Construction method for quickly replacing damaged steel strand of cable-stayed bridge

Abstract

The application relates to the technical field of bridge steel strand construction, in particular to a quick replacement construction method for damaged steel strands of a cable-stayed bridge, a quick replacement construction method for damaged steel strands of a cable-stayed bridge, which comprises the following steps: S1, setting up a falling prevention net: setting up a falling prevention net in a temporary construction lane; S2, replacing a steel strand: unloading the tension of a damaged old steel strand, extracting the old steel strand after unloading the tension, and installing a new steel strand every time one old steel strand is extracted until all the damaged steel strands are replaced; S3, removing the falling prevention net: removing the falling prevention net and completing the construction. The application can realize efficient and safe repair of a super large cable-stayed bridge in a downtown area after the steel strands are damaged.

Description

Technical Field

[0001] This application relates to the technical field of bridge steel strand construction, and more specifically, to a method for rapid replacement of damaged steel strands in cable-stayed bridges. Background Technology

[0002] Cable-stayed bridges are key infrastructure in modern urban transportation systems. Their stay cables are typically composed of multiple high-strength parallel steel strand bundles, offering advantages such as high load-bearing capacity, adjustable cable tension, and relatively convenient maintenance. However, with the increase in service life and the impact of external accidents, some or all of the steel strands in the stay cables may be damaged and need to be replaced.

[0003] In conventional cable-stayed bridge maintenance, replacing the entire cable typically involves large lifting equipment, prolonged traffic closure, and interruption of bridge access, with construction cycles measured in weeks or months. However, for cable-stayed bridges with stranded cable bundle structures, the advantage lies in the ability to partially replace single or a few damaged strands without having to replace the entire cable. However, in actual engineering projects, especially for large cable-stayed bridges located in busy urban areas or on major traffic arteries, even partial replacement at the strand level still faces the following significant technical challenges: Traffic organization and operational windows are severely limited: Bridges located in the city center experience extremely high pedestrian and vehicular traffic on their decks and auxiliary roads, often with multiple lanes, such as eight lanes, making traffic control extremely complex. Traditional steel strand replacement methods require prolonged closure of the work area, but in busy urban areas, traffic cannot be interrupted for extended periods, often limiting the construction window to a few hours at night.

[0004] Working at heights at night carries high risks: To avoid peak traffic hours, the replacement of steel strands is mostly carried out at night, which presents challenges such as poor lighting conditions, large variations in wind load on the bridge deck, and a high risk of falling from heights.

[0005] Therefore, there is an urgent need in this field to provide a construction method for the rapid replacement of damaged steel strands in cable-stayed bridges. Summary of the Invention

[0006] To achieve efficient and safe repair of damaged steel strands on large cable-stayed bridges in urban areas, this application provides a method for rapid replacement of damaged steel strands in cable-stayed bridges.

[0007] This application provides a method for rapid replacement of damaged steel strands in a cable-stayed bridge, which employs the following technical solution: A method for quickly replacing damaged steel strands in a cable-stayed bridge is provided. The bridge deck has multiple lanes and multiple cable stays. The lanes include temporary construction lanes and normal traffic lanes. Construction is carried out in the temporary construction lanes, while normal traffic is allowed in the normal traffic lanes. The construction time is at night. Before construction, safety traffic management and protective equipment are placed. After the construction is completed each night, the equipment occupying the lanes is cleared from the site, and all lanes on the bridge deck are open to normal traffic. The cable-stayed cable includes a sheath and several steel strands installed inside the sheath; The construction method includes the following steps: S1. Installation of fall protection nets: Construction of fall protection nets shall be carried out on the temporary construction lane. S2. Steel strand replacement: Unload the tension of the damaged old steel strand, pull out the old steel strand after unloading the tension, and install a new steel strand for each old steel strand pulled out until all the damaged steel strands are replaced. S3. Removal of the fall protection net: Remove the fall protection net to complete the construction.

[0008] Furthermore, anti-slip clamps are fixedly installed on the undamaged cable stays on both sides of the lane, and the anti-slip clamps are provided with hanging points. The two ends of the fall protection net are respectively hung on the anti-slip clamps on both sides. The fall arresting net includes a first protective net and a second protective net arranged at intervals from top to bottom, with the lowest point of the second protective net being 5-6 meters away from the road surface of the lane.

[0009] Furthermore, after each damaged old steel strand is extracted, it is cut and then subjected to steel strand performance testing. If the test results are satisfactory, only the damaged old steel strand will be replaced. If the test results are unsatisfactory, all the old steel strands shall be replaced.

