Construction method of suspension single-cable-plane cable-stayed steel bridge

Abstract

The application discloses a construction method of a suspension single-cable-plane cable-stayed steel bridge, which comprises the following steps: step one, three-dimensional modeling of the cable-stayed bridge; step two, temporary support system erection; step three, integral stress analysis of the cable-stayed bridge; step four, comfort and vibration reduction analysis of the cable-stayed bridge for people walking; and step five, cable installation and tensioning. The application is aimed at the problems of small stiffness of the suspension system single-cable-plane cable-stayed bridge structure, unsatisfied comfort for people walking and difficult asymmetric collaborative tensioning of small cables, utilizes finite element simulation analysis technology, systematically analyzes dynamic characteristics and sensitive frequency ranges under different load conditions and under different walking working conditions, and sets vertical and transverse TMD damping devices, so that the comfort for people walking reaches the best level, and the safety and comfort of the bridge are ensured.

Description

Technical Field

[0001] This invention belongs to the field of bridge construction technology, specifically relating to a construction method for a suspended single-cable-stayed steel bridge. Background Technology

[0002] Suspended cable-stayed bridges offer excellent scenic views, but their flexible structure results in low stiffness, leading to less noticeable vibrations compared to conventional pedestrian bridges. The vibrations can exceed the limits of human comfort, causing psychological distress for pedestrians. Achieving a balance between the bridge's lightness and pedestrian comfort presents a significant challenge.

[0003] The working mechanism of cable-stayed bridges is similar to prestressing. Each cable in a cable-stayed bridge needs to be tensioned to a certain force value to achieve the overall structural load-bearing capacity. In actual construction, the total cable force is generated by tensioning each cable sequentially. The tensioning of each cable affects the overall load-bearing capacity of the cable-stayed bridge, and the tensioning of cables in the next stage also affects the force value of cables tensioned in the previous stage. Cable force is divided into two parts: one is the final bridge cable force, which refers to the cable force distribution after construction to ensure a reasonable load-bearing capacity for the cable-stayed bridge; the other is the construction cable force, which refers to the specific tension value each cable should be tensioned to during the phased construction of the cable-stayed bridge to ensure that the final bridge cable force matches the initially designed reasonable final bridge force value. This is called the reasonable construction cable force. Therefore, determining the appropriate cable force values ​​for the initial bridge completion state and the cable force values ​​that need to be tensioned for each cable during the construction phase has become crucial in the construction of cable-stayed bridges.

[0004] If the cable tension cannot be controlled due to manufacturing and assembly errors of the main beam, the deviation in cable tension is often sacrificed in order to meet alignment requirements and achieve elevation control. During construction, it is essential to strictly control the magnitude and sequence of cable tension to ensure the safe use of the stay cables, which is of great significance for overall construction control.

[0005] For suspended cable-stayed landscape bridges, the design cable force values ​​are relatively small, and the tensioning accuracy requirements are high. Furthermore, the asymmetrical arrangement of the towers necessitates asymmetrical tensioning. Different tensioning sequences can lead to significant differences in the bridge's alignment. Therefore, designing a construction method for a suspended single-plane cable-stayed steel bridge to determine a reasonable cable force and tensioning sequence for the completed bridge has become a pressing technical problem for those skilled in the field. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a construction method for a suspended single-cable-stayed steel bridge, so as to at least solve some of the above-mentioned technical problems.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A construction method for a suspended single-cable-stayed steel bridge includes the following steps: Step 1, three-dimensional modeling of the cable-stayed bridge; Step 2, construction of a temporary support system; Step 3, overall stress analysis of the cable-stayed bridge; Step 4, pedestrian comfort and vibration reduction analysis on the cable-stayed bridge; Step 5, installation and tensioning of the stay cables.

[0009] Furthermore, in step one, during the 3D modeling of the cable-stayed bridge, the 3D coordinate parameters from the design drawings are imported into CAD and fitted with curves to form a line model. The line model is then imported into Rhino for detailed refinement. During the drawing, processing, and installation, the CAD model is uniformly exported from the Rhino model to ensure consistent control point data. During construction, the processed and installed entities are re-measured, and the data is returned to the CAD model for 3D comparison. Adjustments are made based on the comparison results to ensure the installation accuracy of the curved, thin, irregularly shaped steel box girder.

[0010] Furthermore, in step two, when the temporary support system is erected, the support frame is designed as a round tube support frame made of Q235B material. The uprights are made of round tubes Φ325*10, and the horizontal and diagonal supports are made of round tubes Φ150*10. The support frame size is 2.5m*3m. The standard sections of the support frame are made in three lengths: 1m, 3m, and 4m. The connection of each node within the support frame section is designed with flanges for easy installation and disassembly. The horizontal supports and uprights are connected by semi-penetration welds with a penetration depth of 0.8t and a weld size of not less than 0.75t and not less than 8mm. The welds at each node of the diagonal support connection are fillet welds of grade three with a weld size of not less than 8mm. At the column base and flange connection, a column base stiffening plate is installed with a plate thickness of 12mm and a size of 150*200*16mm.

[0011] The upper part of the temporary support is connected to customized fixtures, which include a transfer beam, an elevation stool, and a limiting block. The transfer beam has a specification of not less than HM294×200×8×12. The support uprights of the elevation stool are made of round tube P159×8, and the connecting horizontal and diagonal bars are made of round tube P140×8. The limiting block is made of steel plate splicing, and the limiting surface is plumb. The transfer beam, elevation stool, limiting block, and support column are connected to each other by welding.

[0012] The temporary supports are constructed with enlarged concrete foundations. The dimensions of a single enlarged concrete foundation for the main bridge support are 3.5m × 4.0m × 0.5m. The main bridge supports are connected by welding 700×700×20mm embedded parts. The concrete used for the enlarged concrete foundations is C30, and a single layer of bidirectional C16@150 steel mesh is installed at the bottom. A 10cm thick C20 concrete pad is installed below the enlarged concrete foundations of the supports. Depending on the bridge width and the site's geographical environment, long-side splicing type and short-side splicing type are set up. The foundation dimensions are 6.7m × 4.0m × 0.5m for the long-side splicing double-row support enlarged concrete foundation and 7.7m × 3.5m × 0.5m for the short-side splicing double-row support foundation.

[0013] Furthermore, during the construction of the temporary support system, the area of ​​the expanded concrete foundation of the support was positioned and marked according to the planar location of the temporary support. Based on the geological survey report and actual site conditions, the expanded concrete foundation construction was carried out, excavating to a silty clay layer with a bearing capacity characteristic value of 160 kPa as the bearing layer. Then, standard support sections were hoisted and welded firmly to the embedded plates at the bottom, with a weld length of not less than 200 mm on each side. Standard sections were connected using flange bolts for easy disassembly later. Next, customized tooling was fabricated. The three-dimensional coordinates of the support points were exported from the 3D model. The position of the elevation stool uprights was located on the transfer beam using planar coordinate data, and the lengths of the uprights and diagonal braces were determined using elevation data. Similarly, single-sided limiting blocks for the main bridge were fabricated and welded to the transfer beam. Finally, the entire tooling was hoisted and the support columns were welded and fixed to the transfer beam. Before the main bridge was hoisted, the height of the elevation stool was measured and fine-tuned. The customized tooling, mainly including the transfer beam, elevation stool, and limiting blocks, was connected to the upper part of the temporary support. The height of the steel elevation stool was set as: theoretical height + 20 mm, and not less than 350 mm. A 50t screw jack is placed next to each support point, and the screw jack is positioned according to the elevation data of the completed bridge deck. A secondary elevation section (which is lightweight) is made according to the clearance distance between the original elevation bench and the steel box girder, and the required elevation is achieved by adding steel plates.

