A method for assembling and constructing a steel truss girder structure

Abstract

This application relates to the field of long-span steel bridge construction technology, and particularly to a method for assembling steel truss girder segments. To address the difficulties in installing the "vertical clamping" structure of the diagonal and vertical members and the chord members during steel truss girder segment assembly, the high difficulty of welding and turning over, and the low accuracy of multi-segment matching, this application proposes the following solution: A hydraulic lifting and adjusting device is used to achieve three-way adjustment of the upper chord; the upper chord is initially positioned to the theoretical truss height plus a preset offset, and after inserting the diagonal and vertical members, it is precisely positioned to the theoretical dimensions; multiple welding bevels of various styles are used, including a single-sided V-shaped bevel on the upper flange and a transitional bevel between single-sided and double-sided V-shaped bevels on the lower flange, combined with a specific welding sequence to achieve non-turning, fully horizontal welding; and multi-segment continuous matching and positioning is achieved through a long-line method with pre-arching and punching pins. This application can precisely control structural dimensions, avoid overhead welding and turning over operations, improve construction efficiency and safety, and is applicable to the factory manufacturing of the main truss segments of fully welded steel truss girder bridges.

Description

Technical Field

[0001] This application relates to the field of long-span steel bridge construction technology, specifically to a method for assembling and constructing steel truss girder segments. Background Technology

[0002] With the rapid development of transportation infrastructure construction, long-span double-deck steel truss bridges have been widely used in bridges spanning rivers, seas, and mountain canyons due to their advantages such as high load-bearing capacity, large spanning capacity, and good structural rigidity. Currently, long-span steel truss bridges generally adopt a construction mode of factory-manufacturing integral segments and on-site assembly. That is, the main truss structure, orthogonal irregular bridge deck system structure, and bridge deck cross bracing are manufactured into integral segments in the factory and then transported to the bridge site for connection. This mode effectively reduces the amount of on-site high-altitude work, lowers construction safety risks, and simultaneously ensures the manufacturing precision and quality of the bridge structure.

[0003] The main truss structure of a steel truss generally consists of an upper chord, lower chord, diagonal members, and vertical members. The main connection methods are welding and high-strength bolting. While high-strength bolting facilitates on-site assembly, it suffers from cumbersome construction procedures, a large number of bolts, and difficulties in later operation and maintenance. Fully welded main truss structures offer advantages such as good integrity, high fatigue strength, and maintenance-free operation, and are gradually becoming the mainstream technology.

[0004] However, the factory manufacturing of the all-welded main truss structure still faces the following technical challenges: First, controlling the alignment precision during assembly is extremely difficult. In the main truss structure, the diagonal and vertical members are typically connected to the upper and lower chords using an insert-type gusset plate structure, forming a "vertical clamping" clamping structure. Traditional assembly methods require ensuring the longitudinal, transverse, and vertical three-dimensional spatial dimensions of the upper and lower chords simultaneously, and the diagonal and vertical members must be precisely inserted into the gusset plates. Alignment adjustment is extremely difficult, and even slight deviations can lead to assembly failure or welding gaps exceeding tolerances.

[0005] Secondly, welding and turning over is difficult and carries the risk of overhead welding. Large truss structures are heavy and large in size, and turning them over requires large turning equipment and hoisting resources, which is not only costly and poses a great safety risk, but also easily leads to structural deformation during the turning process. If all-position welding without turning over is used, there will inevitably be an overhead welding position. Overhead welding is difficult to operate and the welding quality is hard to guarantee, especially for penetration welds, where the defect rate of overhead welding is much higher than that of flat welding.

[0006] Third, high precision is required for continuous matching of multiple segments. The longitudinal alignment of the bridge (including pre-camber) requires that each segment of the truss be continuously matched in a stress-free state in the factory. The splicing accuracy of adjacent segments directly affects the final bridge alignment. The traditional method of manufacturing each segment independently and then matching them results in large accumulated errors, making it difficult to meet high precision requirements.

[0007] Existing technologies have introduced some improvements, such as using three-way hydraulic jacks for fine-tuning and positioning (e.g., Chinese Invention Patent, Application No.: CN116537055A), employing narrow-gap bevels to avoid overturning during welding (e.g., Chinese Invention Patent, Application No.: CN116117283A), or using matching jigs for long-line manufacturing. However, these technologies are independent of each other and fail to form a complete, synergistic systematic construction method to solve the aforementioned three major problems. In particular, for the assembly of "vertical clamping" insertion structures, no effective dedicated solution has yet been found in the existing technology.

