Synchronous different force jacking method and system for replacing support of large-span steel-concrete composite beam

Abstract

The application relates to the technical field of bridge construction, in particular to a synchronous different force jacking method and system for replacing a support of a large-span steel-concrete composite beam. The method comprises the following steps: a first group of jacks is used to jack up the beam body, the design pressure data of each support point is used as a main control parameter, and the vertical displacement is used as an auxiliary parameter for double control, so that each support point is jacked up to a preset height according to the design counterforce difference, then the old support pad stone is removed, the steel support is installed and replaced, the support counterforce is actually measured, the jacking is locked according to the confirmed final counterforce value, finally, the new support pad stone is poured and the main beam is lowered, and the method further comprises the steps of synchronous different force control, space posture closed-loop control and the like, and a system for executing the method, wherein the system comprises multiple jacking units, a hydraulic power station and a PLC controller. The application can accurately control the jacking process, guarantee the safety of the beam body and realize the technical effect of efficiently and safely replacing the support of the large-span steel-concrete composite beam.

Description

Technical Field

[0001] This application relates to the field of bridge construction technology, and in particular to a synchronous different-force jacking method and system for replacing bearings of large-span steel-concrete composite beams. Background Technology

[0002] Steel-concrete composite beam bridges are widely used in the construction of long-span bridges due to their advantages such as high load-bearing capacity and fast construction speed. Steel bearings, as key force-transfer components between the beam and the pier, need to be replaced after long-term service due to aging, wear, or deformation. In actual engineering projects, it is often necessary to replace all bearings on the same pier cap beam, or even all bearings of the entire bridge, to ensure the integrity and stability of the beam's load-bearing system. Because long-span steel-concrete composite beams have characteristics such as high stiffness, heavy self-weight, and uneven stress distribution at various supports, the jacking operation during this multi-point, integral bearing replacement process presents a significant technical challenge.

[0003] Currently, the replacement of supports for steel-concrete composite beams mostly adopts a synchronous equal-force jacking process. This involves controlling all jacks to lift simultaneously under the same pressure, with the main monitoring during the jacking process being the beam displacement, using uniform displacement as the control target. After the beam is lifted, the old supports are removed, new supports are installed, and the beam is lowered. However, the support reaction force data largely relies on theoretical design values ​​and lacks a practical measurement and calibration process.

[0004] The aforementioned existing technologies have the following problems in practical applications: When replacing multi-point, integral bearings, large-span steel-concrete composite beam structures are generally longer than 45m, with characteristics such as high stiffness, heavy self-weight, and significant differences in design reaction forces at each support point. The synchronous equal-force jacking method cannot adapt to these characteristics. Even a small difference in jacking displacement can generate huge secondary internal forces within the beam, which can easily lead to cracking of the steel-concrete interface or damage to the bridge deck pavement. The jacking process only uses displacement as the control target, and the support reaction force lacks actual measurement and calibration. The design reaction force deviates significantly from the actual force, resulting in an imbalance of forces after the installation of each new bearing, which affects the service life of the bearing.

[0005] For example, in a 60m span steel-concrete composite beam, the design reaction force at the intermediate support is approximately 800kN, while the design reaction force at the edge support is only about 450kN. When using synchronous equal-force jacking, all jacks apply the same pressure, leading to over-jacking of the edge support with the smaller design reaction force, while the intermediate support with the larger design reaction force is under-jacked. The resulting displacement difference between the supports is transformed into a huge secondary internal force in the extremely stiff steel-concrete composite beam. Finite element analysis shows that when the displacement difference between the supports reaches 3mm, the tensile stress at the steel-concrete interface is close to the limit allowable value, posing a serious risk of interface cracking. Furthermore, the inventors discovered that in the existing technology, during the beam lowering stage after support replacement, the actual support reaction force of the new support is controlled solely by the theoretical design value, lacking a practical measurement and calibration process. In actual engineering, due to uneven weight distribution of the beam and construction errors, the deviation between the actual reaction force at each support and the theoretical design value can reach 10%–20%, resulting in uneven stress on the new support after installation and severely affecting its service life.

[0006] Therefore, there is an urgent need for a construction method that can accurately control the stress during the beam lifting process to ensure that the beam structure is not easily damaged and that the stress state after the new support is installed is consistent with the design. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, this application provides a synchronous jacking method and system for replacing supports of large-span steel-concrete composite beams, aiming to solve the technical problems in the prior art that the beam jacking process cannot be precisely controlled, resulting in structural damage, and the stress state of the new support after installation does not match the design.

[0008] This application is achieved through the following technical solution: A method for synchronous jacking under different forces to replace supports of a large-span steel-concrete composite beam includes the following steps: The beam is lifted using the first jack group, which is connected to the PLC controller. During the lifting process, the design pressure data of each support point is used as the independent pressure control target of the corresponding jack. The design pressure data of each support point is used as the main control parameter, and the vertical displacement difference between each point is used as the safety interlock parameter for double closed-loop control. This enables each support point to be lifted synchronously but differently to the preset height according to its own design reaction force. After jacking up, remove the old support pad stones; Install and replace the steel support; After the steel support is replaced and in place, the support reaction force is measured by replacing it with jacks. The measured support reaction force data is reported to the design unit for confirmation. The jacking is then carried out and locked according to the confirmed final reaction force value. The new support pad stones were poured and the main beam was lowered back down.

[0009] By adopting the above technical solution, the replacement of supports for large-span steel-concrete composite beams can be completed accurately, safely, and efficiently. Dual-control jacking, using the design pressure data of each support point as the main control parameter and vertical displacement as the auxiliary parameter, allows each support point to be jacked to a preset height according to the design reaction force, preventing deformation or damage to the beam due to uneven stress and ensuring the structural safety of the beam. Using appropriate methods to remove the old support pads minimizes the impact on the beam and surrounding structures. After installing the replacement steel supports, the support reaction force is measured, and the data is submitted to the design unit for confirmation. The supports are then jacked and locked according to the final reaction force value, ensuring that the stress on the new supports meets design requirements and extending their service life. The new support pads are poured, and the main beam is lowered back down, restoring the beam to its normal service state. The entire process utilizes a PLC controller to achieve precise control of each operation step, improving construction efficiency and quality, reducing construction risks, and ensuring the normal operation and safety of the large-span steel-concrete composite beam.

[0010] Optionally, the dual closed-loop interlock control includes: A pressure sensor and a displacement sensor are independently installed on the jack at each lifting point. The pressure sensor is used to monitor the actual lifting force value at the point in real time, and the displacement sensor is used to monitor the actual lifting displacement at the point in real time. The design pressure data of each fulcrum is input into the PLC controller as the independent control target of each jack; During the lifting process, the PLC controller receives feedback values ​​from each pressure sensor in real time and compares them with the corresponding design pressure data. By independently controlling the oil intake of each jack, the actual lifting force value at each point approaches and stabilizes at the corresponding design pressure data. Meanwhile, the PLC controller receives feedback values ​​from each displacement sensor in real time, calculates the displacement difference between each point, and when the calculated displacement difference exceeds the preset threshold, it suspends the adjustment of the pressure deviation or limits the lifting speed of the point where the displacement difference exceeds the limit until the displacement difference returns to a safe range.