[0014] Furthermore, in step three, during the overall stress analysis of the cable-stayed bridge, the finite element analysis software Midas is used to model the entire cable-stayed bridge and perform numerical simulation and analysis to fully understand the stress distribution of the main bridge's irregular steel box girder during the construction process using temporary supports. To ensure the bridge's alignment, the cable force values ​​are determined through simulation to ensure that the alignment meets design requirements after the main bridge is closed and unloaded. By comparing design parameters, simulation calculations are performed during the construction phase to obtain the corresponding pre-camber, thereby determining the formwork elevation for the bridge construction phase. Based on the measured elevation, the previous phase is analyzed to determine the alignment and stress for the next phase, thus determining the formwork elevation. Simultaneously, the curved irregular steel box girder bridge segment is filled with a blank arc-shaped lower sealing plate at the interface position, and a temporary connecting plate is set every 300mm on the upper and lower top plates for docking and positioning. The left and right contours correspond one-to-one with the processing and manufacturing positioning lines. After the entire bridge section is in place, the spatial positioning parameters of the later-added curved panels are measured and fed back into the detailed model. Based on the actual installation dimensions and design control curves, the spatial parameters of the later-added curved lower sealing plates are re-derived. Rigid templates are then used for individual alignment and correction before the missing curved lower sealing plates are installed. This ensures that the alignment of the cable-stayed bridge in its completed state meets the requirements for normal use. Through data monitoring and collection during the construction phase, the internal forces of the cable-stayed bridge are ensured to be reasonable and the alignment smooth after completion, reducing construction errors and workload, and guaranteeing the successful completion of the cable-stayed bridge.

[0015] Furthermore, in step four, during the pedestrian comfort vibration reduction analysis of the cable-stayed bridge, a 3D refined finite element model is established using MidasCivil to systematically analyze the human-induced vibration of the bridge; the dynamic characteristics of the first 10 vertical and first 5 lateral vibration modes of the pedestrian cable-stayed bridge are calculated using eigenvalues; according to the comfort requirements of the standard, the human-induced vibration comfort needs to be verified when the vertical modal vibration frequency is in the range of 1.25Hz to 3.0Hz and the lateral modal vibration frequency is in the range of 0.5Hz to 1.2Hz.

[0016] Based on the dynamic characteristics, the vertical vibration frequency sensitivity range is from the first to the third order; the lateral vibration frequency sensitivity range is from the second to the fourth order. Comfort analysis was conducted using the sensitive modal frequencies determined according to EN03-2007 and CJJ69-201X standards. The dynamic characteristics (peak acceleration) of different crowd loads under various conditions such as continuous walking, group walking, and multiple people jumping were analyzed to evaluate pedestrian comfort. Based on the comfort analysis results, a tuned mass damper (TMD) was used to increase the damping of the cable-stayed bridge structure. Vertical and lateral TMD damping devices were installed, and TMD vibration control simulations were performed on the irregular steel box girder. Optimal tuned mass damper parameters were determined, and the changes in bridge vibration response before and after adding dampers were analyzed based on the validated model. The effectiveness of the tuned mass damper and the comfort of the bridge after adding dampers were evaluated, thus improving pedestrian vibration comfort.

[0017] Furthermore, in step five, the installation and tensioning of the stay cables includes the following steps:

[0018] Step 1: Establish a three-dimensional finite element model; Step 2: Simulate and analyze the tensioning process; Step 3: Deploy and install the cables;

[0019] Step 4, cable tensioning and monitoring; Step 5, second-phase dead load and cable adjustment; Step 6, bridge completion monitoring and TMD frequency modulation.

[0020] Furthermore, in step 1, when establishing the three-dimensional finite element model, MIDAS / CIVIL is used to analyze the pylon, main beam, stay cables and temporary supports; the geometry reflects the final alignment of the bridge, accurately reflects the structural stiffness and cross-sectional properties, structural mass and non-structural mass technical parameters, so as to reasonably analyze the actual mechanical behavior of the structural system;

[0021] Constraints during the process: The pylon adopts a tower-beam fixed connection, with unidirectional support at the beam end piers and unidirectional movable support at the auxiliary piers of beam segment C; the support is simulated according to the actual temporary support position.

[0022] Loads applied during the process: Main beam dead load: After calculating the weight of the transverse diaphragms in segments in the beam element model, uniformly distributed loads are applied to different beam segments. In addition to the transverse diaphragms, the beam segments are pre-installed with TMD vibration damping devices at the factory. The weight of the TMD vibration damping devices is loaded onto the corresponding nodes using nodal loads. C20 concrete is poured at the beam ends for ballast, and ballast loads are applied to the model. Secondary dead load: The secondary dead load includes drainage structures, railings and handrails, and bridge deck pavement. The railings are calculated based on the weight intensity per linear meter. The average thickness of the pavement layer is 55mm, and the load is calculated and applied in segments according to the width variation of different beam segments.

[0023] In step 2, during the simulation analysis of the tensioning process, the cable force optimization of the completed bridge is first performed. Manufacturing pre-camber is not considered; an ideal bridge alignment is used for fabrication. The main beam is hoisted and installed on a support frame and finally welded. The simply supported main beam exhibits initial deflection, which is converted to a continuous beam after welding. Similarly, the initial state of the tower is an ideal vertical state. The ideal bridge state after simulating cable tensioning and applying all secondary dead loads is simulated, and the corresponding cable force is the target bridge cable force. Then, the cable tensioning sequence is simulated and optimized. Cable tensioning is performed in two steps. The first step, after the tower cables are hung, is symmetrically tensioned to 100% of the design value using a graded loading method. The cable tensioning process employs three levels of loading: 30%, 80%, and 100% of the design value. A five-minute pause is taken after each level of loading to allow for monitoring data collection and simulation analysis. The second step involves adjusting the cable tension to the design value based on the monitoring and simulation analysis results after the bridge deck, lighting, and ancillary facilities are completed. The tensioning sequence for individual tower cables is from bottom to top and from shortest to longest, with one pair of stay cables tensioned symmetrically at a time. Tensioning begins from the second pair of cables and proceeds from bottom to top, ending with the first pair. If the simulation analysis indicates that some cables have not reached the designed cable tension value for the completed bridge, tensioning continues; if the cable tension of some cables exceeds the designed cable tension value, the tension is adjusted and released.

[0024] Furthermore, in step 3, the deployment and installation of the cable are carried out using a mobile crane, an aerial work platform, and a chain hoist in coordination. During this process, the crane provides vertical force, the chain hoist provides horizontal force, and the aerial work platform provides the working platform. This includes the following steps:

[0025] Step a: Hoist the cable reel to the bridge deck, with the truck crane assisting manual labor in spreading the cable; Step b: Hoist the fixed end of the cable body close to the tower;

[0026] Step c: The crane and the aerial work platform work together to install and fix the cables; Step d: The crane and the chain hoist work together to install the cable adjustment end; Step e: Repeat steps a, b, c and d to complete the installation of all cables.

[0027] In step 4, during cable tensioning and monitoring, the entire tensioning process is guided by real-time on-site monitoring data; this includes the following steps:

[0028] Step (a) Deploy sensors and monitoring points throughout the bridge; Step (b) Install tensioning fixtures and jacks; Step (c) Load the cables at three levels: 30%, 80%, and 100%, and monitor them simultaneously; Step (d) Monitor the stress and strain values ​​of the towers and main bridge, as well as the cable force values, for every 2-3 pairs of cables tensioned; Step (e) Analyze the monitoring data to guide the adjustment of the tensioned cables; Step (f) Repeat steps (a), (b), (c), (d), and (e) to complete the tensioning of the entire cable; Step (g) Monitor the entire bridge to guide the tensioning of the next tower cable.

