Construction method of three-tensioning of cable stays for super-large bridge towers

Abstract

This invention belongs to the field of bridge construction technology, specifically relating to a three-stage tensioning construction method for cable-stayed bridge towers. The cable-stayed bridge's cable installation and tensioning is divided into three parts: the near-tower section, the middle tower section, and the far-tower section. The cable-stayed sections of the near and middle tower sections are installed sequentially, using high-pressure hoses to connect the tower-end control oil pump and intelligent tensioning jacks, and then performing graded symmetrical tensioning on the cables of these sections. Based on cable force and linearity test results, a synchronous tensioning control center and oil pump system are used to synchronously adjust the cables of the near and middle tower sections. The beam and cable-stayed sections of the far-tower section are then installed, using high-pressure hoses to connect the tower-end control oil pump and intelligent tensioning jacks, followed by graded symmetrical tensioning of the cables. Based on cable force and linearity test results, the three sections of the cable-stayed bridge—near, middle, and far—are synchronously adjusted to ensure cable force requirements and bridge linearity, thus reducing linearity errors and shrinkage.

Description

Technical Field

[0001] This invention belongs to the field of bridge construction technology, specifically relating to a method for three-tensioning construction of cable stays for super-large bridge towers. Background Technology

[0002] Cable-stayed bridges mainly consist of pylons, main girders, and stay cables. Pylon styles include A-type, inverted Y-type, H-type, and single-column, and materials can be steel or concrete. Stay cables can be arranged in a single-plane, parallel double-plane, or inclined-plane configuration. The history of cable-stayed bridges can be traced back to the Strømsund Bridge in Sweden, built in 1956, with a main span of 182.6 meters. After half a century of development, cable-stayed bridge technology has made tremendous progress, especially since the 1990s, with many famous cable-stayed bridges built around the world, such as the Sutong Bridge between Nantong and Suzhou in Jiangsu Province, China (main span 1088 meters), the Normandy Cable-Stayed Bridge in France (main span 856 meters), the Nanjing Yangtze River Second Bridge South Branch Steel Box Girder Cable-Stayed Bridge (main span 628 meters), and the Tatara Bridge in Japan, built in 1999 (main span 890 meters).

[0003] Cable-stayed bridge construction technology is an advanced technique applied to the construction of cable-stayed bridges. Its emergence and development were driven by the modern societal demand for both safety and aesthetics in bridge construction. This technology primarily uses stay cables to transfer the bridge load to the towers or piers, allowing the bridge components to fully utilize their mechanical properties. The advent of cable-stayed bridge construction technology has solved some of the challenges in traditional bridge construction, making the construction of long-span bridges possible. With advancements in science and technology and the continuous accumulation of engineering practice, cable-stayed bridge construction technology continues to develop and improve, providing more reliable technical support for modern bridge construction.

[0004] Currently, cable-stayed bridges are increasingly widely used. Cable-stayed bridges are multi-dimensionally statically indeterminate structures, making the stress conditions of the beams, towers, and cables quite complex. During the tensioning process of the stay cables, an important influencing factor is unbalanced force, which significantly impacts construction. Unbalanced forces mainly arise from the influence of stay cables tensioned later in the same or different layers on the cable forces of those tensioned earlier. When the unbalanced force is too large, it affects the stress conditions of the main bridge structure and increases the difficulty of controlling the overall bridge alignment. The generation of unbalanced forces is particularly pronounced during the tensioning process of multi-plane, multi-layer cable-stayed bridges.

[0005] Secondly, cable stays may experience shrinkage during use, which can affect their tensioning effect and the overall performance of the bridge. Furthermore, existing anti-shrinkage technology for cable stays cannot be combined with an intelligent tensioning control system to prevent shrinkage as soon as the cable stops.

[0006] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0007] To address the aforementioned problems in the existing technology, this invention provides a method for the three-tensioning construction of cable-stayed towers for extra-large bridges.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A method for constructing a three-tensioned cable-stayed tower for a super-large bridge includes the following steps: installing the beams and cables in the near-tower, middle-tower, and far-tower sections; and, based on the cable force and linearity test results, synchronously adjusting the cables of the three sections to ensure cable force requirements and bridge linearity.

[0010] Furthermore, the steps are divided into the following sub-steps:

[0011] S1: The installation and tensioning of the cable-stayed bridge's stay cables are divided into three parts: the near tower section, the middle tower section, and the far tower section;

[0012] S2: Install the stay cables near the tower. After the stay cables are installed, number and match the data acquisition devices of the intelligent tensioning jacks, tower end control oil pumps and synchronous tensioning control center. Then, perform graded symmetrical tensioning on the stay cables near the tower.

[0013] S3: Install the beams and stay cables of the middle tower section of the bridge. Use high-pressure hoses to connect the tower end control oil pump and intelligent tensioning jacks, and then perform graded symmetrical tensioning of the stay cables.

