Integral folding method for large-section box-truss combined steel beam

Abstract

The invention relates to an integral closure method for a large-section box-truss combined steel beam, and belongs to the technical field of bridge closure. Comprising the following steps: S1, preparation before folding; s2, calculating the matching and cutting amount; s3, re-checking measurement is carried out, the spatial postures of erected steel beams on the two sides of the closure section are adjusted to meet the closure requirement, the erected steel beams are continuously monitored for 48 hours, the change rule of closure gaps along with the temperature is obtained, and the precise matching and cutting size and closure time of the closure section are determined; s4, matching and cutting determination; s5, closure section carrying; s6, hoisting testing; s7, hoisting adjustment; s8, a closure section steel beam is lifted; s9, the posture of the steel beam is adjusted; s10, longitudinal temporary locking is carried out; s11, a lower chord longitudinal beam closure opening of the steel beam is adjusted; s12, temporary folding is conducted; s13, permanent folding is carried out; the problems that due to the fact that the structural size and tonnage of the closure section are small, closure time is long, closure efficiency is low, and channel passing is affected are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge closure, and in particular relates to a method for integrally closing a large-segment box-truss composite steel beam. Background Art

[0002] Bridge closure (also known as bridge closing) is a sign of the completion of the main structure of the bridge. It is also the most critical, important, technically demanding and difficult part of bridge construction. At present, in the construction of cable-stayed bridges with steel beams or steel-concrete composite beams, the middle span closure construction usually adopts two methods: temperature matching closure and top-pushing closure. In the temperature matching closure construction method, the closure section steel beam is first made according to the design requirements at the beam manufacturing site, and then the closure temperature is determined according to the closure construction period. The gap of the closure mouth at this temperature is measured, and according to the measurement results, the closure section steel beam is cut and the interface is processed. Four bridge cranes are used to hoist the closure section steel beam into place and adjust it into place. After the closure section steel beam reaches the closure temperature and enters the gear, welding construction is carried out.

[0003] During closing, components may be displaced or deviated due to various factors (such as temperature change, material deformation, etc.). Therefore, pre-biased longitudinal shift can be used to adjust the position of components before closing so that they can be smoothly docked during closing. However, the structural dimensions and tonnage of the closing section are small, and the stability of positioning and adjustment is usually poor due to its light weight. Therefore, during pre-biased longitudinal shift, light structures will be more obviously affected by the external environment (such as wind, vibration, etc.), resulting in more time required to ensure the accuracy of their position during the adjustment process, resulting in a longer closing time and low closing efficiency. If the closing mouth is on the waterway, it will also affect the passage of the waterway for a long time. Summary of the invention

[0004] In order to solve the above-mentioned problems existing in the prior art, the present invention provides a method for overall closure of large-segment box truss composite steel beams, which solves the problem that the closure section structural size and tonnage are small, resulting in a long closure time, low closure efficiency and affecting channel navigation.

[0005] The object of the present invention can be achieved by the following technical solution: A method for integrally closing a large-segment box truss composite steel beam comprises the following steps:

[0006] S1: Preparation before closing: assemble the main span steel beams segment by segment using the bridge crane, complete the erection of the main span steel beams and the grouting of the main pier supports, and temporarily lock the main pier movable supports longitudinally;

[0007] S2: Calculate the amount of cutting, conduct joint measurement on the erected main span steel beams, determine the spatial posture of the closing end rings of adjacent steel beams on both sides of the closing section, calculate the amount of cutting and perform cutting on the rings of the erected beam sections;

[0008] S3: Conduct recheck measurements, adjust the spatial posture of the erected steel beams on both sides of the closing section to meet the closing requirements, monitor the erected steel beams for 48 hours continuously, obtain the change law of the closing gap with temperature, and determine the precise cutting size of the closing section and the closing time;

[0009] S4: Cutting determination: according to the continuous monitoring data analysis, the cutting amount and cutting posture of the ring mouth of the closing section are determined, and the wedge cutting is performed on the steel beam box truss of the closing section as a whole;

[0010] S5: Transportation of the closing section: the original steel beams of the closing section that have been cut are transported to the bottom of the steel beams at the closing mouth by a transport ship. After the ship drops anchor and positions, a large-tonnage bridge crane lowers the spreader to connect the spreader with the steel beam;

