A continuous steel web-plate truss double-layer combined swing bridge stress conversion method

Abstract

The application discloses a continuous steel web-plate truss double-layer combined swivel bridge stress conversion method, which comprises the following steps: after the ribbed slab type prestressed concrete beam structure is completely poured and tensioned, the support is removed, then the temporary supporting piers are removed in a symmetric mode according to the mode of removing one every other one from the main pier to the two end directions, and the outermost row of temporary supporting piers is reserved to be removed after temporary steel supports are installed; finally, the main beam side pier supporting cushion stones are poured, and the bearings are installed; the main beam is supported on the bearings, and the stress conversion is completed; by using the construction scheme, the outermost row of temporary supporting piers of the swivel bridge is reserved to be removed after the temporary steel supports are installed, so that the structure state of the swivel bridge in the three-pier two-span supporting state in the service state is effectively inspected before the outermost row of temporary supporting piers is removed, the structure state is in line with the design requirements, and the longitudinal overturning stability of the long cantilever structure in the process of removing the outermost row of temporary supporting piers and the swivel construction is greatly enhanced.

Description

Technical Field

[0001] This invention relates to the field of construction technology for rotating bridges, and in particular to a method for force conversion of a continuous steel truss web-plate truss double-layer combined rotating bridge. Background Technology

[0002] The construction of rotating bridges, including the conversion of the load-bearing system, is a key construction procedure for projects such as rotating bridges that cross canyons or railways. Controlling the risk of overturning of the bridge structure, controlling the deflection of the cantilevered structure, controlling the cracks in the concrete bridge structure itself, and converting the load-bearing system of the bridge structure before and after the rotation are all very important control modules. Failure to control any of these modules will have a very serious adverse impact on the construction of the rotating bridge.

[0003] Currently, the structural design and construction of bridges spanning railways mostly adopt single-layer T-shaped long cantilever prestressed concrete bridges, and their rotation construction technology is relatively mature and complete. However, the rotation construction of continuous steel truss web-plate girder double-layer composite rotating bridge structures, especially the transformation process of the stress system of such rotating bridge structures, is significantly different from that of single-layer T-shaped long cantilever prestressed concrete bridges. Therefore, research on the stress transformation method of continuous steel truss web-plate girder double-layer composite rotating bridges has important innovative value and practical guiding significance. Summary of the Invention

[0004] To overcome the aforementioned technical challenges, this invention provides a method for force conversion in a continuous steel truss web-plate truss double-layer composite rotating bridge. This double-layer composite rotating bridge adopts a T-shaped long cantilever continuous steel truss web-plate truss composite structure arranged across the entire span. The lower layer uses ribbed prestressed concrete beams with three main beams arranged laterally. The upper layer uses steel truss beams, with three main trusses arranged laterally corresponding to the three main beams of the concrete beams. These main trusses are longitudinally Warren-type trusses, including diagonal members and an upper chord. Steel bridge decks are installed on the steel truss beams. Temporary supports are arranged in rows longitudinally corresponding to the Warren-type main truss steel truss nodes.

[0005] During construction, after the T-shaped long cantilever ribbed prestressed concrete beam structure has been fully poured and tensioned, the full-span scaffolding should be dismantled. When dismantling the scaffolding, it should be unloaded at multiple points and in stages to allow the cantilever structure to naturally deflect completely. The longitudinal overturning stability of the cantilever structure must be guaranteed during the unloading process. The temporary supports of the rotating bridge are divided into the middle row of temporary supports and the outermost row of temporary supports. When dismantling the temporary supports, they should be dismantled from the main pier towards both ends in a symmetrical manner, with one support removed at a time. The outermost row of temporary supports should be retained until the temporary steel supports are installed before dismantling them.

[0006] The monitoring unit monitors the deformation of the support and temporary supports after each stage of dismantling. According to the line monitoring data, when the pressure value of the outermost row of temporary supports is close to zero when the beam is lowered by jacks, temporary steel supports for anti-overturning during rotation are installed. Theoretically, the temporary steel supports are not under stress. In actual construction, when unbalanced bending moments are generated at both ends of the rotating beam, the temporary steel supports are subjected to force to offset this part of the force, ensuring construction safety. After the temporary steel supports are completed, the outermost row of temporary supports is removed before rotation. The outermost row of temporary supports is a steel pipe concrete column pier structure.

