Prestressed tendon tensioning structure of concrete structure and testing method

Abstract

This invention relates to the field of energy-saving building material production equipment technology, and discloses a prestressed tendon tensioning structure and testing method for concrete structures. The structure includes a fixed pipe with a connection port at one end, a straightening mechanism inside the fixed pipe, a slot at the end of the fixed pipe away from the connection port, and a hydraulic tensioning structure fitted onto the fixed pipe. The technical solution of this invention integrates the centering, straightening, and temporary anchoring functions of the steel strand through a pre-embedded fixed pipe and its internal straightening mechanism. Simultaneously, a rotating locking mechanism formed by the limiting block on the outer wall of the fixed pipe and the connecting block on the inner wall of the hydraulic tensioning structure enables rapid connection between the tensioning equipment and the pre-embedded module. Furthermore, by utilizing the precise initial benchmark and relative structural displacement established by the straightening mechanism, accurate testing of the prestress value and real-time monitoring of the anchoring status are simultaneously completed during the tensioning process.

Description

Technical Field

[0001] This invention relates to the field of energy-saving building material production equipment technology, specifically to a prestressed tendon tensioning structure and testing method for concrete structures. Background Technology

[0002] Prestressed concrete structures offer advantages such as lightweight construction, high span capacity, and steel savings, leading to their widespread application in bridge engineering, building structures, and rail transportation. Prestressing technology effectively counteracts tensile stresses generated under service loads by pre-establishing compressive stress within the concrete structure, significantly improving its crack resistance, load-bearing capacity, and durability. Prestressing tendons (typically steel strands or prestressed steel bars) are the core load-bearing elements of the prestressed system; their positioning accuracy and prestress magnitude directly affect the structure's safety and service life.

[0003] In the prestressed construction of concrete structures, the post-tensioning method is the most widely used. This method involves first pre-drilling ducts in the concrete member. After the concrete reaches its design strength, prestressing tendons are inserted into the ducts, and prestress is applied using tension jacks. Finally, anchorages are used to lock the prestress onto the concrete structure. This process involves multiple stages, including tendon placement, tensioning, and testing and verification of the prestressing effect. The construction quality of each stage significantly impacts the final structural performance.

[0004] Currently, the construction and testing of prestressed concrete beams mainly rely on traditional manual methods. The conventional process is as follows: workers first fix corrugated pipes into the beam's reinforcing steel frame according to the design alignment; then, prestressing tendons are inserted one by one into the corrugated pipes, manually adjusted to ensure they are roughly centered within the pipes; after the concrete is poured and cured to reach its strength, tensioning equipment such as jacks is used for tensioning; finally, the prestress values ​​are tested and verified using methods such as pressure gauge readings, elongation measurements, or the reverse tension method. However, existing construction techniques have many insurmountable technical problems, severely restricting the efficient production and quality assurance of prestressed concrete structures.

[0005] First, aligning prestressing tendons is difficult, and ensuring positioning accuracy is challenging. Traditional methods rely on workers' visual inspection and experience, adjusting by hand or using temporary shims. This manual alignment method is not only inefficient but also lacks precision, often resulting in deviations between the center of the steel strand and the designed tensioning axis exceeding permissible limits. When tensioning begins, initial eccentricity leads to uneven stress distribution in the anchorage zone, with some strands experiencing higher stress and others lower, potentially causing scratches or slippage of the tendons. More critically, poor alignment causes an angle between the tension force and the design axis, resulting in prestress loss. This loss cannot be accurately measured and corrected during construction, ultimately leading to a significant discrepancy between the actual prestress and the design value, hindering the full utilization of material properties and wasting valuable resources.

[0006] Secondly, the installation efficiency is low and incompatible with industrialized production models. The installation process of traditional tensioning equipment is extremely cumbersome. At each tensioning point, workers need to install the limiting plate, jack, and tool anchor in sequence. These three components are connected by threads or slots, and repeated adjustments and alignment are required before they can be locked. This process usually requires 2 to 3 people to operate, takes 15 to 20 minutes, and demands a high level of skill from the workers. In multi-point tensioning operations of continuous beams, a significant amount of time is consumed in the repeated disassembly and assembly of equipment, severely restricting construction efficiency and becoming a bottleneck affecting rapid construction. At the same time, since the jack, limiting plate, and tool anchor are three independent components, there are gaps and flexible deformation spaces at their connections. Under the action of hundreds of tons of tension force, the entire system is prone to swaying and eccentricity, further aggravating the deviation of the tensioning axis, leading to inaccurate prestressing and affecting structural performance.

[0007] Third, inaccurate prestress testing makes it difficult to accurately reflect the structural stress state. After tensioning, prestress values ​​are typically determined by hydraulic pressure conversion using jacks or by subsequent random checks. Hydraulic pressure conversion is affected by the internal friction of the jacks and alignment deviations, resulting in significant errors. Subsequent random checks often lag behind the tensioning operation, making real-time monitoring of the tensioning process impossible. Regarding elongation measurement, the traditional method involves marking the exposed ends of the steel strands before tensioning and manually measuring with a steel ruler after tensioning. Because the initial state of the steel strands is curved, the measurement benchmark is difficult to standardize, leading to large dispersion in elongation data and failing to accurately reflect the true prestress establishment. More critically, there is a lack of effective monitoring methods for the locking state of the wedges at the moment of anchorage completion. If the wedge retraction is excessive or the locking is uneven, it is often only discovered during post-incident inspection, at which point it is too late to remedy the situation, creating a quality hazard that may lead to premature failure of the prestressed concrete structure due to insufficient prestress.

[0008] To address the aforementioned problems, this invention provides a method for precise positioning and testing of prestressed tendons in concrete structures. It aims to fundamentally solve the technical bottlenecks of difficult centering, low efficiency, and inaccurate testing in traditional processes by combining a centering and straightening mechanism, modular pre-embedded design, and a rapid clamping tensioning device. This ensures that the material properties of prestressed concrete structures are fully utilized, achieving high-quality and high-efficiency industrial production. Summary of the Invention

[0009] In view of the above-mentioned shortcomings of the prior art, the present invention provides a prestressed tendon tensioning structure and testing method for concrete structures, which can effectively solve the problems existing in the prior art.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] This invention provides a prestressed tendon tensioning structure for a concrete structure, including a box girder with multiple tensioning points at both ends. Each tensioning point has a fixed anchor for anchoring steel strands. The structure also includes a fixing pipe with a connection port at one end for connecting to the fixed anchor. A straightening mechanism for straightening and centering the steel strands passing through the fixing pipe is provided within the fixing pipe. A slot for installing a movable anchor is provided at the end of the fixing pipe away from the connection port. A hydraulic tensioning structure for tensioning the steel strands is sleeved on the fixing pipe.

