A pre-camber control process for manufacturing large-segment continuous steel trusses

Abstract

The invention relates to a pre-arch control process for manufacturing a large-segment continuous steel truss, which is characterized by: the specific control process is as follows: S1: control of the manufacturing accuracy of a double-integral node chord; S2: precision arrangement of a three-dimensional measurement and control network; S3: control of the assembly accuracy of an integral large segment; by controlling the manufacturing accuracy of the double-integral node chord, the distortion of the rod is controlled by the accuracy of an inner partition, the deflection of the rod is controlled by the accuracy of a vertical plate unit, and the arching accuracy is ensured by the accuracy of the chord hole group; the box opening size, the control rod deformation, the welding shrinkage, the bolt hole accuracy and the quality of the relationship between the hole groups are ensured; by arranging a three-dimensional measurement control network, all measurement points of a tire frame and a segment are directly and accurately monitored through the measurement control network to avoid cumulative measurement errors and improve assembly accuracy; by continuously assembling the entire segment, the entire segment that has been assembled first is used as the mother segment of the subsequent entire segment, thereby improving the assembly accuracy; at the same time, the welding quality is controlled during the assembly process to reduce welding deformation to ensure the size of the rod.

Description

Technical Field

[0001] The invention relates to the technical field of pre-camber control of continuous steel trusses, and in particular to a pre-camber control process for manufacturing large-segment continuous steel trusses. Background Art

[0002] With the rapid development of steel bridges in my country, in order to overcome the difficulties of on-site construction and construction period control at the bridge site, the assembly of large steel bridges has been transferred from the bridge site to the factory. The structure of large-segment continuous steel trusses is complex and the main beam has high rigidity. Especially after the use of integral node technology, once the assembly line deviates, adjustment will be very difficult. In order to control the deflection of steel trusses under constant loads, how to ensure the factory pre-arch of steel trusses and how to control it during the manufacturing and assembly process has become a major difficulty; therefore, a pre-arch control process for the manufacture of large-segment continuous steel trusses is needed to achieve the control of the pre-arch and assembly of steel trusses. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a process for controlling the pre-camber of large-segment continuous steel trusses, which can solve the problem that the pre-camber of general large-segment steel trusses is difficult to ensure and difficult to control during the manufacturing and assembly process.

[0004] In order to solve the above technical problems, the technical solution of the present invention is: a pre-camber control process for manufacturing large-segment continuous steel trusses, and its innovation lies in: the specific control process is as follows:

[0005] S1: Control of the manufacturing accuracy of double integral node chords:

[0006] S1.1: Inner baffle precision control: The inner baffle exists in the box body as a mold for geometric precision control of the box-shaped rod. The inner baffle controls the size of the rod box opening and ensures that the distortion of the near and far ends of the chord is ≤2.0mm; the verticality deviation of the plate edge is ≤0.5mm; the inner baffle is cut by precision cutting, and the inner baffle is assembled by marking and symmetrical welding in the same direction to ensure the straightness of the inner baffle;

[0007] S1.2: Vertical plate unit precision control: The vertical plate unit is composed of an integral node plate, a vertical plate and longitudinal plate ribs; the vertical plate unit is processed in four steps: cutting parts, machining, joining and welding longitudinal ribs; if the width of the vertical plate unit is greater than 4100mm, the steel plate joining should be completed first, and then the cutting should be carried out to ensure the vertical plate unit's external dimensions; the vertical plate unit should be accurately marked after cutting and leveling, including the diagonal rod, the vertical rod axis, the horizontal center line and the machining line of the butt end; the vertical plate unit should be machined and controlled according to the allowable deviation of the rod L>8m and the lateral bending f≤3.0mm, and at the same time, the center distance between the two node plates of the lower chord should be ensured to meet the accuracy requirements within the range of ±2.0mm;

