A cast-in-place box beam construction method

Abstract

The invention relates to a cast-in-place box girder construction method, which belongs to the technical field of bridge construction, and comprises S1: surveying the geological conditions of a river channel; S2: pouring concrete on the river channel slope and the flat areas from the two ends of the river channel to the pier body respectively; S3: anchoring steel pipe piles in the center of the river channel along the direction of water flow; S4: setting up a temporary horizontal cap on the top of the steel pipe pile, and building symmetrical bevel caps at both ends of the horizontal cap, the horizontal cap and the bevel caps at both ends form a river channel foundation, the bevel caps extend to the flat area after pouring, and are connected to the flat area; S5: building a bracket and installing a bottom formwork on the river channel foundation and the flat area; S6: pre-pressing the bracket, installing the box girder formwork and steel bars, anchoring the steel pipe piles in the river channel, taking the horizontal cap as the base point, gradually building bevel caps on both sides, the bevel caps connecting the horizontal caps and the flat area, and dispersing the brackets located in the river channel area to both ends of the river channel, further enhancing the stability of the river channel foundation, and not affecting the river at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge construction, and in particular relates to a cast-in-place box girder construction method. Background Art

[0002] In bridge construction, cast-in-place box girders are widely used due to their good integrity, stable structure, and convenient construction. However, the traditional cast-in-place box girder construction method has many shortcomings during the construction process, such as low steel bar installation accuracy, lax concrete pouring quality control, and long construction period, which affect the quality and construction efficiency of the bridge. Therefore, it is of great practical significance to improve the cast-in-place box girder construction method to improve construction accuracy and efficiency.

[0003] There are multiple technical challenges in the process of constructing cast-in-place box girders across rivers. First, due to the presence of rivers, the difficulty of foundation treatment increases, and factors such as geological conditions, riverbed stability, and river scour need to be considered. Secondly, the stable installation of the support is the key to ensuring construction safety and quality. It is necessary to ensure that the support can withstand the weight of the box girder and various forces that may be generated during construction. In addition, cross-river construction also needs to consider how to reduce the impact on the river ecology and hydrological environment.

[0004] Therefore, in the construction plan of cast-in-place beams across the river channel, a construction plan that can continue to meet the requirements of foundation stability and does not affect the river ecology is required. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a cast-in-place box girder construction method to solve the problems of unstable foundation and easy ecological impact on the river channel in the existing cast-in-place beam construction across the river channel.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A cast-in-place box girder construction method, comprising:

[0008] S1: Survey the geological conditions of the river;

[0009] S2: Concrete is poured on the river slope and the flat areas from both ends of the river to the pier body;

[0010] S3: Anchor steel pipe piles in the center of the river along the direction of water flow;

[0011] S4: A temporary horizontal cap is set up on the top of the steel pipe pile, and symmetrical bevel caps are built at both ends of the horizontal cap. The horizontal cap and the bevel caps at both ends form the river foundation. The bevel caps extend to the flat area where the pouring is completed and are connected to the flat area.

[0012] S401: Preparation of the beveled side cap and the steel pipe frame, the steel pipe frame includes the reinforced steel pipe piles, the first steel pipe piles, the side column fixing parts and the receiving parts;

[0013] S402: installing reinforcement steel pipe piles between the horizontal cap and the flat area, wherein the reinforcement steel pipe piles include outer square piles and inner square piles;

[0014] S403: laying the first steel pipe pile on the reinforced steel pipe pile to form a preliminary bevel support frame;

[0015] S404: welding receiving parts at equal intervals on the bevel support frame, wherein one receiving part array is provided with a plurality of threaded mounting openings;

[0016] S405: laying a second steel pipe pile on the bevel support frame, wherein the installation opening extends outside the second steel pipe pile;

[0017] S406: Install side column fixings on both sides of the first steel pipe pile and the second steel pipe pile; the side column fixings include a first fixing group and a second fixing group, the first fixing group and the second fixing group are respectively fixed to the first steel pipe pile and the second steel pipe pile, and the first fixing group and the second fixing group are detachably connected; the first fixing group and the second fixing group have the same structure, both including a fixing part and a connecting part; the fixing part is vertically arranged at the connecting part and fixedly installed in the cavity of the steel pipe pile, and the connecting parts of the first fixing group and the second fixing group are sequentially clamped in the upper and lower parts

[0018] S5: Build supports and install bottom formwork on the river foundation and flat area;

[0019] S6: Support pre-stressing, box girder formwork and steel bar installation.

