Construction method of variable cross-section steel box girder across highway section curve

Abstract

The present application relates to the field of bridge construction method, especially a kind of cross highway section curve variable cross-section steel box girder construction method, which greatly improves the pushing efficiency and reduces the cost under the premise of ensuring structural stability and safety, comprising the following steps: a, steel box girder section division and production;B, steel box girder is transported to the construction site;C, temporary support foundation treatment and temporary support erection;D, erection of bailey beam and steel guard;E, installation of distribution beam and track beam;F, beam transport flat car installation;G, anchor device and pulling power system installation;H, steel box girder section assembly;I, steel box girder pushing installation;J, steel box girder transverse deviation adjustment, and complete a construction stage of steel box girder construction.The present application is especially suitable for cross highway section curve variable cross-section steel box girder construction.

Description

Technical Field

[0001] This invention relates to the field of bridge construction methods, and in particular to a construction method for a curved variable cross-section steel box girder crossing a highway section. Background Technology

[0002] With the continuous increase in urban traffic flow, the construction of existing urban elevated roads is accelerating, and it is common for newly built urban elevated bridges to cross existing highways. Under these complex conditions, the use of steel box girders for the bridge superstructure is a common approach, offering advantages over concrete structures such as flexible segmentation, lighter weight, and easier installation. Steel structures are becoming increasingly novel in form, more complex in construction, and have larger spans. Consequently, the hoisting of large-span steel box girders has become a major challenge, making the selection of appropriate hoisting techniques crucial for their successful installation.

[0003] Existing overpasses often need to cross existing highway sections during construction, involving large spans, small angles with existing highways, narrow sites, tight deadlines, and high requirements for traffic flow and safety. However, existing construction methods are often costly, slow, and inefficient. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a construction method for curved variable cross-section steel box girders that greatly improves the jacking efficiency and reduces the cost while ensuring structural stability and safety.

[0005] The technical solution adopted by this invention to solve its technical problem is: a construction method for curved variable cross-section steel box girders across highway sections, including the following steps: a) Steel box girder segment division and fabrication: The steel box girder is divided into 15 segments along the longitudinal direction, and the segments are numbered sequentially according to the alphabetical order A, B, C, D, E, F, G, H, I, J, K, L, M, N, and O; b) Transportation of steel box girders to the construction site; c) Temporary support foundation treatment and temporary support erection: Temporary supports are set at the bottom of each segment; d) Erecting Bailey beams and steel protective sheds; e) Installing distribution beams and track beams: First, the platform distribution beams are laid, and then the track beams are installed; f) Installation of the beam transport flatbed truck; g) Installation of anchoring devices and traction power system; h) Steel box girder segment assembly: The steel box girder is assembled on-site on a special jig. The linear requirements of the jig are set according to the actual transverse slope, longitudinal slope, and pre-camber of the box girder. Assembly can only proceed after the total station has been used to measure and check for accuracy; The sequence is box girder first, then cantilever beam. The next stage can only be installed after each segment is fully in place. The segment placement is adjusted in the order of horizontal position first, then elevation. i. Steel box girder jacking installation: First stage: The box girder is lifted and hoisted using a crawler crane. The segments of the box girder are numbered A, B, C, and D, a total of four segments, and installed sequentially on the first pier and temporary support. Second stage: The box girder is dragged across the highway section. The segments are numbered E and F, a total of two segments. Third stage: The box girder is hoisted using a crawler crane. The segments are numbered G, H, and I, a total of three segments. Fourth stage: After all the box girders are assembled and installed, the box girders are repaired by bolting and painting, temporary road closures are removed, the steel protective sheds across the highway and the temporary supports in the middle of the road are removed, the equipment and facilities on the road surface are removed, and finally the temporary supports on both sides are removed. j. Adjustment of the lateral deviation of the steel box girder, and completion of one stage of steel box girder construction.

[0006] Furthermore, in step c, jacks are installed between the temporary support and the bottom of each segment to ensure the support is lowered and to adjust the installation elevation of the box girder. Adjusting the elevation using jacks effectively ensures the accuracy and quality of the construction.

[0007] Furthermore, in step h, the position and elevation of the steel box girder are adjusted using jacks. After the elevation adjustment meets the requirements, steel shims and wedges are added. Adding steel shims and wedges ensures that the position of the steel box girder is within the design tolerance range, guaranteeing construction quality.

[0008] Furthermore, in step h, the standard for elevation adjustment is that the difference between the adjusted elevation dimension and the designed elevation dimension shall not exceed 2mm.

[0009] Furthermore, in step i, the first stage uses hoisting to construct the caissons for sections A, B, C, and D; the second stage uses towing to construct the caissons for sections E and F; and the third stage uses hoisting to construct the caissons for sections G, H, and I. This combination of hoisting and towing allows for efficient crossing of the highway during construction, ensuring the safety of the superstructure and high-speed traffic. The entire construction process is simple to operate and effectively reduces safety risks. While ensuring structural stability and safety, it significantly improves the efficiency of the jacking process and reduces costs.