[0011] By adopting the above technical solution, pressure and displacement sensors are independently installed on the jacks at each lifting point, enabling real-time and accurate monitoring of the actual lifting force and displacement at each point. The design pressure data for each support point is input into the PLC control system as an independent control target, allowing the system to receive feedback values ​​from each pressure sensor in real time during the lifting process and compare them with the design pressure data. By independently controlling the oil supply to each jack, the actual lifting force at each point is brought close to and stabilized at the design pressure data, achieving differentiated lifting at each support point according to the design reaction force, ensuring that the beam's stress meets design requirements. Simultaneously, the system receives feedback values ​​from each displacement sensor in real time and calculates the displacement difference between each point. When the displacement difference exceeds a preset threshold, the adjustment of the pressure deviation is paused or the lifting speed of the exceeding point is limited until the displacement difference returns to a safe range. This avoids excessive stress concentration or structural damage to the beam due to excessive displacement differences at each point, ensuring the safety and stability of the large-span steel-concrete composite beam during support replacement lifting, and improving the accuracy and reliability of the lifting operation.

[0012] Optionally, the determination of the preset threshold for displacement difference is based on the following: the limit allowable opening displacement of the steel-concrete joint surface of the large-span steel-concrete composite beam is 2.5mm, the preset threshold for displacement difference is set to 2mm, and the safety reserve factor is 0.8.

[0013] By adopting the above technical solution, based on the ultimate allowable opening displacement of 2.5mm at the steel-concrete interface of the large-span steel-concrete composite beam, a safety reserve factor of 0.8 is introduced, and the preset threshold for the jacking displacement difference is precisely set to 2mm. This technical feature constructs a 20% safety buffer zone before the ultimate failure value, ensuring that the steel-concrete interface will not crack due to excessive displacement under the most unfavorable working conditions, and avoiding frequent shutdowns due to the control system being too sensitive because the threshold is too small. At the same time, it provides precise design input for the coordination relationship between the jacking speed and the PLC scanning cycle, thus achieving the optimal balance between ensuring the absolute safety of the beam structure and ensuring the continuous feasibility of construction.

[0014] Optionally, the lifting speed v, the single scan cycle t of the PLC controller, and the preset threshold h of the displacement difference satisfy the following safety coordination constraint: v×t≤h; where v×t represents the displacement increment generated by any jack in a single scan cycle. The constraint ensures that the maximum displacement increment at any point before the PLC controller detects the displacement deviation does not exceed the preset threshold of the displacement difference, reserving a safety margin for system intervention; the lifting speed v is 1mm / min, the lifting height per stage is 5mm, and the preset threshold h of the displacement difference is 2mm.

[0015] By adopting the above technical solution and limiting the coordination between the jacking speed, the jacking height per stage, and the displacement difference threshold, it is possible to ensure that the displacement difference at each jacking point remains within a controllable range during the synchronous jacking process of replacing the bearings of large-span steel-concrete composite beams under different forces. The jacking speed of 1 mm / min, the jacking height per stage of 5 mm, and the displacement difference threshold of 2 mm work together to give the PLC controller sufficient time to accurately control the jacking situation at each point. If the displacement difference exceeds the threshold, the jacking can be paused or adjusted in time to avoid deformation or damage to the beam due to excessive displacement difference, thus ensuring the safety and stability of the jacking process and improving the quality and efficiency of the bearing replacement construction.

[0016] Optionally, it also includes spatial attitude closed-loop control: based on the real-time feedback values ​​of each displacement sensor, the longitudinal slope change and transverse slope change of the beam are obtained through spatial coordinate calculation; when the longitudinal slope change or transverse slope change exceeds the design allowable value, the PLC controller automatically calculates the compensation lifting amount of each jack, and prioritizes the jacks located in the deformation-sensitive area of ​​the beam for micro-adjustment until the beam slope is restored to the design allowable range; the deformation-sensitive area is the beam stiffness abrupt change area or stress concentration area determined according to the finite element analysis model.

[0017] By adopting the above technical solution, spatial attitude closed-loop control can effectively ensure the stability and safety of large-span steel-concrete composite beams during the jacking process. During the jacking process, displacement sensors provide real-time data feedback, and spatial coordinate calculations can accurately obtain the longitudinal and transverse slope changes of the beam. Once the longitudinal or transverse slope changes exceed the design allowable values, the PLC controller responds quickly and automatically calculates the compensation jacking amount for each jack; priority is given to making minor adjustments to the jacks in the beam deformation-sensitive areas, which can prevent structural damage to the beam due to excessive local deformation; in this way, the slope deviation of the beam can be corrected in a timely manner, restoring the beam slope to the design allowable range; this control method ensures that the beam maintains a good spatial attitude throughout the jacking process, reduces the adverse effects on the beam structure caused by excessive slope changes, thereby improving the quality and efficiency of support replacement work, reducing construction risks, and ensuring the smooth progress of the entire large-span steel-concrete composite beam jacking project.

[0018] Optionally, the PLC controller is communicatively connected to a host industrial control computer, which stores a finite element analysis model of the large-span steel-concrete composite beam. During the jacking process, the host industrial control computer receives the measured displacement data transmitted by the PLC controller in real time and inputs it into the finite element analysis model to dynamically invert the current stiffness distribution state of the beam. When the deviation between the inverted stiffness and the design stiffness exceeds a preset threshold, the host industrial control computer sends the corrected target pressure data of each jack to the PLC controller, and the PLC controller updates the control target of each jack accordingly.

[0019] By adopting the above technical solution, during the synchronous jacking process of replacing the supports of a large-span steel-concrete composite beam, the PLC control system, which stores a finite element analysis model of the large-span steel-concrete composite beam, can input the measured displacement data into the model in real time and dynamically invert the current stiffness distribution of the beam. This allows the system to accurately grasp the stiffness changes of the beam during the jacking process. When the deviation between the inverted stiffness and the design stiffness exceeds a preset threshold, the system automatically corrects the target pressure data of each jack. This automatic correction mechanism can effectively cope with the stiffness changes that may occur in the beam during the jacking process, avoid the problem of uneven jacking caused by stiffness differences, and ensure the stability and safety of the beam during the jacking process. At the same time, the real-time dynamic inversion and correction process can adjust the jacking parameters in a timely manner according to the actual stiffness state of the beam, improving the accuracy and reliability of the jacking operation, reducing the uncertainty caused by stiffness changes, and ensuring the smooth progress of the large-span steel-concrete composite beam support replacement work.

[0020] Optionally, an independent contact state diagnosis step is also included: During the dual closed-loop interlock control process, the PLC controller synchronously establishes the force-displacement relationship curve of each lifting point and compares it with the pre-stored theoretical force-displacement curve. When the slope deviation between the two exceeds the preset threshold of the deviation slope, the system records the abnormal contact state information of the point where the slope deviation occurs, and automatically adjusts the lifting speed parameters of the point where the slope deviation occurs after the current level of lifting is completed and before the next level of lifting is started.

[0021] By adopting the above technical solution, during the dual closed-loop interlocking control process, the PLC controller synchronously establishes the force-displacement relationship curves of each jacking point and compares them in detail with the pre-stored theoretical force-displacement curves. Once the slope deviation between the two exceeds the preset threshold, the system can promptly record the abnormal contact status information of the point where the slope deviation occurs. This helps to quickly locate the jacking point where there may be a problem. Moreover, the system will automatically adjust the jacking speed parameters of the point where the slope deviation occurs after completing the current jacking and before starting the next jacking. This can prevent the jacking imbalance caused by abnormal contact status from further deteriorating, ensuring that each point can work more stably as expected during the subsequent jacking process. This effectively improves the safety, stability, and accuracy of the jacking operation for replacing the support of the large-span steel-concrete composite beam, ensuring the smooth progress of the entire process.

