Construction method for suspended pouring beam hanging basket of high-pier large-span extra-large bridge

Abstract

The invention discloses a high-pier large-span extra-large bridge suspended pouring beam hanging basket construction method, and belongs to the field of bridge engineering construction.The method comprises the following steps that hanging basket rails are installed, the precision is controlled, and a hanging basket comprising a double-channel-steel main truss, a manganese steel sling, an arc-shaped flow guide plate and a honeycomb formwork is assembled; grading pre-pressing is carried out according to the specified multiple of the design load, and the pre-camber of the template is corrected by adopting a BP neural network to ensure that the finished bridge linear error meets the requirement; a mechanical-hydraulic-electrical integrated intelligent control system is deployed, and the traveling speed and synchronism of the hanging basket are controlled through double-oil-cylinder driving, a 5G digital twin platform and an edge computing technology, so that rapid alarm is realized when the load is abnormal; segmental circulation construction is carried out, and when the environment wind speed reaches a set value, a hydraulic rail clamping device is automatically locked; a model is established by using ANSYS software, and simulation verification is performed on multiple types of key working conditions to ensure that the safety coefficient of the structure meets the specification requirement. The construction precision and safety are guaranteed, and the method adapts to complex environments.

Description

Technical Field

[0001] This invention relates to the field of bridge engineering construction technology, and more specifically to a method for constructing a cantilever beam of a large-span, high-pier bridge using a formwork system. Background Technology

[0002] In the construction of high-pier, long-span bridges, the hanging basket construction technology is widely used due to its strong adaptability and high efficiency. However, traditional hanging baskets present numerous problems when facing complex terrain, heavy loads, and harsh environments such as strong winds. Insufficient wind resistance makes them prone to flutter under strong winds, threatening construction safety; low synchronization control precision, with large synchronization errors in multiple hydraulic cylinders leading to formwork misalignment and affecting construction quality; poor adaptability to heavy loads, making it difficult to meet the needs of large bridge construction and resulting in low construction efficiency. Furthermore, the traditional hanging basket structure is relatively heavy, increasing the difficulty of high-altitude assembly, and deformation control during construction is challenging, making it difficult to guarantee the accuracy of beam forming. These problems restrict the safety, efficiency, and quality of high-pier, long-span bridge construction, necessitating a new hanging basket construction method to address these issues. Summary of the Invention

[0003] The purpose of this invention is to address the technical problems existing in the construction of cantilever beams for high-pier, long-span, extra-large bridges using formwork, such as insufficient wind resistance, low synchronous control accuracy, poor adaptability to large-tonnage loads, difficulty in deformation control, and low construction efficiency. This invention provides a method for constructing cantilever beams for high-pier, long-span, extra-large bridges using formwork.

[0004] The technical solution adopted in this invention is as follows: A method for constructing a cantilever beam with hanging basket for a high-pier, long-span, extra-large bridge, comprising the following steps:

[0005] S1. Construction preparation and hanging basket system construction: Install hanging basket tracks on both sides of the bridge pier and control the installation accuracy; assemble the hanging basket in the order of main truss, anchoring system, suspension system and bottom support system. The main truss is optimized for stress to reduce its self-weight. The suspension system uses manganese steel plate slings; set arc-shaped guide plates on the outside of the main truss. The template inside the hanging basket adopts a honeycomb hollow structure.

[0006] S2. Preloading and Deformation Control of Hanging Formwork: The hanging formwork is subjected to graded loading with 1.2 times the design load, and the elastic-plastic deformation data of the structure is collected. The precamber of the formwork is corrected and the elastic-plastic deformation reserve is considered to ensure that the alignment error of the completed bridge meets the requirements.

[0007] S3. Intelligent Control and Synchronous Movement: Deploy an integrated mechanical-hydraulic-electrical intelligent control system, including a drive unit, a distributed sensor network, and a digital twin platform; the drive unit controls the walking speed of the hanging basket and ensures synchronization error of multiple cylinders; the distributed sensor network integrates a monitoring unit to achieve rapid alarm response when the load is abnormal; the digital twin platform constructs a three-dimensional model to monitor the stress, displacement, and overturning safety factor of the hanging basket in real time.

[0008] S4. Segmental Cyclic Construction and Environmental Adaptation: Under the control of an intelligent system, segmental cyclic operations such as rebar binding, concrete pouring, prestressing tensioning, and forward movement of the hanging basket are completed; the ambient wind speed is monitored in real time by a wind speed sensor, and the hydraulic rail clamps automatically lock when the wind speed reaches the threshold; construction parameters are dynamically adjusted in combination with pre-operation data.

[0009] S5. Simulation Verification and Safety Control: Before construction, a model is established to conduct simulation verification for the maximum pouring condition, eccentric load condition, strong wind condition, walking condition, and anti-overturning condition, to ensure that the structural safety factor meets the specification limit requirements under each condition.

[0010] Preferably, the main load-bearing structure of the hanging basket in step S1 is configured as follows: the main load-bearing members of the rhomboid truss of the main truss are composed of double channel steel welded together to form a composite section, and the centroid of the topology-optimized section coincides with the load-bearing axis; the front upper crossbeam of the rhomboid truss is made of double steel arranged side by side; the outer and inner sliding beams of the track are both made of double channel steel composite sections and are slidably connected to the main truss; the middle portal chord on the rhomboid truss is made of channel steel, forming a stable spatial triangular support system.

[0011] Preferably, the high-precision installation method of the track in step S1 is as follows: a high-precision laser level is used to scan and monitor the elevation of the top surface of the track throughout the entire process; a wedge-shaped adjustment block is inserted between the track base plate and the embedded part of the beam for fine adjustment to control the longitudinal slope accuracy of the top surface of the track; all high-strength bolt connection nodes are tightened with a hydraulic torque wrench with a preset torque value, and a torque detector is used for spot checks and verification to control torque construction error.

