A method for manufacturing and constructing a steel box girder

Abstract

This invention discloses a method for manufacturing and constructing a steel box girder. The steel box girder adopts a design with large and small ends, including beam segments A, B1, and B2, which are independently hoisted and assembled sequentially from the large end to the small end. All three are assembled using a reverse assembly method. The manufacturing process of beam segment A includes the following steps: Step A, assembling a jig on an assembly platform according to the bridge alignment and transverse distribution; Step B, assembling the top plate of A on the jig; Step C, assembling a first transverse diaphragm on one side of the top plate of A; Step D, assembling the web plate of A in the middle of the top plate of A; Step E, assembling a second transverse diaphragm on the other side of the top plate of A and performing internal welding of beam segment A; Step F, installing the bottom plate ribs of A into the slots one of the first transverse diaphragm and the slots two of the second transverse diaphragm, and positioning and welding them; Step G, installing the bottom plate of A onto the first and second transverse diaphragms, and performing internal welding of beam segment A; Step H, installing the railing base; Step I, grinding, sandblasting, and painting beam segment A.

Description

Technical Field

[0001] This invention relates to the field of steel box girder technology, and in particular to a method for manufacturing and constructing steel box girders. Background Technology

[0002] Steel box girders are often used in the construction of suspension bridges and cable-stayed bridges due to their light weight and high load-bearing capacity. Pedestrian cable-stayed bridges are a type of bridge for pedestrians. Compared with highway bridges for vehicles, they place greater emphasis on lightweighting, aesthetics, and pedestrian comfort. To meet the lightweight design requirements of pedestrian cable-stayed bridges, traditional concrete structures are no longer the first choice, and steel box girders have become the mainstream option.

[0003] The core of steel box girder fabrication lies in precision control and welding quality. Therefore, improving manufacturing precision and welding quality has become the key to steel box girder fabrication. Summary of the Invention

[0004] One of the objectives of this invention is, at least, to provide a method for manufacturing and constructing steel box girders to overcome the problems existing in the prior art. The method uses a reverse assembly method, which can not only control the lateral assembly accuracy and reduce the construction difficulty, but also significantly reduce the welding difficulty by changing the welding position, thereby improving the manufacturing accuracy and welding quality.

[0005] To achieve the above objectives, the technical solution adopted by the present invention includes the following aspects.

[0006] A method for fabricating and constructing a steel box girder, wherein the steel box girder adopts a design with large and small ends, including beam segments A, B1, and B2, which are independently hoisted and assembled sequentially from the large end to the small end. Beam segments A, B1, and B2 are all assembled using a reverse assembly method. The fabrication of beam segment A includes the following steps: Step A: Assemble the jig on the assembly platform according to the bridge alignment and lateral distribution; Step B: Assemble the top plate A on the jig; Step C: Assemble the first transverse diaphragm on one side of the top plate A; Step D: Assemble web plate A in the middle of top plate A; Step E: Assemble the second transverse diaphragm on the other side of the top plate A, and perform internal welding of beam A; Step F: Install the bottom plate ribs of A into the first slot of the first transverse diaphragm and the second slot of the second transverse diaphragm, and position and weld them. Step G: Install the base plate A on the first transverse diaphragm (13) and the second transverse diaphragm, and perform internal welding of beam A; Step H: Install the railing base; Step I: Grind, sandblast, and paint beam A.

[0007] Preferably, in step B, multiple A-top plate ribs are arranged side by side along the width direction of the A-top plate, and the A-top plate ribs are located on the side of the A-top plate away from the frame (1).

[0008] Preferably, in step C, multiple first transverse partitions are arranged side by side along the length of the top plate A. The first end of the first transverse partition opens to the second end to form a manhole. A slot is provided on the edge of the first transverse partition. The ribs of the top plate A are inserted into the corresponding slots of the first transverse partitions. The first end of the first transverse partition extends 100-120mm beyond the top plate A.

[0009] Preferably, in step D, three A-web plate ribs are arranged side by side on the side of the A-web plate closest to the first transverse diaphragm, and the A-web plate ribs are inserted into the corresponding slots on the first transverse diaphragm; three A-web plate ribs are arranged side by side on both sides of the A-web plate located 9-10m longitudinally at the end of the bridge beam.