[0007] When installing temporary steel supports next to the main pier, it is necessary to ensure that the temporary steel supports do not restrict the symmetrical downward deflection of the T-shaped long cantilever beam structure; the top of the temporary steel support diagonal brace is equipped with a steel support beam, and the contact surface with the bottom of the beam is padded with a rubber plate to ensure that the temporary steel support is tightly pressed against the bottom of the beam without gaps after the cantilever deflection is completed; the temporary steel support system only provides vertical support for the rotating bridge, and the horizontal force is borne by the steel connecting beams within the temporary steel support system.

[0008] As a preferred option, the temporary steel support diagonal bracing rods are made of large-diameter steel pipes, and the horizontal steel connecting beams are made of steel pipes or I-beams for tie rods. Embedded parts are set accordingly during the construction of the main pier cap and the main pier cover beam, and the main pier column base is set on the main pier cap.

[0009] In the construction design of a rotating bridge, the rotation principle is that the weight of the beam is transferred to the upper ball joint through the pier, and then transferred to the lower ball joint and the abutment through the sliding plates between the ball joints. After the main beam construction is completed, the empty sand box transfers the entire weight of the beam to the ball joints. Then, using the traction cable embedded in the upper turntable and the rotating continuous jacks, the dynamic friction torque between the upper and lower ball joints and between the support legs and the sliding track is overcome, so that the bridge body rotates into place.

[0010] The specific construction process of rotating the structure mainly includes the following steps:

[0011] (1) Preparations should be completed before the rotation construction: 1) First, make the traction jacks reach the predetermined tonnage, start the power system equipment, and make it run in automatic mode; 2) The force of the symmetrical jacks used for each rotation should always be equal in magnitude and opposite in direction, so as to ensure that the upper turntable only bears the dynamic couple that is balanced with the friction torque, and no overturning torque is generated; 3) During the operation of the equipment, the attention of the personnel in each position must be highly concentrated, and they should pay attention to the operation of the power system equipment and the rotation parts at all times; if any abnormal situation occurs, it must be reported to the on-site commander immediately, and the machine must be stopped immediately for handling. The equipment can only be restarted and continued to operate after the hidden danger has been completely eliminated; 4) When the key construction begins, the existing line isolation fence should be opened first, the line should be blocked, protection should be set up, and the contact network should be de-energized.

[0012] (2) Rotation Implementation: 1) After the trial rotation is completed, analyze the collected data, compile detailed data for controlling the rotation, and immediately carry out the formal rotation. The interval between the trial rotation and the formal rotation should not exceed 24 hours; 2) Before rotating the structure, personnel should be assigned tasks. Based on each key part and construction link, the on-site personnel should be carefully deployed, each performing their duties and cooperating with each other. The overall on-site commander should make unified arrangements; 3) The hydraulic control system, key approvals, weather conditions, structure, etc., should all be ready and meet the rotation requirements. All personnel should be in place, and the rotation personnel should be received by the project manager. After receiving the rotation command, start the power system equipment and run it in automatic mode; 4) During the operation of the equipment, all personnel must be highly focused and constantly observe and monitor the operation of the power system equipment and the rotation of the bridge deck. Report to the project manager every time the beam end rotates a certain distance. Within 3-5 meters of the endpoint, report to the project manager every 1 meter; within 40 cm of the endpoint, report to the project manager every 2 cm; within 20 cm, report every 1 cm; and within 2 cm, report every 1 millimeter. To ensure that operators of the control system can promptly grasp the rotation status, facilitate the operation of the control system, and achieve the ideal design requirements for the rotation; 5) Lay a 10mm PTFE plate in the 30mm reserved gap between the inner ring balance foot and the pre-embedded steel plate walking track on the top of the bearing platform as a balance walking track during rotation; If the distance between the inner ring balance foot and the walking track changes due to unbalanced force or load during the rotation process, insert PTFE plates at the corresponding eccentric points to correct the eccentricity problem; 6) When the rotating structure is close to the design position, that is, the beam end is 50-80cm away from the design position (distance from... When the distance to the designed position needs to be determined by the coefficient measured during the trial rotation, the system is paused; to prevent the structure from over-rotating, after the inertial operation is completed, the power system is switched from manual to jog operation to position; after each jog operation, the surveyor reports the current status data of the axis movement once, repeating the cycle until the structure axis is accurately positioned; during the entire rotation construction process, the total station is used to strengthen the monitoring of the elevation at both ends of the beam; 7) during the rotation process, it is necessary to ensure continuity, so that the time before, the process of, and the time after the key point are connected, so as to achieve one-time positioning, and try not to stop in the middle.

