A one-time tensioning method for a steel strand stay cable

Abstract

The present application relates to the field of cable-stayed bridge maintenance, and discloses a one-time tension releasing method for steel strand cable-stayed cable, which comprises the following steps: fixing a winch on a bridge deck, and connecting a steel wire rope of the winch with a clamp through a pulley block; clamping the steel strand cable with the clamp, and inversely pulling the steel strand cable with the winch; cutting the steel strand cable when the pulling force of the steel strand cable below the clamping point is less than a set value; slowly unloading the steel strand cable to a pulling force of 0 through the winch after cutting, and then releasing the steel strand cable. The present application can effectively solve the problem that the exposed length of the steel strand cable at the tensioning end cannot be completely released during the removal of the steel strand cable-stayed cable, resulting in an increase in construction procedures and a long construction time.

Description

Technical Field

[0001] This invention relates to the field of cable-stayed bridge maintenance technology, and in particular to a method for one-time tensioning of steel strand cable stays. Background Technology

[0002] As a key load-bearing component of long-span bridges (such as cable-stayed bridges and arch bridges), the installation and dismantling process of stay cables directly affects the construction safety and efficiency of the bridge. In existing stay cable dismantling or replacement projects, the common method is to release the stay cables one strand at a time. However, in practice, limitations such as the exposed length of the stay cables, the working stroke of tensioning equipment (such as jacks), the structure of anchorages, and operating space often make it difficult to achieve complete and synchronous release of individual strands or the entire bundle of stay cables at the tensioning end. This traditional method not only results in a shorter effective stroke per release and a larger number of cycles, but also significantly prolongs the overall construction time and increases costs.

[0003] Therefore, overcoming the problem of tension release under the condition of limited exposed length at the tensioning end has become an urgent technical problem to be solved. Summary of the Invention

[0004] To address the aforementioned problems, the purpose of this invention is to provide a one-time release method for steel strand stay cables, which can effectively solve the problem that the exposed steel strand length at the tensioning end cannot be fully released during the dismantling of steel strand stay cables, resulting in increased construction procedures and excessive time.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for one-time release of a steel strand cable stay, comprising: fixing a winch on the bridge deck, the wire rope of the winch being connected to a clamp via a pulley block; clamping the steel strand with the clamp, using the winch to reverse pull the steel strand, and cutting the steel strand when the tension of the steel strand below the clamping point is less than a set value; after cutting, slowly unloading the steel strand with the winch until the tension is 0, and then releasing it.

[0006] Furthermore, the clamp adopts a two-half symmetrical structure, in which each half includes an ear plate and a tensioning sleeve; the tensioning sleeve is set between the two ear plates, and the middle part of the tensioning sleeve adopts a central hole with a T-shaped cross-section. A single-hole anchor is set in the upper hole, and the steel strand is clamped by the single-hole anchor in conjunction with the clamping plate.

[0007] Furthermore, each half of the clamp has multiple mounting holes on its ear plate. The two halves of the clamp are assembled into one unit by bolts and mounting holes, and the steel strand is clamped by a combination of single-hole anchors and suitable clamping plates.

[0008] Furthermore, the tensioning sleeve is installed between the two ear plates by through-welding.

[0009] Furthermore, before the wire rope is connected to the clamp via the pulley block, the following steps are also included:

[0010] Remove the rainproof cover, steel pipe sleeve, and shock absorber from the bridge deck beam ends; Remove the first preset length of wrapping tape upwards along the pre-embedded pipe at the end of the bridge beam, and then use slings to tightly wrap the entire bundle of steel strands at the second and third preset lengths above the pre-embedded pipe opening at the end of the beam.

[0011] Furthermore, the first preset length is 6-10 meters, the second preset length is 3-5 meters, and the third preset length is 5.5-7 meters.

[0012] Furthermore, the first preset length is 7 meters; the second preset length is 4 meters; and the third preset length is 6.5 meters.

