Cable crane and method suitable for hoisting four-main-cable suspension bridge girder with different sags

Abstract

The invention discloses a cable crane suitable for hoisting four-main-cable suspension bridge girders with different sags, which is characterized in that four supporting legs are arranged on the cable crane and are respectively supported on four main cables in a one-to-one correspondence manner to form a plurality of supporting points, so that the inner main cable and the outer main cable are cooperatively deformed and stressed in the girder hoisting process. The modularized outer side supporting legs are additionally arranged and supported on the outer cable, and meanwhile the outer side supporting legs can be adjusted in a telescopic mode through the oil cylinders, so that cooperative deformation and stress of the inner cable and the outer cable are guaranteed; stress and displacement monitoring elements are additionally arranged at the positions of the supporting legs, the states of the supporting legs of the cable crane are monitored in the whole steel beam hoisting process, and the hoisting safety and stability are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge construction. More specifically, the present invention relates to a multi-support cable-supported crane and method for hoisting the main girder of a four-main-cable suspension bridge with different sag ratios. Background Art

[0002] Hoisting the main girder is a key step in the construction process of a suspension bridge. Traditional suspension bridges have only two main cables, and the cable-supported crane is usually supported on the double main cables to carry out the main girder hoisting operation by utilizing the strength of the main cables. In recent years, with the continuous increase of the bridge span and load, the diameter of the main cables of suspension bridges has been continuously increasing and is approaching the limit. Industry experts have proposed a new type of suspension bridge structure with four main cables of different sag ratios, in which four main cables arranged in a high-low manner jointly bear the load of the super-long-span suspension bridge. The structural form can be seen in the patent - A Suspension Bridge with Four Main Cables of Different Vertical-to-Span Ratios (Patent Application No.: CN202110769322.2). For this new structure, due to space interference problems, when the traditional cable-supported crane is applied to hoist the main girder of a four-main-cable suspension bridge with different sag ratios, it can only be supported on the higher inner cable for hoisting operations and cannot be supported on the outer cable. During the beam hoisting process, after the inner cable bears all the loads, it deforms downward by several meters, while the outer cable hardly deforms downward because it is not stressed. This results in a large deformation difference between the inner and outer cables. This deformation difference makes it impossible to install the outer cable suspenders of the mid-span beam section. Even if some forced measures are taken to complete the installation of the suspenders, during the beam hoisting process, problems such as uneven stress on the inner and outer cables and inner and outer suspenders will occur due to the deformation difference, thus affecting the safety and stability of the hoisting. The design and structure of the traditional cable-supported crane cannot well adapt to the special requirements of the high-low four-main-cable suspension bridge. When applied to hoist the main girder of a four-main-cable suspension bridge with different sag ratios, the inner and outer cables and inner and outer suspenders cannot work together in terms of force, affecting the safety and stability of the hoisting and restricting its application in the construction of such bridges.

[0003] In view of the above problems, there is an urgent need to develop a new equipment and method for hoisting the main girder of a four-main-cable suspension bridge with different sag ratios. Summary of the Invention

[0004] An object of the present invention is to provide a multi-support cable-supported crane and method for hoisting the main girder of a four-main-cable suspension bridge with different sag ratios, which adds modular outer support legs that are supported on the outer cable, and the outer support legs can be adjusted by the telescopic cylinder to ensure the coordinated deformation and force of the inner and outer cables; stress and displacement monitoring elements are added at the positions of each support leg to monitor the state of the support legs of the cable-supported crane throughout the whole process of steel beam hoisting, improving the safety and stability of the hoisting. It solves the problems of excessive deformation difference between the inner and outer cables, inability to connect the suspenders, and uneven force existing in the hoisting of a four-main-cable suspension bridge with different sag ratios by using a conventional cable-supported crane.

[0005] To solve the above technical problems, the present invention provides a cable-supported crane applicable to the hoisting of the main girder of a four-main-cable suspension bridge with different sag degrees. The cable-supported crane is provided with four support legs, which respectively support on the four main cables one by one, forming multiple support points, so that the inner main cable and the outer main cable deform and bear force synergistically during the beam-hoisting process.