[0010] Furthermore, the unloading of the tension of the damaged old steel strand, and the extraction of the old steel strand after unloading the tension, specifically includes the following steps: (1) Anchor head cleaning and rust removal: Remove debris from the protective covers and anchor plates at both ends of the steel strands, and remove the bolts of the protective covers. At the same time, remove the waterproof cover on the bridge deck and the shock absorbers at both ends of the steel strands. After opening the protective covers at both ends of the steel strand, clean the anti-corrosion grease inside the anchor cup with cotton yarn, and treat any rusted parts with a file. Wipe the external threads of the anchor cup at the lower end of the steel strand with acetone, and then use diesel fuel to penetrate into the mating position between the nut and the anchor cup along the spiral direction of the external threads of the anchor cup. (2) Tension measurement of a single steel strand in a stay cable: Several steel strands were extracted for pull-out testing to determine the original stress value of the steel strands, which will serve as the basis for tensioning the replacement cables in the future. (3) Remove the single steel strand: Release the tension of each damaged old steel strand one by one, remove the steel strand and pull it out.

[0011] Furthermore, the steel strands to be dismantled were temporarily anchored by an open-type clamping device on the bridge deck instead of being anchored by the beam end anchorage, and then the cable force was unloaded; Use a jack to loosen and remove the clamps at the tower end of the steel strand; Using a winch, the steel strands, after the clips have been removed, are lowered onto the bridge deck; Repeat the above steps until all the damaged steel strands are removed.

[0012] Furthermore, the open clamping device includes an open anchor block, a conical clamp, and an ear plate. The conical clamp is engaged within the open anchor block, and the steel strand to be unloaded passes through the conical clamp and is fixed within the open anchor block. The ear plate is fixedly connected to both sides of the open anchor block, and a through hole is provided on the ear plate.

[0013] Furthermore, the unloading of the cable force includes the following specific steps: Insert the open-type anchor block along the groove into the steel strand to be removed, and install the conical clamp to tighten it. The clamping force generated by the conical clamp is not less than the cable force of the steel strand to be removed. Connect the through holes of the ear plates on both sides to the wire rope of the winch, and start the winch to pre-tighten. The wire rope of the winch is slowly tightened, and the tension of the wire rope is measured with a force gauge until the tension of the wire rope is 5-10KN greater than the original tension of the steel strand. At this time, the tension of the steel strand has been gradually transferred to the wire rope of the winch. Cut the steel strand to be removed near the open clamping device; The winch's wire rope is slowly released until the tension in the steel strand to be dismantled is reduced to zero.

[0014] Furthermore, installing the new steel strand includes the following steps: One end of the steel strand is anchored to the anchorage on the bridge deck; Start the winch to transport the unanchored end of the steel strand from the bottom to the top of the tower. The steel strand is pulled to the tower end, tensioned, and anchored.

[0015] Furthermore, the process of pulling the steel strand to the tower end, tensioning, and anchoring specifically includes the following steps: Before tensioning, power on the jacks and test the machine. The jack is used for tensioning. After tensioning to the specified pressure, the single-hole tool anchor is locked, and the jack is unloaded. Repeat the above steps until tensioning is complete.

[0016] Furthermore, anchorages are provided at both ends of the steel strand, and tension supports are provided at the ends of the anchorages. The exposed length of the tensioned steel strand from the tension supports is not less than 1.45 meters.

[0017] Compared with the prior art, the embodiments of this application have the following main advantages: This application achieves "road occupancy without road closure, and restoration at dawn" by concentrating construction at night, occupying only temporary construction lanes while maintaining normal traffic flow in other lanes, and clearing and restoring all lanes after each night's work. This solves the problem of traditional methods requiring prolonged traffic closures and being unable to adapt to traffic flow in urban core areas. The installation of fall protection nets before construction, covering the temporary construction lane area, provides passive protection for workers during steel strand replacement, effectively reducing the risk of falls from heights due to poor nighttime visibility and changes in wind load on the bridge deck, thus improving the safety of nighttime construction. Attached Figure Description

[0018] To more clearly illustrate the solutions in this application 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 some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Fig. 1 This is a schematic diagram of the anti-fall net structure in an embodiment of this application.

[0020] Fig. 2 This is a schematic diagram of the structure for unloading the tension (cable force) of a single steel strand in an embodiment of this application.

[0021] Fig. 3 This is a schematic diagram illustrating the structure of the open-type clamping device in the embodiments of this application.

[0022] Reference numerals: 1. Open-type clamping device; 101. Open-type anchor block; 102. Conical clamp; 103. Ear plate; 1031. Circular through hole; 2. Beam end anchor; 3. Winch; 4. Wire rope; 5. Guide pulley; 6. Steel strand; 7. Fall protection net; 71. First protective net; 72. Second protective net; 8. Cable stay; 81. Anti-slip lock. Detailed Implementation

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0024] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0026] Reference Figs. 1-3 A method for quickly replacing damaged steel strands in a cable-stayed bridge is described. The bridge deck has multiple lanes and multiple cable stays 8. The lanes include temporary construction lanes and normal traffic lanes. Construction is carried out in the temporary construction lanes, while normal traffic is allowed in the normal traffic lanes. The construction time is at night. Before construction, safety traffic management and protective equipment are placed. After the construction is completed each night, the equipment occupying the road is cleared from the site, and all lanes on the bridge deck are open to normal traffic. The cable 8 includes a sheath and several steel strands 6 disposed inside the sheath; The construction method includes the following steps: S1. Erection of anti-fall net 7: Construction of anti-fall net 7 is carried out on the temporary construction lane. S2, Replacement of steel strand 6: Unload the tension of the damaged old steel strand 6, pull out the old steel strand 6 after unloading the tension, and at the same time, install a new steel strand 6 for each old steel strand 6 pulled out, until all the damaged steel strand 6 are replaced. S3. Removal of safety net 7: Remove the safety net 7 to complete the construction.

