Prefabricated CFST arch bridge arch rib rapid construction method

Abstract

The application provides a quick construction method of an assembled CFST arch bridge arch rib, and belongs to the technical field of quick construction of arch bridge arch ribs. The method comprises the following steps: step 1, manufacturing and transporting the steel structure of the arch bridge arch rib; step 2, setting a large temporary structure of the arch bridge arch rib; and step 3, assembling the cantilever of the arch bridge arch rib. The application adopts the concept of "factory manufacturing, standardized production and modular installation", and systematically prepares from the aspects of standardized design of the large temporary structure, assembled installation, steel structure processing and manufacturing and transportation, so as to master the key influencing links, realize high-precision and quick cantilever assembly of the arch rib, effectively reduce the installation risk of the arch rib, guarantee the construction period of the key control project, and provide a reference for similar bridge construction.

Description

Technical Field

[0001] This invention relates to the field of prefabricated CFST arch bridges, and more particularly to a rapid construction method for the arch ribs of prefabricated CFST arch bridges. Background Technology

[0002] More and more bridges are developing towards longer spans, prefabrication, and assembly. Among them, CFST arch bridges, due to their advantages such as high load-bearing capacity, large span capacity, good economic performance, and low maintenance, are increasingly being promoted in canyons, rivers, and lakes. Traditionally, arch rib segments are joined by flanges, and wind bracing is done by welding. To achieve rapid assembly and construction, reduce on-site high-altitude welding, and improve project quality, wind bracing between spans is gradually adopting high-strength bolted connections at nodes. Fully bolted cantilever assembly places higher demands on precision. How to achieve high-precision installation of fully bolted arch ribs is a technical challenge in the construction of steel pipe arch ribs.

[0003] With the continuous development of long-span CSFT arch bridges, the construction methods for arch ribs are gradually moving towards factory production, standardization, and prefabrication. Bridge construction is primarily completed in the factory, with only necessary installation procedures performed on-site. This ensures precision and quality while also improving the efficiency of on-site cantilever construction. Rapid arch rib construction requires key measures regarding steel structure processing, cable hoisting systems, cable-stayed systems, and handling adverse construction environments. Therefore, based on the construction schedule, a rapid construction method for prefabricated CSFT arch bridge arch ribs needs to be designed. Summary of the Invention

[0004] The purpose of this invention is to provide a rapid construction method for the arch ribs of prefabricated CFST arch bridges, thereby solving existing technical problems.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A rapid construction method for the arch ribs of prefabricated CFST arch bridges, the method comprising the following steps: Step 1: Manufacturing and transporting the steel structure of the arch ribs of the arch bridge; Step 2: Set up the temporary structures for the arch ribs of the arch bridge; Step 3: Assemble the cantilever of the arch rib of the arch bridge.

[0006] Furthermore, the specific process of step 1 is as follows: The arch rib fabrication employs a double-pronged process of horizontal and vertical assembly. During horizontal assembly, to control the fabrication line shape of the arch rib, the chord difference in the chord extension is controlled within 5mm. During vertical assembly, the lateral bend is controlled within 10mm, the axial deviation is within 8mm, and the segment length deviation is controlled within 5mm. To control welding shrinkage deformation, independent supports are installed on the gusset plate, and free expansion and contraction ends are reserved for welding. The amount of shrinkage is determined in advance through experiments for compensation. To ensure a tight fit between the flanges, the flange surfaces are machine-milled. The two flange surfaces are temporarily tightened together with bolts beforehand. During horizontal assembly, one end of the flange stiffening plate is fully welded, while the other end is left unwelded. Welding is carried out after the vertical assembly alignment is approved to ensure a tight fit between the flanges before the arch rib is hoisted. After the arch rib assembly was completed and accepted, a 3D laser scanner was used to scan the entire process. The 3D laser scanner has an accuracy of 2mm. The scanned model was compared with the manufacturing BIM model to analyze the component processing accuracy in 3D. After the steel structure manufacturing is accepted, the entire segment is treated with anti-corrosion and painting. Then, the entire segment is hoisted onto the ship and transported to the bridge site as a whole. After the segment is transported to the bridge site, it is erected and assembled according to the completed bridge state, and the wind bracing is matched and installed.

[0007] Furthermore, the specific process of step 2 is as follows: the bridge arch rib adopts a supportless installation process of cable hoisting and inclined suspension. The cable hoisting system is the equipment for bridge installation, and construction efficiency and hoisting occupy the critical path. In the design of the cable hoisting system, two sets of independently operating main cranes are set up. The maximum tonnage of a single main crane is 160 tons, and a single set can complete the hoisting of the arch rib segment. The cable tower is designed with a portal truss structure composed of 630×12mm steel pipes and steel sections. The cable tower adopts a prefabricated design. The main pipes are connected by flanges, and the pipe connecting rods and temporary protection are all connected by bolts. The components are manufactured in the factory and quickly assembled on site using tower cranes. Construction efficiency and safety are effectively guaranteed. When designing the cable-stayed tower, the tower and cable tower adopt the same design concept. The anchor box, anchor seat, anchor box and operating platform adopt standardized design, and the components are connected by pins and bolts. Furthermore, in step 3, the cantilever assembly of the arch rib is the stage with the highest safety risk. During the assembly process, factors that restrict the installation efficiency of the arch rib include ship positioning, temperature affecting the fine-tuning and positioning of the arch rib, installation, pre-tensioning, and tensioning of the back bracing, installation of the inter-bracing wind brace, welding of the segmental cladding plates, and connection of the high-strength bolts. Then, the timing of continuous hoisting of the arch ribs is determined. According to industry requirements, before installation, sufficient arch rib segments to be installed should be ensured. At least one arch rib should be installed or no less than 3 / 4 of the total number of segments to be installed on the bridge should be stored before installation. The purpose is to avoid the increased risks of waiting for arch rib segments in a large cantilever state. During implementation, the transportation and processing conditions vary for each project. The supply of finished arch rib segments is affected by factors such as steel structure processing efficiency, steel structure transportation and transshipment, and weather. Before hoisting begins, a comprehensive analysis of the arch rib segment supply is necessary to ensure a continuous supply. During this period, precise adjustment and installation of segment #1 can be carried out to improve the installation accuracy of the first segment and lay the foundation for subsequent hoisting. The vessel is positioned, and the segment is launched between 5 and 6 a.m. The hoisting operation is carried out using a method that allows the construction vessel to be positioned quickly without affecting navigation. Compared with the traditional transportation positioning method, which requires positioning one day in advance to meet the construction schedule requirements, this method only takes 20 minutes, saving the construction period. Each hoisting operation can save a day of positioning time. The installation, pre-tightening, and tensioning of the backing cable can be carried out in advance. The backing cable can be directly anchored, and the backing cable can be temporarily anchored to the installed segment. After the high bolts of the arch rib flange are tightened, the backing cable P anchor is installed. In order to avoid the backing cable steel strand bundles from tangling and twisting, and the steel strands not being able to bear the force evenly, the backing cable steel strands are threaded individually to ensure that each steel strand is parallel. After the buckle is installed, an intelligent continuous pre-tightening jack is used to automatically pre-tighten the buckle. The pre-tightening jack cylinder adopts a honeycomb design, with each single pre-tightening jack corresponding to pre-tightening one steel strand. According to the principle of communicating vessels, the pressure is equal everywhere in a closed container, which can ensure that each single pre-tightening jack outputs an equal pre-tightening force. That is, after the steel strand is pre-tightened, the force is uniform and consistent. The pre-tightening efficiency of the pre-tightening equipment is 4 times higher than that of ordinary single-strand pre-tightening. The main constraint on the efficiency of plate wrapping and high bolt construction is the labor input. The main processes of plate wrapping construction are: assembly, welding, weld inspection, and painting. The requirements for circumferential welds are high. During the welding process, rain and wind protection measures should be taken to ensure the welding quality. Plate wrapping welding should be organized according to the flow operation, and the number of delays should be controlled within 2 sections. The main processes for high-strength bolt connection include: initial tightening, final tightening, inspection, and bolt sealing. The tightening time for a single node bolt group is 2 hours. The factors that limit work efficiency are the number and turnover efficiency of the node safety operation platform. For the arch rib closure, an internal instantaneous closure joint is used. After the arch rib segment is hoisted, the arch rib elevation and alignment are adjusted. Holes are drilled on-site and high-strength bolts are used to connect the joint I-beams. The butt sleeves are welded in time to complete the full bridge closure of the arch rib. Data monitoring of the arch rib alignment, temperature, and cable tension is conducted 3-7 days in advance. When closing, the arch rib closure can begin after the alignment and temperature have stabilized. During closure, each closure buckle is equipped with sufficient personnel for drilling, bolting, assembly, and welding. Considering the possibility that the design temperature cannot be reached during closure, the arch rib alignment under different temperature conditions needs to be calculated in advance to complete the system conversion of the arch rib in the shortest possible time.