[0008] S1.3: Precision control of chord rod hole groups: The chord rod is provided with connection hole groups at both ends. The bolt holes at both ends of the chord rod are drilled simultaneously by a double-gantry 3D CNC drilling machine. The X-Y-Z three-axis drilling of the double-gantry 3D CNC drilling machine can ensure that the bolt holes on different planes are not misaligned in the longitudinal and transverse directions, and the concentricity deviation of the bolt holes on the vertical plates on both sides is controlled within 1.0mm; the vertical plate polar edge hole distance deviation is ensured to be within 1.0mm;

[0009] S1.4: Arching process: The chord is a straight rod. When assembling, the horizontal line on each part is used as the reference to ensure the straightness of the upper end point of the same rod and the two points on both sides of the installation position of the vertical rod on the rod, a total of six points; the elongation of the upper and lower chords needs to be superimposed during production, and the elongation of the upper and lower chords is achieved by lengthening the length of the chord top plate; the steel trusses within the vertical curve range of the facade are straight instead of curved, and the lower chord system line is used as the baseline for manufacturing and lofting. The intersection of the lower chord system line of each segment is located on the theoretical vertical curve; within the linear longitudinal slope range of the side span, the lower chord system line coincides with the theoretical longitudinal slope, and then the arch control is achieved by the process of staggered holes in the splicing plate;

[0010] S2: Accurate layout of three-dimensional measurement and control network: Construct a three-dimensional measurement and control network including a leveling network, a plane linear control network and a total station measurement base station; use a total station and a theodolite to directly and accurately monitor all measurement points of the tire frame and segments through the measurement and control network to avoid cumulative measurement errors; the assembly camber value is determined according to the drawings, and the camber is adjusted by the elevation of the pad and the adjustment block on the load-bearing pier, and is measured and controlled using a high-precision level and leveling control points;

[0011] S2.1: Control of girder assembly accuracy: The main girder is fully welded internally, and the shrinkage and deformation of welding require strict control of its dimensions, which must ensure the girder height and diagonal difference, as well as the connection between the main girder and the crossbeam, while also avoiding misalignment of the box openings;

[0012] S2.2: Continuous matching assembly precision control: The truss assembly adopts a multi-segment continuous matching assembly scheme. The truss assembly and trial assembly are carried out simultaneously. It is required that each round has no less than 4 trusses. After the previous round of assembly is completed, one section is left as the mother section of the next round to participate in the assembly, so as to ensure the smooth connection between adjacent trusses. The assembly sequence is positioning the upper and lower chords → assembling the webs → welding the welds between the webs and the lower chord nodes → welding the welds between the webs and the upper chord nodes;

[0013] S3: Control of assembly accuracy of large integral sections: After the main truss pieces, highway bridge deck blocks, railway steel box bridge decks and cross-joint pieces are assembled and welded and tested to be qualified, the whole section assembly begins. The whole section assembly adopts multi-section continuous matching assembly. The first section is assembled in the following process sequence: railway steel box bridge deck on one side is in place → middle truss piece assembly → railway steel box bridge deck on the other side is assembled → truss pieces on both sides are assembled → cross-joint piece assembly → upper highway bridge deck block assembly. The subsequent whole sections are assembled by first positioning and assembling the middle truss pieces on the assembled whole sections, and then assembling the railway steel box bridge deck on the sides. The latter sequence is the same as the first section. The overall assembly of steel trusses is completed on a large special assembly cradle. After the cradle is manufactured, the elevation of the piers at the segment nodes and the ring mouth is measured, and the cradle elevation is strictly controlled within ±1mm. After each round of whole section assembly is completed, the whole section pre-assembly inspection is carried out.

[0014] S3.1: Measure the interface dimensions of the entire segment: Ensure the bolt hole passing rate and connection quality by measuring the girder width, girder height, diagonal difference, bridge centerline position, main girder center distance, camber, and panel slope; the overall assembly line of the steel truss is ensured by the tire frame, and the camber value is adjusted by the wedge-shaped adjustable pads on the tire frame; the deviation between the segment and the centerline is adjusted by the sliding support of the tire frame pier;

[0015] S3.2: Measure the pre-assembly dimensions of the entire segment: measure the pre-assembly length of the entire segment, the length between segments, the lateral bend, the axis and the spacing between anchor points. The measuring points are arranged on the center line of the main truss. The three-dimensional coordinates of each point are measured using a total station to ensure the accuracy of the geometric dimensions of the entire segment assembly. After the segment assembly is completed, the elevations of the bridge deck nodes and ring openings are measured using a precision level. The camber and panel slope of the entire segment are measured. Together with the measured interface dimensions, they form a complete set of accurate assembly data to ensure that the camber value is within the requirements of the manufacturing acceptance rules.