[0027] By concentrating construction at night, occupying only temporary construction lanes while keeping other lanes open, and clearing and restoring all lanes after each night's construction, the project achieved "occupancy without road closure and restoration at dawn," solving the problem of traditional methods requiring long-term traffic closures and being unable to adapt to traffic flow in the city's core area.

[0028] Before construction, a fall protection net 7 is erected, and the fall protection net 7 covers the temporary construction lane area. It can provide passive protection for workers during the replacement of steel strand 6, effectively reducing the risk of falling from heights due to poor nighttime light and changes in wind load on the bridge deck, and improving the safety of nighttime construction.

[0029] The process adopts a streamlined operation of "unloading old steel strand 6 → pulling out old wires → immediately inserting new wires". Each time an old wire is pulled out, a new wire is installed. This avoids the disorder inside the sheath tube or the instability of the anchoring system caused by pulling out multiple wires at the same time. It also reduces the waiting time for the process and makes it easier to complete the replacement of multiple damaged steel strands 6 within a few hours at night.

[0030] The replacement of individual strands (rather than removing multiple strands at once) maintained the tension distribution of the remaining steel strands 6 within the stay cable 8, avoiding excessive redistribution of cable force or abnormal stress on the sheath due to large-scale unloading, and reducing the risk of local bridge instability or damage to the sheath during construction.

[0031] The installation of the fall protection net 7 not only protects workers on the bridge, but also prevents steel strands 6 or small tools from falling accidentally, avoiding secondary injuries to auxiliary roads, pedestrians or vehicles below the bridge deck, and meeting the stringent safety and civilized construction requirements of urban areas.

[0032] Furthermore, anti-slip clamps 81 are fixedly installed on the undamaged cable stays 8 on both sides of the lane. The anti-slip clamps 81 are provided with hanging points. The two ends of the fall protection net 7 are respectively hung on the anti-slip clamps 81 on both sides. The fall arresting net 7 includes a first protective net 71 and a second protective net 72 arranged at intervals from top to bottom, with the lowest point of the second protective net 72 being 5-6m away from the road surface of the lane.

[0033] The anti-slip clamp 81 is fixedly installed on the undamaged cable 8. The cable 8 serves as the load-bearing structure, which has high load-bearing capacity and small deformation. The anti-slip clamp 81 can effectively prevent the hanging point from sliding or rotating along the cable surface. It is especially suitable for working environments with large wind changes and obvious vibrations at night, ensuring that the fall protection net 7 is stable in position and provides continuous protection throughout the construction period.

[0034] By adopting a double-layer structure of first protective net 71 (upper layer) + second protective net 72 (lower layer), if personnel or tools accidentally break through the first layer, the second layer can intercept them again; the two layers work together to form a fault tolerance mechanism, providing double buffer against accidental falls caused by factors such as poor light at night and personnel fatigue, making the safety far superior to single-layer protection.

[0035] The second protective net 72 is positioned 5–6 meters above the road surface, balancing buffering effect with traffic safety under the bridge. This height allows for sufficient braking distance, effectively absorbing the impact of a fall before the person / object contacts the road. At the same time, it avoids the protective net being too low and encroaching on the clearance limit of the lane below, without affecting the normal passage of vehicles on the ground auxiliary road. It is suitable for scenarios with dense pedestrian and vehicle traffic under bridges in busy urban areas.

[0036] The anti-slip clamps 81 are only installed on the undamaged cable stays 8 on both sides. The fall protection net 7 is suspended and covers the area directly above the temporary construction lane, rather than covering the entire bridge surface. This ensures the safety of the work area and avoids visual obstruction of adjacent traffic lanes or interference from the swaying of the protective net, which is conducive to the smooth driving of vehicles at night.

[0037] The anti-slip locking clamp 81 can be quickly installed and removed. Combined with the hanging point design, the anti-fall net 7 can be erected or taken down within minutes as the construction progresses. The double-layer net structure is uniformly hung before each night construction and uniformly removed after the construction is completed, leaving no permanent road-occupying facilities, thus meeting the core requirement of "restoring normal traffic on all lanes at dawn".

[0038] Furthermore, after each damaged old steel strand 6 is extracted, it is cut and its performance is tested. If the test results are satisfactory, only the damaged old steel strand 6 will be replaced; If the test results are unqualified, all the old steel strands 6 shall be replaced.

[0039] If the test results are qualified, it means that the other undamaged steel strands 6 still meet the usage requirements. In this case, only the damaged steel strands 6 are replaced, instead of the entire cable 8 or all the steel strands 6. This can significantly reduce the number of replacements, reduce material costs and the amount of nighttime construction work, and complete the replacement of more lines within a limited traffic window.