[0014] S4: After the installation and tensioning of the stay cables in the middle tower section, bridge cable force and linearity tests are carried out in the near tower section and the middle tower section. At the same time, a connection is established between the synchronous tensioning control center, the tower end control oil pump and the intelligent tensioning jack.

[0015] S5: Based on the cable tension and linearity test results, use the synchronous tensioning control center and control oil pump system to synchronously adjust the stay cables in the near-tower and middle-tower sections to ensure cable tension requirements and bridge linearity;

[0016] S6: After the near-tower section and the middle tower section are tensioned and adjusted synchronously, the same construction process as S2 is used to install the beam and stay cables of the far tower section. Then, the stay cables are tensioned in stages and symmetrically after connecting the tower end control oil pump and the intelligent tensioning jack with high-pressure hoses.

[0017] S7: After the last pair of stay cables is installed and tensioned, the same construction process as S4 is used to begin the overall bridge cable force detection, linearity detection and establishment of the "control center-oil pump-jack" system for the near tower section, middle tower section and far tower section.

[0018] S8: Using the same construction process as S5, based on the cable tension and linearity test results, the cable stays of the three sections near the tower, middle tower, and far tower are adjusted synchronously to ensure cable tension requirements and bridge linearity.

[0019] S9: Complete the tensioning of the stay cables for the entire bridge.

[0020] Furthermore, in S1, the installation and fixing of stay cables 1 to 3 and the beam are set as the near-tower section, and the remaining stay cables and beams are divided equally and set as the middle tower section and the far tower section respectively, and numbered according to the installation sequence.

[0021] Furthermore, the graded symmetrical tensioning of the stay cables in S2 includes the following sub-steps:

[0022] S21: Install a control oil pump, establish a "jack-oil pump" system, and connect the system to a computer for real-time recording. Control the tension force through "oil pressure-force value".

[0023] S22: After the stay cables at the beam end are anchored, the tower end is tensioned. The four stay cables in the same group are tensioned synchronously and symmetrically. The tensioning adopts dual control of tension force and elongation, with tension control force as the main factor. The graded tensioning program is: 0-0.2σ-0.5σ-0.7σ-1σ.

[0024] S23: During the cable tensioning construction process, the tower displacement and the main beam elevation are monitored simultaneously.

[0025] Furthermore, the overall synchronous tensioning of the stay cables in S5 includes the following sub-steps:

[0026] S51: Install and debug on-site equipment. After the cable stays are tensioned in stages, establish a synchronous tensioning system with control oil pumps, synchronous tensioning control center and intelligent tensioning jacks based on the bridge inspection results.

[0027] S52: Pre-tension each cable to eliminate slack and initial deformation inside the cable. Based on real-time monitoring data, make preliminary adjustments to the cable to bring it close to the design tension.

[0028] S53: Each stay cable is tensioned gradually until the designed tension is reached. During the tensioning process, the changes in cable tension are continuously monitored, and the tensioning speed and tension are adjusted as needed. For stay cables with excessive tension, appropriate cable release operations are performed to ensure that the tension is within the design range.

[0029] S54: Verify the tensioning data controlled by the central control computer of the on-site synchronous tensioning control center with the data of the intelligent tensioning jack hydraulic equipment to ensure that the two data are consistent;

[0030] S55: Perform benchmark calibration of instruments and equipment to ensure that all equipment is in normal working condition, and record the displacement of the beams on both sides of the tower and the longitudinal displacement of the tower.

[0031] S56: Based on the computer control terminal and design scheme, determine the influencing factors, and then analyze the influencing factors to develop a fine-tuning scheme for the overall synchronous tensioning of the cable-stayed cable.

[0032] S57: After the final bridge cable tension is in place, on-site tensioning and observation are carried out for 24 hours. The theoretical calculation and analysis are performed to analyze the deviation between the final on-site results and the predicted values. When the deviation is within the allowable error range, the entire tensioning process is considered to be over. The final tensioning report is recorded and written.

[0033] Furthermore, it includes an intelligent tensioning jack, which is installed on the beam and used for tensioning the stay cables; the intelligent tensioning jack includes:

[0034] An outer cylinder and a piston assembly, wherein the piston assembly is located in the oil chamber of the outer cylinder;

[0035] An anchor plate is located on one side of the extended end of the piston assembly and is used to fix the stay cable. The piston assembly drives the anchor plate to reciprocate.

[0036] The locking assembly is located on the outside of the outer cylinder body, with one end connected to the outer cylinder body and the other end connected to the anchor plate, and is used to lock the position of the anchor plate after it has been moved.