[0012] Furthermore, the fixed tube includes a connecting part and a moving part. The moving part is sleeved on the outside of the connecting part and can slide along the axial direction of the connecting part. A guide block is provided at the end of the connecting part away from the fixed anchor. A connecting groove that slides with the guide block is provided at one end of the moving part. A locking mechanism for connecting with the hydraulic tensioning structure is provided on the moving part.

[0013] Furthermore, the straightening mechanism includes a movable plate, which is disposed inside the movable part. Multiple horizontal tubes for threading steel strands are fixed on the movable plate. Clamping blocks for straightening steel strands are disposed inside the horizontal tubes. A slider is disposed on the outer edge of the movable plate. A sliding groove is disposed on the inner wall of the movable part to slide with the slider. A connecting ring for driving the movable plate to move axially along the movable part is sleeved on the outer side of the movable part. The connecting ring is fixedly connected to the slider.

[0014] Furthermore, a wedge-shaped guide slope is provided at one end of the clamping block near the connecting part. When the moving plate moves away from the connecting part, the guide slope forms a wedge-tight fit with the surface of the steel strand to prevent the steel strand from retracting.

[0015] Furthermore, the hydraulic tensioning structure includes an outer shell and a connecting sleeve that can move axially relative to the outer shell. The connecting sleeve is hollow and is sleeved on the outside of the fixed tube. The outer shell is provided with a reaction support structure for abutting against the box girder during tensioning.

[0016] Furthermore, the locking mechanism includes multiple limiting blocks disposed on the outer wall of the fixed tube, with a gap groove formed between adjacent limiting blocks, and multiple connecting blocks disposed on the inner wall of the connecting sleeve, with the positions of the connecting blocks corresponding to the gap grooves.

[0017] Furthermore, the limiting blocks are evenly distributed along the circumference of the fixed pipe, and the connecting blocks are evenly distributed along the inner wall of the connecting sleeve. When the connecting sleeve is fitted on the outside of the fixed pipe, the connecting blocks pass through the spacer groove. By rotating the connecting sleeve, the connecting blocks rotate behind the limiting blocks and form an abutment fit with the limiting blocks in the axial direction, thereby realizing the connection between the connecting sleeve and the fixed pipe.

[0018] A prestress testing method includes the following steps:

[0019] Step S1: During the prefabrication stage of the box girder, the fixing pipe is connected to the fixing anchor through the connection port, and the steel strand is passed through the straightening mechanism inside the fixing pipe;

[0020] Step S2: Pull the connecting ring in the straightening mechanism to move the moving plate away from the connecting part. The steel strand is straightened and kept in the center by the clamping block in the horizontal tube. Record the initial position of the moving plate at this time as the zero point of displacement measurement.

[0021] Step S3: Place the connecting sleeve of the hydraulic tensioning structure on the outside of the fixed tube, connect and lock it through the locking mechanism;

[0022] Step S4: Activate the hydraulic tensioning structure to apply tension force to the steel strands. During the tensioning process, monitor the following parameters in real time:

[0023] Tension force value P: Calculated using hydraulic system pressure;

[0024] Displacement value S: measures the axial displacement of the connecting sleeve relative to the fixed pipe or the actual displacement of the moving plate;

[0025] Step S5: When the tension reaches the design value P0, record the corresponding displacement value as the measured elongation S0 of the steel strand.

[0026] Step S6: Calculate the actual prestress value of the steel strand based on P0 and L0, and compare it with the theoretical value to determine whether the tensioning quality is qualified.

[0027] Furthermore, the specific method for real-time monitoring of the displacement value S in step S4 is as follows:

[0028] Set displacement measurement reference points on the connection part of the connecting sleeve or fixed pipe;

[0029] During the tensioning process, the axial displacement of the connecting sleeve relative to the fixed tube is measured by a laser displacement sensor or a mechanical dial indicator.

[0030] The displacement value S is the measured elongation of the steel strand. Since the steel strand has been straightened in step S2, there is no need to correct the initial curvature.

[0031] Furthermore, it also includes a step for monitoring the locking status of the clamping block:

[0032] During the tensioning process, the relative position or clamping force between the clamping block and the steel strand is monitored in real time.

[0033] When the tension reaches the design value P0, at the instant the hydraulic tensioning structure is depressurized, monitor whether the clamping block forms a wedge-tight fit with the steel strand, and record the locking displacement ΔS at this time.

[0034] If ΔS is within the preset range, the anchoring is deemed complete and effective.

[0035] If ΔS exceeds the preset range, an anchoring abnormality is determined and an alarm is triggered.

[0036] The technical solution provided by this invention has the following advantages compared with the prior art:

[0037] 1. The present invention is equipped with a fixing pipe, one end of which is fixedly connected to the fixing anchor through a connection port, thereby realizing the pre-installation of the tension structure on the box girder and avoiding the cumbersome process of assembling limiting plates, jacks and other components on site for each tension point in traditional construction.

[0038] Meanwhile, a straightening mechanism is installed in the fixed tube. When the steel strand passes through the fixed tube, the straightening mechanism can mechanically straighten and center the steel strand, eliminating the initial bending and eccentricity caused by the steel strand's own weight and threading. This solves the problems of low accuracy and unreliable centering in traditional manual visual adjustment. A slot for installing movable anchors is set at the end of the fixed tube away from the connection port, so that the steel strand always remains straight and centered before tensioning, providing stable and reliable initial conditions for subsequent tensioning operations.

[0039] 2. The present invention has a hydraulic tensioning structure sleeved on the fixed pipe. The tensioning force is directly transmitted to the fixed anchor through the fixed pipe, thereby pulling the steel strand. This realizes the separate design of the tensioning equipment and the centering anchoring structure, which allows the hydraulic tensioning structure to be quickly transferred and used between multiple tensioning points, significantly improving construction efficiency.

[0040] Meanwhile, by eliminating the bending of the steel strands in advance through the straightening mechanism, the steel strands have a uniform initial state before tensioning, providing an accurate zero point for displacement measurement in subsequent prestressing tests. This solves the problem of inconsistent benchmarks in traditional elongation measurement due to the initial bending of the steel strands, and enables the tension force applied by the hydraulic tensioning structure to correspond accurately with the displacement measurement value, thereby improving the reliability of prestressing test data and the controllability of construction quality. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the 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.