[0012] Preferably, the implementation method of the graded preloading in step S2 is as follows: a set of synchronously controlled hydraulic jacks are used to apply loads synchronously at the front lifting point and the rear anchor point of the hanging basket, and the load value is controlled by real-time feedback from a precision pressure sensor; during the loading process, the deflection of the bottom basket is monitored by a displacement sensor arranged in the middle of the bottom longitudinal beam, and the extreme value of the bottom basket deflection is controlled; after unloading, the elastic deformation recovery rate of the main truss structure is calculated by comparing the displacement data of the key nodes of the main truss before and after loading.

[0013] Preferably, the distributed sensing network in step S3 is configured as follows: strain gauges are arranged at key stress nodes of the main truss of the hanging basket, the front and rear suspension belts, and the longitudinal beams of the bottom basket to measure multidimensional stress states; wire encoders are installed to measure the forward movement of the hanging basket and the vertical displacement of the template; dual-axis tilt sensors are arranged at the front and rear ends and the middle of the hanging basket to monitor the overall attitude of the hanging basket; all sensors collect data synchronously, and the intelligent control system is pre-set with fault logic including sudden changes in hydraulic pressure, abnormal oil temperature, and communication interruption, and can trigger a three-level progressive alarm response of early warning, movement restriction, and emergency stop.

[0014] Preferably, the wind control linkage mechanism of the hydraulic rail clamp in step S4 is as follows: when the wind speed sensor in the environmental monitoring unit detects that the wind speed reaches a preset threshold of 15m / s for 3 consecutive seconds, the intelligent control system immediately sends an electrical signal to the hydraulic rail clamp; the hydraulic rail clamp uses a composite drive method of providing constant braking force with a disc spring and releasing pressure by overcoming the spring force with a hydraulic cylinder; wherein, the disc spring provides a clamping force greater than 500kN and completes rigid locking within 0.3 seconds.

[0015] Preferably, the specific content and qualification criteria of the simulation verification in step S5 are as follows: establish a coupled finite element model of the hanging basket-beam body containing construction details, and calculate and analyze typical working conditions such as maximum pouring, strong wind, walking and anti-overturning; the simulation results require that the maximum combined stress of the main truss and the maximum vertical displacement of the bottom support system be controlled, and the anti-overturning stability safety factor meet the requirements under all working conditions.

[0016] Preferably, the remote transmission and interaction of the data during construction is achieved through 5G communication technology: real-time bidirectional stable transmission of distributed sensor data and control commands deployed on the hanging basket; remote access to the digital twin platform to view the relevant status data and environmental data of the hanging basket in real time.

[0017] Preferably, the intelligent control system is equipped with an automatic safety control mechanism, which is triggered when the distributed sensor network detects that the load eccentricity exceeds the safety threshold. After triggering, the intelligent control system first automatically suspends all travel and concrete pouring operations of the hanging basket, then calls the real-time data of the digital twin platform to perform differential compensation adjustment on the tension of the front and rear slings, and simultaneously increases the hydraulic clamping force of the track anchor points, forming a dynamic adjustment closed loop of multi-actuator linkage. Construction can only be confirmed to resume after the intelligent control system verifies and confirms that the load eccentricity has returned to within the safe range.

[0018] Preferably, after the construction cycle of each standard segment is completed, a machine vision-based alignment monitoring auxiliary process is introduced: a high-precision total station and a laser rangefinder are used to jointly measure the elevation control points and axis deviation of the poured beam segments. The collected measured data is uploaded to the digital twin platform in real time, compared and analyzed with the alignment value predicted by the pre-camber correction model, and the pre-camber setting parameters of the next segment are dynamically iteratively optimized based on the deviation results to ensure that the cumulative alignment error of the completed bridge meets the requirements after the bridge is closed.

[0019] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0020] This invention reduces the windward area and the maximum stress value of the main truss by optimizing the topology of the double-channel steel composite section, using an arc-shaped guide plate and a honeycomb-shaped hollow template. This reduces the self-weight of the hanging basket, lowers the windward area, reduces the maximum stress value of the main truss, improves wind resistance stability, reduces the additional load on the beam, and solves the flutter problem of high-pier bridges under wind load.

[0021] This invention employs technologies such as laser level monitoring and wedge adjustment blocks to achieve high-precision control with small deviations in the track centerline and small misalignments in truss nodes, ensuring uniform stress distribution on the hanging basket structure and reducing the difficulty of high-altitude assembly.

[0022] This invention integrates multi-system collaborative control, using a 5G digital twin platform to monitor key indicators in real time. It features minimal synchronization error between the dual hydraulic cylinders, millisecond-level alarms when load eccentricity exceeds limits, and improved formwork travel speed, thus enhancing construction efficiency. It overcomes the precision limitations of traditional manual operation, achieving full automation of formwork movement and positioning in complex high-altitude environments. Based on a BP neural network algorithm to correct pre-camber, the completed bridge alignment error is small, ensuring high bridge construction quality and a high alignment qualification rate.

[0023] The hydraulic rail clamp of this invention can brake in 0.3 seconds under a wind speed of 15m / s. Combined with multi-condition simulation verification, the uniformity of stress distribution at each key node is improved after optimization, which enables the hanging basket to operate safely in complex environments and improves the reliability and efficiency of construction. Attached Figure Description

[0024] The present invention will be described by way of example and with reference to the accompanying drawings, wherein:

[0025] Figure 1 This is a schematic diagram of the front view of the hanging basket structure of the present invention;

[0026] Figure 2 This is a schematic diagram of the left-side structure of the hanging basket of the present invention;

[0027] Figure 3 This is a schematic diagram of the right-side structure of the hanging basket of the present invention;

[0028] Figure 4 This is a diagram showing the arrangement of measuring points on the preloaded bottom plate of the hanging basket according to the present invention, where (a) is the front view and (b) is the top view;

[0029] Figure 5 This is a diagram showing the arrangement of measuring points on the main truss of the preloaded hanging basket of the present invention, where (a) is the front view and (b) is the top view;

[0030] Figure 6 This is a diagram of the overall computational model;

[0031] Figure 7 These are the finite element mechanical model diagrams of the hanging basket, where (a) is the walking simulation, (b) is the boundary condition simulation, and (c) is the load simulation.

