Construction method for sectionally folding cantilevers of steel truss basket arch bridge

Abstract

The invention relates to the field of highway steel arch bridge folding construction, in particular to a steel truss basket arch bridge cantilever sectional folding construction method which is easy and convenient to construct and reliable in folding butt joint port alignment. The steel truss basket arch bridge cantilever segmented closure construction method is characterized by comprising the six steps of closure segment manufacturing, closure segment pre-assembly, closure segment measurement, closure segment installation and inspection, closure segment installation segment segmentation and inspection and acceptance. According to the construction method for sectional closure of the cantilevers of the steel truss basket arch bridge, closure in a stress-free state is achieved by controlling closure precision, and rod pieces are not subjected to forced force; high-strength bolt connection is adopted, automatic or semi-automatic welding is adopted, the welding stability is guaranteed, and the connection quality is effectively improved; and after closure and system conversion are completed, final measurement is carried out on a finished bridge line shape to ensure that design requirements are met.

Description

Technical Field

[0001] This invention relates to the field of highway steel arch bridge closure construction, and in particular to a simple construction method for the cantilever segmental closure of a steel truss basket arch bridge with reliable alignment of the closure joints. Background Technology

[0002] The closure of a steel truss basket arch bridge is the most technically challenging and risky critical step in bridge construction. The choice of closure scheme directly affects the quality of the completed bridge, construction safety, and project cost.

[0003] Traditional steel truss basket arch bridge closure schemes employ an integral closure method. This involves assembling the cantilevered steel truss arch ribs on both sides and preparing all truss nodes of the closure segment. Within a pre-determined "temperature window," all closure segment nodes are connected simultaneously (or sequentially within a very short time), achieving an instantaneous transformation of the arch rib from a statically determinate structure to a statically indeterminate structure. However, due to the highly complex spatial structure of steel truss basket arch bridges, especially for large-span basket arch bridges with long main arch cantileveres, the displacements at the cantilever ends caused by temperature changes and solar radiation differences are very large and complex (including vertical, lateral, and torsional displacements). Achieving ideal alignment at all interfaces of multiple closure joints simultaneously presents significant technical challenges. Summary of the Invention

[0004] The present invention aims to solve the problem of the high technical difficulty of achieving ideal alignment of all interfaces of multiple closure joints in existing construction methods, and provides a simple construction method for the cantilever segmental closure of steel truss basket arch bridges with reliable alignment of closure interfaces.

