Method for dismantling of steel strand cable stayed cable in intermediate tension

Abstract

The application discloses a steel strand inclined cable intermediate tensioning and dismantling method, which adopts a method of tensioning and dismantling steel strands one by one to realize cable force tensioning of the whole cable; one steel strand to be dismantled is divided into an upper segment L1, a middle segment L2 and a lower segment L3 by two sets of clamping devices; two tool steel strands are correspondingly passed through left and right holes of the two clamping devices and anchored by clamping pieces; the middle segment L2 of the steel strand to be dismantled between the two clamping devices is gradually loosened and cut by a jack tensioning; the upper segment L1 and the lower segment L3 of the steel strand to be dismantled outside the clamping devices are loosened, and a crane hoists away the upper and lower steel strand cable bodies respectively. The application solves technical problems of the prior art, such as insufficient length of old steel strands in long-span cable-stayed bridge steel strand cable replacement construction, high safety risk of high-altitude tower operation, great construction difficulty and low economic applicability.

Description

Technical Field

[0001] This invention relates to the field of cable-stayed bridge maintenance, specifically to methods for removing steel strand cables, old outer sheaths and old anchorages, and installing new cables in long-span cable-stayed bridges. Background Technology

[0002] Since the beginning of the 21st century, my country's infrastructure industry has developed rapidly, and bridges, as an important transportation facility, have been widely constructed. Cable-stayed bridges, as an important bridge type, can achieve large spans and are therefore built in large numbers. However, during the operation of cable-stayed bridges, under the long-term load and adverse external environmental factors, the stay cables may suffer from defects such as PE sleeve rupture, severe corrosion of steel strands, and even cable breakage, endangering the safety of the bridge.

[0003] Steel strand cable systems offer advantages such as single-strand hanging and tensioning, multiple protection mechanisms, and miniaturized construction equipment. Therefore, they are widely used in cable-stayed bridge cables, external prestressed tendons, hangers, and tie rods, as seen in projects like the Wuhan Erqi Bridge, the Yibin Nanxi Yangtze River Bridge, and the Wuhu Yangtze River Bridge No. 2. While significant progress has been made in steel strand cable technology over the years, research on steel strand cable removal and replacement techniques remains lacking in China.

[0004] The replacement of stay cables with steel strands is the reverse process of the original installation. The first step in replacement is to remove the current tension on the steel strands, which requires releasing the elastic elongation ΔL of the steel strands under the current tension. During the original cable installation, it was essential to ensure sufficient allowance L1 behind the anchorage. Considering the tooling connection during steel strand replacement, L1 should be greater than ΔL by a certain length. This is a crucial technical measure concerning the ease of future steel strand replacement. However, in actual construction, operators often prioritize convenience and do not cut the steel strands according to requirements, cutting them into a "stepped" shape. This results in the allowance Li of the upper steel strands being less than the normal allowance L1, or even shorter than the elastic elongation ΔL under tension, leading to difficulties in future steel strand replacement. Summary of the Invention

[0005] The purpose of this invention is to provide a method for dismantling and releasing the tension of steel strand cable stays in the middle, so as to solve the technical problems existing in the prior art, such as insufficient length of old steel strands during the replacement of steel strand cables in large-span cable-stayed bridges, high safety risks of working inside high-altitude towers, high construction difficulty, and low economic applicability.

[0006] The technical solution adopted by the present invention to solve this technical problem is: a method for releasing tension and dismantling the middle of a steel strand cable, characterized in that the tension of the entire cable bundle is released by releasing tension and dismantling the steel strands one by one.

[0007] Preferably, it includes the following steps:

[0008] S1. Remove the old outer sleeve at the bridge deck and install two sets of clamping devices on the steel strand to be removed at the bridge deck. The two sets of clamping devices divide the steel strand to be removed into the upper section L1, the middle section L2 and the lower section L3.

[0009] S2. Use tool steel strands to pass through the two clamping devices and anchor them with clamps to ensure that there is at least one tool steel strand on each side of the steel wire to be removed.

[0010] S3. Using jacks, simultaneously tension the two tool steel strands of any one set of clamping devices. The other set of clamping devices is firmly anchored. Tensioning in stages causes the middle section L2 of the steel strand to be removed between the two clamping devices to gradually loosen. After the tension of the middle section L2 steel strand is loosened, select a suitable position in the length of the middle section L2 to cut the steel strand to be removed.