[0006] Preferably, the cable-supported crane includes a steel truss, and installation beams are formed by extending both ends of the steel truss outwards. Inner support legs and outer support legs are sequentially and spacedly installed on the installation beams from the inside outwards. The two inner support legs respectively support on two inner main cables, and the two outer support legs respectively support on two outer main cables. The bottom surface of the steel truss hoists the main girder through a sling, and the inner cable suspenders and the outer cable suspenders are respectively connected to corresponding positions of the main girder.

[0007] Preferably, the outer support leg includes an outer support fixing member supported on the outer main cable and a pair of hydraulic cylinder jacking devices arranged oppositely. Two ends of the hydraulic cylinder jacking device are respectively hinged to the outer support fixing member and the installation beam. The hydraulic cylinder jacking device is used to adjust the height of the outer support leg to adapt to the different height differences between the inner main cable and the outer main cable at different positions, so that each support leg is stably supported on the corresponding main cable.

[0008] Preferably, the hydraulic cylinder jacking device includes a first connecting plate, a second connecting plate slidably connected to the first connecting plate, and a propulsion cylinder. Jacking limit chutes are arranged on opposite sides of the first connecting plate. The second connecting plate is slidably matched and slides in the jacking limit chutes. The top of the first connecting plate and the bottom of the second connecting plate are respectively hinged to the outer support fixing member and the installation beam. End limit bolts are fixedly arranged on the outer sides of the first connecting plate and the second connecting plate on the same side. The cylinder body and the telescopic rod of the propulsion cylinder are respectively connected to the two end limit bolts.

[0009] Preferably, the outer support leg is of modular design and is integrally installed on the installation beam.

[0010] Preferably, stress sensors, inclination sensors and displacement sensors are arranged on all four support legs, which are respectively used to monitor the stress, inclination and displacement states of the support legs of the cable-supported crane.

[0011] Preferably, it further includes a control system, which controls the jacking cylinders corresponding to the hydraulic cylinder jacking devices to act, and the control system also receives the monitoring data of the stress sensors, inclination sensors and displacement sensors.

[0012] The present invention also provides a hoisting construction method for a cable-supported crane applicable to the hoisting of the main girder of a four-main-cable suspension bridge with different sag degrees, including the following steps: Step 1: After the cable-supported crane is assembled and installed on site, it moves to the area of the beam to be lifted, and completes the temporary fixation measurement of the standing position before hoisting; Step 2: Measure the specific sag of the inner main cable and the outer main cable, calculate the real-time height difference between the inner main cable and the outer main cable, and input the data into the control system. The control system calculates the initial height required for the outer support leg according to the input data; Step 3: Adjust the length of the outer support leg according to the calculated initial height so that the outer support leg can support on the outer main cable; Step 4: The hoisting system of the cable-supported crane is started, and the main beam begins to be lifted; Step 5: After the hoisting is completed, move to the next hoisting position and repeat the above steps.

[0013] Preferably, in Step 2, install a Beidou Global Navigation Satellite System (BDS) receiver at the main cable position where the cable-supported crane stands, measure the three-dimensional coordinates of the centerlines of the inner and outer main cables in real time, obtain the specific sag of the inner and outer main cables, and calculate the real-time height difference △1 between the inner and outer main cables; before the adjustment of the outer support leg, there is an initial height difference △2 between the hoops of the inner support leg and the outer support leg. Then the initial adjustment height of the outer support leg is △1 - △2.

[0014] Preferably, in Step 4, the control system is set in the hoisting system. After the main beam is lifted to a set distance from the ground, the stress sensors are used to monitor the stress conditions of the inner support leg and the outer support leg in real time; the inclination sensors are used to monitor the stability of the cable-supported crane in real time; the displacement sensors are used to monitor the displacement of the support legs in real time; the Beidou Global Navigation Satellite System (BDS) receiver is used to monitor the elevation changes of the inner and outer cables in real time; after the control system obtains the corresponding data, it judges whether the forces on the inner support leg and the outer support leg are uneven, that is, the force value ratio is greater than 1.3, and whether the elevation change, inclination change and displacement change are within the set threshold range. If there are abnormalities, the main beam will be lowered, and according to the actual measurement situation, the construction model of the main beam of the four-main-cable suspension bridge with different sags will be corrected, and the initial height correction value of the outer support leg will be adjusted to ensure the safety of the main beam hoisting construction.