[0013] Furthermore, the steel strand is held in place by a clamp, including: Install a clamping fixture 1.5 meters above the pre-embedded pipe opening. During tensioning, fasten the two halves of the clamp onto the steel strand, allowing the steel strand to pass through the central hole, and tighten the bolts on both sides. Use 12t shackles to thread the steel strand through the two holes above the ear plate and connect them to the pulley block 1.0 meter below. After the single-hole anchor passes through the steel strand, place it inside the sleeve, and insert a clamping plate into the single-hole anchor to hold the steel strand.

[0014] Furthermore, a winch is used to reverse-pull the steel strand until the tension in the steel strand below the clamping point is less than a set value, at which point the steel strand is cut. The specific implementation process includes: After the equipment, tools, and fixtures have been installed, inspected, and verified to be in good condition, and personnel have reached the designated safe position, start the winch to apply tension to the steel strand. When the tension of the steel strand below the clamping point is less than 10kN, extend the cutting machine to cut the steel strand. A force gauge is installed on the wire rope of the winch to determine the timing of cutting by monitoring changes in the force value.

[0015] Furthermore, a force gauge is installed on the winch wire rope to determine the timing of cutting by monitoring changes in force. Specifically, this includes: The first stage involves monitoring changes in force. If the force changes are stable, a single steel strand is completely cut. After cutting six strands at a time, the cut strands are pulled out using a forklift. Once the strands are pulled out, the slings are adjusted, and the remaining strands are rewound tightly. This process of cutting six strands at a time is repeated, and the cut strands are pulled out using a forklift. This process continues until 30 strands have been cut and pulled out, completing the first stage of cutting and lowering. In the second stage, after the first stage of cutting and lowering is completed, 12-16 steel strands remain. The force on the cut steel strands is monitored by the change in the reading of the force gauge on the wire rope to ensure that it does not exceed the measured value of the steel strand tension. At the same time, the number of steel strands to be cut and lowered in the later stages is adjusted according to the reading of the force gauge. Only 3 steel strands can be cut at a time in the second stage, and then a forklift is needed to pull out the cut steel strands. This process is repeated until only 3 steel strands remain to be lowered, completing the second stage of cutting and lowering. In the third stage, after the second stage of cutting and lowering is completed, for the remaining 3 steel strands, the exposed length of the steel strands is first released inside the tower to reduce the cable tension, and then single-strand cutting is adopted. After the cutting is completed, it is pulled out by a forklift. The maximum force of the last steel strand is controlled to not exceed the actual measured value of the steel strand tension.

[0016] The present invention has the following advantages due to the adoption of the above technical solutions: The present invention greatly improves the efficiency of dismantling the steel strand cable stay that cannot be fully tensioned inside the tower, and can save 60% of the dismantling time of this type of cable stay. Attached Figure Description

[0017] Figure 1 This is a schematic diagram illustrating the operation of the one-time tensioning method for the steel strand cable in this embodiment of the invention; Figure 2 This is a schematic diagram of one side of the fixture in an embodiment of the present invention. Detailed Implementation

[0018] 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 described embodiments of the present invention are within the scope of protection of the present invention.

[0019] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0020] In one embodiment of the present invention, a method for one-time tensioning of a steel strand stay cable is provided. In this embodiment, as... Figure 1 As shown, the method includes the following steps: 1) A winch 6 is fixed on the bridge deck, and the wire rope of the winch 6 is connected to the clamp via a pulley block.

[0021] 2) The steel strand is clamped by a fixture, and a winch 6 is used to pull the steel strand back. When the tension of the steel strand below the clamping point is less than a set value, the steel strand is cut. In this embodiment, the steel strand is cut when the tension is less than 10kN. In this embodiment, the position of the clamping point is set according to specific usage requirements.

[0022] 3) After cutting, the 6 pairs of steel strands are slowly unloaded by the winch until the tension is 0, and then lowered.

