Manufacturing method of large-span fish-bellied steel box girder

Abstract

The invention provides a manufacturing method of a large-span fish-belly type steel box girder, and relates to the field of steel box girder manufacturing, the large-span fish-belly type steel box girder is longitudinally segmented, the length of each section of bottom plate is shortened, and bending forming of the bottom plates is facilitated; a bottom plate welding jig frame is erected, and when reinforcing ribs are welded, a bottom plate is deformed into a target radian from an initial radian according to the welding seam shrinkage principle; a three-dimensional model is established, the error between the actual coordinate and the theoretical coordinate of the positioning point is judged, and the position of each structure is adjusted, so that the actual structure size of the steel box girder is more accurate. The manufacturing method has the effect of improving the manufacturing quality and efficiency of the fish-bellied steel box girder.

Description

Technical Field

[0001] The present application relates to the technical field of steel box girder manufacturing, and in particular to a method for manufacturing a large-span fish-belly steel box girder. Background Art

[0002] The long-span fish-belly steel box girder is a common structural form in modern bridge engineering and is widely used in the construction of long-span bridges. Its unique fish-belly design, that is, the cross-sectional shape with a high middle and low ends, can effectively improve the bending resistance and overall rigidity of the beam, reduce the deadweight of the bridge, and enhance the bearing capacity of the bridge under long span conditions. This type of steel box girder is usually composed of a top plate, a bottom plate, a web plate and an internal reinforcement structure, and is assembled through modern welding technology. It has the characteristics of light structure, high strength and good wind resistance, and is widely used in highway bridges, railway bridges and cross-sea bridges.

[0003] In the related art, the method for manufacturing large-span fish-belly steel box girders usually adopts a combination of factory prefabrication and on-site assembly. Specifically, the various components of the steel box girder, such as the top plate, bottom plate and web plate, are usually processed and preliminarily assembled in the factory, and then transported to the construction site for welding and overall installation. During the manufacturing process, especially in the bottom plate part, an arc design is often used to meet the structural requirements of the fish-belly type. Traditional processing technology usually relies on rolling or bending equipment to make the bottom plate, and during the assembly process, the various parts are connected into a whole through welding and other processes.

[0004] With regard to the above-mentioned related technologies, the existing manufacturing methods have some defects, especially when manufacturing the base plate, the accuracy of the curvature is difficult to control. Due to the high processing requirements of the base plate, the existing process is prone to distortion of the base plate during the bending process, causing the geometric shape of the base plate to deviate from the design requirements. This not only increases the workload of adjustment during subsequent assembly, but may also have an adverse effect on the overall stiffness and strength of the steel box girder, reduce the construction quality and service life of the bridge, and affect the overall efficiency and safety of the project. Summary of the invention

[0005] In order to improve the problems of low quality and efficiency in the production process of fish-belly steel box girders, the present application provides a method for producing a large-span fish-belly steel box girder.

[0006] The present application provides a method for manufacturing a large-span fish-bellied steel box girder using the following technical solution: A method for manufacturing a large-span fish-bellied steel box girder, the large-span fish-bellied steel box girder comprising a box girder structure and cantilever structures arranged on both sides of the box girder structure, the steel box girder structure and the cantilever structure are both provided with multiple sections in the longitudinal direction, the box girder structure comprises a top plate located at the top, a bottom plate located at the bottom, and a web plate supported between the top plate and the bottom plate and arranged in the longitudinal direction, the web plates are provided with multiple web plates at intervals in the transverse direction, a box girder chamber is formed between the top plate, the bottom plate and two adjacent web plates, a transverse partition is provided on the inner wall of the chamber, a plurality of reinforcing ribs are welded at intervals in the transverse direction on the sides of the top plate and the bottom plate close to each other, and the reinforcing ribs are arranged in the longitudinal direction; The preparation method comprises the following steps: S1. Conduct three-dimensional modeling of the long-span fish-belly steel box girder and determine the theoretical coordinates of each positioning point; S2, overlapping the inverted tire frame composed of the top plate, the web plate and part of the transverse partition, and splicing multiple sections of the inverted tire frame along the longitudinal direction; S3, measuring the actual coordinates of each positioning point of the inverted tire frame, comparing the actual coordinates of each positioning point with the theoretical coordinates, fine-tuning the error positioning point, and after the adjustment is completed, welding and fixing the multi-section inverted tire frame; S4, calculating the initial curvature of the bottom plate before welding the reinforcing ribs according to the target curvature of the bottom plate and the deformation curvature of the bottom plate when the reinforcing ribs are welded, and arranging the bottom plate welding frame according to the initial curvature of the bottom plate; S5, placing the initial bottom plate on the bottom plate welding frame, pressing the initial bottom plate to an initial curvature, welding the reinforcing ribs, and gradually deforming and bending the bottom plate to a target curvature during the welding process; S6, installing the remaining transverse partitions on the bottom plate, and installing the bottom plate on the inverted tire frame; S7, repeat S4-S7 until the multiple sections of the bottom plate are installed longitudinally; S8. Turn over the box girder structure so that the top plate faces upward and the bottom plate faces downward to complete the production.