[0008] Therefore, developing a construction method that can simultaneously solve the three major technical challenges of high-precision assembly of truss structures, high-quality welding without turning over, and continuous matching of multiple segments has significant engineering application value. Summary of the Invention

[0009] The technical problem to be solved by this application is to overcome the shortcomings of existing steel truss girder segment assembly construction, such as the difficulty in controlling the assembly alignment accuracy, the difficulty in turning over the weld and the easy occurrence of overhead welding defects, and the insufficient accuracy of continuous matching of multiple segments, and to provide a truss segment assembly construction method that can achieve precise alignment, welding without turning over, and continuous matching.

[0010] To achieve the above objectives, this application provides a method for assembling and constructing a steel truss girder segment structure, employing the following technical solution: A method for assembling and constructing a steel truss girder structure includes the following steps: S1. Manufacturing basic unit components for steel truss beams, including upper chord segments, lower chord segments, diagonal segments, and vertical segments; by strictly controlling the processing accuracy of various unit components (including length, end angle, node plate position, etc.), a basic quality guarantee is provided for subsequent assembly. S2. Provide a hydraulic jacking and beam adjusting device, which includes a lower support system, a jacking system, a limit device and a central controller, and can realize independent adjustment in three directions: longitudinal, lateral and vertical. S3. Position the first section of the lower chord and level it to make the lower support stable. Place the first section of the upper chord above the lower chord and adjust the upper chord to the initial positioning state using the hydraulic lifting and adjusting beam device. The initial positioning state is that the distance between the upper chord and the lower chord is L_theoretical + ΔH, where L_theoretical is the theoretical design distance and ΔH is the preset offset. The value of ΔH ranges from 300mm to 800mm. S4. In the initial positioning state, insert both ends of the diagonal member segment and / or the vertical member segment into the lower chord node plate and the upper chord node plate respectively, and temporarily fix them after adjusting them to the design angle; The reason for adopting a two-step adjustment method from initial positioning (e.g., raising by 500mm) to precise positioning (theoretical distance) in this step is that: if the positioning is directly based on the theoretical distance, the diagonal and vertical rods cannot be inserted; if they are pressed directly to the theoretical position from the raised state after insertion, the descent displacement needs to be precisely controlled by a hydraulic device, while ensuring that the gaps between the ends of the diagonal and vertical rods and the node plate are uniform. The two-step method of this application realizes the technological innovation of "first creating space for insertion, then precisely pressing and positioning", which completely solves the installation problem of the "vertical clamping" structure. S5. Using a hydraulic jacking and adjusting device, precisely position the upper chord with the inserted diagonal and / or vertical members, adjusting it to a distance of Ltheoretical + ΔL between it and the lower chord, where ΔL is the allowance for welding shrinkage compensation. Measure the three-dimensional coordinates of the intersection of the chord axis and the node plate using a total station to ensure that the longitudinal, lateral, and vertical alignment dimensions of the upper and lower chords meet design requirements. After adjustment, install fixing fixtures at the bottom to temporarily stabilize the upper chord. The chord axis refers to the theoretical axis along the length of the chord. S6. The first main truss segment is installed successfully, and the installation and positioning of the subsequent main truss segments will begin. First, the lower chord of the second segment will be installed. The planar position relationship between the second lower chord and the first lower chord will be adjusted to ensure that the longitudinal alignment meets the design requirements. The two lower chords will be fastened together using splicing plates. S7. Repeat step S3 to initially position the upper chord of the second segment; repeat step S4 to install the diagonal and vertical members of the second segment; repeat step S5 to precisely adjust and fix the upper chord of the second segment, and then bolt the two upper chords together and bolt the diagonal members connecting the two segments together using splicing plates. S8. Following step S7, complete multiple main truss segments. Using the long-line method and setting pre-arches according to the manufacturing line shape required by the design, complete the continuous matching and positioning installation of multiple main truss segments. Perform overall line shape measurement on the assembled multi-segment continuous matching assembly, including longitudinal line shape, truss height, and node diagonal. After passing the measurement, proceed to the welding process. S9. A multi-segment, multi-style welding bevel is used for welding between the diagonal / vertical members and the chord node plates. This multi-segment, multi-style welding bevel is as follows: in the truss assembly posture, the upper flange of the diagonal or vertical member is set with a single-sided V-groove, while the lower flange is set with a multi-segment, multi-style transition bevel combining single-sided and double-sided V-grooves. Welding is performed in the following order: first, weld the butt weld of the lower flange between the diagonal member flange and the node plate; then weld the butt weld of the upper flange; then weld the fillet weld between the vertical member web and the top plate of the lower chord and the bottom plate of the upper chord; finally, weld the fillet weld between the diagonal member web and the node plate. This sequence follows the principle of "flange first, then web; butt weld first, then fillet weld," effectively controlling welding deformation and ensuring weld quality.

[0011] By combining the above-mentioned bevel forms and welding sequence, this application achieves high-quality welding of all welds without flipping the truss structure, avoiding the safety risks and deformation problems caused by flipping large trusses. At the same time, all welds can be in flat welding or ship-shaped welding positions, which is convenient to operate and reliable in quality.