[0008] Furthermore, in step 3, the steel pipe arch head segment needs to be constructed and installed in advance. The specific process is as follows: Step 3.1.1: Installation of the arch seat embedded section. The arch seat embedded section structure consists of 4 sleeves and 1 set of hinge seats. The bottom is connected as a whole by a steel connecting frame. The positions of the left and right embedded section chord support frames are accurately laid out according to the design drawings. The control point is the hinge groove embedded plate. Due to processing errors, the center point of the hinge shaft needs to be used as the control point. The design coordinates of the hinge shaft are used for accurate layout. The control is within 3mm and the through-axis is used for verification. Step 3.1.2: Set up pre-embedded support steel sections along the layered casting line of the arch seat. The support steel sections are double-sectioned HN200×100mm steel sections, and the support steel sections are welded to the pre-embedded steel plates in the arch seat. Step 3.1.3: Before installing the supporting steel, re-measure and adjust the embedded steel plate to ensure that the top surface of the supporting steel is on the same plane, so as to ensure that each supporting steel is in close contact with the bottom surface of the positioning steel bracket. Adjust the elevation of the embedded steel plate by filling the steel plate. Step 3.1.4: After the supporting steel is installed, mark the position of the positioning steel bracket on its top surface. Use cable hoisting and manual assistance to install the left chord support steel bracket, the right chord support steel bracket and the intermediate connecting frame in sequence. During hoisting, place the positioning steel bracket according to the marked position on the top surface of the supporting steel. After placing it in place, connect the bolts between the brackets to form a whole, thereby completing the preliminary positioning of the embedded section. Step 3.1.5: After the positioning steel bracket is formed as a whole, a three-way jack is set below it to adjust its position and elevation relative to the arch seat. After the first segment is accurately positioned, the three-way jack is used to finely adjust the pre-embedded section to match the first segment. Step 3.2.1: First segment support installation. Design the first segment positioning support according to the structural form and position of the first segment. The basic principle is that the axis position of the support point of the first segment support is consistent with the first segment chord tube in the installation posture, and the elevation position is 5-10cm lower than the first segment chord tube. Sufficient adjustment space is reserved for the three-way jack. At the same time, attention should be paid to the stress calculation of the positioning support, and measures such as adding lateral support should be taken to ensure the overall stability of the support after being stressed. Step 3.2.2: Check the bearing capacity of the support foundation. If the bearing capacity does not meet the requirements, the foundation should be treated in advance. After the foundation is accepted, the support should be laid out and positioned according to the support design drawings. Step 3.2.3: Construct the pier foundation according to the layout position. The top surface of the foundation should be leveled, and steel plates should be pre-embedded on the top surface of the foundation as components to fix the steel pipe columns. Step 3.2.4: Using a truck crane, install the steel pipe columns, inter-column connecting rods, column top distribution beams, and chord pipe supports in sequence, controlling the support elevation according to the design drawings to ensure the adjustment space of the first section; Step 3.3.1: Segment unloading and inspection. According to the steel structure manufacturing precision requirements and pre-assembly requirements, relevant units are organized to inspect the steel structure manufacturing and vertical assembly, and check the key indicators of the vertical assembly segments, such as elevation, lateral bending, verticality, relative height difference of butt joints, diagonal deviation of inner chord pipes, and flange gap between segments. Step 3.3.2: Set up clearly marked measuring points 1.2m at the front and rear ends of the upper and lower chords of the first segment, and collect the measuring point data. After the assembly is accepted, the measuring point data is used as the target value for installation in the bridge site area after coordinate transformation. Step 3.3.3: After the first section is assembled and accepted and all relevant control point data is collected, it is unloaded and transported. Before transport, the processing and welding quality of the temporary structures of the operating platform, lifting points, and fastening points, as well as the matching of the anchor box and fastening points, should be checked. Step 3.4.1: Segment loading and transportation. Before the ship is transported, relevant departments are contacted and personnel are arranged to close the navigation channel. The ship is positioned according to the segment hoisting position and the cable crane lowering position to ensure that the cable crane can lift vertically and that the component placement position is consistent with the projection of the main arch rib axis. After hoisting, it can be directly transferred to the installation position without the need for rotation operation. Step 3.4.2: Before loading, the transport vessel is moored in the steel structure assembly yard dock with its bow facing outward. The guy ropes on the stern deck are connected to the pre-set mooring bollards on the shore. The guy ropes on the stern are connected to the bollards to fix one end of the cargo ship. The guy ropes on the bow are connected to the mooring points reserved on the steel cylinder piles of the trestle in the river channel. Then the binding ropes of the fixed components are unlocked, the first section is unloaded, and the gantry crane is used to lift it onto the platform of the transport vessel. Step 3.4.3: Workers use the reinforced fixing brackets and limit blocks in the cabin to temporarily fix the components, and use steel wire ropes to wrap them horizontally and vertically respectively and tighten them with a hand hoist. At the same time, a fixing fixture is set at the bottom to fix the lower chord tube to the bottom of the cabin, and the sides are fixed and constrained with steel sections to prevent lateral slippage. Step 3.4.4: After confirming the stability of the segment placement and the reliability of the fixing measures, release the gantry crane hook and the ship's fixing guy ropes, drive the ship out of the pier, sail to the lifting area directly below the cable crane, lower the cable crane's lowering point to provide the most direct position for the ship's positioning, and anchor for positioning; Step 3.5.1: Segment lifting and installation. Before lifting, check the structural operation status of the cable crane and each subsystem again to ensure that the cable crane can be used normally and safely. Place three-way jacks at the support points of the support in advance to prepare for the adjustment of the first segment. Step 3.5.2: After the transport vessel is anchored and positioned, the downstream main crane of the cable crane is lowered, and workers board the ship to install the shackles in sequence at the designated lifting lugs and conduct inspections. After all components are connected, the binding and fixing steel cables are released, and personnel leave the deck. The cable crane then carries out the lifting operation. After the section is completely lifted out of the ship's hold, the transport vessel weighs anchor and sails away from the lifting area. Step 3.5.3: When the first segment is hoisted into the air, adjust the arch seat side lifting point to the low end and the mid-span side lifting point to the high end. Adjust the segment's attitude and inclination angle to roughly conform to the completed bridge attitude. Slowly approach the first segment support. After hoisting into place, observe the segment's inclination angle deviation. Adjust the height difference between the front and rear lifting points to meet the initial vertical position requirements of the segment. Place the arch foot end hinge shaft inside the hinge seat and make it closely fit the hinge seat. Slowly place the entire segment on the support. Step 3.5.4: After the first segment is initially positioned, the cable crane hook is gradually unloaded. During the process, pay attention to checking the overall stability of the first segment and the support. If necessary, add stability measures to ensure that the segment does not overturn during the fine adjustment of the three-way jack. Step 3.5.5: After confirming that the position is stable, adjust the three-way jacks at the support point of the support frame, and at the same time use a high-precision total station to measure and position, gradually achieve the fine adjustment of the first section. Step 3.5.6: Once all measurement and control data of the first segment meet the requirements, reinforce it in a timely manner. Fill the gap between the first segment and the support with spot welding, weld the axis limit plate at the hinge position, and pull the lateral guy ropes to ensure that the tension end of the guy rope is firm and does not shift, and ensure that the segment's posture remains unchanged. Step 3.6.1: Wind brace installation, (1) After the first section of the left and right spans is installed, the wind brace is installed. The wind brace between the sections is hoisted by cable crane working crane. It is hoisted to the front end of the installation position, and the wind brace posture is adjusted. After the posture is adjusted to the right position, the wind brace is pulled by hand hoist so that its end point is embedded in the node plate. The node plate and the connecting plate are gradually aligned and the punch nails are driven in and the temporary bolts are tightened to achieve the precise alignment of the wind brace. Step 3.6.2: After positioning, quickly install the node bolts and tighten them symmetrically. First, perform initial tightening on the high-strength bolts at the nodes. The initial tightening torque is 50% of the final tightening torque. After the initial tightening, perform final tightening according to the construction final tightening torque value. Initial tightening and final tightening should be completed within one day. The tightening quality of the high-strength bolts should be inspected using the torque method according to the specifications. The torque check should be completed within 1 hour and 24 hours after the final tightening. Step 3.7.1: Segment matching and positioning adjustment. After the first segment and wind brace are installed, use jacks set under the support frame to precisely adjust the absolute position of the support frame so that it can match the first segment, and make fine adjustments to the position of local members. Step 3.7.2: When adjusting the three-way jacks, since the positioning support is adjusted in a spatial posture, the three directions affect each other. Therefore, the three-way jacks should be adjusted in coordination to gradually approach the position that matches the first section. The misalignment of the chord tube should not exceed 2mm, and the hinge shaft and hinge groove should be in close contact. If some components cannot be matched, they should be adjusted one by one. First, adjust the transverse bridge position, then adjust the longitudinal bridge position and elevation position. Since the longitudinal bridge position and elevation have a great influence on each other, the adjustment needs to be carried out in multiple rounds. In each round, the stroke of each jack should be controlled within 5mm. Step 3.7.3: After the adjustment is completed, fill the space between the supporting steel and the positioning steel bracket with steel plates to make the two parts fit tightly. Then re-measure the position of the segment chord and hinge seat. After meeting the design requirements, weld the supporting steel, filling steel plate and bottom of the positioning steel bracket together to prevent the positioning steel bracket from shifting when pouring concrete. Step 3.7.4: After welding is completed, the three-way jack is returned to its original position and withdrawn. Construction of the pre-embedded section of the arch seat reinforcement, formwork, and concrete is then carried out. During the remaining construction, the position of the segment chord and hinge seat must be continuously monitored. If any movement occurs, construction should be stopped immediately and adjustments made. In particular, it is strictly forbidden to touch the positioning steel support during concrete pouring. The present invention, by adopting the above-described technical solution, has the following beneficial effects: (1) This invention adopts the concept of "factory manufacturing, standardized production and modular installation". It systematically prepares for the standardized design of temporary structures, prefabricated installation, steel structure processing and manufacturing, and transportation. It grasps the key influencing links, realizes high-precision and rapid cantilever assembly of arch ribs, effectively reduces the installation risk of arch ribs, and ensures the construction period of key control projects, providing a reference for the construction of similar bridges. (2) The fine-tuning construction technology of the first segment has successfully achieved high-precision installation of the first segment and in-situ matching between the first segment and the pre-embedded segment, realizing technological progress, promoting the innovation of arch bridge construction technology, and providing new technical support for the development of steel-concrete arch bridges towards larger spans and fully bolted structures. Attached Figure Description