[0015] The present invention has at least the following beneficial effects: 1. Through the design of four support legs, the multi-support cable-supported crane of the present invention can adapt to the hoisting working conditions of the main beam of the four-main-cable suspension bridge with different sags, ensure the coordinated deformation and force of the inner and outer cables during the beam hoisting process, and improve the safety and stability of the main beam hoisting. At the same time, the outer support leg is of modular design. For the hoisting of the main beam of general suspension bridges, the outer support leg can be removed and applied, and the equipment has strong versatility.

[0016] 2. The height of the outer support legs of the present invention can be adjusted by the telescopic hydraulic cylinder to adapt to different hoisting conditions with different height differences between the inner and outer cables. Meanwhile, during the hoisting of the lifting beam, the stress and force conditions of each support leg are monitored to evaluate the hoisting state of the cable-supported crane in real time.

[0017] Other advantages, objectives, and features of the present invention will be partially reflected by the following description and partially understood by those skilled in the art through the research and practice of the present invention. Brief Description of the Drawings

[0018] Figure 1 It is a schematic structural diagram of the multi-support cable-supported crane of the present invention.

[0019] Figure 2 It is a schematic diagram showing that the outer cable boom cannot be connected when the main beam of the conventional cable-supported crane corresponding to the present invention is hoisted.

[0020] Figure 3 It is a schematic structural diagram of the outer support legs of the present invention.

[0021] Figure 4 It is a schematic structural diagram of the hydraulic cylinder lifting device of the present invention; Figure 5 It is a schematic diagram of the layout of the monitoring components of the present invention.

[0022] Description of the Reference Numerals in the Drawings: 1 - Outer support leg; 2 - Outer main cable; 3 - Inner main cable; 4 - Outer support fixing member; 5 - Hydraulic cylinder lifting device; 6 - Inner cable boom; 7 - Inner support leg; 8 - Outer cable boom; 9 - Propulsion cylinder; 10 - End limit bolt; 11 - First connecting plate; 12 - Second connecting plate; 13 - Lifting limit sliding groove; 14 - Steel truss; 15 - Hoisting system; 16 - Lifting tool; 17 - Control system; 18 - Vibration mode stress sensor; 19 - Photoelectric inclination sensor; 20 - Linear displacement sensor; 21 - Laser displacement sensor. Detailed Description of the Embodiment

[0023] In order to better understand the objectives, structure, and functions of the present invention, the following further detailed description of the present invention is made with reference to the drawings, so that those skilled in the art can implement it according to the description in the specification.

[0024] It should be noted that, unless otherwise specified, the experimental methods described in the following implementation plans are all conventional methods, and the reagents and materials, unless otherwise specified, can all be obtained from commercial channels; in the description of the present invention, the terms "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation to the present invention.

[0025] As Figure 1 shown, the present invention provides a cable-supported crane applicable to the hoisting of the main girder of a four-main-cable suspension bridge with different sag degrees. The cable-supported crane is provided with four support legs, which respectively support on the four main cables one by one, forming multiple support points, so that the inner main cable and the outer main cable deform and bear force synergistically during the beam-hoisting process, improving the safety and stability of the main girder hoisting.

[0026] In another technical solution, the cable-supported crane includes a steel truss, and installation beams are formed by extending both ends of the steel truss outward. Inner support legs and outer support legs are sequentially installed at intervals from the inside to the outside on the installation beams. The two inner support legs respectively support on the two inner main cables, and the two outer support legs respectively support on the two outer main cables. The bottom surface of the steel truss hoists the main girder through a sling, and the inner cable suspenders 6 and the outer cable suspenders 8 are respectively connected to the corresponding positions of the main girder.

