Assembly type side box composite beam bridge position modularization suspended splicing construction method

Abstract

The invention relates to an assembly type side box composite beam bridge location modular suspended splicing construction method. The method comprises a single-segment construction method, wherein the single-segment construction method comprises the steps of S100, construction preparation, S200, side main beam installation, S300, cross beam installation, S400, small longitudinal beam installation, S500, segment measurement and adjustment, S600, high-strength bolt construction, S700, side main beam top plate welding, S800, anticorrosive paint coating, S900, stay cable hanging and initial tensioning and S1000, bridge deck slab hoisting. The steel beam segments are divided into a plurality of modules which can be spliced and connected, such as the side main beams, the cross beams and the small longitudinal beams, and are temporarily fixed through hoisting alignment and temporary bolts, so that segment measurement and overall adjustment can be uniformly implemented after the side main beams, the cross beams and the small longitudinal beams are spliced, and the linear control precision and the overall splicing stability are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of side box composite beam technology, and specifically to a modular cantilever construction method for prefabricated side box composite beam bridge sites. Background Technology

[0002] In modern transportation infrastructure construction, bridge engineering is a key node, and the innovation and development of its construction technology is of paramount importance. The side-box steel-concrete composite girder, with its unique structural advantages such as high bending and torsional stiffness and good economic efficiency, has been widely used in the construction of long-span bridges.

[0003] However, with the continuous increase in bridge span and width, the construction difficulty has significantly increased. Taking an ultra-wide double-sided box girder with a width exceeding 45 m as an example, it is no longer feasible to transport the steel beam as a whole. It is usually necessary to disassemble it into several modular components after manufacturing in the factory, transport them to the bridge site, and then assemble them segment by segment. However, due to the large number of components and the large span, conventional point-by-point installation and local correction can easily lead to difficulty in ensuring overall accuracy and large cumulative errors. Furthermore, fixing the nodes too early will limit the space for subsequent overall adjustments, ultimately affecting the alignment control of the segments and the overall stability. This places extremely strict requirements on the accuracy of on-site hoisting and the reliability of component docking. At the same time, it also faces significant challenges in the construction quality of high-strength bolts, the control of welding deformation at nodes, and the synchronous installation of bridge decks.

[0004] Therefore, it is necessary to study a modular cantilever construction method for prefabricated side box composite beam bridge sites. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a modular cantilever construction method for prefabricated side box girder bridge sites, which can effectively solve the problems of insufficient accuracy, error accumulation, and impact on segment alignment control and overall stability caused by point-by-point installation, correction and fixing in the modular assembly construction of ultra-wide double-sided box girder bridges.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A modular cantilever construction method for prefabricated side box composite beam bridge sites includes a single-segment construction method: S100: Construction Preparation The full-slewing crane is in place; each steel beam is pre-assembled and transported to the bridge site; the top of the side main beam is not sealed, and splicing seats are pre-installed on the side main beam; S200: Side main beam installation The two sets of side main beams are installed in sequence; the side main beams are lifted to their installation positions using a full-rotation crane, so that the side main beam segment to be installed is aligned with the previous erected side main beam segment. After checking and adjusting the position, temporary bolts are used for fixing. S300: Beam Installation The crossbeams were hoisted to the installation position using a full-rotation crane, positioning them between the two sets of side main beams. After verifying and adjusting their positions, temporary bolts were used to fix the ends of the crossbeams to the side main beams. The crossbeams were then installed sequentially at intervals along the bridge construction direction. S400: Installation of small longitudinal beams The small longitudinal beams were hoisted to the installation position using a full-rotation crane. After the position was checked and adjusted, the ends of the crossbeams were fixed to the side main beams using temporary bolts. Several small longitudinal beams were fixed between two adjacent crossbeams in sequence. S500: Segment measurement and adjustment After a segment of steel beam is assembled, the position of the steel beam is measured and checked to control the axial deviation, upstream and downstream elevation difference and longitudinal slope of the steel beam; S600: High-strength bolt installation The steel beams are fixed with high-strength bolts in the order of main beams, crossbeams, and small longitudinal beams, and temporary bolts are replaced with high-strength bolts; the tightening is carried out in the order of initial tightening, secondary tightening and final tightening. S700: Welding of the top plate of the side main beam After the high-strength bolts of the side main beam are finally tightened, a top plate is welded onto the side main beam to seal it. S800: Anti-corrosion paint coating Roller coating / high-pressure spraying is used to apply anti-corrosion topcoat to the welded areas of steel beams and the tightened areas of high-strength bolts; S900: Cable-stayed cable installation and initial tensioning The stay cables are installed using the tower top gantry and the high tower cable threading machine. The initial tensioning of the stay cables is carried out simultaneously and symmetrically in the upstream and downstream, side and middle spans. S1000: Bridge deck hoisting Using a full-slewing crane, the bridge panels were lifted one by one to the installation position, ensuring that the exposed steel bars of the bridge panels did not conflict with the shear studs on the top surface of the steel beams. The exposed steel bars of the bridge panels were temporarily connected to some of the shear studs to fix the bridge panels.