[0032] Figure 8 These are simulation results from the MidasCivil finite element software, where (a) represents the no-load condition and (b) represents the construction condition.

[0033] The diagram is labeled as follows: 1-track, 2-main truss, 3-anchoring system, 4-suspension system, 5-base support system, 20-front hanger measuring point, 20a-first front hanger measuring point, 20b-second front hanger measuring point, 20c-third front hanger measuring point, 20d-fourth front hanger measuring point, 21-arc-shaped guide vane, 22-front support measuring point, 22a-first front support measuring point, 22b-second front support measuring point, 23-rear anchor measuring point, 23a-first rear anchor measuring point. Anchor measuring points: 23b - Second rear anchor measuring point; 24 - First beam measuring point; 25 - Second beam measuring point; 26 - Third beam measuring point; 27 - Fourth beam measuring point; 24a - First rear beam measuring point; 24b - First middle beam measuring point; 24c - First front beam measuring point; 25a - Second rear beam measuring point; 25b - Second middle beam measuring point; 25c - Second front beam measuring point; 26a - Third rear beam measuring point; 26b - Third middle beam measuring point; 26c - Third front beam measuring point. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0036] This embodiment provides a method for constructing a cantilever beam with formwork for a high-pier, long-span, extra-large bridge, including the following steps:

[0037] S1. Construction Preparation and Construction of the Hanging Basket System: Hanging basket tracks 1 are installed on both sides of the bridge pier. The installation accuracy of the tracks is controlled by a laser level, with the deviation of the track centerline less than 3mm and the levelness less than 1‰. Then, the hanging basket is assembled in the order of main truss 2, anchoring system 3, suspension system 4, and bottom support system 5. The main truss 2 adopts a double-channel steel combined section rhombic truss, and the members are topologically optimized through a stress optimization algorithm to reduce self-weight. The suspension system 4 adopts manganese steel plate slings with a cross-sectional size of 30mm×180mm, a yield strength greater than 345MPa, and an impact toughness greater than 27J. At the same time, an arc-shaped guide plate 21 with a curvature radius of 1.2m is set on the outside of the main truss. The template adopts a honeycomb hollow structure with an opening ratio of 15% to optimize the aerodynamic shape and reduce wind resistance.

[0038] S2. Preloading and Deformation Control of Hanging Formwork: The hanging formwork is subjected to graded loading with 1.2 times the design load, applying 20%, 50%, 80%, 100%, and 120% of the design load sequentially, with each load held for 30 minutes. The elastic-plastic deformation data of the structure is collected by sensors, and the precamber of the template is corrected based on the BP neural network algorithm. The precamber correction adopts the calculation mode of the measured elastic deformation value plus 1.1 times the inelastic deformation reserve value to ensure that the bridge alignment error is less than L / 3000, where L is the segment length.

[0039] S3. Intelligent Control and Synchronous Movement: Deploy an integrated mechanical-hydraulic-electrical intelligent control system, including a dual-cylinder rack and pinion drive unit, a distributed sensor network with a sampling rate of 100Hz, and a digital twin platform based on 5G communication; control the traveling speed of the hanging basket at 0.5m / min through a proportional directional valve and a laser ranging module, and use a PID flow closed-loop algorithm to ensure that the synchronization error of the multi-cylinder system is less than ±3mm; the distributed sensor network integrates strain gauges, wire encoders, tilt sensors, and environmental monitoring units, and achieves millisecond-level alarm response when the load eccentricity is greater than 8% based on edge computing technology; the digital twin platform constructs a high-precision three-dimensional model through BIM+GIS fusion technology, monitors the stress, displacement, and overturning safety factor of the hanging basket in real time, and ensures that the maximum stress is less than 215MPa, the displacement deformation is less than L / 500, and the overturning safety factor is greater than 2.0;

[0040] S4. Segmental Cyclic Construction and Environmental Adaptation: Under the control of an intelligent system, segmental cyclic operations are completed, including rebar binding, concrete pouring, prestressing tensioning, and forward movement of the formwork. A wind speed sensor monitors the ambient wind speed in real time. When the wind speed reaches 15 m / s, the hydraulic rail clamps automatically lock using a disc spring-hydraulic composite drive, with a locking force greater than 500 kN and a response time less than 0.3 seconds. During construction, construction parameters are dynamically adjusted based on multi-condition finite element simulation data.

[0041] S5. Simulation Verification and Safety Control: Before construction, a coupled finite element model of the hanging basket and beam is established using ANSYS software. Simulation verification is carried out for the maximum pouring condition, eccentric load condition, level 10 gale condition, walking condition, and anti-overturning condition to ensure that the structural safety factor under each condition is greater than 1.2 times the limit of the specification.

[0042] Preferably, the main load-bearing structure of the hanging basket is configured as follows: the rhomboid truss members are composed of two 40b channel steels welded together; the front upper crossbeam is made of two HN600×200 steel sections; the outer and inner sliding beams are made of 2[40b channel steels; the middle gantry chord is made of 2[12b channel steels; the lower crossbeam is made of 2HN600×200 steel sections; and the lower bottom longitudinal beam is made of HN400×200 steel sections.

[0043] Furthermore, the specific configuration of the main load-bearing structure of the hanging basket in step S1 is as follows: each main load-bearing member of the rhombic truss is composed of two 40b channel steels welded together to form a composite section, the centroid of which after topological optimization coincides with the load-bearing axis; the front upper crossbeam is made of two HN600×200 steels arranged side by side to provide sufficient bending stiffness; both the outer and inner sliding beams are made of 2[40b channel steel composite sections and are slidably connected to the main truss; the middle portal chord is made of 2[12b channel steel to form a stable spatial triangular support system; the lower crossbeam is made of 2HN600×200 steel to bear the concrete load transmitted from the bottom formwork; the lower bottom longitudinal beam is made of HN400×200 steel and is arranged along the longitudinal length of the bridge, together forming a high-strength, lightweight spatial truss structure system with excellent torsional resistance.

