Construction method of widened four-panel catwalk structure through towers for high and low four-main-cable suspension bridge

Abstract

This invention provides a variable-width, four-span catwalk structure and construction method for a high-low four-main-cable suspension bridge, including a high-low four-span catwalk structure, a variable-width catwalk structure, a catwalk-through-tower structure, and a wind-resistant and impact-resistant system. The alignment of the four-span catwalk structure perfectly matches the alignment of the high-low four main cables. The inner and outer catwalks are independently set up, forming multiple working surfaces, which can well adapt to the changes in the main cable alignment during the construction of the superstructure of the high-low four-main-cable suspension bridge. A variable cross-section catwalk structure is adopted, transforming the catwalk cross-section near the tower into a narrow catwalk cross-section, solving the problem of small lateral spacing and spatial interference between the inner and outer catwalks. The overall cross-section of the catwalk is symmetrical, resulting in high overall safety. The catwalk-through-tower structure does not occupy the working space at the top of the tower, solving the problem of insufficient working space at the top of the tower in high-low four-main-cable suspension bridges. A wind-resistant and impact-resistant system using vibration damping cables and anti-collision devices is adopted, which improves the overall wind and impact resistance of the high-low four-span catwalk structure and solves the problem of wind-induced collisions.

Description

Technical Field

[0001] This invention relates to the technical field of construction of the superstructure of suspension bridges, specifically to the widened four-panel catwalk structure and construction method of a high-low four-main-cable suspension bridge. Background Technology

[0002] With the continuous increase in the span and load of suspension bridges, the specifications of the main cables are also constantly improving. Especially for 2000m-class double-deck suspension bridges, the main cable wire strength will reach 2160MPa, and the diameter will exceed 1.5m. The excessively large scale of the main cables, saddles, clamps, and anchorages leads to high manufacturing requirements, significant construction difficulties, and low economic efficiency. In recent years, a novel high-low four-main-cable suspension bridge structure has been developed in China. On each side, two small-diameter main cables arranged at different heights replace one ultra-large-diameter main cable. Reducing the main cable diameter and using conventional erection equipment and processes effectively reduces the difficulty of main cable construction, shortens the construction period, and reduces costs. At the same time, the spatial arrangement of the four main cables increases the overall stiffness and damping significantly, improving the structure's wind and seismic resistance.

[0003] For innovative systems of high-low four-main-cable suspension bridges, a four-span catwalk structure needs to be designed to match the alignment of the four main cables to meet the requirements of superstructure construction. Research shows that traditional catwalk structures, both domestically and internationally, are designed with two spans, connected by a transverse passage between the upstream and downstream catwalks; for parallel four-main-cable suspension bridges, a wide, double-span catwalk is used. Currently, there are no actual high-low four-span catwalk projects domestically or internationally, nor are there any research reports on the design and construction of high-low four-main-cable catwalk structures. Therefore, for high-low four-main-cable suspension bridges, an innovative high-low four-main-cable catwalk structure and construction method needs to be proposed to solve the design and construction challenges of high-low four-main-cable catwalks and promote the development of new structural systems for high-low four-main-cable suspension bridges.

[0004] There are challenges in the design and construction of the four-span catwalk structure: 1) The four-span catwalk layout occupies a large space, and the lateral spacing between the inner and outer catwalks is small with vertical height differences. The traditional catwalk width layout will cause spatial interference problems, requiring innovative design of the overall catwalk layout and cross-sectional form; 2) For large-span four-span catwalk structures, the number of catwalk load-bearing ropes is large. If the traditional tower-looping scheme is adopted, the displacement angle of the load-bearing ropes is large, and a large amount of tower top space is occupied, affecting the operation in the tower top area; 3) The lateral spacing between the inner and outer catwalks is small, which can easily lead to collisions in strong winds; 4) The four-span catwalk is an innovative structure and is relatively complex compared with traditional catwalks. The construction feasibility of the new catwalk structure needs to be considered throughout the entire process to avoid mutual interference between the construction of the inner and outer catwalks. Summary of the Invention

[0005] The main objective of this invention is to provide a variable-width, four-panel catwalk structure for a high-low four-main-cable suspension bridge and a construction method therefor, thereby solving the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention includes a four-span catwalk structure with varying heights, a catwalk widening structure, a catwalk through-tower structure, and a wind-resistant and impact-resistant system.

