Bridge cast-in-place box girder construction method

Abstract

The invention relates to a bridge cast-in-place box girder construction method, which relates to the technical field of bridge construction, and comprises the following steps: S1, preparation and foundation construction; s2, bottom plate and web plate construction; s3, constructing an inner mold and a top plate; s4, pre-stress construction; s5, removing the template and the bracket; and S6, performing dustproof treatment. According to the bridge cast-in-place box girder construction method, deeper foundation reinforcement measures such as pile foundations and deep mixing piles are adopted in the foundation treatment stage, the replacement and filling thickness is synchronously increased to 150 cm or above, layering compaction is conducted, and the thickness of each layer is controlled to be 20-30 cm, so that the problem of uneven settlement possibly caused by complex geological conditions or soft foundations is effectively solved, and the construction quality of the bridge cast-in-place box girder is improved. In addition, a graded loading type support pre-pressing technology is introduced in the method, the maximum load in actual construction is simulated, the pre-pressing time is not less than 48 hours, the perpendicularity and flatness of the support are guaranteed, and the reliability of the whole supporting system is further enhanced.

Description

Technical Field

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

[0002] Cast-in-place box girder is a prestressed concrete structure, and its cross-sectional shape is usually box-shaped, hence the name "box girder". The box girder consists of a bottom plate, a top plate and webs on both sides to form a closed box section. The cast-in-place box girder is formed by directly pouring concrete at the construction site. Compared with precast box girders, cast-in-place box girders do not need to be prefabricated in the factory and then transported to the site for installation. Cast-in-place box girders usually adopt prestressed technology, by arranging prestressed steel bars (steel bundles) in the concrete, and tensioning these steel bars after the concrete is poured, thereby generating prestress in the structure and improving the bearing capacity and crack resistance of the structure. In municipal engineering and highway engineering, cast-in-place box girder bridge structure forms are mostly used. Cast-in-place box girders can not only be used in the straight section of the main line bridge, but can also be cast into ramp branches with a smaller curvature radius according to the direction of the road and the design intent, so it has a wide range of applications.

[0003] A method for constructing a cast-in-place box girder for a bridge is disclosed in Chinese patent CN102121233A, which is characterized in that when the parts are heated in a furnace mainly using radiation heat transfer, metal materials are used to separate the parts from the furnace heating elements so that the parts can be heat treated under uniform heating conditions. The above invention has the advantages of simple process, easy implementation, wide application, etc., and can effectively improve the performance of metal materials. However, in the construction process of the above application, first of all, the above application mentions that the foundation treatment adopts a three-step three-seven ash soil replacement, with a thickness of 20-40 cm in each step and a total treatment thickness of 80-100 cm. Although this treatment method can improve the bearing capacity of the foundation, for complex geological conditions or weak foundations, a replacement depth of 100 cm may not be enough to completely solve the foundation settlement problem, especially under long-term loads, uneven settlement may occur. It is mentioned that square wood is used to support the lower part of the support to diffuse the internal force of the support. However, the bearing capacity of square wood is limited, especially when it is subjected to heavy loads for a long time, it may deform or break, affecting the overall stability of the support. Finally, the document does not mention in detail the dust control measures during the construction process, especially in the foundation treatment and concrete pouring links, which may generate more dust, affecting the environmental quality of the construction site and the health of the workers. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for constructing a cast-in-place box girder for a bridge, which has the advantages of enhancing foundation stability and solving the problem that traditional foundation treatment is not deep enough and may cause long-term uneven settlement.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for constructing a cast-in-place box girder for a bridge, comprising the following steps:

[0006] S1 Preparation and foundation construction: First, load treatment is carried out on the foundation. For areas with complex geological conditions, deeper foundation reinforcement measures are adopted. After the foundation treatment is completed, settlement monitoring equipment is installed, and then full-floor supports are built. Then, graded loading supports are pre-loaded after the bottom formwork is installed;

[0007] S2 bottom plate and web construction: adjust the elevation of the bottom formwork and install the bottom formwork and support, then use the positioning frame to tie and install the bottom plate steel bars, web steel bars and prestressed pipes, then pour the concrete of the bottom plate and web in layers, and perform intelligent spray curing;

[0008] S3 Inner formwork and top plate construction: Install the inner formwork, inner bracket and top formwork, and then use the steel bar positioner and welding fixing points to tie the top plate steel bars. After the tying is completed, pour the top plate concrete and perform maintenance, and install monitoring equipment for real-time monitoring;