[0016] S3.3: Measuring point marking: After the entire segment is assembled, the measuring points such as the main truss centerline, camber, bridge centerline, etc. are clearly marked on the surface of the entire segment as the basis for bridge installation positioning and connection construction;

[0017] S3.4: Welding control: During the assembly of the integral trusses, the welds are full penetration welds; a 3mm welding shrinkage is reserved in the height direction of the main truss, and the upper chord and web welds can only be welded after the lower chord and web welds are welded; multiple sections are assembled in a continuous matching manner, and the process splicing plates are pre-spliced ​​with rivets and bolts before welding; the reserved amount is monitored and tracked at any time, and senior welders and robots are selected to weld the welds to ensure the first-time pass rate of the welds; the welding process is strictly carried out in accordance with the welding parameters specified in the welding process, and a welding method with low line energy is adopted; multi-layer and multi-pass welding must be performed symmetrically on both sides; welding deformation is reduced to ensure the size of the rods.

[0018] Furthermore, in the precision control of the S1.2 vertical plate unit, the material connection position avoids the hole group and the main welding position of the rod.

[0019] Furthermore, in the S2.2: continuous matching assembly precision control, in order to avoid error accumulation, each segment truss piece must be measured after assembly, and welding can only be carried out after the measurement is qualified; during the truss piece assembly process, the assembled nodes must also be measured and controlled.

[0020] The advantages of the present invention are:

[0021] 1) In the present invention, the manufacturing accuracy of the double integral node chord is controlled, the distortion of the rod is controlled by the accuracy of the inner partition, the deflection of the rod is controlled by the accuracy of the vertical plate unit, and the arching accuracy is ensured by the accuracy of the chord hole group; the box opening size, the deformation of the controlled rod, the welding shrinkage, the bolt hole accuracy and the quality of the relationship between the hole groups are guaranteed; by arranging a three-dimensional measurement control network, all measurement points of the tire frame and the segment are directly and accurately monitored through the measurement control network to avoid cumulative measurement errors and improve assembly accuracy; by assembling the entire segment continuously, the entire segment that has been assembled first is used as the mother segment of the subsequent assembled entire segment, thereby improving the assembly accuracy; at the same time, the welding quality is controlled during the assembly process to reduce welding deformation to ensure the size of the rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0023] Figure 1 The present invention discloses a process flow chart for controlling the pre-camber of a large-segment continuous steel truss.

[0024] Figure 2 The present invention is a schematic diagram of the vertical plate unit material connection structure of a pre-camber control process for manufacturing a large-segment continuous steel truss beam.

[0025] Figure 3 The present invention is a schematic diagram of the steel truss segment arching structure of a large-segment continuous steel truss manufacturing pre-arch control process.

[0026] Figure 4 The present invention discloses a main truss assembly dimension control diagram for a pre-camber control process for manufacturing a large-segment continuous steel truss girder.

[0027] Figure 5 The present invention is a schematic diagram of the assembly of segment trusses for a pre-camber control process for manufacturing a large-segment continuous steel truss.

[0028] Figure 6 The present invention is a schematic diagram of the whole-segment pre-assembly camber measuring points of a pre-camber control process for manufacturing a large-segment continuous steel truss girder. DETAILED DESCRIPTION

[0029] 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.

[0030] 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.

[0031] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0032] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0033] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0034] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] like Figure 1A pre-camber control process for manufacturing a large-segment continuous steel truss is shown, and the specific control process is as follows:

[0036] S1: Control of the manufacturing accuracy of double integral node chords:

[0037] S1.1: Precision control of inner partitions: The inner partitions are used as a mold for geometric precision control of box-shaped rods and exist in the box body. The inner partitions are used to control the size of the rod box opening and ensure that the distortion of the proximal and distal ends of the chord is ≤2.0mm; the verticality deviation of the plate edge is ≤0.5mm; the inner partitions are cut and cut with precision, and the inner partitions are assembled by marking and welding is performed symmetrically in the same direction to ensure the straightness of the inner partitions.