[0007] Furthermore, after the first segment is completed, repeat steps S200-S1000 to continuously construct the second segment; After the second segment is completed, the following steps will be performed: S1100: Construction of wet joints Stirrups, main bars, and tie bars are installed between the two sections to form a complete steel reinforcement cage. Formwork is then erected and concrete is poured for the wet joint. S1200: Two double-segment cable stays After the wet joint construction is completed, the alignment and load distribution of the main beam are monitored, and the cable tension of the stay cables is readjusted. S1300: Crane moved forward; Once the wet joint strength meets the requirements, the crane moves forward to the next work station, and the above steps are repeated to construct the next two sections.

[0008] Furthermore, the side main beam includes a supporting frame, a bottom plate, a web plate, and a top plate; The bottom plate, web plate and top plate are joined together to form a side box structure that runs through the front and back. The supporting frame surrounds and is fixed to the inner surface of the side box structure. Multiple sets of supporting frames are arranged at intervals along the length of the side main beam.

[0009] Furthermore, a splicing seat is fixedly connected to the side of the main beam near the crossbeam, and the splicing seat has a splicing groove that runs vertically through the beam and faces the opening of the crossbeam. Both ends of the crossbeam are fixedly connected to splicing plates extending toward the side main beam. The splicing plates are located in splicing grooves. The high-strength bolts pass vertically through the splicing base and the splicing plates to fix the crossbeam and the side main beam together. In step S300, the crossbeam is first hoisted vertically above the splicing seat at the installation position, then slowly lowered vertically and fixed with temporary bolts.

[0010] Furthermore, the splicing base includes a base plate, a bottom support plate, and a connecting plate; The base plate is vertically fixed to one side of the main beam near the crossbeam, and the bottom support plate is horizontally fixed to the bottom of the base plate. The bottom support plate extends to the bottom of the main beam and is fixedly connected to the bottom plate of the main beam. Two sets of connecting plates are vertically fixed to the base plate, and a splicing groove is formed between the two sets of connecting plates.

[0011] Furthermore, the splicing base corresponds to the position of the support frame, and the bottom plate and the base plate are fixedly connected to the support frame by high-strength bolts.

[0012] Furthermore, multiple sets of docking grooves are provided at intervals at one end of the bottom plate and the web plate; multiple sets of docking plates are fixed at the other end of the bottom plate and the web plate, and several fixing holes are correspondingly opened on the bottom of the docking groove and the docking plate.

[0013] Furthermore, a nail plate is fixed to the top of the splicing base, and several shear nails are present on the top of the crossbeam, the top of the nail plate, and the top of the top plate.

