Cast-in-place box girder integral moving type steel formwork span-by-span pouring construction method

Abstract

The invention belongs to the technical field of bridge construction, and discloses a cast-in-place box girder integral moving type steel formwork span-by-span pouring construction method. Comprising the following steps that S1, a construction site is treated, and a supporting system is built; s2, assembling a template system; s3, integrating and debugging a driving system; s4, controlling the movement of the template; s5, elevation rechecking and concrete pouring are conducted; s6, circulating construction is conducted; and S7, the whole support is dismantled. According to the device, the driving system is installed on the steel formwork, each side comprises the hydraulic system, each hydraulic system unit comprises the jacking oil cylinder and the transverse moving oil cylinder, lifting and transverse moving of the steel formwork before and after integral construction of the simply-supported box girder steel formwork are ensured, the steel formwork of each unit and a bottom formwork are stably, tightly and reliably connected into a whole, and the construction efficiency is improved. And the integrity of concrete construction is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge construction and discloses a span-by-span casting construction method of an integral movable steel formwork for a cast-in-place box girder. Background Art

[0002] In the current cast-in-place construction of simply supported box girders for railways, traditional block-type steel formworks use ordinary steel plates as formwork materials, which are prone to rust and have prominent problems with misaligned joints, resulting in frequent quality defects such as honeycombed surface of the concrete, requiring frequent grinding and maintenance, insufficient turnover of the formwork, and high construction costs. The formwork drive system mostly uses manual or simple hydraulic control, with poor synchronization accuracy and large elevation deviation after the formwork is shifted, making it difficult to meet high-precision linear requirements. In addition, the risk level of the construction operation of hoisting the steel formwork of the simply supported box girder in sections by span is high, the overall movement of the formwork is inconvenient, the appearance quality of the solid concrete is poor, the linear control is inaccurate, and the elevation positioning is difficult to control.

[0003] Chinese patent 202211352743.6 discloses a cast-in-place box girder mobile formwork complete set of construction equipment and method thereof, the complete set of construction equipment includes a cast-in-place box girder, a mobile formwork, a mobile formwork bracket, a pier, a gantry crane, an electric hoist, a wire rope, a walking track, and a steel integral skeleton and a hoist construction device. When the steel integral skeleton is cast into a concrete box girder, the bottom plate steel bars and web steel bars can be tied on the cast-in-place box girder at the same time, and the prestressed steel bundles can be arranged and the steel skeleton of the inner mold can be assembled. The process is convenient for continuing to quickly transport the prepared steel integral skeleton to the outer template of the mobile formwork when the mobile formwork passes through the hole, thereby realizing synchronous operation, and the construction period of each hole can be shortened by about 5 days. Compared with the traditional construction process, no gantry crane is required, so it meets the requirements of large span, large tonnage and high clearance, and solves the problem that the traditional gantry crane cannot meet the construction requirements when the pier is too high. At the same time, it is also applicable to situations where the gantry crane walking track cannot be set under the bridge deck such as offshore construction. Although the above invention improves the construction efficiency through the gantry crane and synchronous operation, it does not solve the problem of poor concrete quality caused by the formwork material, and it is difficult to achieve the overall movement of the steel formwork, resulting in low overall construction efficiency. Summary of the invention

[0004] The invention aims to solve the problem in the prior art that it is difficult to realize the overall movement of the template, resulting in low overall construction efficiency and excessively high consumption costs.

[0005] The technical solutions adopted in the present invention are: A cast-in-place box girder integral movable steel formwork span-by-span casting construction method comprises the following steps: S1. Construction site preparation and support system construction: clear obstacles in the construction area and level the foundation, use flange bolts to splice steel columns in sections, and install brackets; S2. Formwork system assembly: laying a bottom form on the bracket, fixing prefabricated tracks along both sides of the bottom form, splicing multiple steel formwork units into an integral movable formwork, wherein the outer surface of the steel formwork unit is a stainless steel composite panel structure; S3. Drive system integration and debugging: The motor drive system is symmetrically installed on both sides of the steel formwork, each side includes at least 6 sets of hydraulic units, each set of hydraulic units is equipped with at least 4 jacking cylinders and at least 3 lateral cylinders, and the motor drive system is synchronously connected to the CNC synchronous controller; S4. Template movement control: Start the motor drive system, move the steel template along the track to the target span through the roller system, and synchronously control the hydraulic unit to adjust the template elevation to the design value, with a lateral positioning error of ≤3mm; S5. Elevation verification and concrete pouring: Use a total station to verify the elevation of the top surface of the template. After confirming that the error is ≤2mm, cast-in-place simple supported box girder concrete construction is carried out; S6. Cyclic construction: After the single-span concrete strength reaches 30MPa, the inner formwork is removed, the outer formwork is retained and steps S4 and S5 are repeated to carry out the next span construction; S7. Overall dismantling of the support: pre-embed the lifting points on the beam of the support, and use the CNC synchronous controller to synchronously adjust the falling rate and displacement of the hydraulic jack to lower the support as a whole.

[0006] By adopting the above technical solution, the template can be quickly and accurately positioned to the target span position by using an integral mobile template system and a CNC synchronous controller. The lateral positioning error in this process is controlled within 3 mm, and the elevation error does not exceed 2 mm, which greatly improves the construction accuracy. In addition, the application of prefabricated track and roller system allows the template to be quickly adjusted and reused, reducing the time cost of disassembling and assembling the template in traditional construction methods, thereby speeding up the construction progress and ensuring the quality consistency of each span of the box girder. The use of stainless steel composite panel structure as the outer surface of the steel template unit not only increases the corrosion resistance and durability of the template, but also improves the rigidity and stability of the entire template system, which helps to prevent deformation or displacement problems that may occur during the pouring process. At the same time, the jacking cylinder and transverse cylinder configured by the hydraulic unit can effectively adjust the elevation and flatness of the template to ensure the safety and stability of the construction process. In addition, the embedded hanging points of the bracket and the application of CNC synchronous controllers have achieved precise control of the overall falling process of the bracket, further ensuring the safety of the operators. The design of segmented steel columns and reusable steel formwork units has reduced material waste. Since the formwork can be moved as a whole, there is no need to rebuild and dismantle it every time, which significantly reduces labor and time costs. In addition, by recycling the external formwork, a large amount of formwork materials is saved and the impact of construction on the environment is reduced. Overall, this method not only improves resource utilization, but also reduces the overall project cost, with good economic and social benefits.