[0011] S6: Hoisting test: the bridge crane is loaded step by step. Each load level is monitored during the loading process, and the bridge crane hoist, front support, rear anchor point and structural stress values ​​are monitored in real time;

[0012] S7: Hoisting adjustment: when the steel beam of the closing section is 20-30cm away from the transport ship, the lifting is stopped and the initial posture of the steel beam of the closing section is adjusted by the bridge crane;

[0013] S8: Lift the steel beam of the closing section, and monitor the posture change of the steel beam through the inclinometer throughout the whole process. When the inclination of the steel beam reaches the preset value, stop lifting, adjust the posture of the steel beam of the closing section, and continue lifting when the requirements are met;

[0014] S9: Adjust the posture of the steel beam. When the top surface of the box beam of the closure section is about to be flush with the bottom surface of the box beam of the erected section, stop lifting and observe whether the gap between the end of the closure section and the erected section reaches the preset value. If there is a deviation, adjust the posture of the steel beam.

[0015] S10: Longitudinal temporary locking. When the steel beam of the closing section is lifted to the same level as the erected steel beam, the bridge crane’s longitudinal amplitude change, elevation lifting and lowering, and lateral movement functions are used to adjust the closing opening of the lower chord longitudinal beam of the steel beam on the fixed support side according to the closing construction sequence. After the closing opening is aligned in three directions, the anchor box and steel rod on the lower chord bridge deck are used to perform longitudinal temporary locking.

[0016] S11: Adjust the closing mouth of the lower chord and longitudinal beam of the steel beam, and adjust the elevation and lateral displacement deviation through the bridge crane. After the adjustment is in place, temporarily lock it immediately to release the longitudinal constraint of the movable support;

[0017] S12: Temporary closing: After the lower chord longitudinal beams at both ends of the closing section are temporarily locked, the lateral adjustment is performed through the closing adjustment anchor box on the upper chord member. After the adjustment is in place, temporary locking is performed to complete the temporary closing;

[0018] S13: Permanent closure. After the temporary locking of the closing mouth rods is completed, check their flatness and the closing mouth welding gap. After the inspection is completed, weld the lower chord longitudinal beam, upper chord rod and steel box girder in sequence to complete the permanent closure.

[0019] As a preferred technical solution of the present invention, in step S4, the box girder with the closed ring opening of the erected beam section and the ring opening of the upper chord are cut by 25 mm to form an oblique ring opening.

[0020] As a preferred technical solution of the present invention, after the matching and cutting is completed, the center distance between the closing section steel beam and the erected steel beam is greater than 25mm, and when the top plate of the closing section box beam passes the bottom plate of the erected section box beam, the distance is 50mm.

[0021] As a preferred technical solution of the present invention, in step S8, an inclinometer is installed on the beam surface of the closing section steel beam before lifting. The posture changes of the steel beam are transmitted to the command center display screen in real time through wireless transmission, and warning values ​​and limit values ​​are set. During the lifting process, the lateral inclination of the steel beam does not exceed 0.75%, and the longitudinal inclination does not exceed 2%.

[0022] As a preferred technical solution of the present invention, in steps S10-S12, the adjustment accuracy of the bridge crane is 10 mm.

[0023] As a preferred technical solution of the present invention, in step S12, the diagonal web members on both sides of the steel beam of the closing section are removed in advance and then installed on site after the steel beam is closed.

[0024] As a preferred technical solution of the present invention, in step S13, when closing, the ring mouth is matched first with the lower chord bar, then with the upper chord bar, and finally with the box girder ring mouth.

[0025] The beneficial effects of the present invention are as follows: utilizing the linear relationship between the deformation of the steel structure and the temperature, establishing the corresponding linear parameters of the steel beams at different temperatures, and determining the cutting amount of the steel beams in the closing section, thereby avoiding the situation in which the design temperature is inconsistent with the actual temperature during closing, resulting in the beam length at the actual temperature being inconsistent with the beam length at the original design temperature. At the same time, by using a large-tonnage bridge crane to lift and close the structure in situ, the problem of small structural size and tonnage of the closing section is avoided, the processes such as pre-biased longitudinal shifting are reduced, the closing time is shortened, the time of occupying the waterway is shortened, work efficiency is increased, and costs are saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0027] Figure 1 This is a schematic diagram of the erected main span steel beam and the closure section steel beam to be erected in the present invention;

