A pre-tensioning method bridge screw thread steel grading step-by-step synchronous tensioning device and tensioning method

Abstract

The application discloses a pre-tensioning method bridge threaded steel grading step-by-step synchronous tensioning device and tensioning method. The device comprises a steel beam, a jack assembly, a support assembly, a large counterforce frame, an anchoring assembly, a hydraulic pump station, an inclination sensor and a control assembly. The jack assembly comprises an upper jack unit and a lower jack unit. The piston rod ends of the upper jack unit and the lower jack unit are connected with the large counterforce frame through universal ball head structures. The hydraulic pump station is connected with the upper jack unit and the lower jack unit respectively. The inclination sensor is arranged on the side surface of the large counterforce frame. The control assembly is electrically connected with the hydraulic pump station and the inclination sensor respectively. The application can adapt to the tensioning working condition of the differentiated reinforcement on the upper and lower beam bodies, realize the collaborative synchronous tensioning of the jacks with different tonnages, and has the advantages of uniform tensioning stress, high displacement control precision, simple structure, economy and reliability, effectively reduced beam body deformation risk and improved overall quality of the bridge prestress construction.

Description

Technical Field

[0001] This invention relates to the field of bridge prestressing tensioning technology, and in particular to a graded and step-by-step synchronous tensioning device and method for pre-tensioned bridge threaded steel bars. Background Technology

[0002] In the construction of prestressed bridges using the pre-tensioning method, rebar, as a crucial prestressing reinforcement, directly affects the load-bearing capacity and durability of the overall bridge structure. Due to the characteristics of the design load distribution, the rebar in the upper half of the bridge beam is relatively sparse, while that in the lower half is more densely packed. This differential reinforcement arrangement leads to a significant difference in tension load. Current technologies, particularly conventional tensioning equipment and processes, struggle to effectively handle such load-differentiation, easily resulting in uneven prestress distribution. This can lead to asynchronous tensioning and beam deformation, among other chain-reaction quality issues, potentially impacting the bridge's service life and structural safety.

[0003] Traditional prestressed tensioning devices typically use a single type of jack for uniform tensioning, failing to adapt to the varying load differences between different parts of the beam. This results in over-tensioning in sparse upper areas or under-tensioning in dense lower areas. Furthermore, existing tensioning processes lack effective displacement synchronization control mechanisms and tilt angle monitoring and adjustment methods. If displacement errors accumulate due to factors such as strand retraction during tensioning, the jack piston will be subjected to tilting forces, accelerating seal wear, increasing the risk of oil leaks, and even causing rework, severely delaying the construction schedule. In addition, conventional hydraulic systems are complex, with multiple hydraulic pumps independently driven, increasing equipment costs and control difficulty, hindering efficient operation on construction sites.

[0004] Therefore, how to achieve coordinated and synchronous tensioning for different reinforcement conditions of the upper and lower parts of the beam, ensure uniform tensioning force and high displacement control accuracy, and at the same time simplify the hydraulic system configuration and reduce equipment costs has become an urgent technical problem to be solved in the field of bridge prestressed construction. Summary of the Invention

[0005] To address the technical problems of traditional prestressed tensioning devices being unable to adapt to different load variations at different parts of the beam, and the lack of effective displacement synchronization control mechanisms and tilt angle monitoring and adjustment methods in the tensioning process, this invention provides a graded and step-by-step synchronous tensioning device and method for pre-tensioned bridge rebar. This device can adapt to tensioning conditions with differentiated reinforcement at different parts of the beam, enabling synchronized tensioning with jacks of different tonnages. It ensures uniform tensioning force, high displacement control accuracy, simple structure, economy, and reliability, effectively reducing the risk of beam deformation and improving the overall quality of prestressed bridge construction.

[0006] This invention provides a staged and step-by-step synchronous tensioning device for pre-tensioned bridge rebar, comprising a steel beam, a jack assembly, a support assembly, a large reaction frame, an anchoring assembly, a hydraulic pump station, an inclination sensor, and a control assembly. The steel beam, the support assembly, and the large reaction frame are sequentially arranged at the ends of the bridge to be tensioned. The jack assembly is mounted on the support assembly and includes an upper jack unit and a lower jack unit. The piston rod ends of both the upper and lower jack units are provided with universal ball joint structures, which are respectively connected to the large reaction frame. The anchoring assembly is detachably connected to the large reaction frame. The hydraulic pump station is connected to both the upper and lower jack units. The inclination sensor is located on the side of the large reaction frame. The control assembly is electrically connected to both the hydraulic pump station and the inclination sensor.

[0007] In a preferred embodiment of the pre-tensioned bridge threaded steel graded and step-by-step synchronous tensioning device provided by the present invention, the universal ball head structure includes a ball socket seat disposed at the end of the piston rod and a force transmission plate disposed corresponding to the ball socket seat. A spherical head is provided on one side of the force transmission plate, and the spherical head is embedded in the ball socket seat to form a spherical mating connection.

[0008] In a preferred embodiment of the pre-tensioned bridge rebar graded and step-by-step synchronous tensioning device provided by the present invention, the support component includes a jack support frame and a jack pad, the jack component is disposed on the jack support frame, and the jack pad is disposed between the jack component and the steel beam.

[0009] In a preferred embodiment of the pre-tensioned bridge rebar graded and step-by-step synchronous tensioning device provided by the present invention, the anchoring assembly includes anchor plates and rebar nuts. The anchor plates are respectively disposed on the side of the jack assembly near the steel beam. After the rebar of the bridge is tensioned, it passes through the steel beam and the anchor plates and is fixedly connected to the anchor plates by the rebar nuts. The end of the rebar is connected to an extended rebar by another rebar nut. The extended rebar passes through the large reaction frame and is fixedly connected to the large reaction frame by another rebar nut.

