Installation method of main beam of lifting platform for construction of expressway three-dimensional extension in narrow space

Abstract

The application discloses a kind of installation methods of narrow space highway three-dimensional extension construction lifting platform girder, comprising: S1, construction preparation: install platform foundation between the front end pier column of installed steel box girder and the pier column of next span;S2, main girder hoisting bridge: hoist main girder to beam surface in non-restricted site, carry main girder by beam trolley;S3, install temporary pushing device: install temporary pushing device on the beam surface of installed steel box girder and platform foundation top surface, translate main girder from beam trolley to the top of platform foundation by temporary pushing device;S4, beam falling: drive platform foundation to drive main girder downlink with installed steel box girder beam surface at the same horizontal plane, connect main girder and platform foundation, complete main girder beam falling installation.The application realizes the safe, stable and efficient installation of super large and super heavy steel member main girder under the condition of narrow space in highway, and does not block the highway under the bridge, which ensures the normal operation of existing highway trunk road and has good applicability.

Description

Technical Field

[0001] This invention relates to the field of highway bridge expansion technology. More specifically, this invention relates to a method for installing the main beam of a construction lifting platform for highway expansion in narrow spaces. Background Technology

[0002] Traditional temporary construction equipment, such as construction hoisting platforms, is erected between the front pier of an already installed steel box girder and the pier of the next span. It is used for installation work from the front of the installed steel box girder to the next span of the beam to be installed. When installing a construction hoisting platform, the platform foundation is installed first, and then a crane is used to lift the main beam of the construction hoisting platform onto the platform foundation from the ground. The main beam is an ultra-long and ultra-heavy component, requiring significant site foundation strength for its hoisting. Furthermore, the crane's positioning and hoisting height must be appropriate, the construction space must accommodate the crane's boom rotation, and workers are needed to assist with positioning and connection.

[0003] However, this method is not suitable for installing the main beam of an ultra-long and ultra-heavy construction lifting platform in the narrow urban space of the super-long and ultra-heavy construction main road expansion project. Due to the narrow median strip of the urban expressway, the construction space is limited. The installation height is 30 meters, the main beam component is 38.4 meters long and weighs 248 tons. The narrow construction space makes it difficult to meet the needs of component transportation and crane positioning at the same time. Moreover, under the condition of maintaining the traffic flow of the expressway main road, it is close to the existing operating expressway and encroaches on the line, resulting in high safety risks for the hoisting operation.

[0004] Currently, the following two methods are also used for the transportation and installation of ultra-long and ultra-heavy steel beams: 1) The steel beams are placed on the bridge in areas with good space and gradually pushed into place by long-span jacking equipment. However, this method requires pushing the steel beams over a long distance in narrow urban spaces. For the main beam of the lifting platform of the temporary construction structure, the transportation efficiency is extremely low, which seriously restricts the on-site construction period. 2) The steel beams are manufactured in sections, and the lifting equipment hoists them to the bridge deck one section at a time. Then the steel beams are assembled on the bridge deck and slid to the predetermined position via slide rails. However, this method still relies on hoisting onto the roof, which is not suitable for hoisting large sections of steel beams in narrow median spaces. It also requires sliding the working surface, which poses a high risk for sliding steel beams on curved bridge decks. It is also not suitable for installing the main beam of the construction lifting platform for highway expansion in narrow urban spaces.

[0005] Therefore, given the development needs of highway reconstruction, expansion, and upgrading, there is an urgent need to provide a high-efficiency and low-risk installation method for the main beam of an ultra-long and ultra-heavy construction lifting platform for highway expansion in confined spaces. Summary of the Invention

[0006] The purpose of this invention is to provide a method for installing the main beam of a three-dimensional construction lifting platform for highway expansion in narrow spaces, which enables safe, stable, and efficient installation of ultra-large and ultra-heavy steel structural beams in the narrow space of the median strip of a highway, without blocking the highway road under the bridge, thus ensuring the normal operation of the existing highway trunk road. This method is highly applicable to the construction of highway expansion in narrow spaces.