[0028] Figure 2This is a connection diagram of the bridge deck crane hoist and the closure section steel beam of the present invention;

[0029] Figure 3 This is a diagram of the bridge deck crane lifting the closure section steel beam of the present invention;

[0030] Figure 4 This is a diagram of the closing section steel beam of the present invention being hoisted in situ and about to be closed;

[0031] Figure 5 This is a diagram of the in-situ closing state of the closing section steel beam of the present invention;

[0032] Main component symbols

[0033] In the figure: 1. Closing section steel beam; 2. Bridge crane; 3. Hoisting equipment; 4. Main span steel beam; 5. Transport ship; 6. Movable support; 7. Anchor box; 8. Diagonal brace. DETAILED DESCRIPTION

[0034] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0035] See also Figure 1-Figure 5 This embodiment provides a method for integrally closing a large-segment box truss composite steel beam, comprising the following steps:

[0036] S1: Preparation before closing: assemble the main span steel beam 4 segment by segment using the bridge crane 2, complete the erection of the main span steel beam 4 and the grouting of the main pier support, and temporarily lock the main pier movable support 6 longitudinally;

[0037] S2: Calculate the amount of cutting, conduct joint measurement on the erected main span steel beam 4, determine the spatial posture of the closed end rings of the adjacent steel beams on both sides of the closed section, calculate the amount of cutting and perform cutting on the rings of the erected beam section;

[0038] S3: Conduct recheck measurements, adjust the spatial posture of the erected steel beams on both sides of the closing section to meet the closing requirements, monitor the erected steel beams for 48 hours continuously, obtain the change law of the closing gap with temperature, and determine the precise cutting size of the closing section and the closing time;

[0039] S4: Cutting determination: according to the continuous monitoring data analysis, the cutting amount and cutting posture of the ring mouth of the closing section are determined, and the wedge cutting is performed on the box girder 1 of the closing section steel beam as a whole;

[0040] S5: Transportation of the closing section. The original closing section steel beam 1 that has been cut is transported to the bottom of the closing mouth steel beam by the transport ship 5. After the ship drops anchor and positions, the large-tonnage bridge crane 2 lowers the lifting device 3 to connect the lifting device 3 with the steel beam. At the same time, the connection between the rear anchor point, the front support point and the lifting device 3 of the large-tonnage bridge crane 2 is checked. After all the inspections meet the requirements, the closing section steel beam 1 is loaded and lifted step by step.

[0041] S6: Hoisting test, the bridge crane 2 is loaded step by step. During the loading process, a dedicated person is arranged to pay attention to the load display of the bridge crane 2 in real time, report at each level, and monitor the bridge crane 2 hoist 3, front support, rear anchor point and structural stress value in real time. The observers on the deck pay attention to the separation of the steel beam and the support pad of the transport ship 5. If the load reaches the theoretical weight and the steel beam still does not separate from the transport ship 5, the loading must be stopped immediately, the load must be maintained, and the stress changes must be paid attention to at any time. A dedicated person is organized to conduct a review and inspection, and the loading will continue after everything is normal;

[0042] S7: hoisting adjustment. When the steel beam 1 of the closing section is 520-30cm away from the transport ship, the lifting is stopped. The initial posture of the closing section steel beam 1 is adjusted by the bridge crane 2 to control the longitudinal and transverse slopes within 0.10%. After the adjustment is in place, the personnel evacuate the beam surface and the inclinometer data of the closing section steel beam 1 is reset to zero.

[0043] S8: lifting the closing section steel beam 1, and monitoring the posture change of the steel beam through the inclinometer throughout the whole process. When the inclination of the steel beam reaches the preset value, the lifting is stopped, and the posture of the closing section steel beam 1 is adjusted. When the requirement is met, the lifting is continued. Or when the inclination of the steel beam keeps increasing without decreasing trend, the lifting is also stopped and adjusted;

[0044] S9: Adjust the posture of the steel beam. When the top surface of the box beam of the closing section is about to be flush with the bottom surface of the box beam of the erected section, stop lifting and observe whether the gap between the end of the closing section and the end of the erected section reaches the preset value. If there is a deviation, adjust the posture of the steel beam. If there is a conflict point between the end of the closing section and the end of the erected section, widen the gap so that the width of the gap at both ends is basically the same, and adjust the longitudinal and transverse slopes to zero;

[0045] S10: Longitudinal temporary locking. When the closing section steel beam 1 is lifted to be substantially flush with the elevation of the erected steel beam, the bridge deck crane 2 is used to adjust the closing opening of the lower chord longitudinal beam of the fixed support side steel beam according to the closing construction sequence by using the longitudinal amplitude change, elevation lifting and lowering, and lateral movement functions. After the closing opening is aligned in three directions, the anchor box 7 and steel rod on the lower chord bridge deck are used to perform longitudinal temporary locking.