[0020] Preferably, in step S3, two rows of anchoring steel pipe piles are implanted along the direction of water flow.

[0021] Preferably, the angle between the beveled platform and the flat area is between 150° and 160°.

[0022] Preferably, the specific construction steps for erecting the support of S5 are:

[0023] S501: Select the cup-hook type multifunctional scaffolding and determine the vertical and horizontal spacing and horizontal spacing of the tangerines according to the structural size and deadweight;

[0024] S502: Place steel sections on the bracket in the transverse direction of the bridge as distribution beams, then lay square timber on the distribution beams, and finally lay the bottom formwork;

[0025] S503: The support erection elevation is adjusted through the lower base and the upper support seat to ensure that the support node elevation is consistent with the box girder node bottom elevation;

[0026] S504: Ordinary steel pipe scissors braces are set in the longitudinal and transverse directions.

[0027] Preferably, the stent pre-compression comprises the following steps:

[0028] S601: Prepare sandbags and preload the support system:

[0029] S602: Install the bottom formwork on the bracket, and then install the side forms on both sides of the bottom formwork. After the side forms are installed, install the end forms on both ends of the box beam;

[0030] S603: Use steel bars and tie rods to fix the formwork to the bracket, and check the flatness, verticality and position of the formwork.

[0031] Preferably, the stent system is pre-stressed in a graded weighting manner, including:

[0032] S6011: First level loading, loading to 50% of the total weight, simulating the installation process of the bottom plate, web reinforcement and prestressed tendons;

[0033] S6012: The second level loading is to load to 75% of the total weight, simulating the pouring process of the bottom slab concrete, inclined web concrete and top slab;

[0034] S6013: Third level loading: loading to 100% of the total weight, simulating the condition of box girder concrete pouring completed;

[0035] S6014: Check the deformation of the box girder and the sinking of the support.

[0036] Preferably, the method further includes casting and curing of the beam box:

[0037] S701: Concrete pouring: pour the bottom plate and web plate of the box girder first, and then pour the top plate after the bottom plate and web plate reach 70% of the design strength;

[0038] S702: The inserted vibrator is used for vibrating, and the vibrating rod is kept vertically vibrating;

[0039] S703: After pouring, use plastic film to cover the bridge deck in a non-contact manner and cover it with a curing cover for steam curing.

[0040] The beneficial effects of the present invention are:

[0041] Anchor steel pipe piles in the river channel to build a temporary foundation. Take the horizontal pedestal as the base point and gradually build inclined pedestals on both sides. The inclined pedestals connect the horizontal pedestal and the flat area. When setting up the support, the support located in the river channel area can be dispersed to both ends of the river channel to further enhance the stability of the river channel foundation without affecting the river. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0043] Figure 1 A schematic diagram of the structure of the horizontal cap arrangement of a cast-in-situ box girder across a river channel provided in one embodiment of the present invention;

[0044] Figure 2 It is a schematic diagram of the installation structure of the beveled edge support provided in one embodiment of the present invention;

[0045] Figure 3 A schematic diagram of a reinforced steel pipe pile structure provided in one embodiment of the present invention;

[0046] Figure 4 A schematic diagram of the installation structure of a side column fixing member provided in one embodiment of the present invention;

[0047] Figure 5 A schematic diagram of a connection structure of multiple side column fixing members provided in one embodiment of the present invention;

