Polygonal steel box girder structure of extra-thick plate in spatial distortion form and welding assembly method of polygonal steel box girder structure

Abstract

The invention relates to a polygonal steel box girder structure of an extra-thick plate in a spatial distortion form. The polygonal steel box girder structure is characterized by comprising a bottom plate, webs, a top plate and partition plates, the partition plate is arranged in a box body structure defined by the bottom plate, the web plates and the top plate. A detailed welding scheme is designed for the extra-thick plate steel box girder structure in the spatial distortion form; a large number of space hyperboloid structures are subjected to fine lofting, and the bending and twisting and buckling shapes of plate units are accurately controlled; the method comprises the steps of plate feeding, groove cutting, grinding and welding, different assembling and welding modes are adopted for different positions, the tensile strength of a welding area, the yield strength of weld metal, the percentage elongation after fracture, impact resistance and other physical properties of the welded steel box girder structure in the spatial distortion form meet the construction requirements, and the construction quality is ensured; according to the method, the existing equipment basis is combined, the production process flow and the operation method are improved, the cost is effectively saved, the first-pass yield of welding seams is high, and the welding quality of the steel box girder is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of bridge construction, and in particular to a special thick plate polygonal steel box girder structure with a spatial distortion shape and a welding and assembly method thereof. Background Art

[0002] Compared with the traditional rectangular cross-section steel box girder structure, the spatially distorted polygonal steel box girder structure is extremely irregular. A large number of spatial hyperbolic structures make it more difficult to precisely lay out the steel beams and make them difficult to process and manufacture. In addition, the plate units of the spatially distorted steel box girders are all bent, torsionally curved plate units. Their manufacturing process is very different from that of traditional plane plate units, and their manufacturing accuracy directly affects the quality of the steel box girder.

[0003] Due to the special structure of the spatial twisted steel box girder, the dihedral angle between the polygonal steel box girder panels is too small (the minimum angle is 20°), the welding accessibility is low, and the welding quality requirements are high. The polygonal panels are all full-penetration fillet welds. This has great difficulty in controlling deformation for the spatial twisted structure with high dimensional accuracy requirements, and the traditional welding process cannot meet the design requirements. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a high-quality and high-efficiency welding and assembly method for a special thick plate polygonal steel box girder structure with a spatial distortion shape.

[0005] In order to solve the above technical problems, the technical solution of the present invention is: a spatially distorted extra-thick plate polygonal steel box girder structure, the innovation of which is: comprising a bottom plate, a web plate, a top plate and a partition plate; the partition plate is arranged in a box structure surrounded by the bottom plate, the web plate and the top plate; The bottom plate includes a horizontal box bottom plate, an arc bottom plate and an inclined box bottom plate; the arc bottom plate is arranged between the horizontal box bottom plate and the inclined box bottom plate; one end of the arc bottom plate extends obliquely toward the top plate and intersects with the top plate; The web plate includes a horizontal box web plate and an inclined box web plate; the horizontal box web plate is arranged on one side of the horizontal box bottom plate, and the horizontal box web plate and the horizontal box bottom plate are arranged at an obtuse angle; the inclined box web plate is vertically arranged on one side of the inclined box bottom plate; The top plate includes a horizontal box top plate, an arc-shaped top plate and an inclined box top plate; the arc-shaped top plate is welded between the horizontal box top plate and the inclined box top plate; the horizontal box top plate, the horizontal box belly plate and the horizontal box bottom plate surround the three side surfaces of a horizontal box; one end of the arc-shaped top plate is welded to one end of the arc-shaped bottom plate, and a gap is left between the other end of the arc-shaped top plate and the other end of the arc-shaped bottom plate; the inclined box top plate, the inclined box belly plate and the inclined box bottom plate surround the three side surfaces of an inclined box.

[0006] Furthermore, a plurality of stiffening ribs are vertically arranged on the inner wall of the box structure surrounded by the bottom plate, the web plate and the top plate.