[0010] Preferably, in step E, multiple second transverse partitions are arranged side-by-side along the length of the top plate A, with the second transverse partitions corresponding to the positions of the first transverse partitions. A manhole is provided in the middle of the second transverse partition, the first end of the second transverse partition is arc-shaped, and the middle part is arc-shaped. A slot is provided on the edge of the second transverse partition, and the A top plate ribs on the top plate A are inserted into the corresponding slots of the second transverse partitions. The first end of the second transverse partition extends beyond the top plate A. When A web plate ribs are arranged side-by-side on both sides of the web plate A, the A web plate ribs away from the first transverse partition are inserted into the corresponding slots of the second transverse partitions.

[0011] Preferably, in step G, the A base plate is an integrally bent plate, and the A base plate includes a diagonal section, a support section and an arc section arranged in sequence. The arc section has a circular arc in the middle and serves as a side diaphragm of the steel box girder. The A web plate is located at the support section of the A base plate, and the diagonal section of the A base plate extends 100-12mm beyond the first end of the first transverse diaphragm.

[0012] Preferably, in step I, a set of railing bases is installed on the side of top plate A away from the ribs of top plate A. Before installing the railing bases, beam A is placed facing forward.

[0013] Preferably, the beam segment B1 includes a B1 top plate, a B1 web, a third transverse diaphragm, and a B1 bottom plate. When manufacturing the beam segment B1, the length of the first end of the B1 top plate extending beyond the first end of the third transverse diaphragm is adapted to the length of the first end of the first transverse diaphragm extending beyond the top plate A, and the length of the second end of the B1 top plate extending beyond the second end of the third transverse diaphragm is adapted to the thickness of the B1 web. The B1 bottom plate is inclined, and the length of the first end of the third transverse diaphragm extending beyond the B1 bottom plate is adapted to the length of the inclined section of the bottom plate A extending beyond the first end of the first transverse diaphragm. When the beam segment B1 is assembled with the beam segment A, the B1 top plate overlaps the first transverse diaphragm, and the third transverse diaphragm overlaps the inclined section of the bottom plate A.

[0014] Preferably, the beam segment B2 includes a B2 top plate, a transverse connector, a vertical connector, and a B2 bottom plate. The transverse and vertical connectors are made of H-beams. When manufacturing the beam segment B2, a transverse connector is installed at one end of the B2 top plate, and the first end of the transverse connector is welded to the side of the B2 top plate where the B2 top plate ribs are located. A vertical connector is installed on the B2 top plate, and the first end of the vertical connector is welded to the B2 top plate. Multiple vertical connectors are arranged side by side along the width direction of the B2 top plate, and the length of the vertical connectors increases away from the transverse connectors, so that the B2 bottom plate is arranged obliquely after installation. The B2 bottom plate is installed on the vertical connectors, and the second end of the vertical connectors is welded to the B2 bottom plate. One end of the B2 bottom plate is welded to the transverse connectors, and the second end of the transverse connectors is away from the B2 bottom plate. The transverse connectors serve as the other side partition of the steel box girder. Another set of railing bases is installed on the B2 top plate.

[0015] Preferably, the steel box girder further includes a beam segment C, which includes a top plate C, a transverse connector ', a vertical connector ', and a bottom plate C. The transverse connector ' and the vertical connector ' are made of H-beams. When manufacturing the beam segment C, a transverse connector ' is installed at one end of the top plate C, and the first end of the transverse connector ' is welded to the side of the top plate C where the top plate ribs are located. A vertical connector ' is installed on the top plate C, and the first end of the vertical connector ' is welded to the top plate C. Multiple vertical connectors ' are arranged side by side along the width direction of the top plate C, and the length of the vertical connector ' increases away from the transverse connector ', so that the bottom plate C is arranged obliquely after installation. The bottom plate C is installed on the vertical connector ', and the second end of the vertical connector ' is welded to the bottom plate C. One end of the bottom plate C is connected to the transverse connector ', and the second end of the transverse connector ' is away from the bottom plate C. At this time, the transverse connector ' serves as the other side partition of the steel box girder. Another set of railing bases is installed on the top plate C.

[0016] In summary, by adopting the above technical solution, the present invention has at least the following beneficial effects: The construction method uses the reverse assembly method for assembly. The reverse assembly method can control the lateral assembly accuracy and reduce the construction difficulty. The bottom plate of the steel box girder is curved and needs to be rolled by a plate rolling machine. The amount of butt joints is large. The reverse assembly method can not only change the welding position to greatly reduce the welding difficulty, but also greatly improve the manufacturing progress and manufacturing accuracy. Attached Figure Description

[0017] Figure 1 A flowchart illustrating the fabrication and construction process of a steel box girder, which is an exemplary embodiment of the present invention.

[0018] Figure 2 This is a diagram showing the layout of the tire frame.

[0019] Figure 3 This is a layout diagram of the roof slab.

