Three-span continuous beam-arch combined system bridge superstructure system conversion method

Abstract

The invention discloses a three-span continuous beam-arch combined system bridge superstructure system conversion method, and relates to the technical field of bridge engineering construction, and the method comprises the following steps: building a temporary support system; erecting and connecting a beam body; installing and tensioning the arch structure; implementing system conversion; and follow-up structure construction and acceptance check are conducted, construction of a bridge deck system and accessory structures is completed, and the stress state and linear indexes of the beam-arch combined system are comprehensively detected. According to the method, temporary support arrangement and a pre-pressing scheme are optimized by combining stress analysis, the support stability is improved, accurate control over beam body connection is achieved through symmetrical hoisting and strain monitoring, graded unloading quantitative calculation is completed based on a load distribution algorithm, stable stress is guaranteed, a displacement and stress two-dimensional monitoring system is built, and a quantitative standard is defined; through prestress loss multi-factor calculation compensation, the tensioning control stress is accurately determined, multi-link cooperative power generation is achieved, the defects of a traditional technology are effectively avoided, and finally efficient, safe and high-precision construction of a cooperative stress system is achieved.

Description

Technical Field

[0001] This invention relates to the field of bridge engineering construction technology, specifically to a method for converting the superstructure system of a three-span continuous beam-arch composite bridge. Background Technology

[0002] With the development of transportation infrastructure towards longer spans and heavier loads, three-span continuous beam-arch composite bridges, due to their combination of high beam bending stiffness and excellent arch bearing capacity, effectively improve bridge spanning capacity and load-bearing efficiency. They are widely used in key projects such as highways and intercity railways. The core and critical process for this type of bridge is the superstructure system conversion, which essentially involves a smooth transition from a temporary stress state to a beam-arch collaborative stress design state through the placement and unloading of temporary supports. The quality of the system conversion directly determines the long-term stability, safety, and service life of the bridge structure. Currently, the existing methods for converting the superstructure system of three-span continuous beam-arch composite bridges have formed a preliminary technical framework. However, in practical engineering applications, many technical bottlenecks still need to be addressed to meet the demand for "efficient, safe, and high-precision construction of the collaborative stress system."

[0003] First, the design and construction of the temporary support system lack scientific rigor. Second, the stability and precision of the beam erection and connection process are poor. The beam segment hoisting often adopts unilateral advancement or asymmetrical construction techniques, which can easily lead to concentrated loads on one side of the temporary support and cause support instability. Third, the unloading and monitoring control of the system transition lack precise means. The existing unloading process mostly relies on experience to determine the unloading amount and unloading sequence, without establishing a scientific load distribution algorithm. This can easily lead to excessively fast unloading rates or uneven load distribution, resulting in sudden changes in the stress on the beam-arch structure and making it impossible to achieve a smooth transition. Fourth, the whole-process quality assurance system is imperfect.

[0004] In summary, existing superstructure conversion technologies for three-span continuous beam-arch composite bridges have significant shortcomings in areas such as temporary support optimization, precise control of beam connections, scientific management of system conversion, and quality assurance throughout the entire process. These shortcomings make it difficult to meet the core requirements of modern bridge engineering for the construction of collaborative force-bearing systems that are "efficient, safe, and highly precise." Therefore, developing a system conversion method that can systematically solve the above problems has become a technical challenge that urgently needs to be addressed in the field of bridge engineering. Summary of the Invention

[0005] To address the aforementioned technical problems, a method for converting the superstructure of a three-span continuous beam-arch composite bridge is provided. This technical solution resolves the problems mentioned above.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for converting the superstructure of a three-span continuous beam-arch composite bridge, the specific conversion process of which is as follows:

[0008] S1. Temporary support system construction: Based on the bridge span size, beam self-weight and construction load, temporary piers and support devices are set up between the piers. The temporary support is set up at the ends of each span beam and key stress points in the middle of the span to ensure that the strength and stiffness of the support structure meet the temporary bearing requirements of the beam.

[0009] S2. Beam erection and connection: The precast beam segments are hoisted onto temporary supports, and the beam segments are spliced ​​according to the design sequence. The beam continuity is achieved through welding or prestressed connection processes. The beam alignment is adjusted simultaneously to ensure that the beam axis deviation meets the specifications.

[0010] S3. System conversion implementation: The force system conversion is completed by unloading temporary supports in stages, and the internal force and deformation data of the beam-arch composite structure are monitored simultaneously until the temporary supports are completely detached from the beam, forming a design system in which the beam and arch share the load.

