Bridge steel box girder hoisting device and hoisting construction method thereof

Abstract

The invention relates to the technical field of hoisting equipment, in particular to a bridge steel box girder hoisting device and a hoisting construction method.The bridge steel box girder hoisting device comprises a hoisting ring and a plurality of slings, the tops of the slings are connected with the hoisting ring, side clamping plates are arranged at the other ends of the slings, and fixing units are arranged on the side clamping plates; according to the bridge steel box girder hoisting device and the hoisting construction method thereof, the combined extension unit is arranged on the side clamping plate close to the side where a steel box girder is installed, the moving units are arranged on the other side clamping plates, and a detection piece is further arranged on any side clamping plate. When the steel box girder is hoisted to the installation position, the combined extension unit can extend and be clamped with the installed steel box girder to assist in butt-joint installation of the hoisted steel box girder and the installed steel box girder, the situation that multiple times of manual measurement and supporting are needed in traditional hoisting is avoided, and the installation efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of hoisting equipment technology, specifically to a bridge steel box girder hoisting device and its hoisting construction method. Background Technology

[0002] Steel box girders, also known as steel plate box girders, are a common structural form for long-span bridges. They are generally used on bridges with large spans and are called steel box girders because their shape resembles a box. Steel box girders are generally composed of a top plate, bottom plate, web plate, transverse diaphragms, longitudinal diaphragms, and stiffening ribs, all connected by full welding.

[0003] When installing two adjacent steel box girders, the construction workers fix one of the steel box girders, then use a crane to lift the other steel box girder into the air. Then, they manually align the lifted steel box girder with the fixed steel box girder, and finally weld the connection between the two steel box girders. However, during the construction process, aligning the lifted steel box girder with the fixed steel box girder requires manual operation and the cooperation of surveyors. The alignment may not be accurate enough, which is quite troublesome and also poses a safety hazard.

[0004] To address the aforementioned issues, Chinese patent CN116986463B proposes a steel box girder hoisting device for hoisting and positioning two adjacent steel box girders during installation. The device includes two symmetrically arranged hoisting modules connected by a connecting component. Each hoisting module comprises a support component, an adjustment component, and a clamping component. The support component includes a support base and a hoisting frame, with the hoisting frame fixedly mounted on the upper end of the support base. The connecting component is positioned between the two hoisting frames. An adjustment component is located at the lower part of one end of the support base. Two clamping components are provided: one rotatably mounted at the lower end of the adjustment component, and the other fixedly mounted at the lower part of the other end of the support base. The clamping components clamp the end of the steel box girder. This prior art device, with its adjustment component and control component, enables precise alignment between the steel box girder to be installed and the already fixed steel box girder.

[0005] While the aforementioned patent enables docking during the hoisting and installation of steel box girders, it contains multiple precision components, such as adjustment components, clamping components, and control components, as well as some lead screws and worm gear drives. The large number of components and the complex linkage relationships increase the manufacturing difficulty and maintenance costs of the equipment. Furthermore, since steel box girders are generally heavy, weighing up to hundreds of tons, these linkage designs may loosen due to mechanical fatigue or material creep under some heavy load conditions, affecting the overall structural rigidity and the safety of hoisting.

[0006] Therefore, we propose a bridge steel box girder hoisting device and its hoisting construction method. Summary of the Invention

[0007] To address the aforementioned technical problems, this application provides a bridge steel box girder hoisting device, comprising lifting rings and slings. Multiple slings are provided, with their tops connected to the lifting rings. Each sling has a side clamp plate at its other end. A fixing unit is provided on each side clamp plate, and a combined extension unit is provided on the side clamp plate closest to the already installed steel box girder. Movable units are provided on the remaining side clamp plates, and a detection component is also provided on any of the side clamp plates.

[0008] In some embodiments, the side clamp is U-shaped and its inner opening fits the outer side of the steel box girder. The fixing unit includes a plurality of fixing cylinders arranged on the upper and lower sides of the side clamp. Each fixing cylinder has a fastening plate at its output end. The side clamp has clearance holes for the fastening plates to pass through.

