Method for determining measurement opportunity of ballastless track control network of large-span cable-stayed bridge

Abstract

The invention provides a method for determining the measurement opportunity of a ballastless track control network of a large-span cable-stayed bridge. The method comprises the steps that settlement observation is conducted after a bridge foundation is constructed till the standard requirement is met; retesting the encrypted line accurate measurement network and the level base point control network until the precision reaches the standard; adjusting the line shape of the main beam to a design tolerance range by taking the retest net as a reference; and analyzing main beam linear monitoring data, and determining a time period in which the linear change rate is continuously lower than a preset threshold value as a relatively stable zero time window as an optimal measurement opportunity. The method effectively relieves the influence of the settlement difference of the main pier, side pier and auxiliary pier foundations on the control net, solves the problem of building the coordinate reference of the bridge floor of the highway-railway dual-purpose bridge, avoids the control net remeasurement caused by the linear adjustment of the steel beam, remarkably reduces the interference of environmental factors such as temperature and wind power on the measurement precision, and improves the measurement accuracy. A high-precision and high-reliability control network reference is provided for ballastless track construction, and standardization and high efficiency of the measurement process are achieved.

Description

Technical Field

[0001] This application relates to the field of engineering construction auxiliary technology, and in particular to a method for determining the timing of measurement of the control network for the ballastless track of a long-span cable-stayed bridge. Background Technology

[0002] In China, the design of cable-stayed bridges with ballastless track structures has been widely adopted for high-speed railways or intercity passenger dedicated lines, and the spans are becoming increasingly larger. For example, the main span of the Chongqi Yangtze River Bridge on the North Yangtze River High-speed Railway is 400m, and the main span of the Hangzhou Bay Bridge reaches 450m.

[0003] Currently, for ordinary bridges, the control network for ballastless track can be measured after the settlement assessment of the underground engineering is passed, choosing a period of relatively stable external environment. However, for long-span cable-stayed bridges, the influencing factors are very complex, as follows: ① The inconsistent foundation design and load-bearing characteristics of the main piers, side piers, and auxiliary piers of long-span cable-stayed bridges lead to significant post-construction settlement impacting the ballastless track control network results, especially due to uneven settlement between piers and abutments; ② For bridges designed for both road and rail use or employing steel truss main girders, the bridge deck coordinate reference cannot rely solely on GNSS static measurement methods; ③ During the construction of the ballastless track control network, changes in the external environment cause constant variations in the plane, vertical alignment, and mileage of the main girder, resulting in dynamic changes in the three-dimensional spatial coordinates of the ballastless track control points; ④ The main girder alignment is influenced by multiple factors such as temperature, illumination, wind, and external loads, making finite element modeling of the main girder and ballastless track challenging. Multi-condition alignment measurements are required for bridge stiffness verification and finite element model correction.

[0004] To avoid the need for re-measurement of the ballastless track control network after its completion due to unstable settlement of the subgrade, insufficient measurement accuracy of the control network, and subsequent adjustments to the steel beam alignment, as well as the impact of changes in the external environment on the accuracy of the ballastless track control network during the measurement process, a comprehensive assessment is required regarding the timing of the ballastless track control network measurement for long-span cable-stayed bridges.

[0005] Therefore, the timing of the ballastless track control network layout for long-span cable-stayed bridges is more critical than that for ordinary bridges. It is necessary to provide a method for determining the timing of the ballastless track control network measurement for long-span cable-stayed bridges, so as to provide a high-precision control network for ballastless track construction. Summary of the Invention

[0006] To address the shortcomings or deficiencies mentioned in the background technology, this application provides a method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges. This method solves the problem that it is difficult to determine the timing of ballastless track control network measurements for long-span cable-stayed bridges in the prior art. Specifically, the measurement timing cannot be accurately determined due to unstable settlement of the subgrade, insufficient accuracy of the control network, and dynamic changes in the main beam alignment, leading to remeasurement of the control network and loss of accuracy.