[0005] The present invention relates to a method for constructing segmented closure of a steel truss basket arch bridge cantilevered structure, characterized in that the method comprises six steps: segment fabrication, segment pre-assembly, segment measurement, segment installation and inspection, segmental installation of the closure segment, and inspection and acceptance. The specific steps are as follows: 1) Construction of closure segments (1) Manufacturing length of the closure segment The manufacturing length of the closure segment of the steel truss basket arch is calculated based on the difference between the "predicted temperature at closure" and the "design closure temperature," using the following formula: Lsystem = Ldesign + ΔL L is the blanking length of the closing section, L is the theoretical stress-free length at the design closing temperature, and ΔL is the length adjustment amount. ΔL = αX LletX (Tnet - Tlet) α is the coefficient of linear expansion of steel, typically 1.2 × 10⁻ 5 / ℃; T is the design closing temperature; Tclose is the actual average temperature of the steel truss structure when the closing and locking operation is expected to be performed, which is predicted by continuous monitoring. (2) Fabrication of bolt holes for closure segments For the steel truss basket arch closure segment, bolt holes are pre-made on one side in the factory, and bolt holes are made on-site at the other end during closure. 2) Pre-assembly of closure segments On the 2+1 pre-assembly site, the closure segment is vertically assembled with the previous segment. The components of the closure segment are then inspected, including the following: (1) Geometric dimensions: Check the length, angle and port dimensions of the merging segment members to ensure they match the merging openings on both sides; (2) Bolt hole quality: Check the bolt hole diameter, hole spacing and hole wall smoothness on the closing segment to ensure that there are no burrs and rust; (3) Welding quality: Inspect the welding quality of the closure segment. All welds must undergo visual inspection and non-destructive testing. (4) Separate the segments: After the closure segments are checked and found to be correct, separate the closure segments into the following segments: upper chord of the arch rib, lower chord of the arch rib, web member of the arch rib, horizontal bracing of the arch rib, upper horizontal bracing of the arch rib, and lower horizontal bracing of the arch rib. (5) Pre-assembly record: Record the pre-assembly record of 2+1 pre-assembly, and confirm the accuracy of the merging segment; 3) Measurement of closure segments (1) Temperature control and timing of closure The length of the closure segment and the size of the closure joint are sensitive to temperature changes. Continuous monitoring of the closure joint spacing with temperature changes is necessary to determine the optimal closure time, which is usually selected between 10:00 pm and 6:00 am the next day when the temperature is stable and the temperature difference is small. The closure operation should be completed quickly and continuously to avoid deviations caused by temperature changes. (2) Measurement and Monitoring The closure joint is monitored 24 / 7 to collect data on longitudinal displacement X, axial deviation Y, and elevation Z. The monitoring data is used to fit the temperature-displacement relationship to guide the closure adjustment. A BIM model is used for construction simulation to predict and avoid problems in advance. (3) Structural status adjustment ① Cantilever end elevation adjustment: achieved by adjusting the cable tension of the cable-stayed tower; ② Axis deviation correction: Lateral correction is performed using a chain hoist or pulley system; ③ Closure Spacing Control: Adjust the closure spacing to the specified range using the set longitudinal jacks; 4) Inspection of the closure segment installation (1) Environmental Condition Monitoring ①Temperature: Continuously monitor the temperature change of the closure joint over a 24-hour period, under the "closure temperature" determined in the design. Use the early morning period when the temperature difference between day and night is small and the structural temperature is stable to check whether the real-time temperature is within the allowable range. ② Wind speed: Check the real-time wind speed to ensure it is within the safe construction range and to avoid strong winds affecting accurate positioning and hoisting; (2) Check the state of the closure segment ① Spacing between closure segments: Accurately measure the actual distance between the two sides of the closure segment, compare it with the design calculation value, confirm that its variation pattern conforms to the expected temperature deformation, and verify the accuracy of the processing length of the closure segment component; ② Deviation between axis and elevation: Measure the plane position of the arch ribs on both sides of the closure segment, i.e., the axis, and the elevation; ensure that the deviation is within the range allowed by the design and specifications; ③ Port matching: Check the flatness of the end faces on both sides of the closure segment and the spacing and concentricity of the bolt holes; ensure that the closure segment can be smoothly aligned after hoisting. (3) Temporary constraint status