[0009] In some embodiments, a flange is provided on the outside of the fixed cylinder, and a mounting bracket is installed on the side clamp by bolts. The fixed cylinder is bolted to the mounting bracket via the flange.

[0010] In some embodiments, the combined extension unit consists of a first side plate, a middle plate, and a second side plate. The first side plate, the middle plate, and the second side plate are combined to form a U-shaped structure consistent with the shape of the side clamping plate. An extension cylinder is provided inside the first side plate, and the output end of the first extension cylinder is fixedly connected to the middle plate. An extension cylinder is provided at the bottom of the middle plate, and the output end of the second extension cylinder is fixedly connected to the second side plate. A docking cylinder is fixedly provided on the side clamping plate, and the output end of the docking cylinder is fixedly connected to the first side plate.

[0011] In some embodiments, a roller is rotatably mounted on the side clamp, the bottom end of the sling is wound around the roller, a rotating shaft is provided in the middle of the roller, a drive motor is fixedly mounted on the side clamp, a reducer is connected to the output end of the drive motor, and the output end of the reducer is connected to the rotating shaft on the roller.

[0012] In some embodiments, the detection element is a horizontal sensor.

[0013] In some embodiments, a through groove is provided on the back side of the side clamping plate, and the moving unit includes two drive shafts rotatably disposed on both sides of the through groove. A traveling wheel is provided on the outside of the drive shaft, and a pulley is also provided on the outside of the drive shaft. A belt is provided on the outside of the pulley. The two drive shafts are synchronously driven by the belt. A worm gear is also provided on the outside of one of the drive shafts. A reduction motor is fixedly disposed on the back side of the side clamping plate, and a worm gear that meshes with the worm gear is provided at the output end of the reduction motor.

[0014] In some embodiments, a plurality of ball bearings are movably disposed on the inner bottom surface of the side clamp.

[0015] In some embodiments, a cushioning pad is provided on the outer side of the side clamp.

[0016] This invention provides a method for hoisting a bridge steel box girder hoisting device, comprising the following steps: S1: The side clamping plate is clamped on the outside of the steel box girder. The side clamping plate is moved by the moving motor to drive the traveling wheels so that the hoisting reaches a balanced state. The steel box girder is clamped by the fixed oil cylinder. S2: Conduct a trial lift of the steel box girder, with a lifting height of less than 200mm, and observe the mechanical performance of the crane; S3: Slowly lift the steel box girder and transport it to the installation position, using guy ropes for traction to prevent the steel box girder from rotating horizontally; S4: After being hoisted to the installation position, the hoisted steel box girder is connected to the already installed steel box girder using a modular extension unit, thereby completing the installation.

[0017] The present invention has at least the following beneficial effects: 1. A combined extension unit is installed on the side clamp plate near the installed steel box girder. When the steel box girder is hoisted to the installation position, the combined extension unit can extend and engage with the installed steel box girder, assisting the hoisted steel box girder to dock with the installed steel box girder for installation. This avoids the need for multiple manual measurements and support in traditional hoisting, thus improving installation efficiency. 2. The fixing unit adopts a fixing cylinder and a fastening plate. The side clamp is U-shaped and the inner opening fits the outer side of the steel box girder. The fixing cylinder is set on the upper and lower sides of the side clamp, and the output end is equipped with a fastening plate. The fastening plate abuts against the surface of the steel box girder through the clearance hole, forming a wrap-around clamp on the upper and lower sides of the steel box girder, ensuring that the side clamp forms a stable clamp on the steel box girder. The fixing cylinder is bolted to the mounting bracket through a flange, which is convenient for disassembly, replacement and maintenance. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the steel box girder hoisting state of the present invention; Figure 2 This is a schematic diagram of the overall structure of the present invention; Figure 3 This is a schematic diagram of one of the side clamping plate structures of the present invention; Figure 4 This is a schematic diagram of the structure of the combined extension unit of the present invention; Figure 5 For the present invention Figure 3 Schematic diagram of a partial explosion structure; Figure 6 For the present invention Figure 5 Schematic diagram of a partial structure; Figure 7 This is a schematic diagram of the moving unit structure of the present invention; Figure 8 This is a schematic diagram of the side clamp and combined extension unit structure of the present invention; Figure 9 This is a schematic cross-sectional view of the side plate and the middle plate of the present invention; Figure 10 This is a schematic diagram of the initial and unfolded states of the combined extension unit of the present invention.