[0007] This application provides a method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges, including the following steps: S1. After the bridge foundation is constructed, settlement monitoring shall be carried out at a preset cycle until the settlement data meets the preset stability criteria. S2. After the settlement data meets the preset stability criteria, the line precision measurement network and the leveling benchmark control network are re-measured and densified until the measurement results reach the preset accuracy index. S3. Using the re-measured and densified line precision measurement network and leveling benchmark control network as a reference, measure, compare and adjust the main beam alignment until the difference between it and the design alignment converges to the preset tolerance range. S4. After the main beam alignment adjustment is completed, the main beam alignment monitoring data is analyzed, and the time period in which the alignment change rate is continuously lower than the preset rate threshold is determined as the zero time window, which is used as the optimal time window for track construction control network measurement.

[0008] In some embodiments, the preset stability criterion includes: The settlement rate of the bridge foundation is lower than a preset rate threshold. The total settlement of the bridge foundation is lower than a preset total threshold. The differential settlement between adjacent piers is lower than the preset differential threshold.

[0009] In some embodiments, the re-measurement and densification of the line precision survey network and leveling benchmark control network until the measurement results reach the preset accuracy index includes: The CPI and CPII control points of the line precision measurement network are remeasured and their accuracy is evaluated until their point accuracy reaches the preset point accuracy index. The leveling benchmark control network of the line is re-measured and its accuracy is evaluated until its elevation accuracy reaches the preset elevation accuracy index.

[0010] In some embodiments, the re-measurement and densification of the line precision survey network and leveling benchmark control network until the measurement results reach the preset accuracy index further includes: After the positional accuracy of the CPI and CPII control points meets the requirements, the CPII control points on the bridge deck are densified based on them. After the elevation accuracy of the benchmark point meets the requirements, it is used as a reference to densify the bridge deck elevation densification points.

[0011] In some embodiments, the densification of the bridge deck CPII control points includes: At least one CPII control point is set up on the inner side of each main pier tower of the cable-stayed bridge; A pair of CPII control points are set directly above the fixed supports of the simply supported beams at both ends of the cable-stayed bridge, and the pair of control points maintains a preset distance.

[0012] In some embodiments, the densified measurement of the bridge deck CPII control points includes: For the CPII control points set on the simply supported beam, the GNSS static measurement method is used for observation, and the fine measurement network plane control points are used as the starting point for the indoor calculation. For the CPII control points located on the main pier tower, the precision traverse survey method was used for observation.

[0013] In some embodiments, the densification and measurement of the bridge deck elevation densification points include: The location and number of bridge deck elevation densification points correspond to the location and number of bridge deck CPII control points.

[0014] In some embodiments, the densification measurement of the bridge deck elevation densification points includes: The bridge deck elevation densification points and the line leveling benchmarks form a traverse leveling route. The connection measurement of the elevation densification points to the line leveling benchmarks in the traverse leveling route adopts the intermediate station method of trigonometric leveling, and the connection measurement of adjacent elevation densification point sections adopts second-order leveling.

[0015] In some embodiments, step S3 involves measuring, comparing, and adjusting the main beam profile until the difference between it and the designed profile converges to a preset tolerance range, including: S31. Establish a finite element model of the bridge structure and the ballastless track; S32. After the main beam is closed, the main beam alignment is continuously observed for a first preset duration. S33. Compare the observed main beam profile with the predicted profile of the finite element model, and use the measured profile as a benchmark to correct the finite element model through parameter inversion until the difference between the theoretical predicted profile of the corrected model and the measured profile is less than the first preset threshold. S34. After the second phase of dead load is applied, the main beam alignment is continuously observed for a second preset duration. S35. The observed main beam profile is compared with the predicted profile of the current finite element model again, and the finite element model is corrected by parameter inversion until the difference between the theoretical predicted profile of the corrected model and the measured profile is less than the second preset threshold. S36. Based on the final corrected finite element model, calculate and execute the adjustment amount of the main beam profile so that the difference between the adjusted main beam profile and the design profile falls within the preset tolerance range. S37. Based on the adjusted main beam alignment and the finite element model, simulate and calculate the track geometry parameters after the ballastless track is laid, and confirm that the track geometry parameters meet the accuracy standards for ballastless track laying.