[0038] S1.2: Vertical plate unit precision control: The vertical plate unit is composed of an integral node plate, a vertical plate and longitudinal plate ribs; the vertical plate unit is carried out in four steps: cutting parts, machining, joining and welding longitudinal ribs; if the width of the vertical plate unit is greater than 4100mm, the steel plate joining should be completed first, and then cutting should be carried out to ensure the external dimensions of the vertical plate unit; the vertical plate unit should be accurately marked after cutting and leveling, including the diagonal rod, vertical rod axis, horizontal center line and the machining line of the butt end; the vertical plate unit is machined and controlled according to the allowable deviation of the member L>8m and the lateral bend f≤3.0mm, and at the same time, it is ensured that the center distance between the two node plates of the lower chord meets the accuracy requirements within the range of ±2.0mm; in the precision control of the S1.2 vertical plate unit, the joining position avoids the hole group and the main weld position of the member.

[0039] S1.3: Precision control of chord rod hole groups: The chord rod is provided with connection hole groups at both ends. The bolt holes at both ends of the chord rod are drilled simultaneously by a double gantry 3D CNC drilling machine. The X-Y-Z three-axis drilling of the double gantry 3D CNC drilling machine can ensure that the bolt holes in different planes are not misaligned in the longitudinal and transverse directions, and the concentricity deviation of the bolt holes on the vertical plates on both sides is controlled within 1.0mm; the vertical plate extreme edge hole distance deviation is ensured to be within 1.0mm.

[0040] S1.4: Arching process: The chord is a straight rod. When assembling, the horizontal line on each part is used as the reference to ensure that the straightness of the six points AF, including the upper end point of the same rod and the two points on both sides of the vertical rod installation position, is as follows: Figure 2 As shown; the upper and lower chords need to be superimposed with elongation during production, and the elongation of the upper and lower chords is achieved by lengthening the length of the chord top plate; the steel trusses within the vertical curve range of the facade are straight instead of curved, and the lower chord system line is used as the baseline for manufacturing and lofting, and the intersection of the lower chord system line of each segment is located on the theoretical vertical curve; within the straight longitudinal slope range of the side span, the lower chord system line coincides with the theoretical longitudinal slope, and then the arch control is achieved by the process of staggered holes in the splicing plate, as shown Figure 3 shown.

[0041] S2: Accurate layout of three-dimensional measurement and control network: Construct a three-dimensional measurement and control network including a leveling network, a plane linear control network and a total station measurement base station; use a total station and a theodolite to directly and accurately monitor all measurement points of the tire frame and segments through the measurement and control network to avoid cumulative measurement errors; the assembly camber value is determined according to the drawings, and the camber is adjusted by the elevation of the pads and adjustment blocks on the load-bearing piers, and is measured and controlled using high-precision levels and leveling control points.

[0042] S2.1: Control of girder assembly accuracy: The main girder is fully welded internally. Welding shrinkage and deformation require strict control of its dimensions. It is necessary to ensure the girder height and diagonal difference, as well as the connection between the main girder and the crossbeam, and avoid misalignment of the box mouth. Figure 4 As shown, the allowable deviations of the main truss dimensions are as follows: the allowable deviation of the truss height H is +2.0 to +4.0 mm; the allowable deviation of the 1 / 2 diagonal rod interface position H1 is +1.0 to +2.0 mm; the allowable deviation of the diagonal rod centerline length is +1.0 to +2.0 mm; L 5 Allowable deviation 0~+3.0 mm; horizontal distance between anchor point and node center L 0Tolerance 0~+3.0 mm; Diagonal difference│ L 2- L 3│The allowable deviation is not more than 3.0mm; the node center distance L 1 Allowable deviation -1.0~+3.0 mm; distance between the end hole of the chord and the center of the node L 0 allowable deviation 0~+2.0mm; extreme edge hole distance L The allowable deviation is 0~+2.0 mm; the misalignment of the interface of the oblique and vertical rod cover is not greater than 1.5 mm; the flatness is not greater than 3.0 mm; the out-of-plane bending of the truss is not greater than 4.0 mm; the distortion of the truss is not greater than 3.0 mm; the centerline matching deviation of the upper and lower chords and diagonal webs of adjacent entire segments is controlled to be no greater than ±0.5 mm.