check Check the condition of the arch foot hinge support or fixed joint to ensure there are no foreign objects obstructing it; Inspect the temporary horizontal cables and wind-resistant cable restraints set up during construction. Before closure, adjust or release the force values ​​according to instructions to ensure that the structural system can smoothly transition to the completed bridge state. (4) Self-inspection of closure segment components ① Geometric dimensions: Verify the length, angle, and end dimensions of the merging segment members to ensure they match the merging openings on both sides; ② Bolt hole quality: Check the bolt hole diameter, hole spacing and hole wall smoothness on the closing segment to ensure there are no burrs and rust; 5) Segmented installation of the closure section (1) Sequence of closing segments Install the lower chord of the arch rib → Install the web members of the arch rib → Install the upper chord of the arch rib → Install the lower horizontal bracing of the arch rib → Install the horizontal bracing of the arch rib → Install the upper horizontal bracing of the arch rib. (2) Install the lower chord of the arch rib ① Segment in place When the closing temperature is close to the target closing temperature, a cable crane is used to hoist the lower chord of the arch rib of the closing segment into place. Jacks, chain hoists or tie rods are used to accurately position the lower chord in the horizontal and vertical directions so that the installation position of the lower chord of the arch rib meets the design requirements. ② Drilling of high-strength bolt holes on site After the lower chord of the arch rib is hoisted into place, the actual installation positions of the two ends of the closure segment are accurately measured and laid out on both sides of the closure segment; after the positioning is correct, a steady pressure is applied to drill the hole, and the drill bit is cooled with coolant or lubricating oil to prevent annealing. ③ Install temporary bolts After the high-strength bolt holes of the lower chord of the arch rib are drilled, the temporary constraint and locking of the lower chord of the arch rib of the closing segment should be completed quickly. First, drive in the punch for centering and correction so that the segment interface fits tightly. The number of punches should meet the design requirements. Then, install temporary mounting bolts for temporary fixation. The number of temporary bolts should not be less than 1 / 3 of the total number of bolts at this node. ④ High-strength bolt connection To ensure the quality of bolt friction surface treatment, a calibrated torque wrench must be used for tightening, and the tightening should be carried out in the order of initial tightening to final tightening, with markings made to prevent omissions. (3) Install the remaining segments According to the construction process of installing the lower chord of the arch rib, install the web members of the arch rib, install the upper chord of the arch rib, install the lower horizontal bracing of the arch rib, install the horizontal bracing of the arch rib, and install the upper horizontal bracing segments of the arch rib. (4) Finally joined together ① Install all high-strength bolts on the closure segment. When the temperature stabilizes within the designed closure temperature range, quickly complete the final tightening of the high-strength bolts on the closure segment to achieve permanent structural connection. ②This process requires speed and precision, and should be completed within three hours when the temperature is stable; 6. Quality inspection of closure segments (1) Lifting and Alignment ① Lifting stability: Check that the lifting system is working normally, and that the lifting process of the closing segment is smooth without violent shaking; ② Precise alignment: Monitor the alignment of the closing segment with the two side ports in real time, and use punches or locating pins for initial guidance and positioning; check that the punches are generally inserted into the bolt holes; (2) Construction of high-strength bolt connections ① Insertion direction: The bolts are inserted in the same direction, which meets the specifications; ② Initial tightening and final tightening: Tightening sequence: Strictly check the tightening sequence, proceeding from the part with high joint stiffness to the direction with low constraint, or from the center of the bolt group to the surrounding area, to prevent gaps between the stacked plates; for large nodes, the tightening process involves three steps: initial tightening, re-tightening, and final tightening. Torque and angle control: For the torque method, ensure that the torque wrench used is within its calibration validity period and that the tightening torque value meets the design requirements; for the angle method, check the degree of rotation angle accuracy. Final tightening mark: After final tightening, the bolt head, nut and washer are marked with a colored marker to prevent omissions or repeated tightening; (2) Inspection of high-strength bolts ① Final bolt tightening inspection: Use a calibrated torque wrench to randomly check the bolts after final tightening; check that the torque value is within the deviation range; bolts that are under-tightened or over-tightened need to be replaced and re-tightened.