[0020] Figure 4 This is a diagram showing the arrangement of the horizontal and side partitions on one side of the top slab.

[0021] Figure 5 This is a diagram showing the arrangement of the web plates.

[0022] Figure 6 This is a diagram showing the arrangement of the transverse and side partitions on the other side of the top slab.

[0023] Figure 7 This is a layout diagram of the bottom plate ribs.

[0024] Figure 8 This is a layout diagram of the base plate.

[0025] Figure 9 This is a diagram showing the arrangement of the crossbeams.

[0026] Figure 10 This is a layout diagram of the railing base.

[0027] Figure 11 This is a structural schematic diagram of beam A.

[0028] Figure 12 This is a structural schematic diagram of beam segment B1.

[0029] Figure 13 This is a structural schematic diagram of beam segment B2.

[0030] Figure 14 This is a structural schematic diagram of beam C.

[0031] The diagram is labeled as follows: 1-Frame, 2-Top plate, 3-Top plate rib, 4-Diaphragm, 5-Side diaphragm, 6-Body plate, 7-Body plate rib, 8-Bottom plate rib, 9-Bottom plate, 10-Crossbeam, 11-Guardrail base, 12-Top plate A, 13-First diaphragm, 14-Body plate A, 15-Second diaphragm, 16-Bottom plate A, 17-Guardrail base, 18-Top plate B1, 19-Body plate B1, 20-Third diaphragm, 21-Bottom plate B1, 22-Top plate B2, 23-Horizontal connector, 24-Vertical connector, 25-Bottom plate B2, 26-Top plate C, 27-Horizontal connector, 28-Vertical connector, 29-Bottom plate C. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, so that the objectives, technical solutions, and advantages of the present invention will be clearer. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0033] In the description of this invention, it should be understood that if terms such as "upper," "lower," "left," and "right" 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 component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the accompanying drawings are only for illustrative purposes and should not be construed as limiting this patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances. Example

[0034] This embodiment provides a method for fabricating and constructing a steel box girder. The steel box girder is assembled using a reverse assembly method (i.e., assembling it upside down). (Refer to...) Figures 2-10 The fabrication and construction method of steel box girders includes the following steps: Step A0: Assemble the jig 1 on the assembly platform according to the bridge alignment and lateral distribution; Step B0: Assemble the top plate 2 on the jig 1. Multiple top plate ribs 3 are arranged side by side along the width of the top plate 2. The top plate ribs 3 are located on the side of the top plate 2 away from the jig 1. Step C0: Assemble a horizontal partition 4 and a side partition 5 on one side of the top plate 2. The horizontal partition 4 has a groove ' circumferentially opened on its edge. The groove ' at the bottom of the horizontal partition 4 corresponds one-to-one with the top plate rib 3 on the same side of the top plate 2. When assembling the horizontal partition 4, the top plate rib 3 is inserted into the corresponding groove ' at the bottom of the horizontal partition 4. Multiple horizontal partitions 4 are arranged along the entire length of the top plate 2. The side partition 5 is welded to the side of the horizontal partition 4 away from the middle of the top plate 2, so that the horizontal partition 4 on the same side of the top plate 2 is connected through the side partition 5. The bottom of the side partition 5 is also welded to the top plate 2. Step D0: Assemble the web plate 6 in the middle of the top plate 2, so that the web plate 6 is connected to the transverse partition 4 on one side of the top plate 2. Two web plate ribs 7 are arranged side by side on both sides of the web plate 6. The slots on the transverse partition 4 near the middle of the top plate 2 correspond one-to-one with the two web plate ribs 7 on the same side of the web plate 6. When assembling the web plate 6, the two web plate ribs 7 are inserted into the corresponding slots on the transverse partition 4. In step E0, the transverse diaphragm 4 and the side diaphragm 5 are assembled on the other side of the top plate 2, and the steel box girder is welded inside. The transverse diaphragm 4 and the side diaphragm 5 on this side of the top plate 2 are assembled in the same way as the transverse diaphragm 4 and the side diaphragm 5 in step C0. Step F0: Install the bottom plate rib 8 in the slot ´ of the transverse diaphragm 4 and position and weld it. The bottom plate rib 8 is located in the slot ´ on the top of the transverse diaphragm 4 and on the side away from the web plate 6. Each bottom plate rib 8 is inserted into the corresponding slot ´ on the transverse diaphragm 4 on the same side as the top plate 2. Step G0: Install the bottom plate 9 on the transverse diaphragm 4. A manhole (inspection hole) is opened in the middle of the transverse diaphragm 4. Welding is carried out through the manhole into the steel box girder. Step H0: Install the crossbeams 10 and the railing bases ´11. Install both sets of crossbeams 10 and railing bases ´11 at the connection between the two side partitions 5 and the top plate 2, respectively. Weld the two sets of crossbeams 10 to the side of the two side partitions 5 that are far apart from each other, and weld the two sets of railing bases ´11 to the side of the top plate 2 that is far away from the top plate ribs 3. Before installing the railing bases ´11, the steel box girder is placed upright (i.e., the top plate 2 is located above the bottom plate 9). Step I0: Grind, sandblast, and paint the steel box girder.