[0007] To achieve these objectives and other advantages according to the present invention, a method for installing the main beam of a highway vertical expansion construction lifting platform in a narrow space is provided, comprising the following steps: S1. Construction preparation: Install a platform foundation between the front pier of the installed steel box girder and the pier of the next span; install a beam surface track along the longitudinal direction of the bridge on the installed steel box girder, and set up a beam transport trolley on the track; the platform foundation is a liftable structure. S2. Main beam lifting onto the bridge: Assemble the main beam in an unrestricted area and lift it onto the beam surface. The main beam is then carried by the beam transport trolley along the paving direction of the track to the front pier of the installed steel box girder. S3. Install temporary jacking devices: Install the first temporary jacking device and the second temporary jacking device on the surface of the installed steel box girder and the top surface of the platform foundation, respectively. Use the first temporary jacking device and the second temporary jacking device to move the main girder from the girder transport trolley to directly above the second temporary jacking device. S4. Lowering the beam: Drive the platform foundation to move the main beam down to the same horizontal plane as the installed steel box girder surface. Remove the second temporary jacking device, connect the main beam and the platform foundation, and complete the lowering and installation of the main beam.

[0008] Preferably, in step S2, assembling the main beam and hoisting it to the beam surface includes: assembling the main beam at the gantry crane hoisting site, and then hoisting it to the beam surface by the gantry crane after assembly.

[0009] Preferably, in step S1, after the platform foundation is installed, temporary consolidation structures are installed between the two ends of the platform foundation and the adjacent piers to connect the platform foundation and the piers into an integral load-bearing system.

[0010] Preferably, in step S3, the first temporary jacking device includes a plurality of support piers spaced apart along the longitudinal direction of the bridge, and a jacking device disposed on the support piers. The plurality of support piers are distributed directly below the main beam. The jacking device includes lifting jacks, transverse jacks and longitudinal jacks. The lifting jacks, transverse jacks and longitudinal jacks are used to drive the main beam to move vertically, longitudinally and transversely, respectively. The second temporary jacking device includes multiple identical support blocks and jacking devices installed on the support blocks.

[0011] Preferably, in step S3, moving the main beam from the beam transport trolley to directly above the second temporary jacking device using the first and second temporary jacking devices includes: Lowering the beam into position: The hydraulic cylinder of the beam transport trolley retracts, causing the main beam to descend to the bottom of the main beam and abut against the top of the multiple lifting jacks of the first temporary jacking device. The main beam is supported by multiple supporting piers of the first temporary jacking device. Vertical jacking: Simultaneously drive multiple jacking jacks of the first temporary jacking device to jack the main beam to the design height and support the main beam; Longitudinal jacking: The free ends of multiple longitudinal jacks of the first temporary jacking device are extended synchronously, pushing the main beam forward one jacking stroke along the longitudinal bridge; Vertical beam lowering: The free ends of multiple lifting jacks of the first temporary jacking device are retracted synchronously, and the main beam is placed on multiple support piers, which support the main beam. Reset cycle: Synchronously drive multiple longitudinal jacks to retract, waiting for the next jacking operation; Repeat the above steps to gradually push the main beam to the top of the second temporary jacking device; during the jacking process, the alignment of the main beam is adjusted by the horizontal jacks.

[0012] Preferably, during the process of the main beam being moved as a whole from the beam transport trolley to the second temporary jacking device, when the main beam is jacked up to the point where its front section is on the second temporary jacking device, the load of the front section of the main beam is borne by the second temporary jacking device. Thereafter, the first and second temporary jacking devices work together to simultaneously jack the main beam forward until the main beam is directly above the second temporary jacking device.

[0013] Preferably, the platform foundation includes multiple platform units spaced longitudinally along the bridge, each platform unit includes multiple supports spaced transversely along the bridge, each support has a lifting mechanism at its top, the fixed end of the lifting mechanism is fixedly mounted on the corresponding support, and the free end is vertically upward and fixedly connected to the column, multiple columns of any platform unit are connected into a whole by crossbeams, trusses are detachably connected between adjacent crossbeams, and multiple support piers are respectively mounted on multiple crossbeams.

