Bridge construction method of first casting in place, then rotating and then pushing

Abstract

The invention discloses a bridge construction method with cast-in-place, rotation and pushing in sequence, and relates to the technical field of bridge construction. Comprising the following steps: S1, surveying and setting out; s2, existing line protection; s3, constructing a pile foundation and a bearing platform; s4, pier column and swivel structure construction; s5, the No.0 block is constructed; s6, construction of a suspended pouring section; s7, adjusting hanging basket equipment; s8, steel-concrete combined section construction; s9, bridge rotation; s10, pushing preparation is carried out; and S11, the steel box girder is installed through an incremental launching method. According to the invention, the two main spans which are far away from each other can be closed after the bridge is rotated, a pier does not need to be built between the two main spans, and the influence on the existing line during construction is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of bridge construction, and in particular to a bridge construction method that first casts in situ, then rotates, and then pushes. Background Art

[0002] With the development of society, the carrying capacity required for transportation has been continuously improved, and road interchanges have achieved rapid development. In order to reduce the impact of new bridge construction on the operation and safety of existing traffic under the bridge, bridge rotation construction technology has been widely used. Bridge rotation construction is to transform the construction on the upper part of the obstacle into construction on the shore or near the ground. The bridge is divided into two main spans with the mid-span as the boundary. The two main spans are rotated separately by the rotation system and closed at the mid-span. However, when there are two existing railway lines under the bridge or other reasons cause the obstacle to be wide, the distance between the two main spans after the rotation is too far to be directly closed. If bridge piers are built between the two main spans, it will affect the existing line. Summary of the invention

[0003] The main purpose of the present invention is to provide a bridge construction method which first casts in situ, then rotates, and then pushes, so as to solve the above-mentioned problems.

[0004] To achieve the above object, the present invention provides a bridge construction method of first casting in situ, then rotating, and then pushing, comprising the following steps:

[0005] S1. Measure and lay out the lines to determine the positions of the caps on both sides of the existing lines and the distances between the caps and the existing lines;

[0006] S2. Bored piles or Larsen steel sheet piles are installed between the cap and the existing wire to protect the existing wire;

[0007] S3. Construction of pile foundations and caps on both sides of the existing line;

[0008] S4. Carry out pier construction on the constructed cap, and install the rotating structure on the top of the pier;

[0009] S5. Set up a full-height bracket or a beam-column bracket beside the two piers and set up a No. 0 block formwork for cast-in-place construction of No. 0 block;

[0010] S6. Assemble the hanging basket equipment on the two No. 0 blocks, and use the hanging basket equipment to sequentially construct the suspended casting sections on both sides of the No. 0 block to complete the casting of the main span;

[0011] S7. Remove the bottom basket system of the hanging basket equipment and install the rear anchor, winch, lifting block and anchor pull ring of the hanging basket;

[0012] S8, transport the two steel-concrete combined sections to the bottom of the two adjacent ends of the main spans by a flatbed transport vehicle, anchor the anchor rings on the steel-concrete combined sections, hoist the steel-concrete combined sections to the ends of the main spans by a hanging basket device, and pour concrete;

[0013] S9, release the temporary consolidation of the rotating structure on the two piers, rotate the two main spans to the designated positions at the same time, and after the rotation is completed, block the rotating structure and fix the main spans;

[0014] S10. Remove the hanging basket equipment, install the jacking guide rails on the two cast bridge decks, and assemble the steel box girder and jacking platform on the bridge deck on one side;

[0015] S11. Push the assembled steel box girder to the predetermined position through the pushing platform and then remove the pushing guide rail. Then install the beam-dropping bracket, drop the steel box girder as a whole through the beam-dropping bracket and weld the steel box girder to connect the steel-concrete joint sections on both sides. After the connection is completed, remove the beam-dropping bracket.

[0016] Further, in step S5, the cast-in-place of block No. 0 is in the form of steel pipes and steel brackets, with a total of 4 rows of steel pipe columns, the bottom formwork is made of 15mm bamboo plywood, and the cross beams under the bamboo plywood are fully paved with 10×10cm square wood at intervals of 20cm; longitudinal beams are arranged under the cross beams, column top cross beams are arranged under the longitudinal beams, and 630×10mm steel pipe columns are arranged under the column top cross beams. The lateral spacing of the steel pipe columns is 2-3m, and the longitudinal spacing is 3.1m. The steel pipe columns are located on the pedestal, and the connecting pieces between the steel pipe columns are made of channel steel as scissors braces.