[0023] In step 1) above, if Figure 2 As shown, the clamp adopts a two-half symmetrical structure, where each half includes an ear plate 1 and a tensioning sleeve 2. The tensioning sleeve 2 is set between the two ear plates 1. The middle part of the tensioning sleeve 2 adopts a central hole with an approximately T-shaped cross-section. A single-hole anchor 3 is set in the upper hole, and the steel strand is clamped by the single-hole anchor 3.

[0024] In this embodiment, each ear plate 1 is provided with multiple mounting holes 5. The two halves of the clamp are installed together by bolts and mounting holes 5, and the steel strand is clamped by a single-hole anchor 3 and a clamping piece. The diameter of the mounting hole 5 at the top of the ear plate 1 is larger than the diameter of the mounting hole 5 at the bottom.

[0025] In this embodiment, the tensioning sleeve 2 is installed between the two ear plates 1 by through-welding.

[0026] In use, the steel strand is clamped by a single-hole anchor 3 and a clamping plate. The single-hole anchor 3 is located inside the tensioning sleeve 2. The steel strand is tensioned downward by the tensioning sleeve 2 pressing against the single-hole anchor 3, thereby transferring the force of the beam end anchor to the winch 6.

[0027] In step 1) above, if Figure 1 As shown, the wire rope of the winch 6 first changes direction through the first reaction point 8 and the first pulley 9, and then forms a pulley group through the second pulley 11 and the third pulley 13 of the second reaction point 10. The angle of the wire rope is adjusted through each reaction point so that the final angle of the pulley group is consistent with the tensioning force angle.

[0028] In this embodiment, the first trolley 9 can be a 5-ton trolley, the second trolley 11 can be two 20-ton double-door trolleys, and the third trolley 13 can be two 10-ton double-door trolleys.

[0029] In step 1) above, before the wire rope is connected to the clamp via the pulley block, the following steps are also included: 1.1) Remove the rainproof cover, steel pipe sleeve, and shock absorber from the bridge deck beam ends; 1.2) Remove the first preset length of wrapping tape upwards along the pre-embedded pipe at the end of the bridge beam. At the second and third preset lengths above the pre-embedded pipe opening at the end of the beam, use slings 7 to tightly wrap the entire bundle of steel strands to prevent the steel strands from breaking under stress when cutting them, which could cause injury to personnel.

[0030] The first preset length is 6-10 meters, and in this embodiment, the first preset length is preferably 7 meters. The second preset length is 3-5 meters, and in this embodiment, the second preset length is preferably 4 meters. The third preset length is 5.5-7 meters, and in this embodiment, the third preset length is preferably 6.5 meters.

[0031] In step 2) above, the steel strand is clamped by a fixture, specifically as follows: A clamping fixture is installed 1.5 meters above the pre-embedded pipe opening. During tensioning, the two halves of the clamp are fastened to the steel strand, allowing the steel strand to pass through the central hole. The clamps are then secured with bolts on both sides. The two uppermost mounting holes 5 of the two ear plates 1 are connected to the pulley block 1.0 meter below by inserting the steel strand through 12t shackles. The single-hole anchor 3 passes through the steel strand and is placed inside the sleeve. A clamping plate is inserted into the single-hole anchor 3 to hold the steel strand.

[0032] In this embodiment, as Figure 1 As shown, the two lugs 1 of the clamp are connected to the 12t shackles of the two 10-ton double-door pulleys of the third trolley 13 below by inserting steel wire ropes with 12t shackles; the two 10-ton double-door pulleys of the third trolley 13 and the two 20-ton double-door fixed pulleys of the second trolley 11 form a pulley group, with the steel wire rope of the pulley group running in 8 tracks; the two 20-ton double-door fixed pulleys of the second trolley 11 are connected to the 20t shackles with two 12t shackles, and the 20t shackles are connected to the second reaction point 10; the first trolley 9, the turning anchor point, is installed below the pre-buried pipe opening of cable #18. The first trolley 9 has a maximum force of 5 tons, and a 5-ton pulley is installed at the first trolley 9; the first reaction point 8 is installed 1 meter behind the pre-buried pipe opening of cable #6 in front of the motor vehicle lane next to the pre-buried pipe opening, with a maximum force of 5 tons (pulling force of 5-ton winch 6), and a 5-ton pulley is installed at the first reaction point 8.