[0035] In one preferred embodiment, the steel box girder may also adopt a design comprising multiple independently hoisted beam segments with different sizes at each end. The steel box girder includes beam segments A, B1, and B2, which are assembled sequentially from the larger end to the smaller end. Beam segments A, B1, and B2 are manufactured independently. Figure 1 The construction flowchart for beam A is shown. Figure 11 The structural form of beam A is shown, and the steps involved in manufacturing beam A are as follows: Step A: Assemble the jig 1 on the assembly platform according to the bridge alignment and lateral distribution; Step B: Assemble the A top plate 12 on the jig 1; multiple A top plate ribs are arranged side by side along the width of the A top plate 12, and the A top plate ribs are located on the side of the A top plate 12 away from the jig 1. The A top plate 12 is made of steel plate with a thickness of 12mm, and the A top plate ribs are made of steel plate with a side length of 120mm and a thickness of 10mm, and the standard spacing is 350mm. Step C: Assemble a first transverse diaphragm 13 on one side of the top plate 12 of A; the top plate 12 of A is provided with multiple first transverse diaphragms 13 arranged in parallel along its length (standard spacing is 2.5m). The first transverse diaphragms 13 arranged in the middle of the span are made of steel plates with a thickness of 12mm, and the first transverse diaphragms 13 arranged at the abutments and piers of the bridge are made of steel plates with a thickness of 24mm. The first end of the first transverse diaphragm 13 opens to the second end to form a manhole (the first transverse diaphragm 13 located at the end of the bridge beam does not have a manhole). The first end and the second end of the first transverse diaphragm 13 are opposite each other. Except for the first end of the first transverse diaphragm 13, a slot is opened on the edge of the first transverse diaphragm 13 to insert the rib of the top plate 12 of A into the corresponding slot of the first transverse diaphragm 13. The first end of the first transverse diaphragm 13 extends 100-120mm beyond the top plate 12 of A. Step D: Assemble the A web plate 14 in the middle of the A top plate 12; the A web plate 14 is made of steel plate with a thickness of 12mm (the thickness of the A web plate 14 located 9-10m longitudinally at the end of the bridge beam is 24mm), the A web plate 14 has three A web plate ribs arranged side by side on the side near the first transverse diaphragm 13 (the A web plate 14 located 9-10m longitudinally at the end of the bridge beam has three A web plate ribs arranged side by side on both sides), and insert the A web plate ribs into the corresponding slots on the first transverse diaphragm 13, the A web plate ribs are made of steel plate with a side length of 120mm and a thickness of 10mm. Step E: Assemble the second transverse diaphragm 15 on the other side of the top plate 12 of A, and weld it inside the beam segment A; the top plate 12 of A has multiple second transverse diaphragms 15 arranged along its length, and the second transverse diaphragms 15 correspond to the arrangement of the first transverse diaphragms 13. The second transverse diaphragms 15 arranged in the middle of the span are made of steel plates with a thickness of 12mm, and the second transverse diaphragms 15 arranged at the abutments and piers of the bridge are made of steel plates with a thickness of 24mm. A manhole 2 is provided in the middle of the second transverse diaphragm 15 (the second transverse diaphragm 15 located at the end of the bridge beam does not have a manhole 2). The first end of the plate 15 is arc-shaped, and the middle part is arc-shaped. The edge of the second transverse partition 15 is provided with a second slot (when the A web plate rib is arranged only on the side near the first transverse partition 13, the second transverse partition 15 is provided with a second slot except for the second end, and the first end and the second end of the second transverse partition 15 are opposite to each other; when the A web plate rib is arranged on both sides of the A web plate 14, the second transverse partition 15 is provided with a second slot in the circumference). The A top plate rib on the A top plate 12 is inserted into the corresponding second slot of the second transverse partition 15, and the first end of the second transverse partition 15 extends beyond the A top plate 12. Step F: Install the bottom plate ribs of A into the slot one of the first transverse partition 13 and the slot two of the second transverse partition 15, and position and weld them; the bottom plate ribs of A are made of steel plates with a side length of 120mm and a thickness of 10mm, and each bottom plate rib of A is inserted into the slot one of the first transverse partition 13 and the slot two of the second transverse partition 15 that are arranged along the entire length of the top plate of A; Step G: Install the A base plate 16 on the first transverse diaphragm 13 and the second transverse diaphragm 15, and perform internal welding of beam A; the A base plate 16 is made of steel plate with a thickness of 12mm. The A base plate 16 is an integrally bent plate. The A base plate 16 includes a diagonal section, a support section and an arc section arranged in sequence. The arc section has a circular arc in the middle and serves as a side diaphragm of the steel box girder. The A web plate 14 is located at the support section of the A base plate 16. The diagonal section of the A base plate 16 extends 100-12mm beyond the first end of the first transverse diaphragm 13. Step H: Install the railing base 17. Install a set of railing bases 17 on the side of the top plate 12 away from the ribs of the top plate 12. Before installing the railing bases 17, the beam A is placed facing forward (i.e., the top plate 12 is located above the bottom plate 16). Step I: Grind, sandblast, and paint beam A.