[0017] Furthermore, in step S5, during the construction of block 0, after the bottom formwork is assembled, the support is pre-stressed using prefabricated concrete blocks. The pre-stressing is performed in three levels, namely 60%, 100%, and 120% of the maximum construction load borne by the support.

[0018] Furthermore, in step S6, after the hanging basket equipment is assembled, a static load test is carried out on the hanging basket loaded with precast concrete blocks. The loading is carried out at four levels, namely 60%, 80%, 100% and 120% of the maximum construction load respectively. During the experiment, the settlement of the hanging basket is measured and compared with the theoretical value to provide a basis for the subsequent calculation of the hanging basket formwork elevation. After unloading, the rebound of the hanging basket is measured as the elastic deformation. The total settlement minus the elastic deformation is the measured inelastic deformation, which is compared and corrected with the calculated deformation. When pouring concrete, the pre-cast height value of the corresponding section to be poured is calculated according to the elastic deformation to control the elevation.

[0019] Furthermore, in step S8, the side spans of the two main spans away from the steel-concrete joint section are also constructed. The side span construction includes the following steps:

[0020] A1. Install the side span steel pipe bracket;

[0021] A2. Set up the distribution beam bottom formwork platform;

[0022] A3, bracket pre-compression;

[0023] A4, support formwork;

[0024] A5. Tie steel bars and install prestressed pipes;

[0025] A6. Concrete pouring and curing;

[0026] A7. Remove the inner and outer formworks and end formwork.

[0027] Furthermore, in step S9, before the rotation construction, the rotating part is weighed with a jack, and according to the measurement results and theoretical calculations, the weights at both ends are adjusted by adding sandbags on site to make the structural center of gravity of the rotating part coincide with the center of the rotating shaft as much as possible, and the eccentricity of the structure after counterweighting is controlled to be 5-10cm; after the counterweighting is completed, a trial run is carried out before the formal rotation, and the formal rotation construction is carried out after the trial run is completed and no abnormalities are found.

[0028] Furthermore, in step S9, after the rotation of the two main spans is completed, the side spans and the main spans are connected. The connection is constructed by cast-in-place support. When connecting, a counterweight is applied on one side and a stiffening frame is applied externally to lock the joint.

[0029] Furthermore, in step S1, a fence is set outside the roadbed of the existing line within the construction impact range. The fence uses 1.8m high concrete columns and metal mesh, and a barbed wire cage is set on the top of the fence.

[0030] The present invention uses a bridge rotation construction method to complete the construction of the main span of the bridge body on both sides of the existing line and rotate the two main spans to the same line above the existing line; the steel box girder is moved between the two main spans and the main spans are connected by a jacking method, and there is no need to build piers between the two main spans that are far apart, thereby reducing the impact on the existing line during construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The present invention is a flow chart of a bridge construction method of first casting in situ, then rotating and then jacking. DETAILED DESCRIPTION

[0032] In order to achieve the above-mentioned purpose and effect, the technical means and structures adopted by the present invention are described in detail with reference to the accompanying drawings for the features and functions of the preferred embodiments of the present invention.

[0033] like Figure 1 The present invention provides a bridge construction method of first casting in place, then rotating, and then pushing, comprising the following steps:

[0034] S1. Measure and lay out to determine the positions of the caps on both sides of the existing line and the distance between the caps and the existing line; set up fences on the outside of the roadbed of the existing line within the construction impact range. The fences are made of 1.8m high concrete columns and metal mesh, and a barbed wire cage is set on the top of the fence.

[0035] S2. Bored piles or Larsen steel sheet piles are installed between the cap and the existing wire to protect the existing wire;

[0036] S3. Construction of pile foundations and pedestals on both sides of the existing line; during pedestal construction, accurately embed the steel pipe column embedded parts required for subsequent construction to ensure the accuracy of the plane position of the steel pipe columns during subsequent construction.

[0037] S4. Carry out pier construction on the constructed foundation and install the rotating structure on the top of the pier. When constructing the pier body, accurately embed the wall connection parts required for subsequent construction to ensure reliable connection between the bracket and the pier body and enhance the stability of the bracket.