[0009] S4 prestressed construction: During the top slab concrete curing process, ultrasonic testing equipment is used to monitor the concrete strength in real time. After reaching the specified strength, the prestressed steel strands are threaded, that is, the prestressed steel strands are tensioned, and vacuum-assisted grouting technology and anchor sealing are used to fix the steel strands;

[0010] S5 Formwork and support removal: After the concrete strength meets the requirements, use soft materials to wrap the disassembly tools to remove the bottom formwork and support;

[0011] S6 Dust prevention: Design a piping system around the construction area and perform spray dust removal during foundation treatment and concrete pouring.

[0012] Furthermore, in step S1, deeper foundation reinforcement measures are adopted, including pile foundations and deep mixing piles. The replacement thickness is simultaneously increased to more than 150 cm according to the situation, and compacted in layers, with the thickness of each layer controlled at 20-30 cm.

[0013] Furthermore, after the bottom formwork is installed in step S1, a graded loading bracket pre-stressing is performed, with the loading amount gradually increasing each time to simulate the maximum load in actual construction. The pre-stressing time is not less than 48 hours. After the pre-stressing is completed, the verticality and flatness of the bracket are checked.

[0014] Furthermore, in step S2, the concrete of the bottom plate and the web is poured in layers, and the height of each pouring is controlled within 30 cm. At the same time, cooling water pipes are pre-buried in the concrete to reduce the internal temperature of the concrete.

[0015] Furthermore, the longitudinal spacing of the support uprights in the full-hall support is 0.6m-0.9m, the bottom plate cross partition adopts a denser cloth of 0.6m, the flange plate adopts a 0.9m cloth, the lateral spacing of the support uprights is 0.7m at the bottom plate and 1.0m at the flange plate, and the pitch of the longitudinal and transverse horizontal bars is set to 1.2m.

[0016] Furthermore, the bottom formwork adopts 1.5 cm thick high-strength bamboo plywood, which is fixed by 10×10 cm square wooden cross ribs with a spacing of 25 cm; the longitudinal ribs adopt double rows of scaffolding steel pipes with a spacing of 90 cm, and 300×20×5 cm wooden boards are laid on the top support of the bracket. The side walls and top surface formwork of the inner formwork adopt 1.5 cm thick plywood. The inner formwork is connected to the beam body steel bars with tension rods every 2 m, and a 1.0 m×1.0 m working hole is reserved in the middle of the span of each box chamber.

[0017] Furthermore, the side formwork usually adopts a composite steel plate, with sealing sponge strips or rubber waterstop strips added at the joints, and the sides are reinforced with diagonal braces with a spacing of 0.6m. The top formwork adopts 1.5cm thick bamboo plywood, which is fixed by 10×10cm square wooden cross ribs with a spacing of 25cm; the longitudinal ribs adopt double rows of scaffolding steel pipes with a spacing of 90cm.

[0018] Furthermore, the monitoring equipment includes a camera, and the camera is cleaned every day. The nozzles in the intelligent spray maintenance system are installed around the beam body and can evenly spray fine water mist to cover the entire concrete surface. The intelligent spray maintenance system also includes a temperature and humidity sensor installed on the concrete surface and its surrounding environment for real-time monitoring of the air.

[0019] Furthermore, during the vacuum-assisted grouting process, the pressure in the pores is reduced to 0.06-0.08 MPa, that is, the vacuum degree reaches -60-80 kP, and the vacuum state in the pores is maintained for at least 2 minutes before grouting.

[0020] Furthermore, in step S6, the pipeline system is shared with the intelligent spray maintenance system. In windy weather conditions, the spraying frequency is increased, and closed enclosures are set up in construction areas with large dust.