[0010] In a preferred embodiment of the pre-tensioned bridge threaded steel graded and step-by-step synchronous tensioning device provided by the present invention, the hydraulic pump station includes an oil tank, a motor, a first oil pump, a second oil pump, and two reversing valve groups. The motor drives the first oil pump and the second oil pump in series via the motor shaft. The input ends of the first oil pump and the second oil pump are respectively connected to the oil tank. The output end of the first oil pump is connected to the upper jack unit through one of the reversing valve groups. The output end of the second oil pump is connected to the lower jack unit through the other reversing valve group. The motor, the first oil pump, the second oil pump, and the two reversing valve groups are respectively electrically connected to the control component.

[0011] In a preferred embodiment of the pre-tensioned bridge threaded steel graded and step-by-step synchronous tensioning device provided by the present invention, the reversing valve group includes an overflow valve, a three-position four-way reversing valve with H-type center position function, a check valve, a slow unloading valve, and a fast unloading valve. The pressure port of the three-position four-way reversing valve is connected to the output end of the first oil pump or the second oil pump, the return port of the three-position four-way reversing valve is connected to the oil tank, and the two working ports of the three-position four-way reversing valve are respectively connected to the rod chamber and the rodless chamber of the upper jack unit or the lower jack unit. The check valve, the slow unloading valve, and the fast unloading valve are sequentially arranged in the oil line between the three-position four-way reversing valve and the rodless chamber. The overflow valve is arranged in the oil line between the three-position four-way reversing valve and the first oil pump or the second oil pump, and the three-position four-way reversing valve, the slow unloading valve, and the fast unloading valve are respectively electrically connected to the control component.

[0012] In a preferred embodiment of the pre-tensioned bridge threaded steel graded and step-by-step synchronous tensioning device provided by the present invention, both the upper jack unit and the lower jack unit are equipped with displacement sensors and pressure sensors, and the displacement sensors and the pressure sensors are electrically connected to the control component respectively.

[0013] This invention also provides a method for staged and step-by-step synchronous tensioning of pre-tensioned bridge rebar, comprising the following steps:

[0014] After tensioning begins, the control components acquire the tilt angle of the large reaction frame in real time.

[0015] The control component determines whether the tilt angle exceeds a preset tilt angle threshold. If it does not exceed the threshold, the control component performs a graded and step-by-step cyclic tensioning operation. The graded and step-by-step cyclic tensioning operation includes: after tensioning begins, the control component first drives the lower jack unit to travel a predetermined stroke and then holds the pressure. After holding the pressure, the control component drives the upper jack unit to travel the same predetermined stroke and then holds the pressure. This process is repeated until the designed tension elongation is reached. If the tilt angle exceeds the threshold, the control component pauses the graded and step-by-step cyclic tensioning operation and performs a tilt correction operation. The tilt correction operation includes: the control component determines and controls the jack unit with lag in displacement to perform a stroke compensation operation, adjusting the tilt angle of the large reaction frame to zero degrees, stopping the tilt correction operation, and continuing to perform the graded and step-by-step cyclic tensioning operation.

[0016] In a preferred embodiment of the pre-tensioned bridge threaded steel graded and step-by-step synchronous tensioning method provided by the present invention, the control component determines and controls the jack unit with displacement lag to perform a stroke compensation operation, including: the control component detects the real-time displacement of the upper jack unit and the lower jack unit based on displacement sensors respectively installed on the upper jack unit and the lower jack unit; calculates the displacement difference based on the real-time displacement of the upper jack unit and the lower jack unit; when the absolute value of the displacement difference exceeds a preset synchronous deviation threshold, compares the real-time displacement of the upper jack unit and the lower jack unit and determines that the jack unit with the smaller real-time displacement is the one with displacement lag; the control component controls the jack unit with displacement lag to perform a stroke compensation operation.

[0017] In a preferred embodiment of the pre-tensioned bridge threaded steel graded and step-by-step synchronous tensioning device provided by the present invention, an unloading and reset step is also included. The unloading and reset step includes: after tensioning is completed, the slow unloading valve and the fast unloading valve are opened in sequence to unload the jack assembly, and then the three-position four-way reversing valve is reversed to reset the jack assembly.

[0018] Compared with existing technologies, the pre-tensioned bridge rebar graded and step-by-step synchronous tensioning device and tensioning method provided by this invention have the following advantages:

[0019] This invention effectively adapts to the differences in tension loads under varying reinforcement conditions by employing two different specifications of jacks, one for sparse reinforcement in the upper part of the beam and the other for dense reinforcement in the lower part. By incorporating a universal ball joint structure, the jacks can adapt to angular deviations during tensioning, eliminating off-center loading, protecting jack seals, and extending their service life. Through graded, step-by-step cyclic tensioning operations combined with real-time monitoring and feedback from tilt sensors, synchronized tensioning of the upper and lower jacks is achieved, ensuring precise tension displacement control. Tilt correction operations adjust the stroke of lagging jacks, effectively maintaining the stability of the large reaction frame and further improving tension synchronization accuracy. The system configuration is simplified by using a single motor with dual oil pumps in series in the hydraulic pump station. The reliability of the hydraulic system is improved by using a three-position four-way directional valve with H-type center position function combined with a check valve to achieve pressure holding. The graded unloading design of slow and fast unloading valves reduces unloading impact. The overall device has a simple structure, clear control logic, and is economical and reliable, effectively reducing the risk of beam deformation and improving the overall quality of bridge prestressed construction. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the overall structure of the pre-tensioned bridge threaded steel graded and step-by-step synchronous tensioning device provided in an embodiment of the present invention;

[0022] Figure 2 This is a side view of the pre-tensioned bridge threaded steel graded and step-by-step synchronous tensioning device provided in an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the hydraulic system of the pre-tensioned bridge rebar graded and step-by-step synchronous tensioning device provided in this embodiment of the invention;

[0024] Figure 4 This is a schematic diagram of the structure of the jack provided in an embodiment of the present invention;

[0025] Figure 5 This is a structural block diagram of the pre-tensioned bridge threaded steel graded and step-by-step synchronous tensioning device provided in an embodiment of the present invention;

[0026] Figure 6 This is a schematic flowchart of the pre-tensioned bridge threaded steel graded and step-by-step synchronous tensioning method provided in the embodiments of the present invention.