[0012] Furthermore, in step S2, the maximum lifting force of the hydraulic jacking and adjusting beam device is 500KN, the limiting device prevents overturning due to excessive limits, and the central controller connects each lifting cylinder and lateral movement cylinder, adjusting the displacement in each direction in real time through data feedback from the total station; each hydraulic jacking and adjusting beam device is equipped with an independent longitudinal adjusting cylinder, lateral adjusting cylinder and vertical lifting cylinder, and multiple devices can be arranged longitudinally along the upper chord, and are coordinated uniformly or controlled independently by the central controller.

[0013] Furthermore, in step S3, the preset offset ΔH is set to 500mm. The purpose of this offset is as follows: due to the "vertical clamping" structure where the vertical bar and the upper and lower chords are clamped at a 90° angle, if the upper and lower chords are positioned directly according to the theoretical distance, the diagonal bar and vertical bar cannot be inserted between the node plates of the upper and lower chords (because insertion requires a certain amount of operating space). By pre-raising the upper chord by a certain distance, sufficient space is created for the insertion of the diagonal bar and vertical bar.

[0014] Furthermore, in step S5, the value range of the reserved welding shrinkage compensation amount ΔL is 0-20mm, preferably 10mm. Furthermore, in step S6, the long-line continuous matching and positioning method includes: setting a pre-arch according to the manufacturing alignment required by the design; using punches 0.2mm smaller than the bolt hole diameter for positioning between each segment of the main truss to ensure connection accuracy; and then using splicing plates for temporary bolting. This method enables high-precision matching of multiple segments under stress-free conditions, simulating the bridge alignment.

[0015] Further, in step S4, before inserting the diagonal and / or vertical segments into the node plates, they are pre-rotated by a certain angle to ensure they are in a position conducive to insertion. After both ends are inserted into the node plates, they are rotated to the designed angle, and temporary supports are installed at the bottom. The temporary supports are adjustable screw supports, and PTFE sliding plates or rollers are installed between the support head and the vertical rod, allowing the vertical rod to slide freely in the axial direction while restricting only lateral displacement and rotation.

[0016] Furthermore, in step S8, the specific form of the multi-segment, multi-style welding bevel is as follows: in the width direction of the diagonal or vertical bar, the connection between the wing plate and the web plate adopts an arc transition, the blunt edge of the single-sided V-shaped bevel of the upper wing plate is 2-4mm, and the bevel angle is 45°-60°; the single-sided V-shaped bevel segment and the double-sided V-shaped bevel segment of the lower wing plate are alternately set or gradually transitioned according to the length ratio of 1:1-2:1.

[0017] Furthermore, in step S2, the hydraulic lifting and adjusting beam device is also equipped with a displacement sensor and an inclination sensor. The displacement sensor is used to monitor the displacement in all directions in real time, and the inclination sensor is used to monitor the spatial attitude angle of the upper chord. All sensor data are transmitted to the central controller for closed-loop control.

[0018] The working principle of this application can be understood from the following three aspects: (1) Working principle of the hydraulic jacking two-step installation method: For the "vertical clamping" structure where the vertical member and the upper and lower chords are clamped at a 90° angle (see...), Figure 1 If the upper chord is directly positioned at the theoretical height, the opening distance between the lower chord node plate and the upper chord node plate would be exactly equal to the length of the vertical member, and both ends of the vertical member would need to be inserted into both node plates simultaneously. Since the vertical member requires a certain tilt angle to enter the node plate opening during insertion, and the space between the upper and lower chords is insufficient for the vertical member to tilt at a sufficient angle, direct installation is impossible.

[0019] The proposed solution is as follows: First, the upper chord is raised by an offset ΔH (preferably 500mm). At this point, the opening distance between the upper and lower chord node plates increases by ΔH, which is much greater than the length of the vertical member. This allows the vertical member to be easily tilted at a certain angle (e.g., 20°-30°), its lower end inserted into the lower chord node plate. Then, the vertical member is rotated so that its upper end aligns with the upper chord node plate and is inserted, completing the insertion operation. Subsequently, the upper chord is slowly lowered to its theoretical height (Ltheoretical) using a hydraulic jacking and adjusting beam device. During the descent, both ends of the vertical member gradually press against the inside of the node plate, ultimately forming a tight connection. The three-way adjustment capability of the hydraulic device ensures longitudinal and lateral alignment accuracy during the descent process, preventing skewing.

[0020] 2) Working principle of multi-segment, multi-style bevel welding without turning over: In conventional all-position welding, the overhead welding position is prone to sag due to gravity, resulting in defects such as undercut, lack of fusion, and porosity. This application improves the weld formation by optimizing the bevel design, thereby altering the stress direction and heat dissipation conditions.