[0010] Furthermore, in step j, by pre-welding and fixing the transverse fine-tuning support on the pier, a jack reaction force is provided during the fine-tuning of the transverse deviation of the steel box girder, thereby realizing the transverse deviation adjustment of the steel box girder.

[0011] The beneficial effects of this invention are as follows: First, the use of a drag-and-pull jacking method for steel box girder installation solves problems such as narrow site conditions, tight schedules, and high requirements for traffic flow and safety. Second, the box girder segments are assembled on a dedicated jig, allowing for good site and space conditions, lower hoisting heights, and more accurate assembly. Third, the drag-and-pull jacking method is not limited by lifting capacity or height, greatly reducing the risks of working at heights, simplifying operation, and minimizing safety risks. Fourth, compared to traditional walking-and-pull jacking methods, the drag-and-pull jacking process allows for continuous construction across multiple work surfaces, resulting in faster construction progress and effectively saving time. This invention is particularly suitable for the construction of curved variable cross-section steel box girders crossing highway sections. Attached Figure Description

[0012] Figure 1 This is a schematic diagram showing that the steel box girder of the present invention is divided into 15 segments, and each stage is marked with a letter.

[0013] Figure 2 This is a schematic diagram of the construction of the A-segment box body according to the present invention.

[0014] Figure 3 This is a schematic diagram of the construction of the B-segment box body according to the present invention.

[0015] Figure 4 This is a construction diagram of the C-segment box and the D-segment box of the present invention.

[0016] Figure 5 This is a construction diagram of the E-segment box and the F-segment box of the present invention.

[0017] Figure 6 This is a construction diagram of the G-segment box, H-segment box and I-segment box of the present invention.

[0018] Figure 7This is a construction diagram of the J-segment box, K-segment box and L-segment box of the present invention.

[0019] Figure 8 This is a schematic diagram illustrating the construction of the M-segment box girder, N-segment box girder, and O-segment box girder of the present invention, as well as the removal of temporary supports on the highway road surface.

[0020] Figure 9 This is a schematic diagram after the temporary supports on both sides of the highway section have been removed according to the present invention.

[0021] The markings in the diagram are: 1. Steel box girder, 2. Expressway section, 3. Crawler crane, 4. First pier, 5. Second pier, 6. Third pier, 7. Fourth pier, 8. Temporary support, 9. Temporary support on the expressway road surface. Detailed Implementation

[0022] The invention will be further described below with reference to the accompanying drawings.

[0023] like Figures 1 to 9 The construction method for curved variable cross-section steel box girders crossing highway sections, as shown, includes the following specific steps:

[0024] a. Steel box girder segment division and fabrication: Based on the characteristics of on-site installation process and transportation conditions, the steel box girder is divided into 15 segments in the longitudinal direction. Each segment is composed of 5 parts in the transverse direction. The segments are connected in a Z-shaped overlap form, and the top, web and bottom are staggered by 250mm respectively.

[0025] b. Transportation of Steel Box Girder to the Construction Site: For the transportation of steel box girders, a section will be transported using an extended vehicle of 15 meters or more. The route will be: National Highway to Tianfu Airport Expressway, then Chengdu-Yibin-Zhaoqing Expressway, then G93 Expressway, and finally National Highway to the construction site. Before transportation, oversized transport permits must be obtained from the transportation department. Transportation is only permitted after approval. During transportation, a constant speed must be maintained, traffic rules must be followed, and traffic accidents must be avoided. The allowable width of the transport road must meet the width of the box girder sections, the road surface must be in good condition, flat, and without a turning radius of less than 50 meters. Specific transportation methods are as follows: 1. During loading, a designated person must supervise the process, count the box numbers and packing numbers, and complete the handover procedures. 2. The transportation sequence of each component segment will follow the installation sequence, with units supplied in complete sets. 3. φ16mm steel cables will be used to securely fix the girder to the transport vehicle, and chain hoists will be used to tighten it to the truck bed. 4. When the steel box girder is placed on the sleepers, the tail of the steel box girder should be higher than the head, and the tail of the steel box girder should not be overhanged too long, and should be controlled within 6m. In order to prevent the steel box girder from moving laterally, connecting plates should be welded between the two sides of the steel box girder and the car body to fix the steel box girder on the car body and prevent it from moving.