[0048] Legend: 1. Box girder; 2. Support system; 3. Anchor steel pipe piles; 4. Horizontal cap; 5. Bevel cap; 51. First steel pipe pile; 52. Reinforced steel pipe pile; 53. Receiver; 54. Second steel pipe pile; 6. Flat area; 7. Side column fixings; 71. Connecting part; 72. Fixing part. DETAILED DESCRIPTION

[0049] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0050] like Figure 1-Figure 5 As shown, a cast-in-place box girder construction method includes:

[0051] S1: Survey the geological conditions of the river channel; First of all, it is crucial to conduct a detailed survey of the geological conditions of the river channel, which includes a comprehensive investigation of the river's topography, hydrology and water quality, ecological environment, bank slopes and mudflats, and production and living facilities. The survey method can use traditional measurement methods (such as total stations, rangefinders, etc.), remote sensing technology, and drone measurement technology to ensure accurate data.

[0052] S2: After the survey is completed, concrete is poured on the river slope and the flat area 6 from both ends of the river to the pier body to reinforce the river slope and prevent the foundation from being unstable due to water erosion, while providing a solid foundation for subsequent construction. During the pouring process, attention should be paid to the mix ratio, pouring amount and pouring quality of the concrete to ensure that the concrete can meet the strength and stability required by the design.

[0053] S3: Anchor steel pipe piles 3 are implanted in the center of the river channel along the direction of water flow. As a key measure for foundation reinforcement, anchor steel pipe piles 3 can effectively resist the scouring and scouring force of water flow and improve the stability of the foundation. When anchoring steel pipe piles 3, it is necessary to ensure the verticality, depth and spacing of anchor steel pipe piles 3 to ensure that they can withstand the expected load and impact force. By anchoring steel pipe piles 3 and pouring concrete, the anti-scouring ability of the river channel foundation is significantly improved. Even in the case of severe water scouring, the foundation can remain stable, providing a solid foundation for the construction of box girder 1. In addition, in order to reduce the effect of anchor steel pipe piles 3 on the direction of water flow and water flow, avoid When a turbulent torrent occurs, the impact force of the water flow will affect the stability of the anchored steel pipe piles 3, thereby causing the stability of the entire horizontal pedestal 4 to decrease. The anchored steel pipe piles 3 are arranged along the direction of the water flow to reduce the interaction between the anchored steel pipe piles 3 and the water flow. When the anchored steel pipe piles 3 arranged in the direction of the water flow interact with the water flow, the greater the force of the first anchored steel pipe pile 3 interacting with the water flow, the effect of the anchored steel pipe piles 3 arranged sequentially along the direction of the water flow gradually decreases, forming a stable water flow impact wall, laying a good foundation for the stability of the horizontal pedestal 4; at the same time, the anchored steel pipe piles 3 arranged sequentially along the direction of the water flow have little interference with the flow of river water, and will not affect the water use downstream, such as farmland irrigation.

[0054] S4: A temporary horizontal cap 4 is set up on the top of the steel pipe pile, and symmetrical bevel caps 5 are built at both ends of the horizontal cap 4. The horizontal cap 4 and the bevel caps 5 at both ends form a river channel foundation. The bevel caps 5 extend to the flat area 6 that has been cast and are connected to the flat area 6. After the steel pipe pile is implanted, a temporary horizontal cap 4 needs to be set up on its top. The horizontal cap 4, as a supporting platform for the construction of the box girder 1, needs to have a certain bearing capacity and stability. At the same time, symmetrical bevel caps 5 are built at both ends of the horizontal cap 4 to expand the supporting area of ​​the cap and improve the overall stability of the foundation. The bevel cap 5 extends to the flat area 6 that has been cast and is connected to the flat area 6 to form a complete river channel foundation. The combined use of the horizontal cap 4 and the bevel cap 5 greatly improves the bearing capacity of the foundation, which can not only meet the requirements of the box girder 1 construction for the foundation bearing capacity, but also provide sufficient safety guarantees for the subsequent bridge operation.

[0055] S5: Building a support and installing a bottom formwork on the river foundation and the flat area 6;

[0056] S6: Support pre-stressing, box girder 1 formwork and steel bar installation.