[0006] ② Exposed bolt threads: Check the length of exposed bolt threads after final tightening. The exposed threads of the nut should be no less than 2 to 3 threads, and the exposed length should not exceed 4 threads. ③Joint contact surface: Check the fit of the plate stack contact surface, and insert a 0.3mm feeler gauge to a depth not exceeding 20mm; After inspection and acceptance, the cantilever segment closure construction was completed.

[0007] The present invention relates to a method for constructing cantilevered segmental closure of a steel truss basket arch bridge. By controlling the closure accuracy, it achieves stress-free closure, and the members are not subject to forced force. High-strength bolts are used for connection, and automated or semi-automatic welding is employed to ensure welding stability and effectively improve connection quality. After closure and system conversion, the final bridge alignment is measured to ensure compliance with design requirements. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the closure segment structure of the present invention.

[0009] Among them, the upper chord of the arch rib is 1, the lower chord of the arch rib is 2, and the web member of the arch rib is 3. Detailed Implementation

[0010] Example 1: A method for constructing the cantilever segmental closure of a steel truss basket arch bridge, comprising six steps: segment fabrication, segment pre-assembly, segment measurement, segment installation and inspection, segmental installation of the closure segment, and inspection and acceptance. The specific steps are as follows: 1) Construction of closure segments (1) Manufacturing length of the closure segment The manufacturing length of the closure segment of the steel truss basket arch is calculated based on the difference between the "predicted temperature at closure" and the "design closure temperature," using the following formula: Lsystem = Ldesign + ΔL L is the blanking length of the closing section, L is the theoretical stress-free length at the design closing temperature, and ΔL is the length adjustment amount. ΔL = αX LletX (Tnet - Tlet) α is the coefficient of linear expansion of steel, typically 1.2 × 10⁻ 5 / ℃; T is the design closing temperature; Tclose is the actual average temperature of the steel truss structure when the closing and locking operation is expected to be performed, which is predicted by continuous monitoring. (2) Fabrication of bolt holes for closure segments For the steel truss basket arch closure segment, bolt holes are pre-made on one side in the factory, and bolt holes are made on-site at the other end during closure. 2) Pre-assembly of closure segments On the 2+1 pre-assembly site, the closure segment is vertically assembled with the previous segment. The components of the closure segment are then inspected, including the following: (1) Geometric dimensions: Check the length, angle and port dimensions of the merging segment members to ensure they match the merging openings on both sides; (2) Bolt hole quality: Check the bolt hole diameter, hole spacing and hole wall smoothness on the closing segment to ensure that there are no burrs and rust; (3) Welding quality: Inspect the welding quality of the closure segment. All welds must undergo visual inspection and non-destructive testing. (4) Separate the segments: After the closure segments are checked and found to be correct, separate the closure segments into the following segments: upper chord of the arch rib, lower chord of the arch rib, web member of the arch rib, horizontal bracing of the arch rib, upper horizontal bracing of the arch rib, and lower horizontal bracing of the arch rib. (5) Pre-assembly record: Record the pre-assembly record of 2+1 pre-assembly, and confirm the accuracy of the merging segment; 3) Measurement of closure segments (1) Temperature control and timing of closure The length of the closure segment and the size of the closure joint are sensitive to temperature changes. Continuous monitoring of the closure joint spacing with temperature changes is necessary to determine the optimal closure time, which is usually selected between 10:00 pm and 6:00 am the next day when the temperature is stable and the temperature difference is small. The closure operation should be completed quickly and continuously to avoid deviations caused by temperature changes. (2) Measurement and Monitoring The closure joint is monitored 24 / 7 to collect data on longitudinal displacement X, axial deviation Y, and elevation Z. The monitoring data is used to fit the temperature-displacement relationship to guide the closure adjustment. A BIM model is used for construction simulation to predict and avoid problems in advance. (3) Structural status adjustment ① Cantilever end elevation adjustment: achieved by adjusting the cable tension of the cable-stayed tower; ② Axis deviation correction: Lateral correction is performed using a chain hoist or pulley system; ③ Closure Spacing Control: Adjust the closure spacing to the specified range using the set longitudinal jacks; 4) Inspection of the closure segment installation (1) Environmental Condition Monitoring ①Temperature: Continuously monitor the temperature change of the closure joint over a 24-hour period, under the "closure temperature" determined in the design. Use the early morning period when the temperature difference between day and night is small and the structural temperature is stable to check whether the real-time temperature is within the allowable range. ② Wind speed: Check the real-time wind speed to ensure it is within the safe construction range and to avoid strong winds affecting accurate positioning and hoisting; (2) Check the state of the closure segment ① Spacing between closure segments: Accurately measure the actual distance between the two sides of the closure segment, compare it with the design calculation value, confirm that its variation pattern conforms to the expected