[0013] (3) Rotation and Positioning: 1) Rotation and positioning are performed using a total station for centerline correction, with a centerline deviation not exceeding 2cm; 2) On-site positioning measurement plan: ① Central plumb bob control: Use a plumb bob to check whether the centerline of the beam end coincides with the centerline of the side span; ② Set up one total station on each side of the beam, set the line of sight of each instrument to the theoretical center direction of the beam, and then observe the rotation and positioning process; ③ Set up one level on each end of the beam to observe the beam top elevation after the beam end is positioned; 3) After rotation and positioning, a temporary scaffold is used to support the beam to ensure the stability of the structure, and the outside of the temporary scaffold is completely sealed with safety nets. 4) After the rotating structure is precisely positioned, the structure is constrained and fixed; the elevation of the beam end is precisely adjusted using jacks set at the bottom of the turntable, and measures are taken to pad the beam end; after the beam elevation is adjusted and the rotating structure is precisely positioned, the structure is constrained and fixed; 5) After the rotating structure is precisely positioned, the sealing concrete is poured immediately to complete the consolidation of the turntable structure in the shortest possible time; the upper surface of the base is cleaned, the reserved steel bars are welded, the formwork is erected and the sealing concrete is poured to connect the turntable and the lower turntable into one; the concrete slump is controlled to facilitate vibration and enhance the sealing effect.

[0014] After the formal rotation is completed, and after monitoring the plane position and elevation during the rotation and precise positioning stages, which all meet the design requirements, the temporary locking methods are: ① immediately drive steel wedges between the support feet and the slide, and weld steel reaction frames (with pre-positioned and embedded steel plates) onto the lower turntable bearing platform; ② immediately weld the reserved reinforcing bars on the upper and lower turntables.

[0015] Sealing the turntable: After temporary locking is completed and the rotating unit is ensured to no longer shift, the turntable is sealed as quickly as possible. The surface of the chassis is cleaned of dirt, the pre-installed pressure-reducing pipes are checked for blockage, the pre-installed reinforcing bars on the upper and lower turntables are welded, the formwork is installed, and safety pressure-reducing pipes are installed at the top of the four corners of the sealed turntable. Sealing concrete (micro-expansion concrete) is poured, and the concrete must be vibrated to ensure compaction, making the upper and lower turntables a single unit. Because grouting pipes and subsequent safety grouting pipes were pre-installed during the construction of the upper turntable, the same grade of grouting cement is used to fill the sealing concrete area between the upper and lower turntables to ensure its density.

[0016] After installing the supports and completing the paving stone pouring: Once the upper and lower turntables are permanently sealed after rotation, jacks are placed on the top surface of the lower cap beam of the side pier to lift the ends of each side of the main beam. The lifting force and displacement are controlled simultaneously, with the error to be within 5%. The lifting positions in the longitudinal direction are all within the range of the end crossbeams; the transverse lifting positions should be as close to the supports as possible. For the outer supports, four 600t jacks are placed within 2m of the side longitudinal beam on the end crossbeam. For the inner supports, two 400t jacks and two 300t jacks are placed within 1.5m of each side of the middle longitudinal beam on the end crossbeam.

[0017] ① Apply vertical jacking force to the beam ends using jacks. Jacking should be carried out simultaneously at the large and small mileage beam ends, and simultaneously on the three main beams at the same beam end. The jacking force should be applied uniformly, slowly, and synchronously. ② During construction, construction monitoring should be strengthened, and jacking force and main beam elevation should be controlled simultaneously, but the main beam elevation should be the primary factor. When the jacking force reaches the design value, the elevation of the main beam at the beam end should be equal to the design elevation. ③ After the jacking is completed, temporary compression supports should be set between the main beam and the side pier. The top surface of the temporary supports should be flush with the bottom of the beam. ④ Pour the support pads for the main beam and side pier. After the pads reach the design strength, install the supports. After the supports are installed, remove the temporary supports and jacks. The main beam will be supported on the supports, completing the force transfer.