[0019] In the diagram: 1-Lifting ring; 2-Lifting sling; 3-Side clamp; 4-Fixing unit; 41-Fixing cylinder; 42-Fastening plate; 43-Mounting bracket; 5-Combined extension unit; 51-Side plate one; 52-Intermediate plate; 53-Side plate two; 54-Extension cylinder one; 55-Extension cylinder two; 56-Connecting cylinder; 6-Moving unit; 61-Drive shaft; 62-Walking wheel; 63-Worm gear; 64-Gear motor; 65-Worm; 7-Roller; 8-Drive motor; 9-Gear reducer; 10-Through groove; 11-Ball bearing; 12-Buffer pad. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1: Please refer to Figures 1-2 This invention provides a technical solution: a bridge steel box girder hoisting device for hoisting steel box girders to the installation position, comprising lifting rings 1 and slings 2, wherein the slings 2 are configured with four slings, the top of each sling 2 being connected to the lifting ring 1, the lifting ring 1 being connected to the hook of the crane, and the other end of each sling 2 being provided with a side clamping plate 3, the side clamping plate 3 being able to engage with the outer side of the steel box girder, the side clamping plate 3 being provided with a fixing unit 4, the fixing unit 4 enabling the side clamping plate 3 to stably clamp both sides of the steel box girder, and the side clamping plate 3 near the already installed steel box girder being provided with a combined extension unit 5, which is used when the steel box girder is hoisted to the installation position. When positioned, the combined extension unit 5 can extend to one end of the already installed steel box girder and engage with it, thereby assisting in the docking and installation of the hoisted steel box girder with the already installed steel box girder. The remaining side clamps 3 are equipped with moving units 6, which allow the side clamps 3 to move to the side of the steel box girder, thereby facilitating the adjustment of the position of the slings 2 to achieve a balanced state during hoisting. Each side clamp 3 is also equipped with a detection element, which can detect the posture of the side clamp 3, thereby detecting the posture of the hoisted steel box girder and facilitating adjustments during hoisting.

[0022] During hoisting, the crane connects to the hoisting equipment via lifting rings 1, and then lifts the steel box girder using slings 2. Before the steel box girder is lifted, side clamps 3 are placed on both sides of the steel box girder. In this embodiment, four side clamps 3 are provided, with two on each side of the steel box girder. The four slings 2 can stably lift the steel box girder. After the side clamps 3 are engaged with the outside of the steel box girder, the fixing unit 4 can clamp the sides of the steel box girder from top to bottom to ensure a stable connection between the side clamps 3 and the steel box girder. Since the steel box girder itself is large, the side clamps 3 are also large. In order to ensure the stability and safety of hoisting, the side clamps 3 are made of high-strength alloy steel. To ensure balance during hoisting, the position of the side clamps 3 needs to be adjusted according to the actual center of gravity of the steel box girder. This ensures that the steel box girder remains balanced when hoisted and that the four slings 2 are evenly stressed. During adjustment, one side clamp 3 of the steel box girder remains stationary, while the other side clamp 3, equipped with a moving unit 6, can move along the side of the steel box girder. This allows for adjustment of the hoisting position. Subsequently, the crane lifts the steel box girder and transports it to the installation position. The combined extension unit 5 extends out to connect with the already installed steel box girder, thus assisting in the connection of the hoisted steel box girder. This avoids the need for multiple manual measurements in traditional hoisting and allows for docking without manual support, increasing installation efficiency.

[0023] Example 2: Please refer to Figures 3-5 The present invention provides a technical solution: a bridge steel box girder hoisting device, which further includes a fixing cylinder 41 and a fastening plate 42. The side clamping plate 3 is U-shaped and its inner opening fits the outer side of the steel box girder. The fixing unit 4 includes a plurality of fixing cylinders 41 arranged on the upper and lower sides of the side clamping plate 3. The output end of the fixing cylinder 41 is provided with a fastening plate 42. The side clamping plate 3 is provided with a clearance hole for the fastening plate 42 to pass through.