[0009] Figure 1 This is a statistical chart of the efficiency of the vertical assembly wheel in this invention. Figure 2 This is a statistical chart of the efficiency of the vertical assembly wheel in this invention; Figure 3 This is a statistical chart of the efficiency of the assembly process in this invention; Figure 4 This is a diagram analyzing the influencing factors of the arch rib hoisting process in this invention; Figure 5 This is a statistical chart of the efficiency of arch rib hoisting in this invention. Detailed Implementation

[0010] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are merely to provide the reader with a thorough understanding of one or more aspects of the present invention, and these aspects of the invention can be implemented even without these specific details.

[0011] like Figure 2-5 As shown, taking the Wujiang Grand Bridge as an example, the main bridge is a 504m upper-bearing CFST arch bridge (the largest span arch bridge of its kind under construction), a key control project of the entire Deyu Expressway in Guizhou. The arch ring consists of 60 segments, with a maximum lifting weight of 157 tons. It features an innovative integrated steel pipe arch with fully bolted assembly design. The arch rib segments range in height from 11.4m to 8.4m, width from 3.9m, and length from 20m. The arch rib segments are connected by internal flanges, and the wind braces between the left and right spans are connected by high-bolt joints. The bridge steel components are fabricated in the steel structure processing plant, and large components are transported to the construction site via the Wujiang waterway. After vertical assembly, the arch rib segments are installed at high altitude via a second launching into the water. The critical path for the rapid assembly of the arch ribs is: cable hoisting system → steel structure processing and transportation → fastening system → cantilever assembly of the arch ribs. Step 1: Steel structure manufacturing and transportation, such as Figure 1 As shown: The bridge spans the Wujiang River waterway, located in a typical karst hilly area of ​​Guizhou Province, where land transportation is extremely inconvenient, making the transport of large steel structures impossible. Therefore, during the design phase, factors such as water level variations in the Wujiang River waterway, lock dimensions, vessel capacity, and transport procedures were considered in advance, ultimately determining the maximum transport dimensions of the components to be 10.8 × 56 × 9.8 m. To enable factory manufacturing and large-segment transport, the arch rib height was optimized according to these transport dimensions.