[0042] Figure 1 This is a schematic diagram of the box girder in an embodiment of the present invention;

[0043] Figure 2 This is a schematic diagram of the overall structure in an embodiment of the present invention;

[0044] Figure 3 This is a schematic diagram of the structure of the fixing pipe and the fixing anchor in an embodiment of the present invention;

[0045] Figure 4 This is a schematic diagram of the structure of the fixed tube in an embodiment of the present invention;

[0046] Figure 5 This is a schematic diagram of the internal structure of the fixed tube in an embodiment of the present invention;

[0047] Figure 6 This is a schematic diagram of the guide block in an embodiment of the present invention;

[0048] Figure 7 This is a schematic diagram of the hydraulic tensioning structure in an embodiment of the present invention;

[0049] Figure 8 This is a cross-sectional view of the fixed tube and the hydraulic tensioning structure in an embodiment of the present invention;

[0050] Figure 9 for Figure 8 Enlarged view of the structure of section A;

[0051] Figure 10 This is a flowchart illustrating the prestress testing method in an embodiment of the present invention.

[0052] Explanation of icon numbers:

[0053] 1. Box girder; 11. Tensioning point; 12. Fixed anchorage;

[0054] 2. Fixed tube; 21. Connecting port; 22. Slot; 23. Connecting part; 24. Moving part; 25. Guide block; 26. Connecting groove;

[0055] 3. Straightening mechanism; 31. Moving plate; 32. Horizontal tube; 33. Clamping block; 34. Slider; 35. Slide groove; 36. Connecting ring; 37. Guide slope;

[0056] 4. Hydraulic tensioning structure; 41. Outer shell; 42. Connecting sleeve;

[0057] 5. Engaging mechanism; 51. Limiting block; 52. Connecting block. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0059] The present invention will be further described below with reference to embodiments.

[0060] Example 1

[0061] Reference Figure 1 - Figure 5 This is the first embodiment of the present invention, providing a prestressed tendon tensioning structure for concrete structures. The box girder 1 refers to a precast concrete T-beam, a commonly used main beam structure in bridge engineering, named for its T-shaped cross-section. The box girder 1 consists of a top flange and a web, possessing advantages such as simple structure, clear stress distribution, and convenient precasting, and is widely used in highway and railway bridges with small to medium spans. In continuous beam bridges, the box girder 1 adopts a construction process of first simple support and then continuous support; that is, the box girder 1 is precast and erected in place, and then a continuous section is cast in place at the pier top and negative moment prestressed steel strands are tensioned, so that the box girders 1 of adjacent spans form a continuous structure.

[0062] Tensioning point 11 is a specific location at both ends of box girder 1 for applying prestress, typically located at the ends of the flanges or webs of box girder 1. In the negative bending moment section, tensioning point 11 is set on the top slab or flange of box girder 1 at the cast-in-place continuous section at the pier top. During construction, tensioning grooves and corrugated pipes are pre-installed during the prefabrication of box girder 1. After the wet joint concrete at the pier top reaches the design strength, the steel strands are threaded into the corrugated pipes, and tensioning is performed at tensioning point 11.

[0063] The fixed anchorage 12 is a device used to permanently anchor steel strands in prestressed concrete structures. It belongs to the category of permanent anchorage tools in post-tensioned structures, and its function is to maintain and transfer the tension of the prestressing tendons into the concrete. The fixed anchorage 12 typically consists of an anchor plate, wedges, and spiral reinforcement. During installation, the anchor plate is tightly fitted against the anchor pad, and the wedges are wedged into the conical holes of the anchor plate to hold the steel strands. When the tension is released, the wedges automatically lock, achieving permanent anchorage of the steel strands. In this invention, the fixed anchorage 12 is pre-installed on the anchor pad at the tensioning point 11 of the box girder 1, serving as the fixed end of the entire structure.

[0064] The existing construction process is as follows: When box girder 1 is prefabricated, corrugated pipes are pre-embedded in the negative bending moment section and tensioning grooves are reserved. After box girder 1 is erected, wet joint concrete of continuous section at the top of pier is poured. After the concrete reaches the design strength, steel strands are threaded into the corrugated pipes. Working anchors are installed at the tensioning end. Then, limit plates, jacks and tool anchors are installed in sequence. The axes of the three are adjusted to be aligned. The jacks are started to tension the girder. After the design stress is reached, the anchors are fixed. Then the jacks and tool anchors are disassembled to complete the operation of one tensioning point 11.

[0065] This process presents numerous problems: each tensioning point 11 requires repeated installation and disassembly of multiple components, resulting in cumbersome procedures and low efficiency; after the steel strands are threaded, they are often in a naturally relaxed state, exhibiting bending and eccentricity, while traditional methods rely on manual visual adjustment for alignment, which cannot guarantee accuracy; the jack, limit plate, and tool anchor are independent components with gaps at their connections, making the system prone to swaying under hundreds of tons of tension force, leading to deviation of the tension axis; poor alignment can cause the tension force direction to form an angle with the design axis, resulting in prestress loss, and this loss cannot be accurately measured and corrected.

[0066] The present invention provides a prestressed tendon tensioning structure for concrete structures, including a fixed pipe 2. One end of the fixed pipe 2 is provided with a connection port 21 for connecting with a fixed anchor 12. The fixed pipe 2 is provided with a straightening mechanism 3 for straightening and centering the steel strands passing through the fixed pipe 2. The end of the fixed pipe 2 away from the connection port 21 is provided with a slot 22 for installing a movable anchor. A hydraulic tensioning structure 4 for tensioning the steel strands is sleeved on the fixed pipe 2.

[0067] The fixed tube 2 includes a connecting part 23 and a movable part 24. The movable part 24 is sleeved on the outside of the connecting part 23 and can slide along the axial direction of the connecting part 23. Multiple guide blocks 25 are provided at the end of the connecting part 23 away from the fixed anchor 12, and a connecting groove 26 is provided at one end of the movable part 24 to slide with the guide blocks 25. Specifically, the guide blocks 25 are evenly distributed circumferentially along the connecting part 23, and guide grooves are formed between adjacent guide blocks 25; the connecting groove 26 is a groove structure corresponding to the number and position of the guide blocks 25. During installation, the movable part 24 is sleeved on the outside of the connecting part 23, so that the guide blocks 25 of the connecting part 23 are aligned with the connecting groove 26 of the movable part 24 and inserted. The guide blocks 25 can slide freely within the connecting groove 26, thereby guiding the movable part 24 to move smoothly along the axial direction of the connecting part 23, while restricting the rotation of the movable part 24 relative to the connecting part 23, ensuring that the two remain coaxial.