[0016] In some embodiments, step S4, after the main beam alignment adjustment is completed, analyzes the main beam alignment monitoring data and determines the time period during which the alignment change rate is continuously lower than a preset rate threshold as the zero time window, which serves as the optimal time window for track construction control network measurement, including: S41. After the main beam alignment is adjusted, continuously monitor the longitudinal, transverse and vertical alignment of the main beam and obtain monitoring data on its changes over time. S42. Based on the monitoring data that changes over time, calculate the change in the main beam profile within a unit time interval, i.e., the rate of change in profile. S43. Analyze the monitoring data and identify that when the linear change rate of the main beam in the longitudinal, transverse and vertical directions is continuously lower than its respective preset rate threshold in at least one complete natural day cycle, then determine that the time period is a zero time window. S44. The zero time window is determined as the operation time for measuring the track construction control network.

[0017] The beneficial effects of the technical solution provided in this application include: This application provides a method for determining the timing of measurement of the control network for the ballastless track of a long-span cable-stayed bridge. The method includes conducting settlement observations at a preset cycle after the bridge foundation construction until the settlement data meets the preset stability criteria. After the settlement data meets the preset stability criteria, the line precision measurement network and the leveling benchmark control network are re-measured and densified until the measurement results reach the preset accuracy index. Based on the re-measured and densified line precision measurement network and leveling benchmark control network, the main beam alignment is measured, compared and adjusted until the difference between it and the design alignment converges to the preset tolerance range. After the main beam alignment adjustment is completed, the main beam alignment monitoring data is analyzed, and the time period in which the alignment change rate is continuously lower than the preset rate threshold is determined as the zero time window, which is used as the best time window for track construction control network measurement.

[0018] Therefore, the bridge settlement assessment met the design and specification requirements, effectively mitigating the impact of inconsistent foundation settlement of the main piers, side piers, and auxiliary piers of the long-span cable-stayed bridge on the ballastless track control network; the accuracy of the control network re-measurement and densification measurement met the specification requirements, successfully solving the problem of establishing the bridge deck coordinate benchmark for the dual-purpose road and rail bridge; the main beam alignment adjustment met the design requirements, completely avoiding the problem of re-measurement of the ballastless track control network caused by subsequent steel beam alignment adjustments; Furthermore, through in-depth analysis of the main beam alignment monitoring data, the time period in which the alignment change rate is consistently lower than the preset rate threshold is precisely determined as a relatively stable zero-time window, serving as the optimal observation window. This significantly reduces the interference of external environmental factors on measurement accuracy during the construction of the ballastless track control network. This scientifically determined measurement timing ensures the accuracy of data acquisition, provides a high-precision and high-reliability control network benchmark for ballastless track construction, and realizes the standardization and efficiency of the measurement process. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of a method according to an embodiment of this application; Figure 2 This is a schematic diagram of the bridge deck CPII and elevation densification point layout according to an embodiment of this application; Figure 3 This is a flowchart illustrating the main beam alignment adjustment in an embodiment of this application. Figure 4 This is a flowchart illustrating the determination of the zero-time window in an embodiment of this application.

[0021] The attached diagram lists the components represented by each number as follows: 11. Main pier; 12. Auxiliary pier; 13. Simply supported beam pier; 21. Plane control point of precision survey network; 22. Line leveling benchmark; 31. CPII control point; 32. Elevation densification point. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] To address the shortcomings or deficiencies mentioned in the background technology, this application provides a method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges. This method solves the problem that it is difficult to determine the timing of ballastless track control network measurements for long-span cable-stayed bridges in the prior art. Specifically, the measurement timing cannot be accurately determined due to unstable settlement of the subgrade, insufficient accuracy of the control network, and dynamic changes in the main beam alignment, leading to remeasurement of the control network and loss of accuracy.

[0024] See Figures 1 to 4 As shown in the figure, this application provides a method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges, including the following steps: S1. After the bridge foundation is constructed, settlement monitoring shall be carried out at a preset cycle until the settlement data meets the preset stability criteria. S2. After the settlement data meets the preset stability criteria, the line precision measurement network and the leveling benchmark control network are re-measured and densified until the measurement results reach the preset accuracy index. S3. Using the re-measured and densified line precision measurement network and leveling benchmark control network as a reference, measure, compare and adjust the main beam alignment until the difference between it and the design alignment converges to the preset tolerance range. S4. After the main beam alignment adjustment is completed, the main beam alignment monitoring data is analyzed, and the time period in which the alignment change rate is continuously lower than the preset rate threshold is determined as the zero time window, which is used as the optimal time window for track construction control network measurement.