[0043] S2.2: Continuous matching assembly precision control: The truss assembly adopts a multi-segment continuous matching assembly scheme. The truss assembly and trial assembly are carried out simultaneously. It is required that each round has no less than 4 trusses. After the previous round of assembly is completed, one section is left as the mother section of the next round to participate in the assembly, so as to ensure the smooth connection between adjacent trusses. Figure 5 As shown; the assembly sequence is positioning the upper and lower chords → assembling the web → welding the weld between the web and the lower chord node → welding the weld between the web and the upper chord node; in the continuous matching assembly accuracy control, in order to avoid error accumulation, each segment truss piece must be measured after assembly, and welding can only be carried out after the measurement is qualified; during the truss assembly process, the assembled nodes must also be measured and controlled.

[0044] S3: Control of assembly accuracy of large integral sections: After the main truss pieces, highway bridge deck blocks, railway steel box bridge deck and cross-joint pieces are assembled and welded and tested to be qualified, the whole section assembly begins. The whole section assembly adopts multi-segment continuous matching assembly. The first section is assembled in the following process sequence: railway steel box bridge deck on one side is in place → middle truss piece is assembled → railway steel box bridge deck on the other side is assembled → truss pieces on both sides are assembled → cross-joint piece is assembled → upper highway bridge deck block is assembled. The subsequent whole sections are assembled by first positioning and assembling the middle truss piece on the assembled whole section, and then assembling the side railway steel box bridge deck. The latter sequence is the same as the first section. The overall assembly of steel trusses is completed on a large special assembly cradle. After the cradle is manufactured, the elevation of the piers at the segment nodes and the ring mouth is measured, and the cradle elevation is strictly controlled within ±1mm. After each round of whole section assembly is completed, the whole section is pre-assembled and tested.

[0045] S3.1: Measure the interface dimensions of the entire segment: Ensure the bolt hole pass rate and connection quality by measuring the truss width, truss height, diagonal difference, bridge centerline position, main truss center distance, camber, and panel slope; the overall assembly line of the steel truss is guaranteed by the frame, and the camber value is adjusted by the wedge-shaped adjustable pads on the frame; the deviation between the segment and the centerline is adjusted by the sliding support of the frame pier.

[0046] S3.2: Measure the pre-assembly dimensions of the entire segment: Measure the pre-assembly length of the entire segment, the length between segments, the lateral bend, the axis and the spacing between anchor points. The measuring points are arranged on the center line of the main truss. The three-dimensional coordinates of each point are measured using a total station to ensure the accuracy of the geometric dimensions of the entire segment assembly. After the segment assembly is completed, the elevations of the bridge deck nodes and ring openings are measured using a precision level. The camber and panel slope of the entire segment are measured, and together with the measured interface dimensions, a complete set of accurate assembly data is formed to ensure that the camber value is within the requirements of the manufacturing acceptance rules. Figure 6 As shown; that is: when f When ≤60, the allowable deviation is ±3mm; when f >60, allowable deviation ±5 f / 100, and ≤10, f To calculate the camber, the axis deviation of the entire segment is measured to ensure that the assembly error is within the allowable deviation of ±1.5mm.

[0047] S3.3: Measuring point marking: After the entire segment is assembled, the main truss centerline, camber, bridge centerline and other measuring points are clearly marked on the surface of the entire segment as the basis for bridge installation positioning and connection construction.