[0014] Furthermore, in step S600, the final tightening torque of the high-strength bolt is calculated through the following steps: S610: Conduct torque coefficient testing on multiple batches of high-strength bolts entering the construction site and obtain the test results for each batch; S620: Perform statistical processing on the test results to obtain the average torque coefficient across batches under the temperature and humidity conditions at the construction site; S630: Calculate the reference torque coefficient based on the temperature and humidity conditions at the construction site, and use this to verify the average torque coefficient; S640: After calibrating the electric wrench on the axial force-torque meter, calculate and determine the final tightening torque value of the high-strength bolts used that day based on the verified average torque coefficient.

[0015] Furthermore, the reference torque coefficient at various temperatures is calculated using the following proportionality coefficient formula: Phosphated bolts: ; Phosphated bolts: ; Where: T is temperature (degrees Celsius), and V is relative humidity (%).

[0016] The beneficial effects of the above technical solution are: (1) The present invention divides the steel beam segment into multiple modules such as side main beam, cross beam, and small longitudinal beam that can be spliced ​​and connected. By hoisting and positioning and using temporary bolts for temporary fixation, the rigid locking caused by point welding or direct final tightening can be avoided, thus preserving the overall adjustment space. This allows for unified segment measurement and overall adjustment after the side main beam, cross beam, and small longitudinal beam are assembled. It can effectively control the axis deviation, longitudinal slope, and height difference, and reduce the amplification effect of local error accumulation on the overall alignment. It can effectively solve the problem that point installation, correction, and fixation in the modular assembly construction of ultra-wide double-sided box girder will lead to insufficient accuracy, error accumulation, and affect the alignment control and overall stability of the segment. It significantly improves the accuracy of alignment control and the stability of the overall assembly.

[0017] (2) In this invention, a splicing seat is pre-installed on the side of the main beam near the crossbeam, and splicing plates are installed at both ends of the crossbeam. The splicing plates can be inserted into the splicing slots of the splicing seat to achieve rapid positioning, enabling the crossbeam to be quickly aligned and guided during hoisting and lowering. This avoids the tedious operation of repeatedly adjusting the ends of the crossbeam in the air, improving installation accuracy and construction efficiency. At the same time, after the splicing plates are inserted into the splicing slots, temporary bolts can be used for transitional fixation. While ensuring the stable positioning of the crossbeam, it still leaves room for subsequent overall measurement and adjustment, thus taking into account both the needs of rapid installation and subsequent accuracy control.

[0018] (3) This invention performs torque coefficient testing on multiple batches of high-strength bolts entering the construction site. Based on the verified average torque coefficient, the final tightening torque value of the high-strength bolts used on that day is calculated and determined. This eliminates the randomness of the friction characteristics of a single batch of bolts and improves the representativeness of the tightening parameters. In addition, the average value is checked under temperature and humidity conditions with reference to the torque coefficient, avoiding the accumulation of deviations caused by environmental changes. This ensures the scientificity and accuracy of the final tightening torque value of the high-strength bolts, significantly improves the uniformity of the stress on the bolt connection and the stability of the construction quality, thereby improving the accuracy and safety of the overall assembly segment. Attached Figure Description

[0019] Figure 1 This is a flowchart of the method of the present invention; Figure 2 A top view of the segmented assembly; Figure 3 A 3D schematic diagram of the splicing node between the main beam and the crossbeam; Figure 4 A 3D view of the splicing node between the main beam and the crossbeam from another perspective; Figure 5 A 3D view of the splicing node between the main beam and the crossbeam from a bottom-up perspective; Figure 6 This is a front view of the splicing node between the main beam and the crossbeam; Figure 7 This is a top view of the splicing node between the main beam and the crossbeam.