[0027] The attached figures are labeled as follows:

[0028] 1. Bridge; 2. Steel beam; 3. 250T jack pad; 4. 250T jack; 5. Large reaction frame; 6. Tilt sensor; 7. Upper anchor plate; 8. Lower anchor plate; 9. 400T jack; 10. Jack support frame; 11. 400T jack pad; 12. Oil pipe; 13. Hydraulic pump station; 131. Motor; 132. First oil pump; 133. Second oil pump; 134. Overflow valve; 135. Three-position four-way directional valve; 136. Check valve; 137. Slow unloading valve; 138. Fast unloading valve; 14. Displacement sensor; 15. Threaded steel nut; 16. Universal ball joint structure; 161. Force transmission plate; 17. Threaded steel; 18. Extended threaded steel; 19. Pressure sensor; 20. Control components. Detailed Implementation

[0029] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0030] In embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as superior or more advantageous than other embodiments or designs. Rather, the use of the term "exemplary" is intended to present the concept in a specific manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0031] like Figures 1 to 5As shown in the figure, this embodiment of the invention provides a staged and step-by-step synchronous tensioning device for pre-tensioned bridge rebar, including a steel beam 2, a jack assembly, a support assembly, a large reaction frame 5, an anchoring assembly, a hydraulic pump station 13, an inclination sensor 6, and a control assembly 20. The steel beam 2, the support assembly, and the large reaction frame 5 are sequentially arranged at one end of the bridge 1 to be tensioned; the jack assembly is mounted on the support assembly; the jack assembly includes an upper jack unit and a lower jack unit, the upper jack unit uses a 250T jack 4, and the lower jack unit uses a 400T jack 9. Displacement sensors 14 and pressure sensors 19 are installed on both the 250T jack 4 and the 400T jack 9. The piston rod ends of both the upper and lower jack units are equipped with universal ball joint structures 16, which are connected to the large reaction frame 5 respectively. The support components include a 250T jack pad 3, a jack support frame 10, and a 400T jack pad 11. The anchoring components are detachably connected to the large reaction frame 5 and include an upper anchor plate 7, a lower anchor plate 8, and a threaded steel nut 15. The hydraulic pump station 13 is connected to both the upper and lower jack units respectively. The tilt sensor 6 is located on the side of the large reaction frame 5. The control components 20 are electrically connected to the hydraulic pump station 13, the displacement sensor 14, the pressure sensor 19, and the tilt sensor 6 respectively. During tensioning, the steel beam 2 is fixedly set at the preset positions at both ends of the bridge 1. The 250T jack 4 and 400T jack 9 are supported and fixed on the working platform of the steel beam 2 by the jack support frame 10. A 250T jack pad 3 is set between the 250T jack 4 and the steel beam 2 to expand the force-bearing area and protect the surface of the steel beam 2. A 400T jack pad 11 is set between the 400T jack 9 and the steel beam 2 to play the same role in force transmission and protection. The jack support frame 10 is made of welded steel sections, and its structural strength is designed and checked according to the maximum output load of the jack to ensure that it provides stable and reliable support during the tensioning process.

[0032] The jack assembly in this invention consists of an upper jack unit and a lower jack unit. The upper jack unit uses a 250T jack 4, with a rated output load of 250 tons, specifically designed for tensioning the sparsely arranged threaded steel bars 17 in the upper half of the bridge beam 1. The lower jack unit uses a 400T jack 9, with a rated output load of 400 tons, specifically designed for tensioning the densely arranged threaded steel bars 17 in the lower half of the bridge beam 1. The two different tonnage jacks correspond to different reinforcement densities in the upper and lower parts of the beam, effectively solving the problem of tension load differences caused by differentiated reinforcement. This differentiated configuration ensures that the output capacity of the upper and lower jacks matches the number of threaded steel bars 17 connected to them and the required tension force, avoiding overload or underload phenomena caused by using a single-specification jack.

[0033] like Figure 4As shown, both the 250T jack 4 and the 400T jack 9 have universal ball joint structures 16 at their piston rod ends. Each universal ball joint structure 16 includes a ball socket at the piston rod end and a force transmission plate 161 corresponding to the ball socket. One side of the force transmission plate 161 has a spherical head that is embedded in the ball socket to form a spherical fit connection. Specifically, the outer spherical diameter of the spherical head can be 80 to 120 mm, and the inner spherical diameter of the ball socket is slightly larger than the outer spherical diameter of the spherical head. The fit clearance between the two is 0.1 to 0.3 mm. Both the piston rod and the force transmission plate can be made of 40Cr alloy steel. The piston rod end is recessed inward along the axial direction to form a ball socket to accommodate the spherical head. The surfaces of the ball socket and the spherical head are heat-treated to achieve a surface hardness of HRC 28 to 32, ensuring sufficient strength and wear resistance. The side of the force transmission plate 161 furthest from the piston rod end can be connected to the bearing surface of the large reaction frame 5, or fixedly connected to the bearing surface of the large reaction frame 5 by high-strength bolts. The spherical fit structure allows the jack piston rod to automatically adjust its angle within a certain tilt range, ensuring that the piston rod axis always remains aligned with the direction of the force. When the large reaction frame 5 tilts or the threaded steel 17 is misaligned during tensioning, the universal ball joint structure 16 automatically adapts to the angle change through spherical sliding, eliminating off-center loading, protecting the jack seals, and extending their service life.