[0021] For the single-sided V-groove of the upper flange, the arc points from the top to the bottom of the groove during welding, and the molten pool spreads naturally under gravity, making defects less likely. For the lower flange, if a simple single-sided V-groove is used, the penetration depth during welding is difficult to guarantee root fusion; if a double-sided V-groove is used, back root cleaning or flip welding is required. The innovation of this application lies in: using a single-sided V-groove with a backing pad in specific sections of the lower flange (such as the middle section), while using a double-sided V-groove but welding only from one side in sections with high stress or gap changes, and using a ceramic backing pad on the back to form forced shape, achieving single-sided welding with double-sided forming. This "multi-segment, multi-style" design is customized according to the actual weld length direction and the stress gradient and gap changes on the cross-section, so that each weld can find the most suitable groove shape without flipping.

[0022] By using a specific welding sequence (lower flange → upper flange → web fillet weld → web penetration fillet weld), heat input and deformation direction can be controlled, ultimately achieving low-stress, high-quality, non-turnover welding.

[0023] (3) Working principle of continuous matching and positioning in long-line method: A full-length jig is set up in the factory, and the top surface of the jig is three-dimensionally laid out according to the bridge design alignment (including pre-camber). The first lower chord section is positioned and fixed according to the alignment, and then the second, third, and so on lower chord sections are installed sequentially, with temporary splicing plates and punch pins connecting each section. The diameter of the punch pin is 0.2mm smaller than the diameter of the bolt hole, which ensures both smooth insertion and that the concentricity of the hole group is within 0.2mm. Through repeated measurements and adjustments, the system line (chord axis) and node line (intersection line between the crossbar and the chord) of each segment are made to transition continuously and smoothly. This "controlling the short line with the long line" process disperses the manufacturing error of a single segment along the long line, avoiding the accumulation of errors.

[0024] Compared with the prior art, this application has the following beneficial effects: 1. Breakthrough in the installation difficulties of the "vertical clamping" structure: A two-step installation method of "initial positioning and lifting offset → insertion of diagonal vertical bar → precision positioning and pressing" was creatively proposed. For the first time, a specific numerical range of offset of the upper chord bar applicable to the all-welded truss structure (300-800mm, preferably 500mm) was given, which completely solved the process bottleneck that the diagonal bar and vertical bar could not be inserted into the node plate of the upper and lower chord bars.

[0025] 2. Achieve parallel welding without turning over: By designing multi-segment, multi-style welding bevels (upper single-sided V-shape + lower single-sided V / double-sided V transition bevel) and a specific four-step welding sequence, all welds on the truss structure can be completed in parallel or hull-shaped positions while in the factory assembly posture, without the need for overall turning over or overhead welding operations. This not only reduces the investment cost of large lifting equipment and turning fixtures, but also significantly reduces the safety risks of high-altitude turning over, while significantly improving the stability of welding quality.

[0026] 3. High precision of multi-segment continuous matching: The continuous matching and positioning technology of long line method + pre-arch + punch (0.2mm smaller than the hole diameter) enables multi-segment truss panels to achieve precise docking in a stress-free state. The concentricity error of the hole group of adjacent segment splicing plates can be controlled within 0.2mm. The bridge alignment is verified in advance in the factory, and it can be directly connected without modification during on-site assembly.

[0027] 4. Systemic Synergistic Effect: The three core technical features of this invention (hydraulic jacking two-step installation method, multi-segment multi-style bevel welding method, and long-line continuous matching method) are not simply superimposed, but rather mutually supportive and synergistic. For example, the hydraulic jacking two-step installation method provides a high-precision assembly foundation for multi-segment continuous matching; the multi-segment multi-style bevel welding method allows the assembled structure to be welded without flipping it over, preserving the long-line matching state; and the long-line continuous matching method, in turn, verifies the dimensional stability of the two-step installation method; together, the three constitute a complete, closed-loop controlled high-precision truss assembly construction system. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below: Figure 1 This is a schematic diagram of the main truss structure involved in this application, including the upper chord, lower chord, vertical members, and diagonal members; Figure 2 This is a structural schematic diagram of the hydraulic jacking and beam adjusting device of this application, which includes a lower support system, a jacking system, a limit device, and a central controller; Figure 3 This is a schematic diagram of the initial positioning state of the upper chord in this application, showing that the distance between the upper chord and the lower chord is Lli + 500mm; Figure 4 This is a schematic diagram of the insertion and installation of the diagonal and vertical members in this application, showing the state of the diagonal / vertical members after pre-rotation angle when inserted into the upper and lower chord node plates; Figure 5 This is a flowchart illustrating the long-line continuous matching manufacturing process for the multi-segment main truss structure of this application. Figure 6 This is a schematic diagram of the multi-segment, multi-style welding bevels of this application, showing the structure of a single-sided V-shaped bevel on the upper flange and a multi-segment transition bevel on the lower flange. Detailed Implementation

[0029] The present application will be further described below with reference to the accompanying drawings and embodiments. These embodiments are for illustrative purposes only and do not constitute a limitation on the scope of protection of the present application.