[0007] Furthermore, in step S1, the bracket installation includes the following steps: S11. Sectional hoisting and splicing: Use crane to hoist steel columns in sections. The length of a single section of steel column is ≤6m. Adjacent sections are connected by flange bolts. The overall straightness deviation after splicing is ≤H / 2000, where H is the total height of the column. S12. Re-measurement of support system: Use total station to re-measure the total length of steel columns, with an allowable deviation of ≤L / 5000, where L is the designed span of the beam. Use torque wrench to spot-check flange bolts, with a torque value of ≥400N·m and a discrete rate of ≤10%.

[0008] By adopting the above technical scheme, the maximum length of a single steel column and the connection method of adjacent sections are specified during the segmented hoisting and splicing process, ensuring that the overall straightness deviation of the column is controlled within the standard. This precise control helps to improve the verticality and stability of the entire support system and reduce the safety hazards caused by structural instability. The support system re-measurement is carried out by using a total station for precise measurement, and the torque value of the flange bolt and its discrete rate are strictly specified, which not only ensures the close connection between the components, but also improves the rigidity of the overall structure and enhances the wind and earthquake resistance during the construction process. The segmented hoisting and splicing method can effectively reduce the on-site welding workload and avoid quality problems that may be caused by site conditions. At the same time, it ensures the manufacturing quality and assembly accuracy of the steel column. For the re-measurement of the support system, by checking the total length of the steel column and spot checking the torque value of the flange bolt, it is ensured that all components meet the design requirements, and the effective monitoring of the construction quality is realized, thereby ensuring the construction quality of the final railway simply supported box girder. The segmented hoisting and quick flange connection method make the installation process of the steel column more convenient and efficient, shortening the construction period. This method allows parallel operations, such as preparing for the installation of the next segment while lifting, which greatly improves work efficiency. The allowable deviation standards and flange bolt torque value requirements set during the support system re-test phase provide a clear quality benchmark for subsequent processes, reduce the possibility of rework, and further improve the overall construction progress.

[0009] Furthermore, before the steel formwork units are spliced, the formwork size and span compatibility check is also included. The length, width and diagonal size of each steel formwork unit are measured using a total station, with an allowable deviation of ≤L / 5000, L being the designed span, and the maximum cumulative error of a single formwork ≤10mm. Then, a feeler gauge is used to detect the misalignment height of adjacent formwork joints, with an allowable misalignment height of ≤0.5mm. Finally, the span matching acceptance is carried out before the formwork is moved as a whole, and the deviation value between the total length of the formwork and the designed span is verified by a laser rangefinder to be ≤20mm.

[0010] By adopting the above technical solution, the length, width and diagonal dimensions of each steel formwork unit are accurately measured using a total station, and the allowable deviation is set to ensure the accuracy of the size of a single formwork. This step effectively reduces the installation difficulties or structural instability caused by dimensional errors. The maximum cumulative error of a single template is limited to 10mm, ensuring the consistency and coordination of the overall template system and improving the quality and flatness of the final concrete pouring surface. A feeler gauge is used to detect the misalignment height of adjacent template joints, and the allowable misalignment height is required to be 0.5mm. This strict control helps to avoid concrete leakage caused by uneven template joints, thereby ensuring the density and strength of concrete components. Before the template is moved as a whole, the deviation value between the total length of the template and the designed span is checked by a laser rangefinder to ensure that it is within the marked range, ensuring that the overall layout of the template system meets the design requirements and further enhancing the safety and stability of the structure. Accurate dimensional measurement and strict quality control measures, such as the limitation of dimensional deviation and misalignment height, can not only improve the accuracy of template installation, but also significantly improve the appearance quality of concrete after molding, reduce the workload of repairs, and save costs. During the span matching acceptance process, the application of modern measuring tools such as laser rangefinders can more accurately evaluate the overall layout of the template, timely discover and correct potential problems, and ensure the overall quality of the project.

[0011] Further, in step S2, the installation and fixing of the prefabricated track includes the following steps: S21. Track pre-laying: Two parallel rails are laid symmetrically on both sides of the bottom form of the bracket. The parallelism deviation between the center line of the rail and the axis of the beam body is ≤2mm / m; S22. Use a total station to detect the centerline position of the track. If the deviation exceeds 3mm, adjust the rail laying position. Set anchoring components every 1.5m along the length of the rail and fix the rail to the bracket through embedded steel plates. S23. Use laser marking equipment to detect the straightness of the rail. The straightness deviation over the entire length is ≤5mm. For sections where the local deviation exceeds 3mm, the deviation is corrected by adjusting the thickness of the gasket at the bottom of the rail.