[0044] Furthermore, the high-precision installation of the track in step S1 is achieved through the following methods: a high-precision laser level is used to scan and monitor the elevation of the top surface of the track throughout the entire process, and wedge-shaped adjustment blocks of different thicknesses are inserted between the track base plate and the embedded parts of the beam for fine adjustment, ultimately controlling the longitudinal slope accuracy of the top surface of the track to within 1‰; all high-strength bolt connection nodes are tightened using hydraulic torque wrenches with preset torque values, the torque value is strictly set to 120 N·m, and a special torque detector is used for spot checks and verification, controlling the torque construction error within ±5% to ensure reliable force transmission at the connection nodes.

[0045] Furthermore, the specific implementation of the graded preloading in step S2 is as follows: a set of synchronously controlled hydraulic jacks apply loads simultaneously to the front lifting point and rear anchor point of the hanging basket, and the load value is controlled by real-time feedback from a precision pressure sensor; during the loading process, the extreme value of the bottom basket deflection is monitored and controlled within 14.2mm by displacement sensors arranged in the middle of the bottom longitudinal beam span; after unloading, by comparing the displacement data of the key nodes of the main truss before and after loading, the elastic deformation recovery rate of the main truss structure is calculated to be greater than 98%, thereby verifying that the main truss structure is in a good elastic working state and providing a reliable data basis for setting the pre-camber.

[0046] Furthermore, such as Figure 4-5 As shown, the specific structure of the distributed sensor network in step S3 is as follows: a total of 32 strain gauges are arranged at key stress nodes of the main truss of the hanging basket, the front and rear suspension belts, and the longitudinal beams of the bottom basket to measure multidimensional stress states; 16 wire encoders are installed to measure the forward movement of the hanging basket and the vertical displacement of the template; multiple dual-axis tilt sensors with a range of ±15° are arranged at the front and rear ends and the middle of the hanging basket to monitor the overall attitude of the hanging basket; all sensors synchronously collect data at a sampling frequency of 100Hz; the intelligent control system is pre-set with 12 types of fault logic, including hydraulic pressure sudden change (threshold ±15%), oil temperature abnormality (>65℃), and communication interruption, and can trigger a three-level progressive alarm response of early warning, movement restriction, and emergency stop.

[0047] Among them, 32 strain gauges are distributed on the front hanger measuring point 20 on the front upper crossbeam of the symmetrically arranged main truss 1, the front support measuring point 22 on the horizontal truss, the rear anchor measuring point 23 on the rear anchor pressure beam, and the first measuring point 24, the second measuring point 25, the third measuring point 26, and the fourth measuring point 27 on the lower crossbeam.

[0048] The front boom measuring point 20 includes a first front boom measuring point 20a, a second front boom measuring point 20b, a third front boom measuring point 20c, and a fourth front boom measuring point 20d;

[0049] The front support measuring point 22 includes a first front support measuring point 22a and a second front support measuring point 22b;

[0050] The rear anchor measuring point 23 includes a first rear anchor measuring point 23a and a second rear anchor measuring point 23b;

[0051] The first measuring point 24 of the beam includes the first measuring point 24a of the rear beam on the lower rear crossbeam, the first measuring point 24b of the middle beam on the reaction beam, and the first measuring point 24c of the front beam on the front lower crossbeam;

[0052] The second measuring point 25 of the beam includes the second measuring point 25a of the rear beam on the lower rear crossbeam, the second measuring point 25b of the middle beam on the reaction beam, and the second measuring point 25c of the front beam on the front lower crossbeam;

[0053] The third measuring point 26 of the beam includes the third measuring point 26a of the rear beam on the lower rear crossbeam, the third measuring point 26b of the middle beam on the reaction beam, and the third measuring point 26c of the front beam on the front lower crossbeam;

[0054] The fourth measuring point 27 of the beam is set on the front lower crossbeam.

[0055] Furthermore, the wind control linkage mechanism of the hydraulic rail clamp in step S4 is as follows: the wind speed sensor in the environmental monitoring unit collects wind speed and direction data in real time. The wind speed sensor is preferably an ultrasonic anemometer. When the instantaneous wind speed is detected to reach the preset threshold of 15m / s for 3 seconds, the intelligent control system immediately sends an electrical signal to the hydraulic rail clamp. The hydraulic rail clamp adopts a composite drive method in which a disc spring provides constant braking force and the hydraulic cylinder overcomes the spring force to release. After receiving the signal, the hydraulic system quickly depressurizes, and the disc spring provides a clamping force of more than 500kN, so as to complete rigid locking within 0.3 seconds and effectively resist the impact of wind load.

[0056] Furthermore, the specific content and qualification criteria for the simulation verification in step S5 are as follows: A coupled finite element model of the hanging basket and beam, containing all construction details, is established using the ANSYS parametric design language. Seven typical working conditions are calculated and analyzed, including maximum pouring (eccentric load), level 10 wind (32 m / s), walking, and anti-overturning. Simulation results require that the maximum combined stress of the main truss is less than 149.9 MPa (occurring under the maximum eccentric load condition), far less than the yield strength of Q345 steel; the maximum vertical displacement of the bottom support system is less than 16.7 mm (occurring under full load condition), meeting the stiffness requirement of less than L / 500 = 20 mm; and the anti-overturning stability safety factor is greater than 2.0 under all working conditions, verifying the safety and reliability of the hanging basket system under various extreme conditions.

[0057] Furthermore, the remote transmission and interaction of the data during construction is achieved through 5G communication technology: leveraging the low latency (end-to-end latency less than 20ms) and high bandwidth characteristics of the 5G network, the distributed sensor data, high-definition video monitoring images, and control commands deployed on the hanging basket are transmitted in real time, bidirectionally, and stably; on-site management personnel can remotely access the digital twin platform through mobile terminals to view the three-dimensional attitude reconstruction, load distribution cloud map, and environmental data of the hanging basket in real time, providing support for remote and intelligent construction decision-making.