[0038] S5. Set up a full-height bracket or a beam-column bracket beside the two piers and set up a No. 0 block formwork for cast-in-place construction of No. 0 block;

[0039] Among them, the cast-in-place of block 0 adopts the form of steel pipe and steel support, with a total of 4 rows of steel pipe columns, the bottom formwork adopts 15mm bamboo plywood, and the crossbeam under the bamboo plywood adopts 10×10cm square wood with a full spacing of 20cm; a longitudinal beam is set under the crossbeam, using I20a welded slope adjustment truss, and 2I25a I-beam is set under the flange; a column top crossbeam is set under the longitudinal beam, which is 2I45b I-beam; 630×10mm steel pipe columns are set under the crossbeam of the 2I45b I-beam column top, and the horizontal spacing of the steel pipe columns is 2-3m, and the vertical spacing is 3.1m. The steel pipe columns are located on the pedestal, and the connecting parts between the steel pipe columns use No. 20 channel steel as scissors bracing. When installing the bracket, the bracket must be connected to the completed pier body through the wall connecting piece, and the vertical arrangement spacing of the wall connecting piece is not more than 3m to ensure that the overall stability of the bracket meets the requirements.

[0040] After the bottom formwork is assembled, the support is pre-pressed with concrete precast blocks. The size of the concrete precast blocks is 1.0×1.0×1.0m, and the weight of a single concrete precast block is 2.4t. The pre-pressing is carried out in three levels, which are 60%, 100%, and 120% of the maximum construction load borne by the support. The distribution of the pre-pressing load should be basically consistent with the distribution of the support construction load. The deviation of the loading weight should be controlled within ±5% of the same level of load. The pre-pressing loading and unloading of the support should be carried out in accordance with the principles of symmetry, layering, and grading. Concentrated loading and unloading are strictly prohibited. The loading sequence is from the pier top to the two ends in sequence, first pressurizing the bottom plate and web plate, and then pressurizing the flange plate. The settlement of the support is measured and recorded one hour after each level of loading is completed, and then observed every 6 hours until the settlement difference is less than 2mm for two consecutive times before the next level of loading can be carried out.

[0041] Block No. 0 is cast in one go, and the order of casting is base plate first, web plate, partition wall, and finally top plate. When casting the base plate, the pier top is cast first, and then it is cast symmetrically in layers from the middle to both sides and from low to high. A counter-pressure formwork is set at the chamfer of the web plate of the base plate to avoid honeycombing and other phenomena due to overflow of cement slurry at the connection between the base plate and the web plate and partition plate roots; the concrete of the web plate and partition wall is cast in horizontal layers with a layer thickness of 30 cm. Type 50 insert vibrator is mainly used for vibration; the top plate concrete is cast from one corner of the top plate to the other gradually, and the casting is completed in sequence.

[0042] S6. Assemble the hanging basket equipment on the two No. 0 blocks, and use the hanging basket equipment to sequentially construct the suspended casting sections on both sides of the No. 0 block to complete the casting of the main span;

[0043] Among them, after the hanging basket equipment is assembled, a static load test is carried out on the hanging basket loaded with precast concrete blocks to eliminate the inelastic deformation of the hanging basket and verify the bearing capacity of the hanging basket; loading and unloading are carried out in four levels, namely 60%, 80%, 100% and 120% of the maximum construction load, and the load duration is at least 60 minutes; during the experiment, the settlement of the hanging basket is measured and compared with the theoretical value to provide a basis for the subsequent calculation of the hanging basket formwork elevation; after unloading, the rebound of the hanging basket is measured as the elastic deformation, and the total settlement minus the elastic deformation is the measured inelastic deformation, which is compared and corrected with the calculated deformation. When pouring concrete, the pre-throw height value of the corresponding section to be poured is calculated according to the elastic deformation to control the elevation. The size of the precast concrete block is 1.0×1.0×1.0m, and the weight of a single block is 2.4t. The original elevation of the preloading basket is tested before loading. The deformation value of the hanging basket is measured 1 hour after each level of loading is completed. After all loading is completed, the deformation value of the hanging basket is measured every 1 hour. The preloading is continuous for 4 hours. When the difference between the two deformations in the last measurement time period is less than 2mm, it can be ended. The unloading process is unloaded step by step according to the same weight of graded loading and the deformation after unloading at each level is measured. According to the measured data of loading and unloading, the deformation curves of the hanging basket during loading and unloading are drawn. The deformation values ​​of the hanging basket under the action of each stage are analyzed and calculated to provide a basis for subsequent construction control.

[0044] S7. Remove the bottom basket system of the hanging basket equipment and install the rear anchor of the hanging basket, the winch and the lifting pulley required for lifting the steel box girder;

[0045] S8. Use a flatbed transport vehicle to transport the two steel-concrete joint sections to the bottom of the two adjacent ends of the main spans, anchor the anchor rings on the steel-concrete joint sections, connect the lifting pulley to the anchor rings, and use the hanging basket equipment to lift the steel-concrete joint sections to the ends of the main spans, preparing to install the steel-concrete joint sections on the suspended casting sections.