[0012] By adopting the above technical solution, the parallelism deviation between the center line of the rail and the axis of the beam is stipulated to be within 2mm / m during track pre-laying. This strict parallelism control ensures the basic accuracy of track laying and reduces the workload and complexity of subsequent adjustments. The total station detects the position of the center line of the track and sets a position deviation limit of 3mm to ensure the precise arrangement of the center line of the track, which is crucial to ensure the safety and stability of the entire structure. By setting anchor components at intervals of 1.5m along the length of the rail and firmly fixing the rail to the bracket through embedded steel plates, the overall stability and bearing capacity of the track are enhanced, and displacement caused by external forces is prevented. Or deformation, use laser marking equipment to detect the straightness of the rail, and control the straightness deviation within 5mm over the entire length, and correct the deviation in the section where the local deviation exceeds 3mm, to ensure the straightness of the track, thereby improving the safety and efficiency of the machinery and equipment running on it. Accurate track laying and timely adjustment measures help reduce possible problems during track laying, reduce subsequent maintenance costs, and improve the overall construction quality. Although the refined construction method may require more time and technical investment in the early stage, in the long run, it can significantly reduce the number of reworks due to errors, improve work efficiency, and speed up project progress.

[0013] Furthermore, the installation method of the hydraulic unit in step S3 includes: S31. Arrangement of the lifting cylinder group: The lifting cylinder installation positions are set at the bottom of the steel formwork at intervals of 1.5m in the longitudinal direction. Two lifting cylinders are symmetrically arranged at each installation position. The bases of the lifting cylinder and the lateral cylinder are fixed to the bottom of the steel formwork by high-strength bolts. The top ends of the piston rods of the lifting cylinder and the lateral cylinder are in direct contact with the top surface of the bracket and are pressure-bearingly connected; S32. Transverse cylinder group connection: Transverse cylinder mounting brackets are set at 2m intervals on the side of the steel formwork, and a transverse cylinder is installed on the mounting bracket. The cylinder body of the transverse cylinder is hinged to the mounting bracket, and the end of the piston rod of the transverse cylinder is connected to the track through a universal joint; S33. Hydraulic control integration: The lifting cylinder and the traverse cylinder are connected to an external hydraulic pump station through hydraulic pipelines. A proportional reversing valve is provided at the outlet of the external hydraulic pump station and is communicated with the CNC synchronous controller; S34. Synchronous control configuration: The lifting cylinder and the lateral moving cylinder are both equipped with displacement sensors. The CNC synchronous controller dynamically adjusts the actions of the lifting cylinder and the lateral moving cylinder according to the feedback signal of the displacement sensor to control the lifting speed of the steel formwork to ≤10mm / s and the lateral moving speed to ≤5mm / s. Under the action of the deadweight of the steel formwork and the concrete load, the synchronous displacement error of the lifting cylinder and the lateral moving cylinder is ≤2mm.

[0014] By adopting the above technical scheme, through the arrangement of the lifting cylinder group and the connection of the transverse cylinder group, two lifting cylinders are symmetrically arranged at each lifting cylinder installation position, and transverse cylinder installation brackets are set at a lateral interval of 2m on the side of the steel formwork to ensure uniform distribution and precise transmission of force. The cylinder base is fixed with high-strength bolts and the top of the piston rod is in direct contact with the top surface of the bracket and pressure-bearing connection. This increases the stability and reliability of the system and helps to improve the construction accuracy of the overall structure. The cylinder body of the transverse cylinder is hinged to the installation bracket, and the end of its piston rod is connected to the track through a universal joint, so that the transverse cylinder can flexibly adjust the angle according to actual needs to adapt to construction requirements under different working conditions, improve the adaptability of the equipment, and effectively reduce deviations caused by external factors to ensure construction quality. The hydraulic control integration realizes precise control of the external hydraulic pump station through the communication connection between the proportional reversing valve and the CNC synchronous controller, thereby improving the response speed and control accuracy of the entire hydraulic system. Under the action of the deadweight of the steel formwork and the concrete load, the action of the lifting cylinder and the lateral movement cylinder is dynamically adjusted by the feedback signal of the displacement sensor in the synchronous control configuration, which can effectively control the lifting speed and lateral movement speed of the steel formwork to ensure the safety and stability of the operation.

[0015] Further, S41. Track calibration: use a total station to detect the straightness of the track. When the deviation of the track centerline exceeds 3 mm, adjust the track anchor bolts to correct the deviation; S42. Synchronous movement control: Start the motor drive system and control the roller system to move the steel template along the track at a speed of ≤0.5m / min. At the same time, adjust the hydraulic unit through the CNC synchronous controller to make the vertical elevation error of the template ≤1mm and the lateral positioning error ≤3mm; S43. Positioning error verification: After the steel template is moved to the target span, use a laser rangefinder to measure the lateral deviation between the template side and the track baseline. When the deviation is greater than 3mm, trigger the transverse cylinder to make fine adjustments until it meets the standard.

[0016] By adopting the above technical solution, the total station is used to detect the straightness of the track, and the deviation of the center line of the track can be accurately measured. When the deviation exceeds 3mm, the track anchor bolts are adjusted in time to correct the deviation, ensuring the straightness and installation accuracy of the track. High-precision track calibration measures help reduce the cumulative errors that may occur in the subsequent construction process, ensuring the stability and accuracy of the steel template moving on the track. The motor drive system is started to control the roller system to move the steel template along the track at a speed not exceeding 0.5m / min. This low-speed and stable movement method can effectively reduce the vibration and impact caused by excessive speed, thereby improving the control accuracy during the movement. The hydraulic unit is adjusted by the CNC synchronous controller to make the vertical elevation error of the template within the standard and the lateral positioning error within 3mm, achieving highly accurate control of the position of the steel template and ensuring the dimensional accuracy of the final structure. The laser rangefinder is used to measure the lateral deviation of the template side and the track reference line. After the steel template moves to the target span, its positioning error can be quickly and accurately determined. Once the deviation is found to be too large, the transverse cylinder is immediately triggered to make fine adjustments until it reaches the standard, ensuring accurate positioning.

