Steel box girder welding method based on modular segmented prefabrication

Abstract

The invention discloses a steel box girder welding method based on modular segmented prefabrication. The steel box girder welding method comprises the following steps that S1, an upper segment primary product of a girder segment unit is obtained; s2, an upper segment of the beam segment unit is manufactured; s3, the upper section of the beam section unit is temporarily reinforced through a first connecting structure; s4, obtaining a primary product of the lower section of the beam section unit; s5, manufacturing a lower section of the beam section unit; s6, the second connecting structure is installed on the lower section of the beam section unit; s7, the upper section of the beam section unit is hoisted to the lower section of the beam section unit, and then the first steel component is connected to the first connecting structure and the second connecting structure; and S8, obtaining a beam section unit. The large-span steel box girder is divided into multiple girder section units to be modularly manufactured, then the multiple girder section units are mutually spliced, a large jig frame is not needed for supporting, and the welding quality of the steel box girder can be improved.

Description

Technical Field

[0001] This invention belongs to the field of steel box girder manufacturing technology, specifically relating to a welding method for steel box girders based on modular segmented prefabrication. Background Technology

[0002] A steel box girder is a box-section beam structure made of welded steel plates, and it is widely used in long-span bridges, elevated roads, building roofs, and special steel structure projects.

[0003] Steel box girders typically consist of a top plate, bottom plate, web, and diaphragms, forming a hollow structure with high torsional stiffness. They have the following advantages: (1) Steel box girders can withstand large bending moments and torques, making them suitable for long-span bridges; (2) Compared to concrete beams, steel box girders are lighter, which can reduce the load on the substructure and lower the foundation cost; (3) Through anti-corrosion coating, internal dehumidification, and other measures, their service life can be extended.

[0004] Traditional steel box girder manufacturing often adopts the overall assembly and welding process, which has the following defects: (1) Overall welding requires large jig support, the working space is narrow, resulting in poor weld accessibility and easy blind zone weld quality defects; (2) When welding as a whole, the overall span is large, which can easily cause irreversible deformation such as beam segment twisting and warping. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned technical problems existing in the prior art and to provide a modular segmented prefabrication method for welding steel box girders. This method involves modularly manufacturing large-span steel box girders into multiple segment units, and then splicing these segments together. This eliminates the need for large support frames and improves the welding quality of the steel box girders.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A modular, segmented prefabrication method for welding steel box girders, the steel box girder comprising beam segment units, each beam segment unit comprising an upper segment and a lower segment welded together, the upper segment comprising a top plate, a first web, and a first diaphragm, and the lower segment comprising a bottom plate, a second web, and a second diaphragm; characterized by the following steps:

[0008] S1. Support the top plate of the beam segment unit on the ground, then weld the first transverse diaphragm to the top plate of the beam segment unit, and then weld the first web plate to the first transverse diaphragm to obtain the initial product of the upper segment of the beam segment unit.

[0009] S2. Rotate the initial product of the upper segment of the beam unit by 180°, then support the first transverse diaphragm on the ground, and then weld and fix the first web plate and the top plate of the beam unit to obtain the upper segment of the beam unit.

[0010] S3. Temporary reinforcement is carried out on the upper segment of a pair of beam segments using a connecting structure;

[0011] S4. Support the second web plate and the second transverse diaphragm on the ground, and weld the second web plate and the second transverse diaphragm to fix them. Then weld the bottom plate of the beam segment unit and the second web plate to fix them. Weld to obtain the initial product of the lower segment of the beam segment unit.

[0012] S5. Rotate the initial product of the lower segment of the beam unit by 180°, then support the bottom plate of the beam unit on the ground, and then weld and fix the bottom plate of the beam unit and the transverse diaphragm to obtain the lower segment of the beam unit.

[0013] S6. Install the second connecting structure onto the lower segment of the beam segment unit;

[0014] S7. Lift the upper segment of the beam unit onto the lower segment of the beam unit. At this time, web plate one is supported on web plate two, and diaphragm one is supported on diaphragm two. Then connect steel component one to connecting structure one and connecting structure two.

[0015] S8. Weld and fix web plate one and web plate two, and weld and fix diaphragm one and diaphragm two at the same time. Then remove steel component one, and then remove connecting structure one and connecting structure two to obtain beam segment unit.