[0029] Furthermore, in step 5, during the second-phase dead load and cable adjustment, after the completion of the second-phase bridge deck system construction, including the bridge deck, railings, and handrails, the cable force of the entire bridge is adjusted to the design cable force based on the measured cable force values. First, the cables with large differences between the measured values ​​and the design cable force values ​​are adjusted, and then the cables are adjusted sequentially from large to small. During the adjustment, the cable force values ​​of the respective tower cables are monitored in real time, and the adjustment is repeated cyclically based on the monitoring results until the deviation between the total cable force value and the design cable force value is within the design allowable range.

[0030] In step 6, during bridge monitoring and TMD frequency tuning, after the bridge deck construction is completed and the cables are finally tuned, the frequency of the entire bridge is measured in a unified manner, including the following steps:

[0031] Step (1) Complete the bridge deck construction and adjust the cables of the entire bridge; Step (2) Deploy sensors in the sensitive area; Step (3) Measure the acceleration response of the pedestrian bridge under environmental excitation and impact load; Step (4) Determine the dynamic characteristics of the pedestrian bridge using FFT or PSD spectrum; Step (5) Adjust the TMD frequency; Step (6) Repeat steps (3), (4) and (5) until the natural frequency of the TMD is consistent with the natural frequency of the bridge body.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention is scientifically and rationally designed. It addresses the problem of insufficient stiffness and unmet vertical natural frequency requirements of single-sided single-cable-stayed bridges with tapered variable cross-section steel box girders. By utilizing finite element simulation analysis technology, it systematically analyzes the dynamic characteristics and sensitive frequency range under different load conditions and walking conditions. By setting up vertical and lateral TMD damping devices, it ensures that pedestrian comfort reaches the optimal level, thus guaranteeing the safety and comfort of the bridge.

[0034] This invention utilizes finite element analysis software for simulation calculations, simulating the changes in structural displacement, cable force, and internal forces during construction, and providing theoretical data for each construction stage to guide specific construction control work. Simultaneously, relevant calculation parameters are adjusted according to the actual conditions of the construction site, making the calculation model more closely approximate the actual structural state and ensuring that the theoretical data better reflects the actual structural response.

[0035] This invention addresses the pedestrian vibration comfort of a cable-stayed bridge employing a TMD (Transient Damping) vibration control scheme. Regarding vertical vibration comfort: optimal comfort levels are maintained under low and medium crowd density conditions. Only under extremely high crowd density (4.6 people / m²) loads (GK10 condition) is the comfort level acceptable; otherwise, it is at the optimal level. Regarding lateral vibration comfort: After adding a lateral TMD, optimal comfort is maintained under loads ranging from low to extremely high crowd density. Therefore, by evaluating and optimizing the TMD scheme based on comfort, the problem of human-induced vibration can be effectively solved, ensuring the comfort and safety of the structure during normal operation. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the full bridge line model of the present invention. Figure 2 This is a schematic diagram of the tapered variable cross-section box girder line model of the present invention. Figure 3 This is a schematic diagram of the Rhino model of the present invention. Figure 4 This is a schematic diagram of the three-dimensional picking of control point coordinates in this invention.

[0037] Figure 5 This is a schematic diagram showing the comparison and layout of the three-dimensional measured data of the control point coordinates of the present invention.

[0038] Figure 6 This is a schematic diagram of the 3000×2500 standard section of the present invention. Figure 7 This is a planar schematic diagram of the 3000×2500 standard section of the present invention.

[0039] Figure 8 for Figure 7 Schematic diagrams of the elevations in the AA and BB directions (1m support section).

[0040] Figure 9 for Figure 7 Schematic diagrams of the elevations in the AA and BB directions (3m support section).

[0041] Figure 10 for Figure 7 Schematic diagrams of the elevations in the AA and BB directions (4m support section).

[0042] Figure 11 This is a schematic diagram of the top of the temporary support of the present invention. Figure 12 This is a schematic diagram of the temporary foundation plan layout of the present invention.

[0043] Figure 13 This is a schematic diagram of the temporary foundation facade structure of the present invention. Figure 14 This is a schematic diagram of the embedded part structure of the present invention.

[0044] Figure 15 This is a stress analysis diagram of the cable tower of the present invention. Figure 16 This is a stress analysis diagram of the main bridge box girder of the present invention.

[0045] Figure 17 This is a schematic diagram of the first-order vertical vibration mode of the present invention. Figure 18 This is a schematic diagram of the second-order vertical vibration mode of the present invention.

[0046] Figure 19 This is a schematic diagram of the third vertical vibration mode of the present invention. Figure 20 This is a schematic diagram of the second-order lateral vibration mode of the present invention.

[0047] Figure 21 This is a schematic diagram of the third-order lateral vibration mode of the present invention. Figure 22 This is a schematic diagram of the fourth lateral vibration mode of the present invention.

[0048] Figure 23 This is a schematic diagram showing the location where the dynamic load is applied to the continuous walking node in this invention.

[0049] Figure 24 This is a schematic diagram of the location where the dynamic load is applied at the node of the group in this invention.

[0050] Figure 25 This is a schematic diagram of the location where the dynamic load is applied at the node of the group in this invention.

[0051] Figure 26 This is a schematic diagram showing the location where the dynamic load is applied to the multi-person jumping node in this invention.

[0052] Figure 27 This is a cloud map of the vertical absolute acceleration of the bridge deck under the GK8 working condition of this invention.

[0053] Figure 28 This is a cloud map of the vertical absolute acceleration of the bridge deck under the GK9 working condition of this invention.

[0054] Figure 29 This is a cloud map of the vertical absolute acceleration of the bridge deck under the GK10 working condition of this invention.

[0055] Figure 30 This is a cloud map of the vertical absolute acceleration of the bridge deck under the GK33 working condition of this invention.

[0056] Figure 31 This is a contour map of the bridge deck's lateral absolute acceleration under the LGK3 working condition of this invention.

[0057] Figure 32 This is a contour map of the bridge deck's lateral absolute acceleration under the LGK4 working condition of this invention.

[0058] Figure 33 This is a contour map of the bridge deck's lateral absolute acceleration under the LGK5 working condition of this invention.

[0059] Figure 34 This is a schematic diagram of the vertical TMD installation of the present invention. Figure 35This is a schematic diagram of the horizontal TMD installation of the present invention.

[0060] Figure 36 This is a schematic diagram comparing the absolute acceleration response of the most unfavorable node in the GK8 of this invention.

[0061] Figure 37 This is a schematic diagram comparing the absolute acceleration response of the most unfavorable node in the GK9 of this invention.

[0062] Figure 38 This is a schematic diagram comparing the absolute acceleration response of the most unfavorable node in the GK10 of this invention.

[0063] Figure 39 This is a schematic diagram comparing the absolute acceleration response of the most unfavorable node in the LGK5 of this invention.

[0064] Figure 40 This is a spatial overall model diagram of the present invention. Figure 41 This is a schematic diagram of the support node arrangement and elastic support of the present invention. Figure 42 This is a schematic diagram of the segmented loading of the cross diaphragm reinforcement according to the present invention. Figure 43 This is a schematic diagram of the load loading of the TDM node in this invention.

[0065] Figure 44 This is a schematic diagram of the beam end counterweight (KN / m) of the present invention. Figure 45 This is a schematic diagram of the second-phase constant load segmented loading of the present invention.

[0066] Figure 46 This is a schematic diagram of the deformation (mm) of the main beam of the completed bridge according to the present invention (adjusted cable force).

[0067] Figure 47 This is a schematic diagram of the bridge tower top offset (mm after adjustment of cable force) according to the present invention.