[0030] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0031] In the description of this application, it should be noted that all terms used in this application (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains, and should not be construed as limiting this application; it should be further understood that the terms used in this application should be understood to have the same meaning as those in the context of this specification and the relevant field, and should not be understood in an idealized or overly formal sense, except as expressly defined in this application.

[0032] Example 1 like Figure 1-6 As shown in the figure, this embodiment provides a method for processing and manufacturing the main truss structure of a steel truss bridge.

[0033] Project Overview: This is a large-span, double-deck steel truss bridge. The main truss adopts a fully welded structure, with a segment length of 12m and a truss height of 16m. The standard segment of the main truss consists of an upper chord, a lower chord, vertical members, and diagonal members. The vertical members are connected to the upper and lower chords by insert-type, top-tight welding.

[0034] S1: Unit Manufacturing The top chord segments, bottom chord segments, diagonal segments, and vertical segments are manufactured separately in the factory. The top and bottom chords have box-shaped cross-sections, measuring 1200mm × 800mm, with a plate thickness of 32mm; the vertical segments have H-shaped cross-sections with flange plate thickness of 28mm; the diagonal segments have box-shaped cross-sections. All gusset plates are integrally welded to the chords, and the gusset plates have openings (for subsequent connections). Unit component machining accuracy control: length tolerance ±1mm, end angle tolerance ±0.1°, gusset plate position tolerance ±0.5mm. See... Figure 1 .

[0035] S2: Preparation of hydraulic jacking and beam adjusting device Design and manufacture three hydraulic jacking and beam adjusting devices (in this embodiment, the upper chord is 12m long and weighs approximately 18 tons, with one device spaced 4m apart along the longitudinal direction). Each device includes: Lower support system: base steel plate + four columns + crossbeams, load-bearing capacity 30 tons; Lifting system: vertical lifting cylinder (stroke 500mm, lifting force 200KN), longitudinal lateral movement cylinder (stroke ±100mm, thrust 50KN), lateral movement cylinder (stroke ±50mm, thrust 30KN). Limit device: Mechanical anti-tipping stop, triggered when the cylinder stroke exceeds the limit; Displacement sensor: measures real-time displacement in all directions with an accuracy of 0.1 mm; Inclination sensor: measures the cross slope and longitudinal slope of the upper chord; Central controller: PLC control cabinet, equipped with touch screen, can manually or automatically control the action of each hydraulic cylinder, and receive measurement data from the total station.

[0036] The three devices communicate with the central controller via industrial Ethernet, enabling them to operate in tandem or individually.

[0037] S3: Positioning of the lower chord of the first segment The first section of the lower chord (12m long, weighing 16 tons) was hoisted onto the long-line support frame using a gantry crane. The support frame had been laid out according to the bridge design alignment (including a 30mm pre-camber). The lower chord was placed on adjustable piers and adjusted to the design elevation and plane position using a level and total station. Then it was leveled, supported, and stabilized. The lower chord node plate was facing upwards, preparing for subsequent installation.

[0038] S4: Initial positioning of the upper chord The first section of the upper chord is hoisted onto the hydraulic jacking and beam-adjusting device (three devices have been pre-positioned above the lower chord at corresponding positions). The central controller is activated, and the total station measures the three-dimensional coordinates of the intersection of the upper chord axis and the node line. The longitudinal, lateral, and vertical positions of the upper chord are adjusted using the hydraulic device to ensure that its relative longitudinal and lateral positions with the lower chord meet the design requirements (planar alignment). The vertical adjustment is as follows: the distance between the bottom surface of the upper chord and the top surface of the lower chord = Ltheoretical + 500mm, where Ltheoretical = 16000mm (theoretical truss height), therefore the initial positioning distance is 16500mm.

[0039] S5: Diagonal and vertical bar insertion installation (1) Vertical rod installation: The vertical rod is 15990mm long (considering welding shrinkage), with insert-type structures at both ends. The vertical rod is horizontally hoisted between the upper and lower chords using a truck crane, with an initial angle of about 5° to the horizontal plane. Align the lower end of the vertical rod with the groove of the lower chord node plate and slowly insert it until the lower end enters the node plate to a depth of about 50mm. Then slowly rotate the vertical rod to make it more vertical, while raising the hook to align the upper end of the vertical rod with the groove of the upper chord node plate. Continue to rotate and insert until the upper end also enters the node plate to about 50mm. At this time, the vertical rod is in an inclined state (with an angle of about 5°-8° to the vertical direction). Set up temporary supports (jacks + pads) at the bottom, and then continue to adjust the vertical rod to the theoretical vertical position, and measure its top surface elevation and verticality, fixing it with the lower chord as the reference.