[0016] Furthermore, in step S3, the connecting structure includes an H-beam, a clamping structure, and a fixing plate. The temporary reinforcement steps are as follows:

[0017] (1) Place multiple H-beams on the top plate of the beam segment unit, with two adjacent H-beams in contact. Then fix the clamping structure on the first transverse diaphragm. The clamping structure provides support for the H-beams. Then use a fixing plate to fix and connect two adjacent H-beams.

[0018] (2) The steel plate is fixedly connected between the clamping structure and the fixing plate.

[0019] Furthermore, during the process of fixing two adjacent H-beams, a U-beam is embedded in the H-beam, with the U-beam positioned at the connection point of the two adjacent H-beams. Then, square steel is welded onto the fixing plate, and the square steel is embedded into the U-beam. Bolt 1 is then inserted into the through hole 1 of the H-beam, the through hole 2 of the U-beam, and the through hole 3 of the square steel. Nut 1 is then screwed into bolt 1 and tightened.

[0020] Furthermore, the clamping structure includes two symmetrically arranged clamping plates. The clamping plates are clamped onto the first transverse partition. Then, a threaded rod is inserted into the first mounting hole of the clamping plate. Nuts are screwed into both ends of the threaded rod and tightened.

[0021] The clamping plate is welded with side plates, and the fixing plate is equipped with connecting columns. The first connecting hole of the steel plate is set on the connecting column, and the second connecting hole of the steel plate and the third connecting hole of the side plate are aligned. Then, the second bolt is installed between the second connecting hole and the third connecting hole, and the third nut is screwed into the second bolt and tightened.

[0022] Furthermore, the second connection structure includes a connector, which is stamped according to the curvature of the bottom plate of the beam segment unit, so that the connector forms an installation part, a support part, and a connection part, with the connection part located between the installation part and the support part.

[0023] When installing the second connection structure, support the support part on the bottom plate of the beam segment unit, then insert the second threaded rod into the second mounting hole of the connection part, and then screw the fourth nut into both ends of the second threaded rod and tighten the fourth nut.

[0024] Before connecting steel component one, steel component one is stamped to form a connecting end. Then steel component one is cut to form groove one. When connecting steel component one, steel component one is placed between clamping plate and connector. Bolt three is installed between the upper connecting end and the mounting part two of clamping plate, and between the lower connecting end and mounting part one. Nut five is screwed into bolt three and tightened. At this time, groove one is located on one side of the connection between diaphragm one and diaphragm two.

[0025] Furthermore, a reinforcing plate is welded to the surface of steel component one, and the reinforcing plate is provided with groove two, which is provided correspondingly to groove one, and the shape of groove two is the same as that of groove one.

[0026] Furthermore, after step S7 is completed, a steel component 2 is welded between web plate 1 and web plate 2. The steel component 2 is provided with a groove 3, which is located on one side of the connection between web plate 1 and web plate 2. After step S8 is completed, the steel component 2 is cut off from web plate 1 and web plate 2.

[0027] The present invention, by adopting the above-described technical solution, has the following beneficial effects:

[0028] 1. The beam segment units of the present invention can be prefabricated in the factory and then spliced ​​on the construction site to improve on-site construction efficiency.

[0029] 2. In the modular beam segment unit fabrication of this invention, the upper segment and the lower segment of the beam segment unit are prefabricated independently to avoid cross-interference, ensure that the weld is accessible in all positions, and improve the welding quality.

[0030] 3. The present invention can suppress deformation: (1) After segmented welding, the segments are flipped 180° and then joined together, using gravity to offset part of the residual welding stress and reduce overall deformation; (2) The temporary reinforcement system composed of connecting structure one, connecting structure two and steel component one provides rigid constraints during the joining stage, suppressing misalignment and shrinkage deformation.

[0031] 4. This invention reverses both the upper segment and the lower segment of the beam segment unit:

[0032] Reverse construction of the upper segment of the beam unit: The top plate of the beam unit is supported on the ground, facing downwards, as the support reference plane. Then, the first transverse diaphragm and the first web are welded to form an inverted preliminary upper segment of the beam unit. Then, it is rotated 180° so that the top plate of the beam unit faces upwards, and the first web is welded and fixed to the top plate of the beam unit to facilitate subsequent assembly with the lower segment of the beam unit.

