Multi-stage layered linear control method for large-span ballastless track cable-stayed bridge

Abstract

The invention discloses a multi-stage layered linear control method for a large-span ballastless track cable-stayed bridge, and the method comprises the steps: a main tower construction stage: adjusting the linear shape of a main tower through the jacking force of a cross brace, calculating the pre-lifting amount of an anchor point of a stay cable according to the subsequent load and concrete shrinkage creep factors, and correcting the rigidity of the main tower in a monitoring calculation model; a steel beam erecting stage: controlling the geometrical shape of the cantilever end of the steel beam, and adjusting the local abnormal elevation of the main truss through punching nails; adjusting linear states of steel beams on two sides of the closure opening; and in the ballastless track construction stage, local and overall deviations of the steel beams in the construction process are eliminated layer by layer through the multi-layer ballastless track structure, and track line shape high-precision control is achieved through track plate fine adjustment and self-compacting concrete grouting. Through the multi-stage layered linear control technology, the problems of error accumulation, temperature influence, poor multi-stage construction coordination and the like in the construction process are systematically solved, high-precision control over the track line shape is achieved, and it is ensured that the bridge forming state meets the elevation and smoothness acceptance standards at the same time.

Description

Technical Field

[0001] This invention relates to the field of high-speed railway cable-stayed bridge construction technology, and more specifically to a multi-stage layered alignment control method for long-span ballastless track cable-stayed bridges. Background Technology

[0002] With the development of high-speed railways, long-span cable-stayed bridges have been widely used in railway engineering due to their unique structural advantages. However, the construction control of ballastless track cable-stayed bridges faces many challenges. In traditional construction processes, various errors inevitably exist during the construction phase, such as the dispersion of material parameters and construction deviations. The accumulation of these errors can cause the bridge and track alignment to deviate from the design state, making it difficult to meet high-precision acceptance standards.

[0003] Compared to ballasted track, ballastless track offers higher stability, better smoothness, and lower maintenance costs, making it the primary track structure for high-speed railway bridges in my country. Compared to commonly used long-span bridges, cable-stayed bridges, due to their phased construction, have a greater impact on the final bridge alignment. Furthermore, as the main girder span increases, the bridge's structural stiffness gradually decreases, and environmental factors and construction errors significantly affect the final bridge and track alignment. Therefore, laying ballastless track on long-span cable-stayed bridges presents a major technical challenge.

[0004] Currently, various errors are unavoidable in the construction of ballastless tracks for high-speed railways at different stages, including main girder construction, tensioning, and track installation. The accumulation of these errors means that the applicable conditions of the stress-free state method cannot be strictly met, leading to deviations between the final bridge state and the design state. Existing construction control technologies mainly focus on controlling the accumulation of errors during the main girder construction stage, but lack a systematic method for controlling the alignment of ballastless track structures, making it difficult to simultaneously meet the requirements for track elevation and smoothness. The main girder, stay cables, and main tower of a long-span cable-stayed bridge will experience different temperature changes under the influence of ambient temperature, resulting in temperature differences between the tower, cables, and girder, which in turn affect the bridge and track alignment. Existing technologies do not provide precise enough correction for temperature effects, failing to effectively guarantee construction accuracy. The construction of ballastless track cable-stayed bridges involves multiple stages, including main tower construction, steel girder erection, closure joint adjustment, and ballastless track laying. The construction control objectives and measures for each stage lack organic integration, making it difficult to achieve precise control of the overall alignment.

[0005] Although existing technologies can control construction errors to some extent, achieving high-precision control of the track alignment remains difficult in the construction of long-span ballastless track cable-stayed bridges. This is particularly true in the construction of ballastless track cable-stayed bridges with a main span of 400 meters, where current construction control technologies cannot simultaneously meet the acceptance standards for track elevation and smoothness, thus limiting the development of long-span ballastless track cable-stayed bridges.

[0006] Therefore, how to provide a multi-stage, layered alignment control method for long-span ballastless track cable-stayed bridges on high-speed railways is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the present invention provides a multi-stage layered alignment control method for long-span ballastless track cable-stayed bridges. Through multi-stage layered alignment control technology, the method systematically solves problems such as error accumulation, temperature influence, and poor coordination of multi-stage construction during the construction process, and achieves high-precision control of track alignment, ensuring that the completed bridge meets the elevation and smoothness acceptance standards at the same time.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A multi-stage, layered alignment control method for long-span cable-stayed bridges with ballastless track includes: Main tower construction phase: Adjust the main tower alignment by using cross bracing thrust, and calculate the pre-lift of the stay cable anchor points based on subsequent loads and concrete shrinkage and creep factors to correct the main tower stiffness in the monitoring calculation model; During the steel beam erection stage: control the geometry of the cantilever ends of the steel beams, including the height difference of the main truss, the axis deviation and the local alignment deviation, and adjust the local abnormal elevation of the main truss by using punch pins; adjust the alignment of the steel beams on both sides of the closure joint to ensure that the geometric coordinates of the nodes on both sides of the closure joint meet the reasonable closure joint state; Ballastless track construction stage: The local and overall deviations of the steel beams during construction are eliminated layer by layer through a multi-layered ballastless track structure. Finally, the track alignment is controlled with high precision through track slab fine-tuning and self-compacting concrete grouting.

[0010] Preferably, the main tower construction phase also includes collecting data on the elastic modulus of the main tower concrete to correct the main tower stiffness in the monitoring calculation model.

[0011] Preferably, during the steel beam erection stage, an early warning is issued when the local alignment deviation at the cantilever end of the steel beam exceeds ±20mm, and adjustment measures are taken when it exceeds ±30mm.