[0014] Preferably, in step S4, dismantling the second temporary jacking device includes: The two ends of the main beam are connected to the installed steel box girder and the adjacent pier column to form a whole; Remove the truss located at the front section of the main beam, drive multiple lifting mechanisms on the corresponding platform unit to descend, drive the crossbeam to descend, and then remove the support pier and jacking device of that section. Drive multiple lifting mechanisms upwards until the crossbeam abuts against the main beam, and fix the crossbeam and main beam in place; Repeat the above steps, removing multiple support piers and jacking devices installed on the support piers in the opposite direction to the main beam's forward direction, until all support piers and jacking devices are removed, and multiple crossbeams are connected to the main beam to form a whole, completing the main beam lowering and installation.

[0015] Preferably, before removing any support pier, the beam transport vehicle is driven to the preset position of the main beam, and then the support pier and jacking device at the corresponding position are removed.

[0016] This invention offers at least the following advantages: It allows for the hoisting of the main beam onto the bridge from a distant, unrestricted location, avoiding hoisting operations in confined urban spaces. The main beam is then transported to the pier column of the pre-installed steel box girder using pre-installed steel box girder rails and a beam-carrying trolley, avoiding long-distance jacking operations. This improves construction efficiency and reduces operational risks. A temporary jacking device is used near the restricted work area to jack the main beam in a space-constrained location, and the platform foundation's lifting function facilitates beam lowering, preventing construction encroachment. Simultaneously, the pre-installed steel box girder acts as a barrier, ensuring the continued operation of the existing highway. Ultimately, this invention achieves safe, stable, and efficient installation of ultra-large and ultra-heavy steel main beams in the narrow space of the highway median strip, without blocking the highway under the bridge, thus ensuring the normal operation of the existing highway mainline. It demonstrates good applicability and promising application prospects.

[0017] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating a method for installing the main beam of a construction lifting platform for highway expansion in a narrow space, according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure for lifting the main beam onto the bridge according to the present invention; Figure 3 This is a schematic diagram of the beam transport vehicle structure of the present invention; Figure 4 This is a schematic diagram of the structure of the present invention, which uses a temporary jacking device to jack up the main beam. Figure 5 This is a schematic diagram of the structure of the present invention, showing the main beam being pushed to the top of the platform foundation. Figure 6 This is a schematic diagram of the structure for removing the support pier according to the present invention; Figure 7 This is a schematic diagram of the structure for removing the support pier according to the present invention; Figure 8 This is a schematic diagram of the connection between the main beam and the crossbeam of the present invention; Figure 9 This is a schematic diagram of the basic structure of the platform of the present invention; Figure 10 This is a top view of the main beam of the present invention; Explanation of reference numerals on the accompanying drawings: 1. Main beam, 2. Support frame, 3. Crossbeam, 4. Column, 5. Lifting mechanism, 6. Truss, 7. Installed steel box girder, 8. Pier, 9. Support pier, 10. Beam transport trolley, 11. Gantry crane, 12. Temporary fixed structure, 13. Pushing device. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0020] It should be noted that in the description of this invention, the terms "lateral", "longitudinal", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] like Figure 1-10 As shown, the present invention provides a method for installing the main beam of a construction lifting platform for highway expansion in narrow spaces, comprising the following steps: S1. Construction preparation: Install a platform foundation between the front pier 8 of the installed steel box girder 7 and the pier 8 of the next span. Install a beam surface track along the longitudinal direction of the bridge on the installed steel box girder 7. A beam transport trolley 10 is set on the track. Adjust the beam transport trolley 10 to meet the transportation conditions of the main beam 1. The platform foundation is a liftable structure. S2, such as Figure 2 , Figure 3 As shown, the main beam 1 is lifted onto the bridge: the main beam 1 is assembled in an unrestricted area and lifted to the beam surface. The main beam 1 is carried by the beam transport trolley 10 along the paving direction of the track to the front pier 8 of the installed steel box girder 7. S3, such as Figure 4 , Figure 5 As shown, a temporary jacking device is installed: After the beam transport trolley 10 is transported to the position, the first temporary jacking device and the second temporary jacking device are installed at the corresponding positions on the beam surface of the installed steel box girder 7 and the top surface of the platform foundation, respectively. The main beam 1 is moved from the beam transport trolley 10 to directly above the second temporary jacking device by the first temporary jacking device and the second temporary jacking device. S4, such as Figure 6-8As shown, the main beam is lowered: the driving platform foundation drives the main beam 1 down to the same horizontal plane as the top surface of the main beam 1 and the surface of the installed steel box girder 7. The second temporary jacking device is removed, the main beam 1 and the platform foundation are connected, and the installation of the main beam 1 is completed.