[0068] The connection method between the connection port 21 and the fixed anchor 12 can be selected from various existing connection methods according to construction needs, such as threaded connection, snap-fit ​​connection, flange bolt connection, etc. In this embodiment, flange bolt connection is preferred, that is, a flange is provided at the connection port 21, and it is fastened to the anchor plate of the fixed anchor 12 by high-strength bolts. This connection method has strong load-bearing capacity, high reliability, and is a mature existing technology, which is convenient for construction operation.

[0069] The straightening mechanism 3 includes a movable plate 31, which is disposed inside the moving part 24. Multiple horizontal tubes 32 for threading steel strands are fixed on the movable plate 31. The number of horizontal tubes 32 corresponds to the number of steel strands to be tensioned, and each steel strand passes through one horizontal tube 32 independently. A clamping block 33 for straightening the steel strand is disposed inside the horizontal tube 32. The clamping block 33 can be made of elastic material, and its inner diameter is slightly smaller than the outer diameter of the steel strand. When the steel strand passes through, the clamping block 33 applies a certain radial clamping force to the steel strand. A slider 34 is disposed on the outer edge of the movable plate 31, and a groove 35 is disposed on the inner wall of the moving part 24 to slide smoothly with the slider 34. The slider 34 is embedded in the groove 35 and can slide axially along the groove 35, thereby guiding the movable plate 31 to move smoothly. The outer side of the moving part 24 is fitted with a connecting ring 36 for driving the moving plate 31 to move along the axial direction of the moving part 24. The connecting ring 36 is fixedly connected to the slider 34. Specifically, it can be connected to the slider 34 by passing through a long groove on the side wall of the moving part 24 through a radial connecting member.

[0070] The working process and principle of the straightening mechanism 3 are as follows: After the steel strands are threaded, the worker pushes the connecting ring 36. The connecting ring 36 drives the slider 34, which is fixedly connected to it, to move along the slide groove 35. The slider 34 drives the moving plate 31 to move away from the connecting part 23, that is, towards the tensioning end. The horizontal tube 32 on the moving plate 31 moves accordingly. Since each steel strand passes through the horizontal tube 32 independently, the horizontal tube 32 applies axial tension to the steel strands when it moves, gradually straightening the steel strands. At the same time, the clamping block 33 inside the horizontal tube 32 applies radial clamping force to the steel strands, helping to eliminate the twisting and bending of the steel strands. When the moving plate 31 moves to the front limit position of the moving part 24, all steel strands are straightened and kept in a straight state. Since the positions of the multiple horizontal tubes 32 are precisely guaranteed by the moving plate 31, the steel strands are naturally in the center position, realizing the dual functions of centering and straightening.

[0071] It is important to note the state of the connecting ring 36 during the tensioning process: the connecting ring 36 is only used in the pre-tensioning preparation stage to drive the moving plate 31 to straighten and center the steel strand. After straightening, the connecting ring 36 is fixedly connected to the slider 34, and the slider 34 is fixedly connected to the moving plate 31, which is then in the locked position at the front end of the moving part 24. During the subsequent tensioning process, the entire moving part 24, including its internal moving plate 31 and horizontal tube 32, will move along with the moving part 24 of the fixed tube 2, and therefore the connecting ring 36 will also move accordingly. In other words, the connecting ring 36 is not fixed, but rather forms a whole with the moving part 24 and the moving plate 31, moving synchronously during the tensioning process.

[0072] A wedge-shaped guide slope 37 is provided at one end of the clamping block 33 near the connecting part 23. When the moving plate 31 moves away from the connecting part 23, the wedge-shaped guide slope 37 gradually comes into contact with the surface of the steel strand. As the moving plate 31 continues to move, the contact pressure between the guide slope 37 and the steel strand increases, forming a wedge-tight fit, thereby preventing the steel strand from retracting before or during tensioning. The working process and working principle of the clamping block 33 are as follows: In the initial threading stage, the steel strand enters the horizontal tube 32 from the direction of the connecting part 23. At this time, due to the guiding effect of the wedge-shaped guide slope 37, the steel strand can smoothly enter the horizontal tube 32 without obstruction. When the moving plate 31 moves towards the tensioning end, the clamping block 33 moves accordingly. Due to the relative motion tendency between the clamping block 33 and the steel strand, the wedge-shaped guide slope 37 generates a radial component force on the surface of the steel strand, causing the clamping block 33 to further tighten the steel strand, forming a self-locking mechanism. This design cleverly utilizes the wedge-shaped force-increasing principle to achieve unidirectional locking of the steel strand, which can only move in the tensioning direction and cannot retract in the opposite direction, providing a reliable initial fixation for subsequent tensioning operations.

[0073] In summary, this invention, through the structure of the fixed pipe 2, its connecting part 23, and the moving part 24, achieves the pre-installation of the tensioning module on the box girder 1; through the straightening mechanism 3, utilizing the synergistic effect of the moving plate 31, the horizontal pipe 32, and the clamping block 33, it achieves the mechanical straightening and precise centering of the steel strand; and through the wedge-shaped guide slope 37 and the clamping block 33, it achieves unidirectional self-locking of the steel strand, preventing retraction. These structures collectively solve the technical problems of difficult centering, complex procedures, and uncontrollable initial state of the steel strand in traditional construction, laying the foundation for subsequent efficient and precise tensioning operations.

[0074] Example 2

[0075] Reference Figure 6 - Figure 9 This is the second embodiment of the present invention, which provides a prestressed tendon tensioning structure for concrete structures, with a focus on a detailed description of the hydraulic tensioning structure 4 and its connection method.

[0076] The hydraulic tensioning structure 4 includes a housing 41 and a connecting sleeve 42 that can move axially relative to the housing 41. The housing 41 is the cylinder part of the jack, with a hydraulic oil chamber and piston inside; the connecting sleeve 42 is the piston rod part of the jack, but unlike a traditional jack, the connecting sleeve 42 of this invention has a hollow cylindrical structure, and its inner diameter matches the outer diameter of the fixed pipe 2, so it can be sleeved on the outside of the fixed pipe 2. The housing 41 is provided with a reaction support structure, which is used to abut against the box girder 1 or external support members during tensioning and bear the tension reaction force. The reaction support structure can adopt various existing technologies, such as support rods, support frames, reaction beams, etc., and the specific form can be selected and designed according to the actual conditions of the construction site and the structural characteristics of the box girder 1. In this embodiment, an adjustable length support rod is preferably used, with one end hinged to the housing 41 and the other end provided with a pad to abut against the top plate of the box girder 1. The length of the support rod can be adjusted to adapt to different tensioning positions.