[0007] The high-low four-span catwalk structure is a continuous catwalk structure designed to match the high-low four main cable alignment, including a double-span inner main cable catwalk, a double-span outer main cable catwalk, and a transverse passage.

[0008] The catwalk widening structure includes a normal-width catwalk area, a narrow catwalk area, and a displacement steel frame. Different catwalk cross sections are set according to the different height differences between the inner and outer catwalks. The displacement steel frame is used to transform the cross section of the normal-width catwalk area into the cross section of the narrow catwalk area.

[0009] The catwalk structure includes pre-embedded pipes, cable-switching devices, and triangular brackets. The catwalk load-bearing cables pass through the main tower via the pre-embedded pipes, and the vertical alignment of the catwalk load-bearing cables is adjusted by the cable-switching devices and triangular brackets to make them pass through the tower parallel to each other.

[0010] The wind impact resistance system includes a vibration damping device and an anti-collision device. The vibration damping device is used to connect the lateral channels of the inner and outer main cable catwalks to improve wind and impact resistance, while the anti-collision device is used to prevent collisions between the inner and outer catwalks.

[0011] Preferably, the mid-span elevation of the inner main cable is higher than that of the outer main cable, the catwalk alignment of the inner main cable is higher than that of the outer main cable at the mid-span, and they are at the same elevation at the top of the tower.

[0012] Preferably, the upstream and downstream double-width inner main cable catwalks are set parallel to the inner main cable, and the double-width inner main cable catwalks are connected by a transverse channel.

[0013] The upstream and downstream dual-width outer main cable catwalks are set parallel to the outer main cables, and the dual-width outer main cable catwalks are connected by a transverse channel.

[0014] The inner main cable catwalk and the outer main cable catwalk are relatively independent.

[0015] Preferably, a normal-width catwalk area is set up in the area where the height difference between the inner and outer main cable catwalks is large;

[0016] Narrow catwalk zones are set up in areas where the elevation difference between the inner and outer main cable catwalks is small.

[0017] The wide catwalk area and the narrow catwalk area are connected by a displacement steel frame to achieve a lateral transition and widening.

[0018] Preferably, the pre-embedded pipe is located at the top of the tower, and the triangular bracket is pre-embedded to both sides of the top of the tower by the tower crane and the tower top winch, so that the outer catwalk load-bearing cable passes through the pre-embedded pipe in parallel.

[0019] Preferably, the vibration damping device is located between the first transverse channel of the inner main cable catwalk and the outer main cable catwalk in the near tower area. The vibration damping device includes a limiting cable and a tensioning device. The limiting cable is diagonally tensioned between the transverse channels of the inner and outer main cable catwalks, and the limiting cable is arranged in a "⋈" shape.

[0020] Upon receiving a strong wind warning signal, the tensioning device tightens the limiting cable to form an adaptive tension-compression system.

[0021] Preferably, the anti-collision device is a rubber buffer sleeve, which is installed on the inner catwalk load-bearing cable and the outer catwalk gantry column respectively.

[0022] The method is:

[0023] S1. Preparation for catwalk construction: Equipment and materials for winches and catwalk cables are brought to the site, and four single-line reciprocating traction systems are set up for the four catwalks.

[0024] S2. The catwalk load-bearing cable is erected using the bracket method. The traction system pulls the catwalk load-bearing cable to the top of the tower. The tower top winch and guide rope are connected to the end of the catwalk load-bearing cable. The traction system puller is released, and the tower top winch is started to pull the end of the cable through the pre-buried pipe at the top of the tower.