[0011] S4. After the L2 steel strand in the middle section of the two clamping devices is cut, the two jacks return to oil, and the upper L1 and lower L3 steel strands to be removed outside the clamping devices are gradually loosened. The cut ends of the upper L1 and lower L3 are lifted by the crane, and the anchor at the tower end and the anchor at the beam end are removed. The crane lifts the upper and lower steel strand bodies respectively.

[0012] S5. Repeat steps S1 to S4 to remove the steel strands one by one or group by group until all the steel strands of the entire cable bundle are removed.

[0013] Preferably, it also includes: S6, removing the old anchorage at the beam end by means of a truck crane, and removing the old anchorage at the tower end by means of a winch.

[0014] Preferably, it also includes: S7, firstly, installing the new tower end anchorage and beam end anchorage, and using the method of tensioning and anchoring the steel strands one by one to achieve the installation of the entire bundle of new cables.

[0015] Preferably, the device further includes: the clamping device having at least three through-axial conical holes, including at least one open conical hole and at least two closed conical holes, the top surface of the open conical hole having a through-axial groove, and the two closed conical holes being symmetrically arranged on both sides of the open conical hole; a set of conical clamping pieces are installed in each of the three conical holes, the outer wall taper of the conical clamping pieces being consistent with the inner wall taper of the conical hole.

[0016] Preferably, step S1 includes:

[0017] S11. Insert the middle open conical hole of the two bridge deck clamping devices into the steel strand to be removed along the groove. Adjust the angle and position of the open anchor block to ensure that the groove is facing upward, the large hole of the conical hole of one clamping device is facing upward, the large hole of the conical hole of the other clamping device is facing downward, and the steel strand is located at the center of the conical hole.

[0018] S12. Two clamping devices divide a steel strand to be dismantled into an upper section L1, a middle section L2, and a lower section L3.

[0019] Preferably, step S2 includes:

[0020] Adjust the spatial relative position of the two clamping devices so that the three conical anchor holes of the two clamping devices are all on three parallel lines. The middle open conical hole is used to fit the steel strand to be removed, and the left and right closed conical holes are used to install the tool steel strand. Then, a set of conical clamping plates are installed in each of the three conical holes to press them together.

[0021] Preferably, step S3 includes:

[0022] S31. Use jacks to synchronously and grade the tool steel strands, and use dual index control of cable force and elongation. By tensioning the tool steel strands on both sides, eliminate the elastic elongation △L2 of the middle section L2 of the cable to be dismantled, realize the cable force unloading of the middle section L2 of the steel strand to be dismantled, and complete the cutting of the old steel strand after tensioning until L2 relaxes.

[0023] The determination of tension force needs to take into account the original free length between tensioning anchors and the stress loss during connector connection.

[0024] Preferably, in step S5, when removing the steel strands one by one, the removal is carried out in the order of top layer to bottom layer.

[0025] Preferably, step S6 further includes cleaning the residual mortar inside the cable saddle wire splitter tube.

[0026] In step S7, the installation of the new cable begins with the installation of the tower-end anchorage and beam-end anchorage, followed by on-site welding of the HDPE sleeve. The first steel strand is then passed through the beam-end anchorage and the HDPE sleeve. The HDPE sleeve and the end of the steel strand are then hoisted to the tower end and anchored using the tower top gantry. The clamps at both ends of the first steel strand are installed and tensioned to the design value. The installation of other steel strands is performed using a cyclic traction system.

[0027] The present invention has at least the following beneficial effects:

[0028] (1) During the installation of steel strand stay cables, after tensioning and anchoring grouting, the remaining length of the steel strand at the anchoring end is generally insufficient to meet the length required for tensioning during subsequent cable replacement. This method uses two clamping devices to release the cable force of the steel strand to be dismantled within the clamping range, and can be performed at any position on the cable body without being limited by the remaining length of the steel strand at the original cable anchoring end.

[0029] (2) The present invention can control the maximum tension force required by independently setting the distance between the two clamping devices while ensuring the safety of the original structure under stress, thereby reducing the difficulty and risk of tensioning construction.