[0077] The locking mechanism 5 is a key component for achieving rapid connection between the hydraulic tensioning structure 4 and the fixed pipe 2. The locking mechanism 5 includes multiple limiting blocks 51 disposed on the outer wall of the fixed pipe 2, with gaps formed between adjacent limiting blocks 51; multiple connecting blocks 52 are disposed on the inner wall of the connecting sleeve 42, with the positions of the connecting blocks 52 corresponding to the gaps. Specifically, the limiting blocks 51 are evenly distributed along the circumference of the fixed pipe 2, and the connecting blocks 52 are evenly distributed along the circumference of the inner wall of the connecting sleeve 42, with an equal number of each and a one-to-one correspondence in position.

[0078] The working process and principle of the hydraulic tensioning structure 4 are as follows: When tensioning is required, the connecting sleeve 42 is first fitted onto the outside of the fixed pipe 2. During operation, the connecting block 52 on the inner wall of the connecting sleeve 42 is aligned with the interval groove on the outer wall of the fixed pipe 2. Then, the connecting sleeve 42 is pushed axially so that the connecting block 52 completely passes through the interval groove. At this time, the connecting block 52 has passed the position of the limiting block 51. Then, the connecting sleeve 42 is rotated at a certain angle so that the connecting block 52 rotates behind the adjacent limiting block 51. After rotating into position, the connecting block 52 and the limiting block 51 form an abutment fit in the axial direction, that is, the connecting block 52 is blocked by the limiting block 51 and cannot be directly withdrawn axially, thereby realizing the connection between the connecting sleeve 42 and the fixed pipe 2. At this point, the hydraulic system is activated. The hydraulic oil inside the outer casing 41 pushes the piston, which in turn moves the connecting sleeve 42 axially. Since the connecting sleeve 42 is already connected to the fixed pipe 2, the fixed pipe 2 moves accordingly. Through the connecting port 21 at the rear end of the fixed pipe 2, the fixed anchor 12 is driven, thereby pulling the steel strand for tensioning. After tensioning is completed, the connecting sleeve 42 is rotated in the opposite direction to realign the connecting block 52 with the spacer groove, and the connecting sleeve 42 can then be pulled out of the fixed pipe 2, completing the disassembly.

[0079] The design of this locking mechanism 5 has the following advantages: First, the connection and disassembly operations are simple and quick, requiring only two actions: insertion and rotation, without the need for tools, and taking only a few seconds; Second, the connection is reliable, with the connecting block 52 and the limiting block 51 forming a large-area contact in the axial direction, capable of withstanding hundreds of tons of tension; Third, the multiple connecting blocks 52 and limiting blocks 51, which are evenly distributed circumferentially, share the force, resulting in uniform force distribution and avoiding localized stress concentration; Fourth, the structure is simple, easy to process, low in cost, and highly durable, making it suitable for harsh environments at construction sites.

[0080] The specific structures of the limiting block 51 and the connecting block 52 can be further optimized. A guide slope can be provided on the side of the limiting block 51 near the connecting block 52. This guide slope guides the connecting block 52 to smoothly slide into the rear of the limiting block 51 when the connecting sleeve 42 rotates, reducing the risk of jamming. The front end of the connecting block 52 can also be chamfered or rounded to make its contact with the limiting block 51 smoother. Furthermore, in actual use, an elastic locking pin mechanism can be provided between the connecting sleeve 42 and the fixed tube 2. When the connecting sleeve 42 rotates to its position, the elastic locking pin automatically pops out and engages in the positioning hole, preventing the connecting sleeve 42 from accidentally reversing and disengaging during use, further improving the reliability of the connection.

[0081] In summary, this invention, through its hydraulic tensioning structure 4 and its unique locking mechanism 5, enables rapid connection and disassembly between the tensioning jack and the pre-embedded module, greatly simplifying the on-site tensioning operation process and improving construction efficiency. Simultaneously, the coaxial connection between the connecting sleeve 42 and the fixed pipe 2 ensures that the tension force is precisely applied along the design axis, avoiding the axial offset problem caused by traditional multi-component connections.

[0082] Example 3

[0083] Reference Figure 10 The third embodiment of the present invention provides a prestress testing method for a prestressed tendon tensioning structure based on the above-mentioned concrete structure, comprising the following steps:

[0084] Step S1: During the prefabrication stage of box girder 1, the fixing pipe 2 is connected to the fixing anchor 12 through the connecting port 21, and the steel strand is passed through the straightening mechanism 3 inside the fixing pipe 2. The specific construction method is as follows: Anchor plates are installed inside the box girder 1 template, and then the fixing pipe 2 of the present invention is fixedly connected to the anchor plate through the connecting port 21. Then, the steel strand is passed out from the inside of the box girder 1, and sequentially passes through the fixing anchor 12, the connecting part 23 of the fixing pipe 2, and the straightening mechanism 3 in the moving part 24, that is, each horizontal pipe 32 on the moving plate 31. Finally, a certain length is passed out from the front end of the moving part 24 as the tensioning working section.

[0085] Step S2: Pull the connecting ring 36 in the straightening mechanism 3 to move the moving plate 31 away from the connecting part 23. The steel strand is straightened and kept in the center by the clamping block 33 in the horizontal tube 32. Record the initial position of the moving plate 31 at this time as the zero point of displacement measurement.

[0086] The specific construction method is as follows: Workers manually push or pull the connecting ring 36 using simple tools. The connecting ring 36, through the slider 34, drives the moving plate 31 to move along the groove 35 on the inner wall of the moving part 24 towards the tensioning end until the moving plate 31 reaches the limit position at the front end of the moving part 24. During this process, the clamping block 33 inside the horizontal tube 32 applies axial tension and radial clamping force to the steel strand, completely straightening the steel strand and fixing it in the center position. At this time, a mark is made on the moving part 24 or the connecting ring 36, or the current position is recorded using a displacement sensor, which serves as the reference zero point for subsequent elongation measurement.