[0012] Preferably, during the steel beam erection stage, the closure operation is carried out at night when the temperature is stable. The closure joint state is adjusted by the bridge surface under temporary load to ensure that the turning angles on both sides of the closure joint are zero and the geometric coordinates meet the reasonable closure joint state.

[0013] Preferably, the ballastless track construction stage includes alignment control for the subbase construction, alignment control for the base construction, and alignment control for fine-tuning the track slab. Subbase construction alignment control involves fitting the measured steel beam alignment to the current longitudinal profile, determining the final relative thickness of the subbase through iterative calculations, and determining the formwork elevation based on the relative thickness of the subbase. Base construction alignment control involves measuring the overall stiffness of the bridge under preload, correcting the calculation model, proposing an adjustment scheme for the entire bridge's cable stays, and eliminating overall deviations in the bridge and track alignment. Track slab fine-tuning alignment control is performed during stable nighttime temperatures, proposing a temperature-based pseudo-static effect correction value based on the measured tower-cable beam temperature to ensure the accuracy of the track slab fine-tuning.

[0014] Preferably, the control of the subbase construction alignment also includes comprehensively considering the load changes caused by the adjustment of the stay cables and the adjustment of the subbase thickness, and ensuring through iterative calculation that the deviation between the track elevation and the design value in the final bridge state is less than the allowable value.

[0015] Preferably, the base construction alignment control also includes proposing the formwork elevation of the side span and middle span base based on the steel beam alignment after the first cable adjustment, combined with the subsequent construction deformation and track design alignment.

[0016] Preferably, the track slab fine-tuning alignment control also includes final tensioning of the stay cables before track slab fine-tuning, and the cable adjustment scheme takes into account the influence of temperature on the bridge and track alignment to ensure the track slab fine-tuning accuracy.

[0017] Preferably, it also includes full-process control of construction surveying: during the main tower and cantilever assembly construction stage, a total station is used to measure the three-dimensional coordinates of the main tower and main beam, and the measurement data need to be cross-checked, with an absolute mean error of less than 4mm; during the ballastless track construction stage, a level is used to measure the elevation of each layer of the ballastless track structure with second-order leveling accuracy, and the CPIII control network is re-measured before each construction survey.

[0018] Preferably, temperature correction is also included: monitoring the temperature of the environment, main beam, main tower and cables during construction, and proposing temperature quasi-static effect correction values ​​based on the structural temperatures of the tower, cables and beams to ensure construction accuracy.

[0019] As can be seen from the above technical solution, the present invention discloses a multi-stage layered alignment control method for long-span ballastless track cable-stayed bridges. Through multi-stage layered alignment control technology, the track on long-span ballastless track cable-stayed bridges simultaneously meets the elevation and ride comfort acceptance standards. Compared with the prior art, it has the following beneficial effects: 1. The system systematically solves the problem of error accumulation during construction. Through multi-stage layered control technology, construction errors are eliminated layer by layer, ensuring the accuracy of track alignment.

[0020] 2. Taking into account the influence of temperature on the bridge and track alignment, a temperature-based pseudo-static effect correction method was proposed, which improved construction accuracy.

[0021] 3. It achieved coordinated control of multiple construction stages, including main tower erection, steel beam erection, closure joint adjustment, and ballastless track construction, thereby improving construction efficiency and quality.

[0022] 4. Through precise construction surveying and monitoring, high-precision control of the construction process was ensured, meeting the construction requirements of long-span ballastless track cable-stayed bridges for high-speed railways. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1 The present invention provides a flowchart for the construction control of the alignment of a ballastless track cable-stayed bridge. Figure 2 This invention provides a schematic diagram of the ideal closure joint for the main beam erection. Figure 3 This invention provides a schematic diagram of a reasonable closure joint for the main beam erection. Figure 4 This invention provides a flowchart for controlling the construction alignment of the subbase layer. Figure 5 The base construction alignment control flowchart provided by this invention; Figure 6 The present invention provides a flowchart for the fine-tuning alignment control of the track slab. Figure 7 This is a diagram of a cable-stayed bridge in Embodiment 1 of the present invention; Figure 8 This is a cross-sectional view of the main beam in Embodiment 1 of the present invention; Figure 9 This is a schematic diagram of the ballastless track structure in Embodiment 1 of the present invention; Figure 10 This refers to the bridge alignment measurement data during the cantilever assembly construction process in Embodiment 1 of the present invention; Figure 11 The elevation difference between the upstream and downstream sides of the main truss during the cantilever construction process in Embodiment 1 of the present invention; Figure 12 The maximum positive and negative deviations of each measuring point at each construction stage during the cantilever construction process in Embodiment 1 of the present invention are the overall and local deviations. Figure 13This refers to the deviation of the bridge axis during cantilever construction in Embodiment 1 of the present invention. Figure 14 The measured data of the distance, elevation difference, axial deviation and relative rotation angle on both sides of the closure joint along the bridge direction were continuously observed for 48 hours before the closure in Embodiment 1 of the present invention. Figure 15 This refers to the change in elevation at the track centerline during the bridge structure construction process in Embodiment 1 of the present invention. Figure 16 The 60-meter chord measurement values ​​at the center lines of the four tracks in Embodiment 1 of the present invention; Figure 17 This refers to the change in elevation of the track centerline during the construction of the track structure in Embodiment 1 of the present invention. Figure 18 This refers to the 60-meter chord measurement value at the centerline of the track during the construction of the track structure in Embodiment 1 of the present invention. Figure 19 This refers to the maximum 60-meter chord measurement value at the centerline position of the four tracks during the second permanent construction period after the main beam closure in Embodiment 1 of the present invention. Figure 20 This refers to the quasi-static effect of temperature deformation on the CPIII control point on the bridge in Embodiment 1 of the present invention. Figure 21 The elevation deviation and 60-meter chord measurement deviation of the four track lines in the completed bridge state in Embodiment 1 of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] This invention addresses the structural characteristics of long-span ballastless track cable-stayed bridges for high-speed railways, considering the requirements for bridge alignment and track smoothness control. It researches integrated bridge-track alignment control technology based on multi-stage layered alignment control, proposing a multi-stage layered alignment control method for ballastless track cable-stayed bridges. The research employs theoretical studies, numerical simulations, field measurements, and feedback correction to conduct control technology research covering the entire bridge and track construction process. Key control objectives for each stage are defined: In the main tower construction stage, the main objective is to determine the pre-lifting amount of the main tower and define structural parameters during construction; in the main beam cantilever and completed bridge construction stages, the objective is to correct the finite element model of the entire bridge based on measured data, reduce overall alignment deviations through bridge structure construction control, and simultaneously control the accumulation of local alignment deviations; in the track structure construction layered control stage, the objective is to reduce overall and local deviations through layer-by-layer track structure construction, and ultimately eliminate alignment deviations through track slab fine-tuning and self-compacting concrete grouting, ensuring that the completed bridge track alignment simultaneously meets elevation and smoothness control standards. During the ballastless track laying stage, a temperature-quasi-static effect correction method based on environmental-main beam-main tower-cable temperature monitoring is proposed to fine-tune the track slab alignment. It is recommended to fine-tune the alignment overnight during the nighttime temperature stability period.