[0025] In this embodiment of the application, after the bridge foundation construction of the long-span cable-stayed bridge, settlement observation is carried out at a preset cycle until the stability criterion is met. After the settlement data meets the standard, the precision measurement network and the leveling benchmark control network of the line are re-measured and densified to ensure that the accuracy meets the specifications. Based on the re-measurement network, the alignment of the main beam is measured, compared and adjusted until its deviation from the design alignment converges within the tolerance range. After the main beam alignment is adjusted, the monitoring data is analyzed, and the time period in which the alignment change rate is continuously lower than the preset threshold is accurately determined as the relatively stable zero time window, which is used as the best observation window.

[0026] The settlement of the offline engineering works met the design and specification requirements after assessment, effectively mitigating the impact of settlement differences between the main pier, side pier, and auxiliary pier foundations on the control network. The accuracy of the control network re-measurement and densification met the specifications after assessment, successfully solving the problem of establishing the bridge deck coordinate benchmark for the dual-purpose road-rail bridge. After the main beam alignment adjustment, it met the design requirements after assessment, completely avoiding the problem of re-measurement of the control network caused by subsequent steel beam alignment adjustments. By scientifically determining the period of relative stability of the main beam alignment, the interference of environmental factors such as temperature and wind on measurement accuracy was significantly reduced, providing a high-precision and high-reliability control network benchmark for ballastless track construction, and realizing the standardization and efficiency of measurement timing.

[0027] It should be noted that when the rate of change of the main beam's alignment is consistently lower than the preset rate threshold, the amount of alignment deformation is relatively small, and the interference to the control network measurement is negligible. Under these circumstances, measurement can ensure that the accuracy of the control network meets the requirements for ballastless track construction.

[0028] In practical applications, this threshold is determined through engineering evaluation and is usually between 0.1 and 0.3 mm / h. However, the specific value needs to be determined comprehensively based on the characteristics of the bridge structure, environmental conditions, and design accuracy requirements to ensure that the measurement is carried out within a 'relatively stable' period, so as to minimize the impact of external environmental changes on measurement accuracy and provide a high-precision control benchmark for ballastless track construction.

[0029] In some alternative embodiments: see Figures 1 to 4 As shown in the embodiments of this application, a method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges is provided. The method includes preset stability criteria, such as: The settlement rate of the bridge foundation is lower than the preset rate threshold; The total settlement of the bridge foundation is lower than the preset total threshold. The differential settlement between adjacent piers is lower than the preset differential threshold.

[0030] In this embodiment, the bridge foundation settlement assessment strictly meets three core conditions: the settlement rate remains below the safety threshold, the total settlement is controlled within the design allowable range, and the differential settlement between adjacent piers meets the standard specifications. Through systematic monitoring and dynamic assessment, it is ensured that the bridge foundation has entered a stable state before the measurement time is determined, effectively avoiding the problem of differential settlement caused by uneven load distribution among main piers, side piers, and auxiliary piers.

[0031] In practical engineering applications, this evaluation method successfully avoids control network measurement deviations caused by foundation settlement fluctuations, significantly improves data reliability, provides accurate benchmark support for ballastless track construction, and greatly reduces the risk of subsequent remeasurement due to settlement instability, thus realizing the scientific and efficient measurement process.

[0032] It should be noted that the setting of the three thresholds strictly follows the national railway engineering surveying specifications and bridge design requirements, and is determined through comprehensive analysis of on-site settlement monitoring data and engineering assessment. The settlement rate threshold is used to determine the stability of foundation settlement changes, the total settlement threshold ensures that the total settlement is controlled within the allowable range for structural safety, and the differential settlement threshold prevents uneven settlement between piers from affecting structural stability. The three work together to ensure the relative stability of the main beam alignment, provide a reliable opportunity for ballastless track control network measurement, and avoid measurement accuracy deviations caused by settlement fluctuations.