[0017] Furthermore, in step S6, a rebound tester is used to detect the compressive strength of single-span concrete. When the strength is ≥30 MPa, the inner steel formwork is removed, and the outer formwork is retained when the inner formwork is removed. A release agent is applied to the contact surface between the outer formwork and the concrete, and a temporary supporting steel pipe with a spacing of ≤1.5m is used to fix the position of the outer formwork. The surface quality after removal is checked, and steps S4-S5 are repeated to carry out the construction of the next span. After completing the construction of three spans, the track straightness of the integral movable formwork and the synchronization error of the hydraulic system are systematically retested.

[0018] By adopting the above technical solution, a rebound hammer is used to test the compressive strength of single-span concrete (≥30MPa). This is a non-destructive testing method that can accurately evaluate the strength of concrete without damaging the structure. Subsequent processes are only carried out when the strength reaches the design requirements, thereby ensuring the safety and reliability of the structure. The outer mold is retained when the inner mold is removed. This practice is not only conducive to maintaining the quality of the concrete surface and reducing the risk of cracks or deformation caused by premature removal of the outer mold, but also provides good support conditions for subsequent construction. The contact surface between the outer mold and the concrete is coated with a release agent, which helps prevent concrete from adhering to the outer mold, making the demolding process smoother and reducing damage to the concrete surface. The outer mold position is fixed by temporary support steel pipes with a spacing of 1.5m. This method can effectively increase the stability of the outer mold, avoid displacement or deformation of the outer mold due to external forces, and ensure the dimensional accuracy and appearance quality of the concrete after molding. Check the surface quality of the bracket after removal. This step is crucial to timely discover and solve possible problems and ensure the overall aesthetics and safety of the final structure.

[0019] Furthermore, in step S7, four hydraulic jacks are connected to the CNC synchronous controller through hydraulic pipelines, the top of the hydraulic jack is rigidly connected to the embedded lifting point of the bracket, and the CNC synchronous controller is integrated with a CNC display screen to display the falling speed and displacement of each jack, the pressure value, oil temperature and displacement deviation of the hydraulic jack during operation in real time, and transmit them to the host through the CAN bus. According to the real-time feedback of the bracket falling data by the displacement sensor, the CNC synchronous controller dynamically adjusts the jack lowering rate to keep the multi-lifting point displacement synchronization error ≤5mm. When the synchronization error is greater than 5mm, the CNC synchronous controller executes shutdown self-locking and starts the deviation compensation program to adjust the hydraulic valve opening until the error recovers to ≤5mm.

[0020] By adopting the above technical solution, the key parameters such as the falling speed, displacement, working pressure value, oil temperature of each jack are displayed in real time through the integrated CNC display screen, and the jack lowering rate is dynamically adjusted according to the data fed back by the displacement sensor, ensuring the safety and stability of the operation process. When the synchronization error is detected to exceed the set threshold (>5mm), the CNC synchronous controller can automatically execute the shutdown self-locking and start the deviation compensation program, effectively avoiding the safety hazards caused by excessive errors. Multi-point displacement synchronous control: The CNC synchronous controller is used to accurately control multiple hanging points, so that the displacement synchronization error is kept within the range of ≤5mm, which greatly improves the positioning accuracy during the bracket lowering process, which is conducive to ensuring the overall installation quality of the structure. The displacement sensor is used to monitor the bracket's falling data in real time, providing an accurate information basis for the control system, thereby realizing the precise regulation of each hydraulic jack action. The CNC synchronous controller can automatically adjust the hydraulic valve opening according to the actual falling situation, quickly correct possible displacement deviations, reduce the need for manual intervention, and speed up the construction progress.

[0021] The present invention has the following beneficial effects: 1. The present invention realizes the rapid positioning and precise adjustment of the template by introducing the overall movable template system and CNC synchronous control technology. Compared with the traditional segmented hoisting method, this method greatly reduces the risk of high-altitude operations and avoids the potential safety hazards caused by frequent disassembly and assembly of the template. The overall movable template can be moved to the target position smoothly and quickly on the track, which not only shortens the construction period but also improves the construction efficiency. This method significantly improves the operational safety and stability during the construction process, so that the entire project can be carried out efficiently in a more controllable environment; 2. The present invention adopts stainless steel composite panels as the outer surface material of the steel formwork unit, which solves the problem that the traditional steel formwork is easy to rust and the joints are easy to misalign. It not only enhances the corrosion resistance of the formwork and prolongs its service life, but also ensures the flatness and density of the formwork during the concrete pouring process. The use of stainless steel composite panels can also effectively prevent concrete surface defects caused by deformation or displacement of the formwork, thereby improving the overall quality and appearance of the concrete component and reducing the demand and cost for later repairs; 3. The present invention adopts a hydraulic unit closed-loop control system combined with a displacement sensor real-time feedback mechanism, which can accurately adjust the elevation and flatness of the template. During the movement of the template, any slight position deviation can be quickly detected and automatically corrected, ensuring the stability and accuracy of the template throughout the construction process. For large bridge projects, high-precision synchronous control technology can effectively avoid the impact of cumulative errors on the final structural linear accuracy, ensuring that every detail meets the design requirements, and further improving the quality of the project; 4. The present invention advocates standardized template assembly and overall movement technology, so that the template can be reused between different spans without the need to rebuild and dismantle each time. This modular design concept not only simplifies the construction process, but also greatly reduces material waste. The recycling strategy of the external mold further reduces construction costs and reduces pressure on the environment. The application of intelligent control technology simplifies the process of bracket removal and improves work efficiency. These measures work together to significantly reduce the overall cost of the project, and also promote the practice of the concept of sustainable development in the field of engineering construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific preferred embodiments.

[0024] In the description of the present invention, it should be understood that the terms "left side", "right side", "upper part", "lower part" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. "First", "second" and the like do not indicate the importance of the components, and therefore cannot be understood as limiting the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution, and do not limit the scope of protection of the present invention.