[0012] To achieve a 3mm precision in the fully bolted arch ribs, a double-assembly process of horizontal and vertical splicing was adopted for arch rib processing. In-plant processing followed the stress-free alignment provided by monitoring systems. The chord extensions employed a "straight instead of curved" process, and the truss sections and segments were manufactured using a "5+1" matching method. Key aspects of the horizontal splicing process included: precision control of plate units, quality control of rolled pipes, control of chord extensions, control of truss horizontal splicing, and control of arch rib assembly. After acceptance, the entire segment underwent anti-corrosion treatment and painting, and was then hoisted onto a ship for transport to the bridge site.

[0013] After the bridge segments are transported to the bridge site, they are erected and assembled as if they were already in the bridge's completed state, and the wind braces are matched and installed. Key control points during the erection process include: segment arrival inspection, arch rib formwork control, wind brace matching control, flange tightness control, and erection alignment control. The entire bridge erection is carried out in four rounds: the first round is 3+1 (three segments plus one workday), and the following three rounds are 4+1 (four segments plus one workday), with an average assembly time of 25-30 days per round.

[0014] After the arch ribs are assembled, a 3D laser scanner is used to scan the upright assembly posture. The scanned model and the modeling model are simulated and analyzed to strictly control the 3D accuracy of the arch rib processing. At the same time, the upright assembly scanned model is simulated with the on-site hoisting model to predict potential problems in the cantilever assembly and take measures to deal with them in advance.

[0015] Step 2: Setting up temporary structures The bridge arch ribs are installed using a supportless installation process of "cable hoisting + inclined cable fastening". The cable hoisting system is the main equipment for the bridge installation, and its construction efficiency and the hoisting of the arch ribs occupy the critical path, which is the key research direction for improving the efficiency.

[0016] To enable rapid hoisting of the arch ribs, the cable hoisting system is designed with two independently operating main cranes. Each main crane has a maximum tonnage of 160 tons and can complete the hoisting of the arch rib segments with a single crane. Compared with traditional cable hoists, this reduces the number of lateral movements by 30 and saves approximately 30-45 days of construction time.

[0017] The cable tower is designed with a portal truss structure composed of 630×12mm steel pipes and structural steel. To enable rapid assembly of the cable tower, a prefabricated design is adopted. The main pipes are connected by flanges, and the connecting rods and temporary protection between pipes are all connected by bolts. The components are manufactured in the factory and quickly assembled on site using a tower crane, which effectively ensures both construction efficiency and safety.

[0018] When designing the cable-stayed tower, the tower and cable tower adopt the same design concept. The anchor box, anchor seat, anchor box and operating platform adopt standardized design. The components are mainly connected by pins and bolts.

[0019] Step 3: Assemble the arch rib cantilever The cantilever assembly of the arch rib is the stage with the highest safety risks. During the assembly process, factors that restrict the efficiency of arch rib installation include: ship positioning, temperature affecting the fine-tuning and positioning of the arch rib, installation, pre-tensioning, and tensioning of the back bracing, installation of inter-spandrel wind braces, welding of segmental cladding plates, and connection of high-strength bolts, etc., the degree of their impact is as follows: Figure 4 As shown: Determining the timing of continuous hoisting of arch ribs According to industry requirements, sufficient arch rib segments should be ensured before installation. Generally, at least one arch rib should be installed or no less than 3 / 4 of the total number of segments to be installed on the bridge should be stored before installation. The purpose is to avoid the increased risks caused by waiting for arch rib segments in the large cantilever state.

[0020] During implementation, the transportation and processing conditions vary for each project. The supply of finished arch rib segments is affected by factors such as steel structure processing efficiency, steel structure transportation and transshipment, and weather. Before hoisting begins, a comprehensive analysis of the arch rib segment supply is necessary to ensure a continuous supply. During this period, precise adjustment and installation of segment #1 can be carried out to improve the installation accuracy of the first segment and lay the foundation for subsequent hoisting.

[0021] Rapid ship positioning The segmental launch should be carried out between 5 and 6 a.m. Using construction vessels for rapid positioning without affecting navigation, the hoisting operation can be carried out. Compared with the traditional transportation positioning method, which requires positioning one day in advance to meet the construction schedule requirements, this method only takes 20 minutes, which greatly saves the construction period. Each hoisting operation can save a day of positioning time.

[0022] Installation, pre-tensioning and tensioning of back braces To ensure rapid installation of the arch rib, the back-cable construction process can be carried out in advance, and the back-cables can be directly anchored. The back-cables are temporarily anchored to the installed segment, and the P-anchors of the back-cables are installed after the high bolts of the arch rib flange are tightened. To avoid the back-cable steel strand bundles from tangling and twisting, which would prevent the steel strands from being evenly stressed, the back-cable steel strands are threaded individually to ensure that the steel strands are parallel.

[0023] After the cable is installed, intelligent continuous pre-tightening jacks are used to automatically pre-tighten the cable. The pre-tightening jack cylinders adopt a honeycomb design, with each individual pre-tightening jack corresponding to one steel strand. Based on the principle of communicating vessels, the pressure is equal everywhere in a closed container, thus ensuring that each individual pre-tightening jack outputs an equal pre-tightening force, meaning that the steel strand is uniformly stressed after pre-tightening. This newly developed pre-tightening equipment improves pre-tightening efficiency by 4 times compared to ordinary single-strand pre-tightening.

[0024] Arch rib positioning fine adjustment After the arch rib is hoisted to its installation position, the flange bolts are tightened to ensure a tight fit, completing the tangential assembly of the arch rib and verifying its axial deviation. Tensioning is then performed after the back cable is pre-tightened, and the cable hoist is released from load when tension reaches 80%. Based on the deformation data measured by the surveying robot and the temperature conditions, the daytime tensioning and positioning data for the arch rib are determined. To ensure absolute accuracy of the arch rib, the data is verified between 0:00 and 4:00 AM; if significant deviations are found, a second fine-tuning is performed between 5:00 and 7:00 AM.

[0025] Inter-width wind brace installation After the left and right arch ribs are installed, the wind braces are installed using a working crane. Before installation, the absolute position and relative deviation of the left and right arch ribs are re-measured, and the height difference between the left and right arch ribs is strictly controlled. During installation, the wind braces are adjusted to their installation posture, and precise adjustments are made using a hand-operated hoist. Finally, punch nails and temporary bolts are driven in to complete the positioning of the wind braces. The installation of wind braces is staggered from the segment hoisting. The efficiency of wind brace installation is 2 units per day, which is 2-3 days less than the 3-4 days per unit for traditional welded wind braces. This ensures that the wind brace installation is carried out synchronously, effectively preventing it from occupying the critical path. At the same time, the synchronous installation of wind braces increases the stiffness of the cantilevered section of the arch rib and reduces arch rib deformation.