[0026] c. Temporary Support Foundation Treatment and Erection: To ensure the accuracy of the elevation during hoisting and the stability of the bridge during hoisting, temporary supports were erected at each segment placement location to support the weight of the steel box girder. Temporary supports were arranged at temporary longitudinal segment nodes, simultaneously supporting the weight of the steel box girders on both sides. The piers were used to temporarily fix the box girder of the support segment. The temporary steel supports used Φ400*10 steel pipes as portal columns, with 30# I-beams used to construct the installation platform. Φ250 steel pipes were used as supports and tie rods, mutually supporting each other. A total of 13 sets of temporary supports were required. A working platform was set up 1.8 meters below the bottom of the upper box girder, with 18mm engineering formwork laid on the platform. Fireproof safety netting was installed around the platform, and safety protection measures were implemented to ensure the safety of pedestrians and vehicles during construction. M24 anchor bolts were used to connect the steel columns to the foundation. Each steel column had four anchor bolts, and each support had 10 steel columns. Through mutual support and ties, construction safety and the overall stability of the box girder were ensured. To ensure the smooth lowering of the support frame and the adjustment of the box girder installation elevation, four 100t jacks were installed at the connection point between the box girder and the supports, and four 30t jacks were installed on top of the temporary support frame. The elevation of each steel support was adjusted according to the actual site conditions.

[0027] d. Erection of Bailey Bridges and Steel Shelter: I. Erection of the Bailey Bridge Platform: The Bailey Bridge platform is 80 meters long and 20 meters wide, consisting of 13 Bailey bridge sections forming a truss. The spacing between two Bailey bridge sections is 1 meter, and a total of 9 sets of Bailey bridge trusses are erected to form the Bailey Bridge platform. II. Laying of Patterned Steel Plates: The patterned steel plates are 2mm thick. To ensure complete coverage of the Bailey Bridge platform, plates of the same size as the platform are selected, measuring 80 meters long and 12 meters wide.

[0028] e. Installation of Distribution Beams and Track Beams: I. Platform Distribution Beam Laying: The platform distribution beams are laid using 400H-beams. One 400H-beam is laid every 3.5 meters along the entire checkered steel plate, for a total of 23 beams. II. Track Beam Installation: After the platform distribution beams are laid, three track beams are erected on top using 600H-beams. To ensure the stability of the track beams, a 200H-beam is used to connect and fix every 5 meters between every two track beams. There are 16 beams per row, for a total of 32 beams in two rows.

[0029] f. Installation of the beam transport flatbed truck: The beam transport trolley adopts a six-wheel trolley with a maximum load capacity of 200t.

[0030] g. Installation of Anchoring Device and Towing Power System: The towing equipment is located at the second pier 5. After the equipment support is installed, a winch platform will be erected, and two winches will be installed. The winch platform will be reinforced. To ensure safety and stability during the towing process, the towing equipment will be reinforced. Additionally, a winch platform will be erected next to the first pier 4, with one end of a φ22 steel cable fixed to the platform and the other end fixed to the towing equipment to ensure its stability.

[0031] h. Steel Box Girder Segment Assembly: The steel box girders are assembled on-site on a specialized jig. The jig's linearity is set according to the actual transverse slope, longitudinal slope, and pre-camber of the box girder. Assembly can only proceed after the jig has been measured and checked with a total station. The assembly sequence is box girder first, then cantilever beam. The next stage can only be installed after each segment is fully in place. Segment positioning is adjusted in the order of horizontal position first, then elevation. To prevent lateral displacement of the box girder, limiting plates are welded to the platforms on both sides and ends of the girder to adjust the left and right position and fix the girder. The position and elevation of the steel box girder are adjusted using jacks. Precise measurements are required during elevation adjustment. After the requirements are met, steel shims and wedges are added. Shims are required at each partition. After assembly, the overall dimensions and position are measured and inspected. The splicing accuracy and overall dimensions must meet the design requirements, and the height difference must not exceed 2mm.

[0032] i. Installation of steel box girder by jacking:

[0033] Phase 1: Using crawler cranes, the equipment was lifted from the first pier 4 to the second pier 5, and from the second pier 5 to the temporary support 8 points on the side of the guardrail of the highway section 2. The lifting box body consisted of sections A, B, C and D.

[0034] The second phase, which involves crossing section 2 of the expressway, uses towing equipment for installation. The towing box consists of two sections, E and F. Construction begins with closing the road to erect a Bailey bridge across the left lane of the expressway. After erection, the same construction is carried out on the right lane. Once both sides are erected, the equipment is inspected, the facilities are reinforced, and anchoring is done to facilitate the fixing and stress distribution of the winch. Then, steel supports are erected, and the towing equipment is positioned towards the fourth pier 7 and the first pier 4 on both sides. After the erection was completed, half of the highway was reopened. Then, the reinforcement and pulling equipment for the second pier 5 was installed and tested. The first pier 4 was secured to its foundation using φ22 steel cables and pulled to the top of the second pier 5 for tensioning reinforcement to ensure stability and balanced stress during the pulling process. After all equipment was installed and tested, the installation of the box girder across the highway at the third pier 6 began. During the track assembly of section E, after welding, the box girder was pulled to the installation point for the first pulling of the butt weld of section D. After the first section was pulled and welded together, reinforcement supports were installed on the Bailey bridge, and the flatbed trolley was gradually removed. Then, the construction of the second section began. The first butt weld was completed between sections D and E, and the second between sections E and F.