[0037] The intelligent tensioning jack includes an outer cylinder body, inside which is a piston rod and an oil chamber that can slide up and down. A displacement measuring plate is located at the upper end of the piston rod. A bidirectional limiting clamp is installed inside the displacement measuring plate. A pad is placed inside the displacement measuring plate, and an anchor plate is supported on the pad. The anchor plate is fixed to the steel strand by a unidirectional displacement clamp. The locking assembly includes an outer telescopic rod, an inner telescopic rod, a force-bearing nut, and an anchoring screw. The anchoring plate is fixed to the outer telescopic rod by the anchoring screw. An inner telescopic rod is located inside the outer telescopic rod. The outer telescopic rod has a sliding channel, and the upper part of the inner telescopic rod protrudes outward from the sliding channel, preventing the inner telescopic rod from detaching from the outer telescopic rod. The inner telescopic rod has threads and a force-bearing nut. A linear displacement sensor is connected to the outside of the displacement measuring plate. An oil pressure sensor is connected to the hole inside the oil chamber. An oil chamber bottom cover is located at the lower end of the oil chamber, and a jack base is located under the oil chamber bottom cover.

[0038] Furthermore, an oil pressure sensor is connected to the hole inside the oil chamber.

[0039] Furthermore, in step S53, by supplying oil into the oil chamber, the piston rod moves upward, causing the displacement measuring plate, gasket, and anchor plate at the upper end of the piston rod to move upward together. The displacement measuring plate has a bidirectional limiting clamp to fix the displacement measuring plate to the steel strand. As the steel strand moves, the displacement measuring plate has a gasket to protect the displacement measuring plate and the anchor plate. The anchor plate has a unidirectional displacement clamp to restrict the steel strand to move only upward.

[0040] Furthermore, when the piston rod moves upward, the steel strand is tensioned, and the anchor plate drives the outer telescopic rod to move upward together through the anchor screw. When the anchor length is reached, the piston rod of the intelligent tensioning jack stops moving upward. By rotating the force-bearing screw nut upward, the lower end of the outer telescopic rod is reached, providing a force point to the outer telescopic rod. The anchor plate is limited by the force-bearing screw nut and the anchor screw.

[0041] The beneficial effects of this invention are as follows:

[0042] (1) When tensioning in stages, by starting from the bottom of the tower and gradually tensioning towards the middle and top of the tower, it can be ensured that the tower maintains sufficient stability at each stage. This gradual stabilization construction method helps to reduce the risk of structural deformation or stress concentration caused by one-time tensioning.

[0043] (2) By applying the intelligent synchronous tensioning system and combining it with the three-tensioning construction process, the construction cycle was significantly shortened and the construction quality was improved. This not only enabled the data on the hydraulic pressure of the intelligent tensioning jack and the tension of the stay cable, but also combined anti-retraction with intelligent tensioning to prevent the anchor plates from losing tension and causing the stay cable to retract after the stay cable tensioning is completed. Attached Figure Description

[0044] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0045] Figure 1 This is a flowchart illustrating the overall tensioning process of the present invention.

[0046] Figure 2 This is a flowchart of the synchronous tensioning process of the present invention;

[0047] Figure 3 This is a flowchart of the graded symmetrical tensioning process for the stay cables of the present invention;

[0048] Figure 4 This is a schematic diagram of the bridge near the tower section of the present invention;

[0049] Figure 5 This is a schematic diagram of the near-tower and middle tower sections of the bridge according to the present invention;

[0050] Figure 6 This is a schematic diagram of the near-tower section, middle tower section, and far-tower section of the bridge according to the present invention;

[0051] Figure 7 This is an example diagram of the intelligent synchronous tensioning construction layout of the present invention;

[0052] Figure 8 This is a schematic diagram of the graded tensioning construction of the present invention;

[0053] Figure 9 This is a schematic diagram of the intelligent tensioning jack device of the present invention.

[0054] Explanation of reference numerals in the attached diagram: 1. Synchronous tensioning control center; 2. Control oil pump; 3. Intelligent tensioning jack; 31. Piston rod; 32. Outer cylinder; 33. Anchor plate; 34. Outer telescopic rod; 35. Inner telescopic rod; 36. Force-bearing nut; 37. Anchor bolt; 38. Displacement measuring plate; 39. Linear displacement sensor; 310. Hydraulic pressure sensor; 311. Oil chamber bottom cover; 312. Jack base; 313. Unidirectional displacement clamp; 314. Pad plate; 315. Oil chamber; 316. Bidirectional limit clamp; 4. Stay cable; 5. Beam; 6. Tower; 7. High-pressure hose; 8. Near-tower section; 9. Middle-tower section; 10. Far-tower section. Detailed Implementation

[0055] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided.