[0027] The structure of the multi-support cable-supported crane of the present invention is similar to that of the traditional cable-supported crane. On the basis of the traditional cable-supported crane, modular outer support legs are added and supported on the outer main cable, including inner support legs 1 and outer support legs 7, a steel truss 14, a hoisting system 15, a sling 16, and a control system 17. A total of 4 support legs are provided, which are respectively designed to support on the outer main cable and the inner main cable to ensure that the inner and outer cables deform and bear force synergistically during the beam-hoisting process. As Figure 1 shown, the multi-support cable-supported crane mainly adds the outer support leg 1 shown in the box in the figure to ensure that the main girder can be supported on the outer main cable 2 of the four-main-cable suspension bridge with different sag degrees of high and low. The traditional cable-supported crane can only support on the inner main cable 3. As Figure 2 shown, when carrying out the hoisting of the main girder, the inner main cable 3 will deform greatly downward, and the outer main cable 2 has no deformation, resulting in a large deformation difference between the inner and outer cables compared with the completed bridge. Therefore, the outer cable suspenders 8 of the outer main cable cannot be connected to the main girder. However, the multi-support cable-supported crane shown in Figure 1 of the present application ensures that the inner and outer cables deform downward together during the hoisting process of the main girder through the inner and outer support legs. Therefore, there is no deformation difference between the inner main cable and the outer main cable, and the inner and outer side suspenders can be smoothly connected without additional measures.

[0028] In another technical solution, Figure 3 As shown, the outer supporting leg includes an outer supporting fixture 4 supported on the outer main cable and a pair of hydraulic cylinder lifting devices 5 arranged opposite to each other, the two ends of the hydraulic cylinder lifting device are respectively hinged to the outer supporting fixture and the mounting beam, and the hydraulic cylinder lifting device is used to adjust the height of the outer supporting leg to adapt to the different height differences between the inner main cable and the outer main cable at different positions, so that each supporting leg is firmly supported on the corresponding main cable.

[0029] The height difference between the inner and outer cables is constantly changing in different cross-sections. Therefore, the outer support leg 1 is equipped with a hydraulic cylinder lifting device 5 based on the inner support leg 7. The height of the outer support leg can be adjusted by the cylinder to ensure that the inner and outer cables are subjected to coordinated force. For four-main-cable suspension bridges with different vertical angles, the height difference between the inner and outer cables at different longitudinal bridge positions is different. In order to adapt to the deformation of the height difference, a hydraulic cylinder lifting device is set on the outer leg of the cable-mounted crane. Before the main beam is hoisted, the outer support leg can adjust the length according to the height difference between the inner and outer cables to ensure that each support leg can be firmly supported on the corresponding main cable, ensuring that the inner and outer cables are subjected to coordinated force during the hoisting process. A pair of hydraulic cylinder lifting devices are relatively arranged to achieve stable and synchronous adjustment.

[0030] In another technical solution, Figure 4 As shown, the hydraulic cylinder lifting device includes a first connecting plate 11, a second connecting plate 12 slidably connected to the first connecting plate 11, and a thrust cylinder 9. Lifting limit slide grooves 13 are arranged on opposite sides of the first connecting plate 11. The second connecting plate 12 slides in the lifting limit slide grooves 13. The top of the first connecting plate 11 and the bottom of the second connecting plate 12 are respectively hinged on the external support fixing member 4 and the mounting beam. The first connecting plate and the second connecting plate are both fixedly provided with end limit bolts 10 on the outer sides of the same side. The cylinder body and telescopic rod of the thrust cylinder 9 are respectively connected to the two end limit bolts.

[0031] The main structure of the hydraulic cylinder lifting device 5 includes a propulsion cylinder 9, a limit bolt 10 at the end of the lifting device, a first connecting plate 11, a second connecting plate 12, a lifting limit slide 13 and some other bolt hole limit parts; by propulsion cylinder lifting, the relative distance between the first connecting plate and the second connecting plate can be adjusted, the height of the outer supporting leg can be changed, and the height difference between the inner and outer cables can be adapted. Adjust the main beam into place before lifting, and lock the bolt hole position. A plurality of pairs of positioning bolt holes are also provided on the first connecting plate 11 and the second connecting plate 12, respectively. After the position is adjusted into place, the positioning bolt holes at the corresponding positions of the first connecting plate 11 and the second connecting plate 12 are locked by bolts; during the position adjustment process, the bolts on the first connecting plate 11 and the second connecting plate 12 are removed.