[0025] This embodiment provides a method for casting span by span of an integrally movable steel formwork for a cast-in-place box girder. The method can eliminate the high-altitude operation risks of traditional segmented lifting through an integrally movable formwork system and CNC synchronous control, achieve rapid positioning of the formwork, and reduce the construction period.

[0026] like Figure 1 As shown, the following steps are included: S1. Construction site preparation and support system construction: clear obstacles in the construction area and level the foundation, use flange bolts to splice steel columns in sections, and install brackets; S2. Formwork system assembly: laying a bottom form on the bracket, fixing prefabricated tracks along both sides of the bottom form, splicing multiple steel formwork units into an integral movable formwork, wherein the outer surface of the steel formwork unit is a stainless steel composite panel structure; S3. Drive system integration and debugging: The motor drive system is symmetrically installed on both sides of the steel formwork, each side includes at least 6 sets of hydraulic units, each set of hydraulic units is equipped with at least 4 jacking cylinders and at least 3 lateral cylinders, and the motor drive system is synchronously connected to the CNC synchronous controller; S4. Template movement control: Start the motor drive system, move the steel template along the track to the target span through the roller system, and synchronously control the hydraulic unit to adjust the template elevation to the design value, with a lateral positioning error of ≤3mm; S5. Elevation verification and concrete pouring: Use a total station to verify the elevation of the top surface of the template. After confirming that the error is ≤2mm, cast-in-place simple supported box girder concrete construction is carried out; S6. Cyclic construction: After the single-span concrete strength meets the removal conditions, the inner formwork is removed, the outer formwork is retained and steps S4 and S5 are repeated to carry out the next span construction; S7. Overall removal of the bracket: at the pre-embedded lifting points of the beam, the falling rate and displacement of the hydraulic jack are synchronously adjusted by the CNC synchronous controller to lower the bracket as a whole; In step S1: the steel column segmented hoisting and support system retesting process of the present invention is implemented by the following steps: The bracket involved in the present invention may be a beam-column bracket, such as a Bailey beam bracket. The present invention takes a Bailey beam bracket as an example; S11. Segment design and hoisting: The length of a single section of a steel column is limited to 6m. This design is based on the following factors: Transportation restrictions: The length of the conventional flatbed truck is 12m to avoid the risk of over-length and over-width transportation; Lifting safety: Match the safe lifting range of cranes below 50t to ensure lifting stability; Construction efficiency: reduce the amount of high-altitude splicing work and reduce the risk of personnel operation.

[0027] The flange is made of Q355B steel plate with a thickness of 20mm. The outer diameter of the flange is 1.5 times the outer diameter of the steel pipe. For example, a Φ600mm steel pipe is equipped with a Φ900mm flange. Each flange is equipped with 8 M24 high-strength bolts with a preload of 300kN and a corresponding torque of 400N·m; Before lifting, clean the flange contact surface to ensure that there is no rust or impurities, use temporary positioning bolts to fix the steel column segment, preliminarily adjust the verticality through the total station, and tighten the bolts symmetrically three times in diagonal order.

[0028] The straightness controls 1 / 2000 of the total height H of the column. For example, when H=20m, the allowable deviation is 10mm; Use a total station set up on the extension line of the column axis to measure the horizontal offset of the top and bottom center points. Use a laser plumb line to assist in detecting the local curvature. Set up a detection section every 3m in height. When the deviation exceeds the limit, loosen the flange bolts and add stainless steel sheets in the gap. When the local curvature exceeds the tolerance, use a hydraulic jack to push and correct it.

[0029] S12. Re-test of support system: The allowable deviation of the total length of steel columns is 1 / 5000 of the designed beam span L. For example, when L=32m, the allowable deviation is 6.4mm; A high-precision total station is used in conjunction with a prism target to measure the distance between the top and bottom ends of the column. When the total length deviation exceeds the limit, the flange joint gap is checked, and the out-of-tolerance segment is re-cut or replaced. Local errors are compensated by adjusting the thickness of the flange gaskets of the adjacent segments.

[0030] The torque of the flange bolt is controlled at 400N·m, which is suitable for the theoretical preload force of M24 bolts of 400kN. A digital torque wrench is used for loading in stages. One flange is randomly inspected for every 20 flanges, and the number of bolts inspected is 50%. The segmented lifting reduces the amount of high-altitude work, and the flange connection replaces welding. There is no need for post-weld inspection, which improves efficiency by 50%.

[0031] In step S2, two QU80 parallel rails are symmetrically laid on both sides of the bottom mold of the Bailey beam support, and the parallelism deviation between the center line of the rail and the axis of the beam body is strictly controlled at 2mm / m. During laying, the total station is used to monitor the center line position of the track in real time. If the deviation is detected to exceed 3mm, the rail fine-tuning bolts are immediately adjusted to correct the deviation horizontally to ensure that the track axis coincides with the design axis of the Bailey beam support beam body. Anchor components are set at intervals of 1.5m along the length of the rail. Each anchor point uses an embedded steel plate with a size of 200mm×200mm×20mm, which is fixed with M30 high-strength bolts. The bolt torque value is 400N·m. The embedded steel plate is welded to the Bailey beam support to enhance the anti-slip ability. After the track is initially fixed, the laser marking equipment is used to re-measure the straightness of the entire length of the rail, and the straightness deviation within the entire length range is allowed to be 5mm. For sections where the local deviation exceeds 3mm, the rail surface height is adjusted by adding 0.5mm, 1.0mm or 2.0mm thick stainless steel gaskets at the bottom of the rail. The gaskets and the bottom of the rail are bonded and fixed with epoxy resin to prevent displacement. After the deviation correction is completed, the straightness is re-measured until it meets the standard, forming a high-precision track reference line to provide stable support for the subsequent overall movement of the steel template.