[0007] A welding and assembly method for a spatially distorted extra-thick plate polygonal steel box girder structure, the innovation of which is as follows: S1: Steel plate cutting: First, the steel plate is flattened by a plate cutting machine before pretreatment, and the flatness is strictly controlled; the bent and twisted steel plate is automatically unfolded by software, and the CNC flame cutting machine is used to cut the V-shaped groove; then, the steel plate is profiled by a press, and then fire-corrected on the platform, and the profile and fire-correction are coordinated to achieve the designed curvature; S2: Preparation before welding: Grind away the rust, oil stains and pre-coated primer within 20-30mm on both sides of the weld on all plate units; Determine the need for preheating before welding based on the preheating temperature of the steel plate, the welding cold crack test and the welding process assessment test, and the preheating temperature range is 120-150℃; Use flame preheating or electric heating. To ensure that the preheating is in place, if the steel plate can be heated on both sides, it should be preheated from both sides to ensure that it is heated thoroughly; The temperature measurement point should be no less than 75mm away from the edge of the weld. For thick plates, the temperature should be measured from the back of the thick plate; The heating should be uniform and heated thoroughly, and the temperature measurement should be carried out 30 seconds after the heating source leaves the steel plate; If the temperature cannot be measured on the back, the preheating time should be extended; S3: Assembly welding sequence: The polygonal steel box girder panels are welded on the platform using solid carbon dioxide gas shielded welding and submerged arc welding for steel plate butt welds; First, weld the longitudinal stiffening rib welds on the top plate and bottom plate; then connect the longitudinal stiffening rib welds on the web of the steel box beam on a special tire frame; after trimming, use the tire frame to inspect the shape of the plate unit; Place the outer web and top plate on the integral tire frame; assemble the transverse partitions and vertical partitions in sequence, and fix them by positioning welding; Weld the welds between the transverse diaphragm and the outer web; weld the welds between the outer webs; weld the welds between the vertical diaphragm and the outer web, transverse diaphragm; weld the welds between the transverse diaphragm and the bottom plate, top plate; Weld the welds between the transverse diaphragm and the inner web; weld the welds between the vertical diaphragm and the inner web, and weld the welds between the inner webs; Weld the main weld of the box through penetration, and weld the four welds in the same direction: weld the main weld box inside weld; clean the outside of the box, and weld the main weld box outside weld through penetration; In order to ensure the welding quality of extra-thick plates, the butt welds of steel plates and the full penetration fillet welds between wall panels are heat treated at 250~300℃ for 2~3 hours after welding, and then covered with asbestos blankets for insulation and slow cooling. Among them, welds that have passed the appearance inspection are subjected to ultrasonic non-destructive testing 48 hours after welding.

[0008] Furthermore, when assembling the main fillet welds where the panel dihedral angle is between 20° and 30°, a ceramic backing is lined on the groove side, and the inner fillet weld is welded. According to the different assembly gaps, round bar backing with different diameters is used; the backing is removed. If the welding formation meets the requirements, continue welding the groove side weld; if the weld formation does not meet the requirements, gouge the root on the groove side with a carbon electrode and continue welding after grinding.

[0009] Furthermore, since the arch beam connection section is a twisted structure and the main fillet weld is a full penetration fillet weld with a large filling amount, multi-layer and multi-pass welding should be used during welding. The main fillet welds are welded in the same direction, and the welds between the diaphragm and the inner and outer webs are symmetrically welded from the middle to both sides, and flame dressing is coordinated to reduce welding deformation and ensure the dimensional accuracy of the members.

[0010] Furthermore, for the butt weld of steel plates: shielded metal arc welding with carbon dioxide is used for backing welding, with the current of 220 - 260, voltage of 26 - 30, welding speed of 12 - 20 m / h, and heat input of 1.03 - 2.34 KJ / mm; submerged arc automatic welding is used for filling and surfacing, and the process parameters include: welding current of 630 - 690 A, arc voltage of 28 - 34 V, welding speed of 22 - 30 m / h, and heat input of 2.12 - 3.84 KJ / mm; root cleaning treatment is carried out before reverse welding; For the full penetration fillet welds between the top plate, bottom plate and web of the steel box girder: in the flat position, the process parameters of shielded metal arc welding with solid wire and carbon dioxide gas protection are used, including welding current of 240 - 300 A, arc voltage of 28 - 32 V, welding speed of 20 - 40 m / h, and heat input of 0.60 - 1.73 KJ / mm; in the overhead position, flux cored wire carbon dioxide gas shielded welding is used, and the process parameters include welding current of 160 - 200 A, arc voltage of 24 - 28 V, welding speed of 20 - 40 m / h, and heat input of 0.35 - 1.11 KJ / mm; gouge the root and grind it clean before reverse welding; When the dihedral angle between the steel box girder panels is between 20° and 30°, the process parameters of the full penetration fillet weld include: for the back seal welding, the welding current is 200 - 240 A, voltage is 28 - 32 V, welding speed is 20 - 40 m / h, and heat input is 0.50 - 1.38 KJ / mm; for the first pass on the groove side, the welding current is 220 - 240 A, voltage is 30 - 32 V, welding speed is 20 - 40 m / h, and heat input is 0.50 - 1.38 KJ / mm; for the remaining passes on the groove side, the welding current is 240 - 260 A, voltage is 30 - 32 V, welding speed is 15 - 40 m / h, and heat input is 0.65 - 2.00 KJ / mm; multi-layer and multi-pass welding method is used during welding to effectively ensure the weld quality.