[0068] Figure 48 This is a schematic diagram of the P4 cable force (KN) after the frame is disassembled according to the present invention.

[0069] Figure 49 This is a schematic diagram of the cable force (KN) of the P4 tower after cable adjustment according to the present invention.

[0070] Figure 50 This diagram illustrates the process of using a truck crane and manual labor to hoist the cable reel to the bridge deck, as per the present invention.

[0071] Figure 51 This is a schematic diagram of the fixed end (connecting to the tower end) of the hoisting cable of the present invention near the tower.

[0072] Figure 52 This is a schematic diagram of the installation and fixing of the crane and the aerial work platform in this invention.

[0073] Figure 53This is a schematic diagram of the installation of the cable adjustment end (connecting beam end) of the crane and chain hoist according to the present invention.

[0074] Figure 54 This is a schematic diagram illustrating the installation of all cables and hangers in this invention.

[0075] Figure 55 This is a schematic diagram of the sensor and monitoring point arrangement across the entire bridge in this invention. Figure 1 .

[0076] Figure 56 This is a schematic diagram of the sensor and monitoring point arrangement across the entire bridge in this invention. Figure 2 .

[0077] Figure 57 This is a schematic diagram of the tensioning cable and jack of the present invention.

[0078] Figure 58 This is a schematic diagram of the deformation adjustment of the upper part of the bracket of the present invention. Figure 59 This is a schematic diagram of the suspended single-cable-stayed steel bridge of the present invention. Detailed Implementation

[0079] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0080] like Figure 1-59 As shown, this invention provides a construction method for a suspended single-cable-stayed steel bridge. It utilizes AutoCAD and Rhino software to create a 1:1 model. Taking into account the site environment, construction workflow, hoisting equipment selection, traffic management, and other factors, a temporary support system is rationally arranged, and processing and installation segments are divided. Segment information is input into a unified model, which outputs detailed processing drawings, along with the coordinates and elevation data of the control points for each installation segment. On-site segmented hoisting is performed, using the same model as the processing method to output spatial parameters for the installation control points. Furthermore, the three-dimensional coordinate data from the on-site measured interface is imported into the model for secondary alignment optimization, eliminating accumulated errors and improving on-site installation accuracy. The specific details of this invention are as follows:

[0081] I. 3D modeling.

[0082] The 3D coordinate parameters from the design drawings are imported into CAD and curve-fitted to create a line model. This line model is then imported into Rhino for detailed refinement. During the drawing, fabrication, and installation processes, the CAD model is uniformly exported from the Rhino model to ensure consistent control point data. During construction, the fabricated and installed entities are re-measured, and the data is returned to the CAD model for 3D comparison. Adjustments are made based on the comparison results to ensure the installation accuracy of the curved, thin, irregularly shaped steel box girder. Figures 1-5 As shown, the schematic diagrams are, in order, a schematic diagram of the full bridge line model, a schematic diagram of the tapered variable cross-section box girder line model, a schematic diagram of the Rhino model, a schematic diagram of the three-dimensional acquisition of control point coordinates, and a schematic diagram of the comparison and layout of the three-dimensional measured data of control point coordinates.

[0083] II. Prefabricated temporary support system.

[0084] 1. Temporary Support Design. The support frame is designed as a round tube support frame, made of Q235B material. The uprights are made of round tubes Φ325*10, and the horizontal and diagonal supports (diagonal web members) are made of round tubes Φ150*10. The support frame dimensions are 2.5m*3m. Standard support frame sections are manufactured in three lengths: 1m, 3m, and 4m for easy assembly and welding on-site according to the actual placement height. All nodes within the support frame sections are connected using flanges for easy installation and disassembly. The horizontal supports and uprights use semi-penetration welds with a penetration depth of 0.8t and a weld size of not less than 0.75t and not less than 8mm. The welds at the diagonal support connections are grade III fillet welds with a weld size of not less than 8mm. Stiffening plates with a thickness of 12mm and dimensions of 150*200*16mm are installed at the column bases and flange connections. Figure 6-10 As shown, the following are, in order: a schematic diagram of the 3000×2500 standard section of the present invention, a plan view of the 3000×2500 standard section of the present invention, an elevation view of the 1m support standard section of the present invention, an elevation view of the 3m support standard section of the present invention, and an elevation view of the 4m support standard section of the present invention.

[0085] The temporary scaffolding is connected to customized fixtures, mainly including a transfer beam, elevation stools, and limiting blocks. The transfer beam has a size no smaller than HM294×200×8×12. The elevation stool support uprights are made of P159×8 round tubes, and the connecting horizontal and diagonal bars are made of P140×8 round tubes. The limiting blocks are made of spliced ​​steel plates with plumb lines on the limiting surfaces. The transfer beam, elevation stools, limiting blocks, and scaffolding columns are all welded together. Figure 11 The diagram shown is a schematic representation of the top of the temporary support structure of the present invention.

[0086] The temporary support frame is expanded with an enlarged concrete foundation. The foundation dimensions for a single support frame on the main bridge are 3.5m × 4.0m × 0.5m. The main bridge supports are connected by welding 700×700×20mm embedded parts. C30 concrete is used, with a single layer of bidirectional C16@150 steel mesh at the bottom. A 10cm thick C20 concrete pad is placed under the support foundation. Depending on the bridge width and site conditions, both long-side splicing and short-side splicing types are used. The foundation dimensions for the long-side splicing double-row support frame are 6.7m × 4.0m × 0.5m, and for the short-side splicing double-row support frame, they are 7.7m × 3.5m × 0.5m. Figure 12-14 The diagram shown is a temporary basic schematic diagram of the present invention.

[0087] 2. Temporary Scaffold Construction Process. Based on the scaffold's plan position, the foundation area is located and marked out. The scaffold foundation is constructed according to the geological survey report and actual site conditions, excavating down to the silty clay layer as the bearing layer (bearing capacity characteristic value 160 kPa). Then, standard scaffold sections are hoisted and firmly welded to the embedded plates at the bottom, with a weld length of no less than 200 mm on each side. Standard sections are connected using flange bolts for easy disassembly later. Next, customized tooling is fabricated. The 3D coordinates of the scaffold support points are exported from the 3D model. The elevation bench positions are located on the transfer beam using planar coordinate data, and the lengths of the uprights and diagonal braces are determined using elevation data. Similarly, single-sided limiting blocks for the main bridge are fabricated and welded to the transfer beam. Finally, the entire tooling is hoisted and the scaffold columns are welded and fixed to the transfer beam. Before the main bridge is hoisted, the elevation bench height is measured and fine-tuned. Figure 58 As shown, customized tooling is connected to the upper part of the temporary support, mainly including a transfer beam, elevation stool, and limiting block. The height of the steel elevation stool is set to: theoretical height + 20mm, and not less than 350mm. A 50t screw jack is placed next to each support point, and the screw jack is positioned according to the elevation data of the completed bridge deck. A secondary elevation section (lightweight) is constructed based on the clearance distance between the original elevation stool and the steel box girder, and the required elevation is achieved by adding steel plates, etc.

[0088] III. Overall Stress Analysis of the Bridge

[0089] 1. Pre-construction analysis. The tapered variable cross-section steel box girder is affected by its own weight and unilateral diagonal tension, resulting in complex stresses within the box. During construction, the girder may experience deformations such as settlement, displacement, and torsion. The finite element analysis software Midas is used to model the entire bridge for numerical simulation and analysis. For example... Figure 15 and 16 The figures shown are the stress analysis diagrams of the cable tower and the main bridge box girder of the present invention, respectively.