temperature deformation, and verify the accuracy of the processing length of the closure segment component; ② Deviation between axis and elevation: Measure the plane position of the arch ribs on both sides of the closure segment, i.e., the axis, and the elevation; ensure that the deviation is within the range allowed by the design and specifications; ③ Port matching: Check the flatness of the end faces on both sides of the closure segment and the spacing and concentricity of the bolt holes; ensure that the closure segment can be smoothly aligned after hoisting. (3) Temporary constraint status check Check the condition of the arch foot hinge support or fixed joint to ensure there are no foreign objects obstructing it; Inspect the temporary horizontal cables and wind-resistant cable restraints set up during construction. Before closure, adjust or release the force values ​​according to instructions to ensure that the structural system can smoothly transition to the completed bridge state. (4) Self-inspection of closure segment components ① Geometric dimensions: Verify the length, angle, and end dimensions of the merging segment members to ensure they match the merging openings on both sides; ② Bolt hole quality: Check the bolt hole diameter, hole spacing and hole wall smoothness on the closing segment to ensure there are no burrs and rust; 5) Segmented installation of the closure section (1) Sequence of closing segments Install the lower chord of the arch rib → Install the web members of the arch rib → Install the upper chord of the arch rib → Install the lower horizontal bracing of the arch rib → Install the horizontal bracing of the arch rib → Install the upper horizontal bracing of the arch rib. (2) Install the lower chord of the arch rib ① Segment in place When the closing temperature is close to the target closing temperature, a cable crane is used to hoist the lower chord of the arch rib of the closing segment into place. Jacks, chain hoists or tie rods are used to accurately position the lower chord in the horizontal and vertical directions so that the installation position of the lower chord of the arch rib meets the design requirements. ② Drilling of high-strength bolt holes on site After the lower chord of the arch rib is hoisted into place, the actual installation positions of the two ends of the closure segment are accurately measured and laid out on both sides of the closure segment; after the positioning is correct, a steady pressure is applied to drill the hole, and the drill bit is cooled with coolant or lubricating oil to prevent annealing. ③ Install temporary bolts After the high-strength bolt holes of the lower chord of the arch rib are drilled, the temporary constraint and locking of the lower chord of the arch rib of the closing segment should be completed quickly. First, drive in the punch for centering and correction so that the segment interface fits tightly. The number of punches should meet the design requirements. Then, install temporary mounting bolts for temporary fixation. The number of temporary bolts should not be less than 1 / 3 of the total number of bolts at this node. ④ High-strength bolt connection To ensure the quality of bolt friction surface treatment, a calibrated torque wrench must be used for tightening, and the tightening should be carried out in the order of initial tightening to final tightening, with markings made to prevent omissions. (3) Install the remaining segments According to the construction process of installing the lower chord of the arch rib, install the web members of the arch rib, install the upper chord of the arch rib, install the lower horizontal bracing of the arch rib, install the horizontal bracing of the arch rib, and install the upper horizontal bracing segments of the arch rib. (4) Finally joined together ① Install all high-strength bolts on the closure segment. When the temperature stabilizes within the designed closure temperature range, quickly complete the final tightening of the high-strength bolts on the closure segment to achieve permanent structural connection. ②This process requires speed and precision, and should be completed within three hours when the temperature is stable; 6. Quality inspection of closure segments (1) Lifting and Alignment ① Lifting stability: Check that the lifting system is working normally, and that the lifting process of the closing segment is smooth without violent shaking; ② Precise alignment: Monitor the alignment of the closing segment with the two side ports in real time, and use punches or locating pins for initial guidance and positioning; check that the punches are generally inserted into the bolt holes; (2) Construction of high-strength bolt connections ① Insertion direction: The bolts are inserted in the same direction, which meets the specifications; ② Initial tightening and final tightening: Tightening sequence: Strictly check the tightening sequence, proceeding from the part with high joint stiffness to the direction with low constraint, or from the center of the bolt group to the surrounding area, to prevent gaps between the stacked plates; for large nodes, the tightening process involves three steps: initial tightening, re-tightening, and final tightening. Torque and angle control: For the torque method, ensure that the torque wrench used is within its calibration validity period and that the tightening torque value meets the design requirements; for the angle method, check the degree of rotation angle accuracy. Final tightening mark: After final tightening, the bolt head, nut and washer are marked with a colored marker to prevent omissions or repeated tightening; (2) Inspection of high-strength bolts ① Final bolt tightening inspection: Use a calibrated torque wrench to randomly check the bolts after final tightening; check that the torque value is within the deviation range; bolts that are under-tightened or over-tightened need to be replaced and re-tightened.