[0035] After the E-section and F-section box girder are installed, the third stage of construction will be carried out. A crawler crane will be used to lift the temporary support 8 to the fourth pier column 7. The box girder to be lifted consists of three sections: G-section, H-section and I-section.

[0036] The fourth stage involves dismantling the equipment and facilities. After all the enclosures are assembled and installed, work such as patching and repainting is done on the enclosures. Then, the temporary road closures, the steel protective canopy crossing the highway, and the temporary supports in the middle of the road are dismantled, along with the equipment and facilities on the road surface. Finally, the temporary supports on both sides are removed.

[0037] j. Lateral Deviation Adjustment of Steel Box Girder: The steel box girder has been initially positioned according to the design during the towing process, but lateral deviation will occur during construction. Lateral fine-tuning supports have been welded and fixed during the installation of each temporary support group. These supports mainly facilitate the provision of jack reaction force during fine-tuning and also play a certain limiting role when the steel box girder is towed and deviated. A 30t hydraulic jack is used to correct the lateral deviation problem.

Claims

1. A construction method for a curved variable cross-section steel box girder across a highway section, characterized in that, It comprises the following steps: a. Steel box girder segment division and production: the steel box girder (1) is divided into 15 segments in sequence along the longitudinal direction, and the segment numbers are marked in sequence according to the alphabetical order A, B, C, D, E, F, G, H, I, J, K, L, M, N and O; b. Steel box girder transportation to the construction site; c. Temporary support foundation treatment and temporary support erection: temporary supports are arranged at the bottom of each segment; d. Erection of Bailey beams and steel protective sheds; e. Installation of distribution beams and track beams: first, platform distribution beams are laid, and then track beams are installed; f. Installation of beam transport flat cars; g. Installation of anchoring devices and pulling power systems; h. Steel box girder segment assembly: steel box girder on-site assembly is carried out on a special jig, the linear requirements of the jig are set according to the actual transverse slope, longitudinal slope and pre-camber of the box girder, and full station instrument measurement is used to check that there is no error before assembly can be carried out; the assembly sequence is box body first and cantilever beam second, and each segment can be installed only after it is completely in place; segment positioning is adjusted in the order of plane position first and elevation second; i. Steel box girder jacking installation: First stage: the box body is lifted and installed by using a crawler crane (3), the segment numbers of the lifted and installed box body are A, B, C and D, a total of four segments, and they are installed on the first pier column (4) and the temporary support (8) in sequence; Second stage: across the highway section (2), the segment numbers of the pulled box body are E and F, a total of two segments; Third stage: the box body is lifted by using the crawler crane (3), the segment numbers of the box body are G, H and I, a total of three segments; Fourth stage: after all the box bodies are completely connected and installed, the box body is supplemented with bolts and paint, the temporary road closure is removed, the steel protective shed across the highway and the temporary support in the middle of the road are removed, the equipment and facilities on the road are removed, and finally the temporary supports on both sides are removed; j. Steel box girder transverse deviation adjustment and completion of steel box girder construction of one construction stage.

2. The construction method of the curved variable cross-section steel box girder across the expressway section according to claim 1, characterized in that: In step c, jacks are arranged between the temporary supports and the bottom of each segment to ensure that the supports are removed and the installation elevation of the box girder is adjusted.

3. The construction method of the curved variable cross-section steel box girder across the expressway section according to claim 2, characterized in that: In step h, the position and elevation of the steel box girder are adjusted by using jacks, and after the elevation adjustment meets the requirements, steel shims and steel wedges are added.

4. The construction method of the curved variable cross-section steel box girder across the expressway section according to claim 3, characterized in that: In step h, the standard for elevation adjustment is that the height difference between the adjusted elevation size and the designed elevation size is not more than 2 mm.

5. The method for constructing a curved variable cross-section steel box girder across a highway section according to any one of claims 1 to 4, characterized in that: In step i, the first stage uses lifting to realize the construction of A, B, C and D segments; the second stage uses pulling to realize the construction of E and F segments; and the third stage uses lifting to realize the construction of G, H and I segments.

6. The method for constructing a curved variable cross-section steel box girder across a highway section according to any one of claims 1 to 4, characterized in that: In step j, by using the transverse fine adjustment supports that are pre-welded and fixed on the pier column, a counterforce of the jacks is provided during the fine adjustment of the transverse deviation of the steel box girder, so as to realize the transverse deviation adjustment of the steel box girder.

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