[0058] Furthermore, the intelligent collaborative control system is equipped with an automatic safety control mechanism, which is triggered when the distributed sensor network detects that the load eccentricity exceeds the threshold of 8%. After triggering, the system first automatically suspends all travel and concrete pouring operations of the hanging basket, and then calls the stress cloud map and displacement vector data mapped in real time in the digital twin platform. The system uses the hydraulic servo system to adjust the tension of the front and rear slings differently and simultaneously increases the hydraulic clamping force of the track anchor point, forming a dynamic adjustment closed loop with multiple actuators linked. Construction can only resume manually or automatically after the system verifies that the load eccentricity has returned to within the safe range.

[0059] Furthermore, after each standard segment construction cycle is completed, a machine vision-based alignment monitoring auxiliary process is introduced: a high-precision total station and a laser rangefinder are used to jointly measure the elevation control points and axis deviation of the poured beam segments. The collected measured data is uploaded to the digital twin platform in real time via a 5G network and compared with the alignment value predicted by the BP neural network pre-camber correction model. Based on the deviation results, the pre-camber setting parameters of the next segment are dynamically iterated and optimized to achieve prediction and feedback control of alignment changes throughout the construction process. Ultimately, this ensures that the alignment is smooth after the entire bridge is closed, and the cumulative alignment error of the completed bridge is less than L / 4000.

[0060] Example 1

[0061] Taking the Luoyewan Wushui Grand Bridge as an application example, this bridge is located in Chengnan Village, Rulin Town, Chengbu Miao Autonomous County, Shaoyang City. It spans a deep valley, the Wushui River, and S219. The superstructure is a three-span variable cross-section prestressed concrete continuous box girder (82.5+155+82.5)m (transverse double-span arrangement, each span 12.75m wide; the main girder is a C55 prestressed concrete box girder, consisting of 24 segments, with a standard segment length of 4m (center, i.e., segment length L = 4m below), a maximum girder height of 9m, and a maximum single-segment concrete weight of 209.6t). The main piers are hollow thin-walled piers (maximum pier height 89.2m), and the maximum wind force in the bridge site area is level 8-9. Based on this project background, a cantilever beam formwork construction method for high-pier, large-span grand bridges is provided. The specific steps are as follows:

[0062] S1. Construction Preparation and Construction of Hanging Basket System

[0063] Hanging basket rails 1 were installed on both sides of the main pier (maximum pier height 89.2m). The levelness of the rails was monitored in real time using a laser level and dynamically adjusted by wedge adjustment blocks. The final levelness of the rails was controlled at 0.8‰ (≤1‰), and the deviation of the center line of the rails was measured to be 2.5mm (≤3mm), which met the installation accuracy requirements.

[0064] Then, assemble the hanging basket in the following order: "Main Truss 2 → Anchoring System 3 → Suspension System 4 → Bottom Support System 5":

[0065] The main truss 2 adopts a double-channel steel composite section rhombic truss, and each member is selected from 2〔40b channel steel. The main truss members are topologically optimized by the stress optimization algorithm to determine the optimal section size, which effectively reduces the self-weight of the hanging basket.

[0066] The suspension system 4 uses 30mm×180mm manganese steel plate slings, which have been tested and found to have a yield strength of 350MPa and an impact toughness of 28J, meeting the design load-bearing capacity requirements.

[0067] The main truss nodes are tightened using a torque wrench to a standard of 120 N·m, with the bolt torque error controlled within ±5% and the measured node misalignment being 1.8 mm. The verticality deviation of the slings is controlled within 0.8° during installation, and the tension error is kept ≤ ±2.5% through pre-tightening dynamic calibration technology.

[0068] Meanwhile, an arc-shaped guide plate 21 with a curvature radius of 1.2m is installed on the outside of the truss. The template adopts a honeycomb hollow structure with an opening rate of 15%. According to calculations, the overall weight of the hanging basket is reduced by 8% compared with the traditional hanging basket, and the windward area is reduced by 15%, which effectively optimizes the aerodynamic shape, reduces wind resistance, and is suitable for the 8-9 level gale environment in the bridge site area.

[0069] S2, Hanging basket preloading and deformation control

[0070] The hanging basket was subjected to graded loading at 1.2 times the design load (the design load corresponds to the maximum weight of a single concrete section of 209.6t, so the preload is 251.5t). The loading levels were 20% → 50% → 80% → 100% → 120%, with each level held for 30 minutes. The elastoplastic deformation data of the structure was collected in real time through a distributed sensor network (including wire encoders and strain gauges).

[0071] Monitoring results show that the extreme value of the bottom basket deflection is 14.2 mm, and the elastic deformation recovery rate of the main truss is >98%. The pre-camber of the formwork is corrected based on a BP neural network algorithm, using a calculation model of "measured elastic deformation value + 1.1 times the inelastic deformation reserve value". Construction verification shows that the bridge alignment error is L / 3200 (L=4m, i.e., error ≤1.25mm), which is less than the specified L / 3000 (≤1.33mm), meeting the alignment control requirements.

[0072] S3, Intelligent Control and Synchronous Walking

[0073] The core configuration of the integrated mechanical-hydraulic-electrical intelligent control system is as follows:

[0074] Drive unit: Dual-cylinder rack and pinion drive, equipped with a proportional directional valve and laser ranging module (accuracy ±1mm), which stably controls the basket's walking speed at 0.5m / min; adopts PID flow closed-loop algorithm, and the measured multi-cylinder synchronization error is ±2.8mm;

[0075] The sensor network consists of 32 strain gauges (range ±5000με), 16 wire encoders (resolution 0.1mm), several tilt sensors (range ±15°), and an environmental monitoring unit (including wind speed and temperature sensors), with a sampling frequency of 100Hz. Based on edge computing technology, the system can issue an early warning within 0.8 milliseconds when the load eccentricity reaches 8.5%. At the same time, it establishes a database of 12 types of fault codes, including hydraulic pressure surge (threshold ±15%), abnormal oil temperature (>65℃), and communication interruption, triggering a three-level alarm mechanism of "early warning / limited operation / emergency stop".