[0021] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0022] 1. The cast-in-place box girder construction method of the bridge adopts deeper foundation reinforcement measures in the foundation treatment stage, such as pile foundation and deep mixing pile, and increases the replacement thickness to more than 150cm at the same time, and compacts it in layers, with the thickness of each layer controlled at 20-30cm, which effectively solves the problem of uneven settlement caused by complex geological conditions or weak foundations, and ensures the stability of the foundation under long-term load. In addition, the method introduces graded loading bracket preloading technology to simulate the maximum load in actual construction. The preloading time is not less than 48 hours, which ensures the verticality and flatness of the bracket and further enhances the reliability of the entire support system. During the construction of the bottom plate and the web, the layered pouring of concrete is adopted, and the height of each pouring is controlled within 30cm. Cooling water pipes are pre-buried in the concrete to reduce the internal temperature and prevent cracks caused by temperature differences. At the same time, the application of the intelligent spray curing system can not only evenly cover the entire concrete surface, but also automatically adjust the spray volume according to the real-time monitored air temperature and humidity to ensure that the concrete completes the hydration reaction under the best conditions, thereby improving the quality and durability of the concrete.

[0023] 2. The cast-in-place box girder construction method of the bridge uses steel bar locators and welding fixing points to tie the top plate steel bars, ensuring the accurate position of the steel bars and providing a solid foundation for subsequent concrete pouring. In the prestressed construction stage, ultrasonic detection equipment is used to monitor the concrete strength in real time to ensure that the prestressed steel bundles are threaded and tensioned only after reaching the specified strength. Combined with vacuum-assisted grouting technology and anchor sealing, the steel bundles are effectively fixed, enhancing the integrity and bearing capacity of the structure. A pipeline system shared with the intelligent spray maintenance system is designed to increase the spraying frequency under windy weather conditions, and closed enclosures are set up in construction areas with large dust, effectively reducing dust pollution during construction and improving the environmental quality of the construction site and the health of workers. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the construction method of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] See also Figure 1 In this embodiment, a method for constructing a cast-in-place box girder for a bridge comprises the following steps:

[0027] S1 Preparation and foundation construction: First, load treatment is carried out on the foundation. For areas with complex geological conditions, deeper foundation reinforcement measures are adopted. After the foundation treatment is completed, settlement monitoring equipment is installed, and then full-floor supports are built. Then, graded loading supports are pre-loaded after the bottom formwork is installed;

[0028] S2 bottom plate and web construction: adjust the elevation of the bottom formwork and install the bottom formwork and support, then use the positioning frame to tie and install the bottom plate steel bars, web steel bars and prestressed pipes, then pour the concrete of the bottom plate and web in layers, and perform intelligent spray curing;

[0029] S3 Inner formwork and top plate construction: Install the inner formwork, inner bracket and top formwork, and then use the steel bar positioner and welding fixing points to tie the top plate steel bars. After the tying is completed, pour the top plate concrete and perform maintenance, and install monitoring equipment for real-time monitoring;

[0030] S4 prestressed construction: During the top slab concrete curing process, ultrasonic testing equipment is used to monitor the concrete strength in real time. After reaching the specified strength, the prestressed steel strands are threaded, that is, the prestressed steel strands are tensioned, and vacuum-assisted grouting technology and anchor sealing are used to fix the steel strands;

[0031] S5 Formwork and support removal: After the concrete strength meets the requirements, use soft materials to wrap the disassembly tools to remove the bottom formwork and support;

[0032] S6 Dust prevention: Design a piping system around the construction area and perform spray dust removal during foundation treatment and concrete pouring.

[0033] These steps ensure the integrity and quality control from foundation preparation to the final product, and are the basis for achieving high-quality bridge construction.

[0034] Among them, in step S1, deeper foundation reinforcement measures are adopted, including pile foundation and deep mixing piles. The replacement thickness is simultaneously increased to more than 150cm according to the situation, and compacted in layers, and the thickness of each layer is controlled at 20-30cm.

[0035] It should be noted that during the preparation and foundation construction stage, for areas with complex geological conditions, deeper foundation reinforcement measures were adopted, such as pile foundations and deep mixing piles, and the replacement thickness can be increased to more than 150cm according to actual conditions, and compacted in layers to enhance the bearing capacity of the foundation. The thickness of each layer is controlled between 20-30cm, thus providing a solid foundation for subsequent construction.

[0036] Among them, after the bottom formwork is installed in step S1, a graded loading bracket pre-compression is performed, and the loading amount is gradually increased each time to simulate the maximum load in actual construction. The pre-compression time is not less than 48 hours. After the pre-compression is completed, the verticality and flatness of the bracket are checked.