[0011] Furthermore, the butt weld of the steel plate adopts a U-shaped groove; compared with the V-shaped groove and the X-shaped groove, the U-shaped groove fills less weld metal, which can reduce welding costs and improve welding efficiency; the fillet radius at the bottom increases the space at the root of the groove, making it easier for the welding wire to extend into the root, ensuring root penetration and improving the overall quality of the weld; The dihedral angle of the steel box girder panel is between 75° and 105°, and an asymmetric K-shaped groove is used; the asymmetric groove can minimize the deformation caused by carbon arc air planing root cleaning; When the dihedral angle of the steel box girder panel is less than 75°, or between 105° and 120°, a single-sided V-shaped groove is used; due to the small space between panels and poor welding accessibility, the single-sided V-shaped groove reduces the amount of welding in the narrow space, which not only ensures the welding quality, but also reduces the exposure time of welders in the smoke environment; When the dihedral angle between the steel box girder panels is between 20° and 30°, a single-sided J-shaped groove is used. Considering that the panels are twisted surfaces and the dihedral angle between the two panels is gradual, they cannot be machined into a J-shaped groove. Therefore, it is decided to first use flame cutting to form a V-shaped groove and then use carbon arc air planing to form a J-shaped groove. Because the panels are twisted surfaces, the dimensional tolerance between the panels cannot be guaranteed during assembly. Therefore, the assembly gap between the panels is 3-8mm, and round rods are used as gaskets.

[0012] The advantages of the present invention are: 1) The present invention designs a detailed welding scheme for the extra-thick plate steel box girder structure with a spatial distortion shape; finely lays out a large number of spatial hyperbolic structures, and accurately controls the bending, twisting and curvature of the plate units; the blanking, bevel cutting, grinding and welding of the plate adopt different assembly welding methods for different positions. The physical properties of the welded space-distorted steel box girder structure after welding, such as the tensile strength of the welding area, the yield strength of the weld metal, the elongation after fracture, and the impact resistance, meet the construction requirements, ensuring the construction quality; the present invention combines the existing equipment foundation, improves the production process and operation method, effectively saves costs, has a high one-time pass rate for welds, and has a significant effect on improving the welding quality of steel box girders. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0014] Figure 1 This is a structural diagram of a spatially distorted extra-thick plate polygonal steel box girder of the present invention.

[0015] Figure 2 This is another angled view of a spatially distorted extra-thick plate polygonal steel box girder structure of the present invention.

[0016] Figure 3The invention discloses a steel plate butt joint cutout form for a method for welding and assembling a spatially distorted extra-thick plate polygonal steel box girder.

[0017] Figure 4 The invention discloses a welding and assembling method for a special thick plate polygonal steel box girder with a spatial twisted shape, wherein the dihedral angle is between 75° and 105°, and the groove form between the polygonal panels of the steel box girder is provided.

[0018] Figure 5 The invention discloses a method for welding and assembling a spatially distorted extra-thick plate polygonal steel box girder, wherein the dihedral angle is less than 75°, or between 105° and 120°, and the groove between the polygonal panels of the steel box girder is in the form of a groove.

[0019] Figure 6 The invention discloses a welding and assembly method for a special thick plate polygonal steel box girder with a spatial distortion shape, wherein the dihedral angle is between 20° and 30°, and the groove form between the polygonal panels of the steel box girder is provided.

[0020] Figure 7 The present invention is a steel plate butt weld sequence diagram of a method for welding and assembling a spatially distorted extra-thick plate polygonal steel box girder.

[0021] Figure 8 The present invention is a sequence diagram of the arrangement of the horizontal penetration fillet welds of a method for welding and assembling a spatially twisted extra-thick plate polygonal steel box girder.