[0007] Furthermore, in step S5, after the initial bottom plate is pushed up to the initial curvature, before the reinforcing ribs are welded, the lowest point of the bottom plate is limited by setting a limiter.

[0008] Furthermore, in step S5, when welding the reinforcing ribs, the welding is performed symmetrically from both sides of the bottom plate to the middle.

[0009] Furthermore, the diaphragm comprises a top diaphragm, an abdominal diaphragm and a bottom diaphragm which are connected end to end in sequence, the top diaphragm is connected to the top plate, the bottom diaphragm is connected to the bottom plate, and the abdominal diaphragm is connected to the belly plate.

[0010] Furthermore, the top transverse partition and the bottom transverse partition are both provided with a plurality of avoidance grooves for avoiding the reinforcing ribs.

[0011] Furthermore, in step S2, the overlapping of the inverted tire frame includes the following steps: a. Place the top plate with the inner side facing upwards, draw the installation reference lines of the reinforcing ribs and the web on the top plate according to the drawings, and draw the installation reference lines of the diaphragms on the web; b. Weld the reinforcing ribs on the inner side of the top plate according to the installation reference line of the reinforcing ribs; c. Weld the web plate on the inner side of the top plate according to the installation reference line of the web plate; d. According to the installation reference line of the partition, weld part of the partition on the web and the top plate, wherein the part of the partition includes a top partition and two belly partitions located on both sides of the top partition.

[0012] Furthermore, the positioning point in steps S1 and S3 is the intersection point of the web and the diaphragm.

[0013] Furthermore, the eaves structure includes an eaves panel, an eaves partition and an eaves decorative panel. The eaves panel is arranged coplanar with the top plate. The eaves decorative panel, the eaves partition and the web form an eaves cavity. The eaves partition is arranged in the eaves cavity and is used to support the eaves panel and the eaves decorative panel.

[0014] Furthermore, in step S2, after the multiple sections of the inverted frame are spliced, the cantilevered eaves structure is installed on both sides of the inverted frame. Alternatively, in step S8, after the box beam structure is turned over, the cantilevered eaves structure is installed on both sides of the inverted frame.

[0015] In summary, the present application includes at least one of the following beneficial technical effects: 1. The long-span fish-belly steel box girder of the present invention is longitudinally segmented, so that the length of the bottom plate of each section is shortened, which is convenient for the bending and forming of the bottom plate, solves the problem that the arch of the bridge and the curvature of the bottom plate itself are easily deformed, and makes the overall curvature of the bottom plate smooth and not easy to deform; 2. The present invention sets up a bottom plate welding frame and utilizes the principle of weld shrinkage to deform the bottom plate from an initial curvature to a target curvature when welding the reinforcing ribs. This can solve the problem that the bottom plate deformation during the welding of the reinforcing ribs requires later adjustment, and can calculate the bottom plate deformation caused by the welding of the reinforcing ribs during the deformation of the bottom plate to the target curvature, so that the bottom plate is formed into the target curvature after the reinforcing ribs are welded, thereby improving the quality and efficiency of bottom plate forming. 3. The present invention can indirectly locate the installation position of the bottom plate by measuring the cross positioning points of the web and the transverse partition, thereby solving the problem that the measuring points of the curved bottom plate are difficult to calibrate, and further improving the quality and efficiency of the fish-belly steel box girder manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a schematic diagram of the overall structure of a large-span fish-belly steel box girder according to an embodiment of the present application.

[0018] Figure 2 It is a schematic diagram of the structure of the transverse partition of an embodiment of the present application.

[0019] Figure 3 It is a schematic diagram of the inverted tire frame structure of an embodiment of the present application.

[0020] Figure 4 It is a schematic diagram of a bottom plate welding frame according to an embodiment of the present application.

[0021] Figure 5 It is a schematic diagram of installing the base plate onto the inverted tire frame according to an embodiment of the present application.