[0040] Cutting and testing the extracted old steel strands 6 (e.g., mechanical properties, degree of corrosion, broken wires) can reveal performance degradation that is not apparent to the naked eye. If the test results are unsatisfactory, it means that other steel strands 6 in the same batch or under the same working conditions may have deteriorated significantly. In this case, replacing all the old steel strands 6 at once can eliminate the risk of sudden breakage of the entire cable in the future and improve the long-term safety of the bridge.

[0041] Traditional methods often rely on visual inspection or historical records to determine the scope of replacement, which can lead to misjudgments. This solution is based on actual performance data from random sampling: if the performance is satisfactory, partial replacement (precise repair) is performed; if it fails, complete replacement (thorough remediation) is performed.

[0042] If only obviously damaged steel strands (6) are replaced while ignoring the widespread degradation, the remaining steel strands (6) may gradually fail over months or years, leading to frequent nighttime road closures and repeated construction. By immediately replacing all old steel strands (6) when they fail inspection, the potential problems can be resolved in one operation, reducing the long-term disruption to traffic in the downtown area caused by repeated road closures.

[0043] Furthermore, the unloading of the tension of the damaged old steel strand 6, and the extraction of the old steel strand 6 after unloading the tension, specifically includes the following steps: (1) Anchor head cleaning and rust removal: Remove debris from the protective covers and anchor plates at both ends of the steel strand 6, and remove the bolts of the protective covers. At the same time, remove the waterproof cover of the bridge deck and the shock absorbers at both ends of the steel strand 6. After opening the protective covers at both ends of the steel strand 6, clean the anti-corrosion grease inside the anchor cup with cotton yarn, and treat any rusted parts with a file. Wipe the external threads of the anchor cup at the lower end of the steel strand 6 with acetone, and then use diesel fuel to penetrate into the mating position between the nut and the anchor cup along the spiral direction of the external threads of the anchor cup. (2) Measurement of cable tension in 6 single steel strands of the 8-strand cable: Several steel strands 6 were extracted for pull-out testing to determine the stress value of the original steel strands 6, which will serve as the basis for the tensioning of the later replacement of the stay cables 8. (3) Remove single steel strand 6: Release the tension of each damaged old steel strand 6 one by one, remove the steel strand 6 and pull it out.

[0044] By removing the anti-corrosion grease inside the anchor cup, using a file to treat the rusted areas, cleaning the external threads of the anchor cup with acetone, and using diesel fuel to penetrate the mating position between the nut and the anchor cup, the long-term accumulated rust, grease, and solidified grease can be effectively softened or dissolved, preventing jamming and thread engagement failure when loosening the nut or pulling the steel strand 6, and reducing the time lost in dealing with sudden blockages during nighttime construction.

[0045] Before dismantling, several steel strands 6 were sampled for pull-out testing to obtain the actual stress value of the original steel strands 6, which served as the benchmark data for subsequent replacement tensioning. This avoids excessive or insufficient tension of the new steel strands 6 due to unclear original cable force, uneven distribution of cable force within the stay cables 8, and deviations from the design state of the overall cable force after replacement, thereby improving the accuracy of cable force and structural safety after replacement.

[0046] By releasing tension one by one instead of cutting or violently dismantling at once, the stress change of the remaining steel strands 6 in the cable 8 is gradual and predictable, avoiding the sudden increase in instantaneous stress of adjacent steel strands 6 or abnormal slippage of the anchoring system due to sudden unloading of a single strand, thus reducing the risk of subsequent damage.

[0047] Furthermore, the steel strand 6 to be dismantled is temporarily anchored by the open-type clamping device 1 on the bridge deck instead of by the beam end anchorage 2, and then the cable force is unloaded; Use a jack to loosen and remove the clamps at the tower end of the steel strand 6; Using a winch 3, the steel strand 6, after the clips have been removed, is lowered onto the bridge deck; Repeat the above steps until all damaged steel strands 6 are removed.

[0048] By temporarily transferring the anchoring point of the steel strand 6 from the beam end to the open-type clamping device 1 on the bridge deck, the focus of the dismantling operation is shifted from the high-altitude beam end to the bridge deck operation area. This reduces the time that workers spend at the high-altitude beam end and the time spent operating there. In conjunction with the winch 3 to control the wire release speed, the steel strand 6 can be effectively prevented from swinging out of control or falling during the dismantling process, significantly reducing the risk of high-altitude operations at night.

[0049] Temporary anchoring is performed first, followed by unloading the cable force, so that the stress on the steel strand 6 is gradually released rather than suddenly breaking. The tower end is loosened with jacks to avoid the impact load caused by forcibly hitting the wedges from being transmitted to the adjacent steel strands 6 and the anchoring area. This improves the chain reaction of wedge slippage or sudden redistribution of cable force caused by the removal of a single strand, and protects the structural integrity of the remaining steel strands 6 in the stay cable 8.