[0090] 2. Adjustments to the on-site hoisting process of the main bridge steel box girder. The box girder hoisting process is as follows: temporary support installation for the steel box girder → steel box girder hoisting → welding → cable tensioning system conversion → support removal → paint touch-up. Based on calculation results, the stress distribution of the main bridge's irregularly shaped steel box girder during construction using temporary supports was fully understood. To ensure the bridge's final alignment, the cable force values ​​were determined through simulation to ensure that the alignment meets design requirements after the main bridge is closed and unloaded.

[0091] By comparing design parameters and conducting simulation calculations during the construction phase, the corresponding pre-camber was determined to establish the formwork elevation for the bridge construction phase. Based on the measured elevation, the previous phase was analyzed to determine the alignment and stress for the next phase, thus determining the formwork elevation. Simultaneously, for curved steel box girder bridge sections, the missing curved lower sealing plates at the interface positions were later added. Temporary connecting plates were installed every 300mm on the upper and lower top plates for docking and positioning, with the left and right contours corresponding one-to-one according to the fabrication positioning lines. After the entire bridge section was in place, the spatial positioning parameters of the later-added curved panels were measured and fed back into the detailed model. Based on the actual installation dimensions and design control curves, the spatial parameters of the later-added curved lower sealing plates were re-derived. Rigid material templates were used for individual template alignment, and then the missing curved lower sealing plates were installed. This ensures that the alignment of the cable-stayed bridge in its completed state meets the requirements for normal use. Meanwhile, by monitoring and collecting data on the cable-stayed bridge during the construction phase, we can ensure that the internal forces of the bridge are reasonable and the alignment is smooth after completion, minimize construction errors and workload, and ensure the smooth completion of the cable-stayed bridge.

[0092] IV. Analysis of pedestrian comfort and vibration reduction.

[0093] 1. Dynamic Characteristics Analysis. A refined 3D finite element model was established using Midas Civil to systematically analyze the human-induced vibrations of the bridge. The dynamic characteristics of the first 10 vertical and first 5 lateral vibration modes of the pedestrian cable-stayed bridge were calculated using eigenvalues. According to the comfort requirements of the standard, human-induced vibration comfort calculations are required for the vertical modal vibration frequencies in the range of 1.25Hz to 3.0Hz and the lateral modal vibration frequencies in the range of 0.5Hz to 1.2Hz.

[0094] Based on the dynamic characteristics, the vertical vibration frequency sensitivity range is from the first to the third order; the lateral vibration frequency sensitivity range is from the second to the fourth order. Comfort analysis was conducted using the sensitive modal frequencies determined according to EN03-2007 and CJJ69-201X standards. The dynamic characteristics (peak acceleration) of different groups of people under various conditions such as "continuous walking," "group walking," and "multi-person jumping" were analyzed to evaluate pedestrian comfort. Figure 17-19 As shown, the schematic diagrams are, in order, the first, second, and third vertical vibration modes of the invention. Figure 20-22As shown, the schematic diagrams are, in order, the second-order lateral vibration mode, the third-order lateral vibration mode, and the fourth-order lateral vibration mode of the invention.

[0095] 2. Definition of Crowd Load Cases. Due to differences in walking speed and stride length, pedestrians experience varying step frequencies, resulting in significant differences in pedestrian walking loads. These loads cannot be simulated using a single concentrated load. Considering the movement of multiple pedestrians, the load can be categorized into the following three main cases:

[0096] ① Random crowd walking: The simulation of random crowd load is based on the assumption that a continuous and stable flow of people is formed on the bridge surface, the crowd is evenly distributed on the pedestrian bridge surface, the pedestrians have the same walking frequency, and the phase angle is randomly distributed.

[0097] ② Walking in a small group: Walking in a small group refers to several people walking together at the same speed (ignoring differences in their stride frequency and stride length) from one end of a pedestrian bridge to the other.

[0098] ③Multiple people jumping: In order to fully consider the various pedestrian loads on the pedestrian bridge surface and ensure that the pedestrian bridge still meets the comfort requirements under unfavorable load excitation, the situation of a certain number of people jumping together at the same frequency is considered.

[0099] Referring to CJJ69-201X "Technical Specifications for Urban Pedestrian Overpasses and Underpasses (Draft for Comments)," the number of people per unit area at different pedestrian density levels corresponds to different activity states, as shown in Table 1. For example... Figure 23-26 The diagram shown illustrates the application of loads under different multi-person moving load conditions according to the present invention.

[0100] Table 1 Pedestrian Traffic Levels and Pedestrian Density

[0101]

[0102] 3. Human-induced vibration response and comfort evaluation.

[0103] According to the traffic level classification given in CJJ69-201X, and considering different walking conditions for different groups of people, with vertical bending frequencies f1 = 1.89Hz, f2 = 2.38Hz, and f3 = 2.62Hz, the continuous walking conditions for groups of people at traffic levels A, B, C, and D can be divided into GK1 to GK15; considering the influence of harmonics, the continuous walking conditions for groups of people at traffic levels C, D, and E can be divided into GK16 to GK29; only considering a certain number of people in a group walking at a certain frequency ( The vibration response when walking to the central region where the amplitude of each frequency mode is the largest (f1=1.89Hz, f2=2.38Hz, f3=2.62Hz, f4=1.50Hz, f5=1.70Hz) is considered. The walking condition in a group can be divided into GK30 to GK34. Considering a certain number of people jumping together at the same frequency (f1=1.89Hz, f2=2.38Hz, f3=2.62Hz, f4=1.50Hz, f5=1.70Hz) is divided into GK35 to GK39. Considering the lateral bending frequencies f1=0.872Hz, f2=0.987Hz, and f3=1.114Hz, and considering the crowd density under four traffic levels (A, B, C, and D), the continuous walking condition is divided into LGK1 to LGK15.

[0104] Based on the finite element analysis results and comfort levels and limits, in the scenario considered for multiple-person jumping, the crowd density is 0.2 people / m². 2 and 0.5 people / m 2 At that time, the vertical peak acceleration of the pedestrian bridge was at level CL1, indicating optimal comfort; the crowd density was 1.0 person / m². 2 At that time, the vertical peak acceleration level corresponding to the GK8 operating condition was all at CL2 level, and the comfort level was qualified; the crowd density was 1.5 people / m². 2 At that time, the vertical peak acceleration of GK9 was classified as CL3, resulting in unsatisfactory comfort; the population density was 4.6 people / m². 2 At that time, the vertical peak acceleration in condition GK10 was classified as CL3, resulting in unsatisfactory comfort. In the scenarios considered for group jumping, except for condition GK33, where the vertical peak acceleration was classified as CL2 and comfort was acceptable, the pedestrian bridge comfort was at its optimal level in all other conditions. In the scenarios considered for multiple jumpers, the pedestrian bridge comfort was at its optimal level in all conditions. Peak values ​​all occurred in section B of the pedestrian bridge. Figure 27-30 The figure shown is a vertical absolute acceleration cloud map of the non-optimal comfort condition of the present invention.

[0105] Based on the finite element analysis results and comfort levels and limits, the population density is 0.2 people / m². 2 and 0.5 people / m 2At that time, the lateral peak acceleration of the pedestrian bridge was at level CL1, indicating optimal comfort; the crowd density was 1.0 person / m². 2 At that time, the lateral peak acceleration of the LGK3 was classified as CL3, resulting in unsatisfactory comfort; the crowd density was 1.5 people / m². 2 At that time, the lateral peak acceleration of the LGK4 was classified as CL3, indicating that its comfort level was unsatisfactory; the population density was 4.6 people / m². 2 At that time, the lateral peak acceleration of the LGK5 under operating conditions was determined to be at level CL3, resulting in a failure to meet comfort standards. The peak values ​​all occurred in the area where sections B and C of the pedestrian bridge met. Figures 31-33 The figure shown is a lateral absolute acceleration cloud map of the non-optimal comfort condition of this invention.