[0022] Optionally, the removal of the old bearing pad stone adopts a hydraulic crushing process, specifically including: while the first jack group is kept in the lifting and locking state, the PLC controller continuously monitors the pressure changes of each jack, uses hydraulic crushing equipment, adjusts the pressure to 280~320MPa, and crushes the concrete pad stone with a grade greater than C45 in layers, with the thickness of each layer controlled at 2~4cm. Before crushing, a rebar detector is used to locate the position of the pre-embedded rebar and avoid it; after each layer is crushed, the PLC controller checks the deviation between the pressure value of each jack and the locking value, and when the deviation exceeds ±3% of the locking pressure, the crushing operation is suspended.

[0023] By adopting the above technical solution and deeply integrating the hydraulic crushing process with the PLC jacking monitoring system, an intelligent pressure verification mechanism is introduced during the removal of old support pad stones: before crushing operations, a rebar detector is used to avoid pre-embedded rebars to prevent structural damage; during crushing, the pressure is strictly limited to 280~320MPa and the layer thickness is 2~4cm to achieve precise stripping of high-strength concrete of C45 and above; more importantly, after each layer is crushed, the PLC controller automatically verifies the deviation between the pressure value of each jack and the locking value, and stops the operation if it exceeds ±3%. This technical feature elevates the single demolition process to an intelligent control link linked with the jacking system. It protects the integrity of the cap beam and beam structure through precise hydraulic parameters and rebar avoidance, and ensures the stress stability of the jacking system during crushing through real-time pressure monitoring. It effectively prevents beam instability caused by uneven removal of pad stones or sudden load changes, and achieves two-way interlocking between demolition operations and jacking safety.

[0024] Optionally, the actual measurement of the support reaction force is carried out after the steel support is replaced and installed, specifically including: With the replacement steel support already installed and in place, maintain and lock the lifting bearing state of the first jack group on the beam, so that the beam load is transferred through the replacement steel support. A second jack group is placed on the top surface of the same cover beam next to the first jack group. The second jack group is connected to the PLC controller. The total rated lifting capacity of the second jack group is greater than the total rated lifting capacity of the first jack group. The second jack assembly was lifted so that the movable end of the second jack assembly was in close contact with the steel plate under the replacement steel support, but it had not yet borne the load of the beam. Slowly unload the first jack group and detach the movable end of the first jack group from the bottom of the beam. Smoothly transfer the weight of the beam to the second jack group, maintain pressure, and record the first measured reaction force value. The measured data were compiled into a support reaction force calculation report and submitted to the design unit for confirmation. Based on feedback from the design unit, several trial jackings and data verifications were conducted until the design unit confirmed the final reaction force value. Perform a complete jacking operation based on the final reaction force value and lock the second jack assembly.

[0025] By adopting the above technical solution, the actual support reaction force of the beam can be accurately obtained by measuring the support reaction force after the replacement steel bearing is installed. First, the first jack group is kept in a lifting and bearing state on the beam and locked, so that the beam load is transferred through the new bearing, creating stable conditions for subsequent measurements. The second jack group, with a larger total rated lifting capacity, is placed to ensure that it can stably bear the self-weight of the beam. The second jack group is lifted so that it is in contact with the steel plate under the bearing but does not bear the load. Then, the first jack group is slowly unloaded, and the self-weight of the beam is stably transferred to the second jack group. The first measured reaction force value can be accurately recorded. The measured data is submitted to the design unit for confirmation, and after multiple trial lifting and data verification, the accurate reaction force value is finally determined. The second jack group is fully lifted and locked according to the final reaction force value, ensuring the stability and safety of the beam after the replacement of the bearing of the large-span steel-concrete composite beam, providing a reliable guarantee for the long-term stable operation of the bridge.

[0026] Optionally, it also includes a tiered emergency protection procedure: when the actual pressure value of any jack exceeds ±10% of the corresponding design pressure data and the duration exceeds the preset time threshold, the PLC controller triggers a first-level warning and automatically reduces the lifting speed of the jack to 50% of the normal speed; when the actual pressure value of any jack exceeds ±15% of the corresponding design pressure data, the PLC controller triggers a second-level protection, locks all jacks and stops the lifting operation; when the displacement rate detected by any displacement sensor exceeds the preset displacement rate threshold, the PLC controller triggers an emergency brake, closes all electro-hydraulic servo valves and initiates hydraulic locking.

[0027] By adopting the above technical solution and introducing graded emergency protection steps, a multi-level, progressive jacking safety protection system is constructed: when the pressure deviation exceeds ±10% and continues for an extended period, a first-level warning is triggered and the speed is actively reduced, mitigating the abnormal development and avoiding frequent shutdowns; when the pressure deviation exceeds ±15%, a second-level protection is triggered and the entire system is immediately locked, implementing forced intervention before the structural damage critical point; when the displacement rate exceeds the limit, emergency braking is triggered and the electro-hydraulic servo valve is closed, cutting off the possibility of further displacement from the power source. This technical feature complements the dual closed-loop interlocking control, upgrading the original active control relying on PID regulation to a full life-cycle safety management system with anomaly self-diagnosis, risk-level response, and hard shutdown in extreme situations. It achieves a complete closed loop from preventive control to emergency protection, significantly improving the fault tolerance and inherent safety of the jacking system under extreme conditions such as sensor failure and oil leakage.

[0028] A synchronous jacking system for replacing supports of large-span steel-concrete composite beams, used to perform the synchronous jacking method for replacing supports of large-span steel-concrete composite beams as described in any of the above claims, comprising: Multiple lifting units, each lifting unit includes a jack, a pressure sensor and a displacement sensor independently installed on the jack, and the rated lifting force of the jack of each lifting unit is independently configured according to the design reaction force of the support point. The hydraulic power station is connected to each jack through an independent oil supply line. Each oil supply line is equipped with an electro-hydraulic servo valve. The flow rate specification of each electro-hydraulic servo valve is selected independently according to the target pressure and lifting speed of the corresponding jack. The PLC controller is electrically connected to each pressure sensor, each displacement sensor and each electro-hydraulic servo valve. The PLC controller has pre-stored the design pressure data of each fulcrum. The PLC controller is configured to execute the control method described above with the design pressure data of each fulcrum as the independent control target of each jack. The host industrial control computer is connected to the PLC controller and stores the finite element analysis model of the large-span steel-concrete composite beam. It is used to receive the measured data transmitted by the PLC controller and perform finite element dynamic inversion calculation.

[0029] By adopting the above technical solution, the system can accurately execute the synchronous different force jacking method for replacing the supports of large-span steel-concrete composite beams. It utilizes pressure and displacement sensors in the jacking unit to monitor the jacking force and displacement in real time. The hydraulic power station supplies oil to the jacks through independent oil supply pipelines and electro-hydraulic servo valves. The PLC controller precisely controls the oil supply to the jacks based on sensor feedback, achieving differentiated jacking of each support point according to the design reaction force. It can perform closed-loop spatial attitude control to ensure the beam slope is within the design allowable range; it can dynamically invert the beam stiffness distribution and correct the target pressure data of the jacks; it controls the jacking based on reasonable preset displacement difference thresholds and cooperative relationships; and it can perform contact state diagnosis to ensure the safety and accuracy of the jacking process.