[0048] S3.4: Welding control: During the assembly of the integral trusses, the welds are full penetration welds; a 3mm welding shrinkage is reserved in the height direction of the main truss, and the upper chord and web welds can only be welded after the lower chord and web welds are welded; multiple sections are assembled in a continuous matching manner, and the process splicing plates are pre-spliced ​​with rivets and bolts before welding; the reserved amount is monitored and tracked at any time, and senior welders and robots are selected to weld the welds to ensure the first-time pass rate of the welds; the welding process is strictly carried out in accordance with the welding parameters specified in the welding process, and a welding method with low line energy is adopted; multi-layer and multi-pass welding must be performed symmetrically on both sides; welding deformation is reduced to ensure the size of the rods.

[0049] Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining 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 fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A process for controlling the pre-camber of a large-segment continuous steel truss, characterized in that: The specific control process is as follows: S1: Control of the manufacturing accuracy of double integral node chords: S1.1: Inner baffle precision control: The inner baffle exists in the box body as a mold for geometric precision control of the box-shaped rod. The inner baffle controls the size of the rod box opening and ensures that the distortion of the near and far ends of the chord is ≤2.0mm; the verticality deviation of the plate edge is ≤0.5mm; the inner baffle is cut by precision cutting, and the inner baffle is assembled by marking and symmetrical welding in the same direction to ensure the straightness of the inner baffle; S1.2: Vertical plate unit precision control: The vertical plate unit is composed of an integral node plate, a vertical plate and longitudinal plate ribs; the vertical plate unit is processed in four steps: cutting parts, machining, joining and welding longitudinal ribs; if the width of the vertical plate unit is greater than 4100mm, the steel plate joining should be completed first, and then the cutting should be carried out to ensure the vertical plate unit's external dimensions; the vertical plate unit should be accurately marked after cutting and leveling, including the diagonal rod, the vertical rod axis, the horizontal center line and the machining line of the butt end; the vertical plate unit should be machined and controlled according to the allowable deviation of the rod L>8m and the lateral bending f≤3.0mm, and at the same time, the center distance between the two node plates of the lower chord should be ensured to meet the accuracy requirements within the range of ±2.0mm; S1.3: Precision control of chord rod hole groups: The chord rod is provided with connection hole groups at both ends. The bolt holes at both ends of the chord rod are drilled simultaneously by a double-gantry 3D CNC drilling machine, and the double-gantry 3D CNC drilling machine drills simultaneously on the X-Y-Z axes to ensure that the bolt holes on different planes are not misaligned in the longitudinal and transverse directions, and that the concentricity deviation of the bolt holes on the vertical plates on both sides is controlled within 1.0mm; and that the vertical plate polar edge hole distance deviation is within 1.0mm; S1.4: Arching process: The chord is a straight rod. When assembling, the horizontal line on each part is used as the reference to ensure the straightness of six points, including the upper end point of the same rod and two points on both sides of the vertical rod installation position on the rod; The upper and lower chords need to be superimposed with elongation during production, and the elongation of the upper and lower chords is achieved by lengthening the length of the chord top plate; the steel trusses within the vertical curve range of the facade are straight instead of curved, and the manufacturing and lofting takes the lower chord system line as the baseline, and the intersection of the lower chord system line of each segment is located on the theoretical vertical curve; within the straight longitudinal slope range of the side span, the lower chord system line coincides with the theoretical longitudinal slope, and then the arch control is achieved by the process of staggered holes in the splicing plate; S2: Accurate layout of three-dimensional measurement and control network: Construct a three-dimensional measurement and control network including a leveling network, a plane linear control network and a total station measurement base station; use a total station and a theodolite to directly and accurately monitor all measurement points of the tire frame and segments through the measurement and control network to avoid cumulative measurement errors; the assembly camber value is determined according to the drawings, and the camber is adjusted by the elevation of the pad and the adjustment block on the load-bearing pier, and is measured and controlled using a high-precision level and leveling control points; S2.1: Control of girder assembly accuracy: The main girder is fully welded internally, and the shrinkage and deformation of welding require strict control of its dimensions, which must ensure the girder height and diagonal difference, as well as the connection