[0030] (3) This invention can replace the partial steel strand cable to be removed with two tool steel strands while ensuring the safety of the original structure under stress, so as to realize the cutting of the old cable and solve the technical problem that the steel strand cable with epoxy mortar in the anti-slip device cannot be replaced.

[0031] (4) This method uses the method of releasing tension on the entire cable bundle by dismantling the steel strands one by one in a localized manner. It does not require large tensioning and releasing equipment, which not only saves construction space but also saves construction costs.

[0032] (5) This invention changes the traditional tower end release and dismantling method, greatly reduces the risk of high-altitude operation, and is simple and convenient to operate, with low manual labor intensity, high efficiency, fast construction progress, safety and reliability, and easy to standardize construction.

[0033] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the clamping device of the present invention;

[0035] Figure 2 for Figure 1 Cross-sectional view of the clamping device (1-1);

[0036] Figure 3 This is a schematic diagram of the overall construction process for dismantling the stay cables using the method of this invention;

[0037] Figure 4 for Figure 3 Enlarged schematic diagram of section A of the overall construction;

[0038] Figure 5 for Figure 3 Enlarged schematic diagram of section B of the overall construction project.

[0039] In the attached image:

[0040] 1—Clamping device; 101—Open anchor block; 102—Open conical hole; 103—Closed conical hole; 104—Slot; 105—Conical clamp; 106—Clamping device A; 107—Clamping device B; 2—Tool steel strand; 3—Steel strand to be removed; 301—Upper section L1; 302—Middle section L2; 303—Lower section L3; 4—Jack; 5—P-type anchor. Detailed Implementation

[0041] The present invention will now be described in detail and completely with reference to the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention with reference to the accompanying drawings, it should be particularly noted that the technical solutions and features provided in various parts of the present invention, including the following description, can be combined with each other without conflict.

[0042] Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific implementation process is as follows:

[0044] like Figures 1-5 As shown, the present invention provides a method for releasing tension and dismantling the middle of a steel strand cable, which achieves tension release of the entire cable bundle by releasing tension and dismantling the steel strands one by one.

[0045] This technical solution may also include the following technical details to better achieve the technical effect: including the following steps:

[0046] S1. Open and remove the old outer sleeve at the bridge deck in sections. Install two sets of clamping devices 1 on the bridge deck of the steel strand 3 to be removed. The middle hole of the anchor plate is an open conical hole 102, which is connected to the steel strand 3 to be removed. The two sets of clamping devices 1 divide the steel strand to be removed into the upper section L1 301, the middle section L2 302 and the lower section L3 303.

[0047] S2. The three-hole anchor plates of the upper and lower clamping devices 1 are arranged at a certain distance. Two tool steel strands 2 are passed through the left and right holes of the two clamping devices 1 respectively and anchored with clamping plates.

[0048] S3. Using two jacks 4, simultaneously tension the two tool steel strands 2 of any one set of clamping devices 1. The other set of clamping devices 1 is firmly anchored with P-type anchors 5. Tensioning in stages causes the middle section L2302 of the steel strand 3 to be removed between the two clamping devices 1 to gradually loosen. After the tension of the steel strand in the middle section L2302 is loosened, a suitable position is selected in the length of the middle section L2302 to cut the steel strand 3 to be removed.

[0049] S4. After cutting the steel strand L2 302 in the middle section of the two clamping devices 1, the two jacks return to oil, and gradually loosen the upper section L1 301 and lower section L3 303 steel strands to be removed outside the clamping devices 1. Use a crane to lift the cut ends of the upper section L1 301 and lower section L3 303, remove the anchor at the tower end of the cable and the anchor at the beam end, and the crane removes the upper and lower sections of the steel strand body respectively.

[0050] S5. Repeat steps S1 to S4 to remove the steel strands one by one until all the steel strands of the entire cable bundle are removed.

[0051] This technical solution may also include the following technical details to better achieve the technical effect: S6, removing the old anchorage at the beam end by using a truck crane and removing the old anchorage at the tower end by using a winch.

[0052] This technical solution may also include the following technical details to better achieve the technical effect: S7, First, install the new tower end anchorage and beam end anchorage, and use the method of tensioning and anchoring the steel strands one by one to achieve the installation of the entire bundle of new cables.