[0057] In summary, anchor steel pipe piles 3 are implanted in the river channel to build a temporary foundation. With the horizontal pedestal 4 as the base point, the beveled pedestal 5 is gradually built on both sides. The beveled pedestal 5 connects the horizontal pedestal 4 and the flat area 6. When setting up the support, the support located in the river channel area can be dispersed to both ends of the river channel, so as to further enhance the stability of the river channel foundation without affecting the river.

[0058] In one embodiment, in step S3, two rows of anchoring steel pipe piles 3 are implanted along the direction of water flow, which can further enhance the stability of the horizontal platform 4. In addition, since both ends of the horizontal platform 4 are connected to the hypotenuse platform 5, the force on the horizontal platform 4 will increase. If only one row of anchoring steel pipe piles 3 is implanted in the river channel, it will easily lead to unbalanced force on both ends of the horizontal platform 4. Therefore, the symmetrically arranged anchoring steel pipe piles 3 can increase the supporting force of the horizontal platform 4 and ensure the stability of the action on both ends of the horizontal platform 4.

[0059] In one embodiment, the angle between the beveled pedestal 5 and the flat area 6 is between 150° and 160°; the angle between the beveled pedestal 5 and the flat area 6 can be determined by measurement and calculation; first, the geological conditions of the river channel are surveyed to understand the bearing capacity and stability of the foundation; then, the angle range between the beveled pedestal 5 and the flat area 6 is determined according to the geological conditions and design requirements; the appropriate angle design can ensure that the connection between the beveled pedestal 5 and the flat area 6 is more stable, reducing the structural deformation and damage caused by uneven settlement of the foundation or water scouring, thereby improving the stability of the entire structure; according to the principles of mechanics, the angle design of the structure will affect its force performance and stability. Through reasonable angle design, the structure can generate a reasonable internal force distribution when subjected to external force, thereby improving the bearing capacity and stability of the structure. The appropriate angle can optimize the distribution of stress in the structure, avoid the occurrence of stress concentration, and reduce the risk of damage to the structure caused by excessive stress.

[0060] In one embodiment, the method for constructing the beveled platform 5 includes:

[0061] S401: Prepare the hypotenuse cap 5 and the steel pipe frame. The steel pipe frame preparation includes the reinforcement steel pipe pile 52, the first steel pipe pile 51, the second steel pipe pile 54, the side column fixing member 7 and the receiving member 53. According to the requirements of the hypotenuse cap 5, select the steel pipe frame of appropriate specifications as the main supporting structure. These steel pipe frames are used to construct the skeleton of the hypotenuse cap 5 to form a stable supporting foundation. The side column fixing member 7 is used to connect the steel pipe frame installed on the hypotenuse, and the receiving member 53 is used to connect the hypotenuse cap 5 with the upper structure to ensure the stability of the overall structure.

[0062] S402: installing reinforced steel pipe piles 52 between the horizontal cap 4 and the flat area 6, the reinforced steel pipe piles 52 including outer piles in the shape of a square and inner piles in the shape of a cross. As the main support frame, the outer piles in the shape of a square can resist external pressure and maintain the stability of the cap. The inner piles in the shape of a cross are arranged inside the outer piles in the shape of a square to increase the bearing capacity of the cap and prevent internal deformation.

[0063] S403: Laying the first steel pipe pile 51 on the reinforced steel pipe pile 52 to form a preliminary bevel support frame, wherein a plurality of reinforced steel pipe piles 52 are closely connected to form a stable support plane;

[0064] S404: Weld the sockets 53 at equal intervals on the bevel support frame, wherein one of the sockets 53 arrays is provided with a plurality of threaded mounting openings to ensure that the upper structure can be evenly stressed, and the threaded mounting openings on the sockets 53 are used to connect the upper support structure, such as the existing frame beam for supporting the box beam 1.