[0022] Figure 6 It is a schematic diagram of the flip-chip installation of the base plate completed in the embodiment of the present application.

[0023] Figure numerals: 1. Top plate; 2. Bottom plate; 3. Web plate; 4. Partition; 41. Top partition; 42. Bottom partition; 43. Web partition; 5. Eaves structure; 51. Eaves panel; 52. Eaves decorative panel; 53. Eaves partition; 6. Reinforcing rib; 61. U-shaped rib; 62. T-shaped rib; 63. I-shaped rib; 7. Bottom plate welding frame. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The present application embodiment discloses a method for manufacturing a large-span fish-bellied steel box girder. First, the specific structure of the large-span fish-bellied steel box girder is introduced. Please refer to Figure 1-6, a large-span fish-belly steel box girder structure and an overhanging eaves structure 5 arranged on both sides of the box girder structure, the steel box girder structure and the overhanging eaves structure 5 are both provided with multiple sections in the longitudinal direction, the box girder structure includes a top plate 1 located at the top, a bottom plate 2 located at the bottom, and a web plate 3 supported between the top plate 1 and the bottom plate 2 and arranged in the longitudinal direction, and the web plate 3 is provided with multiple lateral intervals; a box girder chamber is formed between the top plate 1, the bottom plate 2 and two adjacent web plates 3. A transverse partition 4 is provided on the inner wall of the box girder chamber, and the transverse partition 4 is welded and fixed to each inner wall of the box girder chamber. Specifically, the transverse partition 4 is frame-shaped, and the side walls of the transverse partition 4 are respectively welded and fixed to the top plate 1, the bottom plate 2 and the web plates 3 on both sides, so as to support the box girder chamber; a plurality of reinforcing ribs 6 are welded at intervals in the transverse direction on the side of the top plate 1 and the bottom plate 2 close to each other, and the reinforcing ribs 6 are arranged in the longitudinal direction.

[0026] The diaphragm 4 includes a top diaphragm 41, a bottom diaphragm 42 and a belly diaphragm 43, wherein the length of the top diaphragm 41 is the same as the distance between the two webs 3, the curvature of the bottom diaphragm 42 is the same as the curvature of the corresponding bottom plate 2, and the belly diaphragm 43 is the same as the height of the corresponding web 3. By connecting the top diaphragm 41, the belly diaphragm 43 and the bottom diaphragm 42 end to end to form a frame shape, the box beam cavity can be supported and the structural strength of the steel box beam can be improved. In order to make way for the reinforcing ribs 6 on the top plate 1 and the bottom plate 2, a plurality of avoidance grooves are provided on the top diaphragm 41 and the bottom diaphragm 42 to facilitate the installation of the diaphragm 4.

[0027] The eaves structure 5 includes an eaves panel 51, an eaves cross partition 53 and an eaves decorative panel 52. The eaves panel 51 is arranged coplanar with the top plate 1. The eaves decorative panel 52 is an arc-shaped plate whose curvature matches the bottom plate 2. An eaves cavity is formed between the eaves panel 51, the eaves decorative panel 52 and the web 3 close to the eaves structure 5. The eaves cross partition 53 is an integrally formed triangular plate, which is supported inside the eaves cavity to improve the stability of the eaves structure 5.

[0028] In order to further ensure the stability of the steel box girder structure, different shapes of reinforcing ribs 6 are set at different positions. Specifically, since the top plate 1 is the direct compression part of the steel box girder, in order to reduce the local buckling of the top plate 1 when it is compressed, the reinforcing ribs 6 on the inner side of the top plate 1 are set as U-shaped ribs 61. The U-shaped ribs 61 form a larger section inertia torque and section modulus by enclosing, thereby improving the bending stiffness of the top plate 1 and increasing the stability and overall bearing capacity of the top plate 1. Since the bottom plate 2 is an arc-shaped plate, in order to improve the overall stiffness of the bottom plate 2 and enable the reinforcing ribs 6 to adapt to the arc-shaped bottom plate 2 contour, the reinforcing ribs 6 on the bottom plate 2 are set as T-shaped ribs 62. The vertical plate part of the T-shaped ribs 62 can effectively resist the bending deformation of the bottom plate 2 and improve the bending resistance of the bottom plate 2. The horizontal part of the T-shaped ribs 62 can increase the cross-sectional area of ​​the reinforcing ribs 6, improve the overall stiffness of the steel box girder, and make the arc-shaped bottom plate 2 have higher bending and shear resistance. Since the cantilever structure 5 is located at the two wings of the steel box girder and because the cantilever panel 51 is required to have a high ability to resist bidirectional bending, the reinforcing ribs 6 on the cantilever panel 51 are set as I-shaped ribs 63. Due to the cross-sectional characteristics of the upper and lower flange plates and the middle vertical plate of the I-shaped rib 63, the I-shaped rib 63 has a larger cross-sectional moment of inertia and can therefore provide higher bending and torsional stiffness to adapt to the cantilever portion with higher torsional requirements.