[0011] ② Exposed bolt threads: Check the length of exposed bolt threads after final tightening. The exposed threads of the nut should be no less than 2 to 3 threads, and the exposed length should not exceed 4 threads. ③Joint contact surface: Check the fit of the plate stack contact surface, and insert a 0.3mm feeler gauge to a depth not exceeding 20mm; After inspection and acceptance, the cantilever segment closure construction was completed.

Claims

1. A steel truss basket handle arch bridge cantilever segment closure construction method, characterized in that The construction method includes six steps: segment fabrication, segment pre-assembly, segment measurement, segment installation and inspection, segmental installation of the closure segment, and inspection and acceptance. The specific steps are as follows: 1) Construction of closure segments (1) Manufacturing length of the closure segment The manufacturing length of the closure segment of the steel truss basket arch is calculated based on the difference between the "predicted temperature at closure" and the "design closure temperature," using the following formula: Lsystem = Ldesign + ΔL L is the blanking length of the closing section, L is the theoretical stress-free length at the design closing temperature, and ΔL is the length adjustment amount. ΔL = αX LletX (Tnet - Tlet) a is the linear expansion coefficient of the steel material, typically 1.2 x 10⁻ 5 / °C; Tset is the design closing temperature; Tclose is the actual average temperature of the steel truss structure at the time of the closing locking operation, predicted by continuous monitoring values; (2) Fabrication of bolt holes for closure segments For the steel truss basket arch closure segment, bolt holes are pre-made on one side in the factory, and bolt holes are made on-site at the other end during closure. 2) Pre-assembly of closure segments On the 2+1 pre-assembly site, the closure segment is vertically assembled with the previous segment. The components of the closure segment are then inspected, including the following: (1) Geometric dimensions: Check the length, angle and port dimensions of the merging segment members to ensure they match the merging openings on both sides; (2) Bolt hole quality: Check the bolt hole diameter, hole spacing and hole wall smoothness on the closing segment to ensure that there are no burrs and rust; (3) Welding quality: Inspect the welding quality of the closure segment. All welds must undergo visual inspection and non-destructive testing. (4) Separate the segments: After the closure segments are checked and found to be correct, separate the closure segments into the following segments: upper chord of the arch rib, lower chord of the arch rib, web member of the arch rib, horizontal bracing of the arch rib, upper horizontal bracing of the arch rib, and lower horizontal bracing of the arch rib. (5) Pre-assembly record: Record the pre-assembly record of 2+1 pre-assembly, and confirm the accuracy of the merging segment; 3) Measurement of closure segments (1) Temperature control and timing of closure The length of the closure segment and the size of the closure joint are sensitive to temperature changes. Continuous monitoring of the closure joint spacing with temperature changes is necessary to determine the optimal closure time, which is usually selected between 10:00 pm and 6:00 am the next day when the temperature is stable and the temperature difference is small. The closure operation should be completed quickly and continuously to avoid deviations caused by temperature changes. (2) Measurement and Monitoring The closure joint is monitored 24 / 7 to collect data on longitudinal displacement X, axial deviation Y, and elevation Z. The monitoring data is used to fit the temperature-displacement relationship to guide the closure adjustment. A BIM model is used for construction simulation to predict and avoid problems in advance. (3) Structural status adjustment ① Cantilever end elevation adjustment: achieved by adjusting the cable tension of the cable-stayed tower; ② Axis deviation correction: Lateral correction is performed using a chain hoist or pulley system; ③ Closure Spacing Control: Adjust the closure spacing to the specified range using the set longitudinal jacks; 4) Inspection of the closure segment installation (1) Environmental Condition Monitoring ①Temperature: Continuously monitor the temperature change of the closure joint over a 24-hour period, under the "closure temperature" determined in the design. Use the early morning period when the temperature difference between day and night is small and the structural temperature is stable to check whether the real-time temperature is within the allowable range. ② Wind speed: Check the real-time wind speed to ensure it is within the safe construction range and to avoid strong winds affecting accurate positioning and hoisting; (2) Check the state of the closure segment ①Segment spacing: Accurately measure the actual distance between the two sides of the closure segment and compare it with the design calculation value to confirm that the change rule conforms to the expected temperature deformation and verify the accuracy of the processing length of the closure segment component; ②Axis and elevation deviation: Measure the plane position of the arch rib on both sides of the closure segment, i.e. the axis, and the elevation, i.e. the elevation; Ensure that the deviation is within the range allowed by design and specifications; ③Port matching: Check the flatness of the end face of