[0032] In step S3, jacking cylinder installation positions are set at intervals of 1.5m along the longitudinal direction of the bottom of the steel formwork, that is, along the bridge direction, to ensure that the spacing between the cylinder support points is 1 / 20 of the formwork span when the steel formwork has a dead weight of about 20kN / m² and a concrete load of about 25kN / m². For example, the maximum spacing of a 32m span formwork is 1.6m to avoid excessive local deflection. The spacing of 1.5m is adapted to the node spacing of the bracket to ensure that the cylinder support point is located directly above the Bailey beam node to reduce bracket deformation. Two jacking cylinders are symmetrically arranged at each installation position to form a double-cylinder cooperative pressure-bearing structure to prevent overturning caused by failure of a single cylinder. The jacking cylinder base is 10 .9 grade M24 high-strength bolts with a preload of 300kN are used. The top of the piston rod of the lifting cylinder fixed to the reinforcing rib plate at the bottom of the steel formwork directly abuts against the top surface of the Bailey beam bracket. A 20mm thick Q355B pressure plate is welded on the contact surface to ensure that the local pressure stress is 200MPa. Transversely on the side of the steel formwork, that is, at intervals of 2m in the transverse direction of the bridge, a transverse cylinder mounting bracket is set. The bracket is welded to the side wall of the formwork with H-shaped steel. The bracket spacing is adapted to the lateral stiffness requirements of the steel formwork. The cylinder body of the transverse cylinder and the bracket are hinged with a pin shaft, allowing the cylinder to swing within a range of 5° to adapt to uneven tracks or deformation of the formwork. The end of the piston rod of the transverse cylinder The track side baffle is connected through a cross universal joint to eliminate the angle deviation during lateral movement and avoid jamming. The lifting cylinder and the lateral movement cylinder are connected in parallel to the external hydraulic pump station through a high-pressure hose. A proportional reversing valve is set at the outlet of the external hydraulic pump station to communicate with the CNC synchronous controller through the CAN bus. The external hydraulic pump station adjusts the output pressure in real time according to the load of the lifting cylinder and the lateral movement cylinder to ensure that the lifting force fluctuation does not exceed 5%. The proportional valve adjusts the flow according to the controller instruction. The lifting speed is 10mm / s and the lateral movement speed is 5mm / s to avoid hydraulic shock caused by sudden speed changes. The lifting cylinder and the lateral movement cylinder are equipped with magnetostrictive displacement sensors for real-time Monitor the piston rod displacement of the jacking cylinder and the lateral cylinder. The controller collects displacement signals at a frequency of 100Hz and eliminates noise interference through the Kalman filter algorithm. The controller dynamically adjusts the proportional valve opening according to the displacement difference of 2mm, and uses the PID algorithm to compensate for the action lag of the jacking cylinder and the lateral cylinder. When the synchronization error exceeds 2mm, the shutdown self-locking is triggered and the deviation compensation program is started. The synchronization is restored by adjusting the reversing valve opening of the jacking cylinder or the lateral cylinder that exceeds the tolerance separately. During the concrete pouring stage, the controller combines the cylinder pressure signal and the displacement signal to correct the target displacement value in real time to ensure that the template elevation error does not exceed 1mm; A standardized module is formed by the 1.5m lifting cylinder spacing and the 2m lateral cylinder spacing, which can be adapted to the rapid modification of templates with different spans. The symmetrical arrangement of the double lifting cylinders, the universal joint articulated design and the self-locking mechanism form a three-level safety protection. The proportional valve and sensor use a plug-in interface, which speeds up replacement and reduces downtime losses.

[0033] In step S4, during the track calibration phase, a high-precision total station is used to set measuring points every 2m along the entire length of the track to detect the straightness of the track centerline in real time. If a local deviation is detected exceeding 3mm, the track anchor bolts at the corresponding position are immediately loosened, and the horizontal push track adjustment step is fine-tuned by 0.5mm / time. At the same time, stainless steel wedge-shaped gaskets are used to fill the gap to ensure that the track centerline straightness error does not exceed 3mm. During synchronous movement control, the motor drive system is started to drive the roller system to smoothly move the steel template along the track at a low speed of 0.5m / min. At the same time, the CNC synchronous controller receives the feedback data of the displacement sensor and the inclination sensor in real time, dynamically adjusts the hydraulic unit, controls the lifting cylinder to accurately adjust the vertical elevation of the template at a speed of 10mm / s, and the lateral displacement cylinder corrects the lateral offset at a speed of 5mm / s. After the template is moved to the target span, a laser rangefinder is used to arrange five detection points equidistantly on the side of the template to measure its lateral deviation from the track baseline. If the deviation of any measuring point exceeds 3mm, the transverse cylinder is immediately triggered to perform step-by-step fine-tuning. At the same time, the total station remeasures the coincidence of the template axis and the design axis until the deviation of all measuring points is 2mm, ensuring that the template positioning accuracy meets the requirements for concrete pouring.

[0034] In step S6, after the concrete pouring is completed, the single-span box girder is tested for strength using a rebound tester. Ten test areas are arranged in each test area, and each test area is hit 16 times. The average value is taken to convert the compressive strength. When the concrete strength is 30MPa, the inner steel formwork removal operation is started. During removal, the outer formwork is retained to maintain the stability of the concrete structure. The contact surface between the outer formwork and the concrete is evenly coated with a water-based release agent with a viscosity of 150cP and a coating amount of 200g / m² to avoid concrete adhesion. A temporary support steel pipe with an outer diameter of 48mm and a wall thickness of 3.5mm is used. Support points are set at intervals of 1.5m along the longitudinal direction of the outer formwork. The bottom of the steel pipe is fixed with the embedded steel plate bolts through an adjustable base, and the top is tightened with the outer formwork rib plate through a U-shaped support to ensure that the stiffness of the support system meets the wind load and construction load requirements. After removing the inner formwork, check the surface quality of the Bailey beam, focusing on the detection of honeycomb, pitting and crack defects, honeycomb area ratio, and crack width not exceeding 0.2mm. After the quality reaches the standard, repeat steps S4 and S5 to carry out the construction of the next span; After completing the construction of every three spans, the overall movable formwork is systematically re-measured, and a laser marking instrument is used to detect the straightness of the track. The synchronization error of the hydraulic system is calibrated through a displacement sensor. If the deviation occurs, it is automatically adjusted according to the preset compensation procedure to ensure the consistency of the subsequent construction accuracy.