[0030] In summary, this application includes at least one of the following beneficial technical effects: This application integrates the complete construction process for replacing the supports of large-span steel-concrete composite beams. During the jacking phase, it adopts a dual-control strategy, using the design pressure data of each support point as the main control parameter and vertical displacement as the auxiliary parameter. This fundamentally changes the traditional jacking process that uses uniform displacement as the sole control objective, solving the problem of additional stress easily generated during the jacking process of large-span steel-concrete composite beams due to uneven stress at each support point. This effectively avoids cracking of the steel-concrete interface and damage to the bridge deck pavement. Simultaneously, by independently installing pressure and displacement sensors on the jacks at each jacking point, a dual closed-loop control logic of force control and displacement safety interlocking is constructed. This solves the contradictory technical challenge of accurately achieving the design reaction force at each support point while preventing structural damage due to excessive displacement differences during the jacking process of large-span beams. This application elevates the control objective from the displacement difference at each point to the overall spatial attitude of the beam by introducing spatial attitude closed-loop control and finite element dynamic inversion. It also deeply integrates the structural theoretical model with construction process monitoring, enabling the jacking control to adapt to the actual distribution of structural stiffness, significantly improving the intelligence level and quality control accuracy of the jacking operation. By defining the basis for determining key parameters and their collaborative relationships, the construction control has a clear mechanical basis and system reliability guarantee, solving the problem that conventional construction parameters lack specificity and are difficult to ensure structural safety. This application specifically applies hydraulic crushing technology to the removal of high-grade foundation stones, solving the problem that traditional mechanical chiseling methods easily cause damage to the cap beam concrete and reinforcing steel. By replacing jacks and conducting multiple trial jacking tests, the actual measurement and calibration of the support reaction force is achieved, solving the problem that the support reaction force in traditional processes relies solely on theoretical calculations and is disconnected from the actual force. In addition, this application also protects a synchronous different force jacking system for implementing the above methods, forming dual protection of the method and the system, providing patentees with a more convenient way to protect their rights.

[0031] Figure 1 This is a flowchart illustrating the synchronous jacking method with different forces for replacing the supports of the large-span steel-concrete composite beam described in Example 1. Figure 2 This is a schematic diagram of the synchronous different force jacking system for replacing the supports of the large-span steel-concrete composite beam in Example 1. Figure 3 This is a schematic diagram of the arrangement structure of the replacement steel support and the second jack assembly as described in Embodiment 1; Figure 4 This is a schematic diagram of the arrangement structure of the replacement steel support and the new support pad as described in Embodiment 1; Figure 5 This is a schematic diagram of the arrangement structure of the old support pad stone and the first jack group described in Embodiment 1; Figure 6 This is a schematic diagram of the process of implementing dual closed-loop interlock control by the PLC controller described in Embodiment 1; Figure 7 This is a schematic diagram of the process of implementing graded emergency protection by the PLC controller described in Embodiment 1; Figure 8 This is a flowchart illustrating the contact status diagnosis steps implemented by the PLC controller in Embodiment 2. Figure 9 This is a schematic diagram of the process of implementing spatial attitude closed-loop control by the PLC controller described in Embodiment 2; Figure 10 This is a schematic diagram of the process for dynamically inverting the stiffness distribution of a beam based on a finite element analysis model, as described in Example 2. In the diagram: 1. Beam; 2. Cap beam; 3. Old bearing pad; 4. New bearing pad; 5. First jack assembly; 6. Support steel plate; 7. Second jack assembly; 8. PLC controller; 9. Hydraulic power station; 10. Pressure sensor; 11. Displacement sensor; 12. Electro-hydraulic servo valve; 13. Independent oil supply pipeline; 14. Replacement steel support. Detailed Implementation

[0032] The technical solutions of various embodiments of this application will be clearly and completely described below with reference to the figures. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] To more clearly illustrate the technical solution of this application, the following embodiments are all illustrated using a (40+60+40) m three-span steel-concrete composite continuous beam bridge on a highway as an example. The design reaction force of a single mid-support of the bridge is 8500 kN, and that of the side supports is 4200 kN. The method of this application is now used for bearing replacement. Example 1

[0034] Reference Figure 1 The synchronous jacking method for replacing supports of large-span steel-concrete composite beams provided in this application includes the following steps: The first jack group 5 is used to lift the beam 1. The first jack group 5 is connected to the PLC controller 7. During the lifting process, the design pressure data of each support point is used as the main control parameter and the vertical displacement is used as the auxiliary parameter for dual control, so as to lift each support point to the preset height according to the design reaction force. After jacking up, remove the old support pad stones 3; Install and replace steel support 13; After the replacement steel support 13 is in place, the support reaction force is measured by replacing it with jacks. The measured support reaction force data is reported to the design unit for confirmation. The jacking is carried out and locked according to the confirmed final reaction force value. Pour the new support pad 4 and lower the main beam.

[0035] Specifically, the first step is construction preparation. This involves inspecting tools and equipment, preparing sufficient materials with a surplus based on statistical results, and providing technical and safety briefings to all participants.

[0036] Step 2: Erect the working platform. Pre-set 14 lifting points on each side of the cap beam 2, using M24×400 anchor bolts for insertion. Drill holes to a depth of 350mm, and insert the anchor bolts after drilling. Use Ф16 steel wire ropes threaded through and fixed to the square steel at the lifting points. Secure a cross-shaped buckle 20cm from the end of the square steel to prevent the wire rope from slipping out. Erect a mesh of longitudinal and transverse steel pipes, spaced 0.5m×0.5m apart. Secure the longitudinal steel pipes to the transverse pipes using cross-shaped fasteners, and use fasteners to connect the longitudinal steel pipe joints. Lay steel frame panels and secure them reliably to the steel pipes using #12 double-strand iron wire. Securely bind the steel frame panels together to ensure no gaps. Install guardrails and protective netting. The guardrail height should be no less than 1.2m, with three transverse steel pipes for protection. Install a toe board at the bottom edge of the guardrail, with a toe board height of no less than 16cm.

[0037] Step 3: Prepare the work surface. Clean up any debris on the cap beam 2. Remove any remaining concrete on the top surface of cap beam 2 that may affect the jack positions using an electric or pneumatic hammer. Clean up any other loose debris manually. Strictly level the top surface of all cap beam 2 locations where jacks are positioned using dry-hardened mortar to ensure the jacks are subjected to vertical force.

[0038] Step 4: On-site data collection. Investigate the height of the four corners between the bottom of the beam and the top of the bearing pad at the support, and whether the top surface of the bearing pad and the bottom of the beam are level, to determine the elevation of the new bearing pad 4; for areas where the bottom of the beam is not level, use wedge-shaped steel plates to level it. Verify the model, size, quantity, and weight of the upper supports of the same cap beam 2, and determine the jack configuration and control targets based on the relevant reaction force data of the designed supports.