[0053] This technical solution may also include the following technical details to better achieve the technical effect: It further includes: the clamping device 1 has three through-axial conical holes, including one open conical hole 102 and two closed conical holes 103. The top surface of the open conical hole 102 has a through-axial groove 104, and the two closed conical holes 103 are symmetrically arranged on both sides of the open conical hole 102; a set of conical clamping pieces 105 are installed in each of the three conical holes, and the outer wall taper of the conical clamping piece 105 is consistent with the inner wall taper of the conical hole. The clamping device 1 is not limited to having only one open conical hole 102; two sets of clamping devices 1 can simultaneously replace multiple steel strands to be removed. When multiple steel strands need to be removed, multiple sets of conical holes are set on the clamping device 1 according to the position of the steel strands to be removed, each set of conical holes consisting of one open conical hole 102 and two closed conical holes 103.

[0054] This technical solution may also include the following technical details to better achieve the technical effect: Step S1 includes:

[0055] S11. Insert the middle open conical holes 102 of the two bridge deck clamping devices 1 into the steel strand to be removed along the slot 104. Adjust the angle and position of the open anchor block 101 to ensure that the slot 104 faces upward (or temporarily seal the slot 104). The large hole of the conical hole of one clamping device A106 faces upward, and the large hole of the conical hole of the other clamping device B107 faces downward, with the steel strand located at the center of the conical hole. Install the conical clamping piece 105 to press it tight, ensuring that the clamping force it generates is not less than the cable force of the steel strand.

[0056] S12. Two clamping devices 1 divide a steel strand to be dismantled into an upper section L1 301, a middle section L2 302 and a lower section L3 303. The distance L2 between the two clamping devices 1 should not be too long, otherwise the tension required to eliminate the elastic elongation ΔL2 of the middle section L2 302 of the cable to be dismantled will increase, which is not conducive to safe operation.

[0057] This technical solution may also include the following technical details to better achieve the technical effect: Step S2 includes:

[0058] Adjust the spatial relative positions of the upper and lower clamping devices A106 and B107 so that the three conical anchor holes of the two clamping devices 1 are all on three parallel lines. The middle open conical hole 102 is used to fit the steel strand to be removed, and the left and right closed conical holes 103 are used to install the tool steel strand 2. Then, a set of conical clamping plates 105 are installed in each of the three conical holes to press them together.

[0059] This technical solution may also include the following technical details to better achieve the technical effect: Step S3 includes:

[0060] S31. Use jack 4 to simultaneously tension tool steel strand 2 in stages. The purpose is to eliminate the elastic elongation ΔL2 of the middle section L2 302 of the cable to be dismantled by tensioning tool steel strand 2 on both sides, thereby unloading the cable force of the middle section L2 302 of the cable to be dismantled. After tensioning to L2 relaxation, the old steel strand is cut.

[0061] The determination of tension force needs to take into account the original free length between tensioning anchors and the stress loss when the connector is connected. Over-tensioning is required, which means increasing the tension force. At the same time, the bridge deck should be monitored to prevent excessive deformation of the bridge deck at the cable beam end.

[0062] This technical solution may also include the following technical details to better achieve the technical effect: In step S5, when removing the steel strands one by one, they are removed one by one in the order of top layer to bottom layer.

[0063] This technical solution may also include the following technical details to better achieve the technical effect: step S6 also includes cleaning the residual mortar inside the cable saddle wire splitter tube.

[0064] In step S7, the installation of the new cable begins with the installation of tower-end anchorages and beam-end anchorages, followed by on-site welding of HDPE sleeves. The first steel strand is then passed through the beam-end anchorage and the HDPE sleeve. The HDPE sleeve and the end of the steel strand are hoisted to the tower end and anchored using the tower top gantry. The clamps at both ends of the first steel strand are installed and tensioned to the design value. The installation of other steel strands is carried out using a circulating traction system.