[0065] S405: laying a second steel pipe pile 54 on the bevel support frame, with the installation opening extending outside the second steel pipe pile 54, to increase the rigidity and bearing capacity of the bevel support frame, and the installation opening extending outside the second steel pipe pile 54 to facilitate connection with the upper structure and to reinforce the bevel cap 5;

[0066] S406: Install side column fixings 7 on both sides of the first steel pipe pile 51 and the second steel pipe pile 54; the side column fixings 7 include a first fixing group and a second fixing group, the first fixing group and the second fixing group are respectively fixed to the first steel pipe pile 51 and the second steel pipe pile 54, and the first fixing group and the second fixing group are detachably connected; the first fixing group and the second fixing group have the same structure, and both include a fixing portion 72 and a connecting portion 71; the fixing portion 72 is vertically arranged on the connecting portion 71, and is fixedly installed in the cavity of the steel pipe frame, and the connecting portions 71 of the first fixing group and the second fixing group are sequentially clamped in the upper and lower parts; so that the side column fixings 7 lock the inclined hypotenuse support frame and the second steel pipe pile 54, thereby enhancing the connection between the hypotenuse cap 5 and the second steel pipe pile 54 and the stable support effect on the box girder 1.

[0067] In summary, through the combination of the reinforced steel pipe piles 52 and the first steel pipe piles 51, a stable supporting structure is formed, which can resist external pressure and impact and ensure the stability of the beveled platform 5. The M-shaped inner piles and the multiple reinforcement layers make the beveled platform 5 have a stronger bearing capacity and can meet the weight and use requirements of the superstructure; the precise connection of the equidistantly welded sockets 53 and the side column fixings 7 ensures that the connection between the beveled platform 5 and the superstructure is firm and reliable to avoid displacement or loosening; materials such as the steel pipe frame and the sockets 53 are reusable, which reduces resource waste and environmental pollution and meets the requirements of green construction.

[0068] In one embodiment, the specific construction steps of the support erection in step 5 are:

[0069] S501: Build a full-floor support and determine the vertical and horizontal spacing and horizontal spacing according to the structure size and deadweight; the bowl-hook type multifunctional scaffolding can adapt to box beam structures of different sizes and shapes due to its structural characteristics, ensuring the flexibility and efficiency of construction. By accurately calculating the structure size and deadweight, determining the vertical and horizontal spacing and horizontal spacing can ensure that the support has sufficient bearing capacity and ensure safety during construction. At the same time, reasonable spacing setting can reduce unnecessary material waste and reduce construction costs.

[0070] S502: Place steel sections on the bracket in the transverse direction of the bridge as distribution beams, then lay square timber on the distribution beams, and finally lay the bottom formwork;

[0071] S503: The elevation of the support erection is adjusted through the lower base and the upper support seat to ensure that the elevation of the support node matches the bottom elevation of the box girder 1 node; by adjusting the lower base and the upper support seat, the elevation of the support can be accurately controlled to ensure that the elevation of the support node matches the bottom elevation of the box girder 1 node, thereby reducing construction errors. The matching elevation can ensure that the size and shape of the box girder 1 meet the design requirements and ensure the quality of the box girder 1.

[0072] S504: Ordinary steel pipe scissors braces are set in the longitudinal and transverse directions.

[0073] In one embodiment, the stent pre-stressing comprises the following steps:

[0074] S601: Prepare sandbags and preload the support system 2: S601: Prepare sandbags and preload the support system 2. Preloading simulates the actual load during bridge construction, detects the safety and stability of the support system 2, and eliminates non-elastic deformation, providing accurate settlement data and safety assurance for subsequent bridge construction. Operation: According to the bridge design requirements and construction plan, select the appropriate number and weight of sandbags and evenly stack them on the built support.

[0075] S602: Install the bottom formwork on the bracket, then install the side forms on both sides of the bottom formwork, and after the side forms are installed, install the end forms at both ends of the box beam 1; installing the formwork is one of the key steps in bridge construction, and the bottom formwork, side formwork and end formwork together constitute the bridge forming formwork. Operation: First install the bottom formwork and ensure its flatness and stability; then install the side forms on both sides of the bottom formwork to ensure that the side forms are tightly connected to the bottom formwork and vertically; finally install the end forms at both ends of the box beam 1 to ensure the closure and stability of the entire formwork system.