[0056] like Figure 1-9 As shown, the present invention discloses a method for three-tensioning construction of cable-stayed towers for extra-large bridges, the method comprising the following steps:

[0057] S1: The cable-stayed bridge's cable-stayed cable 4 is installed and tensioned in three parts: the near tower section 8, the middle tower section 9, and the far tower section 10;

[0058] S2: Install the stay cables 4 of the near-tower section 8. After the stay cables 4 are installed, number and match the data acquisition devices of the intelligent tensioning jacks 3, tower end control oil pumps 2 and synchronous tensioning control center 1. Then, perform graded symmetrical tensioning on the stay cables 4 of the near-tower section 8.

[0059] S3: Install the beam 5 of the bridge body of the middle tower section 9 and the stay cable 4. Use high pressure hose 7 to connect the tower end control oil pump 2 and intelligent tensioning jack 3, and then perform graded symmetrical tensioning of the stay cable 4.

[0060] S4: After the cable 4 of the middle tower section 9 is installed and tensioned, the cable force and linearity of the bridge are tested in the near tower section 8 and the middle tower section 9. At the same time, the connection between the synchronous tensioning control center 1, the tower end control oil pump 2 and the intelligent tensioning jack 3 is established.

[0061] S5: Based on the cable tension and linearity test results, use the synchronous tension control center 1 and control oil pump 2 system to synchronously adjust the stay cables 4 of the near tower section 8 and the middle tower section 9 to ensure cable tension requirements and bridge linearity;

[0062] S6: After the near tower section 8 and the middle tower section 9 are tensioned and adjusted synchronously, the same construction process as S2 is used to install the beam 5 and the stay cable 4 of the far tower section 10. Then, the high pressure hose 7 is used to connect the tower end control oil pump 2 and the intelligent tensioning jack 3 to the stay cable 4 for graded symmetrical tensioning.

[0063] S7: After the last pair of stay cables 4 are installed and tensioned, the same construction process as S4 is used to start the overall bridge cable force detection, linearity detection and the establishment of the "control center-oil pump-jack" system for near tower section 8, middle tower section 9 and far tower section 10.

[0064] S8: Using the same construction process as S5, based on the cable force test and linearity test results, synchronous cable adjustment is carried out on the three sections of the cable stay 4: near tower section 8, middle tower section 9, and far tower section 10, to ensure cable force requirements and bridge linearity.

[0065] S9: Complete the tensioning of all four stay cables of the bridge.

[0066] Specifically, two tower-end control oil pumps 2 need to be placed on both sides of the tower and connected to the tower-end intelligent tensioning jacks 3 via high-pressure hoses 7 to control the tensioning of stay cables 4, numbers 1 to 3 on the corresponding sides. When the tensioning of cable number 4 is reached, three more pairs of control oil pumps 2 are placed on both sides of the tower and connected to the tower-end intelligent tensioning jacks 3 via high-pressure hoses 7 to control the tensioning of stay cables 4 to 5, 6 to 7, and 8 on the corresponding sides. At the same time, the control oil pumps 2 installed this time need to cooperate with the control oil pumps 2 installed the first time to control the tensioning of stay cables 4, numbers 8 near the tower and 9 in the middle tower section. To determine the cable tension and reduce linearity issues, five pairs of control oil pumps 2 were placed on both sides of the tower. At this point, each end of the tower has nine control oil pumps 2. The five pairs of control oil pumps 2 were used to control the tensioning of the stay cables 4 of No. 9, 10, 11, 12, 13, 14, and 15 on the corresponding sides. At the same time, the five pairs of control oil pumps 2 set up this time need to work with the control oil pumps 2 set up in the first and second sets to determine the cable tension of the stay cables 4 of the near tower section 8, the middle tower section 9, and the far tower section 10, and reduce linearity issues. During intelligent tensioning, the displacement sensors and hydraulic sensors 310 on the intelligent tensioning jacks 3 of each stay cable 4 transmit the mechanical data of the tension amount and the hydraulic pressure data of the intelligent tensioning jacks 3 to the control center. Then, based on the design values, mechanical data, and hydraulic pressure data, the staff issues tensioning or releasing commands to the corresponding tower end tensioning control pumps 2, gradually tensioning each stay cable 4 until the designed tension force is reached. During the tensioning process, changes in cable force are continuously monitored, and the tensioning speed and force are adjusted as needed. Once all stay cables 4 have reached or are close to the designed tension force, fine adjustments are made to ensure that the tension distribution of each stay cable 4 is uniform and meets design requirements. After adjustment, each stay cable 4 is anchored to fix its tension.

[0067] Bridge linearity testing refers to measuring the geometric parameters and structural morphology of a bridge, such as length, width, height, vertical elevation, lateral level, and curvature, to understand its actual condition and deformation. The main purpose of bridge linearity testing is to obtain geometric dimensions and structural morphology data to assess the bridge's current condition, monitor its deformation, and predict potential destructive deformation. This data provides crucial information for bridge design optimization, construction control, maintenance and reinforcement, and safety assessment. Meanwhile, the main purpose of bridge cable stress testing is to monitor and evaluate the stress state of the bridge's cable structures (such as stay cables and suspension cables), ensuring that the cable stress is within the design limits, thereby guaranteeing the overall stability and safety of the bridge.