[0027] like Figure 1 As shown in this embodiment, a multi-stage layered alignment control method for a long-span ballastless track cable-stayed bridge includes alignment control during the main tower construction stage, alignment control during the steel beam erection stage, alignment control during the ballastless track construction stage, and full-process control of construction surveying.

[0028] Main tower construction phase: Adjust the main tower alignment by using cross bracing thrust, and calculate the pre-lift of the stay cable anchor points based on subsequent loads and concrete shrinkage and creep factors to correct the main tower stiffness in the monitoring calculation model; the main tower construction phase also includes collecting main tower concrete elastic modulus data to correct the main tower stiffness in the monitoring calculation model.

[0029] To further optimize the above technical solution, there are two main factors for linear control during the main tower construction phase: one is adjusting the main tower's alignment and internal forces through the jacking force of the cross braces, and the other is the pre-lifting amount of the anchor points on the stay cables. The pre-lifting amount of the stay cable anchor points has a certain impact on the bridge and track alignment in the completed bridge state, but the construction deviation of the anchor point pre-lifting amount has an overall impact on the main beam and track alignment, which can be eliminated through cable adjustment.

[0030] The calculation of anchor point pre-lift needs to consider the vertical compression of the main tower caused by factors such as the increase in the self-weight of the structure and the shrinkage and creep of concrete during the subsequent construction of the anchor point. The anchor point pre-lift and the tower deflection during subsequent construction both affect the bridge and track alignment in the completed bridge state. During the main tower construction stage, it is necessary to clarify key data such as the elastic modulus of the main tower concrete and correct the main tower stiffness in the monitoring and calculation model.

[0031] During the steel beam erection phase: control the geometry of the cantilever ends of the steel beams, including the main truss height difference, axis deviation, and local alignment deviation, and adjust the local abnormal elevation of the main truss using drift pins; adjust the alignment of the steel beams on both sides of the closure joint to ensure that the geometric coordinates of the nodes on both sides of the closure joint meet the reasonable closure joint condition; issue an early warning when the local alignment deviation of the cantilever end of the steel beam exceeds ±20mm, and take adjustment measures when it exceeds ±30mm; carry out the closure operation at night when the temperature is stable, and adjust the closure joint condition through bridge surface temporary loads to ensure that the rotation angle on both sides of the closure joint is zero and the geometric coordinates meet the reasonable closure joint condition; adjust the local abnormal elevation of the main truss using drift pins, strengthen the stiffness of the lateral connection of the main truss, and reduce the planar torsion of the entire frame.

[0032] In actual construction, railway steel truss cable-stayed bridges can be divided into two categories based on transportation conditions: large-segment integral hoisting and member assembly. Control of the steel beam alignment is necessary during both types of construction. The geometric shape of the cantilever end of the steel truss includes the height difference between the two / three main trusses, axis deviation, and local deviations in the steel beam alignment. It should be noted that local deviations in the steel beam alignment refer to the alignment deviation within the first four large segments of the installed beam section. When the maximum local alignment deviation exceeds ±20mm and ±30mm respectively, warnings are issued and measures are taken to adjust the local alignment of the steel beam.

[0033] To further optimize the above technical solution, the local alignment adjustment measures for the cantilever end main truss require that, during the assembly of the main truss members between the two adjacent large steel truss segments, drift pins be driven in evenly at 50% of the total number of holes. The diameter of the drift pins should be 0.2 to 0.5 mm smaller than the theoretical hole diameter. Through the gap between the drift pins and the hole diameter, external force is applied to adjust the local abnormal elevation of the main truss, while strengthening the stiffness of the lateral connection of the main truss and reducing the planar torsion of the entire frame.