[0046] Before installation, weld the steel bars to the top and bottom plates of the steel grid of the steel-concrete joint section, then insert the steel bars of the suspended cast section into the reserved holes in the steel plate of the steel-concrete joint section and weld them to the steel bars in the steel grid. The welding length is 200mm and the welding joints are staggered.

[0047] After the steel bars are installed, C50 slightly expansive concrete is poured into the steel grid room. The gap between the steel beam and the concrete is sealed and reinforced with bamboo plywood and back ribs. The bamboo plywood is 15mm and the back ribs are 10×10cm square wood.

[0048] After the steel-concrete joint section is completed, the side spans on both sides of the main span are constructed. The side span construction includes the following steps:

[0049] A1. Install the side span steel pipe bracket;

[0050] A2. Set up the distribution beam bottom formwork platform;

[0051] A3, bracket pre-compression;

[0052] A4, support formwork;

[0053] A5. Tie steel bars and install prestressed pipes;

[0054] A6. Concrete pouring and curing;

[0055] A7. Remove the inner and outer formworks and end formwork.

[0056] Before the construction of the side span, the foundation area of ​​the side span is measured and the excavation edge line is excavated along the foundation area. After excavation, dynamic penetration testing of the foundation is carried out. When the bearing capacity of the base is not met, replacement treatment is required. After replacement, each layer is compacted. The bearing capacity after compaction is not less than the bearing capacity requirement of the designed support foundation. After the acceptance of the base, reinforced concrete strip foundation construction is carried out. In order to prevent uneven sinking of the base caused by rainwater immersion, the backfill soil of the support ground is 0.5m higher than the natural ground and drainage ditches are set around the foundation. The drainage ditches on the support ground are manually compacted and leveled to ensure smooth drainage.

[0057] S9. Release the temporary consolidation of the rotating structure on the two piers, rotate the two main spans to the designated positions at the same time, and after the rotation is completed, block the rotating structure and fix the main spans.

[0058] Among them, the temporary supports on the rotating structure are removed first. After the temporary supports of the rotating structure are removed, a comprehensive inspection is carried out to check whether there are cracks and abnormal conditions in the key stress-bearing parts of the rotating structure. After the temporary supports are removed, the observation and monitoring time of the rotating structure must reach more than 2 hours.

[0059] After confirming that there are no cracks or other abnormal conditions, use a jack to weigh the rotating part, and based on the measurement results and theoretical calculations, use the on-site sandbag counterweight method to adjust the weights at both ends so that the structural center of gravity of the rotating part coincides with the center of the rotating axis as much as possible. After counterweighting, the eccentricity of the structure is controlled at 5-10cm; then install steel limit devices at the horizontal rotation positions on the side spans on both sides to prevent the rotation from exceeding the limit.

[0060] Then remove the temporary consolidation and lubricate the slideway again to ensure that the resistance on the slideway is at the minimum state, and then conduct a trial run. During the trial run, check whether the rotating structure is balanced and stable, whether there are any faults, and whether cracks occur in the key stress-bearing parts. If there are any abnormalities, the trial run should be stopped, and the cause should be found out and corresponding measures should be taken to rectify the situation before continuing the trial run. After the trial run is completed and there are no abnormalities, the formal rotation construction can be started.

[0061] Before the formal rotation, the rotating structure is left to stand for 24 hours, and various measurement data are reported to the monitoring group to confirm whether it is in a balanced state. After inspection, the rotation construction begins. During construction, the traction jack is tensioned synchronously, and when the tonnage reaches the calculated dynamic friction resistance, the force is applied in stages, with 100KN as the first level, until the horizontal displacement of the support walkway on the rotating structure is observed. The rotation is confirmed to have started, and the static friction resistance is recorded. After rotation, the force is reduced in stages, with 100KN as the first level, until the normal speed is ≤0.02rad / min. During rotation, the machine should rotate at a uniform speed and the angular velocity w≤0.02rad / min; the horizontal line velocity v≤1.0m / min at the end of the main beam; to ensure that the rotation process is smooth and safe, start to decelerate after the horizontal rotation is basically in place (about 1.5m from the design position), reduce the horizontal rotation speed, and take jog operation after reaching 1m from the design position, and cooperate with the surveying personnel to confirm the arc length of the beam end after jog, stop at 0.1m from the design position, measure the axis, and accurately jog control the positioning according to the difference to prevent over-rotation; after the rotation is in place, first use steel wedges to lock the upper and lower turntables of the rotating structure, use jacks to adjust the elevation of the beam ends and use steel wedges to pad, and then complete the consolidation of the upper and lower pedestals.