[0039] Step 5: Installation and commissioning of the lifting system. (Reference) Figures 2 to 4 The first jack group 5 is used to lift the beam 1. The first jack group 5 is connected to the PLC controller 7. The first jack group 5 consists of multiple jacks arranged on the top surface of each cap beam 2. The total lifting capacity of the jacks on the top surface of each cap beam 2 is not less than twice the reaction force of the support point on the top surface of the cap beam 2, and all jacks on the same cap beam 2 are of the same model. The jacks are arranged at the longitudinal ribs of the steel beam, and a support steel plate 51 with a thickness of not less than 20 mm and an area of ​​not less than 500×300 mm is placed between the jacks and the bottom of the beam. The bottom surface of the jacks is leveled with dry hard mortar and supported with a support steel plate 51 with a thickness of not less than 20 mm and an area of ​​not less than 250×250 mm. refer to Figures 2 to 4A pressure sensor 9 and a displacement sensor 10 are independently installed on each jack at each lifting point. The pressure sensor 9 is used to monitor the actual lifting force at that point in real time, and the displacement sensor 10 is used to monitor the actual lifting displacement at that point in real time. The design pressure data of each support point is input into the PLC controller 7 as the independent control target for each jack. The hydraulic power station 8 is connected to each jack through an independent oil supply line 12, and each oil supply line is equipped with an electro-hydraulic servo valve 11. The PLC controller 7 is electrically connected to each pressure sensor 9, each displacement sensor 10, and each electro-hydraulic servo valve 11.

[0040] refer to Figures 2 to 4 After connecting all the jacks and displacement sensors 10 to the PLC controller 7, a test jacking is performed so that the beam 1 moves slightly but does not detach from the support. After stopping for 5 to 10 minutes, observe whether there is any oil leakage at each connection, whether the extension and retraction of the jacks are normal, and whether the changes of the sensors are normal. During the test jacking, the effective stroke of each jack is measured. If the stroke is insufficient, the thickness of the support steel plate 51 on the jack is adjusted so that the effective stroke of each jack is roughly the same.

[0041] Step Six: Monitoring System Installation and Debugging. (Reference) Figures 2 to 4 While the PLC controller 7 monitors the force on all jacks, dial gauge observation points are set on both sides of each pier cap beam 2. The displacement height is measured manually with a steel ruler and compared with the force situation. The measurement is always taken at the same location to ensure the accuracy of the data.

[0042] Step 7: Staged synchronous jacking and monitoring. During the jacking process, the design pressure data of each support point is used as the main control parameter, and the vertical displacement is used as the auxiliary parameter for dual control, so as to jack each support point to the preset height according to the design reaction force.

[0043] refer to Figure 6The specific control method includes dual closed-loop interlocking control: the PLC controller 7 receives feedback values ​​from each pressure sensor 9 in real time and compares them with the corresponding design pressure data. By independently controlling the opening of each electro-hydraulic servo valve 11, the actual lifting force value at each point approaches and stabilizes at its design pressure data. Simultaneously, the PLC controller 7 receives feedback values ​​from each displacement sensor 10 in real time, calculates the displacement difference between each point, and when the displacement difference exceeds a preset threshold, it suspends the adjustment of the pressure deviation or limits the lifting speed of the exceeding point until the displacement difference returns to a safe range. Specifically, the allowable opening displacement of the steel-concrete composite beam's steel-concrete interface is 2.5 mm, and the control threshold is set to 2 mm. To ensure the absolute safety of the beam 1, the project team established a solid model of the bridge using ANSYS finite element software. Simulation results show that when the displacement difference between each support reaches 2.5 mm, the maximum principal tensile stress at the steel-concrete interface has reached the standard value of the tensile strength of C50 concrete. To maintain a 20% safety margin, the preset threshold for displacement difference h is strictly controlled at 2mm; the lifting speed v is set to 1mm / min, the lifting height per stage is set to 5mm, and the preset threshold for displacement difference h is set to 2mm. Furthermore, v, t, and h satisfy the following synergistic relationship: v×t≤h, where t is the single scan cycle of PLC controller 7 in min, and v×t is the displacement increment, to ensure that the displacement increment generated within a single scan cycle of PLC controller 7 does not exceed the allowable displacement difference threshold. That is, even if a jack lifts at its maximum speed v in a single scan cycle due to loss of control or other reasons, the resulting displacement increment will not exceed the allowable displacement difference threshold h. This provides sufficient safety margin for the system to intervene and adjust in the next cycle. For example, when the single scan cycle t of the PLC controller 7 is 0.1s, which is approximately 0.0017min, even if a jack lifts at its maximum speed v=1mm / min in a single scan cycle, the resulting displacement increment will only be approximately 0.0017mm, which is far less than the allowable displacement difference threshold of 2mm. This ensures that the system has sufficient time to intervene before the displacement difference exceeds the safe range. During the lifting process, 1-2 observers are assigned to observe whether there are cracks or deformations on the beam top, bridge deck, and negative bending moment section. If any abnormalities are found, the lifting is stopped immediately and adjustment measures are taken.

[0044] refer to Figure 7 It also includes tiered emergency protection. During the synchronous lifting process with different forces, the PLC controller 7 simultaneously executes the tiered emergency protection program, constructing a multi-layered, progressive safety protection system: Level 1 Early Warning and Active Speed ​​Reduction: The PLC controller 7 monitors the feedback values ​​of the pressure sensors 9 of each jack in real time and compares them with the design pressure data of the corresponding fulcrum. When the actual pressure value of any jack exceeds ±10% of the corresponding design pressure data and the duration exceeds the preset time threshold, the PLC controller 7 triggers a Level 1 early warning. While maintaining the continuity of the lifting operation, it automatically reduces the lifting speed of that jack to 50% of the normal speed. In this embodiment, the preset time threshold is 3 seconds. This mechanism aims to provide a buffer time for abnormal working conditions, both to alleviate the further development of pressure deviation and to avoid the impact of frequent shutdowns on construction efficiency.

[0045] Secondary protection and system-wide locking: When the actual pressure value of any jack exceeds ±15% of the corresponding design pressure data, the PLC controller 7 judges it as a serious overload condition, immediately triggers secondary protection, locks all jacks and stops the lifting operation, and issues an audible and visual alarm signal; this level of protection implements forced intervention before the critical point of structural damage to ensure the structural safety of beam 1.

[0046] Emergency braking and hydraulic locking: When the displacement rate detected by any displacement sensor 10 exceeds the preset displacement rate threshold, the PLC controller 7 judges it as a risk of sudden displacement loss of control, immediately triggers emergency braking, closes all electro-hydraulic servo valves 11 to cut off the power source, and starts the hydraulic locking function of the hydraulic power station 8 to keep each jack in its current load state and prevent the beam 1 from undergoing abnormal displacement due to sudden situations; wherein, in this embodiment, the preset displacement rate threshold is 0.5 mm / s.

[0047] Synergistic Relationship between Graded Emergency Protection and Dual-Loop Interlocking Control: Graded emergency protection serves as a supplement and fallback mechanism to dual-loop interlocking control, forming a dual safety architecture of active control and emergency protection. Under normal operating conditions, dual-loop interlocking control is responsible for the fine-tuning of pressure control and displacement safety interlocking. When the system detects abnormal operating conditions exceeding the dual-loop regulation capacity, such as sensor failure, oil leakage, or sudden overload, the graded emergency protection program intervenes step by step according to preset thresholds, achieving a complete closed loop from preventative control to emergency protection.

[0048] Step 8: Remove the old support pad stone 3 after jacking. After the jacking of beam 1 is completed, hydraulic crushing of the support pad stone is carried out. Hydraulic crushing equipment is used, and the pressure is adjusted to 280~320MPa. This pressure range is determined based on the ultimate tensile strength of C45-C55 high-strength concrete and the optimal energy efficiency ratio of hydraulic crushing. Concrete pad stones with a grade greater than C45 are crushed in layers, with the thickness of each layer controlled at 2~4cm. Before crushing, a rebar detector is used to locate and avoid the pre-embedded rebar. After crushing, the base residue is rinsed with low-pressure water, and the flatness of the base is checked to ensure that there is no residual loose aggregate, no exposed rebar, or damage.