[0033] Because the bottom plate of the beam segment unit has a certain degree of curvature, it cannot be used as a support reference surface. Therefore, it is necessary to reverse-engineer the lower segment of the beam segment unit. Specifically, the second web plate and the second diaphragm are supported on the ground and welded together. Then, the bottom plate of the beam segment unit and the second web plate are welded together for preliminary shaping, resulting in a preliminary lower segment of the beam segment unit. Then, the segment is rotated 180° so that the bottom plate faces downwards, and the bottom plate and the second diaphragm are welded together to facilitate subsequent assembly with the upper segment of the beam segment unit.

[0034] In the reverse engineering process of the upper and lower segments of the beam unit of the present invention, the welding process is either flat welding or vertical welding, without the need for overhead welding, which reduces worker fatigue, reduces welding blind spots, and improves weld formation quality. Attached Figure Description

[0035] The present invention will be further described below with reference to the accompanying drawings:

[0036] Figure 1 This is a structural schematic diagram of the present invention during the fabrication of the initial product of the upper segment of the beam segment unit;

[0037] Figure 2 This is a schematic diagram of the upper segment structure of the beam segment unit obtained by the present invention;

[0038] Figure 3 This is a structural schematic diagram of the present invention when multiple H-beams are placed on the top plate of a beam segment unit;

[0039] Figure 4 This is a schematic diagram of the H-beam structure in this invention;

[0040] Figure 5 This is a schematic diagram of the present invention when the clamping structure is fixed to the web plate.

[0041] Figure 6 This is a schematic diagram of the clamping structure in this invention;

[0042] Figure 7 This is a schematic diagram of the clamping plate in this invention;

[0043] Figure 8 This is a schematic diagram of the structure of the present invention when two adjacent H-beams are fixedly connected by a fixing plate;

[0044] Figure 9 This is an exploded view of the connection between the U-shaped steel and the fixing plate in this invention;

[0045] Figure 10 This is a schematic diagram of the connection between the U-shaped steel and the fixing plate in this invention;

[0046] Figure 11 This is a schematic diagram of the present invention when the steel plate is fixedly connected between the clamping structure and the fixing plate;

[0047] Figure 12 This is a schematic diagram of the steel plate structure in this invention;

[0048] Figure 13 This is a structural schematic diagram of the present invention during the fabrication of the initial product of the lower segment of a beam segment unit;

[0049] Figure 14 This is a schematic diagram of the lower segment structure of the beam segment unit obtained by the present invention;

[0050] Figure 15 This is a schematic diagram of the present invention where the second connecting structure is installed at the lower segment of the beam segment unit;

[0051] Figure 16 This is a schematic diagram of the second connection structure in this invention;

[0052] Figure 17 This is a schematic diagram of the structure of the present invention, showing the upper segment of a beam unit being hoisted onto the lower segment of a beam unit;

[0053] Figure 18 This is a schematic diagram of the present invention where a steel component is connected to a connecting structure 1 and a connecting structure 2;

[0054] Figure 19 This is a schematic diagram of the structure of the present invention when a steel component 2 is welded between web 1 and web 2;

[0055] Figure 20 This is a structural schematic diagram of steel component one in this invention;

[0056] Figure 21 This is a schematic diagram of the structure of steel component two in this invention;

[0057] Figure 22 This is a structural schematic diagram of the beam segment unit in this invention.

[0058] In the figure, 11-top plate of beam segment unit; 12-web plate one; 13-diaphragm plate one;

[0059] 21-Beam segment unit bottom plate; 22-Web plate two; 23-Diaphragm plate two;

[0060] 31-H-beam; 311-Flange plate; 312-H-beam web; 313-Steel channel; 314-Through hole one; 32-Clamping structure; 321-Clamping plate; 322-Threaded rod one; 323-Nut two; 324-Mounting hole one; 325-Side plate; 326-Connecting hole three; 327-Mounting part two; 328-Mounting hole three; 33-Fixing plate; 331-Square steel; 332-Square steel channel; 333-Connecting column; 334-Through hole three; 335-Bolt one; 3 36-Nut 1; 34-U-shaped steel; 341-Through hole 2; 35-Steel plate; 351-Connecting hole 2; 352-Connecting hole 1; 36-Connecting structure 2; 361-Connector; 3611-Mounting part 1; 3612-Connecting part; 3613-Supporting part; 362-Threaded rod 2; 363-Nut 4; 37-Steel component 1; 371-Groove 1; 372-Reinforcing plate; 373-Groove 2; 374-Connecting end; 38-Steel component 2; 381-Groove 3. Detailed Implementation