[0068] By combining the intelligent tensioning jack 3 with the control center, not only is the tensioning process automated and precisely controlled, but the controllability of construction quality is also improved through real-time monitoring and data analysis.

[0069] By tensioning the tower in stages, starting from the bottom and gradually working towards the middle and top, sufficient stability can be maintained at each stage. This gradual stabilization method helps reduce the risk of structural deformation or stress concentration caused by a single tensioning operation.

[0070] The advantages of the first stage are mainly concentrated in the accuracy of the initial tensioning and the stability of the tower base. Through the intelligent synchronous tensioning system, the tension force and tensioning sequence can be precisely controlled in the first stage. This precision ensures the stability and uniform stress distribution of the tower base during the initial tensioning process.

[0071] The second phase focuses on enhancing the overall stability of the tower and optimizing cable force distribution through increased tensioning. Building upon the stability of the tower's base ensured by the first tensioning phase, the second phase further enhances the overall stability of the tower by increasing tensioning in the middle section. This gradual stabilization construction method helps reduce the risk of structural deformation and stress concentration.

[0072] The third stage, as the final stage, has the advantages of ensuring the ultimate stability of the tower structure, comprehensively controlling construction quality, and implementing comprehensive safety protection measures. Through the final tensioning of the tower top and comprehensive control of the tensioning process, the third stage achieves the final optimization and adjustment of cable forces, ensuring the stability and safety of the tower during long-term use.

[0073] The application of an intelligent synchronous tensioning system and the combined implementation of three-stage tensioning construction techniques significantly shortened the construction cycle and improved construction quality. This not only digitized the hydraulic pressure of the intelligent tensioning jack 3 and the tensioning amount of the stay cable 4, but also combined anti-retraction with intelligent tensioning to prevent the anchor plate 33 from losing tension and causing the stay cable 4 to retract after tensioning is completed.

[0074] In S1, the installation and fixing of cable stays 4 from No. 1 to No. 3 and beam 5 are set as near-tower section 8. The remaining cable stays 4 and beam 5 are divided equally and set as middle tower section 9 and far tower section 10 respectively, and numbered according to the installation sequence.

[0075] The four-stage symmetrical tensioning of the stay cables in S2 includes the following sub-steps:

[0076] S21: Install control oil pump 2, establish a "jack-oil pump" system and connect the system to the computer for real-time recording, and control the tension force through "oil pressure-force value";

[0077] S22: After the stay cables 4 at the beam end are anchored, the tower end is tensioned. The four stay cables 4 in the same group are tensioned synchronously and symmetrically. The tensioning adopts dual control of tension force and elongation, with tension control force as the main factor. The graded tensioning program is: 0-0.2σ-0.5σ-0.7σ-1σ.

[0078] S23: During the tensioning process of the four stay cables, the displacement of the cable tower and the monitoring elevation of the main beam are monitored simultaneously.

[0079] The overall synchronous tensioning of cable 4 in S5 includes the following sub-steps:

[0080] S51: Install and debug the on-site equipment. After the fourth stage of tensioning of the stay cables, establish a synchronous tensioning system consisting of control oil pump 2, synchronous tensioning control center 1, and intelligent tensioning jack 3, based on the bridge inspection results.

[0081] S52: Pre-tension each stay cable 4 to eliminate slack and initial deformation inside the cable. Based on real-time monitoring data, make preliminary adjustments to the stay cable 4 to bring it close to the design tension.

[0082] S53: Each stay cable 4 is tensioned gradually until the designed tension force is reached. During the tensioning process, the change in cable force is continuously monitored, and the tensioning speed and tension force are adjusted as needed. For stay cables 4 with excessive tension, appropriate cable release operations are performed to ensure that the tension is within the design range.

[0083] S54: Verify the tensioning data controlled by the central control computer of the on-site synchronous tensioning control center 1 with the data of the intelligent tensioning jack 3 hydraulic equipment to ensure that the two data are consistent;

[0084] S55: Perform benchmark calibration of instruments and equipment to ensure that all equipment is in normal working condition, and record the displacement of the beams 5 on both sides of the tower body 6 and the longitudinal displacement of the tower body 6.

[0085] S56: Based on the computer control terminal and design scheme, determine the influencing factors, and then analyze the influencing factors to develop a fine-tuning scheme for the overall synchronous tensioning of cable 4.

[0086] S57: After the final bridge cable tension is in place, on-site tensioning and observation are carried out for 24 hours. The theoretical calculation and analysis are performed to analyze the deviation between the final on-site results and the predicted values. When the deviation is within the allowable error range, the entire tensioning process is considered to be over. The final tensioning report is recorded and written.