[0046] S11: Adjust the closing mouth of the lower chord of the steel beam and the longitudinal beam, adjust the elevation and lateral displacement deviation by the bridge crane 2, and after the adjustment is in place, immediately perform temporary locking to release the longitudinal constraint of the movable support 6. When adjusting the closing section, ensure the accuracy of the closing section position by adjusting the elevation and lateral displacement deviation;

[0047] S12: Temporary closing. After the lower chord longitudinal beams at both ends of the closing section are temporarily locked, the upper chord members of the closing section are basically aligned in elevation. Therefore, it is only necessary to perform lateral adjustment through the closing adjustment anchor box 7 on the upper chord member, so that the longitudinal and lateral positions of the closing section are adjusted. After the adjustment is in place, temporary locking is performed to complete the temporary closing.

[0048] S13: Permanent closure. After the temporary locking of the closing mouth rods is completed, check their flatness and the closing mouth welding gap. After the inspection is completed, weld the lower chord longitudinal beam, upper chord rod and steel box girder in sequence to complete the permanent closure.

[0049] Because different temperatures will affect the expansion and contraction of materials during the process of closing the bridge by temperature matching, if the design temperature is inconsistent with the actual temperature during closing, the beam length converted into the actual temperature will be inconsistent with the beam length at the original design temperature when the bridge is closed. This will cause the internal force of the main beam to be inconsistent with the design. Therefore, in order to avoid this situation, it is necessary to complete the matching and lifting of the steel beams of the closing section under specified temperature conditions. Therefore, the installation of the closing section of the middle span of the steel beam of the cable-stayed bridge is subject to the limited temperature range and construction time. The structural size and tonnage of the closing components are small and are easily affected by the external environment (such as wind, vibration, etc.), which requires more time to ensure the accuracy of its position during the adjustment process, resulting in a long closing time and low closing efficiency.

[0050] Therefore, the present invention utilizes the linear relationship between the deformation of the steel structure and the temperature, establishes the corresponding linear parameters of the steel beams at different temperatures, and determines the cutting amount of the steel beam 1 in the closing section, so as to avoid the situation that the design temperature is inconsistent with the actual temperature during closing, resulting in the beam length at the actual temperature being inconsistent with the beam length at the original design temperature. At the same time, the large-tonnage bridge crane 2 is used for in-situ lifting and closing, which avoids the problem of small structural size and tonnage of the closing section, reduces the processes such as pre-biased longitudinal shifting, shortens the closing time, shortens the time of occupying the waterway, increases work efficiency, and saves costs.

[0051] In order to reduce the structural deformation of the closing section during the closing process, in this embodiment, in step S4, the closing ring box girder and the upper chord ring of the erected beam section are matched by 25mm to form an oblique ring. By beveling the closing ring, the stress concentration can be reduced and the bearing capacity of the connection part can be improved. In addition, the oblique ring can optimize the force transmission path and reduce possible structural deformation, thereby ensuring the safety and durability of the bridge in use. If there are deviations in the mileage and lateral direction of the erected beam section, the closing mouth of the erected beam section must be matched according to the actual data to ensure that the closing can be completed accurately.

[0052] In order to ensure that the closing section steel beam 1 will not interfere with the erected steel beam during the hoisting process, and to ensure the smooth completion of the hoisting, in one embodiment, after the matching is completed, the center distance between the closing section steel beam 1 and the erected steel beam is greater than 25mm, and when the top plate of the closing section box beam passes the bottom plate of the erected section box beam, the distance is 50mm. During hoisting, the distance between the closing section and the erected steel beam should be no less than 25mm to ensure that the closing section will not collide during the hoisting process. At the same time, when the top plate of the closing section box beam passes the bottom plate of the erected section box beam, the distance between the closing section steel beam 1 and the erected steel beam needs to be 50mm to facilitate the subsequent adjustment of the closing section and the welding and closing process.