[0026] Plate wrapping and high-strength bolt construction The main constraint on the efficiency of plate welding lies in personnel input. The main processes of plate welding include: assembly, welding, weld inspection, and painting. Circular welds have high requirements and necessitate the use of experienced welders. During welding, rain and wind protection measures must be implemented to ensure weld quality. Welding efficiency is 8-10 m / day. At least two people are required for welding a single plate segment, with a welding time of three days. Plate welding should be organized as an assembly line operation, and the number of delayed segments should be controlled within two segments.

[0027] The main processes for high-strength bolt connections include: initial tightening, final tightening, inspection, and bolt sealing. The tightening time for a single bolt group at a single node is 2 hours. The main factors limiting efficiency are the number and turnover efficiency of the node safety operation platform.

[0028] Arch rib closure The arch rib closure section employs a built-in instantaneous closure joint. After the arch rib segment is hoisted, the arch rib elevation and alignment are adjusted, holes are drilled on-site, and high-strength bolts are used to connect the joint I-beams. The connecting sleeves are then welded in a timely manner to complete the full bridge closure of the arch rib. To achieve rapid arch rib closure, data such as arch rib alignment, temperature, and cable tension are monitored 3-7 days in advance. During closure, arch rib closure can begin once the alignment and temperature have stabilized. During closure, sufficient personnel are assigned for drilling, bolting, assembly, and welding for each closure joint. Considering the possibility that the design temperature cannot be reached during closure, the arch rib alignment under different temperature conditions needs to be calculated in advance to complete the system conversion of the arch rib in the shortest possible time.

[0029] In step 3, the steel pipe arch head segment needs to be constructed and installed in advance. The specific process is as follows: Step 3.1.1: Installation of the arch seat embedded section. The arch seat embedded section structure consists of 4 sleeves and 1 set of hinge seats. The bottom is connected as a whole by a steel connecting frame. According to the design drawings, the position of the left and right embedded section chord support frame is accurately laid out. The control point is the hinge groove embedded plate. Due to processing errors, the center point of the hinge axis needs to be used as the control point. The design coordinates of the hinge axis are used for accurate layout. The control is within 3mm and the through axis is used for verification. Step 3.1.2: Set up pre-embedded support steel sections along the layered casting line of the arch seat. The support steel sections are double-sectioned HN200×100mm steel sections, and the support steel sections are welded to the pre-embedded steel plates in the arch seat. Step 3.1.3: Before installing the supporting steel, re-measure and adjust the embedded steel plate to ensure that the top surface of the supporting steel is on the same plane, so as to ensure that each supporting steel is in close contact with the bottom surface of the positioning steel bracket. Adjust the elevation of the embedded steel plate by filling the steel plate. Step 3.1.4: After the supporting steel is installed, mark the position of the positioning steel bracket on its top surface. Use cable hoisting and manual assistance to install the left chord support steel bracket, the right chord support steel bracket and the intermediate connecting frame in sequence. During hoisting, place the positioning steel bracket according to the marked position on the top surface of the supporting steel. After placing it in place, connect the bolts between the brackets to form a whole, thereby completing the preliminary positioning of the embedded section. Step 3.1.5: After the positioning steel bracket is formed as a whole, a three-way jack is set below it to adjust its position and elevation relative to the arch seat. After the first segment is accurately positioned, the three-way jack is used to finely adjust the pre-embedded section to match the first segment. Step 3.2.1: First segment support installation. Design the first segment positioning support according to the structural form and position of the first segment. The basic principle is that the axis position of the support point of the first segment support is consistent with the first segment chord tube in the installation posture, and the elevation position is 5-10cm lower than the first segment chord tube. Sufficient adjustment space is reserved for the three-way jack. At the same time, attention should be paid to the stress calculation of the positioning support, and measures such as adding lateral support should be taken to ensure the overall stability of the support after being stressed. Step 3.2.2: Check the bearing capacity of the support foundation. If the bearing capacity does not meet the requirements, the foundation should be treated in advance. After the foundation is accepted, the support should be laid out and positioned according to the support design drawings. Step 3.2.3: Construct the pier foundation according to the layout position. The top surface of the foundation should be leveled, and steel plates should be pre-embedded on the top surface of the foundation as components to fix the steel pipe columns. Step 3.2.4: Using a truck crane, install the steel pipe columns, inter-column connecting rods, column top distribution beams, and chord pipe supports in sequence, controlling the support elevation according to the design drawings to ensure the adjustment space of the first section; Step 3.3.1: Segment unloading and inspection. According to the steel structure manufacturing precision requirements and pre-assembly requirements, relevant units are organized to inspect the steel structure manufacturing and vertical assembly, and check the key indicators of the vertical assembly segments, such as elevation, lateral bending, verticality, relative height difference of butt joints, diagonal deviation of inner chord pipes, and flange gap between segments. Step 3.3.2: Set up clearly marked measuring points 1.2m at the front and rear ends of the upper and lower chords of the first segment, and collect the measuring point data. After the assembly is accepted, the measuring point data is used as the target value for installation in the bridge site area after coordinate transformation. Step 3.3.3: After the first section is assembled and accepted and all relevant control point data is collected, it is unloaded and transported. Before transport, the processing and welding quality of the temporary structures of the operating platform, lifting points, and fastening points, as well as the matching of the anchor box and fastening points, should be checked. Step 3.4.1: Segment loading and transportation. Before the ship is transported, relevant departments are contacted and personnel are arranged to close the navigation channel. The ship is positioned according to the segment hoisting position and the cable crane lowering position to ensure that the cable crane can lift vertically and that the component placement position is consistent with the projection of the main arch rib axis. After hoisting, it can be directly transferred to the installation position without the need for rotation operation. Step 3.4.2: Before loading, the transport vessel is moored in the steel structure assembly yard dock with its bow facing outward. The guy ropes on the stern deck are connected to the pre-set mooring bollards on the shore. The guy ropes on the stern are connected to the bollards to fix one end of the cargo ship. The guy ropes on the bow are connected to the mooring points reserved on the steel cylinder piles of the trestle in the river channel. Then the binding ropes of the fixed components are unlocked, the first section is unloaded, and the gantry crane is used to lift it onto the platform of the transport vessel. Step 3.4.3: Workers use the reinforced fixing brackets and limit blocks in the cabin to temporarily fix the components, and use steel wire ropes to wrap them horizontally and vertically respectively and tighten them with a hand hoist. At the same time, a fixing fixture is set at the bottom to fix the lower chord tube to the bottom of the cabin, and the sides are fixed and constrained with steel sections to prevent lateral slippage. Step 3.4.4: After confirming the stability of the segment placement and the reliability of the fixing measures, release the gantry crane hook and the ship's fixing guy ropes, drive the ship out of the pier, sail to the lifting area directly below the cable crane, lower the cable crane's lowering point to provide the most direct position for the ship's positioning, and anchor for positioning; Step 3.5.1: Segment lifting and installation. Before lifting, check the structural operation status of the cable crane and each subsystem again to ensure that the cable crane can be used normally and safely. Place three-way jacks at the support points of the support in advance to prepare for the adjustment of the first segment. Step 3.5.2: After the transport vessel is anchored and positioned, the downstream main crane of the cable crane is lowered, and workers board the ship to install the shackles in sequence at the designated lifting lugs and conduct inspections. After all components are connected, the binding and fixing steel cables are released, and personnel leave the deck. The cable crane then carries out the lifting operation. After the section is completely lifted out of the ship's hold, the transport vessel weighs anchor and sails away from the lifting area. Step 3.5.3: When the first segment is hoisted into the air, adjust the arch seat side lifting point to the low end and the mid-span side lifting point to the high end. Adjust the segment's attitude and inclination angle to roughly conform to the completed bridge attitude. Slowly approach the first segment support. After hoisting into place, observe the segment's inclination angle deviation. Adjust the height difference between the front and rear lifting points to meet the initial vertical position requirements of the segment. Place the arch foot end hinge shaft inside the hinge seat and make it closely fit the hinge seat. Slowly place the entire segment on the support. Step 3.5.4: After the first segment is initially positioned, the cable crane hook is gradually unloaded. During the process, pay attention to checking the overall stability of the first segment and the support. If necessary, add stability measures to ensure that the segment does not overturn during the fine adjustment of the three-way jack. Step 3.5.5: After confirming that the position is stable, adjust the three-way jacks at the support point of the support frame, and at the same time use a high-precision total station to measure and position, gradually achieve the fine adjustment of the first section. Step 3.5.6: Once all measurement and control data of the first segment meet the requirements, reinforce it in a timely manner. Fill the gap between the first segment and the support with spot welding, weld the axis limit plate at the hinge position, and pull the lateral guy ropes to ensure that the tension end of the guy rope is firm and does not shift, and ensure that the segment's posture remains unchanged. Step 3.6.1: Wind brace installation, (1) After the first section of the left and right spans is installed, the wind brace is installed. The wind brace between the sections is hoisted by cable crane working crane. It is hoisted to the front end of the installation position, and the wind brace posture is adjusted. After the posture is adjusted to the right position, the wind brace is pulled by hand hoist so that its end point is embedded in the node plate. The node plate and the connecting plate are gradually aligned and the punch nails are driven in and the temporary bolts are tightened to achieve the precise alignment of the wind brace. Step 3.6.2: After positioning, quickly install the node bolts and tighten them symmetrically. First, perform initial tightening on the high-strength bolts at the nodes. The initial tightening torque is 50% of the final tightening torque. After the initial tightening, perform final tightening according to the construction final tightening torque value. Initial tightening and final tightening should be completed within one day. The tightening quality of the high-strength bolts should be inspected using the torque method according to the specifications. The torque check should be completed within 1 hour and 24 hours after the final tightening. Step 3.7.1: Segment matching and positioning adjustment. After the first segment and wind brace are installed, use jacks set under the support frame to precisely adjust the absolute position of the support frame so that it can match the first segment, and make fine adjustments to the position of local members. Step 3.7.2: When adjusting the three-way jacks, since the positioning support is adjusted in a spatial posture, the three directions affect each other. Therefore, the three-way jacks should be adjusted in coordination to gradually approach the position that matches the first section. The misalignment of the chord tube should not exceed 2mm, and the hinge shaft and hinge groove should be in close contact. If some components cannot be matched, they should be adjusted one by one. First, adjust the transverse bridge position, then adjust the longitudinal bridge position and elevation position. Since the longitudinal bridge position and elevation have a great influence on each other, the adjustment needs to be carried out in multiple rounds. In each round, the stroke of each jack should be controlled within 5mm. Step 3.7.3: After the adjustment is completed, fill the space between the supporting steel and the positioning steel bracket with steel plates to make the two parts fit tightly. Then re-measure the position of the segment chord and hinge seat. After meeting the design requirements, weld the supporting steel, filling steel plate and bottom of the positioning steel bracket together to prevent the positioning steel bracket from shifting when pouring concrete. Step 3.7.4: After welding is completed, the three-way jack is returned to its original position and withdrawn. Construction of the pre-embedded section of the arch seat reinforcement, formwork, and concrete is then carried out. During the remaining construction, the position of the segment chord and hinge seat must be continuously monitored. If any movement occurs, construction should be stopped immediately and adjustments made. In particular, it is strictly forbidden to touch the positioning steel support during concrete pouring.