[0034] A large reaction frame 5 is installed on the outside of the steel beam 2 as a reaction support structure during the tensioning process. Specifically, the large reaction frame 5 can be a box-section steel structure, with the cross-sectional dimensions designed according to the maximum tension load. Its height extends through the entire height of the bridge beam 1, ensuring that the tensioning reaction forces of the upper and lower threaded steel bars 17 act on the same reaction structure. A tilt sensor 6 is fixedly installed on the upper side of the large reaction frame 5. The tilt sensor 6 is installed at the midpoint of the height direction of the large reaction frame 5, which is the most sensitive position to detect changes in the tilt state of the large reaction frame 5. The tilt sensor 6 can be a dual-axis tilt sensor with a measurement range of zero to ±15 degrees and a measurement accuracy of 0.01 degrees. It can monitor the tilt angle of the large reaction frame 5 in real time during the tensioning process and transmit the tilt angle signal to the control component 20 as a synchronous control feedback signal. The control component 20 determines whether a tilt correction operation needs to be performed based on the tilt angle. When the tilt angle exceeds a preset tilt angle threshold, the tilt correction operation is automatically triggered.

[0035] The anchoring assembly includes an upper anchor plate 7, a lower anchor plate 8, and a threaded steel nut 15. In the pre-tensioning process provided by the present invention, both the upper and lower threaded steel bars 17 are tensioned at both ends, with the anchoring end located on the side wall of the steel beam 2 and the tensioning end located on the side wall of the large reaction frame 5. Specifically, at the anchoring end, the upper anchor plate 7 and the lower anchor plate 8 are attached to the side wall of the steel beam 2. The threaded steel bar 17 is led out from the bridge beam 1 and passes through the steel beam 2 and the upper anchor plate 7 or the lower anchor plate 8. Then, the threaded steel bar 17 is locked and fixed to the upper anchor plate 7 or the lower anchor plate 8 by the threaded steel bar nut 15. At the tensioning end, the tail of the threaded steel bar 17 is connected to an extended threaded steel bar 18 by a threaded steel bar nut 15. The extended threaded steel bar 18 passes through a pre-reserved circular hole on the large reaction frame 5. The tail of the extended threaded steel bar 18 is then locked and fixed to the outside of the large reaction frame 5 by another threaded steel bar nut 15. The upper threaded steel bar 17 and the lower threaded steel bar 17 adopt the same connection method, and both use a double nut locking structure to ensure a reliable anchoring effect.

[0036] Displacement sensor 14 is installed on the piston rod or cylinder of the 250T jack 4 and the 400T jack 9. Specifically, displacement sensor 14 can be a high-precision wire-type displacement sensor with a measurement stroke of 0 to 300 mm, a measurement accuracy of 0.05 mm, and a resolution of 0.01 mm. The working principle of displacement sensor 14 is as follows: the fixed end of the wire is connected to the jack cylinder, and the movable end of the wire is connected to the end of the piston rod. When the jack piston rod extends or retracts, the wire moves synchronously with the piston rod, and the internal circuit of the sensor converts the displacement of the wire into an electrical signal output. Since the extension displacement of the jack piston has a fixed proportional relationship with the elongation of the threaded steel 17, the actual elongation of the threaded steel 17 can be accurately calculated by monitoring the output signal of displacement sensor 14 in real time, thereby achieving precise control of the tension elongation. The signal of displacement sensor 14 is also transmitted to control component 20 and compared with the preset tension elongation target value as the basis for determining the stop of the graded and step-by-step cyclic tensioning process.

[0037] The hydraulic system used in this invention includes a hydraulic pump station 13, oil pipes 12, and a directional valve assembly. For example... Figure 3As shown, the hydraulic pump station 13 includes an oil tank, a motor 131, a first oil pump 132, a second oil pump 133, and two directional valve groups. The motor 131 drives the first oil pump 132 and the second oil pump 133 in series via a motor shaft. The input ends of the first oil pump 132 and the second oil pump 133 are respectively connected to the oil tank. The output end of the first oil pump 132 is connected to the upper jack unit through one directional valve group, and the output end of the second oil pump 133 is connected to the lower jack unit through another directional valve group. The motor 131, the first oil pump 132, the second oil pump 133, and the two directional valve groups are all electrically connected to the control component 20. This configuration requires only one motor 131 to drive two oil pumps, effectively simplifying the hydraulic system structure and reducing equipment costs. The displacement of the first oil pump 132 and the second oil pump 133 are selected according to the flow requirements of the jacks they serve. The first oil pump 132 has a smaller displacement to match the flow requirements of the 250T jack 4, while the second oil pump 133 has a larger displacement to match the flow requirements of the 400T jack 9, so as to realize independent oil supply and flow matching of the upper and lower hydraulic circuits.

