A control method suitable for flexible closure of a middle span of a three-tower steel box girder cable-stayed bridge

Abstract

The present application relates to a kind of control method suitable for three-tower steel box girder cable-stayed bridge midspan flexible closure, comprising the following steps: predicting closure temperature, correcting closure section steel box girder length, and determining theoretical unstressed closure target posture;When one side main span has closure condition, the elevation of cantilever end girder and end face angle of closure opening two sides are measured, and unstressed closure posture adjustment amount is determined by calculation;Through the way of temporary weight or cable force adjustment, cantilever end girder elevation and inclination are adjusted to be consistent with theoretical unstressed closure target posture;Closure opening middle tower side crane station is unchanged, and one side main span closure is completed;Closure step is repeated, and the other span girder closure is completed;Bridge deck crane releases hook, and cable force is adjusted to the theoretical cable force after closure.Compared with prior art, the present application has the advantages of reducing large cantilever construction waiting operation time, reducing structural safety risk during construction, improving construction efficiency, realizing steel box girder cable-stayed bridge accurate closure and the like.

Description

Technical Field

[0001] This invention relates to the field of bridge construction control, and in particular to a control method applicable to the flexible closure of the mid-span of a three-tower steel box girder cable-stayed bridge. Background Technology

[0002] In traditional cable-stayed bridge construction techniques, when closing the two main spans of a three-tower separated steel box girder cable-stayed bridge, a symmetrical synchronous closure method is typically used. This method primarily ensures the symmetry of the structural alignment and stress state, preventing unadjustable deviations in tower deflection and main girder alignment and internal forces caused by asymmetrical construction. However, the prerequisite for symmetrical synchronous closure of the two main spans is that the main girders of all three towers have reached their maximum cantilever stage. If this prerequisite is not met, the bridge will face a situation where the maximum cantilever is waiting for closure, posing a significant challenge to the wind resistance and safety control of the structure during construction.

[0003] Currently, the hoisting construction of the closure section of a steel box girder cable-stayed bridge adopts the method of "lifting with cranes on both sides of the closure joint or lifting with a crane on one side plus a counterweight on the other side". The closure process mainly includes the temperature-controlled cutting method and the jacking method. For the mid-span closure of a three-tower cable-stayed bridge, regardless of the hoisting method and closure process used, it is required that the two main span closure sections be hoisted symmetrically. The specific steps of its closure construction and control are as follows: (1) Continuous observation of the size and temperature of the closure opening on both sides to determine the ideal closure temperature, the cutting length of the closure segment and other control parameters; (2) Sensitivity analysis of each parameter of the closure opening to determine the adjustment measures for closure; (3) Cutting of the closure segment and transporting it to the bridge site below the closure opening; (4) The two main span closure opening cranes symmetrically and synchronously lift the closure segment to the bottom of the closure opening; (5) Measurement of the alignment data of the closure opening and elimination or reduction of alignment deviation through control measures; (6) Waiting for the ideal closure temperature to be embedded into the closure opening, accurately matching the closure opening, and temporarily locking it; (7) Permanent welding connection and release of the hook of the bridge deck crane. The synchronous closure of the two main spans requires coordinated monitoring of the dimensions of the two closure joints. Closure adjustment measures and temperature changes have a significant interrelationship with the dimensions of the two closure joints, placing high demands on the synchronization of the crane's hook-lifting and hoisting processes. This increases the difficulty of measuring deformation and controlling the alignment of the closure joints, leading to long construction periods and low efficiency. Furthermore, if the cantilever construction progresses inconsistently, there is the unfavorable situation of the large cantilever waiting for closure. How to reduce the construction time of large-span steel box girder cable-stayed bridges in a large cantilever state, achieve asynchronous and flexible closure of the two main spans of a three-tower cable-stayed bridge, and improve closure accuracy has become a common concern for builders. Summary of the Invention

[0004] The purpose of this invention is to overcome the disadvantages of existing technologies, such as the unfavorable construction state of the large cantilever waiting for closure due to different construction progress of the three-tower main girder cantilever, and the asymmetry of structural alignment and internal force state caused by asynchronous closure. This invention provides a control method for flexible closure of the mid-span of a three-tower steel box girder cable-stayed bridge. At the closure joint, a single-sided crane is used to lift the closure section of the steel box girder. Through temporary counterweights and local adjustment of the stay cable tension, a stress-free closure state of the main girder is ensured, meaning the elastic curve of the main girder at the closure point remains continuous. This technology eliminates the need to consider the issue of symmetrical synchronous closure of the two main spans of a three-tower steel box girder cable-stayed bridge; one main span can be closed first, or both main spans can be closed simultaneously. This avoids the structural wind resistance safety risks faced by cable-stayed bridges in the unfavorable state of large cantilever waiting for closure due to differences in construction progress, improves construction efficiency, and demonstrates the flexibility of closure control.