[0030] The Wujiang Grand Bridge is currently the largest fully bolted steel-concrete arch bridge under construction, featuring extensive temporary facilities, a tight schedule, and high safety risks. The bridge construction adopted the concept of "factory manufacturing, standardized production, and modular installation," systematically preparing for standardized design of temporary structures, prefabricated installation, steel structure processing and fabrication, and transportation. Key influencing factors were carefully managed. The arch ribs were continuously hoisted starting April 10, 2022, and successfully completed with high precision closure on August 15, 2022, taking four months. On average, one segment was hoisted every two days, achieving high-precision and rapid cantilever assembly of the arch ribs. This effectively reduced the installation risks of the arch ribs, ensuring the schedule of this key control project and providing a valuable reference for the construction of similar bridges.

[0031] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A rapid construction method for the arch ribs of prefabricated CFST arch bridges, characterized by: The method includes the following steps: Step 1: Manufacturing and transporting the steel structure of the arch ribs of the arch bridge; Step 2: Set up the temporary structures for the arch ribs of the arch bridge; Step 3: Assemble the cantilever of the arch rib of the arch bridge; In step 3, the steel pipe arch segment must first be constructed and installed in advance. The specific process is as follows: Step 3.1.1: Installation of the arch seat embedded section. The arch seat embedded section structure consists of 4 sleeves and 1 set of hinge seats. The bottom is connected as a whole by a steel connecting frame. According to the design drawings, the positions of the left and right embedded section chord support frames are accurately laid out. The control point is the hinge groove embedded plate. Due to processing errors, the center point of the hinge shaft is used as the control point. The design coordinates of the hinge shaft are used for accurate layout. The control is within 3mm, and the through axis is used for verification. Step 3.1.2: Set up pre-embedded support steel sections along the layered casting line of the arch seat. The support steel sections are double-sectioned HN200×100mm steel sections, and the support steel sections are welded to the pre-embedded steel plates in the arch seat. Step 3.1.3: Before installing the supporting steel, re-measure and adjust the embedded steel plate to ensure that the top surface of the supporting steel is on the same plane, so as to ensure that each supporting steel is in close contact with the bottom surface of the positioning steel bracket. Adjust the elevation of the embedded steel plate by filling the steel plate. Step 3.1.4: After the supporting steel is installed, mark the position of the positioning steel bracket on its top surface. Use cable hoisting and manual assistance to install the left chord support steel bracket, the right chord support steel bracket and the intermediate connecting frame in sequence. During hoisting, place the positioning steel bracket according to the marked position on the top surface of the supporting steel. After placing it in place, connect the bolts between the brackets to form a whole, thereby completing the preliminary positioning of the embedded section. Step 3.1.5: After the positioning steel bracket is formed as a whole, a three-way jack is set below it to adjust its position and elevation relative to the arch seat. After the first segment is accurately positioned, the three-way jack is used to finely adjust the pre-embedded section to match the first segment. Step 3.2.1: First segment support installation. Design the first segment positioning support according to the structural form and position of the first segment. The basic principle is that the axis position of the support point of the first segment support is consistent with the first segment chord tube in the installation posture, and the elevation position is 5-10cm lower than the first segment chord tube. Sufficient adjustment space is reserved for the three-way jack. At the same time, attention should be paid to the stress calculation of the positioning support, and measures should be taken to increase lateral support to ensure the overall stability of the support after being stressed. Step 3.2.2: Check the bearing capacity of the support foundation. If the bearing capacity does not meet the requirements, the foundation should be treated in advance. After the foundation is accepted, the support should be laid out and positioned according to the support design drawings. Step 3.2.3: Construct the pier foundation according to the layout position. The top surface of the foundation should be leveled, and steel plates should be pre-embedded on the top surface of the foundation as components to fix the steel pipe columns. Step 3.2.4: Using a truck crane, install the steel pipe columns, inter-column connecting rods, column top distribution beams, and chord pipe supports in sequence, controlling the support elevation according to the design drawings to ensure the adjustment space of the first section; Step 3.3.1: Segment unloading and inspection. According to the steel structure manufacturing precision requirements and pre-assembly requirements, relevant units are organized to inspect the steel structure manufacturing and vertical assembly, and check the key indicators of the vertical assembly segments, such as elevation, lateral bending, verticality, relative height difference of butt joints, diagonal deviation of inner chord pipes, and flange gap between segments. Step 3.3.2: Set up clearly marked measuring points 1.2m at the front and rear ends of the upper and lower chords of the first segment, and collect the measuring point data. After the assembly is accepted, the measuring point data is used as the target value for installation in the bridge site area after coordinate transformation. Step 3.3.3: After the first section is assembled and accepted and all relevant control point data is collected, it is unloaded and transported. Before transport, the processing and welding quality of the temporary structures of the operating platform, lifting points, and fastening points, as well as the matching of the anchor box and fastening points, should be checked. Step 3.4.1: Segment loading and transportation. Before the ship is transported, relevant departments are contacted and personnel are arranged to close the navigation channel. The ship is positioned according to the segment hoisting position and the cable crane lowering position to ensure that the cable crane can lift vertically and that the component placement position is consistent with the projection of the main arch rib axis. After hoisting, it can be directly transferred to the installation position without the need for rotation operation. Step 3.4.2: Before loading, the transport vessel is moored in the steel structure assembly yard dock with its bow facing outward. The guy ropes on the stern deck are connected to the pre-set mooring bollards on the shore. The guy ropes on the stern are connected to the bollards to fix one end of the cargo ship. The guy ropes on the bow are connected to the mooring points reserved on the steel cylinder piles of the trestle in the river channel. Then the binding ropes of the fixed components are unlocked, the first section is unloaded, and the gantry crane is used to lift it onto the platform of the transport vessel. Step 3.4.3: Workers use the reinforced fixing brackets and limit blocks in the cabin to temporarily fix the components, and use steel wire ropes to wrap them horizontally and vertically respectively and tighten them with a hand hoist. At the same time, a fixing fixture is set at the bottom to fix the lower chord tube to the bottom of the cabin, and the sides are fixed and constrained with steel sections to prevent lateral slippage. Step 3.4.4: After confirming the stability of the segment placement and the reliability of the fixing measures, release the gantry crane hook and the ship's fixing guy ropes, drive the ship out of the pier, sail to the lifting area directly below the cable crane, lower the cable crane's lowering point to provide the most direct position for the ship's positioning, and anchor for positioning; Step 3.5.1: Segment lifting and installation. Before lifting, check the structural operation status of the cable crane and each subsystem again to ensure that the cable crane can be used normally and safely. Place three-way jacks at the support points of the support in advance to prepare for the adjustment of the first segment. Step 3.5.2: After the transport vessel is anchored and positioned, the downstream main crane of the cable crane is lowered, and workers board the ship to install the shackles in sequence at the designated lifting lugs and conduct inspections. After all components are connected, the binding and fixing steel cables are released, and personnel leave the deck. The cable crane then carries out the lifting operation. After the section is completely lifted out of the ship's hold, the transport vessel weighs anchor and sails away from the lifting area. Step 3.5.3: When the first segment is hoisted into the air, adjust the arch seat side lifting point to the low end and the mid-span side lifting point to the high end. Adjust the segment's attitude and inclination angle to roughly conform to the completed bridge attitude. Slowly approach the first segment support. After hoisting into place, observe the segment's inclination angle deviation. Adjust the height difference between the