[0106] 4. Human-Induced Vibration Control and Evaluation. When the vibration comfort of a pedestrian bridge fails to meet design requirements, dampers are used to increase structural damping and control vibration comfort. Because pedestrian cable-stayed bridges have dense modalities, with three vertical modes in the sensitive frequency band, multimodal vibration control is necessary. Based on the actual situation, a vertical TMD system is formed by arranging dampers for vertical vibration control throughout the bridge, and a horizontal TMD system is formed by arranging dampers for lateral vibration control. For example... Figure 34 and 35 The diagram shown is a schematic diagram of the TMD installation of the present invention.

[0107] After installing the TMD vibration damping device, a second human-induced vibration time history analysis was conducted on the Shulong Road pedestrian cable-stayed bridge. The same analysis conditions as before the installation of the TMD device were used. The peak vertical acceleration of the model nodes obtained from the time history analysis was compared with the comfort range specified in the standards. The comfort results after vibration reduction control are as follows: Figures 36-39 As shown.

[0108] In summary, after adding a vertical TMD, the population density under continuous walking conditions is only 4.6 people / m². 2 At that time, the vertical peak acceleration of the GK10 under operating conditions was at level CL2, and the comfort level was acceptable; the density of other people was 0.2 people / m². 2 0.5 people / m 2 1.0 person / m 2 1.5 people / m 2 The peak vertical acceleration was at CL1 level, indicating optimal comfort. The peak vertical acceleration was also at CL1 level in both group jumping and multi-person jumping scenarios, indicating optimal comfort.

[0109] After adding a lateral TMD (Transient Damping Device), the crowd density under continuous walking conditions is 0.2 people / m². 2 0.5 people / m 2 1.0 person / m 2 1.5 people / m2 4.6 people / m 2 The peak lateral acceleration was at CL1 level, indicating optimal comfort.

[0110] V. Installation and tensioning of stay cables.

[0111] 1. Establish a three-dimensional finite element model. Use MIDAS / CIVIL to analyze the pylons, main beams, stay cables, temporary supports, etc. The geometry reflects the final alignment of the bridge, accurately reflecting technical parameters such as structural stiffness, section properties, structural mass, and non-structural mass, in order to reasonably analyze the actual mechanical behavior of the structural system. The spatial model is as follows: Figure 40 As shown.

[0112] Constraints: The pylon adopts a tower-beam fixed connection, with unidirectional supports at the beam end piers and unidirectional movable supports at the auxiliary piers of beam segment C. The support structure is simulated based on the actual temporary support locations.

[0113] Load Application: For the main girder dead load, due to the bridge's unique tapered variable cross-section steel box girder, the weight of the transverse diaphragms varies significantly with the cross-section. Therefore, after calculating the weight of the transverse diaphragms segment by segment in the beam element model, a uniformly distributed load is applied to different beam segments. In addition to the transverse diaphragms, the beam segments are pre-installed with TMDs (Transverse Dampers), and the weight of the TMDs is applied to the corresponding nodes using nodal loads. C20 concrete is poured at the beam ends for ballast, and the model is then subjected to ballast loads. (Example: ...) Figures 42-44 As shown, the diagrams are, in order, a schematic diagram of the segmented loading of the transverse diaphragm, a schematic diagram of the TDM node load loading, and a schematic diagram of the beam end counterweight (KN / m) of the present invention.

[0114] The second-phase dead load includes drainage structures, railings, and bridge deck pavement. Railing calculations are based on weight intensity per linear meter; the average pavement layer thickness is 55mm, and load calculations are performed segmentally considering variations in beam width. The second-phase dead load calculation is as follows: Figure 45 As shown.

[0115] 2. Simulation and analysis of the tensioning process. (1) Optimization of cable force in the completed bridge. The main beam of this bridge was not manufactured with pre-camber in mind, and was manufactured using the ideal bridge alignment. The main beam was hoisted and installed on the support and finally welded. The simply supported main beam had an initial deflection, which was converted into a continuous beam after welding, i.e., the main beam was in a stress-free state; similarly, the initial state of the tower was an ideal vertical state. The ideal bridge state after simulating cable tensioning and applying all the secondary dead loads was determined, and the corresponding cable force was the target cable force in the completed bridge. The simulation results of the bridge deformation and the optimization of the cable force values ​​are as follows: Figure 46 and Figure 47As shown. (2) Simulation optimization of cable tensioning sequence. Cable tensioning is carried out in two steps. The first step is to symmetrically tension the cables to 100% of the design value by using a graded loading method after the cables of the tower are hung. Usually, three levels of loading are used: 30%, 80%, and 100% of the design value. After each level of loading is completed, a 5-minute pause is required for monitoring data collection and simulation analysis. The second step is to adjust the cable force to the design value according to the monitoring simulation analysis results after the bridge deck laying, lighting and ancillary facilities are completed.

[0116] The tensioning sequence for single-tower cables: In principle, cables for a single tower should be tensioned from bottom to top and from shortest to longest, with one pair of stay cables tensioned symmetrically each time. Because the first pair of stay cables on a curved bridge is located on the side of the tower, the tensioning of subsequent cables has a significant impact on the cable force of the first pair. The first pair of cables may experience negative cable force during the tensioning process. Therefore, tensioning should begin from the second pair of cables, proceeding from bottom to top, with the first pair tensioned last. Simulation analysis shows that some cables do not reach the designed cable force value for the bridge and need to continue tensioning; some cables exceed the designed cable force value and need to be adjusted and released. For example... Figures 48-49 The figures shown are schematic diagrams of the P4 cable force (KN) after dismantling the frame and the P4 tower cable force (KN) after cable adjustment, respectively.

[0117] 3. Cable Deployment and Installation. The deployment and installation of the cables are mainly carried out using a mobile crane, aerial work platform, and chain hoist in coordination. During the process, the crane provides vertical force, the chain hoist provides horizontal force, and the aerial work platform provides the working platform. Careful coordination and command are essential to avoid collisions at height. Figures 50-54 As shown, the specific installation steps are as follows: 1. Hoist the cable reel to the bridge deck, with the truck crane assisting manual cable spreading; 2. Hoist the fixed end of the cable (the end connected to the tower) close to the tower; 3. The crane and the aerial work platform work together to install and fix the cable; 4. The crane and the chain hoist work together to install the cable adjustment end (the end connected to the beam); 5. Repeat the above steps to complete the installation of all cables.

[0118] 4. Cable Tensioning and Monitoring. Due to system conversion involved in the construction of this bridge, a qualified unit should be commissioned to monitor the project during construction. The specific monitoring content and required measures will be based on the monitoring unit's monitoring plan. On-site tensioning should be guided by real-time on-site monitoring data and strictly carried out according to the instructions issued by the monitoring unit throughout the entire process. Cable tensioning should be conducted synchronously with monitoring throughout the entire process. Figures 55-57 As shown, the specific steps are as follows: 1. Deploy sensors and monitoring points throughout the bridge; 2. Install tensioning fixtures and jacks; 3. Load the cables at three levels: 30%, 80%, and 100%, and monitor them simultaneously; 4. Monitor the stress and strain values ​​of the towers and main bridge, as well as the cable force values, for every 2-3 pairs of cables tensioned; 5. Analyze the monitoring data to guide the adjustment of the tensioned cables; 6. Repeat the above steps to complete the tensioning of the entire cable; 7. Monitor the entire bridge to guide the tensioning of the next tower cable.