[0029] The method for manufacturing a large-span fish-belly steel box girder comprises the following steps: S1. Conduct three-dimensional modeling of the long-span fish-belly steel box girder and determine the theoretical coordinates of each positioning point; S2, overlapping the inverted tire frame composed of the top plate 1, the web 3 and part of the transverse partition 4, and splicing multiple sections of the inverted tire frame along the longitudinal direction; S3, measuring the actual coordinates of each positioning point of the inverted tire frame, comparing the actual coordinates of each positioning point with the theoretical coordinates, fine-tuning the error positioning point, and after the adjustment is completed, welding and fixing the multi-section inverted tire frame; S4, calculating the initial curvature of the bottom plate 2 before welding the reinforcing rib 6 according to the target curvature of the bottom plate 2 and the deformation curvature of the bottom plate 2 when the reinforcing rib 6 is welded, and arranging the welding frame of the bottom plate 2 according to the initial curvature of the bottom plate 2; S5, placing the initial bottom plate 2 on the bottom plate 2 welding frame, pressing the initial bottom plate 2 to an initial curvature, welding the reinforcing ribs 6, and gradually deforming and bending the bottom plate 2 to a target curvature during the welding process; S6, installing the remaining part of the transverse partition 4 on the bottom plate 2, and installing the bottom plate 2 on the inverted tire frame; S7, repeat S4-S7 until the multi-segment bottom plate 2 is installed longitudinally; S8. Turn over the box beam structure so that the top plate 1 faces upward and the bottom plate 2 faces downward, and the production is completed.

[0030] In step S1, a drawing software such as AutoCAD, Sketchup or Solidworks is used to perform three-dimensional modeling on the long-span fish-belly steel box girder, and the theoretical coordinate value of each positioning point is determined according to the data coordinates of the three-dimensional model.

[0031] Preferably, the positioning point is the intersection of the web 3 and the cross-spacer 4, which is a joint of the steel box girder structure, and is convenient for accurate positioning, and can effectively reduce the measurement value error.

[0032] Preferably, in the process of overlapping the inverted tire frame, the rectangular top plate 1 is placed flat on the bottom with the inner side of the top plate 1 facing upward, and the installation reference line of the U-shaped rib 61 and the web 3 is drawn on the inner side of the top plate 1 according to the data of the three-dimensional model, and the installation reference line of the cross partition 4 is drawn on the web 3. Specifically, the installation reference line is drawn by using tools such as a steel ruler, an ink line, a spirit level, a tape measure, and a laser locator. Then, according to the installation and special lines, the U-shaped rib 61 and the web 3 are spot-welded and fixed on the inner side of the top plate 1 in turn, and then part of the cross partition 4 is spot-welded and fixed on the web 3 to ensure the accuracy of the position of the web 3, the U-shaped rib 61, and the cross partition 4 relative to the top plate 1.

[0033] Preferably, among the partial partitions 4 spot-welded and fixed on the web 3, the partial partitions 4 include the top plate 1 partition and the web 3 partition. Before fixing the partial partitions 4, the top plate 1 partition and the web 3 partitions on both sides are welded and fixed so that the top plate 1 partition and the web 3 partition form a U-shaped whole, and then the whole is spot-welded and fixed to the web 3, and is also spot-welded and fixed to the inner side of the top plate 1, thereby ensuring the accuracy of the position of the partition 4 and facilitating operation.

[0034] In step S3, the actual coordinates of each positioning point are measured by a total station and compared with the theoretical coordinates. For specific comparison methods, please refer to the following table:

[0035] In the table, the X-axis is the longitudinal coordinate of the positioning point, the Y-axis is the transverse coordinate of the positioning point, and the Z-axis is the height coordinate of the positioning point.

[0036] According to the data in the table above, there is a deviation between the actual coordinates of the B positioning point and the theoretical coordinates. After analysis, it is caused by the installation deviation of the cross partition 4. The cross partition 4 at this location needs to be offset by 5mm along the X axis and lowered by 1mm along the Z axis. Each positioning point with an error is adjusted in sequence. After the adjustment is completed, the point is re-measured to confirm that it is correct, and then the top plate 1, the web 3 and the cross partition 4 are fully welded and fixed.