between the main girder and the crossbeam, while also avoiding misalignment of the box openings; S2.2: Continuous matching assembly precision control: The truss assembly adopts a multi-segment continuous matching assembly scheme. The truss assembly and trial assembly are carried out simultaneously. It is required that each round has no less than 4 trusses. After the previous round of assembly is completed, one section is left as the mother section of the next round to participate in the assembly, so as to ensure the smooth connection between adjacent trusses. The assembly sequence is positioning the upper and lower chords → assembling the webs → welding the welds between the webs and the lower chord nodes → welding the welds between the webs and the upper chord nodes; S3: Control of assembly accuracy of large integral sections: After the main truss pieces, highway bridge deck blocks, railway steel box bridge decks and cross-joint pieces are assembled and welded and tested to be qualified, the whole section assembly begins. The whole section assembly adopts multi-section continuous matching assembly. The first section is assembled in the following process sequence: railway steel box bridge deck on one side is in place → middle truss piece assembly → railway steel box bridge deck on the other side is assembled → truss pieces on both sides are assembled → cross-joint piece assembly → upper highway bridge deck block assembly. The subsequent whole sections are assembled by first positioning and assembling the middle truss pieces on the assembled whole sections, and then assembling the railway steel box bridge deck on the sides. The latter sequence is the same as the first section. The overall assembly of steel trusses is completed on a large special assembly cradle. After the cradle is manufactured, the elevation of the piers at the segment nodes and the ring mouth is measured, and the cradle elevation is strictly controlled within ±1mm. After each round of whole section assembly is completed, the whole section pre-assembly inspection is carried out. S3.1: Measure the interface dimensions of the entire segment: Ensure the bolt hole passing rate and connection quality by measuring the girder width, girder height, diagonal difference, bridge centerline position, main girder center distance, camber, and panel slope; the overall assembly line of the steel truss is ensured by the tire frame, and the camber value is adjusted by the wedge-shaped adjustable pads on the tire frame; the deviation between the segment and the centerline is adjusted by the sliding support of the tire frame pier; S3.2: Measure the pre-assembly dimensions of the entire segment: measure the pre-assembly length of the entire segment, the length between segments, the lateral bend, the axis and the spacing between anchor points. The measuring points are arranged on the center line of the main truss. The three-dimensional coordinates of each point are measured using a total station to ensure the accuracy of the geometric dimensions of the entire segment assembly. After the segment assembly is completed, the elevations of the bridge deck nodes and ring openings are measured using a precision level. The camber and panel slope of the entire segment are measured. Together with the measured interface dimensions, they form a complete set of accurate assembly data to ensure that the camber value is within the requirements of the manufacturing acceptance rules. S3.3: Measuring point marking: After the entire segment is assembled, the main truss centerline, camber, and bridge centerline measuring points are clearly marked on the surface of the entire segment as the basis for bridge installation positioning and connection construction; S3.4: Welding control: During the assembly of the integral trusses, the welds are full penetration welds; a 3mm welding shrinkage is reserved in the height direction of the main truss, and the upper chord and web welds can only be welded after the lower chord and web welds are welded; multiple sections are assembled in a continuous matching manner, and the process splicing plates are pre-spliced ​​with rivets and bolts before welding; the reserved amount is monitored and tracked at any time, and senior welders and robots are selected to weld the welds to ensure the first-time pass rate of the welds; the welding process is strictly carried out in accordance with the welding parameters specified in the welding process, and a welding method with low line energy is adopted; multi-layer and multi-pass welding must be performed symmetrically on both sides; welding deformation is reduced to ensure the size of the rods.

2. The process for controlling the pre-camber of a large-segment continuous steel truss according to claim 1, characterized in that: In the precision control of the S1.2 vertical plate unit, the material connection position avoids the hole group and the main welding position of the rod.

3. The process for controlling the pre-camber of a large-segment continuous steel truss according to claim 1, characterized in that: S2.2: In the control of the precision of continuous matching assembly, in order to avoid error accumulation, each segment truss piece must be measured after assembly, and welding can only be carried out after the measurement is qualified; during the truss assembly process, the assembled nodes must also be measured and controlled.

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