[0038] Two directional valve assemblies are respectively configured to correspond to the upper jack unit and the lower jack unit. Each directional valve assembly includes an overflow valve 134, a three-position four-way directional valve 135 with H-type center position function, a check valve 136, a slow unloading valve 137, and a fast unloading valve 138. The pressure port of the three-position four-way directional valve 135 is connected to the output end of the first oil pump 132 or the second oil pump 133, and the return port of the three-position four-way directional valve 135 is connected to the oil tank. The two working ports of the three-position four-way directional valve 135 are respectively... The rod-side and rodless chambers of the upper or lower jack unit are connected. A one-way valve 136, a slow-speed unloading valve 137, and a fast-speed unloading valve 138 are sequentially arranged in the oil line between the three-position four-way directional valve 135 and the rodless chamber. An overflow valve 134 is located in the oil line between the pressure port of the three-position four-way directional valve 135 and the first oil pump 132 or the second oil pump 133. The three-position four-way directional valve 135, the slow-speed unloading valve 137, and the fast-speed unloading valve 138 are electrically connected to the control assembly 20. Specifically, the three-position four-way directional valve 135 has four ports: P, T, A, and B. Port P is the pressure port connected to the output end of the first oil pump 132 or the second oil pump 133. Port T is the return port connected to the oil tank. Ports A and B are the working ports, connected to the rod-side and rodless chambers of the jack, respectively. The three-position four-way directional valve 135 with H-type neutral position function is characterized in that: when the valve core of the three-position four-way directional valve 135 is in the neutral position, the P port and T port are interconnected, the A port and B port are interconnected, and all oil ports are in the conducting state. The hydraulic oil output by the oil pump can directly flow back to the oil tank through the P port and T port to achieve unloading. A relief valve 134 is connected at the P port for system overload protection. When the system pressure exceeds the preset value, the relief valve 134 opens to relieve pressure. In this embodiment, the three-position four-way directional valve 135, the slow unloading valve 137, and the fast unloading valve 138 can all be solenoid valves, which facilitates the control component 20 to control the opening or closing of the three-position four-way directional valve 135, the slow unloading valve 137, and the fast unloading valve 138.

[0039] A one-way valve 136 is installed in the B-port oil inlet line of the three-position four-way directional valve 135, with the valve core facing the rodless chamber of the jack. When the valve core of the three-position four-way directional valve 135 is in the neutral position, although ports P and T, and ports A and B are interconnected, the hydraulic oil in the rodless chamber of the jack cannot flow back to the oil tank through port B due to the check valve 136, thus achieving the pressure-holding function of the hydraulic cylinder. This pressure-holding mechanism has a simple structure and reliable response, and can maintain the load state of the jack unit during tensioning without the need for an additional pressure-holding valve group, effectively solving the technical problem of temporary pressure holding during staged and step-by-step cyclic tensioning.

[0040] Slow-speed unloading valve 137 and fast-speed unloading valve 138 are connected in parallel in the oil circuit between check valve 136 and rodless chamber of jack. Slow-speed unloading valve 137 has a smaller flow rate and is used to achieve the first stage of smooth unloading; the unloading time can be set to three to five seconds. Fast-speed unloading valve 138 has a larger flow rate and is used to achieve the second stage of rapid unloading. During unloading, control component 20 first controls the opening of slow-speed unloading valve 137 to slowly reduce the system pressure. Once the pressure drops to a preset safety value, it then controls the opening of fast-speed unloading valve 138 to complete the remaining unloading process. Control component 20 can simultaneously monitor pressure changes in real time via pressure sensor 19. This staged unloading design effectively reduces the adverse effects of unloading impact on the device and threaded steel bar 17, and reduces pressure fluctuations and vibrations during the unloading process.

[0041] Oil pipe 12 can be connected using a high-pressure hose or a rigid pipe. The connection method is as follows: the inlet and return oil pipes of the 250T jack 4 and the 400T jack 9 are connected to the A and B ports of the corresponding three-position four-way directional valve 135 in the hydraulic pump station 13, respectively. The pressure rating of oil pipe 12 is selected based on 1.5 times the maximum working pressure of the system to ensure the safety and reliability of the hydraulic system. The layout of oil pipe 12 follows the shortest path principle to reduce pressure loss, and a reliable pipe clamp fixing method is used to prevent displacement and vibration of oil pipe 12 during tensioning.

[0042] The control component 20 can be an industrial computer, which is electrically connected to the tilt sensor 6, hydraulic pump station 13, displacement sensor 14 and pressure sensor 19 via a serial port. It is used to receive data from each component and send commands to the hydraulic pump station 13.

[0043] like Figure 6 As shown, the present invention also provides a method for staged and step-by-step synchronous tensioning of pre-tensioned bridge rebar, applied to the above-mentioned device for tensioning construction. This tensioning method includes the following steps:

[0044] After tensioning begins, the control component 20 acquires the tilt angle of the large reaction frame 5 in real time;

[0045] The control component 20 determines whether the tilt angle exceeds a preset tilt angle threshold. If it does not exceed the threshold, the control component 20 performs a graded and step-by-step cyclic tensioning operation. The graded and step-by-step cyclic tensioning operation includes: after tensioning begins, the control component 20 first drives the lower jack unit to travel a predetermined stroke and then holds the pressure. After holding the pressure, the control component 20 drives the upper jack unit to travel the same predetermined stroke and then holds the pressure. This process is repeated until the designed tension elongation is reached. If the tilt angle exceeds the threshold, the control component 20 pauses the graded and step-by-step cyclic tensioning operation and performs the tilt correction operation. The tilt correction operation includes: the control component 20 determines and controls the jack unit with lag in displacement to perform a stroke compensation operation, so that the tilt angle of the large reaction frame 5 is adjusted to zero degrees, the tilt correction operation is stopped, and the graded and step-by-step cyclic tensioning operation continues.

[0046] Specifically, the tensioning method includes four main stages: construction preparation, graded and step-by-step cyclic tensioning, tilt correction, and unloading and resetting.