[0087] Step S3: Place the connecting sleeve 42 of the hydraulic tensioning structure 4 onto the outside of the fixed pipe 2, and connect and lock it through the locking mechanism 5. The specific construction method is as follows: The operator aligns the connecting sleeve 42 of the jack with the fixed pipe 2, aligns the connecting block 52 on the inner wall of the connecting sleeve 42 with the interval groove on the outer wall of the fixed pipe 2, pushes it into place axially, and then rotates the connecting sleeve 42 clockwise by a certain angle, usually 30-45 degrees.

[0088] Step S4: Start the hydraulic tensioning structure 4 to apply tension force to the steel strands. During the tensioning process, monitor the following parameters in real time: tension force value P and displacement value S.

[0089] The monitoring method for the tension force P is as follows: the tension force value is obtained by converting the pressure gauge reading of the jack's hydraulic system into the value, using the formula P = p × Ah, where p is the hydraulic oil pressure and Ah is the effective area of ​​the jack piston. The pressure gauge should be calibrated regularly to ensure accurate readings. Alternatively, a pressure sensor can be installed in the hydraulic system to achieve automatic and continuous acquisition and recording of the tension force.

[0090] The method for monitoring the displacement value S is as follows: a displacement measurement reference point is set on the connecting sleeve 42 or the connecting part 23 of the fixed pipe 2. During tensioning, the axial displacement of the connecting sleeve 42 relative to the connecting part 23 of the fixed pipe 2 is measured by a laser displacement sensor or a mechanical dial indicator. Specifically, a reference bracket can be fixed on the outside of the connecting part 23 of the fixed pipe 2, and the displacement sensor is fixed on the reference bracket with the sensor probe abutting against the end face or side of the connecting sleeve 42. When tensioning, the connecting sleeve 42 moves, and the sensor outputs a displacement signal in real time. Since the connecting part 23 of the fixed pipe 2 is connected to the fixed anchor 12 of the box girder 1, it is an absolutely stationary reference point. The displacement of the connecting sleeve 42 directly reflects the displacement of the moving part 24 of the fixed pipe 2. Since the steel strand has been straightened in step S2, there is no relative sliding between the steel strand and the moving part 24 of the fixed pipe 2. Therefore, the displacement value S is the measured elongation of the steel strand, and there is no need to correct the initial curvature.

[0091] Step S5: When the tension reaches the design value P0, record the corresponding displacement value as the measured elongation S0 of the steel strand. The design value P0 is given by the bridge structure design drawings and is usually the tension corresponding to the anchor control stress. For example, for a steel strand with a nominal diameter of 15.2 mm and a tensile strength of 1860 MPa, the anchor control stress is taken as 0.75 times the tensile strength, i.e., 1395 MPa. The tension of a single steel strand is 1395 MPa × 140 mm. 2 =195.3kN. If a bundle of steel strands consists of 5 strands, then the tension P0 = 5 × 195.3 = 976.5kN.

[0092] Step S6: Calculate the actual prestress value of the steel strand based on P0 and L0, and compare it with the theoretical value to determine whether the tensioning quality is qualified. The theoretical elongation can be calculated according to elastic theory: ΔLt=P0×Ls / (E×As), where Ls is the calculated length of the steel strand, and E is the elastic modulus, usually taken as 1.95×10. 5 MPa, where As is the total cross-sectional area of ​​the steel strand. Compare the measured elongation S0 with the theoretical elongation ΔLt. If the deviation is within the allowable range of the specification, usually ±6%, the tensioning quality is deemed qualified. If the deviation exceeds the allowable range, the cause needs to be investigated, such as excessive duct friction, anchor slippage, or steel strand quality problems, and corresponding measures should be taken.

[0093] The reason for collecting the tension force value P and displacement value S is that prestressing tensioning adopts a dual control principle of stress control and elongation verification. Tension force P is the core parameter to ensure the structure obtains the designed prestress and must be precisely controlled; displacement value S is an important indicator to verify whether the tensioning process is normal, reflecting the combined effects of factors such as duct friction, anchorage retraction, and steel strand quality. Only when both parameters simultaneously meet the requirements can the tensioning quality be guaranteed.

[0094] For example, a 30m box girder has 5 steel strands in the negative bending moment zone. The design tension is P0 = 976.5kN, and the theoretical elongation is ΔLt = 204mm. During tensioning, when the hydraulic pressure gauge reading reaches 50.8MPa, corresponding to P0, the displacement sensor measures S0 = 212mm, with a deviation of (212-204) / 204 = 3.9%, which is within the allowable range of ±6%, and the tensioning quality is considered acceptable. If S0 = 185mm is measured, the deviation is -9.3%, exceeding the allowable range, and the machine must be stopped for inspection.

[0095] The monitoring steps for the locking status of clamping block 33 include: during the tensioning process, real-time monitoring of the relative position or clamping force between clamping block 33 and the steel strand. This can be achieved by installing a miniature displacement sensor or pressure sensor on clamping block 33. When the tension force reaches the design value P0, at the instant the hydraulic tensioning structure 4 is depressurized, monitoring is conducted to determine if clamping block 33 forms a wedge-tight fit with the steel strand, and the locking displacement ΔS is recorded. Locking displacement ΔS refers to the slight retraction of the steel strand from the peak tension to the point of anchoring stability. If ΔS is within the preset range, typically 3-6 mm, the anchoring is considered complete and effective; if ΔS exceeds the preset range, such as greater than 8 mm, the anchoring is considered abnormal, possibly due to slippage of the clamping clips, anchor quality issues, etc., and the system will automatically issue an alarm.

[0096] The reason for collecting the locking displacement ΔS is that anchorage locking is the final critical step in prestressed construction, and the amount of wedge retraction directly reflects the reliability of the anchorage. Traditional methods cannot monitor the instantaneous state of anchorage, and problems are often only discovered during post-construction inspections, at which point it is too late to remedy the situation. This invention utilizes the wedge-shaped guiding slope 37 of the clamping block 33 to automatically form a wedge-tight fit with the steel strand at the moment of pressure relief. By monitoring the minute displacements during this process, real-time monitoring of the anchorage state is achieved, filling the gap in traditional testing methods.

[0097] For example, during one tensioning operation, the locking displacement ΔS = 4.2 mm was detected at the moment of pressure release, which was within the preset range of 3-6 mm, and the system determined that the anchoring was normal. During another tensioning operation, ΔS = 9.8 mm was detected, exceeding the preset range, and the system immediately alarmed. Inspection revealed that the tool anchor clamp was worn, causing slippage. After timely replacement, the anchor was re-tensioned, preventing a quality incident.