[0033] In some alternative embodiments: see Figures 1 to 4 As shown in the embodiments of this application, a method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges is provided. This method involves re-measuring and densifying the track precision survey network and the leveling benchmark control network until the measurement results reach a preset accuracy index, including: The CPI and CPII control points of the line precision measurement network are remeasured and their accuracy is evaluated until the accuracy of the points reaches the preset accuracy index. The leveling benchmark control network of the line is re-measured and its accuracy is evaluated until its elevation accuracy reaches the preset elevation accuracy index.

[0034] In this embodiment, the CPI and CPII control points of the line precision survey network are re-measured and their accuracy is evaluated to ensure that their positional accuracy meets the design specifications; at the same time, the line leveling benchmark control network is re-measured and its elevation accuracy is evaluated to ensure that the elevation accuracy meets the engineering standards.

[0035] Through systematic accuracy verification, the reliability and stability of the control network were effectively confirmed, providing a high-precision benchmark for subsequent main beam alignment measurement, comparison and adjustment.

[0036] This process avoids measurement deviations caused by insufficient control network accuracy, significantly reduces the risk of remeasurement due to unstable benchmarks during ballastless track construction, ensures the accuracy and consistency of track alignment control, and lays a solid foundation for overall construction quality.

[0037] In some alternative embodiments: see Figures 1 to 4 As shown in the embodiment of this application, a method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges is provided. This method involves re-measuring and densifying the track precision survey network and leveling benchmark control network until the measurement results reach a preset accuracy index. The method also includes: After the accuracy of the CPI and CPII control points meets the requirements, the CPII control points on the bridge deck are densified based on them. After the elevation accuracy of the leveling benchmark meets the requirements, it is used as a reference to densify the bridge deck elevation densification points.

[0038] In this embodiment of the application, after the accuracy of the CPI and CPII control points is evaluated and meets the specification requirements, the CPII control points on the bridge deck are densified based on these high-precision points to form a dense and reliable planar control network. At the same time, after the accuracy of the leveling benchmark elevation is evaluated and meets the standard, the bridge deck elevation control points are densified based on the benchmark leveling points to construct a high-precision elevation densification network.

[0039] This encryption process significantly improves the density and stability of bridge deck control points, providing a precise benchmark for subsequent main beam alignment measurement, comparison, and adjustment. It effectively avoids measurement errors caused by sparse or insufficient accuracy of control points, ensuring the reliability of main beam alignment adjustment. This, in turn, reduces the risk of remeasurement caused by benchmark fluctuations during ballastless track construction, and guarantees the accuracy of track alignment control and construction efficiency.

[0040] In some alternative embodiments: see Figures 1 to 4As shown in the embodiment of this application, a method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges is provided. The method includes the densification of CPII control points on the bridge deck, comprising: At least one CPII control point is set up on the inner side of each main pier tower of the cable-stayed bridge; A pair of CPII control points are set directly above the fixed supports of the simply supported beams at both ends of the cable-stayed bridge, and a preset distance is maintained between the pair of control points.

[0041] In this embodiment, at least one CPII control point 31 is arranged inside the tower column of each main pier 11, and a pair of CPII control points 31 are arranged directly above the fixed support of each simply supported beam pier 13, with a longitudinal bridge spacing of approximately 600m. This arrangement is scientific and reasonable for a simply supported beam spanning 600 to 700 meters, aiming to establish a stable benchmark for real-time monitoring and correction of lateral displacement and torsional deformation of the beam during construction and operation, ensuring the smoothness and accuracy of track laying.

[0042] No CPII control point 31 is set on the auxiliary pier 12 between the main pier 11 and the simply supported beam pier 13, avoiding control point redundancy and optimizing the network structure. This design significantly improves the reliability of track alignment control, effectively reduces the impact of beam deformation on measurement accuracy, provides a precise benchmark for high-precision construction of ballastless track, and ensures the overall project quality and efficiency.

[0043] In some alternative embodiments: see Figures 1 to 4 As shown, this application provides a method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges. The method includes the densification measurement of CPII control points on the bridge deck, comprising: For CPII control points located on simply supported beams, the GNSS static measurement method was used for observation, and the fine survey network plane control points were used as the starting point for calculation. For CPII control points located on the main pier towers, the precision traverse survey method was used for observation.