[0047] During the construction preparation phase, firstly, place the 250T jack 4 and the 400T jack 9 on the jack support frame 10, and adjust the position of the jack components to align the axis of the jack piston rod with the axis of the threaded steel bar 17; place a 250T jack pad 3 between the 250T jack 4 and the steel beam 2, and a 400T jack pad 11 between the 400T jack 9 and the steel beam 2 to ensure that the jacks are placed stably and the force is evenly distributed; the universal ball joint structure 16 at the end of the jack piston rod is in contact with the bearing surface of the large reaction frame 5; the fixed end of the pull wire of the displacement sensor 14 is connected to the jack cylinder, and the movable end of the pull wire is connected to the end of the jack piston rod; adjust the displacement sensor... 14. Zero point and perform functional tests; tilt sensor 6 is installed at the midpoint of the upper side of the large reaction frame 5 along the height direction, and is calibrated to zero after power-on to ensure accurate tilt angle measurement reference; threaded steel bar 17 is arranged according to the design position and inserted into the hole of the upper anchor plate 7 or lower anchor plate 8, and locked and fixed to the side wall of steel beam 2 by threaded steel bar nut 15; the tail of threaded steel bar 17 is connected to an extension threaded steel bar 18 through a threaded steel bar nut 15, and the extension threaded steel bar 18 is locked and fixed by another threaded steel bar nut 15 after passing through the reserved hole on the large reaction frame 5; the hydraulic system is powered on and checked to confirm that the valve status is normal, the oil tank level is sufficient, and the pipeline connection is reliably sealed.

[0048] The tiered and step-by-step cyclic tensioning stage is the main tensioning operation. After tensioning begins, the control component 20 acquires the tilt angle of the large reaction frame 5 in real time through the tilt sensor 6. When the tilt angle of the large reaction frame 5 does not exceed the preset tilt angle threshold, the control component 20 executes the tiered and step-by-step cyclic tensioning operation. In this embodiment, the tilt angle threshold can be set to ±5°. The specific action sequence of this tiered and step-by-step cyclic tensioning operation is as follows: First, the control component 20 controls the three-position four-way reversing valve 135 connected to the lower jack unit to reverse so that oil enters through port B. The hydraulic oil output by the second oil pump 133 enters the 400T jack through the one-way valve 136. The rodless chamber of jack 9 pushes the piston rod forward, driving the piston rod of the lower jack unit to travel a predetermined stroke in the direction of the large reaction frame 5. The predetermined stroke can be set according to actual construction needs; in this embodiment, the predetermined stroke is set to three millimeters. The displacement sensor 14 monitors the displacement of the piston rod of the 400T jack 9 in real time. When the displacement reaches three millimeters, the control component 20 sends a stop signal. Then, the control component 20 switches the three-position four-way directional valve 135 connected to the lower jack unit to the neutral position. Due to the H-type neutral position function, the P port of the three-position four-way directional valve 135... The system connects to port T, unloads the second oil pump 133, and simultaneously closes the check valve 136, cutting off the hydraulic oil in the rodless chamber of the 400T jack 9 to maintain pressure. The lower jack unit maintains its current stroke load state. Next, the control component 20 controls the three-position four-way directional valve 135 connected to the upper jack unit to switch, allowing oil to enter through port B. The hydraulic oil output from the first oil pump 132 enters the rodless chamber of the 250T jack 4 through the check valve 136, pushing the piston rod forward and driving the piston rod of the upper jack unit to travel the same predetermined stroke (three millimeters) in the direction of the large reaction frame 5. The displacement sensor 14 monitors the piston rod displacement of the 250T jack 4 in real time. When the displacement reaches three millimeters, the control component 20 sends a stop signal. Then, the control component 20 switches the three-position four-way directional valve 135 connected to the upper jack unit to the middle position. At the same time, the first oil pump 132 is unloaded and the one-way valve 136 is closed, and the 250T jack 4 maintains the load state. Finally, the control component 20 judges whether the tension elongation detected by the displacement sensor 14 has reached the design requirement value. If it has not reached the design requirement value, the above action sequence is repeated until the design tension elongation is reached.

[0049] In the aforementioned graded and step-by-step cyclic tensioning process, the tensioning deformation of the upper and lower threaded steel bars 17 is alternating. When the lower jack unit extends 3 mm to tension the lower threaded steel bar 17, the upper threaded steel bar 17 remains under load; when the lower jack unit maintains pressure while the upper jack unit extends 3 mm to tension the upper threaded steel bar 17, both the upper and lower threaded steel bars 17 bear the tension force simultaneously. This alternating tensioning method allows the tensioning deformation of the upper and lower threaded steel bars 17 to gradually accumulate and tend to synchronize, effectively avoiding the problem of uneven prestress distribution caused by differences in the upper and lower reinforcement in traditional synchronous tensioning methods.