[0040] (2) Installation of diagonal bracing: The diagonal bracing is approximately 21.5m long, and both ends are also inserted into node plates. The installation method is to use two truck cranes with special rotating lifting tools to adjust the attitude of the diagonal bracing in the air, insert both ends, and rotate it to the design angle (approximately 45° with the horizontal plane), and set up temporary supports.

[0041] S6: Precision positioning of the upper chord rod After all the diagonal and vertical members are installed and temporarily secured, the hydraulic jacking and adjusting device is activated to slowly lower the upper chord. The descent is paused when the upper chord reaches a distance of 16010mm (Lreasonable + 10mm) from the lower chord, monitored in real-time by a total station. The gaps between the end faces of the diagonal and vertical members and the interior of the node plate are measured, ensuring uniform gaps not exceeding 2mm. Any deviations are corrected using the lateral and longitudinal fine-tuning functions of the hydraulic device. Finally, the upper chord is precisely positioned at Lreasonable + 10mm (allowing for welding shrinkage). After all dimensions are verified to be within acceptable limits, temporary support fixtures are welded to the lower part of the upper chord for fixation.

[0042] S7: Subsequent segment assembly Install the second, third, and so on, up to the sixth segment, following the same steps (a total of 6 segments were manufactured, with a total length of 72m). After each segment's lower chord is installed, it is temporarily bolted to the previous segment's lower chord using splice plates. Positioning is achieved using punches 0.2mm smaller than the bolt hole diameter (26mm hole diameter, 25.8mm punch diameter). Four punches are used for each node plate, and the same applies to the upper chord. Inter-segment connections between diagonal and vertical members are also temporarily bolted using splice plates and punches.

[0043] S8: Overall Linearity Measurement and Adjustment After all six segments were assembled, a total station was used to measure the longitudinal alignment (chord axis), truss height, node diagonals, and pre-camber values ​​within a 72m length. The measurement results showed that the maximum deviation in longitudinal alignment was +3mm / -2mm, the maximum deviation in truss height was +2mm / -1mm, the maximum difference in node diagonals was 3mm, and the pre-camber was 30mm ± 2mm, all meeting the design requirements (longitudinal alignment ± 5mm, truss height ± 3mm, diagonal difference ≤ 5mm). For individual points exceeding the requirements, local fine-tuning was performed using a hydraulic jacking device and jacks.

[0044] S9: Multi-segment, multi-style bevel welding In this embodiment, the connection between the diagonal brace and the node plate employs a multi-segment, multi-style bevel. The specific design is as follows: (1) Beveling type: Upper flange of the diagonal brace (400mm wide, 28mm thick): A single-sided V-groove is cut with a 55° bevel angle, a 3mm blunt edge, and a 4mm root gap. Welding is performed from above, using CO2 gas shielded welding for the root pass and submerged arc welding for the filler and cover pass.

[0045] The lower flange of the diagonal brace is divided into three sections along its length (from one end to the other): the first section (0-300mm from the end) uses a double-sided V-groove, with a 50° bevel angle on the front and a 30° bevel angle on the back, and a 2mm blunt edge; the middle section (300-1000mm) uses a single-sided V-groove with a ceramic gasket, a 60° bevel angle, and a 2mm blunt edge; the third section (1000-1200mm) uses a double-sided V-groove. This segmented design takes into account the stress concentration and welding accessibility differences in the end node plate area of ​​the diagonal brace.

[0046] Diagonal brace web (20mm thick): The weld between the web and the node plate is a full penetration fillet weld without beveling, but a 3mm gap is reserved. Double-sided welding with single-sided forming process is used.

[0047] (2) Welding sequence: Perform in the order of this application: Step 1: Weld the butt weld between the lower flange of the diagonal brace and the lower flange of the node plate (this position is located below in the assembled position, but is made into a flat weld through beveling design). Step 2: Weld the butt weld between the upper flange of the diagonal brace and the upper flange of the node plate; Step 3: Weld the full penetration fillet welds between the web of the vertical member and the top plate of the lower chord and the bottom plate of the upper chord (weld the lower chord side first, then the upper chord side). The web of the vertical member (plate thickness 20mm) and the top plate of the lower chord and the bottom plate of the upper chord are connected by a single-sided V-groove with a groove angle of 50°, a blunt edge of 2mm, and a root gap of 3mm. A ceramic backing is attached to the back, and CO2 gas shielded welding is used for single-sided welding and double-sided forming. Step 4: Weld the full penetration fillet weld between the diagonal brace web and the node plate, using a double-sided asymmetrical bevel (60° bevel angle on the front and 30° bevel angle on the back). After welding the front side, the arc penetration depth is used to achieve automatic back-side forming without the need for root cleaning; or a small carbon arc gouging gun can be used to perform back-side root cleaning from the side gap, with the root cleaning depth controlled within 2mm.