[0025] S3. After completing the tower penetration operation, the traction cable pulls the puller to the middle span side of the tower top, then reconnects the puller to the catwalk load-bearing cable, releases the guide rope, and the puller continues to pull the catwalk load-bearing cable to the top of the tower on the other side. Repeat the tower penetration operation until the cable is in place. Then, perform hot casting joint operation in the designated area in front of the cat anchor, and then install it into the anchoring system. Complete the sag adjustment of the catwalk load-bearing cable, and the installation of the catwalk load-bearing cable is completed.

[0026] S4. Catwalk gantry cable erection: Similar to the above-mentioned catwalk load-bearing cable erection, but it does not need to pass through the pre-buried pipe at the top of the tower. It is directly pulled over the tower, the bracket is removed, and the bracket load-bearing cable is converted into a catwalk handrail cable.

[0027] S5. Installation of displacement steel frame: A catwalk gantry cable system is used to erect a zenith trolley system to assist in the installation of the displacement steel frame;

[0028] S6. Surface layer and transverse passage installation: With the assistance of the tower crane, first install the surface layer of the narrow catwalk area from the top of the tower to the displacement frame area. Then, use the displacement frame as an assembly platform to assemble the surface layer of the normal width catwalk area on the middle span side. Then, use the tower top winch and traction system to slide down for installation.

[0029] S7. Catwalk gantry installation: The catwalk gantry is assembled as a whole on the ground. The tower crane lifts it onto the gantry's load-bearing cable and uses the winch at the top of the tower to pull it back, sliding the gantry one by one down to the designed position for installation.

[0030] S8. Installation of wind and impact resistant system: One end of the limiting cable is connected to the bottom of the inner catwalk lateral passage before the lateral passage is installed. After the catwalk gantry is installed, the other end is connected to the top surface of the outer catwalk lateral passage through the traction system.

[0031] S9. The anti-collision device components are transported via a zenith trolley during the sliding installation of the catwalk surface and catwalk gantry, and are pre-installed at designated positions on the inner and outer catwalk load-bearing cables and the catwalk gantry, respectively.

[0032] Preferably, in step S7, to avoid interference, the inner and outer catwalk gantry frames are installed alternately by sliding down.

[0033] Preferably, in step S6, the transverse cat walkway and the cat walkway surface layer are lowered simultaneously, serving as a counterweight.

[0034] This invention provides a variable-width, four-span catwalk structure and construction method for a four-main-cable suspension bridge with varying heights and tower widths, with the following advantages:

[0035] 1. The alignment of the four-panel catwalk structure of the present invention is perfectly matched with the alignment of the four main cables of different heights. The inner and outer catwalks are set independently to form multiple working surfaces, which can well adapt to the changes in the alignment of the main cables during the construction of the superstructure of the four main cable suspension bridge of different heights.

[0036] 2. This invention employs a variable cross-section catwalk structure, transforming the catwalk cross-section near the tower into a narrow cross-section, thus resolving the issues of small lateral spacing and spatial interference between the inner and outer catwalks. The catwalk cross-section is symmetrical overall, resulting in high overall safety.

[0037] 3. This invention adopts a catwalk through-tower structure, which does not occupy the tower top working space and solves the problem of insufficient working space at the top of the tower of a high and low four main cable suspension bridge.

[0038] 4. This invention adopts a wind and impact resistant system with vibration damping cable and anti-collision device, which improves the overall wind and impact resistance of the four-lane catwalk structure and solves the problem of wind-induced collision. Attached Figure Description

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0040] Figure 1 This is a view of the four-panel catwalk structure of the present invention;

[0041] Figure 2 This is a schematic diagram of the narrow catwalk area arranged with variable width cross section according to the present invention;

[0042] Figure 3 This is a schematic diagram of the variable-width cross-section arrangement of the catwalk in this invention, showing the normal-width catwalk area.