[0033] In step 2) above, the winch 6 is used to reverse pull the steel strand. When the tension of the steel strand below the clamping point is less than the set value, the steel strand is cut. The specific implementation process is as follows: After the equipment, tools, and fixtures have been installed, inspected, and verified to be in good working order, and personnel have reached the designated safe position, start winch 6 to apply tension to the steel strands. When the tension of the steel strands below the clamping point is less than 10kN, extend the cutting machine to cut the steel strands. The maximum tension of a single steel strand is determined based on the actual tension on site. Install a force gauge on the wire rope of winch 6 to determine the timing of cutting by monitoring changes in the force value.

[0034] In this embodiment, a force gauge is installed on the wire rope of winch 6. The timing of cutting is determined by monitoring changes in the force value. Specifically: In the first stage, try cutting a few steel wires and monitor the change in force. Once the force is stable (for example, when the force reaches 1kN, it indicates that the force is stable), you can completely cut a steel strand. After cutting 6 strands at a time, use a 3-ton forklift to pull out the cut steel strands. After the steel strands are pulled out, adjust the slings and rewrap the remaining steel strands tightly to prevent them from breaking apart and injuring people later. Repeat the process of cutting 6 steel strands at a time and pulling out the cut steel strands with a forklift until 30 steel strands have been cut and pulled out, thus completing the first stage of cutting and lowering.

[0035] In the second stage, after the first stage of cutting and lowering, 12-16 steel strands remain. Due to the sag and weight of the remaining strands, the stress on them begins to increase. The stress on the cut strands is monitored by changing the readings of the dynamometer on the wire rope to ensure it does not exceed the measured tensile strength. Simultaneously, the number of strands cut and lowered in subsequent stages is adjusted based on the dynamometer readings. Only 3 strands can be cut at a time in the second stage, and then a forklift is used to pull out the cut strands. This process is repeated until only the last 3 strands remain, completing the second stage of cutting and lowering.

[0036] In the third stage, after the second stage of cutting and lowering, the remaining three steel strands are significantly affected by factors such as the wrapping tape, the weight of the strands themselves, and sag. Therefore, the force on the last three remaining steel strands is relatively large. At this point, a strand of exposed elongation (25-30cm) can be placed inside the tower to reduce the force on the last three strands. Then, a single strand can be cut, and the strands can be pulled out using a forklift after cutting. For the last steel strand, its maximum force must be controlled to not exceed the measured tensile strength of the steel strand.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for one-time tensioning of a steel strand cable stay, characterized in that, include: A winch is fixed on the bridge deck, and the winch's wire rope is connected to a clamp via a pulley block. The steel strand is clamped by a clamp and then pulled back by a winch. When the tension of the steel strand below the clamping point is less than the set value, the steel strand is cut. After cutting, the steel strand is slowly unloaded by a winch until the tension is 0, and then lowered.

2. The method for one-time tensioning of a steel strand cable as described in claim 1, characterized in that, The clamp adopts a two-half symmetrical structure, in which each half includes an ear plate and a tensioning sleeve. The tensioning sleeve is set between the two ear plates. The middle part of the tensioning sleeve has a central hole with a T-shaped cross-section. A single-hole anchor is set in the upper hole to clamp the steel strand.