[0087] Specifically, σ stands for Control Stress, a key parameter in the prestressing tensioning process. Control Stress refers to the target stress value that the prestressing tendons must reach during tensioning to ensure that the prestressed member functions properly under design loads and meets design requirements.

[0088] Specifically, the meanings of each step in the tensioning procedure are as follows:

[0089] 0: Indicates the initial state before tensioning begins, that is, the prestressed tendon is not subjected to any tension stress.

[0090] 0.2σ: This indicates that the prestressing tendon has been tensioned to 20% of the control stress. At this stage, the prestressing tendon is usually pre-tensioned to check whether the tensioning equipment and the condition of the prestressing tendon are normal.

[0091] 0.5σ: This indicates that the prestressing tendons are further tensioned to 50% of the control stress. During this stage, the tensioning stress is continued to increase, while the deformation of the prestressing tendons and the member is observed.

[0092] 0.7σ: This indicates that the prestressing tendons are tensioned to 70% of the control stress. At this point, the deformation of the prestressing tendons and the member will increase further, but it still needs to be kept within a controllable range.

[0093] 1σ: This indicates that the prestressing tendon has been tensioned to 100% of the control stress, i.e., the target tension stress value has been reached. At this stage, it is necessary to maintain the tension stress for a period of time (e.g., hold the load for a few minutes) to ensure that the prestressing tendon and the component are fully stressed and reach a stable state.

[0094] Furthermore, the intelligent tensioning jack 3 in S2 includes an outer cylinder 32, within which a piston rod 31 and an oil chamber 315 are slidable up and down. A displacement measuring plate 38 is located at the upper end of the piston rod 31, and a bidirectional limiting clamp 316 is installed within the displacement measuring plate 38. A pad 314 is placed within the displacement measuring plate 38, and an anchor plate 33 is supported on the pad 314. The anchor plate 33 fixes the steel strand through a unidirectional displacement clamp 313, and an external telescopic rod 34 is fixed to the anchor plate 33 by anchor bolts 37. The rod 34 has an inner telescopic rod 35 inside, and the outer telescopic rod 34 has a sliding channel. The upper part of the inner telescopic rod 35 protrudes outward from the sliding channel, so that the inner telescopic rod 35 cannot be separated from the outer telescopic rod 34. The inner telescopic rod 35 has threads and a force-bearing nut 36 is provided on the inner telescopic rod 35. The displacement measuring plate 38 is externally connected to a linear displacement sensor 39. The oil chamber 315 has an oil pressure sensor 310 connected to the inner hole. The lower end of the oil chamber 315 has an oil chamber bottom cover 311, and a jack base 312 is provided under the oil chamber bottom cover 311.