[0043] Figure 4 This is a front view of the catwalk through-tower structure of the present invention;

[0044] Figure 5 This is a side view of the catwalk through-tower structure of the present invention;

[0045] Figure 6 This is a schematic diagram of the limiting cable connection of the wind-resistant and impact-resistant system of the present invention;

[0046] Figure 7 This is a schematic diagram of the installation of the rubber buffer sleeve of the wind-resistant and impact-resistant system of the present invention;

[0047] Figure 8 This invention relates to the catwalk load-bearing cable tower penetration operation - before tower penetration;

[0048] Figure 9 This invention relates to the catwalk load-bearing cable tower penetration operation - after tower penetration;

[0049] In the diagram: 1—Inner main cable catwalk; 2—Outer main cable catwalk; 3—Narrow catwalk area; 4—Normal width catwalk area; 5—Transverse passage; 6—Outer main cable; 7—Inner main cable; 8—Outer catwalk load-bearing cable; 9—Inner catwalk load-bearing cable; 10—Outer catwalk gantry; 11—Inner catwalk gantry; 12—Outer catwalk gantry cable; 13—Inner catwalk gantry cable; 14—Buried pipe; 15—Triangular bracket; 16—Cable switching device; 17—Cable adjusting mechanism; 18—Cable saddle; 19—Limiting cable; 20—Rubber buffer sleeve; 21—Traction cable; 22—Puller; 23—Bracket load-bearing cable; 24—Bracket; 25—Tower top winch; 26—Guide rope. Detailed Implementation

[0050] Example 1

[0051] like Figure 1 As shown, the four-span catwalk structure of the high-low four-main-cable suspension bridge features a wider, through-tower design. The mid-span elevation of the inner main cable (span 7) is higher than that of the outer main cable (span 6). Therefore, the alignment of the inner main cable catwalk 1 at the mid-span is higher than that of the outer main cable catwalk 2, but they are at the same elevation at the top of the tower. The two inner main cable catwalks 1 and the two outer main cable catwalks 2 are connected by a transverse passage 5, maintaining relative independence between them.

[0052] Different catwalk sections are set according to the different height differences between the inner and outer main cable catwalks: In areas with a large height difference between the inner and outer main cable catwalks, there is basically no interference between the catwalks, so the catwalks are arranged as the normal width catwalk zone 4; In areas with a small height difference between the inner and outer main cable catwalks, the inner and outer main cable catwalks interfere with each other, so the narrow catwalk zone 3 is set; The normal width catwalk zone 4 and the narrow catwalk zone 3 are widened laterally through a displacement steel frame.

[0053] like Figure 2As shown, the typical width of a catwalk is 4m. When the center-to-center distance between the inner main cable 7 and the outer main cable 6 is less than 4m, interference will occur between the inner and outer main cable catwalks due to the need for symmetrical arrangement and space requirements for main cable traction, cable tensioning, and wire winding. Therefore, a narrow catwalk section 3 is adopted, reducing the lateral dimension of the catwalk to within 3m to ensure that the inner catwalk load-bearing cable 9 does not collide with the outer catwalk gantry 10. The width of the catwalk affects its wind resistance performance, but the length of the narrow catwalk section 3 accounts for a small proportion of the total length of the catwalk and has virtually no impact on wind resistance performance.

[0054] like Figure 3 As shown, at this time, the bottom elevation of the inner catwalk load-bearing cable 9 is higher than the top of the outer catwalk gantry 10, and there is no interference problem between the inner and outer catwalks. This part adopts the normal width catwalk area 4 section arrangement, with a width of 4m and symmetrical arrangement.

[0055] like Figure 4 , 5 As shown, since the total number of catwalk load-bearing cables in a four-lane catwalk is double that of a two-lane catwalk, and it is necessary to bypass four cable saddles 18, the traditional method of bypassing the tower and passing the saddles would occupy a large amount of working space at the top of the tower, and the bending angle would be too large, requiring a large amount of lateral displacement measures. The catwalk load-bearing cables include the outer catwalk load-bearing cable 8 and the inner catwalk load-bearing cable 9.