[0035] In step S7, during the overall dismantling stage of the Bailey beam support, four 200t hydraulic jacks are used and connected in parallel to the CNC synchronous controller through 35MPa high-pressure hoses. The top of the hydraulic jack is rigidly connected to the embedded lifting point through a pin shaft. The embedded lifting point is composed of a 20mm thick Q355B steel plate and an M30 high-strength bolt to ensure a tensile strength of 500kN / point. The CNC synchronous controller integrates a 10.1-inch touch screen to display the falling speed, displacement, working pressure, oil temperature and displacement deviation of each jack in real time. The data is uploaded to the CNC synchronous controller through the CAN bus to realize remote monitoring and data storage. The displacement sensor is installed at the four corners of the Bailey beam to collect the falling displacement data in real time. The CNC synchronous controller dynamically adjusts the opening of the proportional reversing valve to control the lowering rate of the jack to ensure that the synchronous error of the displacement of multiple lifting points is 5mm. When the synchronization error exceeds 5mm, the CNC synchronization controller immediately triggers the shutdown self-locking hydraulic locking valve to operate for no more than 0.5s, and starts the deviation compensation program. First, all jack actions are suspended, and then the reversing valve opening of the over-tolerance lifting point is adjusted separately. At the same time, the laser rangefinder re-measures the horizontal inclination of the Bailey beam until the error is restored to no more than 3mm. After the compensation is completed, the system automatically resumes the synchronous fall, and no manual intervention is required in the whole process, ensuring the safety and millimeter-level accuracy of the bracket removal process.

[0036] Working principle: Through the coordination of the overall mobile formwork system and CNC synchronous control technology, the railway simply supported box girder can be constructed quickly and with high precision span by span. After the site is leveled and obstacles are cleared, the steel columns and Bailey beam brackets are hoisted in sections to form a stable load-bearing structure. The bottom formwork is laid on the Bailey beam and the high-precision track is fixed. The steel formwork unit of the stainless steel composite panel is assembled. The hydraulic drive system of the jacking cylinder and the lateral cylinder is used to realize the overall movement of the formwork. The motor drives the roller system to move the formwork along the track. The CNC synchronous controller receives the data of the displacement sensor and the inclinometer, dynamically adjusts the hydraulic unit, controls the lifting height and lateral movement distance, and self-locks and fine-tunes the recovery when the synchronization error exceeds the limit. After the concrete strength exceeds 30MPa, the outer formwork is retained, and the track and hydraulic system accuracy are re-measured before moving to the next span; every 3 spans are systematically calibrated to ensure the continuity of construction, the embedded lifting points are rigidly connected with the hydraulic jack, the CNC is synchronously lowered, the laser monitors the inclination, and the correction program is triggered when the error exceeds 5mm. It is suitable for complex scenes such as high-speed railways and bridges across rivers, and achieves comprehensive improvement in efficiency, quality and safety.

[0037] The preferred embodiments of the present invention are described in detail above; however, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all belong to the protection scope of the present invention.

Claims

1. A method for casting a cast-in-place box girder with an integral movable steel formwork span by span, characterized in that: The following steps are involved: S1. Construction site preparation and support system construction: clear obstacles in the construction area and level the foundation, use flange bolts to splice steel columns in sections, and install brackets; S2. Formwork system assembly: laying a bottom form on the bracket, fixing prefabricated tracks along both sides of the bottom form, splicing multiple steel formwork units into an integral movable formwork, wherein the outer surface of the steel formwork unit is a stainless steel composite panel structure; S3. Drive system integration and debugging: The motor drive system is symmetrically installed on both sides of the steel formwork, each side includes at least 6 sets of hydraulic units, each set of hydraulic units is equipped with at least 4 jacking cylinders and at least 3 lateral cylinders, and the motor drive system is synchronously connected to the CNC synchronous controller; S4. Template movement control: Start the motor drive system, move the steel template along the track to the target span through the roller system, and synchronously control the hydraulic unit to adjust the template elevation to the design value, with a lateral positioning error of ≤3mm; S5. Elevation verification and concrete pouring: Use a total station to verify the elevation of the top surface of the template. After confirming that the error is ≤2mm, cast-in-place simple supported box girder concrete construction is carried out; S6. Cyclic construction: After the single-span concrete strength meets the removal conditions, the inner formwork is removed, the outer formwork is retained and steps S4 and S5 are repeated to carry out the next span construction; S7. Overall dismantling of the support: pre-embed the lifting points on the beam of the support, and use the CNC synchronous controller to synchronously adjust the falling rate and displacement of the hydraulic jack to lower the support as a whole.

2. The cast-in-place box girder integral movable steel formwork span-by-span casting construction method according to claim 1 is characterized in that: In step S1, the bracket installation includes the following steps: S11. Sectional hoisting and splicing: Use crane to hoist steel columns in sections. The length of a single section of steel column is ≤6m. Adjacent sections are connected by flange bolts. The overall straightness deviation after splicing is ≤H / 2000, where H is the total height of the column. S12. Re-measurement of support system: Use total station to re-measure the total length of steel columns, with an allowable deviation of ≤L / 5000, where L is the designed span of the beam. Use torque wrench to spot-check flange bolts, with a torque value of ≥400N·m and a discrete rate of ≤10%.

