcting hydraulic cylinder 5 and a control device. The control device is electrically connected to the lifting hydraulic cylinder 6, the deviation-correcting hydraulic cylinder 5 and the propulsion hydraulic cylinder 3 respectively. The bottom of the lifting hydraulic cylinder 6 is slidably arranged in the frame 4 and is connected to the movable end of the propulsion hydraulic cylinder 3. The deviation-correcting hydraulic cylinder 5 is horizontally slidably arranged on the frame 4, and the movable end of the deviation-correcting hydraulic cylinder 5 is connected to the side of the fixed end of the lifting hydraulic cylinder 6. The control device controls the lifting hydraulic cylinder 6 and the propulsion hydraulic cylinder 3 to alternately lift and propel. The movable end of the propulsion hydraulic cylinder 3 is slidably connected to the side of the jacking hydraulic cylinder 6. When the correction hydraulic cylinder 5 needs to correct the deviation, the correction hydraulic cylinder 5 pushes the side of the jacking hydraulic cylinder 6, so that the jacking hydraulic cylinder 6 and the propulsion hydraulic cylinder 3 form a relative horizontal sliding, and the correction hydraulic cylinder 5 needs to move with the jacking hydraulic cylinder 6, so the fixed end of the correction hydraulic cylinder 5 is slidably connected to the frame 4.

[0026] Specifically, in step S3, the control device controls the actions of the jacking hydraulic cylinder 6 and the propulsion hydraulic cylinder 3, so that the top of the jacking hydraulic cylinder 6 moves in a parabolic trajectory when pushing the steel box girder, and moves in an inverted parabolic trajectory when retracting and resetting; when the left jack 1 pushes the steel box girder, the propulsion hydraulic cylinder 3 of the left jack 1 is in a retracted position in the initial state, and the propulsion hydraulic cylinder 3 of the right jack 2 is in a propulsion position in the initial state. At this time, the steel box girder is simultaneously on the left jack 1 and the right jack 2. The control device instructs the propulsion hydraulic cylinder 3 of the left jack 1 to advance while instructing the jacking hydraulic cylinder 6 to rise synchronously, while the right jack 2 retracts and descends, completing the switching jacking action of the two jacks on the steel box girder, and then the left jack 1 continues to advance and rise until the jacking hydraulic cylinder 6 reaches the highest point after advancing half the distance. While continuing to advance, the jacking hydraulic cylinder 6 gradually lowers, the jacking action of the left hydraulic cylinder forms a parabolic trajectory, and the reset action of the right hydraulic cylinder forms an inverted parabolic trajectory.

[0027] Furthermore, in step S3, the pushing hydraulic cylinder abuts against the rocker arm 9 of the rotating drum 8 in the descending section of the parabolic trajectory and pushes the rotating drum 8 to rotate and rise; the buffer is set at half of the advancing distance of the propulsion hydraulic cylinder 3, so that the two pushing hydraulic cylinders contact and push the rocker arm 9 of the buffer in the second half of the moving distance of the propulsion hydraulic cylinder 3 and after the lifting hydraulic cylinder 6 starts to descend, which can avoid interference between the two lifting hydraulic cylinders 6 and the buffer when they are reset under the action of the propulsion hydraulic cylinder 3.

[0028] Furthermore, when the two groups of walking jacking jacks are raised and lowered to a distance of 20 mm from the staggered height, the speed of the two lifting hydraulic cylinders 6 of the walking jacking jacks is reduced to half of the normal state; Since the steel box girder is alternately pushed by two sets of walking jacking jacks, and the weight of the steel box girder is heavy, each walking jacking jack needs to keep moving slowly to avoid multiple walking jacking jacks from being out of sync. Assuming that the left jack 1 is raised and the right jack 2 is lowered in the two sets of walking jacking jacks, the superimposed speed of the two sets when switching the pushing is twice that of the normal single-cycle pushing action. Therefore, when the distance for switching the pushing is about to be reached, the lifting and lowering speed needs to be reduced to half of the original speed to avoid the control of multiple walking jacking jacks from being out of sync due to excessive movement speed.

[0029] Furthermore, in step S4, a laser locator is installed on the permanent bridge pier and electrically connected to the control device. Detection points are respectively set on the front guide beam and the rear end of the steel box girder. The laser locator determines the distance between the detection points and the posture of the steel box girder by locating the distance, and transmits the detection data to the control device. The control device instructs the correction hydraulic cylinder 5 to dynamically adjust the posture of the steel box girder. Since permanent bridge piers are the piers where the steel box girder needs to be installed, laser locators are installed on them. The laser locators detect the distances between monitoring points at different locations on the steel box girder. The control device calculates the position of the steel box girder based on the results. The corrective hydraulic cylinder 5 on one of the walking jacks then corrects the girder as the lifting hydraulic cylinder 6 raises it. Through the synchronized adjustment of the corrective hydraulic cylinders 5 on several walking jacks, the steel box girder is gradually moved to the correct position. The alternating jacking action of the two sets of walking jacks allows for faster correction of the steel box girder.

[0030] Furthermore, a bidirectional distance sensor 7 is provided on the frame 4, and the bidirectional distance sensor 7 is electrically connected to the control device. The two detection directions of the bidirectional distance sensor 7 are perpendicular to each other, and the horizontal detection direction is toward the jacking hydraulic cylinder 6, and the vertical detection direction is toward the steel box girder; the position of the propulsion hydraulic cylinder 3 is detected by the bidirectional distance sensor 7, and after the position of the propulsion hydraulic cylinder 3 is fed back to the control device, the corresponding jacking hydraulic cylinder 6 is instructed to perform the corresponding lifting action, and the position of the steel box girder is detected in the vertical detection direction to ensure accurate control of the jacking distance.