[0022] Fig. 9 The present invention is a horizontal + upward penetration fillet weld arrangement sequence diagram of a spatially twisted extra-thick plate polygonal steel box girder welding and assembly method.

[0023] Fig.10 The invention discloses a welding and assembly method for a special thick plate polygonal steel box girder with a spatial distortion shape, wherein the dihedral angle is 20°-30°, and the arrangement sequence of the welds of the full penetration fillet welds between the face plates of the polygonal steel box girder is provided. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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.

[0026] like Figure 1 Figure 2 The illustrated structure is a spatially distorted extra-thick plate polygonal steel box girder structure, comprising a bottom plate 1, a web plate 2, a top plate 3 and a partition plate 4; the partition plate 4 is arranged in a box structure surrounded by the bottom plate 1, the web plate 2 and the top plate 3.

[0027] The bottom plate 1 includes a horizontal box bottom plate 11, an arc bottom plate 12 and an inclined box bottom plate 13; the arc bottom plate 12 is arranged between the horizontal box bottom plate 11 and the inclined box bottom plate 13; one end of the arc bottom plate 13 extends obliquely toward the top plate 3 and intersects with the top plate 3.

[0028] The web 2 includes a horizontal box web 21 and an inclined box web 22; the horizontal box web 21 is arranged on one side of the horizontal box bottom plate 11, and the horizontal box web 21 and the horizontal box bottom plate 11 are arranged at an obtuse angle; the inclined box web 22 is vertically arranged on one side of the inclined box bottom plate 11.

[0029] The top plate 3 includes a horizontal box top plate 31, an arcuate top plate 32 and an inclined box top plate 33; the arcuate top plate 32 is welded between the horizontal box top plate 31 and the inclined box top plate 33; the horizontal box top plate 31, the horizontal box web 21 and the horizontal box bottom plate 31 surround the three side surfaces of a horizontal box; one end of the arcuate top plate 32 is welded to one end of the arcuate bottom plate 12, and a gap is left between the other end of the arcuate top plate 32 and the other end of the arcuate bottom plate 12; the inclined box top plate 33, the inclined box web 22 and the inclined box bottom plate 13 surround the three side surfaces of an inclined box.

[0030] A plurality of stiffening ribs are vertically arranged on the inner wall of the box structure surrounded by the bottom plate 1, the web plate 2 and the top plate 3.

[0031] like Figures 3 to 10 The following is a welding and assembly method for a spatially distorted extra-thick plate polygonal steel box girder structure. The specific welding and assembly method is as follows: S1: Steel plate cutting: First, the steel plate is flattened by a plate cutting machine before pretreatment, and the flatness is strictly controlled; the bent and twisted steel plate is automatically unfolded by software, and the CNC flame cutting machine is used to cut the V-shaped groove; then, the steel plate is profiled by a press, and then fire-corrected on the platform, and the profile and fire-correction are coordinated to achieve the designed curvature; S2: Preparation before welding: Grind away the rust, oil stains and pre-coated primer within 20-30mm on both sides of the weld on all plate units; Determine the need for preheating before welding based on the preheating temperature of the steel plate, the welding cold crack test and the welding process assessment test, and the preheating temperature range is 120-150℃; Use flame preheating or electric heating. To ensure that the preheating is in place, if the steel plate can be heated on both sides, it should be preheated from both sides to ensure that it is heated thoroughly; The temperature measurement point should be no less than 75mm away from the edge of the weld. For thick plates, the temperature should be measured from the back of the thick plate; The heating should be uniform and heated thoroughly, and the temperature measurement should be carried out 30 seconds after the heating source leaves the steel plate; If the temperature cannot be measured on the back, the preheating time should be extended; S3: Assembly welding sequence: The polygonal steel box girder panels are welded on the platform using solid carbon dioxide gas shielded welding and submerged arc welding for steel plate butt welds; First, weld the longitudinal stiffening rib welds on the top plate and bottom plate; then connect the longitudinal stiffening rib welds on the web of the steel box beam on a special tire frame; after trimming, use the tire frame to inspect the shape of the plate unit; Place the outer web and top plate on the integral tire frame; assemble the transverse partitions and vertical partitions in sequence, and fix them by positioning welding; Weld the welds between the transverse diaphragm and the outer web; weld the welds between the outer webs; weld the welds between the vertical diaphragm and the outer web, transverse diaphragm; weld the welds between the transverse diaphragm and the bottom plate, top plate; Weld the welds between the transverse diaphragm and the inner web; weld the welds between the vertical diaphragm and the inner web, and weld the welds between the inner webs; Weld the main weld of the box through penetration, and weld the four welds in the same direction: weld the main weld box inside weld; clean the outside of the box, and weld the main weld box outside weld through penetration; In order to ensure the welding quality of extra-thick plates, the butt welds of steel plates and the full penetration fillet welds between wall panels are heat treated at 250~300℃ for 2~3 hours after welding, and then covered with asbestos blankets for insulation and slow cooling. Among them, welds that have passed the appearance inspection are subjected to ultrasonic non-destructive testing 48 hours after welding.