[0036] Figure 12 The structural form of beam segment B1 is shown. Beam segment B1 includes a B1 top plate 18, a B1 web 19, a third transverse diaphragm 20, and a B1 bottom plate 21, all made of 12mm thick steel plate (the B1 web 19, located 9-10m longitudinally at the bridge beam end, can be made of 24mm thick steel plate; the third transverse diaphragm 20, located at the abutments and piers, is also made of 24mm thick steel plate). Multiple B1 top plate ribs are arranged side-by-side along the width of the B1 top plate 18, and one B1 web rib is arranged on one side of the B1 web 19. Both the B1 top plate rib and the B1 web rib are made of steel with a side length of 120mm and a thickness of 10mm. The steel plate is used for fabrication. The standard spacing of the ribs of the B1 top plate is 350mm. Multiple third transverse diaphragms 20 are arranged side-by-side along the length of the B1 top plate 18 (standard spacing is 2.5m; after beam B1 and beam A are assembled, the third transverse diaphragms 20 correspond to the positions of the first transverse diaphragms 13). The first end of each third transverse diaphragm 20 opens towards the second end to form a manhole (the third transverse diaphragm 20 located at the bridge beam end does not have a manhole). The first and second ends of the third transverse diaphragm 20 are opposite each other. Except for the first end of the third transverse diaphragm 20, the edge of the third transverse diaphragm 20 has a slot. The beam B1 does not have a railing base 17. The fabrication of beam B1 includes the following steps: Step A1: Assemble the jig 1 on the assembly platform according to the bridge alignment and lateral distribution; Step B1: Assemble the B1 top plate 18 on the jig frame 1. The ribs of the B1 top plate are located on the side of the B1 top plate 18 away from the jig frame 1. Step C1: Assemble the third transverse diaphragm 20 on the top plate 18 of B1; insert the top plate rib of the top plate 18 of B1 into the corresponding slot 3 of the third transverse diaphragm 20. The length of the first end of the top plate 18 extending beyond the first end of the third transverse diaphragm 20 is adapted to the length of the first end of the first transverse diaphragm 13 extending beyond the top plate 12 of A. The length of the second end of the top plate 18 extending beyond the second end of the third transverse diaphragm 20 is adapted to the thickness of the web 19 of B1. The first end and the second end of the top plate 18 of B1 are opposite each other. When beam B1 and beam A are assembled, the top plate 18 of B1 overlaps the first transverse diaphragm 13. Step D1: Assemble the B1 web plate 19 at the second end of the third transverse diaphragm 20 and perform internal welding of the beam plate B1; insert the B1 web plate rib on the B1 web plate 19 into the corresponding slot three on the third transverse diaphragm 20. Step E1: Install the B1 bottom plate ribs into the slots three of the third transverse partition 20 and position and weld them; the B1 bottom plate ribs are made of steel plates with a side length of 120mm and a thickness of 10mm, and each B1 bottom plate rib is inserted into the corresponding slot three of the third transverse partition 20 arranged along the entire length of the B1 top plate 18. Step F1: Install the B1 base plate 21 on the third transverse diaphragm 20 and weld the beam B1 inside. The B1 base plate 21 is set at an angle. The length of the first end of the third transverse diaphragm 20 extending beyond the B1 base plate 21 matches the length of the inclined section of the A base plate 16 extending beyond the first end of the first transverse diaphragm 13. When the beam B1 and the beam A are assembled, the third transverse diaphragm 20 overlaps on the inclined section of the A base plate 16. Step G1: Grind, sandblast, and paint beam segment B1.