[0061] This invention modularly manufactures large-span steel box girders into multiple segment units. These segments are prefabricated in a factory and then transported to the site for assembly, improving on-site construction efficiency. The span of each segment is smaller than the overall steel box girder span, facilitating segmented transportation. The length of each segment is controlled between 10-30m, the lifting capacity of each segment is controlled to a single segment weight ≤100t, and the width limit during transportation is ≤5.5m.

[0062] Beam segment unit such as Figure 22 As shown, the beam segment unit includes upper and lower segments distributed vertically. The upper segment of the beam segment unit includes a top plate 11, a web 12, and a transverse diaphragm 13. The lower segment of the beam segment unit includes a bottom plate 21, a second web 22, and a second transverse diaphragm 23.

[0063] like Figures 1 to 22 As shown, this invention provides a modular, segmented prefabrication method for welding steel box girders.

[0064] Example 1,

[0065] A modular, segmented prefabrication-based steel box girder welding method includes the following steps:

[0066] I. Reconstruction of the upper segment and lower segment of the beam segment unit:

[0067] 1. Reconstruction of upper segments of beam units:

[0068] (1) Support the top plate 11 of the beam segment unit on the ground, with its orientation downwards, as the support reference plane. Then weld the transverse diaphragm 13 to the top plate 11 of the beam segment unit, and then weld the web plate 12 to the transverse diaphragm 13, thus obtaining the initial product of the upper segment of the beam segment unit, such as... Figure 1 As shown.

[0069] (2) Rotate the initial product of the upper segment of the beam unit by 180°, then support the transverse diaphragm 13 on the ground, and then weld and fix the web 12 and the top plate 11 of the beam unit to obtain the upper segment of the beam unit, as shown. Figure 2 As shown.

[0070] 2. Reconstruction of the lower segment of the beam unit:

[0071] Because the bottom plate 21 of the beam segment unit has a certain degree of curvature, it cannot be used as a support reference surface. Therefore, it is necessary to reverse-engineer the lower segment of the beam segment unit, specifically as follows:

[0072] (1) Support the second web plate 22 and the second diaphragm 23 on the ground, and weld the second web plate 22 and the second diaphragm 23 to fix them. Then weld the bottom plate 21 of the beam segment unit and the second web plate 22 to fix them. Perform preliminary shaping and weld to obtain the preliminary product of the lower segment of the beam segment unit, such as Figure 13 As shown.

[0073] (2) Rotate the initial lower segment of the beam unit 180°, and then support the bottom plate 21 of the beam unit on the ground. This can be done by fixing vertical short columns on the ground to support the bottom plate 21, or by placing sandbags on the ground to support the bottom plate 21. Then weld and fix the bottom plate 21 of the beam unit to the transverse diaphragm 23 to obtain the lower segment of the beam unit. Figure 14 As shown.

[0074] In the reverse engineering process of the upper and lower segments of the beam unit of the present invention, the welding process is either flat welding or vertical welding, without the need for overhead welding, which reduces worker fatigue, reduces welding blind spots, and improves weld formation quality.

[0075] II. Establish a stabilization and reinforcement system between the upper segment and the lower segment of the beam segment unit:

[0076] After the upper segment of the beam unit is reconstructed, a connecting structure is used to temporarily reinforce the upper segment. After the lower segment of the beam unit is reconstructed, connecting structure 2 (36) is installed on the lower segment. Then, the upper segment of the beam unit is hoisted onto the lower segment, with web 12 supported on web 22 and diaphragm 13 supported on diaphragm 23. After segmental welding, the segments are rotated 180° and then joined together, using gravity to offset some of the residual welding stress and reduce overall deformation. Steel component 37 is then connected to connecting structure 1 and connecting structure 2 (36). The temporary reinforcement system formed by connecting structure 1, connecting structure 2 (36), and steel component 37 provides rigid constraints during the joining stage, suppressing misalignment and shrinkage deformation.