[0119] 5. Phase II Dead Load and Cable Adjustment. After the completion of the Phase II bridge deck system (bridge deck pavement, railings and handrails), the cable forces of the entire bridge will be adjusted to the design cable forces based on the measured cable force values. Priority will be given to adjusting the cable forces with the largest differences between the measured values ​​and the design values ​​of the completed bridge, and then adjusting them sequentially from the largest to the smallest. During the adjustment, the cable force values ​​of the respective towers must be monitored in real time, and the adjustment will be carried out cyclically based on the monitoring results, until the deviation between the total cable force value of the entire bridge and the design value of the completed bridge is within the allowable range of the design.

[0120] 6. Bridge Completion Monitoring and TMD Frequency Tuning. The structural system of a single-sided, single-cable-stayed bridge is unique, with the main girder employing a distinctive tapered variable cross-section steel box girder, resulting in a complex stress state after completion. A unified measurement of the entire bridge's frequencies is required after the bridge deck construction is completed and the cables are finally adjusted. The specific steps for unified frequency measurement of the entire bridge are as follows: 1. Complete bridge deck construction and adjust all cables; 2. Deploy sensors in sensitive areas, using unidirectional and tridirectional sensors; 3. Measure the pedestrian bridge's acceleration response under environmental excitation and impact loads; 4. Determine the pedestrian bridge's dynamic characteristics using FFT or PSD spectra; 5. Adjust the TMD frequency; 6. Repeat steps 3, 4, and 5 until the TMD natural frequency matches the bridge's natural frequency.

[0121] This invention uses AutoCAD and Rhino software to create a 1:1 model. Taking into account the site environment, construction workflow, hoisting equipment selection, traffic management, and other factors, a temporary support system is rationally arranged, and processing and installation segments are divided. Segment information is input into a unified model, which outputs detailed processing drawings, along with the coordinates and elevation data of the control points for each installation segment. On-site segmented hoisting uses the same model as the processing system to output spatial parameters for the installation control points. Furthermore, 3D coordinate data from the on-site measured interface is imported into the model for secondary alignment optimization, eliminating accumulated errors and improving on-site installation accuracy.

[0122] This invention utilizes finite element method (FEM) software for construction-period analysis based on time-varying mechanics to obtain predicted and target values ​​for structural performance. Based on construction analysis and predictions, deformation values ​​at each installation stage are obtained. Reverse deformation is applied during processing and installation to ensure the bridge's alignment and mechanical state meet design requirements, guaranteeing an aesthetically pleasing appearance and good landscape effect. Furthermore, this invention uses FEM software to analyze the vertical and lateral vibration modes of human-induced vibrations. By comparing the vertical peak acceleration characteristic curves under different load conditions and walking scenarios, and considering the optimal comfort level requirements specified in the standards, vertical and lateral TMD damping devices are installed to ensure the comfort and safety of the bridge structure during normal operation meet design requirements, resulting in a good pedestrian comfort experience.

[0123] This invention uses a finite element model to simulate the stress and strain of the tower, main bridge, and cables at various stages, including cable hanging, tensioning, support removal, and secondary dead load construction (bridge deck paving, railings, etc.). This allows for the analysis and calculation of the optimal cable tensioning sequence and cable force value, enabling one-time tensioning and cable adjustment. This significantly improves construction progress while ensuring construction safety during system conversion.

[0124] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the scope of the patent. Any modifications or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but which still solve the same technical problem as the present invention, should be included within the scope of protection of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the scope of patent protection of the present invention.

Claims

1. A construction method for a suspended single-cable-stayed steel bridge, characterized in that, Includes the following steps: Step 1: 3D modeling of the cable-stayed bridge; Step two, temporary scaffolding system construction; Step 3: Overall stress analysis of the cable-stayed bridge; Step 4: Vibration reduction analysis for pedestrian comfort on cable-stayed bridges; Step 5: Installation and tensioning of the stay cables; In step one, when modeling the cable-stayed bridge in 3D, the 3D coordinate parameters from the design drawings are imported into CAD and curve-fitted to form a line model. The line model is then imported into Rhino for detailed refinement. During the drawing, processing, and installation, the CAD model is uniformly exported from the Rhino model to ensure consistent control point data. During construction, the processed and installed entities are re-measured, and the data is returned to the CAD model for 3D comparison. Adjustments are made based on the comparison results to ensure the installation accuracy of the curved, thin, irregularly shaped steel box girder. In step four, during the pedestrian comfort vibration reduction analysis of the cable-stayed bridge, a 3D refined finite element model was established using MidasCivil to systematically analyze the human-induced vibration of the bridge. The dynamic characteristics of the first 10 vertical and first 5 lateral vibration modes of the pedestrian cable-stayed bridge were calculated using eigenvalues. According to the comfort requirements of the standard, the human-induced vibration comfort needs to be verified when the vertical modal vibration frequency is in the range of 1.25Hz~3.0Hz and the lateral modal vibration frequency is in the range of 0.5~1.2Hz. Based on the dynamic characteristics, the vertical vibration frequency sensitivity range is from the first to the third order; the lateral vibration frequency sensitivity range is from the second to the fourth order. Comfort analysis was conducted based on the sensitive modal frequencies of each order determined according to EN03-2007 and CJJ69-201X standards. Based on the comfort analysis results, TMD vibration damping devices were adopted to increase the damping of the cable-stayed bridge structure and improve pedestrian vibration comfort. At the same time, 13 sets of TMD devices were reserved for final commissioning. In step five, the installation and tensioning of the stay cables includes the following steps: Step 1: Establish a three-dimensional finite element model; Step 2, simulation analysis of the tensioning process; Step 3, cable deployment and installation; Step 4, cable tensioning and monitoring; Step 5, Phase II dead load and cable adjustment; Step 6, Bridge Completion Monitoring and TMD Frequency Modulation; In step 1, when establishing the three-dimensional finite element model, MIDAS / CIVIL is used to analyze the pylon, main beam, stay cables and temporary supports; the geometry reflects the final alignment of the bridge, accurately reflects the structural stiffness and cross-sectional properties, structural mass and non-structural mass technical parameters, so as to reasonably analyze the actual mechanical behavior of the structural system; Constraints during the process: The pylon adopts a tower-beam fixed connection, with unidirectional support at the beam end piers and unidirectional movable support at the auxiliary piers of beam segment C; the support is simulated according to the actual temporary support position. Loads applied during the process: Main beam dead load: After calculating the weight of the transverse diaphragms in the beam element model, uniformly distributed loads are applied to different beam segments. Except for the transverse diaphragms, the beam segments are pre-installed with TMD vibration damping devices at the factory. The weight of the TMD vibration damping devices is loaded onto the corresponding nodes using nodal loads. C20 concrete is poured at the beam ends for ballast, and ballast loads are applied to the model. Secondary dead load: The secondary dead load includes drainage structures, railings and handrails, and bridge deck pavement. The railings are calculated based on the weight intensity per linear meter. The average thickness of the pavement layer is 55mm, and the load is calculated and applied in segments according to the width variation of different beam segments. In step 2, during the simulation analysis of the tensioning process, the cable force optimization of the completed bridge is first performed. Manufacturing pre-camber is not considered; an ideal bridge alignment is used for fabrication. The main beam is hoisted and installed on a support frame and finally welded. The simply supported main beam exhibits initial deflection, which is converted to a continuous beam after welding. Similarly, the initial state of the tower is an ideal vertical state. The ideal bridge state after simulating cable tensioning and applying all secondary dead loads is simulated, and the corresponding cable force is the target bridge cable force. Then, the cable tensioning sequence is simulated and optimized. Cable tensioning is performed in two steps. The first step, after the tower cables are hung, is symmetrically tensioned to 100% of the design value using a graded loading method. The tensioning process employs a three-stage loading method: 30%, 80%, and 100% of the design value. A five-minute pause is taken after each loading stage for monitoring data collection and simulation analysis. The second step involves adjusting the cable tension to the design value based on the monitoring and simulation analysis results after the bridge deck, lighting, and ancillary facilities are completed. The tensioning sequence for individual tower cables is from bottom to top and from shortest to longest, with one pair of stay cables tensioned symmetrically at a time. Tensioning begins from the second pair of cables and proceeds upwards, ending with the first pair. If simulation analysis indicates that some cables have not reached the designed bridge cable tension value, tensioning continues; if the cable tension of some cables exceeds the designed bridge cable tension value, cable release is implemented.