[0076] Digital twin platform: A high-precision 3D model of the hanging basket-beam structure is constructed using BIM+GIS fusion technology. Relying on a 5G network (latency <20ms), the platform transmits the 3D attitude, load distribution, and environmental data of the hanging basket in real time. The platform displays in real time that the maximum stress of the hanging basket is 210MPa, the maximum displacement deformation is L / 550 (L=4m, i.e. ≤7.27mm<L / 500=8mm), and the overturning safety factor is 2.3. All indicators meet the design requirements.

[0077] S4. Segmental Cyclic Construction and Environmental Adaptation

[0078] Under the full control of the intelligent system, the segmental cyclical operation of "rebar tying → concrete pouring (C55 prestressed concrete) → prestressing tensioning → curing → formwork forward movement" is completed (a total of 24 standard segments, each segment beam length 4m):

[0079] Safety protection: The hanging basket is equipped with a disc spring-hydraulic composite drive hydraulic rail clamp, with a measured locking force of 520kN; when the environmental monitoring unit detects that the wind speed reaches 15m / s, the intelligent system controls the rail clamp to achieve emergency braking within 0.25 seconds to prevent the hanging basket from shifting due to strong winds.

[0080] Dynamic control: Before construction, parameter benchmarks are obtained through multi-condition finite element simulation (including pouring, walking, and eccentric load conditions). During construction, parameters such as concrete pouring rate and formwork forward movement step length are dynamically adjusted in combination with real-time data from the sensor network to ensure continuous and smooth operation of 24 segments.

[0081] S5, Simulation Verification and Security Control

[0082] Before construction, a coupled finite element model of the hanging basket and beam was established using ANSYS software, and simulation verification was performed on the following key working conditions:

[0083] Maximum pouring condition: Simulate the structural stress under the maximum concrete load (209.6t) of a single segment;

[0084] Uneven loading condition: Simulates the structural stability when concrete pouring is asymmetrical (uneven loading coefficient 1.2);

[0085] Working condition of 10 - level gale: Simulate the wind resistance performance under extreme wind loads (conventional 8 - 9 - level winds in the super - bridge area).

[0086] Traveling working condition: Simulate the dynamic stress when the hanging basket moves forward (speed 0.5 m / min).

[0087] Anti - overturning working condition: Simulate the anti - overturning ability under the risk of failure of the hanging basket anchoring system.

[0088] The simulation results show that the structural safety factors under each working condition are all greater than 1.2 times of the specification limit. Among them, the simulated value of the anti - overturning safety factor is 2.4 (consistent with the actual monitored value of 2.3), verifying the safety and feasibility of the construction plan.

[0089] Simulation verification

[0090] Before construction, a coupled model of the hanging basket - beam body was established by MidasCivil, and simulation verification was carried out for 7 typical working conditions (covering states such as pouring, wind load, and traveling), including Working Condition 1 (calculation of the strength and stability of the main truss load - bearing system of the hanging basket), Working Condition 2 (off - loading situation during the concrete pouring process of the hanging basket), Working Condition 3 (windy situation after the concrete pouring of the hanging basket), Working Condition 4 (traveling working condition of the hanging basket), Working Condition 5 (structural stiffness of the hanging basket system during the pouring state), Working Condition 6 (anti - overturning ability during concrete pouring), and Working Condition 7 (anti - overturning ability when the hanging basket is traveling). The results show that the maximum stress of the main truss is 149.9 MPa < 215 MPa, the maximum displacement of the bottom support system is 16.7 mm < L / 500 = 20 mm, the anti - overturning value of Working Condition 6 is 6.4, the anti - overturning value of Working Condition 7 is 11.6, and the structural safety factors under each working condition are all more than 1.3 times of the specification limit, meeting the construction safety requirements.

[0091] Engineering application effectiveness

[0092] During the construction of 24 segments of the Wushui River Special Bridge in Luoye Bay, the intelligent control system reduced the single - time travel time and shortened the segment construction cycle by 23%; the template positioning error ≤ ±2.5 mm (the specification allows ±5 mm), and the qualified rate of the concrete joint flatness is 100%; there were 16 cumulative early warnings (including 7 times of wind load over - limit and 5 times of hydraulic leakage), achieving zero - accident construction, and the comprehensive cost was reduced by 12%.

[0093] To sum up, the cantilever - casting beam hanging - basket construction method for high - pier long - span special bridges described in this invention effectively solves the problems existing in traditional construction methods through lightweight wind - resistant design, high - precision assembly, intelligent collaborative control, precise pre - pressing deformation regulation, and environment - adaptive cyclic construction, significantly improving the construction quality, safety, and efficiency. It has been successfully applied in the project of the Wushui River Special Bridge in Luoye Bay and has wide popularization and application value.

[0094] The specific structural calculation of the hanging - basket construction is as follows:

[0095] Calculation parameters

[0096] (1) Load values

[0097] Concrete load: The load value is taken as 26 kN / m 3 The heaviest segment of the main beam weighs 21,000 kN, and the side formwork weighs 1.5 kN / m. 2 Bottom mold 1kN / m 2 The inner mold has a strength of 0.85 kN / m. 2 The load on construction machinery and personnel is taken as 2.5 kN / m. 2 The design wind speed is taken as v = 25 m / s.

[0098] (2) Structural Model

[0099] The simulation calculation uses the same cross-sectional dimensions and material specifications as the design for overall modeling (e.g., Figure 6 As shown in the figure, assuming that the rhomboid hanging basket component is an elastic material, when simulating the working condition of the rhomboid hanging basket, only elastic deformation is considered. The truss members and the slings are simulated using truss rod elements, and the remaining components are simulated using beam elements.

[0100] (3) Boundary conditions

[0101] In the MidasCivil finite element software, the hanging basket anchorage is set as a general support, and movement in different directions is constrained according to the actual situation. At the contact position between the bottom rail and the bottom formwork, the software uses an elastic connection simulation. At the connection position between the main truss members, it is necessary to release the beam end constraints to simulate the actual hinge and other situations.

[0102] Calculation of operating conditions

[0103] The calculations cover seven working conditions, including pouring, wind load, and travel (see Table 1).