[0022] In the above technical solution, the present invention hoists the main beam 1 onto the bridge from a remote, unrestricted location, avoiding hoisting operations in narrow urban spaces. Subsequently, the main beam 1 is transported to the pier column 8 of the pre-installed steel box girder 7 using the pre-installed steel box girder 7 beam surface track and beam transport trolley 10, avoiding long-distance jacking operations, which can improve construction efficiency and reduce operational risks. A temporary jacking device is used near the restricted working surface to jack the main beam 1 in a space-constrained location, and the lifting function of the platform foundation is used to realize the beam lowering, avoiding the problem of construction encroachment. At the same time, the pre-installed steel box girder 7 below acts as a barrier, ensuring the smooth operation of the existing highway. Ultimately, the invention achieves safe, stable, and efficient installation of the ultra-large and ultra-heavy steel main beam 1 in the narrow space of the median strip of the highway, while not blocking the highway under the bridge, ensuring the normal operation of the existing highway main road. It has good applicability and good application prospects.

[0023] In another technical solution, step S2, assembling the main beam 1 and hoisting the main beam 1 to the beam surface, includes: assembling the main beam 1 at the hoisting site of the gantry crane 11, and after the assembly is completed, being hoisted to the beam surface by the gantry crane 11.

[0024] In this technical solution, the main beam 1 is assembled at the hoisting site of the gantry crane 11 and then hoisted by the gantry crane 11. All assembly operations are carried out on the ground, ensuring high welding quality and high precision in alignment control. This avoids the need for reassembly operations after hoisting at height, resulting in low construction safety risks. The gantry crane 11 also offers high efficiency in lifting the beam and minimizes traffic disruption.

[0025] In another technical solution, in step S1, after the platform foundation is installed, a temporary consolidation structure 12 is installed between the two ends of the platform foundation and the adjacent pier 8, and the platform foundation and the pier 8 are connected into an integral load-bearing system through the temporary consolidation structure 12.

[0026] In this technical solution, after the platform foundation is installed, the platform foundation and the pier column 8 are connected into an integral load-bearing system through a temporary consolidation structure 12. This ensures the load-bearing capacity and overturning resistance of the platform foundation, providing reliable working conditions for the subsequent jacking of the main beam 1 above the platform foundation and its safe lowering. The temporary consolidation structure 12 is an adjustable strut, with both ends of the strut hinged to the platform foundation and the pier column 8, respectively.

[0027] In another technical solution, in step S3, the first temporary jacking device includes a plurality of support piers 9 spaced apart along the longitudinal direction of the bridge, and a jacking device 13 disposed on the support piers 9. The plurality of support piers 9 are distributed directly below the main beam 1. The jacking device 13 includes a lifting jack, a transverse jack and a longitudinal jack. The lifting jack, the transverse jack and the longitudinal jack are respectively used to drive the main beam 1 to move vertically, longitudinally and transversely. The second temporary jacking device includes multiple identical support blocks 9 and a jacking device 13 installed on the support blocks 9.

[0028] In this technical solution, the vertical support of the main beam 1 and the lateral correction of the main beam 1 within a small range during the jacking process are achieved by using the support pier 9 and the three-way jack, resulting in high construction control precision.