[0048] 3) Welding parameters: CO2 gas shielded welding: current 300A, voltage 28V, welding speed 400mm / min, gas flow rate 20L / min; Submerged arc welding: current 600A, voltage 33V, welding speed 500mm / min.

[0049] After each weld was completed, interlayer cleaning was performed, and VT testing was conducted. The first-pass yield rate of all welds reached 98.5%, with no overhead welding defects.

[0050] S10: Post-welding inspection After each segment was welded, an overall measurement was performed again. The average shrinkage of the girder height was 2.5mm, slightly smaller than the pre-determined 3mm shrinkage, but close to the theoretical value. After removing the punch pins at the bolt joints of the connecting plates, the high-strength bolts could be inserted freely, and the concentricity of the hole group was satisfactory. During the final product delivery and on-site assembly, the segment splicing was successful on the first attempt.

[0051] Figure 1 This is a schematic diagram of the main truss structure involved in this application, including upper chord, lower chord, vertical members and diagonal members, wherein the vertical members and upper and lower chords are of the structure form of insertion and tight welding.

[0052] Figure 2 This is a structural schematic diagram of the hydraulic jacking and beam adjusting device of this application, which includes a lower support system, a jacking system, a limiting device, and a central controller. The support at the bottom of the rod can accurately adjust the spatial posture of the component to ensure that the position of the component meets the requirements.

[0053] Figure 3 This is a schematic diagram of the initial positioning state of the upper chord of this application, showing that the distance between the upper chord and the lower chord is L_li + 500mm. For the truss structure where the diagonal and vertical members are inserted into the upper and lower chords and are difficult to install, a reasonable installation approach is proposed. After initial positioning with a certain displacement, the inserted diagonal and vertical members are installed first, and then the upper chord is adjusted into place by the hydraulic lifting device of this invention.

[0054] Figure 4 This is a schematic diagram of the insertion and installation of the diagonal and vertical members in this application. It addresses the difficulty in assembling the inserted diagonal and vertical members with the upper and lower chords through a tight welding structure, and proposes the timing and steps for installing the diagonal and vertical members.

[0055] Figure 5This is a flowchart illustrating the long-line continuous matching manufacturing process of the multi-segment main truss structure in this application, and a method for continuous matching of linear arched multi-segment main truss segments under stress-free conditions.

[0056] Figure 6 This is a schematic diagram of the multi-segment, multi-style welding bevels in this application, showing the structure of a single-sided V-shaped bevel on the upper flange and a multi-segment transition bevel on the lower flange. This effectively avoids structural overturning, reduces construction difficulty, and ensures structural stability. The designed non-overturning welding butt joint bevel optimizes the welding process, reduces construction difficulty, and ensures weld quality.

[0057] In summary, the steel truss girder assembly construction method proposed in this application can be widely applied to the factory manufacturing of main truss girder segments for various types of large-span steel truss girder bridges that are either fully welded or partially welded. The hydraulic jacking devices, welding bevel types, and long-line jigs required by this method can all be achieved using conventional industrial equipment or through simple processing, without the need for special materials or high-end equipment. This application not only improves manufacturing precision and efficiency, but more importantly, it solves the long-standing safety hazard problem of large truss segment overturning welding that has plagued the industry, demonstrating significant industrial applicability.