[0032] In another technical solution, the outer support legs are modularly designed and are integrally installed on the installation beam. Alternatively, the outer support legs and the corresponding installation beam can be integrally modularly designed. During use, they are connected and assembled with the corresponding installation beam on the inner support legs. With the modular design of the outer support legs, for the hoisting of the main girder of a general suspension bridge, the outer support legs can be removed for application, and the equipment has strong versatility.

[0033] In another technical solution, as Figure 5 shown, stress sensors, inclination sensors, and displacement sensors are provided on all four support legs, which are respectively used to monitor the stress, inclination, and displacement states of the support legs of the cable-suspended crane.

[0034] Stress and displacement monitoring components are added at the positions of the support legs of the multi-support cable-suspended crane to monitor the state of the support legs of the cable-suspended crane throughout the process of steel girder hoisting, improving the safety and stability of hoisting. Compared with the traditional cable-suspended crane, the number of support points changes from 2 to 4, and the hoisting load of the main girder is borne jointly by the inner and outer cables instead of the inner cable alone, increasing the safety and stability of the cable-suspended crane during the hoisting of the main girder. However, the force system changes from statically determinate to statically indeterminate, and the stress becomes complex. Therefore, stress and displacement monitoring components are added at the positions of the support legs of the multi-support cable-suspended crane to monitor the stress conditions of each support leg in real time during the process of hoisting the beam and evaluate the hoisting safety. The stress sensor component is a vibrating type stress sensor 18, which has good long-term monitoring stability and strong anti-interference ability, is suitable for harsh environments, and is installed at the middle web position of different support legs. Combined with the jacking force data of the hydraulic cylinder of the outer support leg, the stress condition of the support leg is evaluated; the inclination monitoring component is an optoelectronic inclination sensor 19, which has high precision and strong anti-interference ability and is installed at the crossbeam position of different support legs to evaluate the inclination state; the displacement monitoring components are a linear variable differential transformer (LVDT) 20 and a laser displacement sensor 21. The linear variable differential transformer (LVDT) is installed at the top support position of the hydraulic cylinder of the outer support leg, and the laser displacement sensor is installed at the bottom surface position of the large crossbeam of different support legs to evaluate the displacement state of the support leg.

[0035] In another technical solution, it further includes a control system, which controls the corresponding jacking cylinders of the hydraulic cylinder jacking device to act, and the control system also receives the monitoring data of the stress sensors, inclination sensors, and displacement sensors.

[0036] The present invention also discloses a hoisting construction method for a cable-suspended crane suitable for hoisting the main girder of a four-main-cable suspension bridge with different sag degrees. The specific working process is as follows: Step 1: Conduct measurement work before hoisting. The cable-supported crane is modularly designed. After being assembled and installed on-site, it moves to the area of the beam to be hoisted and completes the temporary fixation of the standing position before hoisting. The surveyors use to determine the specific sag of the inner and outer cables, calculate the real-time height difference between the inner and outer cables, and input the data into the control system. The control system calculates the required initial height of the outer support leg based on the input data. Install a Beidou Global Navigation Satellite System (BDS) receiver at the main cable position where the cable-supported crane stands, measure the three-dimensional coordinates of the centerlines of the inner and outer main cables in real time, obtain the specific sag of the inner and outer main cables, and calculate the real-time height difference △1 between the inner and outer main cables; before adjusting the outer support leg, there is an initial height difference △2 between the hoops of the inner support leg and the outer support leg, so the initial adjustment height of the outer support leg is △1 - △2.

[0037] Step 2: Adjust the support legs. Through the instructions of the control system, the four hydraulic cylinder jacking devices start to operate, release the positioning bolts between the connecting plates, and adjust the corresponding support legs to the appropriate height respectively to ensure that each support leg can closely fit on the cable. Since the jacking distance of the hydraulic cylinder is limited, every time a certain distance is jacked up, it is necessary to cooperate to temporarily fix the positioning bolts of the connecting plate again, release the limit bolts of the jacking device, retract the hydraulic cylinder, and re-fix the limit bolts of the jacking device at the next hole position. Since the height difference change between the inner and outer cables between adjacent hoisted beam segments is generally less than 1 m, there will be no situation of multiple disassembly and adjustment in one hoisting stage. After the adjustment is completed, re-fix the positioning bolts of the connecting plate. Generally, the height difference between the inner and outer cables of the mid-span beam segment is about the height of the main beam. For a steel truss beam, it is about 10 m. If the height difference between the inner and outer cables is too large and it is impossible to further increase the hydraulic cylinder jacking device, at this time, extend the connecting plate to the longest. Before hoisting, the outer support leg cannot support on the outer main cable. For this special situation, as long as the outer cable can be pressed down during hoisting to ensure that the outer cable suspender can be connected to the main beam.