[0020] Reference numerals: 1. Side main beam; 2. Crossbeam; 3. Splice seat; 4. Small longitudinal beam; 5. Nail plate; 6. Shear nail; 101. Support frame; 102. Base plate; 103. Web plate; 104. Top plate; 105. Butt joint groove; 106. Butt joint plate; 201. Splice plate; 301. Splice joint groove; 302. Base plate; 303. Bottom support plate; 304. Connecting plate. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: This embodiment aims to provide a modular cantilever construction method for prefabricated side box composite beam bridge sites, which is mainly used for the construction of ultra-wide double-sided box steel-concrete composite beams for double-tower double-cable-stayed bridges. It addresses the problem that point-by-point installation, correction and fixing in the modular assembly construction of ultra-wide double-sided box composite beams can lead to insufficient accuracy, error accumulation and affect the alignment control and overall stability of segments.

[0022] This embodiment aims to provide a modular cantilever construction method for prefabricated side box composite beam bridge sites, including a single-segment construction method, which includes the following steps: S100: Construction Preparation Based on the structural characteristics and transportation conditions of the steel beams, the steel beams are disassembled into suitable components. By optimizing the transportation route and selecting appropriate transport vehicles and fixing methods, the safety and integrity of the steel beams during transportation are ensured, so that each component can be transported to the bridge site.

[0023] like Figure 2 The steel beam components include at least the side main beam 1, the crossbeam 2, and the small longitudinal beam 4. Each component is pre-assembled at the bridge site. The top of the side main beam 1 is not sealed to facilitate worker access for construction. The splicing seat 3 is pre-installed on the side main beam 1 and is used to connect the crossbeam 2 and the side main beam 1.

[0024] like Figure 3-7 A splicing seat 3 is fixedly connected to the side of the main beam 1 near the crossbeam 2. The splicing seat 3 has a splicing groove 301 that runs vertically through the beam and opens towards the crossbeam 2. Specifically, the splicing seat 3 includes a base plate 302, a bottom support plate 303, and a connecting plate 304. The base plate 302 is vertically fixed to the side of the main beam 1 near the crossbeam 2, and the bottom support plate 303 is horizontally fixed to the bottom of the base plate 302. The bottom support plate 303 extends to the bottom of the main beam 1 and is fixedly connected to the bottom plate 102 of the main beam 1. Two sets of connecting plates 304 are vertically fixedly connected to the base plate 302, and the splicing groove 301 is formed between the two sets of connecting plates 304.

[0025] The full-rotation crane is positioned to lift the assembled steel beam components. A reasonable lifting plan is formulated based on the weight, size, and installation location of the steel beams. Through precise measurement and positioning, the steel beams are accurately positioned.

[0026] S200: Installation of Side Main Beam 1 The first segment of the side main girder was transported from the steel structure factory to the bridge site by a girder transport vehicle. The side main girder was lifted using a full-rotation crane. Two 50m long guy ropes were set up during each lifting to control the direction of rotation in the air and avoid collisions with the installed components.

[0027] Each segment has two side main beams 1, and the two sets of side main beams 1 are installed sequentially. For example... Figure 3 and Figure 4 (Top plate 104 not shown) The side main beam 1 includes a support frame 101, a bottom plate 102, a web plate 103 and a top plate 104; the bottom plate 102, the web plate 103 and the top plate 104 can be joined together to form a side box structure that runs through the front and back. The support frame 101 surrounds and is fixed to the inner surface of the side box structure. Three sets of support frames 101 are arranged at intervals along the length of the side main beam 1 to provide internal support and improve the stability of the structure.

[0028] The splicing base 3 corresponds to the support frame 101, wherein the bottom support plate 303 and the base plate 302 are fixedly connected to the support frame 101 by high-strength bolts.

[0029] Multiple sets of mating grooves 105 are provided at intervals at one end of the base plate 102 and the web plate 103. Specifically, multiple ribs are fixed at intervals along the cross-sectional contour of the base plate 102 and the web plate 103, and mating grooves 105 are formed between adjacent ribs. Multiple sets of mating plates 106 are bolted to the other end of the base plate 102 and the web plate 103. Several fixing holes are correspondingly opened on the bottom of the mating groove 105 and the mating plate 106 to facilitate bolt fixing.