[0024] The side clamping plate 3 is forged as a whole from high-strength alloy steel. The upper and lower flanges can be connected by an arc-shaped transition section to avoid stress concentration. The inner surface is sprayed with a wear-resistant ceramic coating to reduce friction damage with the steel box girder surface. After the side clamping plate 3 is engaged with the steel box girder, the fixing cylinder 41 extends to drive the fastening plate 42 to abut against the surface of the steel box girder. The fixing cylinder 41 is set on the two flanges of the side clamping plate 3, thereby forming a wrap-around clamping on the upper and lower sides of the steel box girder. Under the clamping action of the fastening plates 42 on the upper and lower sides, the side clamping plate 3 forms a stable clamping on the steel box girder. The diameter of the clearance hole is slightly larger than that of the fastening plate 42 so that it can pass through the clearance hole and ensure that the fastening plate 42 will not get stuck when it extends.

[0025] A flange is provided on the outside of the fixed cylinder 41, and a mounting bracket 43 is installed on the side clamping plate 3 by bolts. The fixed cylinder 41 is bolted to the mounting bracket 43 through the flange. The two side wing plates of the mounting bracket 43 are also installed on the side clamping plate 3 by multiple sets of high-strength bolts, which facilitates the disassembly and replacement of the cylinder without the need for overall replacement, and also facilitates maintenance at any time.

[0026] Example 3: Please refer to Figure 9 This invention provides a technical solution: a bridge steel box girder hoisting device, further comprising a side plate 51, a middle plate 52, and a second side plate 53. A combined extension unit 5 is composed of the side plate 51, the middle plate 52, and the second side plate 53. The side plate 51, the middle plate 52, and the second side plate 53 combine to form a U-shaped structure consistent with the shape of the side clamping plate 3, thus allowing it to engage with the outer side of the steel box girder. An extension cylinder 54 is installed inside the side plate 51, and the output end of the extension cylinder 54 is fixedly connected to the middle plate 52. When the extension cylinder 54 extends, it can drive the middle plate 52 away from the side plate 51. An extension cylinder 55 is installed at the bottom of the middle plate 52, and the output end of the extension cylinder 55 is fixedly connected to the second side plate 53. When the second extension cylinder extends, it can move the second side plate 53 away from the middle plate 52. A docking cylinder 56 is fixedly installed on the side clamping plate 3. The output end of the docking cylinder 56 is fixedly connected to the first side plate 51. When the docking cylinder 56 extends, it can move the first side plate 51 away from the side clamping plate 3. The first side plate 51 then moves the middle plate 52 and the second side plate 53 away from the side clamping plate 3 in the same way. When both the first extension cylinder 54 and the second extension cylinder 55 extend, the U-shaped structure formed by the combination of the first side plate 51, the middle plate 52, and the second side plate 53 is in an expanded state. That is, the upper and lower openings of this U-shaped structure become larger, and its length increases. Therefore, even when there is a large gap between the hoisted steel box girder and the already installed steel box girder, it can still fit onto the outside of the already installed steel box girder. For details, please refer to [link to relevant documentation]. Figure 10 Then, when extension cylinder 1 54 and extension cylinder 2 55 retract, the U-shaped structure is gradually retracted until side plate 1 51, middle plate 52 and side plate 2 53 are all restored to their initial state. At this time, all three are closely attached to the outside of the steel box girder, and the connection is completed.

[0027] Example 4: Please refer to Figures 4-6 The present invention provides a technical solution: a bridge steel box girder hoisting device, which further includes a roller 7 and a drive motor 8. The roller 7 is rotatably mounted on the side clamping plate 3. The bottom end of the sling 2 is wound around the roller 7. The sling 2 can be wound and unwound on the roller 7 by the bidirectional rotation of the roller 7. A rotating shaft is provided in the middle of the roller 7. The drive motor 8 is fixedly mounted on the side clamping plate 3. The output end of the drive motor 8 is connected to a reducer 9. The drive motor 8 connected to the reducer 9 can adapt to the large load scenario of steel box girder hoisting and ensure stable use. The output end of the reducer 9 is connected to the rotating shaft on the roller 7 for transmission.