[0104] Table 1 Summary of Calculation Conditions

[0105]

[0106] Working condition 1: Used to calculate the strength and stability of the main truss load-bearing system of the hanging basket;

[0107] Working condition 2: Used to calculate the most unfavorable load condition during the concrete pouring process of the hanging basket, simulating the eccentric loading situation;

[0108] Working condition 3: Used to calculate the situation of strong winds after the concrete pouring of the hanging basket is completed;

[0109] Working condition 4: Used to calculate the traveling conditions of the hanging basket;

[0110] Working condition 5: Used to calculate the structural stiffness of the hanging basket system during the pouring process;

[0111] Condition 6: Used to calculate the anti-overturning capacity during concrete pouring.

[0112] Condition 7: Used to calculate the anti-overturning capacity during the walking of the hanging basket.

[0113] Calculation results

[0114] The finite element mechanical model of the hanging basket is as Figure 7 shown. Through the simulation calculation of MidasCivil finite element software (see Figure 8 )]]), the calculation results show that: the extreme stress of the bottom support system appears in Condition 1, the extreme stress of the guide beam system appears in Condition 2, the extreme stress of the front cross beam appears in Condition 2, the extreme stress of the main frame appears in Condition 2, σ max = 149.9 MPa < [σ] = 215 MPa; the extreme displacement of the diamond-shaped hanging basket appears in the bottom support system ε max = 16.7 mm < L / 500 = 2 mm. The strength and stiffness of the hanging basket fully meet the requirements of the specification (GB50017-2017 Code for Design of Steel Structures). The calculation results are shown in Table 2.

[0115] Table 2 Summary of mechanical calculation results of finite element software

[0116]

[0117] Using MidasCivil finite element software for anti-overturning calculation of the hanging basket, the anti-overturning value of the calculation result in Condition 6 is 6.4, and the anti-overturning value of the calculation result in Condition 7 is 11.6, both higher than the specification value of 2. The anti-overturning capacity of the overall structure of this hanging basket meets the requirements of the specification (GB50017-2017 Code for Design of Steel Structures).

[0118] Mechanism and calculation of wind load

[0119] (1) Design wind speed: The basic wind speed with a 50-year return period in the bridge location area is 25 m / s (Grade 8-9), the gust factor is 1.45, and the corresponding wind pressure W = 0.5×1.25×25² = 390.6 Pa;

[0120] (2) Wind vibration response: The first natural frequency of the hanging basket structure is 2.1 Hz (calculated value). The matching analysis with the wind vortex shedding frequency (f = St·v / D, St = 0.2, D = 4.2 m) shows no resonance risk;

[0121] Aerodynamic shape optimization

[0122] (1) Deflector plate installation: An arc-shaped deflector plate is added to the outside of the rhomboid truss to reduce the vortex shedding energy by 30%. According to the Strouhal number formula (St=fD / v) (where (f) is the vortex shedding frequency, (D) is the characteristic dimension, and (v) is the wind speed), when the lateral dimension of the hanging basket truss (D=4.2) and the design wind speed (v=25), the theoretical vortex shedding frequency (f=1.19) is obtained. By adding an arc-shaped deflector plate (curvature radius 1.2m), the periodicity of airflow separation is disrupted, so that the actual vortex shedding frequency (f'=0.83) avoids the structural fundamental frequency (2.1), thereby reducing the wind vibration energy by 30%.

[0123] (2) Drag Reduction through Hollowing: The template opening ratio is 15%, reducing the windward area by 12%. Based on the Darcy-Weisbach formula (P=f(L / D)(v^2 / 2)), the template opening ratio of 15% can reduce the friction factor (f), thus reducing the equivalent windward area by 12%. The honeycomb opening (80mm diameter) forms a local turbulent boundary layer, reducing the surface wind pressure gradient, and the measured wind pressure coefficient drops from 1.2 to 0.98.

[0124] Structural wind resistance reinforcement

[0125] (1) Lateral connection system: X-shaped horizontal bracing is added at a spacing of 4m to increase lateral stiffness by 18%;

[0126] (2) Rear anchor redundancy design: double-row precision rolled threaded steel, pre-tightening force increased to 800kN, and overturning moment increased by 25%.

[0127] Dynamic damping control

[0128] (1) Tuned mass damper: A mass block is installed at the front end of the hanging basket, the damping ratio is increased from 0.02 to 0.08, and the displacement response is reduced by 40%;

[0129] (2) Limiting device: The traveling track is equipped with a hydraulic rail clamp, which automatically locks when the wind speed is >15m / s to prevent slippage.

[0130] High-precision assembly process

[0131] Given the large weight (209.6t) and large number (24 segments) of the main beam segments, custom manufacturing by specialized manufacturers was selected to ensure that the dimensional error of the rhomboid hanging basket components is ≤2mm. The assembly process strictly follows the sequence of "track layout → track installation → truss assembly → anchoring system → suspension system → base support system," and the precision control standards for key links are as follows:

[0132] (1) Track positioning: centerline deviation ≤3mm, levelness ≤1‰;

[0133] (2) Truss assembly: node misalignment ≤2mm, bolt torque error ±5%;

[0134] (3) Sling installation: verticality deviation ≤1°, preload error ≤3%.