[0056] Therefore, a 100mm diameter steel pipe with a 10mm wall thickness is pre-embedded at the top of the tower to ensure the smooth passage of the load-bearing cable while providing sufficient supporting rigidity. Additionally, steel fibers are added to the concrete mix in the opening area to prevent cracking of the tower concrete. The load-bearing cable passes directly through the inside of the steel pipe, eliminating the need for lateral displacement and minimizing overall structural costs. Triangular brackets 15 are pre-embedded to both sides of the tower top via a tower crane and a tower-top winch 25, ensuring that the load-bearing cable 8 of the outer catwalk passes parallel to the pre-embedded pipe 14, preventing friction between the cable and the steel pipe. An adjustment device 17 is also installed to adjust the catwalk's load-bearing alignment.

[0057] like Figure 6 and Figure 7 As shown, a wind-resistant and collision-resistant system is installed to prevent collisions caused by the small lateral spacing between the inner and outer catwalks in narrow catwalk areas during strong winds. The wind-resistant system includes a vibration damping device and a collision-resistant device. The vibration damping device is installed between the first lateral passage 5 of the inner and outer main catwalks near the tower. The limiting cable 19 is pre-tensioned diagonally between the lateral passages 5 of the inner and outer main catwalks. When a strong wind warning signal is received, the tensioning device tightens the limiting cable 19, forming a "⋈"-shaped adaptive tension-compression system between the inner and outer main catwalks, consisting of the limiting cable 19 and the lateral passage 5, thus improving the overall wind and impact resistance of the four-catwalk structure.

[0058] The rubber buffer sleeve 20 is a buffer device installed between the inner catwalk load-bearing cable 9 and the outer catwalk gantry 10. It is designed with reference to the anti-ship collision rubber guard structure of the dock. The rubber buffer sleeve 20 is wrapped around the collision risk area between the outer catwalk gantry 10 column and the inner catwalk load-bearing cable 9 to reduce the collision response of the inner and outer catwalks.

[0059] Example 2

[0060] like Figures 1-9 As shown, in conjunction with Example 1, the construction method of the widened four-span catwalk structure through the towers of the high and low four-main-cable suspension bridge is further explained. The method is as follows:

[0061] S1. Preparation for catwalk construction: Equipment and materials for winches and catwalk cables are brought to the site, and four single-line reciprocating traction systems are set up for the four catwalks.

[0062] S2. The outer catwalk load-bearing cable is erected using the bracket method. The traction system pulls the catwalk load-bearing cable to the top of the tower. The tower top winch 25 and guide rope 26 are connected to the catwalk load-bearing cable head. The traction system puller 22 is released, and the tower top winch 25 is started to pull the rope head through the tower top pre-buried pipe 14.

[0063] S3. After completing the tower penetration operation, the traction cable 21 pulls the puller 22 to the middle span side of the tower top, then reconnects the puller 22 to the catwalk load-bearing cable, releases the guide rope 26, and the puller 22 continues to pull the catwalk load-bearing cable to the top of the tower on the other side. Repeat the tower penetration operation until the cable is pulled into place. Then, perform hot casting joint operation in the designated area in front of the cat anchor, and then install it into the anchoring system to complete the sag adjustment of the catwalk load-bearing cable. The installation of the catwalk load-bearing cable is now complete.

[0064] S4. Catwalk gate cable erection: Similar to the above-mentioned catwalk load-bearing cable erection, but it does not need to pass through the pre-buried pipe 14 at the top of the tower. It is directly pulled over the tower, the bracket 24 is removed, and the bracket load-bearing cable 23 is converted into the catwalk handrail cable.

[0065] S5. Installation of displacement steel frame: A catwalk gantry cable system is used to erect a zenith trolley system to assist in the installation of the displacement steel frame;

[0066] S6. Surface layer and transverse passage installation: With the assistance of the tower crane, first install the 3rd surface layer of the narrow catwalk area from the tower top to the displacement frame area. Then, use the displacement frame as an assembly platform to assemble the 4th surface layer of the normal width catwalk area on the middle span side. Then, use the tower top winch 25 and traction system to slide down for installation.

[0067] S7. Catwalk gantry installation: The catwalk gantry is assembled as a whole on the ground. The tower crane lifts it onto the gantry's load-bearing cable and uses the tower top winch 25 reverse pull to slide the gantry down one by one to the design position for installation.