[0028] The detection component is a horizontal sensor, but it is not limited to that; it can also be other sensors that can detect the hoisting status of the steel box girder, such as an angle sensor.

[0029] When the steel box girder is hoisted to the required installation position, if the hoisted steel box girder is placed completely parallel to the already installed steel box girder, it means that it has been placed in the bottom installation position. However, in this case, the position of the steel box girder cannot be adjusted. The on-site workers need to observe and use walkie-talkies to notify the crane operator to lift and lower the steel box girder multiple times to complete the docking installation. In this invention, a drive motor 8 and a roller 7 are set on the side clamp plate 3. The drive motor 8 drives the roller 7 to raise and lower the sling 2. Thus, when the steel box girder is hoisted to the required installation position, the roller 7 on the side clamp plate 3 at the docking end can lower the sling 2 a little distance. At this time, the hoisted steel box girder is in a certain tilted state, and its tilting direction is towards the installation side. Then, the combined extension unit 5 wraps around the already installed steel box girder, and at the same time, the sling 2 on the other side is lowered to complete the docking installation of the two steel box girders.

[0030] Example 5: Please refer to Figures 6-7 The present invention provides a technical solution: a bridge steel box girder hoisting device, which further includes a through groove 10 and a traveling wheel 62 disposed in the through groove 10. The through groove 10 is opened on the back side of the side clamping plate 3. The moving unit 6 includes two drive shafts 61 rotatably disposed on both sides of the through groove 10. The traveling wheel 62 is disposed on the outside of the drive shaft 61. The pulley is also disposed on the outside of the drive shaft 61. The belt is disposed on the outside of the pulley. The two drive shafts 61 are synchronously driven by the belt. The worm gear 63 is also disposed on the outside of one of the drive shafts 61. A reduction motor 64 is fixedly disposed on the back side of the side clamping plate 3. The output end of the reduction motor 64 is provided with a worm 65 that meshes with the worm gear 63.

[0031] The geared motor 64 drives the worm gear 63 and worm 65 to mesh, thereby driving the traveling wheel 62 to rotate. When the side clamping plate 3 is engaged with the steel box girder, the fixing cylinder 41 has not yet clamped the steel box girder. At this time, the traveling wheel 62 can drive the side clamping plate 3 to move along the outside of the steel box girder, thereby adjusting the hoisting position.

[0032] Multiple balls 11 are movably disposed on the bottom inner surface of the side clamp 3. When the side clamp 3 moves, due to the possible slight irregularities on the surface of the steel box girder, traditional sliding friction can easily cause the side clamp 3 to jam. The balls 11 reduce frictional resistance through point contact. The balls 11 are installed in the hemispherical groove at the bottom inner side of the side clamp 3, and the diameter of the groove is slightly larger than the diameter of the balls 11, ensuring that the balls 11 roll freely but will not fall off.

[0033] A buffer pad 12 is provided on the outer side of the side clamp plate 3. After the hoisting is completed and the side clamp plate 3 is separated from the steel box girder, the side clamp plates 3 will move towards the middle and move directly under the lifting ring 1. Therefore, by providing a buffer pad 12 on the outer side of the side clamp plate 3, the side clamp plates 3 can be buffered when they collide with each other, which can reduce the noise when the side clamp plates 3 collide with each other and also prevent the coating on the surface of the side clamp plate 3 from being damaged.

[0034] This invention provides a method for hoisting a bridge steel box girder hoisting device, comprising the following steps: S1: The side clamping plate 3 is clamped on the outside of the steel box girder. The side clamping plate 3 is moved by the moving motor driving the traveling wheel 62 to achieve a balanced state of hoisting. The steel box girder is clamped by the fastening plate 42 through the fixed oil cylinder 41. S2: Conduct a trial lift of the steel box girder, with a lifting height of less than 200mm, and observe the mechanical performance of the crane; S3: Slowly lift the steel box girder and transport it to the installation position, using guy ropes for traction to prevent the steel box girder from rotating horizontally; S4: After being hoisted to the installation position, the hoisted steel box girder is connected to the already installed steel box girder through the combined extension unit 5, thereby completing the installation.