[0053] In order to accurately control the posture of the hoisted steel beam, ensure the accurate docking between the closed section and the erected beam, and ensure that the construction quality meets the design requirements, in one embodiment, in step S8, an inclinometer is installed on the beam surface of the closed section steel beam 1 before lifting. Through wireless transmission, the changes in the posture of the steel beam are transmitted to the command center display screen in real time, and the warning value and limit value are set. During the hoisting process, the lateral inclination of the steel beam posture does not exceed 0.75%, and the longitudinal inclination does not exceed 2%. By real-time monitoring and displaying the inclination angle of the steel beam, abnormal changes can be discovered in time, so that corresponding measures can be taken to avoid potential safety hazards. The set warning value can alert the operator in advance, thereby reducing the occurrence of accidents and effectively improving construction safety.

[0054] In order to avoid excessive deviation during the closing process, resulting in stress concentration or deformation and causing safety hazards, in one embodiment, in steps S10-S12, the adjustment accuracy of the bridge crane 2 is 10mm, and the anchor boxes 7 for temporary locking and longitudinal and transverse adjustment are all placed on the steel beam in advance and welded on the steel beam. At the same time, temporary tensioning equipment such as steel bars, nuts, through-hole jacks, and top steel strands are used to adjust the position of the closing section during closing. In the actual construction process, too high adjustment accuracy requirements may increase the difficulty of operation and extend the construction time. The lifting equipment will be affected by various factors during adjustment, such as wind force, load characteristics of equipment, etc. At the same time, in the closing process, the longitudinal and transverse adjustments of the components are interrelated, but the adjustment accuracy of 10mm can ensure that when multiple adjustments are made, the coordination and cooperation in various directions are effectively carried out, and a certain space can be left for subsequent inspections and necessary remedial measures after the actual closing. If the adjustment accuracy is too demanding, it may be difficult to make reasonable adjustments when poor docking or other problems are found.

[0055] In order to improve the closing efficiency, in one embodiment, in step S12, the diagonal web members 8 on both sides of the closing section steel beam 1 are removed in advance and installed on site after the steel beam is closed, thereby reducing the closing matching interfaces and improving the closing efficiency. During the closing stage, the diagonal web members 8 will interfere with the operation of the lifting equipment and the precise docking of the steel beam. After removing the diagonal web members 8, it can be ensured that during the closing and temporary locking process, the operating space of the equipment is not restricted, thereby improving the operating accuracy.

[0056] In order to ensure the reasonable distribution of stress between the components after closing, in one embodiment, in step S13, the ring mouth matching during closing is first the lower chord, then the upper chord, and finally the box girder ring mouth. When closing, the box girder closing mouth is adjusted by a "7"-shaped plate and a screw jack, and the plate is welded after the welding requirements are met. Because the lower chord and the upper chord are the main load-bearing components of the bridge, ensuring the matching of their ring mouths is crucial to the stability of the entire structure. First, the lower chord is processed, and then the upper chord is processed, which can effectively and gradually adjust the overall stress state of the structure to ensure the reasonable distribution of stress between the components after closing. After ensuring that the ring mouths of the lower chord and the upper chord are butted, the box girder is closed, which can reduce the influence of deformation or displacement of other parts on the welding quality during the closing process. In addition, the "7"-shaped plate and the screw jack can be used to accurately control the gap of the closing mouth when the ring mouth is butted, reduce the error caused by misalignment or deformation of the parts, and ensure the overall flatness and functionality after closing.