[0068] S8. Installation of wind and impact resistant system: One end of the limiting cable 19 is connected to the bottom of the inner cat walkway 5 before the installation of the transverse passage 5. After the cat walkway gantry is installed, the other end is connected to the top surface of the outer cat walkway 5 through the traction system.

[0069] S9. The anti-collision device components are transported via a zenith trolley during the sliding installation of the catwalk surface and catwalk gantry, and are pre-installed at designated positions on the inner and outer catwalk load-bearing cables and the catwalk gantry, respectively.

[0070] Preferably, in step S7, to avoid interference, the inner and outer catwalk gantry frames are installed alternately by sliding down.

[0071] Preferably, in step S6, the transverse cat walkway and the cat walkway surface layer are lowered simultaneously, serving as a counterweight.

[0072] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. The widened, four-panel catwalk structure of a high-low four-main-cable suspension bridge is characterized by: This includes a four-span catwalk structure with varying heights, a catwalk widening structure, a catwalk penetrating tower structure, and a wind-resistant and impact-resistant system. The high-low four-span catwalk structure is a continuous catwalk structure designed to match the high-low four main cable alignment, including a double-span inner main cable catwalk (1), a double-span outer main cable catwalk (2), and a transverse passage (5). The catwalk widening structure includes a normal width catwalk area (4), a narrow catwalk area (3) and a displacement steel frame. Different catwalk sections are set according to the different height differences between the inner and outer catwalks. The displacement steel frame is used to transform the cross section of the normal width catwalk area (4) into the cross section of the narrow catwalk area (3). The catwalk structure includes a pre-embedded pipe (14), a cable-switching device (16), and a triangular bracket (15). The catwalk load-bearing cable passes through the main tower through the pre-embedded pipe (14), and the vertical alignment of the catwalk load-bearing cable is adjusted by the cable-switching device (16) and the triangular bracket (15) so that it passes through the tower in parallel. The wind impact resistance system includes a vibration damping device and an anti-collision device. The vibration damping device is used to connect the transverse channels of the inner and outer main cable catwalks (5) to improve wind and impact resistance. The anti-collision device is used to prevent collisions between the inner and outer catwalks. The vibration damping device is located between the first transverse channel (5) of the double-span inner main cable catwalk (1) and the double-span outer main cable catwalk (2) in the near-tower area. The vibration damping device includes a limiting cable (19) and a tensioning device. The limiting cable (19) is diagonally tensioned between the transverse channels (5) of the inner and outer main cable catwalks. The limiting cable (19) is in the shape of a " "-shaped layout; Upon receiving a strong wind warning signal, the tensioning device tightens the limiting cable (19) to form an adaptive tension-compression system; The anti-collision device is a rubber buffer sleeve (20), which is installed on the inner catwalk load-bearing cable (9) and the outer catwalk gantry (10) respectively.

2. The variable-width, four-span catwalk structure of the high and low four-main-cable suspension bridge according to claim 1, characterized in that: The mid-span elevation of the inner main cable (7) is higher than that of the outer main cable (6). The inner main cable catwalk (1) is higher than the outer main cable catwalk (2) at the mid-span, but at the same elevation at the top of the tower.

3. The variable-width, four-span catwalk structure of the high and low four-main-cable suspension bridge according to claim 1, characterized in that: The upstream and downstream double-width inner main cable catwalks (1) are set in parallel with the inner main cable (7), and the double-width inner main cable catwalks (1) are connected by a transverse channel (5); The upstream and downstream double-width outer main cable catwalks (2) are set in parallel with the outer main cable (6), and the double-width outer main cable catwalks (2) are connected by a transverse channel (5); The inner main cable catwalk (1) and the outer main cable catwalk (2) are relatively independent.

4. The variable-width, four-panel catwalk structure of the high and low four-main-cable suspension bridge according to claim 1, characterized in that: A normal-width catwalk area (4) is set up in the area where the elevation difference between the inner main cable catwalk (1) and the outer main cable catwalk (2) is large. Narrow catwalk areas (3) are set up in areas where the elevation difference between the inner main cable catwalk (1) and the outer main cable catwalk (2) is small. The wide catwalk area (4) and the narrow catwalk area (3) are connected by a displacement steel frame to achieve a lateral transition and widening.