[0050] Compared to traditional manual chisel hammering, the tower end jack loosening of the clamps is faster and more controllable. The winch 3 releases the wire instead of manual dragging, which is especially suitable for the rapid extraction of long steel strands 6 with large spans (such as exceeding 100m). This significantly shortens the removal time of each steel strand 6, and allows more damaged steel strands 6 to be replaced within the limited nighttime window.

[0051] The mechanical impact of the jacking method on the wedges and anchor holes is much less than that of the hammering method. It can effectively improve the deformation of the anchor hole cone surface, the chipping of the wedge teeth surface or the cracking of the anchor plate, and preserve the integrity and anchoring reliability of the tower end anchor when the new steel strand 6 is installed in the future, reducing the additional cost of anchor repair or replacement.

[0052] The winch 3 lowers the steel strand 6 onto the bridge deck at a controllable speed and constant tension, avoiding plastic bending, wire unraveling, or surface scratches caused by free fall. The extracted steel strand 6 remains straight, facilitating subsequent cutting and sampling for performance testing.

[0053] Reference Fig. 2 Furthermore, the open clamping device includes an open anchor block 101, a conical clamping plate 102, and an ear plate 103. The conical clamping plate 102 is clamped inside the open anchor block 101, and the steel strand 6 to be unloaded passes through the conical clamping plate 102 and is fixed inside the open anchor block 101. The ear plate 103 is fixedly connected to both sides of the open anchor block 101, and a through hole is provided on the ear plate 103.

[0054] The open-type anchor block 101, in conjunction with the conical clamp 102, can directly insert the steel strand 6 without having to insert it from the end and tighten it as is the case with traditional closed anchors. This is especially suitable for steel strands 6 that are already installed inside the stay cable 8 and whose ends cannot be freely pulled out.

[0055] During nighttime construction, workers can temporarily anchor or release a single steel strand within seconds, significantly shortening the unloading preparation time for each strand.

[0056] When the steel strand 6 is under tension, the tapered clamp 102 will generate a self-locking effect: the greater the tension, the stronger the wedging force between the clamp and the tapered hole wall of the open anchor block 101, ensuring that the steel strand 6 will not suddenly slip out during the unloading or relaxation process of the jack, and avoiding the steel strand 6 from popping out and injuring people or damaging adjacent structures due to temporary anchoring failure.

[0057] The through hole on the ear plate 103 can be used for: Connect the jacks to unload the cable tension; Connect a manual hoist or wire rope 4 for fine-tuning of the position; This serves as the turning and fixing point for the traction rope of winch 3.

[0058] This makes the open clamping device not only an anchor but also a multi-functional connection interface, reducing the time spent on frequent tooling changes on site.

[0059] By replacing the tapered clips 102 of different specifications (such as ϕ15.2mm, ϕ15.7mm, etc.), the same open-type anchor block 101 can be matched with a variety of commonly used cable-stayed cable strands 6 models, without the need to customize anchors for each diameter, reducing the complexity of equipment preparation and making it easier to deal with different specifications of cable strands 6 that may exist on the same bridge.

[0060] The contact surface between the tapered clamp 102 and the steel strand 6 is usually designed with fine teeth or sandblasting treatment to provide sufficient friction while avoiding deep tooth marks or stress concentration points; and the temporary anchoring is only used for the dismantling process, and the steel strand 6 is eventually pulled out and replaced, and is not required to be reused. Therefore, it allows for more relaxed surface contact requirements than permanent anchors, simplifies the clamp structure, and reduces manufacturing costs.

[0061] The open-type structure allows workers to install the cable by side-clamping, eliminating the need to lift the end of the steel strand 6 to align with the center hole of the anchor. The ear plate 103 can also serve as a handle or lifting point, making it convenient to hold or suspend the safety rope. This is particularly beneficial for workers operating at night, in windy conditions, or with handheld lighting, reducing the need for auxiliary personnel.

[0062] Furthermore, the unloading of the cable force includes the following specific steps: The open-type anchor block 101 is inserted into the steel strand 6 to be removed along the groove opening, and the conical clamp 102 is installed to press it tight. The clamping force generated by the conical clamp 102 is not less than the cable force of the steel strand 6 to be removed. The through holes of the ear plates 103 on both sides are connected to the wire rope 4 of the winch 3, and the winch 3 is turned on for pre-tightening. The wire rope 4 of the winch 3 is slowly tightened, and the tension of the wire rope 4 is measured with a force measuring instrument until the tension of the wire rope 4 is greater than the original tension of the steel strand 6 by 5-10KN. At this time, the tension of the steel strand 6 has been gradually transferred to the wire rope 4 of the winch 3. Cut the steel strand 6 to be removed near the open clamping device 1. The wire rope 4 of the winch 3 is slowly released until the tension of the steel strand 6 to be dismantled is reduced to zero.

[0063] By gradually tightening the wire rope 4 using winch 3 and measuring the tension in real time, the cable force originally borne by the steel strand 6 is smoothly transferred to the winch 3 system, rather than being released through cutting or sudden loosening. The tension of the wire rope 4 is only 5-10 kN greater than the original cable force, which ensures complete unloading and prevents abnormal stress on adjacent steel strands 6 or deformation of the anchorage zone due to excessive additional tension.