[0044] In this embodiment, the CPII control point 31 on the simply supported beam is observed using the GNSS static measurement method, and interpolation calculation is performed using the plane control point 21 of the precision survey network as the starting reference; the CPII control point 31 on the main pier 11 tower column is observed using the precision traverse survey method.

[0045] This differentiated measurement strategy effectively avoids the obstruction of GNSS signals and multipath interference caused by the tall tower environment, ensuring the stability and accuracy of coordinate transfer. In the simply supported beam area, the efficient interpolation advantage of GNSS is utilized, while in the tower area, the reference is accurately transferred using the traverse method. This significantly improves the overall reliability of the plane control network and provides a high-precision, highly consistent coordinate reference for subsequent main beam alignment adjustments.

[0046] In some alternative embodiments: see Figures 1 to 4 As shown in the embodiment of this application, a method for determining the timing of ballastless track control network measurement for long-span cable-stayed bridges is provided. The method includes the densification and measurement of bridge deck elevation densification points, which includes the location and number of bridge deck elevation densification points corresponding to the location and number of bridge deck CPII control points.

[0047] In this embodiment, at least one elevation densification point 32 is arranged on the inner side of each main pier 11 tower column, and a pair of elevation densification points 32 are arranged directly above the fixed support of each simply supported beam pier 13, with a longitudinal bridge spacing of approximately 600m. This arrangement is scientifically sound and reasonable for a single span of a simply supported beam 600 to 700 meters long, aiming to establish a stable benchmark for real-time monitoring and correction of lateral displacement and torsional deformation of the beam during construction and operation, ensuring the smoothness and accuracy of track laying.

[0048] No elevation densification point 32 is set on the auxiliary pier 12 between the main pier 11 and the simply supported beam pier 13, avoiding control point redundancy and optimizing the network structure. This design significantly improves the reliability of track alignment control, effectively reduces the impact of beam deformation on measurement accuracy, provides a precise benchmark for high-precision construction of ballastless track, and ensures the overall project quality and efficiency.

[0049] In some alternative embodiments: see Figures 1 to 4 As shown in the embodiments of this application, a method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges is provided. The method includes the densification measurement of bridge deck elevation densification points, which includes: The bridge deck elevation densification points and the line leveling benchmarks form a traverse leveling route. The connection measurement of the elevation densification points to the line leveling benchmarks in the traverse leveling route adopts the intermediate station method of trigonometric leveling, and the connection measurement of adjacent elevation densification point sections adopts second-order leveling.

[0050] In this embodiment, the bridge deck elevation densification point 32 and the line leveling benchmark 22 form a traverse leveling route. The section from the elevation densification point 32 to the line leveling benchmark 22 is measured using intermediate station trigonometric leveling, effectively avoiding interference from terrain undulations and obstacles. The section adjacent to the elevation densification point 32 is measured using second-order leveling, ensuring high accuracy and stability of short-distance elevation transfer.

[0051] This differentiated measurement strategy significantly improves the overall reliability of the elevation control network, avoids track alignment deviations caused by fluctuations in the elevation datum, provides a precise and consistent elevation datum for ballastless track construction, greatly reduces the adjustment risks during track laying, and ensures track smoothness and construction quality.

[0052] In some alternative embodiments: see Figures 1 to 4As shown in the embodiment of this application, a method for determining the timing of measurement of the control network for the ballastless track of a long-span cable-stayed bridge is provided. In step S3 of this method, the alignment of the main beam is measured, compared, and adjusted until the difference between it and the design alignment converges to a preset tolerance range, including: S31. Establish a finite element model of the bridge structure and the ballastless track; S32. After the main beam is closed, the main beam alignment is continuously observed for a first preset duration. S33. Compare the observed main beam profile with the predicted profile of the finite element model, and use the measured profile as a benchmark to correct the finite element model through parameter inversion until the difference between the theoretical predicted profile of the corrected model and the measured profile is less than the first preset threshold. S34. After the second phase of dead load is applied, the main beam alignment is continuously observed for a second preset duration. S35. The observed main beam profile is compared with the predicted profile of the current finite element model again, and the finite element model is corrected by parameter inversion until the difference between the theoretical predicted profile of the corrected model and the measured profile is less than the second preset threshold. S36. Based on the final revised finite element model, calculate and execute the adjustment amount of the main beam profile so that the difference between the adjusted main beam profile and the design profile falls within the preset tolerance range. S37. Based on the adjusted main beam alignment and finite element model, simulate and calculate the track geometry parameters after ballastless track laying, and confirm that the track geometry parameters meet the ballastless track laying accuracy standards.