[0030] During installation, a full-slewing crane is used to lift the side main beam 1 to the installation position, so that the side main beam 1 of the segment to be installed is aligned with the side main beam 1 of the previous erected segment. The connecting plate 106 of the side main beam 1 of the segment to be installed is inserted into the connecting groove 105 of the side main beam 1 of the previous erected segment.

[0031] During the docking process, the axial deviation, planar position, and longitudinal slope of the side main beam 1 were strictly controlled. The position of the side main beam 1 was adjusted by hand-operated hoists, and the axis and alignment of the side main beam 1 were verified by total station to meet the design requirements. The position was then checked and adjusted.

[0032] After verification and adjustment, temporary fixing is carried out. Temporary bolts or 50% punchings are installed in the order of web plate 103 first and bottom plate 102. The number of temporary bolts should be sufficient to ensure close contact between the surface of connecting plate 304 and the surface of component plate, and there should be no less than 2.

[0033] S300: Installation of crossbeam 2 Both ends of the crossbeam 2 are fixedly connected to splicing plates 201 extending towards the side main beam 1. A full-rotation crane is used to hoist the crossbeam 2 to the installation position, positioning it between the two sets of side main beams 1. The crossbeam 2 can first be hoisted vertically above the splicing seat 3 at the installation position, and then slowly lowered vertically, positioning the splicing plate 201 in the splicing groove 301, aligning the holes of the splicing plate 201 with the holes of the splicing seat 3. Figure 2 Three sets of crossbeams 2 are installed sequentially at intervals along the bridge construction direction. Crossbeams 2 are hoisted and installed one at a time along the construction direction. Two 50m long guy ropes are set up each time they are hoisted to control the direction of rotation in the air and avoid collision with the installed components.

[0034] After adjusting the position of the side main beam 1 using a hand-operated hoist and verifying the plane position and elevation of the crossbeam 2 to meet the design requirements using a total station, use temporary bolts to vertically pass through the splicing seat 3 and splicing plate 201 to fix the crossbeam 2 and the side main beam 1. The number of temporary bolts should be sufficient to ensure a close fit between the surface of the connecting plate 304 and the surface of the component, and should be no less than 2.

[0035] S400: Installation of small longitudinal beam 4 Using a full-rotation crane, the small longitudinal beams 4 are hoisted to the installation position in sequence. After checking and adjusting the position, temporary bolts are used to fix the end of the crossbeam 2 to the side main beam 1. Multiple small longitudinal beams 4 are fixed between two adjacent crossbeams 2 in sequence, forming a mesh-like skeleton structure with the crossbeams 2.

[0036] S500: Segment measurement and adjustment After a steel beam segment is assembled, its position is measured and verified to control axial deviation, upstream and downstream elevation difference, and longitudinal slope. Segment elevation can be adjusted using a crane, and axial deviation can be adjusted using wire ropes and chain hoists. The previous steel beam segment can be used as a fixed point for diagonal adjustment of the newly erected segment. After adjustment, the newly erected segment is remeasured, and only after meeting the requirements can the next process proceed.

[0037] S600: High-strength bolt installation The steel beams are fixed with high-strength bolts in the order of main beam 1, crossbeam 2, and small longitudinal beam 4, and the temporary bolts are replaced with high-strength bolts. The tightening is carried out in the order of initial tightening, secondary tightening and final tightening.

[0038] To facilitate construction management and reduce the variety of torque values ​​that need to be verified by electric wrenches at the same time or construction site, when the on-site verification data of the torque coefficient of high-strength bolts is stable, the torque coefficients of several batches of high-strength bolts can be statistically analyzed. If the average value K of the torque coefficient is within the range of 0.11 to 0.15 and the standard deviation S ≤ 0.01, the average value K of the torque coefficients of these batches of high-strength bolts can be used as the basis for determining the construction torque and a final tightening torque can be determined.