[0018] The beneficial effects of using this invention are as follows: In specific construction, the temporary supports of the rotating bridge are dismantled symmetrically from the main pier towards the two end piers, one at a time, while the outermost row of temporary supports is retained and dismantled after the temporary steel supports are installed. This effectively verifies that the structural state of the rotating bridge in its three-pier, two-span support state meets the design requirements before the outermost row of temporary supports is dismantled. During the rotation construction, the beam height of the double-layer combined rotating bridge structure is significantly higher than that of the single-layer rotating bridge, resulting in a significantly increased risk of overturning during the bridge rotation. When unbalanced bending moments occur at both ends of the rotating bridge, the combined structure of temporary steel supports for anti-overturning is used to offset this force, greatly enhancing the longitudinal anti-overturning stability of the long cantilever structure during the dismantling of the outermost row of temporary supports and the rotation construction process, thus ensuring construction safety. Attached Figure Description

[0019] Figure 1 : Schematic diagram of temporary support for a double-layer combined rotating bridge in a state of alternating dismantling and reassembly;

[0020] Figure 2 Schematic diagram of temporary steel supports for the installation of a double-layer combined rotating bridge;

[0021] Figure 3 Enlarged schematic diagram of the temporary steel support structure nodes;

[0022] Figure 4 Schematic diagram of the bottom surface node of the temporary steel support;

[0023] Figure 5 Schematic diagram of the top surface node of the temporary steel support;

[0024] Figure 6 Schematic diagram of a double-layer combined rotating bridge cantilever rotation;

[0025] Figure 7 : Schematic diagram of the double-layer combined rotating bridge in use;

[0026] The structure includes: 1. Main pier, 11. Main pier cap, 12. Main pier column base, 13. Main pier cap beam, 2. Steel truss beam, 21. Main truss diagonal member, 22. Top chord member, 3. Prestressed concrete beam, 4. Steel bridge deck, 5. Temporary piers, 51. Outermost row of temporary piers, 52. Middle row of temporary piers, 6. Temporary steel supports, 61. Steel support feet, 62. Top of steel support diagonal brace, 63. Steel support crossbeam, 64. Steel connecting beam, 7. Side piers. Detailed Implementation

[0027] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments given herein are only for illustration and explanation of the present invention and cannot be used to limit the present invention. The present invention will now be described in conjunction with an actual project of a continuous steel truss web-plate truss double-layer composite rotating bridge.

[0028] Referring to the attached drawings, a continuous steel truss-plate truss double-layer composite swing bridge adopts a T-shaped long cantilever continuous steel truss-plate truss composite structure, specifically using a 2×85m continuous steel truss-plate truss composite structure. The upper and lower bridge decks are arranged with a design elevation difference of 14.8m across the entire span. The lower layer uses ribbed prestressed concrete beams, which have three main beams arranged laterally. The upper layer uses steel truss beams, with three main trusses arranged laterally corresponding to the three main beams of the concrete beams, with a center distance of 18.35m. The main trusses are longitudinally Warren-type trusses, including main truss diagonal members and upper chord members. The span length is 14m, and the main truss height (distance between the upper and lower chord system lines) is 14.879m. Steel bridge decks are installed on the steel truss beams. Temporary supports are set in rows longitudinally at the steel truss nodes corresponding to the Warren-type main truss.

[0029] In actual construction, after the T-shaped long cantilever ribbed prestressed concrete beam structure has been fully poured and tensioned, all full-span scaffolding should be removed. When removing the scaffolding, it should be unloaded at multiple points and in stages to allow the cantilever structure to deflect naturally and completely. The longitudinal overturning stability of the cantilever structure must be guaranteed during the unloading process.

[0030] The temporary supports of the rotating bridge are removed in a symmetrical manner, starting from the main pier and moving towards both ends of the side piers, with one removed at a time. The outermost row of temporary supports is retained and will be removed after the temporary steel supports are installed.

[0031] The monitoring unit monitors the deformation of the bridge after each stage of support removal. Based on the alignment monitoring data, when the pressure value of the outermost row of temporary supports is close to zero when the beam is lowered by jacks, temporary steel supports for anti-overturning during the rotation are installed. Theoretically, the temporary steel supports are not subject to stress. In actual construction, when unbalanced bending moments occur at both ends of the rotating bridge, the temporary steel supports are subjected to stress to offset this part of the force, ensuring construction safety. After the temporary steel supports are installed, the outermost row of steel pipe concrete temporary supports is removed before the rotation.