[0077] 3. Weld the upper segment and lower segment of the beam unit together vertically:

[0078] Weld and fix web plate 12 and web plate 22, and weld and fix diaphragm 13 and diaphragm 23. Then remove steel component 1 37, and then remove connecting structure 1 and connecting structure 2 36 to obtain beam segment unit.

[0079] Example 2,

[0080] Based on the above embodiment one, the present invention needs to consider avoiding deformation of the upper and lower segments of the beam unit during hoisting and welding, and at the same time facilitate the quick dismantling of connection structure one, connection structure two 36 and steel component one 37. The present invention designs another embodiment, specifically designing the temporary reinforcement system.

[0081] Connection structure one includes an H-beam 31, a clamping structure 32, and a fixing plate 33. The clamping structure 32 includes two symmetrically arranged clamping plates 321, each with a mounting hole 324 and a side plate 325 welded to it. The fixing plate 33 has two connecting posts 333. Connection structure two 36 includes two connectors 361, which are stamped according to the curvature of the beam segment unit bottom plate 21, forming a mounting part 3611, a support part 3613, and a connecting part 3612. The connecting part 3612 is located between the mounting part 3611 and the support part 3613.

[0082] The temporary reinforcement steps are as follows:

[0083] (1) Place multiple H-beams 31 on the top plate 11 of the beam segment unit, with adjacent H-beams 31 in close contact, such as Figure 3 As shown. The H-beam 31 is the prior art, which includes a flange plate 311 and an H-beam web plate 312. The H-beam web plate 312 is fixed between the upper and lower flange plates 311, and the flange plate 311 and the H-beam web plate 312 form a steel channel 313.

[0084] Clamp the clamping plate 321 onto the transverse partition 13, then insert the threaded rod 322 into the mounting hole 324 of the clamping plate 321, and then screw the nuts 323 into both ends of the threaded rod 322 and tighten them. Figure 5 As shown, the clamping structure 32 is fixed on the transverse diaphragm 13, and the clamping structure 32 provides support for the H-beam 31.

[0085] A U-shaped steel 34 is embedded in the steel channel 313 of the H-beam 31, with the U-shaped steel 34 positioned at the connection point of two adjacent H-beams 31. A square steel 331 is then welded onto the fixing plate 33, and the square steel 331 is embedded into the U-shaped steel 34. Bolts 335 are then inserted into the through holes 314 of the flange plate 311, 341 of the U-shaped steel 34, and 334 of the square steel 331. Nuts 336 are then screwed into the bolts 335 and tightened. Nuts 336 are positioned in the square steel channel 332 of the square steel 331. Figure 8 As shown. In this invention, two adjacent H-beams 31 are fixedly connected by U-shaped steel 34 and square steel 331 on the fixing plate 33.

[0086] This invention uses H-beams 31 in close contact to form a rigid support frame, which improves the bending stiffness of the top plate 11 of the beam segment unit and prevents the top plate 11 of the beam segment unit from twisting when the upper segment of the beam segment unit is hoisted. This invention embeds U-beams 34 at the connection of the H-beams 31 and welds them to the fixing plate 33 via square steel 331 to form a rigid node, avoiding relative displacement between the H-beams 31. Furthermore, the locking design of bolts penetrating the H-beams 31, U-beams 34, and square steel 331 ensures a firm and detachable connection.

[0087] (2) Based on the distance between the fixing plate 33 and the clamping structure 32, steel plates 35 of different lengths are cut. The first connection hole 352 of the steel plate 35 is placed on the connecting post 333; the first connection hole 352 is an oblong hole. Then, the second connection hole 351 of the steel plate 35 and the third connection hole 326 of the side plate 325 are aligned. Then, bolt 2 is inserted between the second connection hole 351 and the third connection hole 326, and nut 3 is screwed into bolt 2 and tightened. Figure 11 As shown. In this invention, the steel plate 35 is fixedly connected between the clamping structure 32 and the fixing plate 33, so that all the transverse diaphragms 13 are connected together and subjected to force on the H-beam 31, forming a stable structure and preventing the transverse diaphragms 13 from twisting when the upper segment of the beam unit is hoisted.