[0057] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for integrally closing a large-segment box truss composite steel beam, characterized in that: The following steps are involved: S1: Preparation before closing: assemble the main span steel beams segment by segment using the bridge crane, complete the erection of the main span steel beams and the grouting of the main pier supports, and temporarily lock the main pier movable supports longitudinally; S2: Calculate the amount of cutting, conduct joint measurement on the erected main span steel beams, determine the spatial posture of the closing end rings of adjacent steel beams on both sides of the closing section, calculate the amount of cutting and perform cutting on the rings of the erected beam sections; S3: Conduct recheck measurements, adjust the spatial posture of the erected steel beams on both sides of the closing section to meet the closing requirements, monitor the erected steel beams for 48 hours continuously, obtain the change law of the closing gap with temperature, and determine the precise cutting size of the closing section and the closing time; S4: Cutting determination: according to the continuous monitoring data analysis, the cutting amount and cutting posture of the ring mouth of the closing section are determined, and the wedge cutting is performed on the steel beam box truss of the closing section as a whole; S5: Transportation of the closing section: the original steel beams of the closing section that have been cut are transported to the bottom of the steel beams at the closing mouth by a transport ship. After the ship drops anchor and positions, a large-tonnage bridge crane lowers the spreader to connect the spreader with the steel beam; S6: Hoisting test: the bridge crane is loaded step by step. Each load level is monitored during the loading process, and the bridge crane hoist, front support, rear anchor point and structural stress values ​​are monitored in real time; S7: Hoisting adjustment: when the steel beam of the closing section is 20-30cm away from the transport ship, the lifting is stopped and the initial posture of the steel beam of the closing section is adjusted by the bridge crane; S8: Lift the steel beam of the closing section, and monitor the posture change of the steel beam through the inclinometer throughout the whole process. When the inclination of the steel beam reaches the preset value, stop lifting, adjust the posture of the steel beam of the closing section, and continue lifting when the requirements are met; S9: Adjust the posture of the steel beam. When the top surface of the box beam of the closure section is about to be flush with the bottom surface of the box beam of the erected section, stop lifting and observe whether the gap between the end of the closure section and the erected section reaches the preset value. If there is a deviation, adjust the posture of the steel beam. S10: Longitudinal temporary locking. When the steel beam of the closing section is lifted to the same level as the erected steel beam, the bridge crane’s longitudinal amplitude change, elevation lifting and lowering, and lateral movement functions are used to adjust the closing opening of the lower chord longitudinal beam of the steel beam on the fixed support side according to the closing construction sequence. After the closing opening is aligned in three directions, the anchor box and steel rod on the lower chord bridge deck are used to perform longitudinal temporary locking. S11: Adjust the closing mouth of the lower chord and longitudinal beam of the steel beam, and adjust the elevation and lateral displacement deviation through the bridge crane. After the adjustment is in place, temporarily lock it immediately to release the longitudinal constraint of the movable support; S12: Temporary closing: After the lower chord longitudinal beams at both ends of the closing section are temporarily locked, the lateral adjustment is performed through the closing adjustment anchor box on the upper chord member. After the adjustment is in place, temporary locking is performed to complete the temporary closing; S13: Permanent closure. After the temporary locking of the closing mouth rods is completed, check their flatness and the closing mouth welding gap. After the inspection is completed, weld the lower chord longitudinal beam, upper chord rod and steel box girder in sequence to complete the permanent closure.

2. The method for integrally closing a large-segment box girder composite steel beam according to claim 1, characterized in that: In step S4, the box girder with the closed ring opening and the ring opening of the upper chord of the erected beam section are cut by 25 mm to form an oblique ring opening.

3. The method for integrally closing a large-segment box truss composite steel beam according to claim 2, characterized in that: After the matching and cutting is completed, the center distance between the closing section steel beam and the erected steel beam is greater than 25mm, and when the top plate of the closing section box beam passes the bottom plate of the erected section box beam, the distance is 50mm.

4. The method for integrally closing a large-segment box truss composite steel beam according to claim 1, characterized in that: In step S8, an inclinometer is installed on the surface of the steel beam in the closing section before lifting. The changes in the posture of the steel beam are transmitted to the command center display screen in real time through wireless transmission, and warning values ​​and limit values ​​are set. During the lifting process, the lateral inclination of the steel beam does not exceed 0.75%, and the longitudinal inclination does not exceed 2%.

5. The method for integrally closing a large-segment box truss composite steel beam according to claim 1, characterized in that: In steps S10-S12, the adjustment accuracy of the bridge crane is 10 mm.

6. The method for integrally closing a large-segment box truss composite steel beam according to claim 1, characterized in that: In step S12, the diagonal web members on both sides of the steel beam of the closing section are removed in advance and then installed on site after the steel beam is closed.

7. The method for integrally closing a large-segment box truss composite steel beam according to claim 1, characterized in that: In step S13, when closing, the ring mouth is matched first with the lower chord bar, then with the upper chord bar, and finally with the box girder ring mouth.

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