[0098] In summary, this invention, through a prestressing testing method based on structural characteristics, utilizes the straightening mechanism 3 to establish a precise zero displacement point, accurately measures elongation using the relative displacement of the structure, and monitors the anchorage status using the characteristics of the clamping block 33. This achieves comprehensive real-time monitoring and quality assessment of the tensioning process, significantly improving the reliability and traceability of prestressed construction.

[0099] As can be seen from Embodiments 1, 2, and 3, the technical solution of the present invention integrates the centering, straightening, and temporary anchoring functions of the steel strand through the pre-embedded fixed pipe 2 and its internal straightening mechanism 3. Simultaneously, the rotating locking mechanism 5, formed by the limiting block 51 on the outer wall of the fixed pipe 2 and the connecting block 52 on the inner wall of the hydraulic tensioning structure 4, enables rapid connection between the tensioning equipment and the pre-embedded module. Furthermore, utilizing the precise initial benchmark and relative structural displacement established by the straightening mechanism 3, accurate testing of the prestress value and real-time monitoring of the anchoring status are simultaneously completed during the tensioning process. The entire process achieves a fully integrated closed loop from steel strand preparation, centering and straightening, rapid tensioning to quality testing.

[0100] The significant advantages of this invention are:

[0101] First, by setting a straightening mechanism 3 consisting of a moving plate 31, a horizontal pipe 32 and a clamping block 33 in the fixed pipe 2, the steel strand is mechanically straightened and forcibly centered before tensioning, which completely eliminates the prestress loss caused by the initial bending and eccentricity of the steel strand in the traditional process. Moreover, no manual visual adjustment is required, and the centering accuracy is guaranteed by the mechanical structure, which greatly improves consistency and reliability.

[0102] Secondly, through the sleeve structure of the connecting part 23 and the moving part 24 of the fixed tube 2, and the sliding cooperation between the guide block 25 at the end of the connecting part 23 and the connecting groove 26 of the moving part 24, the smooth guidance of the moving part 24 on the fixed tube 2 is achieved. This ensures that the moving part 24 can slide smoothly during tensioning, while also restricting the relative rotation between the two, ensuring that the tension force is always accurately applied along the design axis. This solves the problem of insufficient rigidity and easy shaking in traditional multi-component connection systems.

[0103] Third, the rotating locking mechanism 5, formed by the limiting block 51 on the outer wall of the fixed pipe 2 and the connecting block 52 on the inner wall of the hydraulic tensioning structure 4, enables the rapid connection and disassembly of the tensioning jack and the pre-embedded module. Only two actions, insertion and rotation, are required to complete the connection, reducing the preparation time for traditional single-point tensioning from 15-20 minutes to a few seconds. At the same time, the axial abutment of the connecting block 52 and the limiting block 51 can reliably withstand hundreds of tons of tension force, achieving a balance between efficiency and safety.

[0104] Fourth, by utilizing the precise zero displacement point established by the straightening mechanism 3 before tensioning, and the axial displacement measurement of the connecting sleeve 42 relative to the connecting part 23 of the fixed tube 2, high-precision real-time measurement of the elongation of the steel strand is achieved without the need to correct the initial curvature. At the same time, through the locking characteristics of the wedge-shaped guide slope 37 of the clamping block 33 at the moment of pressure relief, real-time monitoring of the anchoring status is achieved, filling the technical gap that traditional methods cannot monitor the anchoring process, and forming a complete integrated solution for tensioning, testing and monitoring.

[0105] The working principle of this invention is as follows:

[0106] First, during the prefabrication stage of box girder 1, the connecting part 23 of the fixed pipe 2 is fixedly connected to the fixed anchor 12 through the connecting port 21, and the steel strand is passed through the straightening mechanism 3 inside the fixed pipe 2; push the connecting ring 36 to drive the moving plate 31 to move away from the connecting part 23. The horizontal pipe 32 on the moving plate 31 gradually straightens the steel strand. At the same time, the clamping block 33 inside the horizontal pipe 32 forms a wedge tight fit with the steel strand using the wedge-shaped guide slope 37 to prevent the steel strand from retracting. At this time, the position of the moving plate 31 is recorded as the zero point for subsequent displacement measurement.

[0107] Secondly, when tensioning is required, the connecting sleeve 42 of the hydraulic tensioning structure 4 is fitted onto the outside of the fixed pipe 2, so that the connecting block 52 on the inner wall of the connecting sleeve 42 is aligned with the spacer groove on the outer wall of the fixed pipe 2 and pushed in axially. Then, the connecting sleeve 42 is rotated so that the connecting block 52 is rotated into the back of the limiting block 51 to form axial abutment, thus achieving a quick connection. After the reaction support structure on the outer shell 41 is abutted and fixed to the box girder 1, the hydraulic system is started. The connecting sleeve 42 drives the moving part 24 of the fixed pipe 2 to move in the tensioning direction as a whole. The fixed anchor 12 is pulled through the connecting part 23 of the fixed pipe 2, thereby applying tension force to the steel strand.

[0108] Secondly, the tension force P and displacement S are monitored in real time during the tensioning process: the tension force P is obtained by converting the hydraulic system pressure; the displacement S is obtained by measuring the axial displacement of the connecting sleeve 42 relative to the connecting part 23 of the fixed pipe 2, and this displacement value is the measured elongation of the steel strand; when the tension force reaches the design value P0, the corresponding elongation is recorded as the measured elongation S0.

[0109] Finally, after tensioning is completed, the hydraulic system is depressurized. At this time, the clamping block 33 and the steel strand are finally locked together under the action of the wedge-shaped guide slope 37. The locking displacement ΔS at the moment of depressurization is recorded. If ΔS is within the preset range, the anchoring is deemed effective; otherwise, an alarm is triggered. The connecting sleeve 42 is rotated in the opposite direction to align the connecting block 52 with the interval groove. The hydraulic tensioning structure 4 is pulled out from the fixed pipe 2, completing all the work of one tensioning point 11. The process can then be repeated to the next pre-embedded module.

[0110] In summary, this invention provides a prestressed tendon tensioning structure for concrete structures, consisting of a pre-embedded fixing pipe 2, a straightening mechanism 3, a rotating locking mechanism 5, and a hydraulic tensioning structure 4. Combined with an integrated testing method based on this structure, it collaboratively achieves mechanical centering and straightening of the steel strands, rapid connection of the tensioning equipment, real-time monitoring of the tensioning process, and automatic determination of the anchorage status. This effectively solves the three major technical bottlenecks in traditional prestressed construction: difficulty in centering, low efficiency, and inaccurate testing, significantly improving the construction quality and efficiency of the negative bending moment zone of continuous box girders.