[0034] In actual construction, for the closure of the main girder of a steel truss cable-stayed bridge, the closure segment is typically hoisted, then one side of the closure segment is assembled with the already erected girder segment, and then closed with the other side of the steel girder. Before closure, the alignment of the steel beams on both sides of the closure joint needs to be adjusted. For two-main-truss and three-main-truss steel truss cable-stayed bridges, there are 6 and 9 closure joints respectively, and the requirements for the deviation of the steel beam alignment on both sides of the closure joint are very high. Under stress-free conditions, the ideal closure joint state of the steel truss girder is as follows: Figure 2 As shown, under stress-free conditions, the geometric coordinates on both sides of the closure joint of a single main truss must be equal, that is:

[0035] In the formula, X, Y, and Z represent the absolute coordinates of the bridge's longitudinal, transverse, and elevation directions, respectively. It should be noted that the alignment measurement of the steel truss girder before closure must be conducted in the same coordinate system.

[0036] To ensure that the turning angles on both sides of the closure joint are zero, the geometric coordinates on both sides of the closure joint must satisfy:

[0037] In the formula, z represents the vertical deformation of the bridge node, which is the absolute elevation of the steel truss node minus the deformation caused by adjacent nodes in the longitudinal section.

[0038] Various errors occur during bridge construction. Furthermore, the steel beams are fabricated according to the actual vertical curve of the track. Therefore, a stress-free closure state is usually unattainable during actual bridge construction. The closure joint state can be adjusted to... Figure 3 The reasonable closure state shown is represented by the geometric coordinates of the nodes on both sides of the closure opening as follows:

[0039] Figure 3 Under the reasonable closure condition shown, it is necessary to ensure that the rotation angle of the cantilever end of the steel beam on the closure side is zero, that is:

[0040] Under proper closure conditions, since the horizontal distance between the lower chord members after closure is less than the horizontal distance between the two sides of the upper chord closure opening, the lower chord members can be assembled first. After the lower chord punches and positioning bolts are installed, the upper chord at the closure opening can be adjusted by applying load to the lower chord and then installing the upper chord punches and positioning bolts.

[0041] Ballastless track construction stage: The local and overall deviations of the steel beams during construction are eliminated layer by layer through a multi-layered ballastless track structure. Finally, the track alignment is controlled with high precision through track slab fine-tuning and self-compacting concrete grouting.

[0042] Laying ballastless track on long-span bridges requires a multi-layered ballastless track structure to eliminate local and overall deviations of the steel truss girder during construction. The ballastless track construction phase includes... Linear control of subgrade construction: Based on the longitudinal section of the steel beam under the current state, the final relative thickness of the subgrade is determined by iterative calculation, and the formwork elevation of the subgrade is determined based on the relative thickness of the subgrade; taking into account the load changes caused by the adjustment of the stay cables and the adjustment of the subgrade thickness, iterative calculation is used to ensure that the deviation between the track elevation and the design value in the final completed bridge state is less than the allowable value.

[0043] The process for controlling the alignment of the subbase construction is as follows: Figure 4As shown, after the cantilever erection is completed, the bare beam alignment at the centerline position of the steel beam track is measured, and a longitudinal section at the centerline position of the track under the current bare beam state is fitted based on the measured values. Using the fitted longitudinal section under the current state as the initial value, theoretical calculations are performed for subsequent construction stages. Taking into account the load changes caused by the adjustment of the stay cables and the thickness of the subgrade, iterative calculations ensure that the deviation between the track elevation and the design value in the final bridge state is less than the allowable value. When the track elevation deviation in the completed bridge state meets the allowable value condition, the final relative thickness of the subgrade can be obtained. Based on the current measured alignment and the superimposed relative thickness of the subgrade, the formwork elevation of the subgrade can be determined.

[0044] Base construction alignment control: By measuring the overall stiffness of the bridge under preload, the calculation model is corrected, and an adjustment scheme for the entire bridge cable stays is proposed to eliminate the overall deviation of the bridge and track alignment. Based on the steel beam alignment after the first cable stay adjustment, combined with the subsequent construction deformation and track design alignment, the elevation of the base formwork for the side spans and middle spans is proposed.

[0045] The construction alignment control process for the base is as follows: Figure 5 As shown, currently, the overall stiffness of long-span ballastless track bridges is measured through preloading, and the calculation model is revised based on the measurement results to propose the cable length increment for adjusting the entire bridge's stay cables, thereby eliminating the overall deviation of the bridge and track alignment. After the steel beam alignment reaches the target elevation after cable adjustment, the formwork elevations for the side spans and mid-span are proposed based on the subsequent construction deformation and track design alignment. During the base construction process, it is necessary to clarify the variation law of ambient temperature and steel beam alignment, and adjust the steel beam alignment after closure through the first stay cable adjustment, while verifying the accuracy of the revised calculation model.

[0046] Track slab fine-tuning and alignment control: Track slab fine-tuning is carried out during the nighttime period when the temperature is stable. Based on the measured temperature of the tower cable beam, a temperature-quasi-static effect correction value is proposed to ensure the accuracy of track slab fine-tuning. Before the track slab fine-tuning, the stay cables are tensioned for the final tensioning. The cable adjustment plan takes into account the influence of temperature on the bridge and track alignment to ensure the accuracy of track slab fine-tuning.