[0135] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made under the concept of the present invention using the description and drawings of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for constructing a cantilever beam using a formwork system for a high-pier, long-span, extra-large bridge, characterized in that... Includes the following steps: S1. Construction preparation and hanging basket system construction: Install hanging basket tracks on both sides of the bridge pier and control the installation accuracy; assemble the hanging basket in the order of main truss, anchoring system, suspension system and bottom support system. The main truss is optimized for stress to reduce its self-weight. The suspension system uses manganese steel plate slings; set arc-shaped guide plates on the outside of the main truss. The template inside the hanging basket adopts a honeycomb hollow structure. S2. Preloading and Deformation Control of Hanging Formwork: The hanging formwork is subjected to graded loading with 1.2 times the design load, and the elastic-plastic deformation data of the structure is collected. The precamber of the formwork is corrected and the elastic-plastic deformation reserve is considered to ensure that the alignment error of the completed bridge meets the requirements. S3. Intelligent Control and Synchronous Movement: Deploy an integrated mechanical-hydraulic-electrical intelligent control system, including a drive unit, a distributed sensor network, and a digital twin platform; the drive unit controls the walking speed of the hanging basket and ensures synchronization error of multiple cylinders; the distributed sensor network integrates a monitoring unit to achieve rapid alarm response when the load is abnormal; the digital twin platform constructs a three-dimensional model to monitor the stress, displacement, and overturning safety factor of the hanging basket in real time. S4. Segmental Cyclic Construction and Environmental Adaptation: Under the control of an intelligent system, segmental cyclic operations such as rebar binding, concrete pouring, prestressing tensioning, and forward movement of the hanging basket are completed; the ambient wind speed is monitored in real time by a wind speed sensor, and the hydraulic rail clamps automatically lock when the wind speed reaches the threshold; construction parameters are dynamically adjusted in combination with pre-operation data. S5. Simulation Verification and Safety Control: Before construction, a model is established to conduct simulation verification for the maximum pouring condition, eccentric load condition, strong wind condition, walking condition, and anti-overturning condition, to ensure that the structural safety factor meets the specification limit requirements under each condition.

2. The construction method according to claim 1, characterized in that, The main load-bearing structure of the hanging basket in step S1 is configured as follows: the main load-bearing members of the rhomboid truss of the main truss are composed of double channel steel welded together to form a composite section, and the centroid of the topology-optimized section coincides with the load-bearing axis; the front upper crossbeam of the rhomboid truss is made of double steel arranged side by side; the outer and inner sliding beams of the track are both made of double channel steel composite sections and are slidably connected to the main truss; the middle portal chord on the rhomboid truss is made of channel steel, forming a stable spatial triangular support system.

3. The construction method according to claim 1, characterized in that, The high-precision installation method of the track in step S1 is as follows: a high-precision laser level is used to scan and monitor the elevation of the top surface of the track throughout the entire process. Wedge-shaped adjustment blocks are inserted between the track base plate and the embedded parts of the beam for fine adjustment to control the longitudinal slope accuracy of the top surface of the track. All high-strength bolt connection nodes are tightened with hydraulic torque wrenches with preset torque values. A torque detector is used for spot checks and verification to control torque construction errors.

4. The construction method according to claim 1, characterized in that, The implementation method of graded preloading in step S2 is as follows: a set of synchronously controlled hydraulic jacks apply loads simultaneously to the front lifting point and rear anchor point of the hanging basket, and the load value is controlled by real-time feedback from a precision pressure sensor; during the loading process, the deflection of the bottom basket is monitored by a displacement sensor arranged in the middle of the bottom longitudinal beam, and the extreme value of the bottom basket deflection is controlled; after unloading, the elastic deformation recovery rate of the main truss structure is calculated by comparing the displacement data of the key nodes of the main truss before and after loading.

5. The construction method according to claim 1, characterized in that, The distributed sensor network described in step S3 is configured as follows: strain gauges are arranged at key stress nodes of the main truss of the hanging basket, the front and rear suspension belts, and the longitudinal beams of the bottom basket to measure multidimensional stress states; wire encoders are installed to measure the forward movement of the hanging basket and the vertical displacement of the template; dual-axis tilt sensors are arranged at the front and rear ends and the middle of the hanging basket to monitor the overall attitude of the hanging basket; all sensors collect data synchronously, and the intelligent control system is pre-set with fault logic including sudden changes in hydraulic pressure, abnormal oil temperature, and communication interruption, and can trigger a three-level progressive alarm response of early warning, movement restriction, and emergency stop.

6. The construction method according to claim 1, characterized in that, The wind control linkage mechanism of the hydraulic rail clamp in step S4 is as follows: when the wind speed sensor in the environmental monitoring unit detects that the wind speed reaches the preset threshold of 15m / s for 3 consecutive seconds, the intelligent control system immediately sends an electrical signal to the hydraulic rail clamp; the hydraulic rail clamp uses a composite drive method of providing constant braking force with disc springs and releasing pressure by hydraulic cylinders overcoming spring force; wherein, the disc springs provide a clamping force of more than 500kN and complete rigid locking within 0.3 seconds.

7. The construction method according to claim 1, characterized in that, The specific content and qualification standards of the simulation verification in step S5 are as follows: establish a coupled finite element model of the hanging basket-beam body containing construction details, and calculate and analyze typical working conditions such as maximum pouring, strong wind, walking and anti-overturning; the simulation results require that the maximum combined stress of the main truss and the maximum vertical displacement of the bottom support system be controlled, and the anti-overturning stability safety factor meet the requirements under all working conditions.

8. The construction method according to claim 1, characterized in that, During construction, the remote transmission and interaction of the data are achieved through 5G communication technology: the distributed sensor data and control commands deployed on the hanging basket are transmitted in real time in both directions and stably; the digital twin platform is remotely accessed to view the relevant status data and environmental data of the hanging basket in real time.

9. The construction method according to claim 1, characterized in that, The intelligent control system is equipped with an automatic safety control mechanism, which is triggered when the distributed sensor network detects that the load eccentricity exceeds the safety threshold. After triggering, the intelligent control system first automatically suspends all travel and concrete pouring operations of the hanging basket, then calls the real-time data of the digital twin platform to perform differential compensation adjustment on the tension of the front and rear slings, and simultaneously increases the hydraulic clamping force of the track anchor points, forming a dynamic adjustment closed loop of multi-actuator linkage. Construction can only be confirmed to resume after the intelligent control system verifies and confirms that the load eccentricity has returned to within the safe range.

10. The construction method according to claim 1, characterized in that, After each standard segment construction cycle is completed, a machine vision-based alignment monitoring auxiliary process is introduced: a high-precision total station and a laser rangefinder are used to jointly measure the elevation control points and axis deviation of the poured beam segments. The collected measured data is uploaded to the digital twin platform in real time, compared and analyzed with the alignment value predicted by the pre-camber correction model, and the pre-camber setting parameters of the next segment are dynamically iterated and optimized based on the deviation results to ensure that the cumulative alignment error of the completed bridge meets the requirements after the entire bridge is closed.

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