[0011] S4. Subsequent structural construction and acceptance: Complete the construction of the bridge deck system and ancillary structures, and conduct comprehensive testing on the stress state and alignment indicators of the beam-arch composite system to ensure that it meets the design and specification requirements.

[0012] The preferred method for setting up a temporary support system is as follows:

[0013] The temporary piers are constructed using steel pipe piles or concrete casting. An adjustable top support is installed on the top of the support device for fine-tuning the beam elevation. The layout density and bearing capacity of the temporary supports are determined according to the weight and stress distribution of the beam segments, and the spacing between adjacent temporary supports does not exceed the design limit. After the temporary supports are erected, a pre-loading test is conducted to eliminate inelastic deformation of the structure. The pre-loading load is 1.2 times the design load. After the pre-loading stabilizes, the support settlement data is recorded.

[0014] Preferably, the beam erection and connection process is as follows: The beam segment hoisting adopts a symmetrical construction process, progressing gradually from both ends of the bridge towards the middle or from the middle towards both ends, to avoid excessive load on one side leading to temporary support instability; before splicing the beam segments, the joint area is cleaned to ensure the contact surface is flat and clean; during welding connections, the welding sequence and temperature are controlled to reduce welding stress; during prestressed connection, prestress is applied according to the designed tensioning sequence; during tensioning, the beam strain is monitored to ensure accurate prestressing; and after tensioning, grouting of the ducts is carried out promptly.

[0015] Preferably, during the system conversion process, the unloading amount of temporary supports needs to be calculated using a load distribution algorithm. The formula for the load distribution algorithm is as follows:

[0016]

[0017] In the formula, For the first Temporary support unloading volume at level 1 The total self-weight of the beam-arch composite structure. For the first Level 1 support load distribution factor (determined based on support location and structural stiffness, with a value range of 0.1-0.3). The total number of unloading stages (value 3-5); temporary support unloading is carried out in 3-5 stages, the unloading amount of each stage is calculated according to the above formula, and the unloading amount of each stage does not exceed 30% of the total unloading amount. After each stage of unloading is completed, it is left to stand for 12-24 hours.

[0018] During the unloading process, strain sensors and displacement gauges are used to monitor the key sections of the beam at mid-span, support, and arch rib. The monitoring frequency is once per hour. If the monitoring data changes abruptly, the unloading is stopped immediately, the cause is analyzed, and adjustment measures are taken.

[0019] The unloading sequence follows the principle of first the middle span and then the support points, and first the side spans and then the middle span, to ensure a smooth transition of the beam-arch structure under stress until the temporary supports are completely unloaded and the beam-arch collaborative stress system is formed.

[0020] Preferably, the monitoring data control standards are as follows:

[0021] The maximum allowable vertical displacement of the beam is 1 / 1000 of the span, and does not exceed 20 mm. The maximum allowable strain of the arch rib needs to be verified by the stress calculation formula, which is as follows:

[0022]

[0023] In the formula, The stress value corresponding to the maximum strain in actual monitoring of the arch rib. The tensile strength of the arch rib material is designed. When the monitoring data exceeds the allowable value, the system conversion is suspended. The problem is addressed by temporarily supporting the top or adjusting the unloading speed. Construction can continue only after the data stabilizes within the allowable range.

[0024] Preferably, the subsequent structural construction and acceptance process is as follows: the bridge deck system construction is carried out after the system conversion is completed and the structure is stable. The construction sequence proceeds from bridge deck paving to ancillary facilities in turn to avoid concentrated construction loads. During the acceptance phase, the alignment, internal forces, connection quality and durability indicators of the beam-arch composite system are tested. Ultrasonic testing is used to test the quality of welded joints, and the rebound method is used to test the concrete strength.

[0025] Preferably, the following quality control measures are adopted throughout the conversion process: a three-level quality inspection system is established, including self-inspection by the construction team, inspection by technical personnel, and special inspection by the supervision unit, with on-site supervision implemented for key processes; incoming inspection of construction raw materials and components is carried out, and materials such as steel, cement, and prestressed tendons must be provided with quality qualification certificates and can only be used after passing the inspection; emergency plans are prepared, and measures are formulated to deal with emergencies such as temporary support instability and excessive structural deformation, and emergency supplies and equipment are provided to ensure construction safety.