[0035] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A bridge steel box girder hoisting device, comprising a lifting ring (1) and slings (2), wherein multiple slings (2) are provided and their tops are all connected to the lifting ring (1), characterized in that: The other end of each sling (2) is provided with a side clamp (3), a fixing unit (4) is provided on the side clamp (3), a combined extension unit (5) is provided on the side clamp (3) near the installed steel box girder, and a moving unit (6) is provided on the other side clamps (3). A detection piece is also provided on any one of the side clamps (3).

2. The bridge steel box girder hoisting device according to claim 1, characterized in that: The side clamp (3) is U-shaped and its inner opening fits the outer side of the steel box girder. The fixing unit (4) includes multiple fixing cylinders (41) set on the upper and lower sides of the side clamp (3). Each fixing cylinder (41) has a fastening plate (42) at its output end. The side clamp (3) has a clearance hole for the fastening plate (42) to pass through.

3. The bridge steel box girder hoisting device according to claim 2, characterized in that: A flange is provided on the outside of the fixed cylinder (41), and a mounting bracket (43) is installed on the side clamp (3) by bolts. The fixed cylinder (41) is bolted to the mounting bracket (43) through the flange.

4. The bridge steel box girder hoisting device according to claim 1, characterized in that: The combined extension unit (5) consists of a side plate one (51), a middle plate (52) and a side plate two (53). The side plate one (51), the middle plate (52) and the side plate two (53) are combined to form a U-shaped structure consistent with the shape of the side clamping plate (3). An extension cylinder one (54) is provided in the side plate one (51). The output end of the extension cylinder one (54) is fixedly connected to the middle plate (52). An extension cylinder two (55) is provided at the bottom of the middle plate (52). The output end of the extension cylinder two (55) is fixedly connected to the side plate two (53). A docking cylinder (56) is fixedly provided on the side clamping plate (3). The output end of the docking cylinder (56) is fixedly connected to the side plate one (51).

5. The bridge steel box girder hoisting device according to claim 1, characterized in that: A roller (7) is rotatably mounted on the side clamp (3). The bottom end of the sling (2) is wound around the roller (7). A rotating shaft is provided in the middle of the roller (7). A drive motor (8) is fixedly mounted on the side clamp (3). A reducer (9) is connected to the output end of the drive motor (8). The output end of the reducer (9) is connected to the rotating shaft on the roller (7) for transmission.

6. The bridge steel box girder hoisting device according to claim 1, characterized in that: The detection component is a horizontal sensor.

7. The bridge steel box girder hoisting device according to claim 1, characterized in that: The back side of the side clamp (3) is provided with a through groove (10). The moving unit (6) includes two drive shafts (61) rotatably arranged on both sides of the through groove (10). A walking wheel (62) is provided on the outside of the drive shaft (61). A pulley is also provided on the outside of the drive shaft (61). A belt is provided on the outside of the pulley. The two drive shafts (61) are synchronously driven by the belt. A worm gear (63) is also provided on the outside of one of the drive shafts (61). A reduction motor (64) is fixedly provided on the back side of the side clamp (3). A worm (65) that meshes with the worm gear (63) is provided at the output end of the reduction motor (64).

8. The bridge steel box girder hoisting device according to claim 7, characterized in that: Multiple ball bearings (11) are movably disposed on the bottom inner surface of the side clamp (3).

9. The bridge steel box girder hoisting device according to claim 1, characterized in that: A buffer pad (12) is provided on the outside of the side clamp (3).

10. A hoisting construction method for a bridge steel box girder hoisting device according to any one of claims 1-9, characterized in that, Includes the following steps: S1: The side clamp (3) is clamped on the outside of the steel box girder. The side clamp (3) is moved by the moving motor to drive the walking wheel (62) so that the hoisting reaches a balanced state. The steel box girder is clamped by the fastening plate (42) through the fixed oil cylinder (41). S2: Conduct a trial lift of the steel box girder, with a lifting height of less than 200mm, and observe the mechanical performance of the crane; S3: Slowly lift the steel box girder and transport it to the installation position, using guy ropes for traction to prevent the steel box girder from rotating horizontally; S4: After being hoisted to the installation position, the hoisted steel box girder and the already installed steel box girder are connected by the combined extension unit (5) to complete the installation.

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