[0037] Figure 13 The structural form of beam segment B2 is shown. Beam segment B2 includes a B2 top plate 22, a transverse connector 23, a vertical connector 24, and a B2 bottom plate 25. The B2 top plate 22 and B2 bottom plate 25 are made of steel plates with a thickness of 12mm. The transverse connector 23 and vertical connector 24 are made of H-beams. Multiple B2 top plate ribs are arranged side-by-side along the width direction of the B2 top plate 22. The B2 top plate ribs are made of steel plates with a side length of 120mm and a thickness of 10mm, and the standard spacing between the B2 top plate ribs is 350mm. The manufacturing process of beam segment B2 includes the following steps: Step A2: Assemble the jig 1 on the assembly platform according to the bridge alignment and lateral distribution; Step B2: Assemble the B2 top plate 22 on the jig frame 1. The ribs of the B2 top plate are located on the side of the B2 top plate 22 away from the jig frame 1. Step C2: Install a transverse connector 23 at one end of the top plate 22 of B2, so that the first end of the transverse connector 23 is welded to the side of the top plate 22 of B2 where the top plate ribs of B2 are arranged, and the overall length of the transverse connector 23 is adapted to the overall length of the top plate 22 of B2. Step D2: Install vertical connectors 24 on the top plate 22 of B2. Multiple vertical connectors 24 are arranged side by side along the width direction of the top plate 22 of B2 (after beam B2 and beam B1 are assembled, the arrangement of vertical connectors 24 corresponds to the arrangement of the third transverse diaphragm 20), so that the vertical connectors 24 are staggered with the ribs of the top plate of B2, and the first end of the vertical connector 24 is welded to the top plate 22 of B2. The length of the vertical connector 24 increases in the direction away from the transverse connector 23, so that the bottom plate 25 of B2 is arranged obliquely after installation. Step E2: Install the B2 base plate 25 on the vertical connector 24, so that the B2 top plate 22 and the B2 base plate 25 are located at the two ends of the vertical connector 24 respectively. The B2 base plate 25 is welded to the second end of the vertical connector 24, and one end of the B2 base plate 25 is welded to the transverse connector 23. The second end of the transverse connector 23 is away from the B2 base plate 25, and the first and second ends of the transverse connector 23 are opposite to each other. The transverse connector 23 not only serves as the other side partition of the steel box girder, but also plays a guiding and supporting role for the hanging basket (temporary operating platform). In actual use, the beam segment B2 located at the end of the bridge beam can be sealed with an end partition, so that both ends of the bridge are in a closed state. Step F2: Install the railing base 17. Install another set of railing base 17 on the side of B2 top plate 22 away from the ribs of B2 top plate. Before installing the railing base 17, the beam B2 is placed facing forward (i.e., B2 top plate 22 is located above B2 bottom plate 25). Step G2: Grind, sandblast, and paint beam segment B2.

[0038] In one preferred embodiment, the steel box girder further includes beam segment C, which comprises beam segments A, B1, B2, and C assembled sequentially from the larger end to the smaller end. Figure 14 The structural form of beam segment C is shown. Beam segment C includes a top plate 26, a transverse connector '27, a vertical connector '28, and a bottom plate 29. The top plate 26 and bottom plate 29 are made of 12mm thick steel plates, and the transverse connector '27 and vertical connector '28 are made of H-beams. Multiple top plate ribs are arranged side-by-side along the width of the top plate 26. These top plate ribs are made of 120mm side-by-side steel plates with a thickness of 10mm. The standard spacing of the top plate ribs is 350mm. The fabrication of beam segment C includes the following steps: Step A3: Assemble the jig 1 on the assembly platform according to the bridge alignment and lateral distribution; Step B3: Assemble the C-top plate 26 on the jig 1. The C-top plate rib is located on the side of the C-top plate 26 away from the jig 1. Step C3: Install a transverse connector ´27 at one end of the top plate 26, so that the first end of the transverse connector ´27 is welded to the side of the top plate 26 where the top plate ribs are arranged, and the overall length of the transverse connector ´27 is adapted to the overall length of the top plate 26. Step D3: Install vertical connectors '28' on the top plate 26 of C. Multiple vertical connectors '28' are arranged side by side along the width direction of the top plate 26 of C (after beam C and beam B2 are assembled, the arrangement positions of vertical connectors '28' and vertical connectors 24 correspond), so that the vertical connectors '28' are staggered with the ribs of the top plate of C, and the first end of the vertical connectors '28' is welded to the top plate 26 of C. The length of the vertical connectors '28' increases in the direction away from the transverse connectors '27, so that the bottom plate 29 of C is arranged obliquely after installation. Step E3: Install the C-bottom plate 29 on the vertical connector ´28, so that the C-top plate 26 and the C-bottom plate 29 are located at the two ends of the vertical connector ´28 respectively. The C-bottom plate 29 is welded to the second end of the vertical connector ´28, and one end of the C-bottom plate 29 is welded to the transverse connector ´27. The second end of the transverse connector ´27 is away from the C-bottom plate 29, and the first and second ends of the transverse connector ´27 are opposite each other. At this time, the transverse connector ´27 serves as the other side partition of the steel box girder (the second end of the transverse connector 23 at the widened section can be connected to the B2 bottom plate 25). In actual use, the beam segment C located at the end of the bridge beam can be sealed with an end partition ´, so that both ends of the bridge are in a closed state. Step F3: Install railing base 17. Install another set of railing base 17 on the side of C top plate 26 away from C top plate rib (at this time, railing base 17 is not placed on beam B2). Before installing railing base 17, beam C is placed upright (i.e. C top plate 26 is located above C bottom plate 29). Step G3: Grind, sandblast, and paint beam C.