[0037] Preferably, in steps S4 and S5, the bottom plate 2 welding frame is an arc-shaped top frame with a low center and high sides. The arc-shaped top surface of the bottom plate 2 welding frame is obtained by subtracting the deformation arc of the bottom plate 2 when the reinforcing rib 6 is welded from the target arc of the bottom plate 2. The initial bottom plate 2 is a rectangular plate. The initial bottom plate 2 is pressed from above to fit the top surface of the bottom plate 2 welding frame by a jack or a hydraulic cylinder, so that the top plate 1 can be pressed to the initial arc. Before welding the reinforcing rib 6 on the bottom plate 2, first draw the installation reference line of the T-shaped rib 62 on the bottom plate 2 according to the three-dimensional model, and then weld the T-shaped rib 62 to the bottom plate 2 in sequence according to the installation reference line.

[0038] Preferably, before welding the T-shaped rib 62 to the base plate 2, in order to reduce the possibility of welding errors caused by the displacement of the base plate 2 during welding, a limiter is provided on the welding frame of the base plate 2. In this embodiment, the limiter is a clamp, and the two jaws of the clamp slide up and down. The base plate 2 is located between the two jaws, and the base plate 2 is clamped and fixed by the relative movement of the jaws. As an alternative embodiment, the limiter can also be an inverted L-shaped plate, which is fixedly connected to the welding frame of the base plate 2 and abuts against the lowest point of the base plate 2, thereby limiting the lowest point of the base plate 2, so that the middle of the base plate 2 is fixed and the two sides are free to deform.

[0039] Preferably, in order to make the deformation of the bottom plate 2 more uniform when installing the T-shaped ribs 62, the T-shaped ribs 62 are welded in sequence from both sides of the bottom plate 2 to the middle, and during the welding process, the T-shaped ribs 62 on both sides are welded symmetrically, so that the bottom plate 2 gradually bends from both sides to the middle when welding the T-shaped ribs 62, making the welding deformation of the bottom plate 2 more uniform, thereby further improving the molding quality of the bottom plate 2.

[0040] In step S6, the remaining part of the diaphragm 4 is the bottom diaphragm 42. When welding the bottom diaphragm 42, the installation reference line of the bottom diaphragm 42 is also drawn on the bottom plate 2 according to the three-dimensional model, and the bottom diaphragm 42 is welded and fixed on the bottom plate 2 according to the installation reference line to ensure the position accuracy of the bottom diaphragm 42. When the bottom plate 2 is installed on the inverted tire frame, the bottom plate 2 diaphragm on the bottom plate 2 is aligned with the belly diaphragm 43 on the inverted tire frame and welded and fixed, and then the bottom plate 2 is welded and fixed with the belly plate 3 to complete the production of the unit box beam structure. Multiple bottom plates 2 are welded in sequence along the longitudinal direction to complete the production of the overall box beam structure.

[0041] In this embodiment, after splicing multiple sections of the inverted frame, the eaves structure 5 is installed on both sides of the inverted frame. Specifically, the eaves panel 51 is welded and fixed coplanarly with the top plate 1, and the installation reference lines of the eaves diaphragm 53 and the I-shaped rib 63 are drawn on the eaves panel 51. The I-shaped rib 63 and the eaves diaphragm 53 are welded and fixed according to the installation reference lines, and then the eaves decorative plate 52 is welded and fixed, and the production of the unit eaves structure 5 is completed. Due to the inverted installation of this method, the eaves panel 51 and the top plate 1 are placed horizontally at the bottom, which is convenient for positioning and installation of each structure.