[0047] Track slab fine-tuning alignment control process as follows Figure 6As shown, after the base construction is completed, the track slabs are roughly laid, and the calculation accuracy of the correction model is further verified based on the change in elevation of the top surface of the base slabs before and after the rough laying. Before fine-tuning after the track slabs are laid, the stay cables need to be tensioned. The cable adjustment plan needs to consider the influence of temperature on the bridge and track alignment. Since the track slab fine-tuning needs to be carried out at night, the overall structural temperature remains stable, meaning the temperature between different components of the same material remains basically uniform. For cable-stayed bridges, the measured temperatures of the tower, cable, and beam can be used as the structural temperature to simulate the quasi-static effect of structural temperature on the bridge and track alignment. After the final cable tension adjustment is completed, the fine-tuning elevations of the track slabs in the side spans and middle spans are proposed based on the changes caused by the grouting of self-compacting concrete in the side spans and middle spans, the final target track alignment, and the temperature of the tower, cable, and beam.

[0048] To further optimize the above technical solution, since the mid-span of a long-span steel truss cable-stayed bridge is significantly affected by temperature, the fine-tuning of the track slab within the mid-span range requires preliminary fine-tuning first, and temperature alignment correction values ​​should be proposed based on the measured tower cable beam temperatures. To avoid the influence of temperature on the fine-tuning of the track slab, it is recommended that the fine-tuning of the mid-span track slab be carried out at night when the temperature is stable and completed on the same day.

[0049] The entire construction surveying process is controlled during the main tower and cantilever assembly construction stages. A total station is used to measure the three-dimensional coordinates of the main tower and main beam. The measurement data must be cross-checked, and the absolute mean square error must be less than 4mm. During the ballastless track construction stage, a level is used to measure the elevation of each layer of the ballastless track structure with second-order leveling accuracy. The CPIII control network is re-measured before each construction survey.

[0050] In this embodiment, the alignment control of the ballastless track cable-stayed bridge requires high precision. The accuracy of measurement and monitoring data is fundamental to alignment control and requires full-process control. During the main tower and cantilever assembly construction phases, the three-dimensional coordinates of the main tower and main beam need to be measured simultaneously in each construction condition, all using a total station. Measurements are conducted in two groups, with cross-checking of data accuracy; it is recommended that the absolute mean square error between the two groups be less than 4 mm. During the ballastless track construction phase, alignment control only requires measuring the elevation of each layer of the ballastless track structure, and high measurement accuracy is required. It is recommended to use a level instrument with second-order leveling accuracy. It should be noted that the alignment of long-span cable-stayed bridges and tracks is greatly affected by temperature; track construction measurements can only be conducted at night under good weather conditions. Before each construction measurement, the CPIII control network must be re-measured and adjusted; the main tower deviation is monitored using GNSS.

[0051] During the construction of ballastless track cable-stayed bridges, the cable force is used to adjust the overall alignment deviation of the bridge and track. The accuracy of the cable force measurement affects the final bridge alignment. On-site cable force measurement typically involves using sensors to measure the acceleration response of the cables under load, and then calculating the cable force based on the explicit relationship between the cable force and its natural frequency. Since the cable natural frequency needs to be calculated using a Fast Fourier Transform (FFT) based on the measured cable acceleration time history, according to the sampling theorem, the frequency resolution Δf of the Fourier spectrum is equal to the reciprocal of the test duration T, i.e., Δf = 1 / T. Therefore, the frequency resolution and cable force measurement accuracy can only be improved by increasing the test duration. Considering both the sampling theorem and measurement accuracy, a sampling frequency above 50Hz is used to measure the cable force, and four consecutive harmonic frequencies of the cable are extracted from the Fourier spectrum to determine the fundamental frequency of the cable force.

[0052] In other specific embodiments, temperature correction is also included: monitoring the temperature of the environment, main beam, main tower and cables during construction, and proposing temperature pseudo-static effect correction values ​​based on the structural temperatures of the tower, cables and beams to ensure construction accuracy.

[0053] This embodiment provides a multi-stage, layered alignment control method for a long-span cable-stayed bridge with ballastless track. Alignment control is divided into three stages: main tower construction, main girder erection, and ballastless track structure construction. The main tower construction stage primarily affects alignment by defining structural parameters and calculating the pre-lift of the stay cable anchor points. Both contribute to the overall error in the final bridge alignment and can be reduced through cable adjustment. The main girder erection stage primarily affects the final bridge by local errors in the steel beams during assembly and on both sides of the closure joint. These alignment errors need to be reduced through post-closure track structure construction. Alignment control during the ballastless track construction stage mainly involves adjusting the stay cable tension to eliminate overall deviations in the steel beams and track, and using a three-layer system of foundation, base, and self-compacting concrete to eliminate local alignment deviations in the track. It should be noted that the adjustable range of the subbase is generally large, and it can also eliminate some overall deviations; the adjustment range of the base is mainly used to eliminate local deviations in the track structure; before the fine-tuning of the track slab, the deviation of the track alignment on the bridge has been controlled through the subbase, base, and adjustment cables. The fine-tuning of the track slab ensures that the track in the completed bridge state meets the acceptance standards. In addition, during the fine-tuning of the base and track, to prevent vertical deformation of the bridge caused by construction loads and secondary dead loads, which could lead to inflection points in the track alignment, the alignment must be controlled according to absolute elevation during the track structure construction process. Furthermore, the division of the construction area on the bridge must be based on the deformation characteristics of the bridge, and the division of the construction area should select a fixed point for vertical deformation of the bridge.