[0050] The tilt correction stage is used to address the cumulative displacement error caused by factors such as the retraction of the steel strands during tensioning. When the tilt sensor 6 detects that the tilt angle of the large reaction frame 5 exceeds the preset tilt angle threshold, the control component 20 pauses the graded and step-by-step cyclic tensioning operation and performs a tilt correction operation. The control component 20 determines and controls the jack unit with lagging displacement to perform a stroke compensation operation, adjusting the tilt angle of the large reaction frame to zero degrees, stopping the tilt correction operation, and continuing to perform the graded and step-by-step cyclic tensioning operation. The jack unit with lagging displacement is the jack on the lagging side that caused the large reaction frame 5 to tilt. Specifically, the control component 20 detects the real-time displacement of the upper and lower jack units using displacement sensors 14 respectively installed on the upper and lower jack units; calculates the displacement difference based on the real-time displacement of the upper and lower jack units; when the absolute value of the displacement difference exceeds the preset synchronization deviation threshold (in this embodiment, the synchronization deviation threshold is set to 0.5mm, and the setting of the synchronization deviation threshold can be adjusted according to the actual construction situation), compares the real-time displacement of the upper and lower jack units and determines that the jack unit with the smaller real-time displacement is the one with displacement lag; the control component 20 calculates the stroke compensation amount according to the preset stroke compensation algorithm, and controls the jack unit with displacement lag to perform stroke compensation operation according to the stroke compensation amount. For example, assuming the retraction of the lower threaded steel bar 17 is greater than that of the upper threaded steel bar 17, that is, the actual displacement value of the lower jack unit is less than that of the upper jack unit, causing the large reaction frame 5 to tilt downwards. When the displacement difference between the upper and lower jack units exceeds 0.5mm, the lower jack unit becomes the lagging jack. The control component 20 controls the three-position four-way directional valve 135 corresponding to the lower jack unit to switch to allow oil to enter through port B, driving the lower jack unit to independently tension forward for the supplementary stroke operation. During the supplementary stroke operation, the control component 20 supplements according to the preset step. The compensation algorithm calculates the stroke compensation amount L = K·|θ| (K is the conversion factor between tilt angle and stroke amount, |θ| is the absolute value of the tilt angle, and L is in mm). Control component 20 controls the lower jack unit to tension forward independently based on the stroke compensation amount. Tilt sensor 6 continuously monitors the tilt angle change of the large reaction frame 5. As the tilt angle gradually decreases and approaches zero degrees, the stroke compensation amount calculated by control component 20 also gradually decreases. When the tilt angle returns to near zero degrees, control component 20 issues a stop signal to shut down the stroke compensation action. After the tilt angle returns to zero, the graded and step-by-step cyclic tensioning operation continues. This tilt correction operation, through real-time monitoring and dynamic compensation, effectively eliminates the accumulation of displacement errors caused by factors such as steel strand retraction during tensioning, maintains the stability of the large reaction frame 5's posture, further improves tensioning synchronization accuracy, reduces the tilting force on the jack piston, and lowers the risk of seal wear and oil leakage.

[0051] The unloading and reset phase is the final operation after tensioning. First, the slow unloading valve 137 and the fast unloading valve 138 are opened sequentially to allow the jack unit to unload smoothly in stages. Specifically, the slow unloading valve 137 is opened for three to five seconds, and the system pressure slowly decreases. Once the pressure drops to a preset safety value, such as five MPa, the fast unloading valve 138 is opened to complete the remaining unloading. Then, the control component 20 controls the three-position four-way directional valve 135 to switch so that oil enters through port A. The hydraulic oil output from the oil pump enters the rod chamber of the jack, pushing the piston rod to retract and reset. The displacement sensor 14 monitors the piston rod's retraction position. When the piston rod has fully retracted to its initial position, the control component 20 issues a stop signal. Finally, the threaded steel nut 15 and the extended threaded steel 18 are removed, the site is cleaned, and the tensioning operation is completed.

[0052] In practical engineering applications, taking a prestressed concrete simply supported beam bridge on a highway as an example, the bridge span is 30 meters, the beam height is 1.8 meters, the upper part is equipped with 36 PSB930 grade threaded steel bars with a diameter of 32 mm, and the lower part is equipped with 48 threaded steel bars of the same specification. According to the traditional synchronous tensioning process, the tension load difference between the upper and lower parts reaches more than 30%, which easily leads to uneven distribution of prestress. After adopting the device and method of this invention, 250T jacks are used to tension the 36 threaded steel bars in the upper part, and 400T jacks are used to tension the 48 threaded steel bars in the lower part. Each cycle of tensioning is 3 mm, the tension force of a single threaded steel bar in the upper part increases by about 15 kN, and the tension force of a single threaded steel bar in the lower part increases by about 10 kN. The tension deformation gradually accumulates until the design elongation is reached. During construction, the tilt sensor 6 monitors the posture of the large reaction frame in real time. When the tilt angle exceeds ±5°, the tilt correction operation is automatically triggered, and the large reaction frame 5 is kept in a horizontal state by adjusting the stroke. After tensioning, the prestress is evenly distributed, and the camber of the bridge beam meets the design requirements, effectively reducing the risk of beam deformation and improving the overall quality of bridge prestressing construction.

[0053] The pre-tensioning bridge rebar graded and step-by-step synchronous tensioning device and method of this invention effectively adapts to the differences in tension loads under different reinforcement conditions by using two different specifications of jacks, 250 tons and 400 tons, respectively, for the sparse reinforcement in the upper part and the dense reinforcement in the lower part of the bridge beam. By setting up a universal ball joint structure 16, the jacks can adapt to angular deviations during the tensioning process, eliminating off-center loading, protecting the jack seals, and extending their service life. The graded and step-by-step cyclic tensioning operation, combined with real-time monitoring by the tilt sensor 6, further enhances the tensioning effect. Feedback is provided to achieve coordinated and synchronous tensioning of the upper and lower jacks, ensuring the accuracy of tension displacement control. The tilt correction operation adjusts the stroke of the lagging jack, effectively maintaining the stability of the large reaction frame 5. The system configuration is simplified by using a single motor 131 connected in series with two oil pumps in the hydraulic pump station 13. The hydraulic system reliability is improved by using a three-position four-way directional valve 135 with H-type center position function in conjunction with a check valve 136 to achieve pressure holding. The staged unloading design of the slow unloading valve 137 and the fast unloading valve 138 reduces unloading impact. The overall device has a simple structure, clear control logic, and is economical and reliable, showing good application value and promising prospects in actual bridge prestressed construction.