[0026] Preferably, during the prestressing tensioning of the beam, the actual tensioning control stress needs to be determined through prestress loss calculation. The formula for calculating prestress loss is as follows:

[0027]

[0028] In the formula, This represents the actual tension control stress of the prestressed tendons. To design the tension control stress for prestressed tendons, For the first Prestress loss value, This represents the number of prestress loss terms (values ​​range from 4 to 6).

[0029] Based on the calculated actual tension control stress, prestressing construction is carried out according to this stress value to ensure that the prestressing of the beam is applied accurately and meets the structural stress requirements.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. A combined optimization scheme of "adjustable top support + 1.2 times design load preloading" is proposed, which breaks through the limitations of traditional temporary support relying solely on experience. The adjustable top support enables dynamic fine-tuning of the beam elevation, and the 1.2 times design load preloading precisely eliminates the inelastic deformation of the support. At the same time, the support layout density is scientifically determined based on the segmental weight and stress distribution of the beam. This ensures that the strength and stiffness of the support structure meet the temporary bearing requirements, while avoiding insufficient bearing capacity or waste of resources, significantly improving the safety and economy of the temporary support system.

[0032] 2. Construct a three-in-one beam connection technology system integrating "symmetrical hoisting + welding stress control + prestressed strain monitoring". Symmetrical hoisting is employed to balance temporary support loads and avoid instability risks caused by excessive load on one side; controlling welding sequence and temperature reduces residual stress at joints, lowering the risk of joint cracking; and beam strain monitoring during prestressing achieves precise closed-loop control, solving multi-dimensional problems commonly found in traditional beam connections, such as support instability, poor joint quality, and inaccurate prestressing application.

[0033] 3. Optimize the load distribution algorithm, clarify the support load distribution coefficient, the total number of unloading stages, and the single-stage unloading limit, and provide a static resting requirement of 12-24 hours after each unloading stage to achieve quantitative control of staged unloading, ensure a smooth transition of stress, establish a dual-dimensional monitoring and control standard for displacement and stress, clarify the dual limits of vertical displacement of the beam, quantify the safety threshold of arch rib stress through stress verification formula, and construct an emergency response mechanism for exceeding the threshold to solve the shortcomings of traditional monitoring that is singular, lacks quantitative standards and emergency plans, and improve the safety of system transition.

[0034] 4. Construct a multi-factor compensation model for prestress loss, incorporating 4-6 prestress loss factors through a quantitative formula system to accurately calculate the actual tension control stress. Compared with the traditional method of tensioning only according to the design value, this model can effectively compensate for prestress loss during construction, solve the problem of reduced beam load-bearing capacity caused by insufficient prestress, and significantly improve the stability and durability of the beam structure.

[0035] 5. Integrate multi-dimensional quality and safety control measures to form a full-process guarantee system, improve the three-level quality inspection system, implement on-site supervision of key processes, strengthen process control, strictly inspect raw materials upon arrival, ensure material quality traceability, and develop targeted emergency plans for sudden situations such as temporary support instability and excessive deformation, and equip emergency supplies and equipment; through multi-link collaborative control, avoid the problems of incomplete quality and safety hazard investigation and insufficient emergency response in traditional construction, and ensure that the entire construction process is safe and controllable. Attached Figure Description

[0036] Figure 1 This is a flowchart of the steps of the present invention. Detailed Implementation

[0037] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0038] Reference Figure 1 As shown, a method for converting the superstructure of a three-span continuous beam-arch composite bridge is presented. The specific conversion process is as follows:

[0039] S1. Temporary support system construction: Based on the bridge span size, beam self-weight and construction load, temporary piers and support devices are set up between the piers. The temporary support is set up at the ends of each span beam and key stress points in the middle of the span to ensure that the strength and stiffness of the support structure meet the temporary bearing requirements of the beam.

[0040] S2. Beam erection and connection: The precast beam segments are hoisted onto temporary supports, and the beam segments are spliced ​​according to the design sequence. The beam continuity is achieved through welding or prestressed connection processes. The beam alignment is adjusted simultaneously to ensure that the beam axis deviation meets the specifications.

[0041] S3. System conversion implementation: The force system conversion is completed by unloading temporary supports in stages, and the internal force and deformation data of the beam-arch composite structure are monitored simultaneously until the temporary supports are completely detached from the beam, forming a design system in which the beam and arch share the load.

[0042] S4. Subsequent structural construction and acceptance: Complete the construction of the bridge deck system and ancillary structures, and conduct comprehensive testing on the stress state and alignment indicators of the beam-arch composite system to ensure that it meets the design and specification requirements.