[0038] Step 3: Hoisting start. The multi-support cable-supported crane hoisting system starts, and the main girder begins to be lifted. The displacement, inclination angle and stress sensors located on the outer support legs continuously monitor the deformation of the inner and outer cables and the operating state of the hoisting mechanism. The hoisting system makes real-time adjustments according to the monitoring data to ensure the smoothness and safety of the hoisting process. The control system is set inside the hoisting system. When carrying out the hoisting of the main girder, the main girder is lifted about 0.2 m above the ground. The stress sensors are used to monitor the forces on the inner and outer support legs in real time; the inclination sensors are used to monitor the stability of the cable-supported crane in real time; the displacement sensors are used to monitor the displacement of the support legs in real time; the BDS receivers of the Beidou global satellite navigation system are used to monitor the elevation changes of the inner and outer cables in real time. After obtaining the corresponding data through the control system, if it is judged that there is uneven force on the inner and outer support legs (the force value ratio is greater than 1.3), or there are abnormalities in the elevation change and inclination change, exceeding the designed threshold, the main girder needs to be lowered. According to the actual measurement, the finite element model of the main girder construction of the four-main-cable suspension bridge with different sag is corrected, and the initial height correction value of the outer support leg is adjusted to ensure the safety of the main girder hoisting construction.

[0039] Step 4: Hoisting completed, move to the next hoisting position. When the main girder is lifted to the predetermined position, it is first lifted 50 cm more. The inner cable suspenders and outer cable suspenders are connected to the main girder, and then it is lowered. The load of the main girder is transferred from the cable-supported crane to the suspenders. The control system maintains the stable state of the support legs, the hoisting system stops working, and the hoisting task is completed. The connection between the lifting appliance and the main girder lifting lug is released. After the routine safety inspection of the cable-supported crane, it is ready to move to the next beam section hoisting position to carry out the hoisting work of the next beam section.

[0040] It can be understood that the present invention is described through some embodiments. Those skilled in the art know that without departing from the spirit and scope of the present invention, various changes or equivalent replacements can be made to these features and embodiments. Although the embodiments of the present invention are disclosed as above, it is not limited to only the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily achieved. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details and the examples shown and described here.

Claims

1. A cable-suspended crane applicable to the hoisting of the main girder of a four-main-cable suspension bridge with different sag degrees, characterized in that, It includes that four support legs are arranged on the cable-supported crane, which respectively support on the four main cables one by one, forming multiple support points, so that the inner main cable and the outer main cable are deformed and stressed cooperatively during the beam hoisting process.

2. The cable-supported crane applicable to the hoisting of the main girder of a four-main-cable suspension bridge with different sag degrees as described in claim 1, characterized in that The cable-supported crane includes a steel truss, and installation beams are formed by extending both ends of the steel truss outwards. Inner support legs and outer support legs are sequentially installed at intervals from the inside to the outside on the installation beams. The two inner support legs respectively support on the two inner main cables, and the two outer support legs respectively support on the two outer main cables. The bottom surface of the steel truss hoists the main beam through a sling, and the inner cable hoist rod and the outer cable hoist rod are respectively connected to the corresponding positions of the main beam.

3. The cable-supported crane applicable to the hoisting of the main girder of a four-main-cable suspension bridge with different sag degrees as claimed in claim 2, wherein, The outer support leg includes an outer support fixing member supported on the outer main cable and a pair of hydraulic cylinder lifting devices arranged oppositely. The two ends of the hydraulic cylinder lifting device are respectively hinged to the outer support fixing member and the installation beam. The hydraulic cylinder lifting device is used to adjust the height of the outer support leg to adapt to the different height differences between the inner main cable and the outer main cable at different positions, so that each support leg is firmly supported on the corresponding main cable.