[0039] Specifically, the final tightening torque of a high-strength bolt can be calculated using the following steps: S610: Torque coefficient tests are performed on multiple batches of high-strength bolts entering the construction site to obtain the test results for each batch. The tested high-strength bolts are those used in the construction on that day.

[0040] S620: Perform statistical processing on the test results to obtain the average torque coefficient across batches under the temperature and humidity conditions at the construction site.

[0041] S630: Since temperature and humidity have a certain impact on torque coefficient, when the temperature and humidity change significantly during on-site construction, a reference torque coefficient is calculated based on the temperature and humidity conditions of the construction site, and the average torque coefficient is then checked accordingly.

[0042] The reference torque coefficient for various temperatures can be calculated using the following proportionality formula: Phosphated bolts: ; Phosphated bolts: ; Where: T is temperature (degrees Celsius), and V is relative humidity (%).

[0043] S640: After calibrating the electric wrench on the axial force-torque meter, calculate and determine the final tightening torque value of the high-strength bolts used that day based on the verified average torque coefficient.

[0044] The torque coefficient test is conducted using an axial torque measuring instrument. During the test, the preload of the bolt should be controlled within ±5% of the design preload value; otherwise, the measured torque coefficient will be invalid data.

[0045] The torque coefficient test was conducted in a simulated on-site construction manner. The installation, tightening, initial tightening, and final tightening of the high-strength bolts were strictly tested in accordance with the construction steps. At the same time, the test environment and temperature should be kept as consistent as possible with the construction conditions.

[0046] S700: Side main beam 1, top plate 104 welding After the high-strength bolts of the side main beam 1 are finally tightened, a top plate 104 is welded onto the side main beam 1 to seal it. At the same time, a connecting nail plate 5 is welded onto the top of the splice seat 3 to facilitate bridge deck construction. There are several shear nails 6 on the top of the crossbeam 2, the top of the nail plate 5, and the top of the top plate 104.

[0047] S800: Anti-corrosion paint coating Roller coating / high-pressure spraying is used to apply anti-corrosion topcoat to the welded areas of the steel beams and the tightened areas of the high-strength bolts.

[0048] S900: Cable-stayed cable installation and initial tensioning The stay cables are installed using the tower top gantry and the high tower cable threading machine. Initial tensioning of the stay cables is carried out in the inner cavity of the main tower. The tensioning of the stay cables in the upstream and downstream, and the side and middle spans should be carried out synchronously and symmetrically.

[0049] S1000: Bridge deck hoisting Before the bridge deck is erected, clean up the debris on the top surface of the steel beam and lay rubber pads in the overlapping area between the steel beam and the bridge deck to be erected (the rubber pads can also be installed on the steel beam in advance before the steel beam is installed). The bottom surface of the rubber pads is firmly bonded to the top surface of the steel beam with general-purpose XY401 adhesive.

[0050] Using a full-slewing crane, the bridge panels were lifted one by one to the installation position, ensuring that the exposed steel bars of the bridge panels did not conflict with the shear studs 6 on the top surface of the steel beams. The exposed steel bars of the bridge panels were temporarily connected to some of the shear studs 6 to fix the bridge panels.

[0051] like Figure 1 After the first segment is completed, steps S200-S1000 can be repeated to continuously carry out the construction of the second segment; After the second segment is completed, the following steps will be taken to complete the construction of the two-segment stage: S1100: Construction of wet joints According to design requirements, stirrups, main bars, and tie bars are installed between the two sections to form a complete steel reinforcement cage. Formwork is erected, and concrete is poured for the wet joints. The steel reinforcement protective layer uses concrete or cement mortar spacers of the same grade as the main structure. The spacers should be firmly tied to the steel reinforcement, and their position and quantity should meet the specifications and design requirements, and be distributed as evenly as possible with staggered arrangement. The number of spacers on the sides and bottom of the steel reinforcement protective layer should not be less than 3 per m².