[0043] The process of setting up the temporary support system is as follows:

[0044] The temporary piers are constructed using steel pipe piles or concrete casting. An adjustable top support is installed on the top of the support device for fine-tuning the beam elevation. The layout density and bearing capacity of the temporary supports are determined according to the weight and stress distribution of the beam segments. The spacing between adjacent temporary supports does not exceed the design limit. After the temporary supports are erected, a pre-loading test is conducted to eliminate inelastic deformation of the structure. The pre-loading load is 1.2 times the design load. After the pre-loading stabilizes, the support settlement data is recorded.

[0045] An adjustable top support combined with a 1.2 times design load preloading scheme is adopted. The adjustable top support enables dynamic fine-tuning of the beam elevation, and the 1.2 times preloading load accurately eliminates the inelastic deformation of the support. At the same time, the support layout density is determined by combining the segmental weight and stress distribution of the beam, avoiding the insufficient load-bearing capacity or waste of resources caused by the traditional support relying solely on experience, thus improving the safety and economy of the temporary support system.

[0046] The beam erection and connection process is as follows: The beam segments are hoisted using a symmetrical construction technique, progressing gradually from both ends of the bridge towards the middle or from the middle towards both ends, to avoid excessive load on one side leading to temporary support instability; before splicing the beam segments, the joint areas are cleaned to ensure the contact surfaces are flat and clean; during welding connections, the welding sequence and temperature are controlled to reduce welding stress; during prestressed connections, prestress is applied according to the designed tensioning sequence, and the beam strain is monitored during tensioning to ensure accurate prestressing; after tensioning, grouting of the ducts is carried out promptly.

[0047] A three-pronged beam connection technology is proposed, which combines symmetrical hoisting, welding stress control, and prestressed strain monitoring. The symmetrical hoisting process balances the temporary support load, the welding sequence and temperature control reduce the residual stress in the joints, and the prestressing tensioning combined with beam strain monitoring achieves closed-loop control of tensioning accuracy. This technology solves many problems that are prone to occur in traditional beam connections, such as support instability, joint cracking, and insufficient prestress.

[0048] During the system conversion process, it is necessary to calculate the staged unloading amount of temporary supports using a load distribution algorithm. The formula for the load distribution algorithm is as follows:

[0049]

[0050] In the formula, For the first Temporary support unloading volume at level 1 The total self-weight of the beam-arch composite structure. For the first Level 1 support load distribution factor (determined based on support location and structural stiffness, with a value range of 0.1-0.3). The total number of unloading stages (value 3-5); temporary support unloading is carried out in 3-5 stages, the unloading amount of each stage is calculated according to the above formula, and the unloading amount of each stage does not exceed 30% of the total unloading amount. After each stage of unloading is completed, it is left to stand for 12-24 hours.

[0051] During the unloading process, strain sensors and displacement gauges are used to monitor the key sections of the beam at mid-span, support, and arch rib. The monitoring frequency is once per hour. If the monitoring data changes abruptly, the unloading is stopped immediately, the cause is analyzed, and adjustment measures are taken.

[0052] The unloading sequence follows the principle of first the middle span and then the support points, and first the side spans and then the middle span, to ensure a smooth transition of the beam-arch structure under stress until the temporary supports are completely unloaded and the beam-arch collaborative stress system is formed.

[0053] The monitoring data control standards are as follows:

[0054] The maximum allowable vertical displacement of the beam is 1 / 1000 of the span, and does not exceed 20 mm. The maximum allowable strain of the arch rib needs to be verified by the stress calculation formula, which is as follows:

[0055]

[0056] In the formula, The stress value corresponding to the maximum strain in actual monitoring of the arch rib. The tensile strength of the arch rib material is designed. When the monitoring data exceeds the allowable value, the system conversion is suspended. The problem is addressed by temporarily supporting the top or adjusting the unloading speed. Construction can continue only after the data stabilizes within the allowable range.

[0057] A dual-dimensional monitoring and control standard for displacement and stress is constructed to clarify the dual limits of vertical displacement of the beam. The stress safety threshold of the arch rib is quantified through stress verification formula. At the same time, an emergency response mechanism for exceeding the threshold is established to solve the problem that traditional monitoring only focuses on a single indicator and lacks quantitative standards and emergency plans, thereby improving the safety of system transformation.