4. The cable-supported crane applicable to the hoisting of the main girder of a four-main-cable suspension bridge with different sag degrees as claimed in claim 3, wherein, The hydraulic cylinder lifting device includes a first connecting plate, a second connecting plate slidably connected to the first connecting plate, and a propulsion cylinder. Jacking limit chutes are arranged on the opposite sides of the first connecting plate. The second connecting plate is slidably matched and slides in the jacking limit chutes. The top of the first connecting plate and the bottom of the second connecting plate are respectively hinged to the outer support fixing member and the installation beam. End limit bolts are fixedly arranged on the outer sides of the first connecting plate and the second connecting plate on the same side. The cylinder body and the telescopic rod of the propulsion cylinder are respectively connected to the two end limit bolts.

5. The cable-supported crane applicable to the hoisting of the main girder of a four-main-cable suspension bridge with different sag degrees as claimed in claim 2, characterized in that, The outer support leg is of modular design and is integrally installed on the installation beam.

6. The cable-supported crane applicable to the hoisting of the main girder of a four-main-cable suspension bridge with different sag degrees as claimed in claim 4, wherein Stress sensors, inclination sensors and displacement sensors are arranged on all four support legs, which are respectively used to monitor the stress, inclination and displacement states of the support legs of the cable-supported crane.

7. The cable-supported crane applicable to the hoisting of the main girder of a four-main-cable suspension bridge with different sag degrees as claimed in claim 6, wherein, It also includes a control system, which controls the action of the jacking cylinders corresponding to the hydraulic cylinder lifting devices. The control system also receives the monitoring data of the stress sensors, inclination sensors and displacement sensors.

8. Hoisting construction method of a cable-supported crane applicable to the hoisting of the main girder of a four-main-cable suspension bridge with different sag degrees, characterized in that, It includes the following steps: Step 1: After the cable-supported crane is assembled and installed on site, it walks to the area where the beam to be hoisted is located, and completes the temporary fixing measurement of the position before hoisting. Step 2: Measure the specific sag of the inner main cable and the outer main cable, calculate the real-time height difference between the inner main cable and the outer main cable, and input the data into the control system. The control system calculates the required initial height of the outer support leg according to the input data. Step 3: Adjust the length of the outer support leg according to the calculated initial height, so that the outer support leg can support on the outer main cable. Step 4: The hoisting system of the cable-supported crane is started, and the main beam begins to be lifted. Step 5: After the hoisting is completed, it walks to the next hoisting position and repeats the above steps.

9. The hoisting construction method of the cable-supported crane applicable to the hoisting of the main girder of a four-main-cable suspension bridge with different sag degrees as claimed in claim 8, characterized in that, In the second step, a Beidou Global Navigation Satellite System (BDS) receiver is installed at the main cable position where the cable-borne crane is stationed to measure the three-dimensional coordinates of the centerlines of the inner and outer main cables in real time, obtain the specific sag of the inner and outer main cables, and calculate the real-time height difference Δ1 between the inner and outer main cables. Before the outer support leg is adjusted, there is an initial height difference Δ2 between the clamps of the inner support leg and the outer support leg. Therefore, the initial adjustment height of the outer support leg is Δ1 - Δ2.

10. The hoisting construction method of the cable-supported crane applicable to the hoisting of the main girder of a four-main-cable suspension bridge with different sag degrees as claimed in claim 9, characterized in that, In the fourth step, the control system is set in the lifting system. After the main beam is lifted to a set distance from the ground, the stress sensors are used to monitor the forces on the inner and outer support legs in real time; the inclination sensors are used to monitor the stability of the cable-borne crane in real time; the displacement sensors are used to monitor the displacements of the support legs in real time; the BDS receiver is used to monitor the elevation changes of the inner and outer cables in real time. After the control system obtains the corresponding data, it judges whether the forces on the inner and outer support legs are uneven, that is, the force ratio is greater than 1.3, and whether the elevation changes, inclination changes, and displacement changes are within the set threshold ranges. If there are any abnormalities, the main beam is lowered, and according to the actual measurement, the construction model of the main beam of the four-main-cable suspension bridge with different sags is corrected, and the initial height correction value of the outer support leg is adjusted to ensure the safety of the main beam hoisting construction.

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