[0052] The concrete used is C60 micro-expansion polypropylene fiber concrete, which is transported from the mixing plant to the bridge site by tanker truck. The wet joint concrete is poured using a truck pump and vibrated with a hand-held vibrator.

[0053] S1200: Two double-segment cable stays After the wet joint construction is completed, the alignment and load distribution of the main beam are monitored, and the collected data is reported to the monitoring unit. After the monitoring unit analyzes and calculates the data, it issues a monitoring command for the secondary tensioning of the stay cables.

[0054] After the cable tension is adjusted, the main beam alignment and cable tension are monitored again, and the collected data is reported to the monitoring unit. The monitoring unit then analyzes and calculates the data before issuing monitoring instructions for the subsequent segment construction.

[0055] S1300: Crane moved forward; Once the wet joint strength meets the requirements, the crane moves forward to the next work position, and the above steps are repeated to construct the subsequent two sections. One forward movement of the crane allows for the construction of one double-section section.

Claims

1. A modular cantilever construction method for prefabricated side box composite beam bridge sites, characterized in that: Including single-segment construction methods: S100: Construction Preparation The full-slewing crane is in place; each steel beam is pre-assembled and transported to the bridge site; the top of the side main beam is not sealed, and splicing seats are pre-installed on the side main beam; S200: Side main beam installation The two sets of side main beams are installed in sequence; the side main beams are lifted to their installation positions using a full-rotation crane, so that the side main beam segment to be installed is aligned with the previous erected side main beam segment. After checking and adjusting the position, temporary bolts are used for fixing. S300: Beam Installation The crossbeams were hoisted to the installation position using a full-rotation crane, positioning them between the two sets of side main beams. After verifying and adjusting their positions, temporary bolts were used to fix the ends of the crossbeams to the side main beams. The crossbeams were then installed sequentially at intervals along the bridge construction direction. S400: Installation of small longitudinal beams The small longitudinal beams were hoisted to the installation position using a full-rotation crane. After the position was checked and adjusted, the ends of the crossbeams were fixed to the side main beams using temporary bolts. Several small longitudinal beams were fixed between two adjacent crossbeams in sequence. S500: Segment measurement and adjustment After a segment of steel beam is assembled, the position of the steel beam is measured and checked to control the axial deviation, upstream and downstream elevation difference and longitudinal slope of the steel beam; S600: High-strength bolt installation The steel beams are fixed with high-strength bolts in the order of main beams, crossbeams, and small longitudinal beams, and temporary bolts are replaced with high-strength bolts; the tightening is carried out in the order of initial tightening, secondary tightening and final tightening. S700: Welding of the top plate of the side main beam After the high-strength bolts of the side main beam are finally tightened, a top plate is welded onto the side main beam to seal it. S800: Anti-corrosion paint coating Roller coating / high-pressure spraying is used to apply anti-corrosion topcoat to the welded areas of steel beams and the tightened areas of high-strength bolts; S900: Cable-stayed cable installation and initial tensioning The stay cables are installed using the tower top gantry and the high tower cable threading machine. The initial tensioning of the stay cables is carried out simultaneously and symmetrically in the upstream and downstream, side and middle spans. S1000: Bridge deck hoisting Using a full-slewing crane, the bridge panels were lifted one by one to the installation position, ensuring that the exposed steel bars of the bridge panels did not conflict with the shear studs on the top surface of the steel beams. The exposed steel bars of the bridge panels were temporarily connected to some of the shear studs to fix the bridge panels.