[0058] The subsequent structural construction and acceptance process is as follows: the bridge deck construction will be carried out after the system conversion is completed and the structure is stable. The construction sequence will proceed from the bridge deck paving to the ancillary facilities in turn to avoid the concentration of construction loads. During the acceptance phase, the alignment, internal forces, connection quality and durability indicators of the beam-arch composite system will be tested. Ultrasonic testing will be used to test the quality of welded joints, and the rebound method will be used to test the concrete strength.

[0059] The following quality control measures were adopted throughout the conversion process: a three-level quality inspection system was established, including self-inspection by construction teams, inspection by technical personnel, and special inspection by the supervision unit, with on-site supervision implemented for key processes; incoming inspection of construction raw materials and components was carried out, and materials such as steel, cement, and prestressed tendons were required to provide quality certificates and could only be used after passing inspection; emergency plans were prepared, and measures were formulated to deal with emergencies such as temporary support instability and excessive structural deformation, and emergency supplies and equipment were provided to ensure construction safety.

[0060] During the prestressing tensioning of the beam, the actual tensioning control stress needs to be determined through prestress loss calculation. The formula for calculating prestress loss is as follows:

[0061]

[0062] In the formula, This represents the actual tension control stress of the prestressed tendons. To design the tension control stress for prestressed tendons, For the first Prestress loss value, This represents the number of prestress loss terms (values ​​range from 4 to 6).

[0063] Based on the calculated actual tension control stress, prestressing tensioning is carried out according to this stress value to ensure that the prestressing of the beam is applied accurately and meets the structural stress requirements.

[0064] A multi-factor compensation model for prestress loss is constructed, incorporating 4-6 prestress loss factors into the formula system to accurately calculate the actual tension control stress, compensate for the prestress loss caused by traditional tensioning based solely on design values, solve the problem of reduced load-bearing capacity caused by insufficient prestress in beams, and improve the stability and durability of beam structures.

[0065] In summary, the advantages of this invention are as follows:

[0066] By introducing a load distribution algorithm formula to calculate the unloading amount of temporary supports in stages, the quantitative relationship between the unloading amount of each stage and the total self-weight of the structure and the load distribution coefficient is clarified, avoiding sudden changes in internal forces caused by empirical unloading, so that the stress of the beam-arch structure can be smoothly transitioned and the internal force distribution of the completed bridge can better meet the design requirements.

[0067] The installation position of the arch rib is corrected in real time by using the linear deviation correction formula to ensure that the deviation of the arch rib axis is controlled within 5mm. The actual tension control stress is accurately calculated by the prestress loss calculation formula to compensate for the prestress loss caused by multiple factors, ensure the accuracy of prestress application of the beam and arch structure, and improve the overall stiffness and load-bearing capacity of the structure.

[0068] Establish a linkage mechanism of monitoring, early warning and adjustment, clarify the stress control threshold of the arch rib through stress calculation formula, combine it with the vertical displacement limit of the beam, monitor the structural deformation and internal force state in real time during the system transformation process, deal with abnormal situations in a timely manner, and reduce safety risks such as temporary support instability and excessive structural deformation.

[0069] Clearly define the technical parameters and operating standards for key processes such as temporary support layout, beam splicing, and arch structure installation. In conjunction with a three-level quality inspection system and raw material inspection requirements, a standardized construction process can be formed to reduce human error and improve construction efficiency and project quality pass rate.

[0070] Through precise system conversion control, the beam-arch composite structure forms a synergistic stress-bearing system, avoiding local stress concentration and reducing the risk of early structural damage. At the same time, the improved precision of prestressing application and alignment control can reduce the occurrence of bridge defects during the operational phase, extend the long-term service life of the bridge, and reduce later maintenance costs.

[0071] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A method for converting the superstructure system of a three-span continuous beam-arch composite bridge, characterized in that, The specific conversion process is as follows: S1. Temporary support system construction: Based on the bridge span dimensions, beam self-weight and construction load, temporary piers and support devices are set up between the piers. The temporary support locations include the ends of each span beam and key stress points in the middle of the span. S2. Beam erection and connection: The precast beam segments are hoisted onto temporary supports, and the beam segments are spliced ​​according to the design sequence. The beam continuity is achieved through welding or prestressed connection processes, and the beam alignment is adjusted simultaneously. S3. System conversion implementation: The force system conversion is completed by unloading temporary supports in stages, and the internal force and deformation data of the beam-arch composite structure are monitored simultaneously until the temporary supports are completely detached from the beam, forming a design system in which the beam and arch share the load. S4. Subsequent structural construction and acceptance: Complete the construction of the bridge deck system and ancillary structures, and conduct a comprehensive test on the stress state and alignment indicators of the beam-arch composite system.