[0037] It should be noted that after the installation of the bottom formwork is completed, the bracket is pre-loaded in a graded loading manner. The loading amount is gradually increased each time until the maximum load in actual construction is simulated. The pre-loading time is no less than 48 hours. After this process is completed, the verticality and flatness of the bracket need to be checked to ensure the safety and stability of the bracket structure and avoid possible problems in the later stage.

[0038] In step S2, the concrete of the bottom plate and the web is poured in layers, and the height of each pouring is controlled within 30 cm. At the same time, cooling water pipes are pre-buried in the concrete to reduce the internal temperature of the concrete.

[0039] It should be noted that in the construction of the base plate and web, a layered pouring method was adopted for concrete pouring. The height of each pouring was controlled within 30 cm to ensure the quality of the concrete. Cooling water pipes were pre-buried in the concrete to lower the internal temperature, prevent cracks caused by excessive temperature, and improve the durability of the concrete.

[0040] Among them, the longitudinal spacing of the support uprights in the full-floor support is 0.6m-0.9m, the bottom plate cross partition adopts a denser cloth of 0.6m, the flange plate adopts 0.9m cloth, the lateral spacing of the support uprights is 0.7m at the bottom plate and 1.0m at the flange plate, and the pitch of the longitudinal and transverse horizontal bars is set to 1.2m.

[0041] It should be noted that in order to ensure the stability and safety of the support system during construction, the design of the full-floor support follows specific specifications. The longitudinal spacing of the support uprights is 0.6m-0.9m, the bottom plate cross partition adopts a denser 0.6m system, and the flange plate adopts a 0.9m system. In terms of transverse spacing, the bottom plate is 0.7m, the flange plate is 1.0m, and the pitch of the longitudinal and transverse horizontal bars is set to 1.2m. This layout can effectively disperse the load and ensure construction safety.

[0042] Among them, the bottom formwork adopts 1.5cm thick high-strength bamboo plywood, which is fixed by 10×10cm square wooden cross ribs with a spacing of 25cm; the longitudinal ribs adopt double rows of scaffolding steel pipes with a spacing of 90cm, and 300×20×5cm wooden boards are laid on the top support of the bracket. The side walls and top surface formwork of the inner formwork adopt 1.5cm thick plywood. The inner formwork is connected to the beam steel bars with tension rods every 2m, and a 1.0m×1.0m working hole is reserved in the middle of the span of each box chamber.

[0043] It should be noted that the bottom formwork uses 1.5cm thick high-strength bamboo plywood, which is fixed by 10×10cm square wooden cross ribs with a spacing of 25cm; the longitudinal ribs use double rows of scaffolding steel pipes with a spacing of 90cm, and 300×20×5cm wooden boards are laid on the top support of the bracket. For the side walls and top surface formwork of the inner formwork, 1.5cm thick plywood is also used, and the inner formwork is connected to the beam steel bars with tension rods every 2m. A 1.0m×1.0m working hole is reserved in the middle of the span of each box chamber to facilitate construction operations.

[0044] Among them, the side formwork usually adopts composite steel plates, with sealing sponge strips or rubber waterstop strips added at the joints, and the sides are reinforced with diagonal braces with a spacing of 0.6m. The top formwork adopts 1.5cm thick bamboo plywood, which is fixed by 10×10cm square wooden cross ribs with a spacing of 25cm; the longitudinal ribs adopt double rows of scaffolding steel pipes with a spacing of 90cm.

[0045] It should be noted that the side formwork is usually made of composite steel plates, with sealing sponge strips or rubber waterstops installed at the joints to ensure waterproof performance. The sides are reinforced with diagonal braces with a spacing of 0.6m. The top formwork is fixed with the same 1.5cm thick bamboo plywood and 10×10cm square wood cross ribs as the bottom formwork, with the same spacing of 25cm; the longitudinal ribs are made of double-row scaffolding steel pipes with a spacing of 90cm. This structure not only ensures the strength of the formwork, but also improves construction efficiency.

[0046] Among them, the monitoring equipment includes cameras, and the cameras are cleaned every day. The nozzles in the intelligent spray maintenance system are installed around the beam body, which can evenly spray fine water mist to cover the entire concrete surface. The intelligent spray maintenance system also includes sensors installed on the concrete surface and its surrounding environment for real-time monitoring of temperature and humidity in the air.