[0064] Cutting is performed when the tension of the steel strand 6 is completely borne by the wire rope 4 of the winch 3. At this time, the internal stress of the steel strand 6 is close to zero. There will be no sudden retraction, wire breakage or ejection during cutting, which greatly reduces the safety threat to operators in high-altitude cutting operations at night.

[0065] It is explicitly required that the clamping force generated by the conical clamp 102 is not less than the original cable force of the steel strand 6 to be removed, so as to ensure that the steel strand 6 is not easy to slip out of the open anchor block 101 during the load transfer process (especially the critical stage when the pull force of the winch 3 just exceeds the original cable force).

[0066] Cut the steel strand 6 near the clamping device, leaving a short distance (usually 10-20cm) between the cut end of the steel strand 6 and the open anchor block 101. This ensures that the end will not get stuck in the sheath when the winch 3 is used to release the wire or when it is manually pulled out. It also makes it easier for the entire steel strand 6 to be smoothly removed after the clamp is loosened at the tower end.

[0067] After the tension is precisely reduced to zero, the steel strand 6 is in a fully relaxed state, at which point the following can be easily completed: The tower end clamps loosen (no residual axial tension, the clamps can be easily removed); The entire steel strand 6 is pulled out from the sheath (without increased frictional resistance); Cut and sample for performance testing (unaffected by residual stress).

[0068] This significantly improves the consistency and repeatability of construction quality in subsequent steps.

[0069] This unloading method uses the winch 3 as the core power source, and is equipped with a portable force gauge and an open clamping device. It is not subject to the strict limitations of the length and spatial angle of the cable 8. Compared with the traditional customized hydraulic synchronous unloading system, the equipment is lightweight, quick to deploy, and more suitable for maintenance scenarios at night, in multiple locations, and with short construction periods.

[0070] The winch, force gauge, and opening clamping device are all small, mobile equipment with a total weight of no more than 200 kg. They have little impact on the local load on the bridge deck, do not require additional reinforcement of the temporary construction lane, and are easy to remove from the site quickly after each day's construction to restore traffic flow.

[0071] Furthermore, installing the new steel strand 6 includes the following steps: One end of the steel strand 6 is anchored to the anchorage on the bridge deck; Start the winch 3 to transport the unanchored end of the steel strand 6 from the bottom to the top of the tower. The steel strand 6 is pulled to the tower end, tensioned, and anchored.

[0072] By placing the anchorage point at the bridge deck end, the tower end is only responsible for tensioning and anchoring, avoiding the complex and coordinated operations required by the traditional "tensioning at both ends" method, which necessitates simultaneous cable threading, anchoring, and tensioning at the tower end. Tower end operators only need to perform actions such as traction, positioning, tensioning, and installing clamps.

[0073] For situations where the tower height is significantly higher than the bridge deck (common cable-stayed bridge tower heights range from 60 to 200 meters) and the stay cables 8 have a large inclination angle, using a winch 3 to pull upwards instead of manually dragging or lowering from the tower top can improve the situation where the steel strands 6 bend, get stuck, or wear the sheath inside the sheath. The uniform speed pulling of the winch 3 also makes it easier to control the steel strands 6 from twisting, reducing the risk of wire strand breakage during installation.

[0074] After one end of the steel strand 6 is anchored on the bridge deck, when the winch 3 pulls the other end upward, the entire steel strand 6 always maintains a certain initial tension and constrains its position to prevent the steel strand 6 from moving back and forth in the sheath tube or slipping out of the tower end hole during the traction process, thus protecting the tower end operators.

[0075] During dismantling, the process involves "temporary anchoring with a clamping device on the bridge deck → winch 3 lowering the line from the tower end to the bridge deck"; during installation, the process involves "permanent anchoring on the bridge deck → winch 3 pulling the line from the bridge deck to the tower end". Both processes use the same set of winch 3, force gauge, and traction steel wire rope 4, only in opposite directions. The equipment does not need to be reconfigured, and construction personnel can quickly master the reverse operation, reducing training costs and changeover time.

[0076] Since the steel strand 6 is packaged in a coil at the factory, it is easy to cause kinking if it is freely laid down from the top of the tower. This solution involves pulling it upwards after anchoring it on the bridge deck. Under the traction force, the steel strand 6 remains in a straight tension state, which can naturally release the residual torsional stress of the coil. After installation, the steel strand 6 has a high straightness, which is conducive to the uniform distribution of cable force in the later stage.

[0077] Before anchoring at the bridge deck end, the tensioning working length can be reserved according to the design drawings and marked on the anchor plate; after the winch 3 pulls to the tower end, the tower end only needs to install the clamps and tension according to the marked position, without the need to adjust the length at the tower end, reducing the high-altitude measurement and cutting operations at the tower end, and improving the installation accuracy and safety.