[0031] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for assembling a long-span framed steel box girder, characterized by: The following steps are involved: S1: Construction preparation: Build an assembly platform behind the abutment, erect temporary supports, and install two sets of walking-type jacking jacks on several temporary supports; S2: Segmental assembly of steel box beams: hoist the prefabricated steel box beam segments to the assembly platform, adjust the elevation and alignment, and then assemble and weld them; S3: Guide beam installation and jacking start: A guide beam is added to the front end of the steel box girder to guide it through the pier top. Two sets of walking jacking jacks are activated to form a double cycle to alternately push the steel box girder forward along the slideway. When the two sets of walking jacking jacks switch to jacking, the buffers are synchronously and alternately pushed up to provide switching buffering. S4: Dynamic deviation correction and precision control: The lateral deviation of the steel box girder is dynamically adjusted during the jacking process by using walking jacks. One set of walking jacks provides support, while the other set of walking jacks corrects the deviation. S5: Beam drop and system conversion: After the steel box girder is pushed to the designed position, the girder is lifted using a walking jack, and the slideways and temporary restraints are removed. Finally, the girder is dropped onto the permanent piers to complete the structural system conversion. S6: Subsequent construction and quality inspection: Conduct steel box girder connection and bridge deck load tests to ensure overall structural safety and functional integrity.

2. The method for assembling a long-span framed steel box girder according to claim 1, characterized in that: In step S3, the buffer is arranged between two groups of walking-type pushing jacks, and the buffer includes a rotating drum and a fixed rod. The rotating drum is sleeved on the fixed rod, and the side wall of the fixed rod is surrounded by corrugations. The inner wall of the rotating drum is provided with a convex rod, and the convex rod is slidably provided in the corrugations. The rotating drum rotates and rises and falls with the sliding of the convex rod and the corrugations. Two groups of rocker rods are provided on the outer side wall of the rotating drum. The two groups of walking-type pushing jacks push alternately and push the rocker rod synchronously to make the rotating drum rotate and rise and fall.

3. The method for assembling a long-span framed steel box girder according to claim 2, characterized in that: A rubber buffer pad is provided on the top of the rotating drum.

4. The method for assembling a long-span framed steel box girder according to claim 2, wherein: In step S1, the two groups of walking-type pushing jacks are respectively a left jack and a right jack, and the left jack and the right jack both include a frame and a propulsion hydraulic cylinder, and the propulsion hydraulic cylinder is horizontally arranged in the frame, and the first inlet and outlet oil ports of the propulsion hydraulic cylinder of the left jack are connected to the second inlet and outlet oil ports of the propulsion hydraulic cylinder of the right jack, and the second inlet and outlet oil ports of the propulsion hydraulic cylinder of the left jack are connected to the first inlet and outlet oil ports of the propulsion hydraulic cylinder of the right jack.

5. The method for assembling a long-span framed steel box girder according to claim 4, characterized in that: The left jack and the right jack also include a lifting hydraulic cylinder, a correcting hydraulic cylinder and a control device. The control device is electrically connected to the lifting hydraulic cylinder, the correcting hydraulic cylinder and the propulsion hydraulic cylinder respectively. The bottom of the lifting hydraulic cylinder is slidably arranged in the frame and is connected to the movable end of the propulsion hydraulic cylinder. The correcting hydraulic cylinder is horizontally slidably arranged on the frame, and the movable end of the correcting hydraulic cylinder is connected to the side of the fixed end of the lifting hydraulic cylinder. The control device controls the lifting hydraulic cylinder and the propulsion hydraulic cylinder to alternately lift and propel.

6. The method for assembling a long-span framed steel box girder according to claim 5, characterized in that: In step S3, the control device controls the actions of the jacking hydraulic cylinder and the propulsion hydraulic cylinder, so that the top of the jacking hydraulic cylinder moves in a parabolic trajectory when pushing the steel box girder, and moves in an inverted parabolic trajectory when retracting and returning to its original position.

7. The method for assembling a long-span framed steel box girder according to claim 5, characterized in that: In step S3, the push hydraulic cylinder contacts the swing arm of the drum in the descending section of the parabolic trajectory and pushes the drum to rotate and rise.

8. The method for assembling a long-span framed steel box girder according to claim 1, characterized in that: When the two sets of walking type jacking jacks are raised and lowered to a distance of 20mm from the staggered height, the speed of the two lifting hydraulic cylinders of the walking type jacking jacks is reduced to half of the normal state.

9. The method for assembling a long-span framed steel box girder according to claim 5, characterized in that: In step S4, a laser locator is set on the permanent bridge pier and electrically connected to the control device. Detection points are respectively set on the front guide beam and the rear end of the steel box girder. The laser locator determines the distance between the detection points and the posture of the steel box girder by locating the distance, and transmits the detection data to the control device. The control device instructs the correction hydraulic cylinder to dynamically adjust the posture of the steel box girder.

10. The method for assembling a long-span framed steel box girder according to claim 9, characterized in that: A bidirectional distance sensor is provided on the frame and is electrically connected to the control device. The two detection directions of the bidirectional distance sensor are perpendicular to each other, and the horizontal detection direction is toward the jacking hydraulic cylinder, and the vertical detection direction is toward the steel box girder.

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