front and rear lifting points to meet the initial vertical position requirements of the segment. Place the arch foot end hinge shaft inside the hinge seat and make it closely fit the hinge seat. Slowly place the entire segment on the support. Step 3.5.4: After the first segment is initially positioned, the cable crane hook is gradually unloaded. During the process, pay attention to checking the overall stability of the first segment and the support, and add stability measures to ensure that the segment does not overturn during the fine adjustment of the three-way jacks. Step 3.5.5: After confirming that the position is stable, adjust the three-way jacks at the support point of the support frame, and at the same time use a high-precision total station to measure and position, gradually achieve the fine adjustment of the first section. Step 3.5.6: Once all measurement and control data of the first segment meet the requirements, reinforce it in a timely manner. Fill the gap between the first segment and the support with spot welding, weld the axis limit plate at the hinge position, and pull the lateral guy ropes to ensure that the tension end of the guy rope is firm and does not shift, and ensure that the segment's posture remains unchanged. Step 3.6.1: Wind brace installation. After the first sections of the left and right spans are installed in place, the wind brace installation is carried out. The wind braces between sections are hoisted using a cable crane. The wind braces are hoisted to the front end of the installation position, and the wind brace posture is adjusted. After the posture is adjusted to the correct position, the wind brace is pulled by a hand hoist so that its end point is embedded into the node plate. The node plate and the connecting plate are gradually aligned, and the punch pins are driven in and the temporary bolts are tightened to achieve precise alignment of the wind brace. Step 3.6.2: After positioning, quickly install the node bolts and tighten them symmetrically. First, perform initial tightening on the high-strength bolts at the nodes. The initial tightening torque is 50% of the final tightening torque. After the initial tightening, perform final tightening according to the construction final tightening torque value. Initial tightening and final tightening should be completed within one day. The tightening quality of the high-strength bolts should be inspected using the torque method according to the specifications. The torque check should be completed within 1 hour and 24 hours after the final tightening. Step 3.7.1: Segment matching and positioning adjustment. After the first segment and wind brace are installed, use jacks set under the support frame to precisely adjust the absolute position of the support frame so that it can match the first segment, and make fine adjustments to the position of local members. Step 3.7.2: When adjusting the three-way jacks, since the positioning support is adjusted in a spatial posture, the three directions affect each other. Therefore, the three-way jacks should be adjusted in coordination to gradually approach the position that matches the first section. The misalignment of the chord tube should not exceed 2mm, and the hinge shaft and hinge groove should be in close contact. If some components cannot be matched, they should be adjusted one by one. First, adjust the transverse bridge position, then adjust the longitudinal bridge position and elevation position. Since the longitudinal bridge position and elevation have a great influence on each other, the adjustment needs to be carried out in multiple rounds. In each round, the stroke of each jack should be controlled within 5mm. Step 3.7.3: After the adjustment is completed, fill the space between the supporting steel and the positioning steel bracket with steel plates to make the two parts fit tightly. Then re-measure the position of the segment chord and hinge seat. After meeting the design requirements, weld the supporting steel, filling steel plate and bottom of the positioning steel bracket together to prevent the positioning steel bracket from shifting when pouring concrete. Step 3.7.4: After welding is completed, the three-way jack is returned to its original position and withdrawn. Construction of the pre-embedded section of the arch seat reinforcement, formwork and concrete is carried out. During the other construction, the position of the segment chord and hinge seat should be continuously observed. If any movement occurs, construction should be stopped immediately and adjustments should be made. During concrete pouring, it is strictly forbidden to touch the positioning steel support. In step 3, the cantilever assembly of the arch rib is the stage with the highest safety risk. During the assembly process, factors that restrict the installation efficiency of the arch rib include ship positioning, temperature affecting the fine-tuning and positioning of the arch rib, installation, pre-tensioning and tensioning of the back bracing, installation of the inter-bracing wind brace, welding of the segmental cladding plates and connection of the high-strength bolts. Then, the timing of continuous hoisting of the arch ribs is determined. According to industry requirements, before installation, sufficient arch rib segments to be installed should be ensured. At least one arch rib should be installed or no less than 3 / 4 of the total number of segments to be installed on the bridge should be stored before installation. The purpose is to avoid the increased risks of waiting for arch rib segments in a large cantilever state. During implementation, the transportation and processing conditions of each project are different. The supply of finished arch rib segments is affected by factors such as steel structure processing efficiency, steel structure transportation, transfer, and weather. Before the hoisting begins, a comprehensive analysis of the supply of arch rib segments is required to ensure a continuous supply of arch rib segments. During this period, precise adjustment and installation of segment #1 are carried out to improve the installation accuracy of the first segment and lay the foundation for subsequent hoisting. The vessel is positioned, and the segment is launched between 5 and 6 a.m. The hoisting operation is carried out using a method that allows the construction vessel to be positioned quickly without affecting navigation. Compared with the traditional transportation positioning method, which requires positioning one day in advance to meet the construction schedule requirements, this method only takes 20 minutes, saving the construction period and saving one day of positioning time for each hoisting operation. The installation, pre-tightening, and tensioning of the back-clip cable are carried out in advance. The back-clip cable is directly anchored, and the back-clip cable is temporarily anchored to the installed segment. After the high bolts of the arch rib flange are tightened, the P-anchor of the back-clip cable is installed. In order to avoid the back-clip cable steel strand bundles from tangling and twisting, and the steel strands not being able to bear the force evenly, the back-clip cable steel strands are threaded individually to ensure that each steel strand is parallel. After the buckle is installed, an intelligent continuous pre-tightening jack is used to automatically pre-tighten the buckle. The pre-tightening jack cylinder adopts a honeycomb design, with each single pre-tightening jack corresponding to pre-tightening one steel strand. According to the principle of communicating vessels, the pressure is equal everywhere in a closed container, thus ensuring that each single pre-tightening jack outputs an equal pre-tightening force. That is, after the steel strand is pre-tightened, the force is uniform and consistent. The pre-tightening efficiency of the pre-tightening equipment is 4 times higher than that of ordinary single-strand pre-tightening. The main constraint on the efficiency of plate wrapping and high bolt construction is the labor input. The main processes of plate wrapping construction are: assembly, welding, weld inspection, and painting. The requirements for circumferential welds are high. During the welding process, rain and wind protection measures should be taken to ensure the welding quality. Plate wrapping welding should be organized according to the flow operation, and the number of delays should be controlled within 2 sections. The main processes for high-strength bolt connection include: initial tightening, final tightening, inspection, and bolt sealing. The tightening time for a single node bolt group is 2 hours. The factors that limit work efficiency are the number and turnover efficiency of the node safety operation platform. For the arch rib closure, an internal instantaneous closure joint is used. After the arch rib segment is hoisted, the arch rib elevation and alignment are adjusted. Holes are drilled on-site and high-strength bolts are used to connect the joint I-beams. The butt sleeves are welded in time to complete the full bridge closure of the arch rib. Data monitoring of the arch rib alignment, temperature, and cable tension is conducted 3-7 days in advance. When closing, the arch rib closure can begin after the alignment and temperature have stabilized. During closure, each closure buckle is equipped with sufficient personnel for drilling, bolting, assembly, and welding. Considering the possibility that the design temperature cannot be reached during closure, the arch rib alignment under different temperature conditions needs to be calculated in advance to complete the system conversion of the arch rib in the shortest possible time.