[0032] When assembling the main weld with a panel dihedral angle between 20°-30°, a ceramic liner is lined on the groove side and the inner corner weld is welded. Depending on the assembly gap, round rod liners with different diameters are used; remove the liner, and if the welding formation does not meet the requirements, continue to weld the groove side weld; if the weld formation does not meet the requirements, use a carbon rod air planer to clean the root of the groove side, and continue welding after grinding.

[0033] Since the arch-beam joint section is a twisted structure and the main weld is a full-penetration fillet weld with a large filling volume, multi-layer and multi-pass welding should be used during welding. The main welds should be welded in the same direction, and the welds between the diaphragm and the inner and outer webs should be welded symmetrically from the middle to both sides, and flame trimming should be used to reduce welding deformation and ensure the dimensional accuracy of the rods.

[0034] Steel plate butt weld: CO2 gas shielded welding for base welding, current 220~260, voltage 26~30, welding speed 12~20m / h, heat input 1.03~2.34KJ / mm; submerged arc automatic welding for filling and capping, process parameters include: welding current 630~690A, arc voltage 28~34V, welding speed 22~30m / h, heat input 2.12~3.84KJ / mm; root cleaning before reverse welding; For the penetration fillet welds between the top plate, bottom plate and web of the steel box girder: the horizontal position adopts solid wire carbon dioxide gas shielded welding process parameters including welding current 240-300A, arc voltage 28-32V, welding speed 20-40m / h, heat input 0.60-1.73KJ / mm; the upward position adopts flux-cored wire carbon dioxide gas shielded welding, process parameters including welding current 160-200A, arc voltage 24-28V, welding speed 20-40m / h, heat input 0.35-1.11KJ / mm; the reverse side is cleaned by air planing and polishing before welding; When the dihedral angle between the steel box girder panels is between 20° and 30°, the process parameters of the penetration fillet weld include: the bottom welding current is 200-240A, the voltage is 28-32V, the welding speed is 20-40m / h, and the heat input is 0.50-1.38KJ / mm; the first welding current on the groove side is 220-240A, the voltage is 30-32V, the welding speed is 20-40m / h, and the heat input is 0.50-1.38KJ / mm; the remaining welding currents on the groove side are 240-260A, the voltage is 30-32V, the welding speed is 15-40m / h, and the heat input is 0.65-2.00KJ / mm; multi-layer and multi-pass welding is adopted during welding to effectively ensure the quality of the weld.

[0035] The butt weld of steel plates adopts U-shaped groove; compared with V-shaped groove and X-shaped groove, U-shaped groove fills less weld metal, which can reduce welding cost and improve welding efficiency; the fillet radius at the bottom increases the space at the root of the groove, making it easier for the welding wire to extend into the root, ensuring root penetration and improving the overall quality of the weld; The dihedral angle of the steel box girder panel is between 75° and 105°, and an asymmetric K-shaped groove is used; the asymmetric groove can minimize the deformation caused by carbon arc air planing root cleaning; When the dihedral angle of the steel box girder panel is less than 75°, or between 105° and 120°, a single-sided V-shaped groove is used; due to the small space between panels and poor welding accessibility, the single-sided V-shaped groove reduces the amount of welding in the narrow space, which not only ensures the welding quality, but also reduces the exposure time of welders in the smoke environment; When the dihedral angle between the steel box girder panels is between 20° and 30°, a single-sided J-shaped groove is used. Considering that the panels are twisted surfaces and the dihedral angle between the two panels is gradual, they cannot be machined into a J-shaped groove. Therefore, it is decided to first use flame cutting to form a V-shaped groove and then use carbon arc air planing to form a J-shaped groove. Because the panels are twisted surfaces, the dimensional tolerance between the panels cannot be guaranteed during assembly. Therefore, the assembly gap between the panels is 3-8mm, and round rods are used as gaskets.