2. The modular cantilever construction method for prefabricated side box composite beam bridge sites according to claim 1, characterized in that: After the first segment is completed, repeat steps S200-S1000 to continuously construct the second segment. After the second segment is completed, the following steps will be performed: S1100: Construction of wet joints Stirrups, main bars, and tie bars are installed between the two sections to form a complete steel reinforcement cage. Formwork is then erected and concrete is poured for the wet joint. S1200: Two double-segment cable stays After the wet joint construction is completed, the alignment and load distribution of the main beam are monitored, and the cable tension of the stay cables is readjusted. S1300: Crane moved forward; Once the wet joint strength meets the requirements, the crane moves forward to the next work station, and the above steps are repeated to construct the next two sections.

3. A modular cantilever construction method for prefabricated side box girder bridge sites according to claim 1 or 2, characterized in that: The side main beam includes a supporting frame, a bottom plate, a web plate, and a top plate; The bottom plate, web plate and top plate are joined together to form a side box structure that runs through the front and back. The supporting frame surrounds and is fixed to the inner surface of the side box structure. Multiple sets of supporting frames are arranged at intervals along the length of the side main beam.

4. The modular cantilever construction method for prefabricated side box composite beam bridge sites according to claim 3, characterized in that: A splicing seat is fixedly connected to the side of the main beam near the crossbeam. The splicing seat has a splicing groove that runs vertically through the beam and faces the opening of the crossbeam. Both ends of the crossbeam are fixedly connected to splicing plates extending toward the side main beam. The splicing plates are located in splicing grooves. The high-strength bolts pass vertically through the splicing base and the splicing plates to fix the crossbeam and the side main beam together. In step S300, the crossbeam is first hoisted vertically above the splicing seat at the installation position, then slowly lowered vertically and fixed with temporary bolts.

5. The modular cantilever construction method for prefabricated side box girder bridge sites according to claim 4, characterized in that: The splicing base includes a base plate, a bottom support plate, and a connecting plate; The base plate is vertically fixed to one side of the main beam near the crossbeam, and the bottom support plate is horizontally fixed to the bottom of the base plate. The bottom support plate extends to the bottom of the main beam and is fixedly connected to the bottom plate of the main beam. Two sets of connecting plates are vertically fixed to the base plate, and a splicing groove is formed between the two sets of connecting plates.

6. The modular cantilever construction method for prefabricated side box composite beam bridge sites according to claim 5, characterized in that: The splicing base corresponds to the position of the support frame, and the bottom plate and base plate are fixedly connected to the support frame by high-strength bolts.

7. A modular cantilever construction method for prefabricated side box girder bridge sites according to claim 1 or 2, characterized in that: Multiple sets of docking grooves are provided at intervals at one end of the base plate and the web plate; multiple sets of docking plates are fixed at the other end of the base plate and the web plate, and several fixing holes are correspondingly opened at the bottom of the docking groove and on the docking plate.

8. The modular cantilever construction method for prefabricated side box girder bridge sites according to claim 7, characterized in that: The top of the splicing base is fixed with a nail plate, and there are several shear nails on the top of the crossbeam, the top of the nail plate, and the top of the top plate.

9. A modular cantilever construction method for prefabricated side box girder bridge sites according to claim 1 or 2, characterized in that: In step S600, the final tightening torque of the high-strength bolt is calculated through the following steps: S610: Conduct torque coefficient testing on multiple batches of high-strength bolts entering the construction site and obtain the test results for each batch; S620: Perform statistical processing on the test results to obtain the average torque coefficient across batches under the temperature and humidity conditions at the construction site; S630: Calculate the reference torque coefficient based on the temperature and humidity conditions at the construction site, and use this to verify the average torque coefficient; S640: After calibrating the electric wrench on the axial force-torque meter, calculate and determine the final tightening torque value of the high-strength bolts used that day based on the verified average torque coefficient.

10. A modular cantilever construction method for prefabricated side box girder bridge sites according to claim 9, characterized in that: The reference torque coefficient for various temperatures is calculated using the following proportionality formula: Phosphated bolts: ; Phosphated bolts: ; Where: T is temperature (degrees Celsius), and V is relative humidity (%).

Images