[0039] In practical applications, bridges can be constructed by combining standard sections and widened sections. The standard section consists of beams A, B1, and B2, assembled sequentially from the larger end to the smaller end. The widened section consists of beams A, B1, B2, and C, assembled sequentially from the larger end to the smaller end. The combination of standard and widened sections to form a bridge not only reduces the bridge's self-weight but also improves its scenic appeal.

[0040] The above description is merely a detailed illustration of specific embodiments of the present invention and is not intended to limit the invention. Various substitutions, modifications, and improvements made by those skilled in the art without departing from the principles and scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating and constructing a steel box girder, characterized in that, The steel box girder adopts a design with large and small ends, including beam segments A, B1, and B2, which are independently hoisted and assembled sequentially from the large end to the small end. Beam segments A, B1, and B2 are all assembled using the reverse assembly method. The fabrication of beam segment A includes the following steps: Step A: Assemble the jig on the assembly platform according to the bridge alignment and lateral distribution (1). Step B: Assemble the top plate (12) A on the frame (1); Step C: Assemble the first transverse partition (13) on one side of the top plate (12) of A; Step D: Assemble web plate A (14) in the middle of top plate A (12). Step E: Assemble the second transverse diaphragm (15) on the other side of the top plate (12) of A, and perform internal welding of beam A; Step F: Install the bottom plate rib of A into the first slot of the first transverse diaphragm (13) and the second slot of the second transverse diaphragm (15), and position and weld them. Step G: Install the A base plate (16) on the first transverse diaphragm (13) and the second transverse diaphragm (15), and perform internal welding of beam A; Step H, install the railing base (17); Step I: Grind, sandblast, and paint beam A.

2. The method for fabricating and constructing a steel box girder according to claim 1, characterized in that, In step B, multiple A-top plate ribs are arranged side by side along the width direction on the A-top plate (12), and the A-top plate ribs are located on the side of the A-top plate (12) away from the frame (1).

3. The method for fabricating and constructing a steel box girder according to claim 2, characterized in that, In step C, multiple first transverse partitions (13) are arranged along the length of the top plate (12). The first end of the first transverse partition (13) opens to the second end to form a manhole. A slot is provided on the edge of the first transverse partition (13). The rib of the top plate on the top plate (12) is inserted into the corresponding slot of the first transverse partition (13). The first end of the first transverse partition (13) extends 100-120mm beyond the top plate (12).

4. The method for fabricating and constructing a steel box girder according to claim 3, characterized in that, In step D, three A-web plate ribs are arranged side by side on the side of the A-web plate (14) close to the first transverse diaphragm (13), and the A-web plate ribs are inserted into the corresponding slots on the first transverse diaphragm (13); three A-web plate ribs are arranged side by side on both sides of the A-web plate (14) located 9-10m longitudinally at the end of the bridge beam.

5. The method for fabricating and constructing a steel box girder according to claim 4, characterized in that, In step E, multiple second transverse partitions (15) are arranged side by side along the length of the top plate (12). The arrangement of the second transverse partitions (15) corresponds to that of the first transverse partition (13). A manhole is opened in the middle of the second transverse partition (15). The first end of the second transverse partition (15) is arc-shaped, and the middle part is arc-shaped. A slot is opened on the edge of the second transverse partition (15). The A top plate rib on the top plate (12) is inserted into the corresponding slot of the second transverse partition (15). The first end of the second transverse partition (15) extends beyond the top plate (12). When the A web plate ribs are arranged side by side on both sides of the A web plate (14), the A web plate ribs away from the first transverse partition (13) are inserted into the corresponding slot of the second transverse partition (15).