[0036] The working principle of the present invention is: Those skilled in the art should understand that the present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements shall fall within the scope of the present invention claimed for protection.

Claims

1. A spatially distorted extra-thick plate polygonal steel box girder structure, characterized in that: It includes a bottom plate, a web plate, a top plate and a partition plate; the partition plate is arranged in a box structure surrounded by the bottom plate, the web plate and the top plate; The bottom plate includes a horizontal box bottom plate, an arc bottom plate and an inclined box bottom plate; the arc bottom plate is arranged between the horizontal box bottom plate and the inclined box bottom plate; one end of the arc bottom plate extends obliquely toward the top plate and intersects with the top plate; The web plate includes a horizontal box web plate and an inclined box web plate; the horizontal box web plate is arranged on one side of the horizontal box bottom plate, and the horizontal box web plate and the horizontal box bottom plate are arranged at an obtuse angle; the inclined box web plate is vertically arranged on one side of the inclined box bottom plate; The top plate includes a horizontal box top plate, an arc-shaped top plate and an inclined box top plate; the arc-shaped top plate is welded between the horizontal box top plate and the inclined box top plate; the horizontal box top plate, the horizontal box belly plate and the horizontal box bottom plate surround the three side surfaces of a horizontal box; one end of the arc-shaped top plate is welded to one end of the arc-shaped bottom plate, and a gap is left between the other end of the arc-shaped top plate and the other end of the arc-shaped bottom plate; the inclined box top plate, the inclined box belly plate and the inclined box bottom plate surround the three side surfaces of an inclined box.

2. The spatially distorted extra-thick plate polygonal steel box girder structure according to claim 1 is characterized by: A plurality of stiffening ribs are vertically arranged on the inner wall of the box structure surrounded by the bottom plate, the web plate and the top plate.

3. A welding and assembly method for a spatially distorted extra-thick plate polygonal steel box girder structure, characterized in that: The specific welding assembly method is as follows: S1: Steel plate cutting: First, the steel plate is flattened by a plate cutting machine before pretreatment, and the flatness is strictly controlled; the bent and twisted steel plate is automatically unfolded by software, and the CNC flame cutting machine is used to cut the V-shaped groove; then, the steel plate is profiled by a press, and then fire-corrected on the platform, and the profile and fire-correction are coordinated to achieve the designed curvature; S2: Preparation before welding: Grind away the rust, oil stains and pre-coated primer within 20-30mm on both sides of the weld on all plate units; Determine the need for preheating before welding based on the preheating temperature of the steel plate, the welding cold crack test and the welding process assessment test, and the preheating temperature range is 120-150℃; Use flame preheating or electric heating. To ensure that the preheating is in place, if the steel plate can be heated on both sides, it should be preheated from both sides to ensure that it is heated thoroughly; The temperature measurement point should be no less than 75mm away from the edge of the weld. For thick plates, the temperature should be measured from the back of the thick plate; The heating should be uniform and heated thoroughly, and the temperature measurement should be carried out 30 seconds after the heating source leaves the steel plate; If the temperature cannot be measured on the back, the preheating time should be extended; S3: Assembly welding sequence: The polygonal steel box girder panels are welded on the platform using solid carbon dioxide gas shielded welding and submerged arc welding for steel plate butt welds; First, weld the longitudinal stiffening rib welds on the top plate and bottom plate; then connect the longitudinal stiffening rib welds on the web of the steel box beam on a special tire frame; after trimming, use the tire frame to inspect the shape of the plate unit; Place the outer web and top plate on the integral tire frame; assemble the transverse partitions and vertical partitions in sequence, and fix them by positioning welding; Weld the welds between the transverse diaphragm and the outer web; weld the welds between the outer webs; weld the welds between the vertical diaphragm and the outer web, transverse diaphragm; weld the welds between the transverse diaphragm and the bottom plate, top plate; Weld the welds between the transverse diaphragm and the inner web; weld the welds between the vertical diaphragm and the inner web, and weld the welds between the inner webs; Weld the main weld of the box through penetration, and weld the four welds in the same direction: weld the main weld box inside weld; clean the outside of the box, and weld the main weld box outside weld through penetration; In order to ensure the welding quality of extra-thick plates, the butt welds of steel plates and the full penetration fillet welds between wall panels are heat treated at 250~300℃ for 2~3 hours after welding, and then covered with asbestos blankets for insulation and slow cooling. Among them, welds that have passed the appearance inspection are subjected to ultrasonic non-destructive testing 48 hours after welding.