2. The method for converting the superstructure system of a three-span continuous beam-arch composite bridge according to claim 1, characterized in that, The process of setting up the temporary support system is as follows: The temporary piers are constructed using steel pipe piles and concrete. The top of the support device is equipped with an adjustable top support for fine-tuning the beam elevation. The layout density and bearing capacity of the temporary supports are determined according to the weight and stress distribution of the beam segments, and the spacing between adjacent temporary supports does not exceed the design limit. After the temporary supports are erected, a pre-stressing test is conducted to eliminate inelastic deformation of the structure. The pre-stressing load is 1.2 times the design load, and the support settlement data is recorded.

3. The method for converting the superstructure system of a three-span continuous beam-arch composite bridge according to claim 1, characterized in that, The beam erection and connection process is as follows: The beam segment hoisting adopts a symmetrical construction process, advancing from both ends of the bridge towards the middle to avoid excessive load on one side leading to temporary support instability; the joint area is cleaned before beam segment splicing, and prestress is applied according to the designed tensioning sequence during prestressed connection. The beam strain is monitored during tensioning, and grouting of the ducts is carried out in a timely manner after tensioning is completed.

4. The method for converting the superstructure system of a three-span continuous beam-arch composite bridge according to claim 1, characterized in that, During the system conversion process, it is necessary to calculate the staged unloading amount of temporary supports using a load distribution algorithm. The formula for the load distribution algorithm is as follows: ； In the formula, For the first Temporary support unloading volume at level 1 The total self-weight of the beam-arch composite structure. For the first Level support load distribution factor, To unload the total number of levels, This is the sum of the support load distribution coefficients corresponding to all unloading levels; During the unloading process, strain sensors and displacement gauges were used to monitor the key sections of the beam at mid-span, supports, and arch ribs. The unloading sequence follows the principle of first the middle span and then the support points, and first the side spans and then the middle span, to ensure a smooth transition of the beam-arch structure under stress until the temporary supports are completely unloaded and the beam-arch collaborative stress system is formed.

5. The method for converting the superstructure system of a three-span continuous beam-arch composite bridge according to claim 4, characterized in that, The monitoring data control standards are as follows: The maximum allowable vertical displacement of the beam is 1 / 1000 of the span, and does not exceed 20 mm. The maximum allowable strain of the arch rib needs to be verified by the stress calculation formula, which is as follows: ； In the formula, The stress value corresponding to the maximum strain in actual monitoring of the arch rib. Design the tensile strength for the arch rib material.

6. The method for converting the superstructure system of a three-span continuous beam-arch composite bridge according to claim 1, characterized in that, The subsequent structural construction and acceptance process is as follows: the bridge deck construction will be carried out after the system conversion is completed and the structure is stable. The construction sequence will proceed from the bridge deck paving to the ancillary facilities in turn to avoid the concentration of construction loads. During the acceptance phase, the alignment, internal forces, connection quality and durability indicators of the beam-arch composite system will be tested. Ultrasonic testing will be used to test the quality of welded joints, and the rebound method will be used to test the concrete strength.

7. The method for converting the superstructure system of a three-span continuous beam-arch composite bridge according to claim 1, characterized in that, The following quality control measures were adopted throughout the conversion process: a three-level quality inspection system was established, including self-inspection by construction teams, inspection by technical personnel, and special inspection by the supervision unit, with on-site supervision implemented for key processes; incoming inspection of construction raw materials and components was carried out, and steel, cement, and prestressed tendon materials were required to provide quality certificates and could only be used after passing the inspection; emergency plans were prepared, and measures were formulated to deal with sudden situations such as temporary support instability and excessive structural deformation, and emergency supplies and equipment were provided.

8. The method for converting the superstructure system of a three-span continuous beam-arch composite bridge according to claim 1, characterized in that, During the prestressing tensioning of the beam, the actual tensioning control stress needs to be determined through prestress loss calculation. The formula for calculating prestress loss is as follows: ； In the formula, This represents the actual tension control stress of the prestressed tendons. To design the tension control stress for prestressed tendons, For the first Prestress loss value, This represents the number of prestress loss terms; Based on the calculated actual tension control stress, prestressing construction is carried out according to this stress value to ensure that the prestressing of the beam is applied accurately and meets the structural stress requirements.

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