[0054] Example 1 Taking a double-tower, three-cable-stayed bridge with a steel truss girder and ballastless track for both road and rail use as an example, such as Figure 7As shown, the bridge span arrangement is (56+168+392+168+56) m, with a total length of 840 m. The upper level houses a 6-lane urban expressway, while the lower level accommodates a 2-track high-speed railway on the upstream side and a 2-track intercity railway on the downstream side. The entire bridge adopts a tower-beam separation, longitudinal semi-floating structural system, with transverse wind-resistant supports installed at the bridge towers. The vertical curve of the track on the bridge adopts a 3‰ longitudinal slope, with the slope change point located at the mid-span of the main span. Within a 98 m radius on both sides of the slope change point is a circular curve with a radius of 30,000 m.

[0055] like Figure 8 As shown, the main girder adopts a three-section main truss structure, an N-shaped truss, with side trusses and middle trusses having heights of 15.3m and 15.537m respectively, a truss width of 2×15.5m, and a segment spacing of 14m, totaling 60 segments for the entire bridge. The lower chord nodes of the steel beams on the lower mileage side are E0~E30, and the upper chord nodes are A0~A30; the lower chord nodes of the steel beams on the higher mileage side are E0'~E30, and the upper chord nodes are A0'~A30; the upper and lower chord nodes at mid-span of the steel truss girder are E30 and A30 respectively. The upper deck of the main girder uses an orthotropic integral steel bridge deck, while the lower deck uses an integral bridge deck combining box trusses and plate trusses. The steel beam manufacturing layout uses the lower chord system line as the baseline. Each node of the lower chord system line is located on the theoretical vertical curve. Within the mid-span circular curve range of the vertical curve, the stiffening beams are straight instead of curved; within the remaining straight longitudinal slope range, the lower chord system line coincides with the theoretical longitudinal slope of 3‰.

[0056] The bridge towers are A-shaped concrete structures, with a height of 170 m. The lower tower column is 21.7 m high, the middle tower column is 96.3 m high, the upper tower column is 38.285 m high, and the top section is 13.715 m high. The stay cables are... The stay cables are made of 15.2 mm steel strands with a standard tensile strength of 2100 MPa. The stay cables are arranged in a three-plane spatial configuration, with 12 pairs of stay cables and a total of 144 sets throughout the bridge.

[0057] The bridge track structure uses CRTS III type slab track within the E2~E2' node range, and beam end adjusters and double-block track within the E0~E2 and E0'~E2' node ranges. Figure 9 As shown, the CRTS III type slab track, from top to bottom, consists of: rails, fasteners, rail support platform, track slab, self-compacting concrete, isolation layer, base, and pad layer. It should be noted that during the initial fine-tuning process in the track's operation phase, the fastener adjustment range is generally 0 ~ +10 mm, and the standard 165 mm for the pad layer refers to the pad layer thickness at the track centerline.

[0058] Main tower construction phase During the main tower construction phase, structural parameters were collected through on-site measurements, and the thrust of the main tower's cross braces and the pre-lift of the anchor points were determined. Taking into account the stress state of the main tower wall and the main tower's alignment during construction, the thrust of the five cross braces of this bridge is 520 t, 600 t, 360 t, 400 t, and 240 t, respectively. Based on subsequent loads and concrete shrinkage and creep, the pre-lift of the anchor points of the two main towers is 45 mm.

[0059] Cantilever assembly construction control like Figure 10 As shown in the figure, solid lines represent measured elevation values, and dashed lines represent theoretical calculation values. It should be noted that the steel beam closure section was lifted using a dual-crane hoisting method. After lifting, the steel beam was first connected to the steel beam on the lower mileage side, and then spliced ​​to the steel beam on the higher mileage side. Therefore, after tensioning cable #11, the steel beam on the lower mileage side is higher than the steel beam on the higher mileage side. Because the finite element model was corrected using the method proposed in this invention during construction, the measured deviation of the elevation after tensioning cable #11 is less than 3 cm from the theoretical value.

[0060] like Figure 11 As shown, during the construction process, the height difference between the upstream and downstream sides of the main truss on both the large and small mileage sides was less than 5mm after the tensioning of cable #11, and the directions were consistent, providing good working conditions for the subsequent lifting of the closure section.

[0061] like Figure 12 As shown, due to alignment control during the cantilever assembly process, local deviations were all less than 30 mm, and overall deviations were all less than 40 mm, achieving the control target. Since the main beam was cantilevered after tensioning the No. 5 cable on the low mileage side and the No. 3 cable on the high mileage side, measures were taken in subsequent working conditions to reduce local deviations at the cantilever ends, thereby controlling the overall deviation. like Figure 13 As shown, due to the control of the axis during construction, the axis deviation of each node of the main beam before closure was less than 10 mm.

[0062] Continuous observation of both sides of the closure point for 48 hours Figure 14 As shown in the diagram, temperature changes significantly affect the relative spacing at the closure joint, with the rate of change per unit temperature being, in descending order, upstream, middle truss, and downstream. Furthermore, the closure joint spacing of the upper chord members is more sensitive to ambient temperature changes than that of the lower chord members. The shaded area in the diagram represents the time range where the lower chord spacing is less than the upper chord spacing. As shown, the upper and lower chord members reach a reasonable closure state at night. As shown in the diagram, the elevation difference on both sides of the closure joint is not sensitive to ambient temperature; therefore, temporary bridge surface load adjustments are needed to adjust the closure joint's state. As shown in the diagram, the axial deviation at the closure joint follows the same trend as temperature changes; the axial deviation change is small after 6 PM, and work is recommended during this time period. As shown in the diagram, the relative rotation angles of the three trusses are all less than 1‰ within 48 hours and are relatively stable at night.