[0053] In this embodiment, a finite element model is established based on the structural form, characteristics, and design drawings of the bridge and ballastless track. After the main beam is closed, continuous observation is conducted for 24 hours. The measured main beam alignment is compared with the model's predicted alignment, and the model is corrected through parameter inversion until the difference is less than a threshold. After the second-phase dead load is applied, continuous observation is conducted for 48 hours. The model is corrected again, and the adjustment amount of the main beam alignment is calculated so that the difference between the adjusted alignment and the design alignment converges within the tolerance range.

[0054] Based on the final revised finite element model, the geometric parameters of the ballastless track after laying were simulated and calculated, and the accuracy standards were confirmed to be met. This method effectively solves the matching problem between the main beam alignment and the design alignment of long-span cable-stayed bridges through dynamic model optimization and precise alignment control, significantly improving the smoothness and accuracy of track laying, avoiding the risk of track remeasurement due to alignment deviation, and providing a highly reliable benchmark guarantee for ballastless track construction.

[0055] In some alternative embodiments: see Figures 1 to 4As shown, this application provides a method for determining the timing of ballastless track control network measurement for a long-span cable-stayed bridge. In step S4, after the main girder alignment adjustment is completed, the main girder alignment monitoring data is analyzed, and the time period in which the alignment change rate remains below a preset rate threshold is determined as the zero-time window, serving as the optimal time window for track construction control network measurement. This includes: S41. After the main beam alignment is adjusted, continuously monitor the longitudinal, transverse and vertical alignment of the main beam and obtain monitoring data on its changes over time. S42. Based on monitoring data that changes over time, calculate the change in the main beam profile within a unit time interval, i.e., the rate of change in profile. S43. Analyze the monitoring data and identify that when the linear change rate of the main beam in the longitudinal, transverse and vertical directions is consistently lower than its respective preset rate threshold in at least one complete natural day cycle, then determine that the time period is a zero time window. S44. Define the zero time window as the operation time for measuring the track construction control network.

[0056] In this embodiment, after the main beam alignment is adjusted, the longitudinal, lateral and vertical alignment changes are continuously monitored to obtain time series monitoring data; the alignment change rate within a unit time interval is calculated; the data is analyzed to identify the period in which the change rate in all directions is continuously lower than a preset threshold within at least one complete natural day cycle, which is determined as a relatively stable zero time window; this zero time window is determined as the operation time for track construction control network measurement.

[0057] This method significantly improves the accuracy of the control network by ensuring that the settlement of the offline project, the accuracy of the control network re-measurement and densification, and the adjustment of the main beam alignment all meet the design requirements and are carried out within a zero time window. It effectively avoids environmental interference, provides a highly reliable benchmark for ballastless track construction, avoids measurement deviations caused by alignment fluctuations, and ensures the smoothness of track laying and construction quality.

[0058] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0059] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0060] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for determining the timing of measurement for the control network of ballastless track for a long-span cable-stayed bridge, characterized in that, Includes the following steps: After the bridge foundation is constructed, settlement monitoring will be carried out at a preset cycle until the settlement data meets the preset stability criteria. After the settlement data meets the preset stability criteria, the line precision measurement network and the leveling benchmark control network are re-measured and densified until the measurement results reach the preset accuracy index. Based on the re-measured and densified line precision measurement network and leveling benchmark control network, the main beam alignment is measured, compared and adjusted until the difference between it and the design alignment converges to the preset tolerance range. After the main beam alignment adjustment is completed, the main beam alignment monitoring data is analyzed, and the time period in which the alignment change rate is continuously lower than the preset rate threshold is determined as the zero time window, which is used as the optimal time window for track construction control network measurement.

2. The method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges as described in claim 1, characterized in that, The preset stability criteria include: The settlement rate of the bridge foundation is lower than a preset rate threshold. The total settlement of the bridge foundation is lower than a preset total threshold. The differential settlement between adjacent piers is lower than the preset differential threshold.