[0062] After the rotation construction is completed, the main span and the side spans on both sides are connected. The connection is constructed by cast-in-place support. Before the connection, counterweights are applied to the beam ends of the main span to ensure that the elevations of the ends of the connected beams are the same and to avoid deformation of the joints when pouring concrete. The two ends of the connection are locked by a rigid frame and temporary prestressed tendons.

[0063] S10. Remove the hanging basket equipment. To reduce the safety risk of the existing line during the removal, move the hanging basket back 3 sections. The removal of the hanging basket is carried out symmetrically at the two cantilever ends of the continuous beam to balance the force on the continuous beam and ensure construction safety. After the removal is completed, install the jacking guide rails on the two cast bridge decks, and assemble the steel box beam, guide beam and jacking platform on the bridge deck on one side; the jacking platform is set on the concrete beam and steel-concrete joint section on the small pile number side, and the jacking direction is from the small pile number to the large pile number.

[0064] S11. After the overall assembly of the steel box girder on the on-site assembly platform is completed, the sliding jacking method is used to pull the fine-rolled threaded steel bar through the tensioning jack, and the beam section is dragged to slide on the slideway set on the concrete beam, and the traction beam body is installed in place. In order to ensure construction safety, meet the anti-overturning requirements of the steel box girder, facilitate the jacking operation of the starting segment steel beam, and reduce the cantilever length of the steel beam itself and the stress during construction, a front guide beam is set at the front end of the steel box girder and a rear guide beam is set at the rear end.

[0065] The jacking is carried out three times. After the first jacking, the steel box girder and the rear guide girder are located on the bridge deck with a small pile number, and the front end of the front guide girder is suspended; after the second jacking, the front end of the front guide girder is located on the bridge deck with a large pile number, the rear end of the front guide girder and the front end of the steel box girder are suspended, and the rear end of the steel box girder and the rear guide girder are located on the bridge deck with a small pile number; after the third jacking, the steel box girder reaches the preset position and the jacking is completed. At this time, the front guide girder is located on the bridge deck with a large pile number, the rear guide girder is located on the bridge deck with a small pile number, and the steel box girder is suspended. Then remove the front guide girder and the rear guide girder, install the beam drop bracket, and use the beam drop bracket to drop the steel box girder to the specified position to connect with the steel-concrete joint section at both ends of the steel box girder.

[0066] After the steel box girder is closed, the beam support is removed and other debris is cleaned up, and the steel beam is fully inspected and partially painted. Then a 200t crawler crane is used to lift two 36t forklifts to the bridge deck, and then a forklift is used to install the prefabricated bridge deck from both ends to the middle of the span. During the construction process, the 200t crawler crane cooperates to lift the prefabricated bridge deck from the ground to the bridge deck. All lifting operations must be carried out in the construction skylight.

[0067] The above descriptions are only preferred embodiments of the present invention, not all embodiments. Anyone should be aware that any structural changes made under the inspiration of the present invention, and any technical solutions that are the same or similar to the present invention, belong to the protection scope of the present invention.

Claims

1. A bridge construction method of first casting in place, then rotating, and then pushing, characterized in that: The following steps are involved: S1. Measure and lay out the lines to determine the positions of the caps on both sides of the existing lines and the distance between the caps and the existing lines; S2. Bored piles or Larsen steel sheet piles are installed between the cap and the existing wire to protect the existing wire; S3. Construction of pile foundations and caps on both sides of the existing line; S4. Carry out pier construction on the constructed cap, and install the rotating structure on the top of the pier; S5. Set up a full-height bracket or a beam-column bracket beside the two piers and set up a No. 0 block formwork for cast-in-place construction of No. 0 block; S6. Assemble the hanging basket equipment on the two No. 0 blocks, and use the hanging basket equipment to sequentially construct the suspended casting sections on both sides of the No. 0 block to complete the casting of the main span; S7. Remove the bottom basket system of the hanging basket equipment and install the rear anchor, winch, lifting block and anchor pull ring of the hanging basket; S8, transport the two steel-concrete combined sections to the bottom of the two adjacent ends of the main spans by a flatbed transport vehicle, anchor the anchor rings on the steel-concrete combined sections, hoist the steel-concrete combined sections to the ends of the main spans by a hanging basket device, and pour concrete; S9, release the temporary consolidation of the rotating structure on the two piers, rotate the two main spans to the designated positions at the same time, and after the rotation is completed, block the rotating structure and fix the main spans; S10. Remove the hanging basket equipment, install the jacking guide rails on the two cast bridge decks, and assemble the steel box girder and jacking platform on the bridge deck on one side; S11. Push the assembled steel box girder to the predetermined position through the pushing platform and then remove the pushing guide rail. Then install the beam-dropping bracket, drop the steel box girder as a whole through the beam-dropping bracket and weld the steel box girder to connect the steel-concrete joint sections on both sides. After the connection is completed, remove the beam-dropping bracket.