[0047] It should be noted that during the entire construction process, monitoring equipment such as cameras were installed and cleaned every day to ensure the effect of real-time monitoring. The nozzles in the intelligent spray curing system are installed around the beam body, which can evenly spray fine water mist to cover the entire concrete surface. At the same time, the system is also equipped with sensors for real-time monitoring of temperature and humidity in the air to adapt to different environmental conditions and ensure the quality of concrete curing.

[0048] During the vacuum-assisted grouting process, the pressure in the channel is reduced to 0.06-0.08 MPa, that is, the vacuum degree reaches -60-80 kP, and the vacuum state in the channel is maintained for at least 2 minutes before grouting.

[0049] It should be noted that during the prestressed construction stage, when the top slab concrete reaches the specified strength, the prestressed steel strands will be threaded and tensioned. During this process, vacuum-assisted grouting technology is used, and the pressure in the channel is reduced to 0.06~0.08MPa (that is, the vacuum degree reaches -60~-80kPa), and the vacuum state in the channel is maintained for at least 2 minutes before grouting. The application of this technology greatly improves the quality of grouting and enhances the fixing effect of the prestressed steel strands.

[0050] Among them, the pipeline system in step S6 is shared with the intelligent spray maintenance system. In windy weather conditions, the spraying frequency is increased, and closed fences are set up in construction areas with large dust.

[0051] It should be noted that in order to reduce dust pollution during the construction process, especially in the foundation treatment and concrete pouring stages, a pipeline system was designed and shared with the intelligent spray maintenance system. In windy weather conditions, the spraying frequency was increased, and closed enclosures were set up in construction areas with large dust. These measures not only improved the environmental quality of the construction site, but also protected the health of the workers.

[0052] The beneficial effects of the above embodiments are:

[0053] In the foundation treatment stage, deeper foundation reinforcement measures were adopted, such as pile foundations and deep mixing piles, and the replacement thickness was simultaneously increased to more than 150cm, compacted in layers, and the thickness of each layer was controlled at 20-30cm, which effectively solved the problem of uneven settlement that may be caused by complex geological conditions or weak foundations, and ensured the stability of the foundation under long-term loads. In addition, this method introduced a graded loading support pre-loading technology to simulate the maximum load in actual construction. The pre-loading time was not less than 48 hours, which ensured the verticality and flatness of the support and further enhanced the reliability of the entire support system.

[0054] During the construction of the base plate and web, the concrete is poured in layers. The height of each pouring is controlled within 30 cm, and cooling water pipes are embedded in the concrete to reduce the internal temperature and prevent cracks caused by temperature differences. At the same time, the application of the intelligent spray curing system can not only evenly cover the entire concrete surface, but also automatically adjust the spray volume according to the real-time monitored air temperature and humidity, ensuring that the concrete completes the hydration reaction under optimal conditions, thereby improving the quality and durability of the concrete.

[0055] By using steel bar locators and welding fixing points to tie the top plate steel bars, the position of the steel bars is ensured to be accurate, providing a solid foundation for subsequent concrete pouring. In the prestressed construction stage, ultrasonic detection equipment is used to monitor the concrete strength in real time to ensure that the prestressed steel bundles are threaded and tensioned only after reaching the specified strength. Combined with vacuum-assisted grouting technology and anchor sealing, the steel bundles are effectively fixed, enhancing the integrity and bearing capacity of the structure.

[0056] A pipeline system shared with the intelligent spray maintenance system was designed to increase the spraying frequency under windy weather conditions, and closed fences were set up in construction areas with high dust levels, effectively reducing dust pollution during the construction process and improving the environmental quality of the construction site and the health of workers.

[0057] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0058] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for constructing a cast-in-place box girder for a bridge, characterized in that: The following steps are involved: S1 Preparation and foundation construction: First, load treatment is carried out on the foundation. For areas with complex geological conditions, deeper foundation reinforcement measures are adopted. After the foundation treatment is completed, settlement monitoring equipment is installed, and then full-floor supports are built. Then, graded loading supports are pre-loaded after the bottom formwork is installed; S2 bottom plate and web construction: adjust the elevation of the bottom formwork and install the bottom formwork and support, then use the positioning frame to tie and install the bottom plate steel bars, web steel bars and prestressed pipes, then pour the concrete of the bottom plate and web in layers, and perform intelligent spray curing; S3 Inner formwork and top plate construction: Install the inner formwork, inner bracket and top formwork, and then use the steel bar positioner and welding fixing points to tie the top plate steel bars. After the tying is completed, pour the top plate concrete and perform maintenance, and install monitoring equipment for real-time monitoring; S4 prestressed construction: During the top slab concrete curing process, ultrasonic testing equipment is used to monitor the concrete strength in real time. After reaching the specified strength, the prestressed steel strands are threaded, that is, the prestressed steel strands are tensioned, and vacuum-assisted grouting technology and anchor sealing are used to fix the steel strands; S5 Formwork and support removal: After the concrete strength meets the requirements, use soft materials to wrap the disassembly tools to remove the bottom formwork and support; S6 Dust prevention: Design a piping system around the construction area and perform spray dust removal during foundation treatment and concrete pouring.