[0032] The installation of temporary steel supports beside the main pier must ensure that these supports do not restrict the symmetrical deflection of the T-shaped long cantilever beam structure. The top of the temporary steel support's diagonal brace is equipped with a steel support beam, and the contact surface between the temporary steel support and the bottom of the rotating bridge beam is padded with a rubber sheet to ensure a tight, gapless fit between the temporary steel support and the beam bottom after the cantilever deflection is complete. The temporary steel support system only provides vertical support to the main beam of the rotating bridge; horizontal forces are borne by the steel connecting beams within the temporary steel support system.

[0033] In practice, large-diameter steel pipes are used for temporary steel support diagonal bracing rods, and I-beams are used for horizontal steel tie beams. Embedded parts are set during the construction of the main pier cap and main pier cover beam, and the main pier column base is set on the main pier cap.

[0034] During bridge rotation, the weight of the bridge beam is transferred to the upper ball joint through the piers, and then transferred to the lower ball joint and the abutment through the sliding plates between the ball joints. After the main structure of the bridge beam is completed, the empty sand box transfers the entire weight of the beam to the ball joints. Then, using the traction cable embedded in the upper turntable and the continuous rotation jacks, the dynamic friction torque between the upper and lower ball joints and between the support legs and the sliding track is overcome, allowing the bridge to rotate into place.

[0035] After all preparations are completed, the formal rotation will take place:

[0036] (1) After the trial rotation is completed, analyze the collected data, compile detailed data for controlling the rotation, and immediately carry out the formal rotation. The interval between the trial rotation and the formal rotation should not exceed 24 hours.

[0037] (2) Before the rotating structure is rotated, the personnel should be assigned to specific tasks. Based on each key part and construction link, the on-site personnel should be carefully deployed, each performing their duties and cooperating with each other. The on-site general commander should make unified arrangements.

[0038] (3) The hydraulic control system, key approvals, weather conditions, structures, etc. are all ready and meet the requirements for rotation. All personnel are in place. After receiving the rotation order from the project manager, the rotation personnel start the power system equipment and run it in automatic mode.

[0039] (4) During the operation of the equipment, all personnel must be highly focused and pay close attention to the operation of the power system equipment and the rotation of the bridge deck. Every 5m of the beam end is rotated, a report must be made to the project manager. Within 5m of the end point, a report must be made to the project manager every 1m of rotation. Within 40cm of the end point, a report must be made to the project manager every 2cm of rotation. Within 20cm, a report must be made every 1cm. Within 2cm, a report must be made every 1mm. This is so that the operators of the control system can keep abreast of the rotation and operate the control system to achieve the ideal design requirements.

[0040] (5) A 10mm PTFE plate is laid in the 30mm reserved gap between the inner ring balance foot and the embedded steel plate walking track on the top of the bearing platform as a balance walking track during the rotation. When the distance between the inner ring balance foot and the walking track changes due to unbalanced force or load during the rotation, a PTFE plate is inserted at the corresponding eccentric position to correct the eccentricity problem;

[0041] (6) When the rotating structure is close to the design position, i.e., the beam end is 50-80cm away from the design position (the distance from the design position needs to be calculated by the coefficient measured during the trial rotation), the system is paused; to prevent the structure from over-rotating, after the inertial operation is completed, the power system is changed from manual to jog operation to position; after each jog operation, the surveyor measures and reports the current status data of the axis movement once, and repeats the cycle until the structure axis is accurately positioned; throughout the entire rotation construction process, the total station is used to strengthen the monitoring of the elevation at both ends of the beam;

[0042] (7) During the rotation process, ensure continuity so that the key points before, during and after are connected to achieve the goal in one go, and try not to stop in the middle.

[0043] After the bridge is rotated and positioned, a total station is used for centerline correction, with an allowable centerline deviation of no more than 2 cm; selection of on-site positioning measurement scheme:

[0044] ① Central plumb bob control: Use a plumb bob to check whether the center of the beam end coincides with the center line of the side span;

[0045] ② Set up one total station on each side of the beam, set the line of sight of each instrument to the theoretical center of the beam, and then observe the rotation and positioning process.