6. The method for fabricating and constructing a steel box girder according to claim 5, characterized in that, In step G, the A base plate (16) is an integrally bent plate. The A base plate (16) includes a diagonal section, a support section and an arc section arranged in sequence. The middle part of the arc section is circular arc and the arc section serves as a side diaphragm of the steel box girder. The A web plate (14) is located at the support section of the A base plate (16). The length of the diagonal section of the A base plate (16) extending beyond the first end of the first transverse diaphragm (13) is 100-12mm.

7. The method for fabricating and constructing a steel box girder according to claim 6, characterized in that, In step I, a set of railing bases (17) are installed on the side of top plate A (12) away from the ribs of top plate A. Before installing the railing bases (17), beam A is placed facing forward.

8. The method for fabricating and constructing a steel box girder according to claim 6, characterized in that, The beam segment B1 includes a B1 top plate (18), a B1 web (19), a third transverse diaphragm (20), and a B1 bottom plate (21). When manufacturing the beam segment B1, the length of the first end of the B1 top plate (18) extending beyond the first end of the third transverse diaphragm (20) is matched with the length of the first end of the first transverse diaphragm (13) extending beyond the A top plate (12). The length of the second end of the B1 top plate (18) extending beyond the second end of the third transverse diaphragm (20) is matched with the length of the B1 web. (19) Thickness matching; so that the B1 base plate (21) is set obliquely, the length of the first end of the third diaphragm (20) extending beyond the B1 base plate (21) matches the length of the oblique section of the A base plate (16) extending beyond the first end of the first diaphragm (13), when the beam B1 and the beam A are assembled, so that the B1 top plate (18) overlaps on the first diaphragm (13), and the third diaphragm (20) overlaps on the oblique section of the A base plate (16).

9. The method for fabricating and constructing a steel box girder according to claim 7, characterized in that, The beam segment B2 includes a B2 top plate (22), a transverse connector (23), a vertical connector (24), and a B2 bottom plate (25). The transverse connector (23) and the vertical connector (24) are made of H-beams. When manufacturing the beam segment B2, a transverse connector (23) is installed at one end of the B2 top plate (22), and the first end of the transverse connector (23) is welded to the side of the B2 top plate (22) where the B2 top plate ribs are arranged. A vertical connector (24) is installed on the B2 top plate (22), and the first end of the vertical connector (24) is welded to the B2 top plate (22). Multiple vertical connectors (24) are connected along the B2 top plate. The plates (22) are arranged side by side in the width direction. The length of the vertical connector (24) increases in the direction away from the horizontal connector (23), so that the B2 base plate (25) is arranged diagonally after installation. The B2 base plate (25) is installed on the vertical connector (24), so that the second end of the vertical connector (24) is welded to the B2 base plate (25), and one end of the B2 base plate (25) is welded to the horizontal connector (23). The second end of the horizontal connector (23) is away from the B2 base plate (25). The horizontal connector (23) serves as the other side partition of the steel box girder. Another set of railing bases (17) is installed on the B2 top plate (22).

10. The method for fabricating and constructing a steel box girder according to claim 9, characterized in that, The steel box girder also includes beam segment C, which includes a top plate (26), a transverse connector (27), a vertical connector (28), and a bottom plate (29). The transverse connector (27) and the vertical connector (28) are made of H-beams. When making beam segment C, the transverse connector (27) is installed at one end of the top plate (26), and the first end of the transverse connector (27) is welded to the side of the top plate (26) where the top plate ribs are arranged. The vertical connector (28) is installed on the top plate (26), and the first end of the vertical connector (28) is welded to the top plate (26). Multiple vertical connectors (28) are installed on the top plate (26). The vertical connectors (28) are arranged side by side along the width of the top plate (26), and the length of the vertical connectors (28) is increased in the direction away from the horizontal connectors (27), so that the bottom plate (29) is arranged diagonally after installation. The bottom plate (29) is installed on the vertical connectors (28), and the second end of the vertical connectors (28) is welded to the bottom plate (29). One end of the bottom plate (29) is connected to the horizontal connectors (27), and the second end of the horizontal connectors (27) is away from the bottom plate (29). At this time, the horizontal connectors (27) serve as the other side partition of the steel box beam. Another set of railing bases (17) is installed on the top plate (26).

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