2. The rapid construction method for the arch rib of the prefabricated CFST arch bridge according to claim 1, characterized in that: The specific process of step 1 is as follows: The arch rib processing adopts a double-pairing process of horizontal assembly and vertical assembly. During the horizontal assembly process, in order to control the processing line of the arch rib, the chord difference of the chord extension is controlled at 5mm. During the vertical assembly process, the lateral bend is controlled at 10mm, the axis deviation is within 8mm, and the segment length deviation is controlled at 5mm. To control welding shrinkage deformation, independent supports are installed on the gusset plate, and free expansion and contraction ends are reserved for welding. The amount of shrinkage is determined in advance through experiments for compensation. To ensure a tight fit between the flanges, the flange surfaces are machine-milled. The two flange surfaces are temporarily tightened together with bolts beforehand. During horizontal assembly, one end of the flange stiffening plate is fully welded, while the other end is left unwelded. Welding is carried out after the vertical assembly alignment is approved to ensure a tight fit between the flanges before the arch rib is hoisted. After the arch rib assembly was completed and accepted, a 3D laser scanner was used to scan the entire process. The 3D laser scanner has an accuracy of 2mm. The scanned model was compared with the manufacturing BIM model to analyze the component processing accuracy in 3D. After the steel structure manufacturing is accepted, the entire segment is treated with anti-corrosion and painting. Then, the entire segment is hoisted onto the ship and transported to the bridge site as a whole. After the segment is transported to the bridge site, it is erected and assembled according to the completed bridge state, and the wind bracing is matched and installed.

3. The rapid construction method for the arch rib of the prefabricated CFST arch bridge according to claim 1, characterized in that: Step 2 involves the following process: the bridge arch ribs are installed using a cable hoisting and inclined cable-stayed installation process without supports. The cable hoisting system is the key equipment for bridge installation, and construction efficiency and hoisting are critical. In the design of the cable hoisting system, two sets of independently operating main cranes are set up, with a maximum tonnage of 160 tons for each main crane. A single set can complete the hoisting of the arch rib segments. The cable tower is designed with a portal truss structure composed of 630×12mm steel pipes and structural steel. The cable tower adopts a prefabricated design, with flange connections between main pipes and bolt connections for pipe couplings and temporary protection. The components are manufactured in the factory and quickly assembled on site using tower cranes, effectively ensuring both construction efficiency and safety. When designing the cable-stayed tower, the tower and cable tower adopt the same design concept. The anchor box, anchor seat and operating platform adopt standardized design, and the components are connected by pins and bolts.

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