2. A bridge construction method of first casting in situ, then rotating, and then pushing as claimed in claim 1, characterized in that: In step S5, the cast-in-place of block No. 0 is in the form of steel pipes and steel brackets, with a total of 4 rows of steel pipe columns. The bottom formwork is made of 15mm bamboo plywood, and the cross beams under the bamboo plywood are fully paved with 10×10cm square wood at intervals of 20cm; longitudinal beams are arranged under the cross beams, and column top cross beams are arranged under the longitudinal beams. Under the column top cross beams are 630×10mm steel pipe columns, and the horizontal spacing of the steel pipe columns is 2-3m, and the vertical spacing is 3.1m. The steel pipe columns are located on the pedestal, and the connecting parts between the steel pipe columns are made of channel steel as scissors braces.

3. A bridge construction method of first casting in situ, then rotating, and then pushing as claimed in claim 1, characterized in that: In step S5, during the construction of block 0, after the bottom formwork is assembled, the support is pre-pressed using prefabricated concrete blocks. The pre-pressing is performed in three levels, namely 60%, 100%, and 120% of the maximum construction load borne by the support.

4. A bridge construction method of first casting in situ, then rotating, and then pushing as claimed in claim 3, characterized in that: In step S6, after the hanging basket equipment is assembled, a static load test is carried out on the hanging basket loaded with precast concrete blocks. The loading is carried out at four levels, namely 60%, 80%, 100% and 120% of the maximum construction load. During the experiment, the settlement of the hanging basket is measured and compared with the theoretical value to provide a basis for the subsequent calculation of the hanging basket formwork elevation. After unloading, the rebound of the hanging basket is measured as the elastic deformation. The total settlement minus the elastic deformation is the measured inelastic deformation, which is compared and corrected with the calculated deformation. When pouring concrete, the pre-cast height value of the corresponding section to be poured is calculated according to the elastic deformation to control the elevation.

5. The method for constructing a bridge by first casting in situ, then rotating, and then pushing as claimed in claim 1, characterized in that: In step S8, the side spans of the two main spans away from the steel-concrete joint section are also constructed. The side span construction includes the following steps: A1. Install the side span steel pipe bracket; A2. Set up the distribution beam bottom formwork platform; A3, bracket pre-compression; A4, support formwork; A5. Tie steel bars and install prestressed pipes; A6. Concrete pouring and curing; A7. Remove the inner and outer formworks and end formwork.

6. A bridge construction method of first casting in situ, then rotating, and then pushing as claimed in claim 5, characterized in that: In step S9, before the rotation construction, the rotating part is weighed with a jack, and according to the measurement results and theoretical calculations, the weights at both ends are adjusted by adding sandbags on site to make the structural center of gravity of the rotating part coincide with the center of the rotating shaft as much as possible, and the eccentricity of the structure after counterweighting is controlled at 5-10cm; after the counterweighting is completed, a trial run is carried out before the formal rotation, and the formal rotation construction is carried out after the trial run is completed and no abnormalities are found.

7. A bridge construction method of first casting in situ, then rotating, and then pushing as claimed in claim 6, characterized in that: In step S9, after the rotation of the two main spans is completed, the side spans and the main spans are connected. The connection is constructed by cast-in-place support. When connecting, a counterweight is applied on one side and a stiffening frame is applied externally to lock the joint.

8. A bridge construction method of first casting in situ, then rotating, and then pushing as claimed in any one of claims 1 to 7, characterized in that: In step S1, a fence is set outside the roadbed of the existing line within the construction impact range. The fence is made of 1.8m high concrete columns and metal mesh, and a barbed wire cage is set on the top of the fence.

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