[0088] (3) Install the second connecting structure 36. The two connecting parts 361 are fixed to the second transverse diaphragm 23. At this time, the support part 3613 is supported on the bottom plate 21 of the beam segment unit, and the connecting part 3612 is tightly attached to the second transverse diaphragm 23. Then, insert the threaded rod 362 into the second mounting hole of the connecting part 3612, and then screw nuts 363 into both ends of the threaded rod 362, and tighten the nuts 363 as follows. Figure 15 As shown. Based on the curvature of the beam segment unit base plate 21, the installation part 3611, support part 3613, and connecting part 3612 are designed to ensure complete contact between the support surface and the beam segment unit base plate 21, avoiding localized stress concentration. The locking method of the threaded rod 362 and nut 363 provides uniform clamping force, preventing slippage of the connecting structure 36 during closure, and facilitating subsequent disassembly of the connecting structure 36.

[0089] (4) Before connecting steel component 37, steel component 37 is stamped to form connecting end 374, and then steel component 37 is cut to form groove 371. A reinforcing plate 372 is welded to the surface of steel component 37. The reinforcing plate 372 has a second groove 373, which corresponds to groove 371. The shape of groove 373 is the same as that of groove 371. The reinforcing plate 372 increases the strength of steel component 37. Grooves 371 and 373 appropriately increase the space at the welding point of diaphragm 13 and diaphragm 23, and diaphragm 13 and diaphragm 23 are appropriately welded as a whole.

[0090] Connect steel component 37, placing it between clamping plate 321 and connector 361. Then, install bolt 3 between the upper connecting end 374 and mounting hole 328 of mounting part 2 327, and between the lower connecting end 374 and mounting part 1 3611. Screw nut 5 into bolt 3 and tighten it. At this point, groove 371 is located on one side of the connection between diaphragm 13 and diaphragm 23. Figure 18 As shown. The connecting end 374 is stamped and fixed to the mounting part 327 of the clamping plate 321 and the mounting part 3611 of the connector 361 by bolts, realizing rapid alignment of the upper and lower segments. The upper and lower segments of the beam unit form a stable system, improving the overall load-bearing capacity. At the same time, the misalignment between the upper and lower segments of the beam unit is ≤1mm, meeting the welding requirements of the upper and lower segments of the beam unit and improving the welding quality. Moreover, the entire temporary reinforcement system provides external rigid constraint during the welding of the diaphragm, suppressing the shrinkage or warping of the diaphragm caused by heat input.

[0091] Example 3,

[0092] To prevent partial misalignment of web plate 12 and web plate 22 during welding, this invention, based on the solution of Embodiment 2, designs another embodiment. After establishing a stabilizing reinforcement system between the upper and lower segments of the beam segment unit, a steel component 2 38 is welded between web plate 12 and web plate 22. Steel component 2 38 is provided with a groove 381, located on one side of the connection between web plate 12 and web plate 22. Figure 19 As shown. Next, the upper and lower segments of the beam segment unit are welded together, and then steel member 238 is cut off from web 12 and web 22. The groove 381 of steel member 238 is located on one side of the connection between web 12 and web 22, acting as a physical limit during closure, forcibly aligning the edges of the two webs, with misalignment controlled within ±0.5mm. Furthermore, steel member 238 provides additional local rigid constraint during web welding, suppressing web shrinkage or warping caused by heat input.