[0095] During the tensioning stage, oil is supplied into the oil chamber 315, causing the piston rod 31 to move upward. This causes the upper displacement measuring plate 38, gasket, and anchor plate 33 of the piston rod 31 to move upward together. The displacement measuring plate 38 has a bidirectional limiting clamp 316 that fixes the displacement measuring plate 38 to the steel strand. As the steel strand moves, the displacement measuring plate 38 has a gasket to protect the displacement measuring plate 38 and the anchor plate 33. The anchor plate 33 has a unidirectional displacement clamp 313 that restricts the steel strand to move only upward. When the piston rod 31 moves upward, the steel strand is tensioned. At the same time, the anchor plate 33 drives the outer telescopic rod 34 to move upward together through the anchor screw 37. The outer telescopic rod 34 contains an inner telescopic rod 35 and has a sliding channel. The upper part of the inner telescopic rod 35 protrudes outward from the sliding channel, so that the inner telescopic rod 35 cannot detach from the outer telescopic rod 34. When the anchoring length is reached, the piston rod 31 of the intelligent tensioning jack 3 stops moving upward. At this time, the force-bearing nut 36 needs to be rotated upward to reach the lower end of the outer telescopic rod 34 and provide a force point to the outer telescopic rod 34. At this time, the anchor plate 33 will not move downward due to the force-bearing nut 36, and will not move upward due to the anchor screw 37. This prevents the anchor plate 33 from losing tension and causing the stay cable 4 to retract after the intelligent tensioning jack 3 finishes tensioning. The intelligent features of the intelligent tensioning jack 3 are reflected in the following: A displacement measuring plate 38 is fixed to the steel strand, and a linear displacement sensor 39 is connected to the outside of the displacement measuring plate 38. This allows for precise measurement of the tension length of the steel strand. If the stay cable 4 still has a slight amount of retraction, the steel strand will cause the displacement measuring plate 38 to move downwards. At this time, the linear displacement sensor 39 will immediately detect the slight displacement, providing a more accurate understanding of the tension of the stay cable 4 steel strand, thus facilitating the estimation of cable force changes. The oil chamber 315 has channels similar to the oil pressure sensor 310, allowing for a clearer understanding of the oil pressure value of the intelligent tensioning jack 3. The bottom of the intelligent tensioning jack 3 is equipped with an oil chamber bottom cover 311, facilitating maintenance in case of equipment failure. A jack base 312 is located under the oil chamber bottom cover 311, with a groove inside the base to facilitate fixing the intelligent tensioning jack 3 and to better bear the force while protecting the main body of the intelligent tensioning jack 3.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for constructing cable-stayed towers of extra-large bridges using a three-tensioning method, characterized in that: The construction method includes the following steps: installing the beams (5) and stay cables (4) of the near tower section (8), middle tower section (9) and far tower section (10); and simultaneously adjusting the stay cables (4) of the three sections of the near tower section (8), middle tower section (9) and far tower section (10) according to the cable force test and linearity test results to ensure the cable force requirements and bridge linearity. The steps are divided into the following sub-steps: S1: The cable stays (4) of the cable-stayed bridge are hung and tensioned in three parts: the near tower section (8), the middle tower section (9) and the far tower section (10). S2: Install the stay cables (4) of the near-tower section (8). After the stay cables (4) are installed, number and match the data acquisition devices of the intelligent tensioning jack (3), tower end control oil pump (2) and synchronous tensioning control center (1). Then, perform graded symmetrical tensioning on the stay cables (4) of the near-tower section (8). S3: Install the beam (5) of the middle tower section (9) bridge body and the stay cables (4), use high pressure hose (7) to connect the tower end control oil pump (2) and intelligent tensioning jack (3), and then perform graded symmetrical tensioning of the stay cables (4); S4: After the cable stays (4) of the middle tower section (9) are installed and tensioned, bridge cable force and linearity are tested in the near tower section (8) and the middle tower section (9). At the same time, the connection between the synchronous tensioning control center (1), the tower end control oil pump (2) and the intelligent tensioning jack (3) is established. S5: Based on the cable tension test and linearity test results, the synchronous tensioning control center (1) and control oil pump (2) system are used to synchronously adjust the stay cables (4) of the near tower section (8) and the middle tower section (9) to ensure the cable tension requirements and bridge linearity; S6: After the near tower section (8) and the middle tower section (9) are tensioned and adjusted synchronously, the same construction process as S2 is used to install the beam (5) and the stay cables (4) of the far tower section (10). Then, the high-pressure hose (7) is used to connect the tower end control oil pump (2) and the intelligent tensioning jack (3) and the stay cables (4) are tensioned in stages and symmetrically. S7: After the last pair of stay cables (4) are installed and tensioned, the same construction process as S4 is used to start the overall bridge cable force detection, linearity detection and the establishment of the "control center-oil pump-jack" system for the near tower section (8), middle tower section (9) and far tower section (10); S8: Using the same construction process as S5, based on the cable force test and linearity test results, the cable stays (4) of the three sections of the near tower section (8), middle tower section (9) and far tower section (10) are adjusted synchronously to ensure the cable force requirements and bridge linearity. S9: Complete the tensioning of the entire bridge's cable stays (4).

2. The method for three-tensioning construction of cable-stayed towers of extra-large bridges according to claim 1, characterized in that: In S1, the installation and fixing of the No. 1 to No. 3 stay cables (4) and beam (5) are set as the near tower section (8), and the remaining stay cables (4) and beam (5) are divided equally and set as the middle tower section (9) and the far tower section (10) respectively, and numbered according to the hanging order.

3. The method for three-tensioning construction of cable-stayed towers of extra-large bridges according to claim 1, characterized in that: The graded symmetrical tensioning of the stay cable (4) in S2 includes the following sub-steps: S21: Install control oil pump (2), establish "jack-oil pump" system and connect the system to the computer for real-time recording, and control the tension force through "oil pressure-force value"; S22: After the stay cables (4) at the beam end are anchored, the tower end is tensioned. The four stay cables (4) in the same group are tensioned synchronously and symmetrically. The tensioning adopts dual control of tension force and elongation, with tension control force as the main factor. The graded tensioning program is: 0-0.2σ-0.5σ-0.7σ-1σ. S23: During the tensioning process of the stay cable (4), the displacement of the tower body (6) and the elevation of the main beam are monitored synchronously.