[0029] In another technical solution, step S3, which involves using a first temporary jacking device and a second temporary jacking device to move the main beam 1 from the beam transport trolley 10 to directly above the second temporary jacking device, includes: Lowering the beam into position: The hydraulic cylinder of the beam transport trolley 10 retracts, causing the main beam 1 to descend to the bottom of the main beam 1 and abut against the top of the multiple lifting jacks of the first temporary jacking device. The main beam 1 is supported by the multiple support piers 9 of the first temporary jacking device, completing the force system conversion. Vertical jacking: Simultaneously drive multiple jacking jacks of the first temporary jacking device to jack vertically, supporting the main beam 1 and jacking the main beam 1 to the design height; Longitudinal jacking: The free ends of multiple longitudinal jacks of the first temporary jacking device are extended synchronously, pushing the main beam 1 forward along the longitudinal bridge by one jacking stroke; Vertical beam lowering: The free ends of multiple lifting jacks of the first temporary jacking device are retracted synchronously, and the main beam 1 is placed on multiple support piers 9, and the main beam 1 is supported by the support piers 9. Reset cycle: Synchronously drive multiple longitudinal jacks to retract, waiting for the next jacking operation; Repeat the above steps of vertical lifting, longitudinal pushing, vertical beam lowering, and reset cycle to achieve the step-by-step advancement of the main beam 1, so as to gradually push the main beam 1 onto the second temporary pushing device and place it directly above the installation position of the main beam 1; during the pushing process, the alignment of the main beam 1 is adjusted by the horizontal jacks. During the process of moving the main beam 1 from the beam transport trolley 10 to the second temporary jacking device, when the main beam 1 is jacked to the point where its front section is on the second temporary jacking device, the load of the front section of the main beam 1 is borne by the second temporary jacking device. After that, the first and second temporary jacking devices work together synchronously to jack the main beam 1 forward until the main beam 1 is directly above the second temporary jacking device.

[0030] In this technical solution, the main beam 1 is pushed by the first and second temporary jacking devices working together. The beam transport trolley 10 does not move or participate in the operation during the jacking process, which avoids the frequent start-stop and longitudinal movement of the beam transport trolley 10 under heavy load, fundamentally eliminating safety hazards such as slippage and over-limit. The process is simple and the risk is low.

[0031] In another technical solution, the platform foundation includes multiple platform units spaced longitudinally along the bridge. Each platform unit includes multiple supports 2 spaced transversely along the bridge. Each support 2 is equipped with a lifting mechanism 5 at its top. The fixed end of the lifting mechanism 5 is fixedly mounted on the corresponding support 2, and the free end is vertically upward and fixedly connected to the column 4. The multiple columns 4 of any platform unit are connected into a whole by crossbeams 3. Adjacent crossbeams 3 are detachably connected by trusses 6. Multiple support piers 9 are respectively mounted on multiple crossbeams 3.

[0032] In this technical solution, such as Figure 9 As shown, the platform foundation consists of multiple platform units spaced longitudinally along the bridge. Each platform unit includes multiple supports 2, and a lifting mechanism 5 is installed on the supports 2. The lifting mechanism 5 can be a lifting cylinder, which realizes the lifting function of the platform foundation. The multiple supports 2 of any platform unit are connected into a whole by crossbeams 3, which can improve the synchronization of lifting between multiple supports 2. Adjacent crossbeams 3 are detachably connected by trusses 6, which can improve the integrity and stability of the platform foundation. The detachable design allows two adjacent platform units to form independent lifting units, which facilitates the subsequent dismantling of multiple support piers 9 and jacking devices 13.

[0033] In another technical solution, in step S4, dismantling the second temporary jacking device includes: After the main beam 1 is positioned for installation, its two ends are connected to the already installed steel box girder 7 and the adjacent pier column 8 respectively through connectors to form a whole, thereby improving the stability of the main beam 1 installation. First connecting plates can be welded to both sides of the rear end of the main beam 1, and second connecting plates can be welded to both sides of the end of the already installed steel box girder. The first and second connecting plates are connected to each other by bolts to form a whole, thereby connecting the main beam 1 to the already installed steel box girder. The front end of the main beam 1 is hinged to the pier column through an adjustable strut. The truss 6 located at the front section of the main beam 1 is removed, and the connection constraints of the two platform units are released. The platform unit near the rear end of the main beam 1 is also connected to other platform units through the truss. Therefore, the platform unit near the front end of the main beam 1 is separated into an independent liftable unit. Multiple lifting mechanisms 5 on the platform unit are driven downwards, which in turn drives the crossbeam 3 on it downwards. The downward movement of the crossbeam 3 drives the support piers on the crossbeam 3 downwards away from the main beam 1, providing space for the dismantling of the support piers. Then, the support piers and the jacking device 13 on the platform unit are removed. Multiple lifting mechanisms 5 on the platform unit are driven to move upward until the crossbeam 3 abuts against the main beam 1, and the crossbeam 3 and the main beam 1 are fixedly connected by flange bolts. Repeat the above steps, and remove multiple support blocks 9 and the jacking device 13 set on the support blocks 9 in the opposite direction to the forward direction of the main beam 1, until all support blocks and jacking devices 13 are removed, and multiple crossbeams 3 are connected to the main beam 1 to form a whole, thus completing the installation of the main beam 1. Before removing any of the supporting piers, drive the beam transport vehicle to the preset position of the main beam 1, and then remove the supporting pier and jacking device 13 at the corresponding position.