[0076] S603: Use steel bars, tie rods and other fixings to fix the formwork to the bracket, and check the flatness, verticality and position of the formwork. Fixing the formwork is to prevent displacement or deformation of the formwork during concrete pouring, and to ensure the accuracy and stability of the bridge forming. Operation: Use steel bars, tie rods and other fixings to firmly connect the formwork to the bracket: Then check the flatness, verticality and position of the formwork to ensure that the formwork meets the design requirements. Principle description: Bracket preloading is a process of testing the safety and stability of the bracket system 2 by applying simulated loads to the bracket. During the preloading process, the bracket will undergo a certain amount of settlement and deformation, which are important reference data for subsequent bridge construction. The installation and fixing of the formwork is to ensure the accuracy and stability of the bridge forming. The flatness, verticality and position of the formwork will directly affect the forming quality and appearance of the bridge.

[0077] In one embodiment, the stent system 2 is pre-stressed in a stepwise manner, including:

[0078] S6011: The first level of loading is to load to 50% of the total weight, simulating the installation process of the bottom plate, web reinforcement, prestressed tendons, etc. The sandbags are evenly stacked on the bracket to ensure uniform distribution of the load and avoid local overload;

[0079] S6012: The second level of loading is to load to 75% of the total weight, simulating the pouring process of the bottom plate concrete, inclined web concrete, top plate, etc., gradually increasing the loading material to ensure stability and safety during the loading process, continuously observing the deformation and sinking of the support system 2, and continuing to compare and analyze with the data of the first level of loading;

[0080] S6013: Third level loading: Load to 100% of the total weight, simulate the condition of box girder 1 concrete pouring completion, continue to add materials on the basis of the second level loading until the total weight of preloading is reached, carefully observe the deformation and sinking of the support system 2, and record the data in detail;

[0081] S6014: Check the deformation of box girder 1 and the sinking of the support; after completing the third level loading, conduct a comprehensive inspection of the support system 2, including deformation, sinking, cracks, etc. Use measuring tools to accurately measure the deformation and sinking of the support system 2 and record the data.

[0082] In one embodiment, it also includes casting and curing of the beam box:

[0083] S701: Concrete pouring: first pour the bottom plate and web plate of box girder 1, and then pour the top plate after the bottom plate and web plate reach 70% of the design strength. During pouring, keep the bottom plate concrete evenly laid without hollows or cracks;

[0084] S702: Use an inserted vibrator to vibrate, and keep the vibrator rod vertically to effectively remove bubbles in the concrete and improve the density and strength of the concrete. During the vibration process, be careful to avoid contact between the vibrator rod and the formwork or steel bars to prevent deformation of the formwork or displacement of the steel bars.

[0085] S703: After pouring, the bridge deck is covered with plastic film in a non-contact manner and covered with a curing cover for steam curing. The combination of plastic film and non-contact covering of the pouring surface and steam curing can keep the concrete surface moist and at a suitable temperature, which is conducive to the early strength development of concrete and the improvement of its later durability.

[0086] In short, layered pouring and vibration treatment can effectively ensure the quality of beam box concrete and improve the overall performance and durability of the beam box. The combination of non-contact dense covering and steam curing can greatly reduce the occurrence of cracks on the concrete surface and improve the aesthetics and service life of the beam box. Reasonable pouring and curing technology can shorten the construction period of the beam box, improve construction efficiency and reduce construction costs. At the same time, it also helps to reduce the cost of later maintenance and repair and improve the economic benefits of the project.