[0063] Based on the test results of the closure joint spacing, axial deviation, elevation difference, and relative rotation angle, and considering the sensitive and inconsistent characteristics of the spacing between the three trusses of the upper chord with temperature changes, the closure operation must be carried out at night when the temperature is stable. First, the positioning bolts of the middle truss and upstream main truss of the lower chord are installed. After installation, the deviation of the downstream main truss is 3 mm, which can be corrected by longitudinal tensioning. After the installation of the positioning bolts of the three lower chord trusses, the closure joint spacing of the upstream, middle, and downstream upper chords is 8 mm, 8 mm, and 5 mm, respectively. The closure joint state of the upper chord is adjusted by longitudinal tensioning of the three upper chord trusses and by placing one 40-ton dump truck upstream and downstream of the bridge deck.

[0064] During the longitudinal movement and jacking of the steel beams on the high-mileage side, the displacement difference between the upstream and downstream sides was strictly controlled to be within 5mm, in increments of 2cm. After the closure joint was in place, the upstream and downstream elevation differences, the elevation differences on both sides of the closure joint, and the axial deviation were finely adjusted based on the observation data of the closure joint. The upstream and downstream elevation differences of the steel beams were adjusted using upstream and downstream counter-pressure, the elevation differences on both sides of the closure joint were adjusted using temporary loads on the beam surface, and the axial deviation was adjusted using tension or counter-jacking. After the closure joint punching was completed and before sunrise, the longitudinal constraints on the tower beams on the high-mileage side were released to allow for the release of longitudinal deformation of the steel beams caused by temperature changes.

[0065] Steel strand cable tension control The stay cables are tensioned in three stages (60%, 80%, and 100%). After the last strand of each stage is tensioned to its final position, the tension is maintained for 5 minutes. Markings are made after the 80% and 100% tensioning stages are completed, and the uniformity of the internal force of the strands within the cable is verified by measuring the elongation. To control the unbalanced force on the steel anchor beam, the difference in the number of tensioned individual strands within the same cable number and on the same side (side or middle truss) should not exceed 5 strands; for side and middle span stay cables of the same cable number, the difference in the total number of tensioned individual strands within the cable should not exceed 15 strands.

[0066] After the main girder is closed, the cable tension of the completed bridge needs to be adjusted according to the actual dead load. Since the dead load in the design drawings is generally greater than the actual dead load, the cable tension and length of the completed bridge are both less than the design values, and the initial tension length of some stay cables is less than the completed bridge cable length. The principle of the first cable adjustment of this bridge is to tension the cables with a remaining length greater than 50 mm to 50 mm, and not to adjust the cables with a length less than 50 mm; the second cable adjustment is to tension the remaining cables to the completed bridge cable length, and not to adjust the cables with insufficient length.

[0067] Subbase adjustment During the subbase construction, relative elevations were used for layout. For steel truss cable-stayed bridges, the stiffness of the side span steel beams and the longitudinal profile at the centerline of the steel beam track after bridge completion are controlled by the elevations of the tops of the side piers and auxiliary piers. Therefore, ensuring the absolute elevation of the steel beam pier top supports is sufficient to guarantee the alignment of the side span steel beams and their tracks. For the mid-span steel beams, the secondary dead load has a significant impact, and the cables were not adjusted during the beam lowering process, and the track structure load was not applied. Therefore, the longitudinal profile of the mid-span track centerline deviates significantly from the design value.

[0068] Based on the measured data, the alignment of the steel beam at the measuring points was fitted, resulting in three target steel beam alignments. It should be noted that E0~E16 and E0'~E16' were both fitted with a 3‰ slope; the center of segments E16~E23 and E16'~E23' were both fitted with a 4.45‰ slope; the target elevation of the circular curve was fitted with a vertical curve of 4.45‰ plus a radius of 30000; target elevation 2 was fitted with a vertical curve of 3‰ plus a radius of 30000; and target elevation 3.5‰ was fitted with a vertical curve of 30000.

[0069] Bridge structure construction like Figure 15 As shown in the figure, solid lines represent measured values, and dashed lines represent theoretical values. It should be noted that the measurements of changes before and after subbase construction, the first cable adjustment, and the changes before and after highway paving are all taken from the top surface of the subbase, while the measurements of changes before and after the second cable adjustment are taken from the top surface of the base. As shown in the figure, the theoretical values ​​calculated using the modified finite element model have a high degree of consistency with the measured values.

[0070] like Figure 16 As shown, bridge construction had no impact on the improvement of chord measurement values. This is mainly because bridge construction primarily affects the overall alignment of the track, thus having a relatively small impact on the 60-meter chord measurement values ​​of the track.

[0071] Track structure construction It should be noted that the measurements before and after the base construction are the elevations of the top surface of the subbase, the measurements before and after the track slab rough laying are the elevations of the top surface of the base, and the measurements before and after the self-compacting concrete grouting and water bag unloading are the elevations of the top surface of the rail support platform. Figure 17 As shown, the calculation results of the corrected finite element model are in good agreement with the measured results, demonstrating high calculation accuracy. like Figure 18 As shown, the chord measurement value at 60 meters was significantly improved during the track structure construction process. The chord measurement value at the track centerline position was also significantly improved after the track slab was roughly laid.

[0072] like Figure 19 As shown, the maximum value of the chord measurement continuously decreases. In particular, the chord measurement values ​​are significantly improved in the three construction stages: subbase construction, base construction, and track slab fine-tuning.

[0073] Model and temperature correction like Figure 20 As shown, a non-uniform temperature field exists between the steel beams, cables, and main tower due to the influence of ambient temperature and solar radiation temperature differences. While the temperature is stable among the steel beams, cables, and main tower in the early morning, temperature differences exist between different materials. The temperature gradients of the steel beams, cables, and main tower affect the alignment of the main beam and the track on the bridge, necessitating consideration of the impact of temperature differences between different components on construction control.