[0034] In this technical solution, the main beam 1 is an ultra-long and ultra-heavy component. To ensure stability during the removal of the supporting piers, a counterweight is required before removal to ensure the horizontal stability of the main beam 1 and prevent it from overturning during the removal process, thus improving operational safety. Since the beam transport vehicle is located at the rear end of the main beam 1, multiple supporting piers 9 and the jacking device 13 installed on the supporting piers 9 are removed sequentially in the opposite direction to the forward direction of the main beam 1. This dismantling sequence can fully utilize the counterweight effect to ensure a smooth transition of the load of the main beam 1 to the lifting platform crossbeam 3, avoiding a sudden increase in cantilever negative bending moment and load impact, thus ensuring structural safety. During dismantling, only one platform unit is separated at a time, and the main beam is supported by other platform units. The connection between the main beam and the crossbeam can be completed crosswise while ensuring the stability of the main beam 1, further ensuring construction safety.

[0035] The installation method of the main beam 1 of the highway three-dimensional expansion construction lifting platform in narrow spaces of the present invention enables stable and efficient transportation and installation of ultra-long and ultra-heavy structures under bridges with high traffic control and narrow working spaces. It effectively overcomes key bottlenecks in highway three-dimensional expansion construction and provides a working platform for the jacking and transportation installation of bridge steel box girders. It provides a reference solution for the transportation and installation of ultra-long and ultra-heavy components above existing roads in the field of bridge reconstruction and expansion, and has good application prospects. The present invention is applicable to the transportation and installation of "ultra-large and ultra-heavy" components under general conditions of narrow spaces, high traffic control, and high safety and stability requirements, including steel structures and concrete beam structures.

[0036] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for installing the main beam of a lifting platform for highway expansion construction in narrow spaces, characterized in that, Includes the following steps: S1. Construction preparation: Install a platform foundation between the front pier of the installed steel box girder and the pier of the next span; install a beam surface track along the longitudinal direction of the bridge on the installed steel box girder, and set up a beam transport trolley on the track; the platform foundation is a liftable structure. S2. Main beam lifting onto the bridge: Assemble the main beam in an unrestricted area and lift it onto the beam surface. The main beam is then carried by the beam transport trolley along the paving direction of the track to the front pier of the installed steel box girder. S3. Install temporary jacking devices: Install the first temporary jacking device and the second temporary jacking device on the surface of the installed steel box girder and the top surface of the platform foundation, respectively. Use the first temporary jacking device and the second temporary jacking device to move the main girder from the girder transport trolley to directly above the second temporary jacking device. S4. Lowering the beam: Drive the platform foundation to move the main beam down to the same horizontal plane as the installed steel box girder surface. Remove the second temporary jacking device, connect the main beam and the platform foundation, and complete the lowering and installation of the main beam.

2. The method for installing the main beam of the highway three-dimensional expansion construction lifting platform in a narrow space as described in claim 1, characterized in that, In step S2, assembling the main beam and hoisting it to the beam surface includes: assembling the main beam at the gantry crane hoisting site, and then hoisting it to the beam surface by the gantry crane after assembly.

3. The method for installing the main beam of the highway three-dimensional expansion construction lifting platform in a narrow space as described in claim 1, characterized in that, In step S1, after the platform foundation is installed, temporary consolidation structures are installed between the two ends of the platform foundation and the adjacent piers to connect the platform foundation and the piers into an integrated load-bearing system.