[0087] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A cast-in-place box girder construction method, characterized in that: include, S1: Survey the geological conditions of the river; S2: Concrete is poured on the river slope and the flat areas from both ends of the river to the pier body; S3: Anchor steel pipe piles in the center of the river along the direction of water flow; S4: A temporary horizontal cap is set up on the top of the steel pipe pile, and symmetrical bevel caps are built at both ends of the horizontal cap. The horizontal cap and the bevel caps at both ends form the river foundation. The bevel caps extend to the flat area where the pouring is completed and are connected to the flat area. S401: Preparation of the beveled side cap and the steel pipe frame, the steel pipe frame includes the reinforced steel pipe piles, the first steel pipe piles, the side column fixing parts and the receiving parts; S402: installing reinforcement steel pipe piles between the horizontal cap and the flat area, wherein the reinforcement steel pipe piles include outer square piles and inner square piles; S403: laying the first steel pipe pile on the reinforced steel pipe pile to form a preliminary bevel support frame; S404: welding receiving parts at equal intervals on the bevel support frame, wherein one receiving part array is provided with a plurality of threaded mounting openings; S405: laying a second steel pipe pile on the bevel support frame, wherein the installation opening extends outside the second steel pipe pile; S406: Install side column fixings on both sides of the first steel pipe pile and the second steel pipe pile; the side column fixings include a first fixing group and a second fixing group, the first fixing group and the second fixing group are respectively fixed to the first steel pipe pile and the second steel pipe pile, and the first fixing group and the second fixing group are detachably connected; the first fixing group and the second fixing group have the same structure and both include a fixing part and a connecting part; the fixing part is vertically arranged at the connecting part and fixedly installed in the cavity of the steel pipe pile, and the connecting parts of the first fixing group and the second fixing group are sequentially clamped in upper and lower connection; S5: Build supports and install bottom formwork on the river foundation and flat area; S6: Support pre-stressing, box girder formwork and steel bar installation.

2. A cast-in-place box girder construction method according to claim 1, characterized in that: In the step S3, two rows of anchoring steel pipe piles are implanted along the water flow direction.

3. A cast-in-place box girder construction method according to claim 1, characterized in that: The angle between the beveled edge support and the flat area is between 150° and 160°.

4. A cast-in-place box girder construction method according to claim 1, characterized in that: The specific construction steps for erecting the support of S5 are as follows: S501: Select the cup-hook type multifunctional scaffolding, and determine the vertical and horizontal spacing and horizontal spacing of the vertical poles according to the structural size and deadweight; S502: Place steel sections on the bracket in the transverse direction of the bridge as distribution beams, then lay square timber on the distribution beams, and finally lay the bottom formwork; S503: The support erection elevation is adjusted through the lower base and the upper support seat to ensure that the support node elevation is consistent with the box girder node bottom elevation; S504: Ordinary steel pipe scissors braces are set in the longitudinal and transverse directions.

5. A cast-in-place box girder construction method according to claim 1, characterized in that: The stent preloading comprises the following steps: S601: Prepare sandbags and preload the support system: S602: Install the bottom formwork on the bracket, and then install the side forms on both sides of the bottom formwork. After the side forms are installed, install the end forms on both ends of the box beam; S603: Use steel bars and tie rods to fix the formwork to the bracket, and check the flatness, verticality and position of the formwork.

6. A cast-in-place box girder construction method according to claim 5, characterized in that: The bracket system is pre-stressed by a graded weighting method, including: S6011: First level loading, loading to 50% of the total weight, simulating the installation process of the bottom plate, web reinforcement, and prestressed tendons; S6012: The second level of loading is to load to 75% of the total weight, simulating the pouring process of the bottom slab concrete, inclined web concrete, and top slab; S6013: Third level loading: loading to 100% of the total weight, simulating the condition of box girder concrete pouring completed; S6014: Check the deformation of the box girder and the sinking of the support.

7. A cast-in-place box girder construction method according to claim 1, characterized in that: It also includes the pouring and maintenance of beam boxes: S701: Concrete pouring: pour the bottom plate and web plate of the box girder first, and then pour the top plate after the bottom plate and web plate reach 70% of the design strength; S702: The inserted vibrator is used for vibrating, and the vibrating rod is kept vertically vibrating; S703: After pouring, use plastic film to cover the bridge deck in a non-contact manner and cover it with a curing cover for steam curing.

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