5. The variable-width, four-span catwalk structure of the high and low four-main-cable suspension bridge according to claim 1, characterized in that: The pre-embedded pipe (14) is located at the top of the tower, and the triangular bracket (15) is pre-embedded to both sides of the top of the tower by the tower crane and the tower top winch (25) so that the outer catwalk load-bearing cable (8) passes through the pre-embedded pipe (14) in parallel.

6. The construction method of the variable-width four-span catwalk structure through the towers of the high and low four-main-cable suspension bridge according to any one of claims 1 to 5, wherein the method is as follows: S1. Preparation for catwalk construction: Equipment and materials for winches and catwalk cables are brought to the site, and four single-line reciprocating traction systems are set up for the four catwalks. S2. The catwalk load-bearing cable is erected using the bracket method. The traction system pulls the catwalk load-bearing cable to the top of the tower. The tower top winch (25) and guide rope (26) are connected to the head of the catwalk load-bearing cable. The traction system puller (22) is released, and the tower top winch (25) is started to pull the head of the cable through the pre-buried pipe (14) at the top of the tower. S3. After completing the tower penetration operation, the traction cable (21) pulls the puller (22) to the middle span side of the tower top, and then reconnects the puller (22) with the catwalk load-bearing cable. The guide rope (26) is released, and the puller (22) continues to pull the catwalk load-bearing cable to the top of the tower on the other side. The tower penetration operation is repeated until the cable is pulled into place. Then, the hot-cast joint operation is carried out in the designated area in front of the cat anchor, and then it is installed into the anchoring system. The sag adjustment of the catwalk load-bearing cable is completed, and the catwalk load-bearing cable installation is completed. S4. Catwalk gantry cable erection: Similar to the above-mentioned catwalk load-bearing cable erection, but it does not need to pass through the pre-buried pipe (14) at the top of the tower. It is directly pulled over the tower, the bracket (24) is removed, and the bracket load-bearing cable (23) is converted into the catwalk handrail cable; the catwalk gantry cable includes the outer catwalk gantry cable (12) and the inner catwalk gantry cable (13). S5. Installation of displacement steel frame: A catwalk gantry cable system is used to erect a zenith trolley system to assist in the installation of the displacement steel frame; S6. Surface layer and transverse passage installation: With the assistance of the tower crane, first install the surface layer of the narrow catwalk area (3) from the top of the tower to the displacement frame area. Then, use the displacement frame as an assembly platform to assemble the surface layer of the normal width catwalk area (4) on the middle span side. Then, use the tower top winch (25) and traction system to slide down for installation. S7. Catwalk gantry installation: The catwalk gantry is assembled on the ground as a whole. The tower crane lifts it onto the gantry's load-bearing cable and uses the tower top winch (25) to pull it back and slide the gantry down to the design position one by one for installation. The catwalk gantry includes the outer catwalk gantry (10) and the inner catwalk gantry (11). S8. Installation of wind-resistant and impact-resistant system: Before the installation of the transverse channel (5), one end of the limiting cable (19) is connected to the bottom of the inner cat walkway transverse channel (5). After the cat walkway gantry is installed, the other end is connected to the top surface of the outer cat walkway transverse channel (5) through the traction system. S9. The anti-collision device components are transported via a zenith trolley during the sliding installation of the catwalk surface and catwalk gantry, and are pre-installed at designated positions on the inner and outer catwalk load-bearing cables and the catwalk gantry, respectively.

7. The construction method of the variable-width four-span catwalk structure through the towers of the high and low four-main-cable suspension bridge according to claim 6, characterized in that: In step S7, to avoid interference, the inner and outer catwalk gantry frames are installed alternately by sliding down.

8. The construction method of the variable-width four-span catwalk structure through the towers of the high and low four-main-cable suspension bridge according to claim 6, characterized in that: In step S6, the transverse catwalk and the catwalk surface layer are lowered simultaneously, serving as counterweights.

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