[0046] ③ Place one level at each end of the beam to observe the elevation of the top of the beam after the beam ends are in place;

[0047] In practice, the above three schemes are adopted simultaneously, and the results of the three schemes are compared and verified.

[0048] After the beam is rotated into place, a temporary scaffold is used to support it and ensure the stability of the structure. The temporary outer side is completely enclosed with safety nets to prevent objects from falling, and a dedicated safety officer is assigned to provide protection.

[0049] After the rotating structure is precisely positioned, it is constrained and fixed. Jacks installed at the bottom of the turntable are used to precisely adjust the elevation of the beam ends, and measures are taken to shim the beam ends. Once the beam elevation is adjusted and the rotating structure is precisely positioned, it is then constrained and fixed.

[0050] After the turntable is precisely positioned, the sealing concrete pouring is immediately carried out to complete the consolidation of the turntable structure in the shortest possible time. The upper surface of the base is cleaned, the pre-reserved reinforcing bars are welded, the formwork is erected, and the sealing concrete is poured to connect the turntable and the lower turntable into one unit. The concrete slump is controlled to facilitate vibration and enhance the sealing effect.

[0051] After the formal rotation was completed, and after monitoring the plane position and elevation during the rotation and precise positioning stages, which all met the design requirements, steel wedges were immediately driven into the support legs and slides, and a steel reaction frame (with pre-positioned and embedded steel plates) was welded onto the lower turntable bearing platform for temporary locking.

[0052] Sealing the turntable: After temporary locking is completed and the rotating unit is ensured to no longer shift, the turntable is sealed as quickly as possible. The surface of the chassis is cleaned of dirt, the pre-installed pressure-reducing pipes are checked for blockage, the pre-installed reinforcing bars on the upper and lower turntables are welded, the formwork is installed, and safety pressure-reducing pipes are installed at the top of the four corners of the sealed turntable. Sealing concrete (micro-expansion concrete) is poured, and the concrete must be vibrated to ensure compaction, making the upper and lower turntables a single unit. Because grouting pipes and subsequent safety grouting pipes were pre-installed during the construction of the upper turntable, the same grade of grouting cement is used to fill the sealing concrete area between the upper and lower turntables to ensure its density.

[0053] After installing the supports and completing the paving stone pouring: Once the upper and lower turntables are permanently sealed after rotation, jacks are placed on the top surface of the lower cap beam of the side pier to lift the ends of each side of the main beam. The lifting force and displacement are controlled simultaneously, with the error to be within 5%. The lifting positions in the longitudinal direction are all within the range of the end crossbeams; the transverse lifting positions should be as close to the supports as possible. For the outer supports, four 600t jacks are placed within 2m of the side longitudinal beam on the end crossbeam. For the inner supports, two 400t jacks and two 300t jacks are placed within 1.5m of each side of the middle longitudinal beam on the end crossbeam.

[0054] When the jacking operation is carried out, jacks are used to apply vertical jacking force at the beam end. The jacking is carried out simultaneously at the large and small mileage beam ends, and the jacking is carried out simultaneously on the three main beams at the same beam end. The jacking force is applied at a uniform speed, slowly and synchronously.

[0055] During construction, construction monitoring should be strengthened, and a dual control system of jacking force and main beam elevation should be adopted, but the main beam elevation should be the primary control. When the jacking force reaches the design value, the elevation of the main beam at the beam end should be equal to the design elevation.

[0056] After the top is completed, a temporary compression support is set between the main beam and the side pier, with the top surface of the temporary support flush with the bottom of the beam;

[0057] The main beam side pier support pad is poured. After the pad reaches the design strength, the support is installed. After the support is installed, the temporary support and jacks are removed. The main beam is supported on the support, and the force transfer is completed.