[0054] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A staged and step-by-step synchronous tensioning device for pre-tensioned bridge threaded steel bars, characterized in that, The bridge includes a steel beam, a jack assembly, a support assembly, a reaction frame, an anchoring assembly, a hydraulic pump station, a tilt sensor, and a control assembly. The steel beam, the support assembly, and the reaction frame are sequentially arranged at the ends of the bridge to be tensioned. The jack assembly is mounted on the support assembly and includes an upper jack unit and a lower jack unit. The piston rod ends of both the upper and lower jack units are equipped with universal ball joint structures, which are respectively connected to the reaction frame. The anchoring assembly is detachably connected to the reaction frame. The hydraulic pump station is connected to both the upper and lower jack units. The tilt sensor is located on the side of the reaction frame. The control assembly is electrically connected to both the hydraulic pump station and the tilt sensor.

2. The pre-tensioned bridge rebar graded and step-by-step synchronous tensioning device according to claim 1, characterized in that, The universal ball joint structure includes a ball socket seat disposed at the end of the piston rod and a force transmission plate disposed corresponding to the ball socket seat. A spherical head is provided on one side of the force transmission plate, and the spherical head is embedded in the ball socket seat to form a spherical mating connection.

3. The pre-tensioned bridge rebar graded and step-by-step synchronous tensioning device according to claim 1, characterized in that, The support assembly includes a jack support frame and a jack pad. The jack assembly is mounted on the jack support frame, and the jack pad is located between the jack assembly and the steel beam.

4. The pre-tensioned bridge rebar graded and step-by-step synchronous tensioning device according to claim 1, characterized in that, The anchoring assembly includes an anchor plate and a threaded steel nut. The anchor plates are respectively located on the side of the jack assembly near the steel beam. After the threaded steel of the tensioned bridge passes through the steel beam and the anchor plate, it is fixedly connected to the anchor plate by the threaded steel nut. The end of the threaded steel is connected to an extension threaded steel by another threaded steel nut. The extension threaded steel passes through the large reaction frame and is fixedly connected to the large reaction frame by another threaded steel nut.

5. The pre-tensioned bridge rebar graded and step-by-step synchronous tensioning device according to claim 1, characterized in that, The hydraulic pump station includes an oil tank, a motor, a first oil pump, a second oil pump, and two directional valve groups. The motor drives the first oil pump and the second oil pump in series via a motor shaft. The input ends of the first oil pump and the second oil pump are respectively connected to the oil tank. The output end of the first oil pump is connected to the upper jack unit through one of the directional valve groups, and the output end of the second oil pump is connected to the lower jack unit through the other directional valve group. The motor, the first oil pump, the second oil pump, and the two directional valve groups are electrically connected to the control component.

6. The pre-tensioned bridge threaded steel graded and step-by-step synchronous tensioning device according to claim 5, characterized in that, The directional valve assembly includes a relief valve, a three-position four-way directional valve with H-type center position function, a check valve, a slow unloading valve, and a fast unloading valve. The pressure port of the three-position four-way directional valve is connected to the output end of the first oil pump or the second oil pump. The return port of the three-position four-way directional valve is connected to the oil tank. The two working ports of the three-position four-way directional valve are respectively connected to the rod chamber and the rodless chamber of the upper jack unit or the lower jack unit. The check valve, the slow unloading valve, and the fast unloading valve are sequentially arranged in the oil line between the three-position four-way directional valve and the rodless chamber. The relief valve is arranged in the oil line between the three-position four-way directional valve and the first oil pump or the second oil pump. The three-position four-way directional valve, the slow unloading valve, and the fast unloading valve are electrically connected to the control component.

7. The pre-tensioned bridge rebar graded and step-by-step synchronous tensioning device according to claim 1, characterized in that, Both the upper jack unit and the lower jack unit are equipped with displacement sensors and pressure sensors, and the displacement sensors and pressure sensors are electrically connected to the control component.

8. A method for staged and step-by-step synchronous tensioning of pre-tensioned bridge rebar, characterized in that, Includes the following steps: After tensioning begins, the control components acquire the tilt angle of the large reaction frame in real time. Determine whether the tilt angle exceeds a preset tilt angle threshold; If the tension is not exceeded, the control component performs a graded and step-by-step cyclic tensioning operation. The graded and step-by-step cyclic tensioning operation includes: after tensioning begins, the control component first drives the lower jack unit to travel a predetermined stroke and then holds the pressure. After holding the pressure, the control component drives the upper jack unit to travel the same predetermined stroke and then holds the pressure. This process is repeated until the designed tension elongation is reached. If the tension is exceeded, the control component pauses the graded and step-by-step cyclic tensioning operation and performs a tilt correction operation. The tilt correction operation includes: the control component determines and controls the jack unit with lag in displacement to perform a stroke compensation operation, so that the tilt angle of the large reaction frame is adjusted to zero degrees, the tilt correction operation is stopped, and the graded and step-by-step cyclic tensioning operation continues.

9. The method for graded and step-by-step synchronous tensioning of pre-tensioned bridge threaded steel bars according to claim 8, characterized in that, The control component determines and controls the jack unit with lag in displacement to perform a stroke compensation operation, including: the control component detects the real-time displacement of the upper jack unit and the lower jack unit based on displacement sensors respectively installed on the upper jack unit and the lower jack unit; calculates the displacement difference based on the real-time displacement of the upper jack unit and the lower jack unit; when the absolute value of the displacement difference exceeds a preset synchronization deviation threshold, compares the real-time displacement of the upper jack unit and the lower jack unit and determines that the jack unit with the smaller real-time displacement is the one with lag in displacement; the control component controls the jack unit with lag in displacement to perform a stroke compensation operation.

10. The method for graded and step-by-step synchronous tensioning of pre-tensioned bridge threaded steel bars according to claim 8, characterized in that, It also includes an unloading and reset step, which includes: after tensioning is completed, opening the slow unloading valve and the fast unloading valve in sequence to unload the jack assembly, and then switching the three-position four-way reversing valve to return the jack assembly to its original position.

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