[0074] Completed bridge status like Figure 21 As shown, the deviations in elevation and chord measurements for all four track lines are less than 10 mm, meeting the acceptance standards for track elevation and smoothness.

[0075] This embodiment, through multi-stage layered alignment control technology, achieves for the first time on a 400-meter span ballastless track cable-stayed bridge that the track simultaneously meets the acceptance standards for elevation and smoothness. This method systematically solves problems such as error accumulation, temperature influence, and poor coordination in multi-stage construction during the construction process. It has significant innovation and practicality and can be widely applied to the construction control of long-span ballastless track cable-stayed bridges for high-speed railways.

[0076] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0077] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. 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 the invention. Therefore, the invention 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 disclosed herein.

Claims

1. A multi-stage layered alignment control method for a long-span ballastless track cable-stayed bridge, characterized in that, include: Main tower construction phase: Adjust the main tower alignment by using cross bracing thrust, and calculate the pre-lift of the stay cable anchor points based on subsequent loads and concrete shrinkage and creep factors to correct the main tower stiffness in the monitoring calculation model; During the steel beam erection stage: control the geometry of the cantilever ends of the steel beams, including the height difference of the main truss, the axis deviation and the local alignment deviation, and adjust the local abnormal elevation of the main truss by using punch pins; adjust the alignment of the steel beams on both sides of the closure joint to ensure that the geometric coordinates of the nodes on both sides of the closure joint meet the reasonable closure joint state; Ballastless track construction stage: The local and overall deviations of the steel beams during construction are eliminated layer by layer through a multi-layered ballastless track structure. Finally, the track alignment is controlled with high precision through track slab fine-tuning and self-compacting concrete grouting.

2. The multi-stage layered alignment control method for a long-span ballastless track cable-stayed bridge according to claim 1, characterized in that, The main tower construction phase also includes collecting data on the elastic modulus of the main tower concrete to correct the main tower stiffness in the monitoring calculation model.

3. The multi-stage layered alignment control method for a long-span ballastless track cable-stayed bridge according to claim 1, characterized in that, During the steel beam erection stage, an early warning is issued when the local alignment deviation at the cantilever end of the steel beam exceeds ±20mm, and adjustment measures are taken when it exceeds ±30mm.

4. The multi-stage layered alignment control method for a long-span ballastless track cable-stayed bridge according to claim 3, characterized in that, During the steel beam erection phase, the closure operation is carried out at night when the temperature is stable. The closure joint state is adjusted by the bridge surface under temporary load to ensure that the turning angles on both sides of the closure joint are zero and the geometric coordinates meet the reasonable closure joint state.

5. The multi-stage layered alignment control method for a long-span ballastless track cable-stayed bridge according to claim 1, characterized in that, The ballastless track construction phase includes alignment control for the subbase construction, alignment control for the base construction, and alignment control for fine-tuning the track slab. Subbase construction alignment control involves fitting the measured steel beam alignment to the current longitudinal profile, determining the final relative thickness of the subbase through iterative calculations, and then determining the formwork elevation based on this relative thickness. Base construction alignment control involves measuring the overall stiffness of the bridge under preload, correcting the calculation model, proposing an adjustment scheme for the entire bridge's cable stays, and eliminating overall deviations in the bridge and track alignment. Track slab fine-tuning alignment control is conducted during stable nighttime temperatures, proposing temperature-based pseudo-static effect correction values ​​based on measured tower-cable beam temperatures to ensure the accuracy of track slab fine-tuning.

6. The multi-stage layered alignment control method for a long-span ballastless track cable-stayed bridge according to claim 5, characterized in that, The alignment control of the subbase construction also includes comprehensively considering the load changes caused by the adjustment of the stay cables and the adjustment of the subbase thickness, and ensuring through iterative calculation that the deviation between the track elevation and the design value in the final bridge state is less than the allowable value.

7. The multi-stage layered alignment control method for a long-span ballastless track cable-stayed bridge according to claim 6, characterized in that, The base construction alignment control also includes proposing the formwork elevation of the side span and middle span base based on the steel beam alignment after the first cable adjustment, combined with the subsequent construction deformation and track design alignment.

8. The multi-stage layered alignment control method for a long-span ballastless track cable-stayed bridge according to claim 7, characterized in that, The fine-tuning and alignment control of the track slab also includes final tensioning of the stay cables before fine-tuning the track slab. The cable adjustment scheme takes into account the impact of temperature on the bridge and track alignment to ensure the accuracy of the track slab fine-tuning.

9. A multi-stage layered alignment control method for a long-span ballastless track cable-stayed bridge according to any one of claims 1 to 8, characterized in that, It also includes full-process control of construction surveying: during the main tower and cantilever assembly construction stage, a total station is used to measure the three-dimensional coordinates of the main tower and main beam, and the measurement data need to be cross-checked, with an absolute mean error of less than 4mm; during the ballastless track construction stage, a level is used to measure the elevation of each layer of the ballastless track structure with second-order leveling accuracy, and the CPIII control network is re-measured before each construction survey.

10. A multi-stage layered alignment control method for a long-span ballastless track cable-stayed bridge according to any one of claims 1 to 8, characterized in that, It also includes temperature correction: during construction, the temperature of the environment, main beam, main tower and cables is monitored, and temperature pseudo-static effect correction values ​​are proposed based on the structural temperature of the tower, cables and beams to ensure construction accuracy.

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