[0093] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A welding method for steel box girders based on modular segmented prefabrication, the steel box girder comprising beam segment units, each beam segment unit comprising an upper segment and a lower segment welded together, the upper segment comprising a top plate, a first web, and a first diaphragm, the lower segment comprising a bottom plate, a second web, and a second diaphragm; characterized in that, Specifically, the steps include the following: S1. Support the top plate of the beam segment unit on the ground, then weld the first transverse diaphragm to the top plate of the beam segment unit, and then weld the first web plate to the first transverse diaphragm to obtain the initial product of the upper segment of the beam segment unit. S2. Rotate the initial product of the upper segment of the beam unit by 180°, then support the first transverse diaphragm on the ground, and then weld and fix the first web plate and the top plate of the beam unit to obtain the upper segment of the beam unit. S3. Temporary reinforcement is carried out on the upper segment of a pair of beam segments using a connecting structure; S4. Support the second web plate and the second transverse diaphragm on the ground, and weld the second web plate and the second transverse diaphragm to fix them. Then weld the bottom plate of the beam segment unit and the second web plate to fix them. Weld to obtain the initial product of the lower segment of the beam segment unit. S5. Rotate the initial product of the lower segment of the beam unit by 180°, then support the bottom plate of the beam unit on the ground, and then weld and fix the bottom plate of the beam unit and the transverse diaphragm to obtain the lower segment of the beam unit. S6. Install the second connecting structure onto the lower segment of the beam segment unit; S7. Lift the upper segment of the beam unit onto the lower segment of the beam unit. At this time, web plate one is supported on web plate two, and diaphragm one is supported on diaphragm two. Then connect steel component one to connecting structure one and connecting structure two. S8. Weld and fix web plate one and web plate two, and weld and fix diaphragm one and diaphragm two at the same time. Then remove steel component one, and then remove connecting structure one and connecting structure two to obtain beam segment unit.

2. The method for welding steel box girders based on modular segmented prefabrication according to claim 1, characterized in that: In step S3, the connecting structure includes an H-beam, a clamping structure, and a fixing plate. The temporary reinforcement steps are as follows: (1) Place multiple H-beams on the top plate of the beam segment unit, with two adjacent H-beams in contact, then fix the clamping structure on the transverse diaphragm, and then use a fixing plate to fix and connect the two adjacent H-beams. (2) The steel plate is fixedly connected between the clamping structure and the fixing plate.

3. The method for welding steel box girders based on modular segmented prefabrication according to claim 2, characterized in that: During the process of fixing two adjacent H-beams, a U-beam is embedded in the H-beam, with the U-beam positioned at the connection point of the two adjacent H-beams. Then, square steel is welded onto the fixing plate, and the square steel is embedded into the U-beam. Bolt 1 is then inserted into the through hole 1 of the H-beam, the through hole 2 of the U-beam, and the through hole 3 of the square steel. Nut 1 is then screwed into bolt 1 and tightened.

4. The method for welding steel box girders based on modular segmented prefabrication according to claim 2, characterized in that: The clamping structure includes two symmetrically arranged clamping plates. The clamping plates are clamped on the first transverse partition. Then, a threaded rod is inserted into the first mounting hole of the clamping plate. Nuts are screwed into both ends of the threaded rod and tightened. The clamping plate is welded with a side plate, and the fixing plate is provided with a connecting post. The connecting hole one of the steel plate is set on the connecting post, and then the connecting hole two of the steel plate and the connecting hole three of the side plate are aligned. Then, bolt two is installed between connecting hole two and connecting hole three, and nut three is screwed into bolt two and tightened.

5. The method for welding steel box girders based on modular segmented prefabrication according to claim 4, characterized in that: The second connection structure includes two connectors. The connectors are stamped according to the curvature of the bottom plate of the beam segment unit, so that the connectors form an installation part, a support part, and a connection part. The connection part is located between the installation part and the support part. When installing the second connection structure, support the support part on the bottom plate of the beam segment unit, then insert the second threaded rod into the second mounting hole of the connection part, and then screw the fourth nut into both ends of the second threaded rod and tighten the fourth nut. Before connecting steel component one, steel component one is stamped to form a connecting end. Then steel component one is cut to form groove one. When connecting steel component one, steel component one is placed between clamping plate and connector. Bolt three is installed between the upper connecting end and the mounting part two of clamping plate, and between the lower connecting end and mounting part one. Nut five is screwed into bolt three and tightened. At this time, groove one is located on one side of the connection between diaphragm one and diaphragm two.

6. The method for welding steel box girders based on modular segmented prefabrication according to claim 5, characterized in that: A reinforcing plate is welded to the surface of the steel component one. The reinforcing plate is provided with a second groove, which is provided in correspondence with the first groove. The shape of the second groove is the same as that of the first groove.

7. The method for welding steel box girders based on modular segmented prefabrication according to claim 1, characterized in that: After step S7 is completed, steel component 2 is welded between web 1 and web 2. The steel component 2 is provided with groove 3, which is located on one side of the connection between web 1 and web 2. After step S8 is completed, steel component 2 is cut off from web 1 and web 2.

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