3. The method for one-time tensioning of a steel strand cable as described in claim 2, characterized in that, Each half of the clamp has multiple mounting holes on its ear plate. The two halves of the clamp are assembled into one piece by bolts and mounting holes, and the steel strand is held by a combination of single-hole anchors and suitable clamping plates.

4. The method for one-time tensioning of a steel strand cable as described in claim 2, characterized in that, The tensioning sleeve is installed between the two ear plates by through-welding.

5. The method for one-time tensioning of a steel strand cable as described in claim 1, characterized in that, Before the wire rope is connected to the clamp via the pulley block, the following is also included: Remove the rainproof cover, steel pipe sleeve, and shock absorber from the bridge deck beam ends; Remove the first preset length of wrapping tape upwards along the pre-embedded pipe at the end of the bridge beam, and then use slings to tightly wrap the entire bundle of steel strands at the second and third preset lengths above the pre-embedded pipe opening at the end of the beam.

6. The method for one-time tensioning of a steel strand cable as described in claim 5, characterized in that, The first preset length is 6 to 10 meters, the second preset length is 3 to 5 meters, and the third preset length is 5.5 to 7 meters.

7. The method for one-time tensioning of a steel strand cable as described in claim 6, characterized in that, The first preset length is 7 meters; the second preset length is 4 meters; and the third preset length is 6.5 meters.

8. The method for one-time tensioning of a steel strand cable as described in claim 1, characterized in that, Holding the steel strand with clamps includes: Install a clamping fixture 1.5 meters above the pre-embedded pipe opening. During tensioning, fasten the two halves of the clamp onto the steel strand, allowing the steel strand to pass through the central hole. Use 12t shackles to pass through the two holes above the ear plate and connect them to the pulley block 1.0 meter below. After the single-hole anchor passes through the steel strand, place it inside the sleeve. Insert a clamping piece into the single-hole anchor to hold the steel strand.

9. The method for one-time tensioning of a steel strand cable as described in claim 1, characterized in that, A winch is used to reverse pull the steel strand. When the tension in the steel strand below the clamping point is less than a set value, the steel strand is cut. The specific implementation process includes: After the equipment, tools, and fixtures have been installed, inspected, and verified to be in good condition, and personnel have reached the designated safe position, start the winch to apply tension to the steel strand. When the tension of the steel strand below the clamping point is less than 10kN, extend the cutting machine to cut the steel strand. A force gauge is installed on the wire rope of the winch to determine the timing of cutting by monitoring changes in the force value.

10. The method for one-time tensioning of a steel strand cable as described in claim 9, characterized in that, Installing a force gauge on the winch wire rope and determining the timing of cutting by monitoring changes in force value, specifically includes: The first stage involves monitoring changes in force. If the force changes are stable, a single steel strand is completely cut. After cutting six strands at a time, the cut strands are pulled out using a forklift. Once the strands are pulled out, the slings are adjusted, and the remaining strands are rewound tightly. This process of cutting six strands at a time is repeated, and the cut strands are pulled out using a forklift. This process continues until 30 strands have been cut and pulled out, completing the first stage of cutting and lowering. In the second stage, after the first stage of cutting and lowering is completed, 12-16 steel strands remain. The force on the cut steel strands is monitored by the change in the reading of the force gauge on the wire rope to ensure that it does not exceed the measured value of the steel strand tension. At the same time, the number of steel strands to be cut and lowered in the later stages is adjusted according to the reading of the force gauge. Only 3 steel strands can be cut at a time in the second stage, and then a forklift is needed to pull out the cut steel strands. This process is repeated until only 3 steel strands remain to be lowered, completing the second stage of cutting and lowering. In the third stage, after the second stage of cutting and lowering is completed, for the remaining 3 steel strands, the exposed length of the steel strands is first released inside the tower to reduce the cable tension. Then, the steel strands are cut one by one. After the cutting is completed, they are pulled out by a forklift. The maximum force of the last steel strand is controlled to not exceed the measured value of the steel strand tension.

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