[0042] Since the cantilevered eaves structure 5 on both wings will increase the overall weight of the fish-belly steel box girder, making it more difficult to turn over the box girder structure, as an alternative embodiment, the cantilevered eaves structure 5 can be installed after the box girder structure is turned over, thereby reducing the difficulty of turning over the box girder structure.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for manufacturing a large-span fish-belly steel box girder, characterized in that: The large-span fish-bellied steel box girder comprises a box girder structure and cantilever structures arranged on both sides of the box girder structure, the steel box girder structure and the cantilever structure are both provided with multiple sections in the longitudinal direction, the box girder structure comprises a top plate located at the top, a bottom plate located at the bottom, and a web plate supported between the top plate and the bottom plate and arranged in the longitudinal direction, a plurality of web plates are arranged in the transverse direction, a box girder chamber is formed between the top plate, the bottom plate and two adjacent web plates, a transverse partition is provided on the inner wall of the chamber, a plurality of reinforcing ribs are welded in the transverse direction at intervals on the sides of the top plate and the bottom plate close to each other, and the reinforcing ribs are arranged in the longitudinal direction; The preparation method comprises the following steps: S1. Conduct three-dimensional modeling of the long-span fish-belly steel box girder and determine the theoretical coordinates of each positioning point; S2, overlapping the inverted tire frame composed of the top plate, the web plate and part of the transverse partition, and splicing multiple sections of the inverted tire frame along the longitudinal direction; S3, measuring the actual coordinates of each positioning point of the inverted tire frame, comparing the actual coordinates of each positioning point with the theoretical coordinates, fine-tuning the error positioning point, and after the adjustment is completed, welding and fixing the multi-section inverted tire frame; S4, calculating the initial curvature of the bottom plate before welding the reinforcing ribs according to the target curvature of the bottom plate and the deformation curvature of the bottom plate when the reinforcing ribs are welded, and arranging the bottom plate welding frame according to the initial curvature of the bottom plate; S5, placing the initial bottom plate on the bottom plate welding frame, pressing the initial bottom plate to an initial curvature, welding the reinforcing ribs, and gradually deforming and bending the bottom plate to a target curvature during the welding process; S6, installing the remaining transverse partitions on the bottom plate, and installing the bottom plate on the inverted tire frame; S7, repeat S4-S7 until the multiple sections of the bottom plate are installed longitudinally; S8. Turn over the box girder structure so that the top plate faces upward and the bottom plate faces downward to complete the production.

2. The method for manufacturing a large-span fish-bellied steel box girder according to claim 1, characterized in that: In step S5, after the initial bottom plate is pushed up to the initial curvature, before the reinforcing ribs are welded, the lowest point of the bottom plate is limited by setting a limiter.

3. The method for manufacturing a large-span fish-bellied steel box girder according to claim 2, characterized in that: In step S5, when welding the reinforcing ribs, the welding is performed symmetrically from both sides of the bottom plate to the middle.

4. The method for manufacturing a large-span fish-bellied steel box girder according to claim 1, characterized in that: The diaphragm comprises a top diaphragm, an abdominal diaphragm and a bottom diaphragm which are connected end to end in sequence. The top diaphragm is connected to the top plate, the bottom diaphragm is connected to the bottom plate, and the abdominal diaphragm is connected to the belly plate.

5. The method for manufacturing a large-span fish-bellied steel box girder according to claim 4, characterized in that: The top transverse partition and the bottom transverse partition are both provided with a plurality of avoidance grooves for avoiding the reinforcing ribs.

6. The method for manufacturing a large-span fish-bellied steel box girder according to claim 5, characterized in that: In step S2, the overlapping of the inverted tire frame includes the following steps: a. Place the top plate with the inner side facing upwards, draw the installation reference lines of the reinforcing ribs and the web on the top plate according to the drawings, and draw the installation reference lines of the diaphragms on the web; b. Weld the reinforcing ribs on the inner side of the top plate according to the installation reference line of the reinforcing ribs; c. Weld the web plate on the inner side of the top plate according to the installation reference line of the web plate; d. According to the installation reference line of the partition, weld part of the partition on the web and the top plate, wherein the part of the partition includes a top partition and two belly partitions located on both sides of the top partition.

7. The method for manufacturing a large-span fish-bellied steel box girder according to claim 6, characterized in that: The positioning point in steps S1 and S3 is the intersection point of the web and the diaphragm.

8. The method for manufacturing a large-span fish-bellied steel box girder according to claim 1, characterized in that: The eaves structure includes an eaves panel, an eaves partition and an eaves decorative panel. The eaves panel is arranged coplanar with the top plate. The eaves decorative panel, the eaves partition and the web form an eaves cavity. The eaves partition is arranged in the eaves cavity and is used to support the eaves panel and the eaves decorative panel.

9. The method for manufacturing a large-span fish-bellied steel box girder according to claim 8, characterized in that: In step S2, after a plurality of sections of the inverted frame are spliced, an overhanging eave structure is installed on both sides of the inverted frame.

10. The method for manufacturing a large-span fish-bellied steel box girder according to claim 8, characterized in that: In step S8, after the box beam structure is turned over, the cantilevered eaves structure is installed on both sides of the inverted frame.

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