[0049] Step 9: Install and replace steel support 13. Lay out the support on the bottom of the steel-concrete composite beam. Before laying out, clean the beam bottom surface to remove rust, concrete residue, and oil. Mark the support center, bolt hole positions, and support edge outline, and set 2-3 verification reference points. The deviation between the support center and the beam axis 1 should not exceed 1mm, and the bolt hole spacing deviation should not exceed 0.5mm. Use a magnetic drill to drill, employing low-speed drilling and segmented chip removal. The initial speed should be controlled at 300-500 r / min. When drilling to half the designed depth, pause to clean the drill chips before continuing drilling. After drilling, use a hole cleaner to remove residual drill chips and blow clean the borehole. After installing and replacing steel support 13, use a level to level the surface. Place stainless steel leveling shims between the support base plate and the beam bottom for adjustment, ensuring the height difference between the four corners of the support is no more than 1mm.

[0050] Step 10: Perform actual measurement of support reaction force by replacing the jacks. After the replacement steel support 13 is installed in place, maintain and lock the lifting and bearing state of the first jack group 5 on the beam 1, so that the load of the beam 1 is transferred through the replacement steel support 13. A second jack group 6 is placed on the top surface of the same cover beam 2 next to the first jack group 5. The total rated lifting capacity of the second jack group 6 is greater than that of the first jack group 5. The second jack group 6 is lifted so that its top is in close contact with the steel plate under the support but has not yet borne the load of the beam 1. The first jack group 5 is slowly unloaded and removed from the bottom of the beam. The weight of the beam 1 is smoothly transferred to the second jack group 6. The pressure is maintained for at least 15 minutes and the first measured reaction force value is recorded to ensure that the internal friction resistance of the jacks is completely overcome and the oil pressure fluctuation tends to be stable, thereby obtaining a stable and reliable first measured reaction force value. The measured data is compiled into a support reaction force measurement calculation sheet and submitted to the design unit for confirmation. Second and third test jacking and data verification are carried out according to the feedback from the design unit until the design unit confirms the final reaction force value. The second jack group 6 is fully lifted according to the final reaction force value and locked.

[0051] Step 11: Pour the new support pad stone 4. After all the support reaction lifting work is completed, tie the reinforcement of the support pad stone, ensuring that the spacing and row spacing deviation of the reinforcement is no more than 5mm, and the anchorage length meets the design requirements; after the formwork is installed, seal the joints with sealing strips, and use a spirit level to ensure the plane position and top elevation of the pad stone. Pour the special grouting concrete, and use a screed to level it when it reaches the design elevation. Before initial setting, perform 2-3 finishing operations to ensure the flatness of the top surface. After demolding, cover with geotextile and water for curing for no less than 7 days. Subsequent work can only be carried out when the concrete strength reaches 85% or more of the design strength.

[0052] Step 12: Lower the main beam and dismantle the jacking system. Simultaneously lower the main beam step by step, and dismantle the monitoring system and jacking system; repair the partially damaged protective layer concrete of the cap beam 2 with polymer mortar, and clean the top of the cap beam 2; when dismantling the working platform, follow the principle of dismantling from top to bottom and from auxiliary to main in an orderly manner.

[0053] The implementation principle of this embodiment is as follows: By independently setting pressure sensors 9 and displacement sensors 10 on the jacks at each lifting point, a dual closed-loop control logic of force value control and displacement safety interlock is constructed. Using the design pressure data of each support point as the control target, the actual force value is monitored in real time, and the oil supply is adjusted independently to make the actual force value at each point approach the design value; simultaneously, the displacement difference is monitored in real time, and when the displacement difference exceeds the standard, force value adjustment is paused or the lifting speed is limited to ensure the safety of the beam 1's posture. This control mechanism solves the technical problem of structural damage caused by additional stress during the lifting process of large-span steel-concrete composite beams due to uneven force distribution at each support point. Example 2

[0054] Reference Figures 8 to 10 The difference between this embodiment and Embodiment 1 is that it further integrates multiple control strategies such as spatial attitude closed-loop control, finite element dynamic inversion, parameter scientific design and contact state diagnosis, forming a comprehensive intelligent lifting control method.

[0055] Reference Figures 8 to 10 During the lifting process, in addition to executing the dual closed-loop interlock control described in Embodiment 1, PLC controller 7 also simultaneously executes the following control steps: First, refer to Figure 8 The system performs contact status diagnosis. The PLC controller 7 synchronously establishes force-displacement relationship curves for each jacking point and compares them with pre-stored theoretical force-displacement curves. When the slope deviation exceeds a preset threshold, the system records abnormal contact status information for the point where the slope deviation occurs. After completing the current jacking stage and before starting the next stage, the system automatically adjusts the jacking speed parameters for the point where the slope deviation occurs to ensure normal contact between the beam bottom and the jack at each point. Reference Figure 8 The theoretical force-displacement curve is pre-generated according to the following method: Based on the finite element model of beam 1, under the simulated ideal contact state, the theoretical force-displacement relationship of each point within the small lifting range is calculated, the reference curve is generated and stored in PLC controller 7.

[0056] Reference Figure 8The criterion for judging the slope deviation is as follows: During each stage of jacking, the PLC controller 7 calculates the instantaneous slope of the force-displacement curve at each point in real time, i.e., ΔF / Δs, where ΔF is the force increment and Δs is the displacement increment, and compares it with the slope of the theoretical curve in the corresponding displacement segment; when the instantaneous slope deviation exceeds ±25% of the theoretical slope, the contact state at that point is judged to be abnormal.

[0057] Reference Figure 8 Typical causes of abnormal contact include: local gaps between the jack and the beam bottom support plate 51 causing eccentric compression; uneven padding under the support plate 51 causing the jack to tilt; and local unevenness at the bottom of the beam resulting in insufficient contact area.

[0058] Reference Figure 8 The automatic adjustment measures are as follows: for abnormal contact points, the lifting speed is reduced to 60% of the normal speed in the next stage of lifting, and the preset threshold of displacement difference at that point is tightened to 70% of the original value, so as to carry out lifting with a more conservative strategy.

[0059] Secondly, refer to Figure 9 The system performs closed-loop spatial attitude control. Under normal contact conditions, the PLC controller 7 calculates the longitudinal and transverse slope changes of beam 1 using spatial coordinates based on real-time feedback values ​​from each displacement sensor 10. When the longitudinal or transverse slope changes exceed the design allowable values, the PLC controller 7 automatically calculates the compensation lifting amount for each jack and prioritizes minor adjustments to the jacks located in the deformation-sensitive area of ​​beam 1 until the slope of beam 1 returns to the design allowable range, ensuring the overall attitude of beam 1 meets design requirements. Taking the (40+60+40)m three-span continuous beam used in this embodiment as an example, its finite element analysis model shows that the area near the mid-support point 10m from the beam end is a stress concentration area at the steel-concrete interface, which is the deformation-sensitive area described in this method. When the system detects that the transverse slope change exceeds the limit, the PLC controller 7 will prioritize adjusting the jacks located in this area for compensation lifting.