3. The cast-in-place box girder integral movable steel formwork span-by-span casting construction method according to claim 2 is characterized in that: Before the steel formwork units are spliced, the template size and span compatibility check is also included. The length, width and diagonal size of each steel formwork unit are measured using a total station. The allowable deviation is ≤L / 5000, L is the design span, and the maximum cumulative error of a single template is ≤10mm. Then, a feeler gauge is used to detect the misalignment height of adjacent template joints. The allowable misalignment height is ≤0.5mm. Finally, the span matching acceptance is carried out before the template is moved as a whole, and the deviation value between the total length of the template and the design span is verified by a laser rangefinder to be ≤20mm.

4. The cast-in-situ box girder integral movable steel formwork span-by-span casting construction method according to claim 1 is characterized in that: In step S2, the prefabricated track installation and fixing includes the following steps: S21. Track pre-laying: Two parallel rails are laid symmetrically on both sides of the bottom form of the bracket. The parallelism deviation between the center line of the rail and the axis of the beam body is ≤2mm / m; S22. Use a total station to detect the centerline position of the track. If the deviation exceeds 3mm, adjust the rail laying position. Set anchoring components every 1.5m along the length of the rail and fix the rail to the bracket through embedded steel plates. S23. Use laser marking equipment to detect the straightness of the rail. The straightness deviation over the entire length is ≤5mm. For sections where the local deviation exceeds 3mm, the deviation is corrected by adjusting the thickness of the gasket at the bottom of the rail.

5. The cast-in-situ box girder integral movable steel formwork span-by-span casting construction method according to claim 1 is characterized in that: The installation method of the hydraulic unit in step S3 includes: S31. Arrangement of the lifting cylinder group: The lifting cylinder installation positions are set at the bottom of the steel formwork at intervals of 1.5m in the longitudinal direction. Two lifting cylinders are symmetrically arranged at each installation position. The bases of the lifting cylinder and the lateral cylinder are fixed to the bottom of the steel formwork by high-strength bolts. The top ends of the piston rods of the lifting cylinder and the lateral cylinder are in direct contact with the top surface of the bracket and are pressure-bearingly connected; S32. Transverse cylinder group connection: Transverse cylinder mounting brackets are set at 2m intervals on the side of the steel formwork, and a transverse cylinder is installed on the mounting bracket. The cylinder body of the transverse cylinder is hinged to the mounting bracket, and the end of the piston rod of the transverse cylinder is connected to the track through a universal joint; S33. Hydraulic control integration: The lifting cylinder and the traverse cylinder are connected to an external hydraulic pump station through hydraulic pipelines. A proportional reversing valve is provided at the outlet of the external hydraulic pump station and is communicated with the CNC synchronous controller; S34. Synchronous control configuration: The lifting cylinder and the lateral moving cylinder are both equipped with displacement sensors. The CNC synchronous controller dynamically adjusts the actions of the lifting cylinder and the lateral moving cylinder according to the feedback signal of the displacement sensor to control the lifting speed of the steel formwork to ≤10mm / s and the lateral moving speed to ≤5mm / s. Under the action of the deadweight of the steel formwork and the concrete load, the synchronous displacement error of the lifting cylinder and the lateral moving cylinder is ≤2mm.

6. The cast-in-situ box girder integral movable steel formwork span-by-span casting construction method according to claim 1 is characterized in that: The step S4 comprises: S41. Track calibration: Use a total station to detect the straightness of the track. When the deviation of the track centerline exceeds 3mm, adjust the track anchor bolts to correct the deviation; S42. Synchronous movement control: Start the motor drive system and control the roller system to move the steel template along the track at a speed of ≤0.5m / min. At the same time, adjust the hydraulic unit through the CNC synchronous controller to make the vertical elevation error of the template ≤1mm and the lateral positioning error ≤3mm; S43. Positioning error verification: After the steel template is moved to the target span, use a laser rangefinder to measure the lateral deviation between the template side and the track baseline. When the deviation is greater than 3mm, trigger the transverse cylinder to make fine adjustments until it meets the standard.

7. The cast-in-situ box girder integral movable steel formwork span-by-span casting construction method according to claim 1, characterized in that: In step S6, a rebound tester is used to test the compressive strength of single-span concrete. When the strength is ≥30 MPa, the inner steel formwork is removed. When the inner formwork is removed, the outer formwork is retained. A release agent is applied to the contact surface between the outer formwork and the concrete. A temporary support steel pipe with a spacing of ≤1.5m is used to fix the position of the outer formwork. The surface quality of the bracket after removal is checked, and steps S4-S5 are repeated to carry out the construction of the next span. After completing the construction of three spans, the track straightness of the integral movable formwork and the synchronization error of the hydraulic system are systematically retested.

8. The cast-in-situ box girder integral movable steel formwork span-by-span casting construction method according to claim 1, characterized in that: In step S7, four hydraulic jacks are connected to the CNC synchronous controller through hydraulic pipelines, the top of the hydraulic jack is rigidly connected to the embedded lifting point of the bracket, and the CNC synchronous controller is integrated with a CNC display screen to display the falling speed and displacement of each jack, the pressure value, oil temperature and displacement deviation of the hydraulic jack during operation in real time, and transmit them to the host through the CAN bus. According to the real-time feedback of the bracket falling data by the displacement sensor, the CNC synchronous controller dynamically adjusts the jack lowering rate to keep the multi-hanging point displacement synchronization error ≤5mm. When the synchronization error is greater than 5mm, the CNC synchronous controller executes shutdown self-locking and starts the deviation compensation program to adjust the hydraulic valve opening until the error recovers to ≤5mm.

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