2. The construction method for a suspended single-cable-stayed steel bridge according to claim 1, characterized in that, In step two, when the temporary support system is erected, the support frame is designed as a round tube support frame made of Q235B material, and the uprights are made of Φ325 round tubes.

10. Horizontal and diagonal supports use Φ150 round tubes.

10. The support frame is 2.5m in size. The support frame is manufactured in standard sections of 1m, 3m, and 4m. All nodes within the support frame sections are connected using flanges for easy installation and disassembly. The horizontal supports and columns are connected using semi-penetration welds with a penetration depth of 0.8t and a weld size of not less than 0.75t and not less than 8mm. The diagonal supports are connected using fillet welds of grade III with a weld size of not less than 8mm. Stiffening plates with a thickness of 12mm and a dimension of 150mm are installed at the column base and flange connections. 200 16mm; The upper part of the temporary support is connected to customized fixtures, which include a transfer beam, an elevation stool, and a limiting block. The transfer beam has a specification of not less than HM294×200×8×12. The support uprights of the elevation stool are made of round tube P159×8, and the connecting horizontal and diagonal bars are made of round tube P140×8. The limiting block is made of steel plate splicing, and the limiting surface is plumb. The transfer beam, elevation stool, limiting block, and support column are connected to each other by welding. The temporary supports are constructed with enlarged concrete foundations. The dimensions of a single enlarged concrete foundation for the main bridge support are 3.5m × 4.0m × 0.5m. The main bridge supports are connected by welding 700×700×20mm embedded parts. The concrete used for the enlarged concrete foundations is C30, and a single layer of bidirectional C16@150 steel mesh is installed at the bottom. A 10cm thick C20 concrete pad is installed below the enlarged concrete foundations of the supports. Depending on the bridge width and the site's geographical environment, long-side splicing type and short-side splicing type are set up. The foundation dimensions are 6.7m × 4.0m × 0.5m for the long-side splicing double-row support enlarged concrete foundation and 7.7m × 3.5m × 0.5m for the short-side splicing double-row support foundation.

3. The construction method for a suspended single-cable-stayed steel bridge according to claim 1, characterized in that, During the construction of the temporary support system, the area of ​​the expanded concrete foundation of the support was marked out according to the plan position of the temporary support. Based on the geological survey report and the actual site conditions, the construction of the expanded concrete foundation of the support was carried out, and the silty clay layer with a bearing capacity characteristic value of 160 kPa was excavated as the bearing layer. Then, the standard sections of the support were hoisted and welded firmly to the embedded plate at the bottom. The weld length on each side was not less than 200 mm. The standard sections were connected by flange bolts for easy disassembly later. Then, customized tooling was made, and the three-dimensional coordinates of the support support points were exported from the three-dimensional model. The position of the elevation stool uprights on the transfer beam was located by means of the planar coordinate data, and the length of the uprights and diagonal braces was determined by the elevation data. Similarly, the single-sided limiting blocks of the main bridge were made and welded to the transfer beam. Finally, the tooling was hoisted as a whole and the support columns were welded and fixed to the transfer beam. Before the main bridge was hoisted, the height of the elevation stool was measured and fine-tuned.

4. The construction method for a suspended single-cable-stayed steel bridge according to claim 1, characterized in that, In step three, during the overall stress analysis of the cable-stayed bridge, the finite element analysis software Midas is used to model the entire cable-stayed bridge and perform numerical simulation and analysis. This is to fully understand the stress distribution of the main bridge's irregular steel box girder during the construction process using temporary supports. To ensure the bridge's alignment, the cable force values ​​are determined through simulation to ensure that the alignment meets design requirements after the main bridge is closed and unloaded. By comparing design parameters, simulation calculations are performed during the construction phase to obtain the corresponding pre-camber, which is used to determine the formwork elevation during the bridge construction phase. Based on the measured elevation, the previous phase is analyzed to determine the alignment and stress of the next phase, thereby determining the formwork elevation. This ensures that the alignment of the cable-stayed bridge in its completed state meets the needs of its normal use. Through data monitoring and collection during the construction phase, the internal forces of the cable-stayed bridge are ensured to be reasonable and the alignment smooth after completion, reducing construction errors and workload, and ensuring the successful completion of the cable-stayed bridge.

5. The construction method for a suspended single-cable-stayed steel bridge according to claim 1, characterized in that, In step 3, the cable deployment and installation are carried out using a mobile crane, an aerial work platform, and a chain hoist in coordination. The crane provides vertical force, the chain hoist provides horizontal force, and the aerial work platform provides the working platform. The process includes the following steps: Step a: Hoist the cable reel to the bridge deck, with the truck crane assisting manual labor in spreading the cable; Step b: The fixed end of the hoisting cable is brought close to the tower; Step c: The crane and the aerial work platform work together to install and secure the cables; Step d: The crane and chain hoist work together to install the cable adjustment end; Step e, repeat steps a, b, c and d to complete the installation of all cable hangers; In step 4, during cable tensioning and monitoring, the entire tensioning process is guided by real-time on-site monitoring data; this includes the following steps: Step (a): Arrange sensors and monitoring points across the entire bridge; Step (b): Install the tensioning cable and jacks; Step (c): The cable is loaded in three levels: 30%, 80%, and 100%, with simultaneous monitoring. Step (d): For every 2-3 pairs of cables tensioned, systematic monitoring of the stress and strain values ​​of the tower and main bridge, as well as the cable force values, shall be conducted. Step (e) involves analyzing monitoring data to guide adjustments to the tension of the already tensioned cables; Step (f), repeat steps (a), (b), (c), (d) and (e) to complete the tensioning of the entire cable; Step (g) involves full-bridge monitoring and control to guide the tensioning of the next cable.

6. The construction method for a suspended single-cable-stayed steel bridge according to claim 1, characterized in that, In step 5, during the second-phase dead load and cable adjustment, after the second-phase bridge deck system construction, including the bridge deck, railings, and handrails, is completed, the cable force of the entire bridge is adjusted to the design cable force based on the measured cable force values. First, the cables with large differences between the measured values ​​and the design cable force values ​​are adjusted, and then the cables are adjusted sequentially from large to small. During the adjustment, the cable force values ​​of the respective tower cables are monitored in real time, and the adjustment is repeated cyclically based on the monitoring results until the deviation between the total cable force value and the design cable force value is within the design allowable range. In step 6, during bridge monitoring and TMD frequency tuning, after the bridge deck construction is completed and the cables are finally tuned, the frequency of the entire bridge is measured in a unified manner, including the following steps: Step (1): Complete the bridge deck construction and adjust the cables of the entire bridge; Step (2): Arrange sensors in the sensitive area; Step (3), acceleration response of pedestrian bridge under environmental excitation and impact load; Step (4): Determine the dynamic characteristics of the pedestrian bridge using FFT or PSD spectra; Step (5), adjust the TMD frequency; Step (6), repeat steps (3), (4) and (5) until the natural frequency of the TMD matches the natural frequency of the bridge body.

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