[0060] Reference Figure 9 The specific method for solving the spatial coordinates is as follows: take the support point at one end of the beam 1 as the origin of the coordinates, and establish a spatial coordinate system with the longitudinal direction of the beam 1 as the X-axis, the transverse direction as the Y-axis, and the vertical direction as the Z-axis; the vertical displacement values ​​measured by the displacement sensors 10 at each lifting point constitute the Z-coordinate change of each feature point of the beam 1.

[0061] Reference Figure 9 The calculation method for longitudinal slope change is as follows: along the longitudinal direction of beam 1, i.e. the X-axis direction, take the readings of displacement sensors 10 at each support point on the same side, and fit a straight line using the least squares method. The change in the slope of this straight line is the longitudinal slope change.

[0062] Reference Figure 9 The method for calculating the change in cross slope is as follows: On the same cross section, take the difference between the readings of displacement sensors 10 at symmetrical points on both sides of beam 1, divide it by the lateral distance between the two sensors, and the change in cross slope of the cross section is obtained.

[0063] Reference Figure 9 When the longitudinal slope change exceeds 0.1% or the cross slope change exceeds 0.05%, the PLC controller 7 starts compensation adjustment, where 0.1% and 0.05% are determined according to the allowable deviation of the bridge design.

[0064] Reference Figure 10 Simultaneously, finite element dynamic inversion is performed. The host industrial control computer communicates with the PLC controller 7 via industrial Ethernet, with a communication cycle of no more than 100ms. The host industrial control computer has a pre-stored three-dimensional finite element model of the large-span steel-concrete composite beam based on the design drawings. The model includes the main structural components such as steel beams, concrete bridge decks, shear connectors, and supports.

[0065] Reference Figure 10 The specific implementation process of dynamic inversion is as follows: After receiving the measured displacement data of each point transmitted by the PLC controller 7, the host industrial control computer uses the measured displacement as the boundary condition and adopts the inverse analysis method to solve for the equivalent stiffness parameters of each section of beam 1. The inverse analysis method adopts the model correction technology based on the least squares method. By continuously adjusting the stiffness reduction coefficient of each beam segment in the finite element model, the sum of square errors between the displacement of each measuring point calculated by the model and the displacement measured by the PLC is minimized, thereby inverting the current stiffness distribution state of beam 1. When the deviation between the inverted stiffness value of a certain section and the design stiffness value exceeds the preset threshold, the host industrial control computer recalculates the target reaction force value of each support point according to the corrected stiffness distribution and sends the corrected target pressure data to the PLC controller 7. For example, when the measured data shows that the mid-span displacement is large while the displacement near the support is small, the finite element inversion may identify that the actual stiffness of the mid-span region is lower than the design value. At this time, the system will appropriately reduce the target lifting force of the support near the mid-span to reduce the additional bending moment in the mid-span region.

[0066] The implementation principle of this embodiment is as follows: multiple advanced control strategies are organically integrated to form a multi-level, multi-dimensional intelligent lifting control system. Furthermore, there is a hierarchical progression and information-sharing collaborative relationship between each control strategy: contact state diagnosis provides contact quality assessment for the dual-loop interlocking control; only when the contact state at each point is normal can the force-displacement dual-loop control obtain accurate feedback signals; the measured displacement data generated by the dual-loop interlocking control is simultaneously shared by the spatial attitude closed-loop control and the finite element dynamic inversion; the target pressure data corrected by the finite element dynamic inversion directly updates the pressure control target in the dual-loop interlocking control; the compensation lifting amount calculated by the spatial attitude closed-loop control is superimposed on the displacement target of the dual-loop interlocking control; the above control strategies do not operate independently and in parallel, but rather form a multi-level nested control architecture in the PLC controller 7 and the host industrial control computer. The output of any level serves as the input or constraint condition for other levels, collectively constituting a complete intelligent control system. Example 3

[0067] Reference Figures 2 to 4 This application also discloses a synchronous jacking system for replacing supports of large-span steel-concrete composite beams under different forces, used to execute any of the synchronous jacking methods for replacing supports of large-span steel-concrete composite beams under different forces described in the above embodiments, including: Multiple lifting units, each lifting unit includes a jack, a pressure sensor 9 and a displacement sensor 10 independently installed on the jack, and the rated lifting force of the jack of each lifting unit is independently configured according to the design reaction force of the support point. The hydraulic power station 8 is connected to each jack through an independent oil supply line 12. Each oil supply line is equipped with an electro-hydraulic servo valve 11. The flow rate specification of each electro-hydraulic servo valve 11 is selected independently according to the target pressure and lifting speed of the corresponding jack. The PLC controller 7 is electrically connected to each pressure sensor 9, each displacement sensor 10 and each electro-hydraulic servo valve 11 respectively. The PLC controller 7 has pre-stored the design pressure data of each fulcrum. The PLC controller 7 is configured to execute any of the control methods in the above embodiments with the design pressure data of each fulcrum as the independent control target of each jack. The host industrial control computer is communicatively connected to the PLC controller 7 and stores the finite element analysis model of the large-span steel-concrete composite beam. It is used to receive the measured data transmitted by the PLC controller 7 and perform finite element dynamic inversion calculations.

[0068] Specifically, refer to Figures 3 to 5Each lifting unit includes a jack, a pressure sensor 9 and a displacement sensor 10 independently mounted on the jack; the jack can be a hydraulic jack or a screw jack; the pressure sensor 9 can be a strain gauge pressure sensor or a piezoresistive pressure sensor, and the displacement sensor 10 can be a grating displacement sensor or a magnetostrictive displacement sensor; the hydraulic power station 8 is connected to each jack through an independent oil supply line 12, and each oil supply line is equipped with an electro-hydraulic servo valve 11; the electro-hydraulic servo valve 11 can be a direct-acting electro-hydraulic servo valve 11 with fast response speed, or it can be a pilot-operated electro-hydraulic servo valve 11, which can withstand larger flow rates and pressures.

[0069] Reference Figures 3 to 5 The PLC controller 7 is electrically connected to each pressure sensor 9, each displacement sensor 10 and each electro-hydraulic servo valve 11, and is configured to perform control steps such as synchronous different force control, spatial attitude closed-loop control, finite element analysis model inversion, and contact state diagnosis.

[0070] The implementation principle of this application embodiment is as follows: Through the coordinated work of each component, the system can accurately control the lifting force and displacement of each jack, realize synchronous lifting with different forces, and ensure the safety and stability of beam 1 during the replacement of the support of the large-span steel-concrete composite beam. Compared with the traditional lifting system, it improves the control accuracy and construction safety.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of this application.

Claims

1. A method for synchronous jacking under different forces for replacing supports of large-span steel-concrete composite beams, characterized in that, Includes the following steps: The beam (1) is lifted using the first jack group (5). The first jack group (5) is connected to the PLC controller (7). During the lifting process, the design pressure data of each support point is used as the independent pressure control target of the corresponding jack. The design pressure data of each support point is used as the main control parameter, and the vertical displacement difference between each point is used as the safety interlock parameter for double closed-loop control. This enables each support point to be lifted synchronously but differently to the preset height according to its own design reaction force. After jacking up, the old support pad stone is removed (3); Install replacement steel support (13); After the replacement steel support (13) is in place, the support reaction force is measured by replacing it with a jack. The measured support reaction force data is reported to the design unit for confirmation. The jacking is carried out and locked according to the confirmed final reaction force value. Pour new support pad stones (4) and lower the main beam back down.