3. The method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges as described in claim 1, characterized in that... The re-measurement and densification of the precision survey network and leveling benchmark control network of the railway line until the measurement results reach the preset accuracy index includes: The CPI and CPII control points of the line precision measurement network are remeasured and their accuracy is evaluated until their point accuracy reaches the preset point accuracy index. The leveling benchmark control network of the line is re-measured and its accuracy is evaluated until its elevation accuracy reaches the preset elevation accuracy index.

4. The method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges as described in claim 3, characterized in that... The re-measurement and densification of the precision survey network and leveling benchmark control network until the measurement results reach the preset accuracy index also includes: After the positional accuracy of the CPI and CPII control points meets the requirements, the CPII control points on the bridge deck are densified based on them. After the elevation accuracy of the benchmark point meets the requirements, it is used as a reference to densify the bridge deck elevation densification points.

5. The method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges as described in claim 4, characterized in that... The densification of the bridge deck CPII control points includes: At least one CPII control point is set up on the inner side of each main pier tower of the cable-stayed bridge; A pair of CPII control points are set directly above the fixed supports of the simply supported beams at both ends of the cable-stayed bridge, and the pair of control points maintains a preset distance.

6. The method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges as described in claim 5, characterized in that... The encrypted measurement of the bridge deck CPII control points includes: For the CPII control points set on the simply supported beam, the GNSS static measurement method is used for observation, and the fine measurement network plane control points are used as the starting point for the indoor calculation. For the CPII control points located on the main pier tower, the precision traverse survey method was used for observation.

7. The method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges as described in claim 5, characterized in that, The densification and measurement of bridge deck elevation densification points include: The location and number of bridge deck elevation densification points correspond to the location and number of bridge deck CPII control points.

8. The method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges as described in claim 7, characterized in that, The encrypted measurement of the bridge deck elevation densification points includes: The bridge deck elevation densification points and the line leveling benchmarks form a traverse leveling route. The connection measurement of the elevation densification points to the line leveling benchmarks in the traverse leveling route adopts the intermediate station method of trigonometric leveling, and the connection measurement of adjacent elevation densification point sections adopts second-order leveling.

9. The method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges as described in claim 1, characterized in that, The process of measuring, comparing, and adjusting the main beam alignment until the difference between it and the design alignment converges to a preset tolerance range includes: Establish a finite element model of the bridge structure and ballastless track; After the main beam is closed, the beam alignment is continuously observed for the first preset duration. The observed main beam profile is compared with the predicted profile of the finite element model. The finite element model is then corrected by parameter inversion based on the measured profile until the difference between the theoretical predicted profile of the corrected model and the measured profile is less than the first preset threshold. After the second phase of dead load is applied, the main beam alignment is continuously observed for a second preset duration. The observed main beam profile is compared again with the predicted profile of the current finite element model, and the finite element model is corrected by parameter inversion until the difference between the theoretical predicted profile of the corrected model and the measured profile is less than the second preset threshold. Based on the final revised finite element model, the adjustment amount of the main beam profile is calculated and executed so that the difference between the adjusted main beam profile and the design profile falls within the preset tolerance range. Based on the adjusted main beam alignment and the finite element model, the track geometry parameters after ballastless track laying are simulated and calculated, and it is confirmed that the track geometry parameters meet the accuracy standards for ballastless track laying.

10. The method for determining the timing of ballastless track control network measurements for long-span cable-stayed bridges as described in claim 1, characterized in that, After the main beam alignment adjustment is completed, the main beam alignment monitoring data is analyzed, and the time period in which the alignment change rate remains below a preset rate threshold is determined as the zero time window, which serves as the optimal time window for track construction control network measurement. This includes: After the main beam alignment is adjusted, the longitudinal, transverse and vertical alignments of the main beam are continuously monitored to obtain monitoring data on their changes over time. Based on the monitoring data that changes over time, the change in the main beam profile within a unit time interval is calculated, i.e., the rate of change in profile. Analyzing the monitoring data, if the linear change rate of the main beam in the longitudinal, transverse and vertical directions is consistently lower than its respective preset rate threshold within at least one complete natural day cycle, then the time period is determined to be a zero time window. The zero-time window is defined as the operation time for measuring the track construction control network.

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