[0058] The above embodiments are only used to explain the technical solutions of the present invention and not to limit it. Although the above embodiments have provided specific descriptions of the present invention, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications and equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for assembling and constructing a steel truss girder segment structure, characterized in that, Includes the following steps: S1. Basic unit components for manufacturing steel truss beams, wherein the basic unit components include upper chord segments, lower chord segments, diagonal segments, and vertical segments; S2. Provide a hydraulic jacking and beam adjusting device, which includes a lower support system, a jacking system, a limit device and a central controller, and can realize independent adjustment in three directions: longitudinal, lateral and vertical. S3. Position the first section of the lower chord and level it to make the lower support stable. Place the first section of the upper chord above the lower chord and adjust the upper chord to the initial positioning state using the hydraulic lifting and adjusting beam device. The initial positioning state is that the distance between the upper chord and the lower chord is L_theoretical + ΔH, where L_theoretical is the theoretical design distance and ΔH is the preset offset. The value of ΔH ranges from 300mm to 800mm. S4. In the initial positioning state, insert both ends of the diagonal member segment and / or the vertical member segment into the lower chord node plate and the upper chord node plate respectively, and temporarily fix them after adjusting them to the design angle; S5. The upper chord, which has been inserted with diagonal and / or vertical members, is precisely positioned using a hydraulic jacking and adjusting device. The upper chord is adjusted to a distance of Lli + ΔL between it and the lower chord, where ΔL is the reserved amount for welding shrinkage compensation. The three-dimensional coordinates of the intersection of the chord axis and the node plate are measured using a total station to ensure that the longitudinal, transverse, and vertical alignment dimensions of the upper and lower chords meet the design requirements. S6. The first main truss segment is installed successfully, and the installation and positioning of the subsequent main truss segments will begin. First, the lower chord of the second segment will be installed. The planar position relationship between the second lower chord and the first lower chord will be adjusted to ensure that the longitudinal alignment meets the design requirements. The two lower chords will be fastened together using splicing plates. S7. Repeat step S3 to initially position the upper chord of the second segment; repeat step S4 to install the diagonal and vertical members of the second segment; repeat step S5 to precisely adjust and fix the upper chord of the second segment, and then bolt the two upper chords together and bolt the diagonal members connecting the two segments together using splicing plates. S8. Following step S7, complete multiple main truss segments. Using the long-line method and setting pre-arches according to the manufacturing line shape required by the design, complete the continuous matching and positioning installation of multiple main truss segments. Perform overall line shape measurement on the assembled multi-segment continuous matching assembly, including longitudinal line shape, truss height, and node diagonal. After passing the measurement, proceed to the welding process. S9. Welding between the diagonal / vertical members and the chord node plates is carried out using multi-segment and multi-style welding bevels. The multi-segment and multi-style welding bevels are as follows: in the truss assembly posture, the upper flange of the diagonal or vertical member is set with a single-sided V-shaped bevel, and the lower flange is set with a multi-segment and multi-style transition bevel that combines single-sided V-shaped bevels and double-sided V-shaped bevels.

2. The method for assembling and constructing a steel truss girder segment structure according to claim 1, characterized in that, In step S2, the maximum lifting force of the hydraulic jacking and adjusting beam device is 500KN, the limiting device prevents overturning due to excessive limits, and the central controller is connected to each jacking cylinder and lateral movement cylinder, and adjusts the displacement in each direction in real time through the feedback data of the total station.

3. The method for assembling and constructing a steel truss girder segment structure according to claim 1, characterized in that, In step S2, the hydraulic lifting and adjusting beam device is also equipped with a displacement sensor and an inclination sensor. The displacement sensor is used to monitor the displacement in all directions in real time, and the inclination sensor is used to monitor the spatial attitude angle of the upper chord. All sensor data are transmitted to the central controller for closed-loop control.

4. The method for assembling and constructing a steel truss girder segment structure according to claim 1, characterized in that, In step S3, the preset offset ΔH is set to 500mm.

5. The method for assembling and constructing a steel truss girder segment structure according to claim 1, characterized in that, In step S4, the diagonal bar segment and / or vertical bar segment are pre-rotated by a certain angle before being inserted into the node plate to make them easy to insert. After both ends are inserted into the node plate, they are rotated to the designed angle and temporary supports are set at the bottom.

6. The method for assembling and constructing a steel truss girder segment structure according to claim 1, characterized in that, In step S5, the value range of the reserved welding shrinkage compensation amount ΔL is 0-20mm.

7. The method for assembling and constructing a steel truss girder segment structure according to claim 6, characterized in that, The reserved welding shrinkage compensation amount is set at 10mm.

8. The method for assembling and constructing a steel truss girder segment structure according to claim 1, characterized in that, In step S8, the continuous matching and positioning of the long line method includes: setting a pre-arch according to the manufacturing line shape required by the design, positioning each segment of the main truss with a punch pin 0.2mm smaller than the bolt hole diameter, and then temporarily bolting together with splicing plates.

9. The method for assembling and constructing a steel truss girder segment structure according to claim 1, characterized in that, In step S9, the specific form of the multi-segment, multi-style welding bevel is as follows: in the width direction of the diagonal or vertical bar, the connection between the flange and the web plate adopts an arc transition, the blunt edge of the single-sided V-shaped bevel of the upper flange is 2-4mm, and the bevel angle is 45°-60°; the single-sided V-shaped bevel segment and the double-sided V-shaped bevel segment of the lower flange are alternately set or gradually transitioned according to the length ratio of 1:1-2:

1.

10. The method for assembling and constructing a steel truss girder segment structure according to claim 1, characterized in that, In step S9, the welding is performed in the following order: first, weld the butt weld of the lower wing plate between the diagonal wing plate and the node plate; then weld the butt weld of the upper wing plate; then weld the fillet weld between the vertical web plate and the top plate of the lower chord and the bottom plate of the upper chord; and finally weld the fillet weld between the diagonal web plate and the node plate.

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