2. The synchronous different-force jacking method for replacing supports of large-span steel-concrete composite beams according to claim 1, characterized in that, The dual closed-loop interlock control includes: A pressure sensor (9) and a displacement sensor (10) are independently installed on the jack at each lifting point. The pressure sensor (9) is used to monitor the actual lifting force value at the point in real time, and the displacement sensor (10) is used to monitor the actual lifting displacement at the point in real time. The design pressure data of each fulcrum is input into the PLC controller (7) as the independent control target of each jack; During the lifting process, the PLC controller (7) receives the feedback values ​​of each pressure sensor (9) in real time and compares them with the corresponding design pressure data. By independently controlling the oil intake of each jack, the actual lifting force value at each point approaches and stabilizes at the corresponding design pressure data. At the same time, the PLC controller (7) receives the feedback values ​​of each displacement sensor (10) in real time, calculates the displacement difference between each point, and when the calculated displacement difference exceeds the preset threshold of displacement difference, it suspends the adjustment of pressure deviation or limits the lifting speed of the point where the displacement difference exceeds the limit until the displacement difference returns to the safe range.

3. The synchronous different-force jacking method for replacing supports of large-span steel-concrete composite beams according to claim 2, characterized in that, The determination of the preset threshold for displacement difference is based on the following: the limit allowable opening displacement of the steel-concrete joint surface of the large-span steel-concrete composite beam is 2.5mm, the preset threshold for displacement difference is set to 2mm, and the safety reserve factor is 0.

8.

4. The synchronous different-force jacking method for replacing supports of large-span steel-concrete composite beams according to claim 2, characterized in that, The lifting speed v, the single scan cycle t of the PLC controller (7) and the preset threshold h of the displacement difference satisfy the following safety coordination constraint: v×t≤h; Wherein, v×t represents the displacement increment generated by any jack in a single scanning cycle. The constraint ensures that the maximum displacement increment of any point before the PLC controller (7) detects the displacement deviation does not exceed the preset threshold of displacement difference, thus reserving a safety margin for system intervention. The lifting speed v is 1 mm / min, the lifting height of each level is 5 mm, and the preset threshold of displacement difference h is 2 mm.

5. The synchronous different-force jacking method for replacing supports of large-span steel-concrete composite beams according to claim 2, characterized in that, It also includes spatial attitude closed-loop control: based on the real-time feedback values ​​of each displacement sensor (10), the longitudinal slope change and transverse slope change of the beam (1) are obtained by spatial coordinate calculation; when the longitudinal slope change or transverse slope change exceeds the design allowable value, the PLC controller (7) automatically calculates the compensation lifting amount of each jack, and prioritizes the jacks located in the deformation sensitive area of ​​the beam (1) to make slight adjustments until the slope of the beam (1) is restored to the design allowable range; the deformation sensitive area is the area of ​​sudden change in stiffness or stress concentration of the beam (1) determined according to the finite element analysis model.

6. The synchronous different-force jacking method for replacing supports of large-span steel-concrete composite beams according to claim 2, characterized in that, The PLC controller (7) is connected to a host industrial control computer, which stores a finite element analysis model of a large-span steel-concrete composite beam. During the jacking process, the host industrial control computer receives the measured displacement data transmitted by the PLC controller (7) in real time and inputs it into the finite element analysis model to dynamically invert the current stiffness distribution state of the beam (1). When the deviation between the inverted stiffness and the design stiffness exceeds the preset threshold of stiffness deviation, the host industrial control computer sends the corrected target pressure data of each jack to the PLC controller (7), and the PLC controller (7) updates the control target of each jack accordingly.

7. The synchronous different-force jacking method for replacing supports of large-span steel-concrete composite beams according to claim 2, characterized in that, It also includes an independent contact state diagnosis step: During the dual closed-loop interlock control process, the PLC controller (7) synchronously establishes the force-displacement relationship curve of each lifting point and compares it with the pre-stored theoretical force-displacement curve. When the slope deviation of the two exceeds the preset threshold of the deviation slope, the system records the abnormal contact state information of the point where the slope deviation occurs, and automatically adjusts the lifting speed parameters of the point where the slope deviation occurs after the current level lifting is completed and before the next level lifting is started.

8. The synchronous different-force jacking method for replacing supports of large-span steel-concrete composite beams according to claim 1, characterized in that, The removal of the old bearing pad stone (3) adopts a hydraulic crushing process, specifically including: while the first jack group (5) is kept in the lifting and locking state, the PLC controller (7) continuously monitors the pressure change of each jack, uses hydraulic crushing equipment, adjusts the pressure to 280~320MPa, and crushes the concrete pad stone with a grade greater than C45 in layers, with the thickness of each layer controlled at 2~4cm. Before crushing, a rebar detector is used to find out the position of the pre-embedded rebar and avoid it; after each layer is crushed, the PLC controller (7) checks the deviation between the pressure value and the locking value of each jack, and when the deviation exceeds ±3% of the locking pressure, the crushing operation is suspended.

9. The synchronous different-force jacking method for replacing supports of large-span steel-concrete composite beams according to claim 1, characterized in that, The actual measurement of the support reaction force was carried out after the steel support was replaced and installed, and specifically included: With the replacement steel support (13) already installed and in place, the first jack group (5) is kept in the lifting and bearing state of the beam (1) and locked, so that the load of the beam (1) is transferred through the replacement steel support (13). A second jack group (6) is placed on the top surface of the same cover beam (2) next to the first jack group (5). The second jack group (6) is connected to the PLC controller (7). The total rated lifting capacity of the second jack group (6) is greater than the total rated lifting capacity of the first jack group (5). Lift the second jack group (6) so that the movable end of the second jack group (6) is in close contact with the steel plate under the replacement steel support (13) but has not yet borne the load of the beam (1); Slowly unload the first jack group (5) and make the movable end of the first jack group (5) detach from the bottom of the beam, and smoothly transfer the weight of the beam (1) to the second jack group (6), maintain pressure and record the first measured reaction force value; The measured data were compiled into a support reaction force calculation report and submitted to the design unit for confirmation. Based on feedback from the design unit, several trial jackings and data verifications were conducted until the design unit confirmed the final reaction force value. Perform a complete jacking operation based on the final reaction force value and lock the second jack group (6).

10. A synchronous jacking system for replacing supports of large-span steel-concrete composite beams under different forces, characterized in that, The synchronous jacking method for replacing the supports of a large-span steel-concrete composite beam as described in any one of claims 1 to 9 includes: Multiple lifting units, each lifting unit includes a jack, a pressure sensor (9) and a displacement sensor (10) independently set on the jack, and the rated lifting force of the jack of each lifting unit is independently configured according to the design reaction force of the support point. The hydraulic power station (8) is connected to each jack through an independent oil supply line (12). Each oil supply line is equipped with an electro-hydraulic servo valve (11). The flow rate specification of each electro-hydraulic servo valve (11) is selected independently according to the target pressure and lifting speed of the corresponding jack. The PLC controller (7) is electrically connected to each pressure sensor (9), each displacement sensor (10) and each electro-hydraulic servo valve (11). The PLC controller (7) has pre-stored the design pressure data of each fulcrum. The PLC controller (7) is configured to execute the control method according to any one of claims 2 to 9 with the design pressure data of each fulcrum as the independent control target of each jack. The host industrial control computer is connected to the PLC controller (7) and stores the finite element analysis model of the large-span steel-concrete composite beam. It is used to receive the measured data transmitted by the PLC controller (7) and perform finite element dynamic inversion calculation.

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