Claims

1. A method for force conversion in a continuous steel truss web-plate truss double-layer composite rotating bridge, characterized in that: This double-layer composite rotating bridge adopts a T-shaped long cantilever continuous steel truss web-plate truss composite structure with the entire span arranged. The lower layer uses ribbed prestressed concrete beams, which have three main beams arranged laterally. The upper layer uses steel truss beams, with three main trusses arranged laterally corresponding to the three main beams of the concrete beams. The main trusses are longitudinally Warren-type trusses, including main truss diagonal members and upper chord members. Steel bridge decks are installed on the steel truss beams. Temporary piers are arranged in rows longitudinally corresponding to the Warren-type main truss steel truss nodes. The temporary piers are divided into the middle row of temporary piers and the outermost row of temporary piers. The outermost row of temporary piers uses a steel-concrete composite column pier structure. After the T-shaped long cantilever ribbed prestressed concrete beam structure is fully poured and tensioned, the full-span scaffolding is dismantled. During dismantling, the scaffolding should be unloaded at multiple points and in stages. Temporary supports are dismantled symmetrically, starting from the main pier and proceeding towards both ends, with one support removed at a time. The outermost row of temporary supports is retained until temporary steel supports are installed before further dismantling. The monitoring unit monitors the deformation after each stage of scaffolding and temporary support removal. Based on the alignment monitoring data, when the pressure value of the outermost row of temporary supports using jacks to lower the beam approaches zero, temporary anti-overturning steel supports are installed. This ensures the temporary supports are in place. Temporary steel supports are installed beside the main pier without restricting the symmetrical downward deflection of the T-shaped long cantilever beam structure. The top of the temporary steel support's diagonal brace is equipped with a steel support beam, and the contact surface with the beam bottom is padded with a rubber sheet to ensure tight contact between the temporary steel support and the beam bottom after the cantilever deflection is complete. The temporary steel support's diagonal brace uses large-diameter steel pipes, and the horizontal steel connecting beam uses steel pipes or I-beams for tie rods. Embedded parts are correspondingly installed during the construction of the main pier's foundation and main pier cap beam. The main pier's column base is located on the main pier's foundation. The outermost row of temporary supports is removed before the pier rotation after the temporary steel support construction is completed. The method for force conversion of the double-layer combined rotating bridge mainly includes the following steps: preparatory work should be completed before the rotation construction, the rotation is carried out, the rotation is in place, and after the formal rotation is completed, the plane position and elevation monitored during the rotation and precise positioning stages meet the design requirements, the turntable is temporarily locked and sealed, the supports are installed, the pad stones are poured, the main beam is supported on the supports, and the force conversion is completed.

2. The method for force conversion of a continuous steel truss web-plate truss double-layer composite rotating bridge according to claim 1, characterized in that: After the trial rotation is completed, analyze the collected data, compile detailed data for controlling the rotation, and immediately carry out the formal rotation. The interval between the trial rotation and the formal rotation should not exceed 24 hours.

3. The method for force conversion of a continuous steel truss web-plate truss double-layer composite rotating bridge according to claim 1, characterized in that: During the bridge rotation process, the beam end must report to the project manager every 5m, every 1m within 5m of the end point, every 2cm within 40cm of the end point, every 1cm within 20cm, and every 1mm within 2cm.

4. The method for force conversion of a continuous steel truss web-plate truss double-layer composite rotating bridge according to claim 1, characterized in that: After the bridge rotation is in place and the upper and lower turntables are permanently sealed, jacks are placed on the top surface of the lower cap beam of the side piers to lift the beam ends on each side of the main beam. The lifting force and displacement are controlled simultaneously, with the error to be controlled within 5%. The lifting positions in the longitudinal direction are all within the range of the end crossbeams. The transverse lifting positions should be as close to the supports as possible. For the outer supports, four 600t jacks are placed within 2m of the side longitudinal beam on the end crossbeam. For the inner supports, two 400t jacks and two 300t jacks are placed within 1.5m of the middle longitudinal beam on both sides of the end crossbeam. The jacks are used to lift the beam ends... Vertical jacking force is applied at the jacking point, with the jacking proceeding simultaneously at both the large and small mileage beam ends, and simultaneously on the three main beams at the same beam end. The jacking force is applied uniformly, slowly, and synchronously. During construction, construction monitoring is strengthened, and a dual control system of jacking force and main beam elevation is adopted, but the main beam elevation is the primary control. When the jacking force reaches the design value, the main beam elevation at the beam end is equal to the design elevation. After the jacking is completed, a temporary compression support is set between the main beam and the side pier, with the top surface of the temporary support flush with the bottom of the beam. The support pads for the main beam and side piers are poured, and after the pads reach the design strength, the supports are installed. After the supports are installed, the temporary supports and jacks are removed, and the main beam is supported on the supports, completing the force transfer.

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