[0111] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A prestressed tendon tensioning structure of a concrete structure, comprising a box girder (1), the box girder (1) being provided with a plurality of tensioning points (11) at both ends, the tensioning points (11) being provided with fixed anchorage devices (12) for anchoring steel strands, characterized in that: It also includes a fixed pipe (2), one end of which is provided with a connection port (21) for connecting with a fixed anchor (12), a straightening mechanism (3) for straightening and centering the steel strand passing through the fixed pipe (2) is provided in the fixed pipe (2), a slot (22) for installing a movable anchor is provided at the end of the fixed pipe (2) away from the connection port (21), and a hydraulic tensioning structure (4) for tensioning the steel strand is sleeved on the fixed pipe (2).

2. A prestressing tendon tensioning arrangement for a concrete structure according to claim 1, characterised in that: The fixed tube (2) includes a connecting part (23) and a moving part (24). The moving part (24) is sleeved on the outside of the connecting part (23). The moving part (24) can slide along the axial direction of the connecting part (23). A guide block (25) is provided at one end of the connecting part (23) away from the fixed anchor (12). A connecting groove (26) that slides with the guide block (25) is provided at one end of the moving part (24). A locking mechanism (5) for connecting with the hydraulic tensioning structure (4) is provided on the moving part (24).

3. A tendon tensioning arrangement for a concrete structure according to claim 2, characterised in that: The straightening mechanism (3) includes a movable plate (31), which is disposed inside the movable part (24). Multiple horizontal tubes (32) for threading steel strands are fixed on the movable plate (31). Clamping blocks (33) for straightening steel strands are disposed inside the horizontal tubes (32). A slider (34) is disposed on the outer edge of the movable plate (31). A sliding groove (35) is disposed on the inner wall of the movable part (24) for sliding cooperation with the slider (34). A connecting ring (36) for driving the movable plate (31) to move axially along the movable part (24) is sleeved on the outer side of the movable part (24). The connecting ring (36) is fixedly connected to the slider (34).

4. The prestressed tendon tensioning structure for a concrete structure according to claim 3, characterized in that: The clamping block (33) has a wedge-shaped guide slope (37) at one end near the connecting part (23). When the moving plate (31) moves away from the connecting part (23), the guide slope (37) forms a wedge-tight fit with the surface of the steel strand to prevent the steel strand from shrinking back.

5. A prestressed tendon tensioning structure for a concrete structure according to claim 4, characterized in that: The hydraulic tensioning structure (4) includes an outer shell (41) and a connecting sleeve (42) that can move axially relative to the outer shell (41). The connecting sleeve (42) is a hollow cylinder and is sleeved on the outside of the fixed tube (2). The outer shell (41) is provided with a reaction support structure for abutting against the box girder (1) during tensioning.

6. The prestressed tendon tensioning structure for a concrete structure according to claim 5, characterized in that: The locking mechanism (5) includes multiple limiting blocks (51) disposed on the outer wall of the fixed tube (2), and a gap groove is formed between adjacent limiting blocks (51). Multiple connecting blocks (52) are disposed on the inner wall of the connecting sleeve (42), and the position of the connecting blocks (52) corresponds to the gap groove.

7. A prestressed tendon tensioning structure for a concrete structure according to claim 6, characterized in that: The limiting blocks (51) are evenly distributed around the fixed tube (2), and the connecting blocks (52) are evenly distributed around the inner wall of the connecting sleeve (42). When the connecting sleeve (42) is fitted on the outside of the fixed tube (2), the connecting blocks (52) pass through the spacer groove. By rotating the connecting sleeve (42), the connecting blocks (52) rotate behind the limiting blocks (51) and form an abutment fit with the limiting blocks (51) in the axial direction, thereby realizing the connection between the connecting sleeve (42) and the fixed tube (2).

8. A prestressing testing method, implemented based on the prestressing tendon tensioning structure of a concrete structure as described in any one of claims 1-7, characterized in that, Includes the following steps: Step S1: During the prefabrication stage of the box girder (1), the fixing pipe (2) is connected to the fixing anchor (12) through the connecting port (21), and the steel strand is passed through the straightening mechanism (3) inside the fixing pipe (2). Step S2: Pull the connecting ring (36) in the straightening mechanism (3) to move the moving plate (31) away from the connecting part (23). The steel strand is straightened and kept in the center by the clamping block (33) in the horizontal tube (32). Record the initial position of the moving plate (31) at this time as the zero point of displacement measurement. Step S3: Place the connecting sleeve (42) of the hydraulic tensioning structure (4) on the outside of the fixed pipe (2), and connect and lock it through the locking mechanism (5); Step S4: Start the hydraulic tensioning structure (4) to apply tension force to the steel strands. During the tensioning process, monitor the following parameters in real time: Tension force value P: Calculated using hydraulic system pressure; Displacement value S: Measure the axial displacement of the connecting sleeve (42) relative to the fixed pipe (2) or measure the actual displacement of the moving plate (31); Step S5: When the tension reaches the design value P0, record the corresponding displacement value as the measured elongation S0 of the steel strand. Step S6: Calculate the actual prestress value of the steel strand based on P0 and L0, and compare it with the theoretical value to determine whether the tensioning quality is qualified.

9. The prestress testing method according to claim 8, characterized in that, The specific method for real-time monitoring of the displacement value S in step S4 is as follows: A displacement measurement reference point is set on the connection part (23) of the connecting sleeve (42) or the fixed tube (2); During the tensioning process, the axial displacement of the connecting sleeve (42) relative to the connecting part (23) of the fixed tube (2) is measured by a laser displacement sensor or a mechanical dial indicator; The displacement value S is the measured elongation of the steel strand. Since the steel strand has been straightened in step S2, there is no need to correct the initial curvature.

10. The prestress testing method according to claim 9, characterized in that, It also includes a step for monitoring the locking state of the clamping block (33): During the tensioning process, the relative position or clamping force between the clamping block (33) and the steel strand is monitored in real time; When the tension reaches the design value P0, at the instant the hydraulic tensioning structure (4) is depressurized, monitor whether the clamping block (33) forms a wedge tight fit with the steel strand, and record the locking displacement ΔS at this time; If ΔS is within the preset range, the anchoring is deemed complete and effective. If ΔS exceeds the preset range, an anchoring abnormality is determined and an alarm is triggered.

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