[0078] When the steel strand 6 is transported upwards from the bridge deck, its path of movement is within the coverage area of ​​the fall arrest net 7 above the temporary construction lane. Even if the steel strand 6 accidentally falls out of the clamp or is shaken by the wind during the traction process, it will fall onto the fall arrest net 7 and will not fall directly onto the bridge deck or the auxiliary road below, forming a closed-loop protection with the double-layer fall arrest net 7 safety system set up in advance.

[0079] Furthermore, the process of pulling the steel strand 6 to the tower end, tensioning, and anchoring specifically includes the following steps: Before tensioning, power on the jacks and test the machine. The jack is used for tensioning. After tensioning to the specified pressure, the single-hole tool anchor is locked, and the jack is unloaded. Repeat the above steps until tensioning is complete.

[0080] Each steel strand 6 has its tension force controlled independently to avoid uneven cable force caused by multiple strands being tensioned simultaneously. At the same time, the jack is unloaded before the next strand is tensioned, which can reduce the impact of tool anchor retraction deformation on adjacent tensioned steel strands 6, making the final anchoring force of each strand closer to the design value.

[0081] Before formal tensioning, a power-on test of the jacks (including the oil pump, pressure gauge, and oil pipes) can detect and resolve issues such as hydraulic system leaks, unstable pressure, abnormal zeroing of the pressure gauge, stuck needles, jack piston creep, or abnormal noises. This avoids sudden equipment failures that could interrupt tensioning or cause safety accidents during high-altitude operations at the tower end, and is especially suitable for working conditions with limited nighttime lighting and inconvenient maintenance.

[0082] After each steel strand is tensioned to the specified pressure, the single-hole tool anchor is immediately locked, so that the wedges engage with the steel strand 6 and bear the tension. Afterwards, when the jack is unloaded, the steel strand 6 will not spring back or slip. Compared with tensioning multiple strands at once and then anchoring them as a whole, this method significantly reduces the cable force loss caused by wedge slippage or anchor plate deformation, achieving both tensioning efficiency and accuracy.

[0083] The sequential tensioning of a single strand allows the load on the tower end anchor plate and the concrete under the anchor to increase gradually, avoiding local stress concentration or anchor plate deflection caused by tensioning multiple strands at once. At the same time, unloading before proceeding with the next strand allows the anchor system a short period of stress adjustment time, which is beneficial to protecting the long-term durability of the tower end anchorage zone.

[0084] The tension value of each new steel strand 6 can be compared with the tension value of the original steel strand 6 at the same location recorded during previous removal (obtained by a force measuring instrument). If the deviation exceeds a reasonable range (e.g., ±5%), the design tension can be checked or adjusted on-site to ensure that the tension distribution of the entire cable after replacement is consistent with the original design or health monitoring benchmark.

[0085] The single-hole tool anchor is small in size and lightweight, allowing for single-person operation. After the jack is unloaded, it can be moved to the next steel strand position 6, eliminating the need to store a large number of tools on the tower top or for multiple people to work together. The entire tensioning and anchoring process requires few tools and involves compact movements, making it suitable for nighttime environments with strong winds, significant vibrations, and limited working space at the tower top.

[0086] Furthermore, anchors are provided at both ends of the steel strand 6, and tension supports are provided at the ends of the anchors. Both the anchors and tension supports are existing technologies, and the exposed length of the tensioned steel strand 6 from the tension supports is not less than 1.45 meters.

[0087] Obviously, the embodiments described above are only some embodiments of this application, not all embodiments. The accompanying drawings show preferred embodiments of this application, but do not limit the patent scope of this application. This application can be implemented in many different forms; rather, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this application's specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the scope of patent protection of this application.

Claims

1. A method for rapid replacement of damaged steel strands in a cable-stayed bridge, characterized in that, The bridge deck is equipped with multiple lanes and multiple cable stays (8). The lanes include temporary construction lanes and traffic lanes. Construction is carried out in the temporary construction lanes, and traffic is allowed to pass normally in the traffic lanes. The construction time is at night. Before construction, safety traffic guidance and protective equipment are placed. After the construction is completed every night, the equipment occupying the road is cleared from the site, and all lanes on the bridge deck are allowed to pass normally. The cable-stayed cable (8) includes a sheath and several steel strands (6) disposed inside the sheath; The construction method includes the following steps: S1. Erection of anti-fall net (7): Construction of anti-fall net (7) is carried out on the temporary construction lane; S2, Steel strand (6) replacement: Unload the tension of the damaged old steel strand (6), pull out the old steel strand (6) after unloading the tension, and at the same time, install a new steel strand (6) for each old steel strand (6) pulled out, until all the damaged steel strands (6) are replaced. S3. Removal of the fall protection net (7): Remove the fall protection net (7) to complete the construction.

2. The construction method for rapid replacement of damaged steel strands in a cable-stayed bridge according to claim 1, characterized in that, Anti-slip clamps (81) are fixedly installed on the undamaged cable stays (8) on both sides of the lane. The anti-slip clamps (81) are provided with hanging points. The two ends of the fall protection net (7) are respectively hung on the anti-slip clamps (81) on both sides. The fall arresting net (7) includes a first protective net (71) and a second protective net (72) arranged at intervals from top to bottom, and the lowest point of the second protective net (72) is 5-6m away from the road surface of the lane.