4. The welding and assembly method of a spatially distorted extra-thick plate polygonal steel box girder structure according to claim 3 is characterized by: When assembling the main weld with a panel dihedral angle between 20°-30°, a ceramic liner is lined on the groove side and the inner corner weld is welded. Depending on the assembly gap, round rod liners with different diameters are used; remove the liner, and if the welding formation does not meet the requirements, continue to weld the groove side weld; if the weld formation does not meet the requirements, use a carbon rod air planer to clean the root of the groove side, and continue welding after grinding.

5. The welding and assembly method of a spatially distorted extra-thick plate polygonal steel box girder structure according to claim 3 is characterized by: Since the arch-beam joint section is a twisted structure and the main weld is a full-penetration fillet weld with a large filling volume, multi-layer and multi-pass welding should be used during welding. The main welds should be welded in the same direction, and the welds between the diaphragm and the inner and outer webs should be welded symmetrically from the middle to both sides, and flame trimming should be used to reduce welding deformation and ensure the dimensional accuracy of the rods.

6. The welding and assembly method of a spatially distorted extra-thick plate polygonal steel box girder structure according to claim 3 is characterized by: Steel plate butt weld: CO2 gas shielded welding for base welding, current 220~260, voltage 26~30, welding speed 12~20m / h, heat input 1.03~2.34KJ / mm; submerged arc automatic welding for filling and capping, process parameters include: welding current 630~690A, arc voltage 28~34V, welding speed 22~30m / h, heat input 2.12~3.84KJ / mm; root cleaning before reverse welding; For the penetration fillet welds between the top plate, bottom plate and web of the steel box girder: the horizontal position adopts solid wire carbon dioxide gas shielded welding process parameters including welding current 240-300A, arc voltage 28-32V, welding speed 20-40m / h, heat input 0.60-1.73KJ / mm; the upward position adopts flux-cored wire carbon dioxide gas shielded welding, process parameters including welding current 160-200A, arc voltage 24-28V, welding speed 20-40m / h, heat input 0.35-1.11KJ / mm; the reverse side is cleaned by air planing and polishing before welding; When the dihedral angle between the steel box girder panels is between 20° and 30°, the process parameters of the penetration fillet weld include: the bottom welding current is 200-240A, the voltage is 28-32V, the welding speed is 20-40m / h, and the heat input is 0.50-1.38KJ / mm; the first welding current on the groove side is 220-240A, the voltage is 30-32V, the welding speed is 20-40m / h, and the heat input is 0.50-1.38KJ / mm; the remaining welding currents on the groove side are 240-260A, the voltage is 30-32V, the welding speed is 15-40m / h, and the heat input is 0.65-2.00KJ / mm; multi-layer and multi-pass welding is adopted during welding to effectively ensure the quality of the weld.

7. The welding and assembly method of a spatially distorted extra-thick plate polygonal steel box girder structure according to claim 3 is characterized by: The butt weld of steel plates adopts U-shaped groove; compared with V-shaped groove and X-shaped groove, U-shaped groove fills less weld metal, which can reduce welding cost and improve welding efficiency; the fillet radius at the bottom increases the space at the root of the groove, making it easier for the welding wire to extend into the root, ensuring root penetration and improving the overall quality of the weld; The dihedral angle of the steel box girder panel is between 75° and 105°, and an asymmetric K-shaped groove is used; the asymmetric groove can minimize the deformation caused by carbon arc air planing root cleaning; When the dihedral angle of the steel box girder panel is less than 75°, or between 105° and 120°, a single-sided V-shaped groove is used; due to the small space between the panels and poor welding accessibility, the single-sided V-shaped groove reduces the amount of welding in the narrow space, which not only ensures the welding quality, but also reduces the time the welder is exposed to the smoke environment; when the dihedral angle between the steel box girder panels is between 20° and 30°, a single-sided J-shaped groove is used. Considering that the panels are twisted surfaces and the dihedral angle between the two panels is gradual, they cannot be machined into a J-shaped groove. Therefore, it is decided to first use flame cutting to form a V-shaped groove and then use carbon arc air planing to form a J-shaped groove. Because the panels are twisted surfaces, the dimensional tolerance between the panels cannot be guaranteed during assembly. Therefore, the assembly gap between the panels is 3-8mm during assembly, and round rods are used as pads.

Images