[0065] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for dismantling a steel strand cable with intermediate tension, characterized in that, The tension of the entire cable bundle is released by removing the steel strands one by one. Includes the following steps: S1. Remove the old outer sheath at the bridge deck, and install two sets of clamping devices on the steel strand to be removed at the bridge deck. The two sets of clamping devices divide the steel strand to be removed into an upper section L1, a middle section L2, and a lower section L3; step S1 includes: S11. Insert the middle open conical hole of the two bridge deck clamping devices into the steel strand to be removed along the groove. Adjust the angle and position of the open conical hole to ensure that the groove is facing upward, the large hole of the conical hole of one clamping device is facing upward, the large hole of the conical hole of the other clamping device is facing downward, and the steel strand is located in the center of the conical hole. S12. Two clamping devices divide a steel strand to be removed into an upper section L1, a middle section L2 and a lower section L3. S2. Use tool steel strands to pass through the two clamping devices and anchor them with tapered clips to ensure that there is at least one tool steel strand on each side of each steel strand to be removed. S3. Using jacks, simultaneously tension the two tool steel strands of any one set of clamping devices. The other set of clamping devices is firmly anchored. Tensioning in stages causes the middle section L2 of the steel strand to be removed between the two clamping devices to gradually loosen. After the tension of the middle section L2 steel strand is loosened, select a suitable position in the length of the middle section L2 to cut the steel strand to be removed. Specifically: S31, use jacks to synchronously and grade the tool steel strands, and use the dual index control of cable force and elongation. By tensioning the tool steel strands on both sides, the elastic elongation △L2 of the middle section L2 of the cable to be dismantled is eliminated, thereby unloading the cable force of the middle section L2 of the steel strand to be dismantled. After tensioning until the middle section L2 relaxes, the old steel strand is cut. The determination of tension force needs to take into account the original free length between tensioning anchors and the stress loss when the connector is connected. S4. After the L2 steel strand in the middle section of the two clamping devices is cut, the two jacks return to oil, and the upper L1 and lower L3 steel strands to be removed outside the clamping devices are gradually loosened. The cut ends of the upper L1 and lower L3 are lifted by the crane, and the anchor at the tower end and the anchor at the beam end are removed. The crane lifts the upper and lower steel strand bodies respectively. S5. Repeat steps S1 to S4 to remove the steel strands one by one until all the steel strands of the entire cable bundle are removed. The clamping device has at least three through-axial conical holes, including at least one open conical hole and at least two closed conical holes. The top surface of the open conical hole has a through-axial groove, and the closed conical holes are symmetrically arranged on both sides of the open conical hole. A set of conical clamping pieces is installed in each conical hole, and the outer wall taper of the conical clamping piece is consistent with the inner wall taper of the conical hole. In step S5, when removing the steel strands one by one, they are removed one by one in the order from the top layer to the bottom layer.

2. The method for dismantling and releasing intermediate tension of a steel strand cable as described in claim 1, characterized in that, Also includes: S6. Remove the old anchorages at the beam ends using a truck crane and the old anchorages at the tower ends using a winch.

3. The method for releasing and dismantling the intermediate tension of a steel strand cable as described in claim 2, characterized in that, Also includes: S7. First, install the new tower end anchorage and beam end anchorage, and use the method of tensioning and anchoring the steel strands one by one to achieve the installation of the entire new cable bundle.

4. The method for dismantling and releasing intermediate tension of a steel strand cable as described in claim 1, characterized in that, Step S2 includes: Adjust the spatial relative position of the two clamping devices so that the three conical holes of the two clamping devices are all on three parallel lines. The middle open conical hole is used to fit the steel strand to be removed, and the left and right closed conical holes are used to install the tool steel strand. Then, a set of conical clamping plates are installed in each of the three conical holes to press them together.

5. The method for releasing and dismantling the intermediate tension of a steel strand cable as described in claim 3, characterized in that, Step S6 also includes cleaning the residual mortar inside the cable saddle wire splitter tube; In step S7, the installation of the new cable begins with the installation of tower-end anchorages and beam-end anchorages, followed by on-site welding of HDPE sleeves. The first steel strand is then passed through the beam-end anchorage and the HDPE sleeve. The HDPE sleeve and the end of the steel strand are hoisted to the tower end and anchored using the tower top gantry. The clamps at both ends of the first steel strand are installed and tensioned to the design value. The installation of other steel strands is carried out using a circulating traction system.

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