4. The method for installing the main beam of the highway three-dimensional expansion construction lifting platform in a narrow space as described in claim 1, characterized in that, In step S3, the first temporary jacking device includes multiple support piers spaced apart along the longitudinal direction of the bridge, and a jacking device set on the support piers. The multiple support piers are distributed directly below the main beam. The jacking device includes lifting jacks, transverse jacks and longitudinal jacks. The lifting jacks, transverse jacks and longitudinal jacks are used to drive the main beam to move vertically, longitudinally and transversely, respectively. The second temporary jacking device includes multiple identical support blocks and jacking devices installed on the support blocks.

5. The method for installing the main beam of the highway three-dimensional expansion construction lifting platform in a narrow space as described in claim 4, characterized in that, In step S3, moving the main beam from the beam transport trolley to directly above the second temporary jacking device using the first and second temporary jacking devices includes: Lowering the beam into position: The hydraulic cylinder of the beam transport trolley retracts, causing the main beam to descend to the bottom of the main beam and abut against the top of the multiple lifting jacks of the first temporary jacking device. The main beam is supported by multiple supporting piers of the first temporary jacking device. Vertical jacking: Simultaneously drive multiple jacking jacks of the first temporary jacking device to jack the main beam to the design height and support the main beam; Longitudinal jacking: The free ends of multiple longitudinal jacks of the first temporary jacking device are extended synchronously, pushing the main beam forward one jacking stroke along the longitudinal bridge; Vertical beam lowering: The free ends of multiple lifting jacks of the first temporary jacking device are retracted synchronously, and the main beam is placed on multiple support piers, which support the main beam. Reset cycle: Synchronously drive multiple longitudinal jacks to retract, waiting for the next jacking operation; Repeat the above steps to gradually push the main beam to the top of the second temporary jacking device; during the jacking process, the alignment of the main beam is adjusted by the horizontal jacks.

6. The method for installing the main beam of the highway three-dimensional expansion construction lifting platform in a narrow space as described in claim 5, characterized in that, During the process of the main beam being moved from the beam transport trolley to the second temporary jacking device, when the main beam is jacked up to the point where its front section is on the second temporary jacking device, the load of the front section of the main beam is borne by the second temporary jacking device. After that, the first and second temporary jacking devices work together to push the main beam forward synchronously until the main beam is directly above the second temporary jacking device.

7. The method for installing the main beam of the highway three-dimensional expansion construction lifting platform in a narrow space as described in claim 4, characterized in that, The platform foundation includes multiple platform units spaced longitudinally along the bridge. Each platform unit includes multiple supports spaced laterally along the bridge. Each support is equipped with a lifting mechanism at its top. The fixed end of the lifting mechanism is fixedly mounted on the corresponding support, and the free end is vertically upward and fixedly connected to the column. Multiple columns of any platform unit are connected into a whole by crossbeams. Adjacent crossbeams are detachably connected by trusses. Multiple support piers are respectively set on multiple crossbeams.

8. The method for installing the main beam of the highway three-dimensional expansion construction lifting platform in a narrow space as described in claim 7, characterized in that, In step S4, dismantling the second temporary jacking device includes: The two ends of the main beam are connected to the installed steel box girder and the adjacent pier column to form a whole; Remove the truss located at the front section of the main beam, drive multiple lifting mechanisms on the corresponding platform unit to descend, drive the crossbeam to descend, and then remove the support pier and jacking device of that section. Drive multiple lifting mechanisms upwards until the crossbeam abuts against the main beam, and fix the crossbeam and main beam in place; Repeat the above steps, removing multiple support piers and jacking devices installed on the support piers in the opposite direction to the main beam's forward direction, until all support piers and jacking devices are removed, and multiple crossbeams are connected to the main beam to form a whole, completing the main beam lowering and installation.

9. The method for installing the main beam of the highway three-dimensional expansion construction lifting platform in a narrow space as described in claim 8, characterized in that, Before removing any of the supporting piers, drive the beam transport vehicle to the preset position of the main beam, and then remove the supporting pier and jacking device at the corresponding position.

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