3. The construction method for rapid replacement of damaged steel strands in a cable-stayed bridge according to claim 1, characterized in that, After each damaged old steel strand (6) is extracted, it is cut and its performance is tested. If the test results are satisfactory, only the damaged old steel strand (6) will be replaced; If the test results are unqualified, all the old steel strands (6) shall be replaced.

4. The construction method for rapid replacement of damaged steel strands in a cable-stayed bridge according to claim 3, characterized in that, The unloading of the tension of the damaged old steel strand (6), and the extraction of the old steel strand (6) after unloading the tension, specifically includes the following steps: (1) Anchor head cleaning and rust removal: Remove the protective covers and anchor plate surface debris from the upper and lower ends of the steel strand (6), and remove the protective cover bolts. At the same time, remove the waterproof cover of the bridge deck and the shock absorbers at the upper and lower ends of the steel strand (6). After opening the protective covers at both ends of the steel strand (6), clean the anti-corrosion grease inside the anchor cup with cotton yarn, and treat any rusted parts with a file. Wipe the external thread of the anchor cup at the lower end of the steel strand (6) with acetone, and then use diesel fuel to penetrate into the mating position of the nut and the anchor cup along the spiral direction of the external thread of the anchor cup. (2) Cable-stayed cable (8) Single steel strand (6) Cable force measurement: Several steel strands (6) were extracted for pull-out testing to detect the stress value of the original steel strands (6), which served as the basis for tensioning the replacement cable (8) in the later stage. (3) Remove the single steel strand (6): Release the tension of each damaged old steel strand (6) one by one, remove the steel strand (6) and pull it out.

5. The method for rapid replacement of damaged steel strands in a cable-stayed bridge according to claim 4, characterized in that, The dismantling of a single steel strand (6) includes the following specific steps: The steel strand (6) to be dismantled was temporarily anchored by the open clamping device (1) on the bridge deck instead of by the beam end anchorage (2), and then the cable force was unloaded. Loosen and remove the clamps of the steel strand (6) at the tower end using a jack; Using a winch (3), the steel strand (6) after the clamps have been removed is placed on the bridge deck; Repeat the above steps until all the damaged steel strands (6) are removed.

6. The construction method for rapid replacement of damaged steel strands in a cable-stayed bridge according to claim 5, characterized in that, The open clamping device includes an open anchor block (101), a conical clamp (102), and an ear plate (103). The conical clamp (102) is clamped inside the open anchor block (101). The steel strand (6) to be unloaded passes through the conical clamp (102) and is fixed inside the open anchor block (101). The ear plate (103) is fixedly connected to both sides of the open anchor block (101), and a through hole is provided on the ear plate (103).

7. The construction method for rapid replacement of damaged steel strands in a cable-stayed bridge according to claim 6, characterized in that, The unloading of the cable force includes the following specific steps: Insert the open-type anchor block (101) along the groove onto the steel strand (6) to be removed, and install the conical clamp (102) to tighten it. The clamping force generated by the conical clamp (102) is not less than the cable force of the steel strand (6) to be removed. The through holes of the ear plates (103) on both sides are connected to the wire rope (4) of the winch (3), and the winch (3) is turned on to pre-tighten. The wire rope (4) of the winch (3) is slowly tightened, and the tension of the wire rope (4) is measured with a force measuring instrument until the tension of the wire rope (4) is greater than the original tension of the steel strand (6) by 5-10KN. At this time, the tension of the steel strand (6) has been gradually transferred to the wire rope (4) of the winch (3). The steel strand (6) to be removed is cut near the open clamping device (1); The wire rope (4) of the winch (3) is slowly released until the tension of the steel strand (6) to be removed is reduced to zero.

8. The construction method for rapid replacement of damaged steel strands in a cable-stayed bridge according to claim 1, characterized in that, The installation of the new steel strand (6) includes the following steps: One end of the steel strand (6) is anchored to the anchorage on the bridge deck; Start the winch (3) to transport the unanchored end of the steel strand (6) from the bottom to the top of the tower. The steel strand (6) is pulled to the tower end, tensioned, and anchored.

9. The construction method for rapid replacement of damaged steel strands in a cable-stayed bridge according to claim 8, characterized in that, The process of pulling the steel strand (6) to the tower end, tensioning and anchoring it specifically includes the following steps: Before tensioning, power on the jacks and test the machine. The jack is used for tensioning. After tensioning to the specified pressure, the single-hole tool anchor is locked, and the jack is unloaded. Repeat the above steps until tensioning is complete.

10. The construction method for rapid replacement of damaged steel strands in a cable-stayed bridge according to claim 8, characterized in that, Anchors are provided at both ends of the steel strand (6), and tension supports are provided at the ends of the anchors. The exposed length of the tensioned steel strand (6) from the tension support is not less than 1.45 meters.

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