the closure segment on both sides, as well as the spacing and concentricity of the bolt hole group; Ensure that the closure segment can be smoothly aligned after hoisting; ⑶Temporary restraint state inspection Check the state of the hinge support or consolidation at the arch foot to ensure that there is no foreign object blocking; Check the temporary horizontal cable and wind cable restraint measures set during construction, and adjust or release the force value according to the instructions before closure to ensure that the structural system can smoothly transition to the completed bridge state; ⑷Closure segment component self-inspection ①Geometric size: Review the length, angle and port size of the closure segment rod to ensure that it matches the two sides of the closure port; ②Bolt hole quality: Check the bolt hole diameter, hole distance and hole wall smoothness on the closure segment to ensure that there are no burrs and rust; 5) Installation of segmented closure segment ⑴Closure segment sequence Install the arch rib lower chord → install the arch rib web → install the arch rib upper chord → install the arch rib lower chord → install the arch rib transverse link → install the arch rib upper chord; ⑵Install the arch rib lower chord ①Segment positioning When the temperature approaches the planned closure temperature, use the cable crane to hoist the arch rib lower chord of the closure segment into position, use the jack, inverted chain hoist or opposite-pulling facilities for accurate positioning in the horizontal and vertical directions, and make the arch rib lower chord installation position meet the design requirements; ②On-site high-strength bolt hole drilling After the arch rib lower chord is hoisted into position, accurately measure the actual installation position of the two ports of the closure segment on both sides; After positioning, apply stable pressure to drill, and use cooling liquid or lubricating oil to cool the drill bit to prevent annealing; ③Install temporary bolts After the high-strength bolt hole of the arch rib lower chord is drilled, quickly complete the temporary restraint locking of the arch rib lower chord of the closure segment; First, hit the punch pin for centering correction to make the segment interface tightly fit, the number of punch pins should meet the design requirements, then install temporary installation bolts for temporary fixation, the number of temporary bolts should not be less than 1 / 3 of the total number of bolts at the node; ④High-strength bolt connection Ensure the quality of the bolt friction surface treatment, use a calibrated torque wrench to tighten in the order of initial tightening to final tightening, and make a mark to prevent missed tightening; ⑶Install the remaining segments According to the construction technology of installing the arch rib lower chord, install the arch rib web, install the arch rib upper chord, install the arch rib lower chord, install the arch rib transverse link, and install the arch rib upper chord segment installation; ⑷Final closure ①Install all high-strength bolts of the closure segment, and when the temperature stabilizes within the design closure temperature range, quickly complete the final tightening of the high-strength bolts of the closure segment to achieve permanent connection of the structure; ②This process requires speed and accuracy, and it must be completed within three hours when the temperature is stable; 6, Closure segment quality inspection ⑴Hoisting and alignment ①Hoisting stability: Check that the hoisting system is working properly and that the closure segment hoisting process is stable without violent shaking; ② Precise centering: Real-time monitoring of the alignment of the folded segment and the two side ports, using punch or positioning pin for preliminary guidance and positioning; check the punch generally above the bolt hole; ⑵High-strength bolt connection construction ① Direction of insertion: The direction of bolt insertion is consistent, meeting the specification requirements; ② Initial and final tightening: Tightening sequence: Strictly check the tightening sequence, from the part with high joint stiffness to the part with small constraint, or from the center of the bolt group to the periphery, to avoid gaps between the plate stacks; For large nodes, it goes through three steps of initial tightening, re-tightening and final tightening; Torque and angle control: For torque method, ensure that the torque wrench used is within the calibration validity period, and the tightening torque value meets the design requirements; For the angle method, check the rotation angle to the right degree; Final tightening mark: The bolt head, nut and washer after final tightening are marked with colored markers to prevent missed or repeated tightening; ⑵High-strength bolt inspection ① Final tightening inspection of the bolt: Use a calibrated torque wrench to check the final tightening of the bolt; Check the torque value within the tolerance range; Replace and retighten the under-tightened or over-tightened bolt; ② Exposed bolt thread: Check the exposed length of the bolt thread after final tightening, the exposed thread of the nut should not be less than 2 to 3 threads, and the exposed length should not be more than 4 threads; ③ Joint contact surface: Check the fit of the plate stack contact surface, the depth of the 0.3mm plug should not exceed 20mm; After inspection and acceptance, complete the cantilever segment folding construction.

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