4. The method for three-tensioning construction of cable-stayed towers of extra-large bridges according to claim 1, characterized in that: The overall synchronous tensioning of the stay cable (4) in S5 includes the following sub-steps: S51: Install and debug the on-site equipment. After the cable stays (4) are tensioned in stages, establish a synchronous tensioning system consisting of a control oil pump (2), a synchronous tensioning control center (1), and an intelligent tensioning jack (3) based on the bridge inspection results. S52: Pre-tension each cable (4) to eliminate slack and initial deformation inside the cable. Based on real-time monitoring data, make preliminary adjustments to the cable (4) to make it close to the design tension. S53: Each cable (4) is tensioned gradually until the designed tension is reached. During the tensioning process, the change of cable force is continuously monitored, and the tensioning speed and tension are adjusted as needed. For cable (4) with excessive tension, cable release is performed appropriately to ensure that the tension is within the design range. S54: Verify the tensioning data controlled by the central control computer of the on-site synchronous tensioning control center (1) with the data of the hydraulic equipment of the intelligent tensioning jack (3) to ensure that the two data are consistent; S55: Perform benchmark calibration of instruments and equipment to ensure that all equipment is in normal working condition, and record the displacement of the beams (5) on both sides of the tower body (6) and the longitudinal displacement of the tower body (6). S56: Based on the computer control terminal and design scheme, determine the influencing factors, and then analyze the influencing factors to make a fine-tuning scheme for the overall synchronous tensioning of the cable-stayed cable (4). S57: After the final bridge cable tension is in place, on-site tensioning and observation are carried out for 24 hours. The theoretical calculation and analysis are performed to analyze the deviation between the final on-site results and the predicted values. When the deviation is within the allowable error range, the entire tensioning process is considered to be over. The final tensioning report is recorded and written.

5. The method for three-tensioning construction of cable-stayed towers of extra-large bridges according to claim 4, characterized in that: The system includes an intelligent tensioning jack (3), which is mounted on the beam and used for tensioning the stay cables (4); the intelligent tensioning jack (3) includes: An outer cylinder (32) and a piston assembly, the piston assembly being located in an oil chamber (315) of the outer cylinder (32); Anchor plate (33) is located on one side of the extended end of the piston assembly and is used to fix the cable (4). The piston assembly drives the anchor plate (33) to reciprocate. The locking assembly is located on the outside of the outer cylinder (32), with one end connected to the outer cylinder (32) and the other end connected to the anchor plate (33), and is used to lock the position of the moved anchor plate (33).

6. The method for three-tensioning construction of cable-stayed towers of extra-large bridges according to claim 5, characterized in that: The intelligent tensioning jack (3) has an outer cylinder (32) containing a piston rod (31) that can slide up and down and an oil chamber (315). The upper end of the piston rod (31) has a displacement measuring plate (38). The displacement measuring plate (38) contains a bidirectional limiting clamp (316). A pad (314) is placed inside the displacement measuring plate (38). An anchor plate (33) is supported on the pad (314). The anchor plate (33) is fixed to the steel strand by a unidirectional displacement clamp (313). The positioning assembly includes an outer telescopic rod (34), an inner telescopic rod (35), a force-bearing nut (36), and an anchor bolt (37). The anchor plate (33) is fixed to the steel strand by a unidirectional displacement clamp (313). An anchor screw (37) fixes an outer telescopic rod (34), an inner telescopic rod (35) is inside the outer telescopic rod (34), the outer telescopic rod (34) has a sliding channel, the upper part of the inner telescopic rod (35) protrudes outward from the sliding channel, so that the inner telescopic rod (35) cannot be separated from the outer telescopic rod (34), the inner telescopic rod (35) has threads, and a force-bearing screw nut (36) is provided on the inner telescopic rod (35). The displacement measuring plate (38) is externally connected to a linear displacement sensor (39), the lower end of the oil cavity (315) has an oil cavity bottom cover (311), and a jack base (312) is provided under the oil cavity bottom cover (311).

7. The method for three-tensioning construction of cable-stayed towers of extra-large bridges according to claim 6, characterized in that: The oil chamber (315) is connected to an oil pressure sensor (310) through an inner hole.

8. The method for three-tensioning construction of cable-stayed towers of extra-large bridges according to claim 7, characterized in that: In step S53, by supplying oil into the oil chamber (315), the piston rod (31) moves upward, causing the displacement measuring plate (38), gasket, and anchor plate (33) at the upper end of the piston rod (31) to move upward together. The displacement measuring plate (38) has a bidirectional limiting clamp (316) inside, which fixes the displacement measuring plate (38) to the steel strand. As the steel strand moves, the displacement measuring plate (38) has a gasket inside, which is used to protect the displacement measuring plate (38) and the anchor plate (33). The anchor plate (33) has a unidirectional displacement clamp (313) inside, which restricts the steel strand to move only upward.

9. The method for three-tensioning construction of cable-stayed towers of extra-large bridges according to claim 8, characterized in that: When the piston rod (31) moves upward, the steel strand is tensioned. The anchor plate (33) drives the outer telescopic rod (34) to move upward together through the anchor screw (37). When the anchor length is reached, the piston rod (31) of the intelligent tensioning jack (3) stops moving upward. By rotating the force-bearing screw nut (36) upward, the lower end of the outer telescopic rod (34) is reached, and the force-bearing point of the outer telescopic rod (34) is given. The anchor plate (33) is limited by the force-bearing screw nut (36) and the anchor screw (37).

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