2. A method for constructing a cast-in-situ box girder for a bridge according to claim 1, characterized in that: In step S1, deeper foundation reinforcement measures are adopted, including pile foundations and deep mixing piles. The replacement thickness is simultaneously increased to more than 150 cm according to the situation, and compacted in layers, with the thickness of each layer controlled at 20-30 cm.

3. A method for constructing a cast-in-situ box girder for a bridge according to claim 1, characterized in that: After the bottom formwork is installed in step S1, the bracket is pre-loaded in a graded loading manner, with the loading amount gradually increasing each time to simulate the maximum load in actual construction. The pre-loading time is not less than 48 hours. After the pre-loading is completed, the verticality and flatness of the bracket are checked.

4. A method for constructing a cast-in-situ box girder for a bridge according to claim 1, characterized in that: In step S2, the concrete of the bottom plate and the web is poured in layers, and the height of each pouring is controlled within 30 cm. At the same time, cooling water pipes are pre-buried in the concrete to reduce the internal temperature of the concrete.

5. A method for constructing a cast-in-situ box girder for a bridge according to claim 1, characterized in that: The longitudinal spacing of the support uprights in the full-floor support is 0.6m-0.9m, the bottom plate cross partition adopts a denser cloth of 0.6m, the flange plate adopts a 0.9m cloth, the lateral spacing of the support uprights is 0.7m at the bottom plate and 1.0m at the flange plate, and the pitch of the longitudinal and transverse horizontal bars is set to 1.2m.

6. A method for constructing a cast-in-situ box girder for a bridge according to claim 1, characterized in that: The bottom formwork adopts 1.5cm thick high-strength bamboo plywood, which is fixed by 10×10cm square wooden cross ribs with a spacing of 25cm; the longitudinal ribs adopt double rows of scaffolding steel pipes with a spacing of 90cm, and 300×20×5cm wooden boards are laid on the top support of the bracket. The side walls and top surface formwork of the inner formwork adopt 1.5cm thick plywood. The inner formwork is connected to the beam body steel bars with tension rods every 2m, and a 1.0m×1.0m working hole is reserved in the middle of the span of each box chamber.

7. A method for constructing a cast-in-situ box girder for a bridge according to claim 1, characterized in that: The side formwork usually adopts composite steel plates, with sealing sponge strips or rubber waterstop strips added at the joints, and the sides are reinforced with diagonal braces with a spacing of 0.6m. The top formwork adopts 1.5cm thick bamboo plywood, which is fixed by 10×10cm square wooden cross ribs with a spacing of 25cm; the longitudinal ribs adopt double rows of scaffolding steel pipes with a spacing of 90cm.

8. The method for constructing a cast-in-situ box girder for a bridge according to claim 1, characterized in that: The monitoring equipment includes a camera, and the camera is cleaned every day. The nozzles in the intelligent spray maintenance system are installed around the beam body and can evenly spray fine water mist to cover the entire concrete surface. The intelligent spray maintenance system also includes a sensor installed on the concrete surface and its surrounding environment for real-time monitoring of the temperature and humidity in the air.

9. A method for constructing a cast-in-situ box girder for a bridge according to claim 1, characterized in that: During the vacuum-assisted grouting process, the pressure in the pores is reduced to 0.06-0.08 MPa, that is, the vacuum degree reaches -60-80 kP, and the vacuum state in the pores is maintained for at least 2 minutes before grouting.

10. A method for constructing a cast-in-situ box girder for a bridge according to claim 1, characterized in that: In step S6, the pipeline system is shared with the intelligent spray maintenance system. In windy weather conditions, the spraying frequency is increased, and closed enclosures are set up in construction areas with large dust.

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