[0005] This invention provides a control method for flexible closure of the mid-span of a three-tower steel box girder cable-stayed bridge, comprising the following steps:

[0006] S1: Establish the overall finite element analysis model for the construction stage of the cable-stayed bridge;

[0007] S2: Predict the closure temperature, consider the impact of closure temperature and construction method on the length of the closure section, and correct the length of the steel box girder of the closure section; before the closure stage of on-site construction, predict the closure temperature based on historical meteorological data and calculate the deviation value from the design reference temperature.

[0008] S3: Based on the corrected beam length, establish a finite element analysis single-beam model of the closure section steel box girder. Calculate the relative elevation of the top plate of the beam end at small and large mileage points and the inclination angle of the beam end face under self-weight load (uniformly distributed longitudinal load of the main beam and concentrated load of the transverse diaphragm) to determine the theoretical stress-free closure target posture. The load magnitude and distribution are determined according to the design drawings. The lifting point position of the closure section steel box girder is determined according to the construction plan, while also considering the influence of the longitudinal slope of the main beam on the closure target posture.

[0009] S4: Calculate the installation elevation of the top of the steel box girder at the small and large mileage points of the closure section;

[0010] S5: Consider longitudinal slope The impact on the target attitude of the closure is investigated, and the target attitude of the beam end closure (relative elevation and beam end face inclination angle) is corrected.

[0011] S6: When the main span on one side is ready for closure, use a total station to measure the elevation of the top and bottom plates and the longitudinal coordinates of the center line of the main beam at the end of the large cantilever on the middle tower and the side tower. Calculate the inclination angle of the end face of the main beam at the end of the large cantilever. Based on the measurement results, determine the elevation adjustment amount and the inclination angle adjustment amount of the beam end face for stress-free closure of the large cantilever beam at the middle tower and the side tower.

[0012] S7: Set temporary counterweights at the ends of the large cantilever beams on both sides, and at the same time, observe the changes in elevation and end face inclination of the large cantilever beams on the middle tower and side tower sides caused by the temporary counterweights in the overall model of the cable-stayed bridge.

[0013] S8: In the overall model, change the cable force of the two pairs of stay cables on the large cantilever of the middle tower and the side tower near the closure point, and observe the changes in the elevation of the large cantilever beam end and the changes in the inclination angle of the beam end face caused by the changes in the cable force of the two pairs of stay cables.

[0014] S9: Calculate the required cable tension adjustment for the stay cables on the middle tower side and the side tower side, adjust the cable tension on site, and control the elevation error within ±10mm and the tilt angle error within 0.001rad;

[0015] S10: The steel box girder of the closure section is lifted using the bridge deck crane on one side of the side tower at the closure point. The bridge deck crane position of the middle tower remains unchanged. Lifting the closure section has no impact on the stress and deformation of the middle tower structure, thus ensuring the stress and linear symmetry of the middle tower structure. After the closure section is lifted and embedded into the closure point for precise alignment and matching, a temporary connection is installed to lock the closure point.

[0016] S11: Perform circumferential welding on the closure section. The main span on one side is closed. The bridge deck crane remains in the lifting state and does not release the hook.

[0017] S12: When the other main span is ready for closure, repeat steps S5~S9 to complete the closure of the other main span.

[0018] S13: After the entire bridge is closed, the bridge deck cranes on both sides that lift the closure section will be released to complete the weight transfer of the closure section. The longitudinal limit support or damper of the middle tower will be installed, and the longitudinal temporary anchorage of the middle tower will be removed. The temporary load applied before the closure will be removed, and the cable force of the stay cable adjusted before the closure will be adjusted to the theoretical cable force after the closure.

[0019] Furthermore, in S2, the deviation between the predicted closure temperature and the design reference temperature is calculated. The corrected length of the steel box girder in the closure section is... m;

[0020] In the formula, The design length of the steel box girder for the closure section; The length of the cantilever of the main beam from the central tower to the closure point; The length of the cantilever of the main beam from the side tower to the closure point; 0.015m is the coefficient of linear expansion of the steel box girder; 0.015m is the length reserved for welding construction.

[0021] Furthermore, in S3, the weight of the diaphragm is applied to the corresponding nodes as a concentrated load. The steel box girder model is modified according to the design drawings to ensure that the weight of the closure section steel box girder is consistent with the design drawings, and general support boundary conditions are added to the nodes at the lifting points in the model. The relative elevation between the top plate of the beam end at the small mileage and the adjacent lifting point under self-weight load is calculated from the model. and the inclination angle of the beam end face The relative elevation between the beam end at high mileage and the nearest lifting point and the inclination angle of the beam end face .

[0022] Furthermore, in S4, based on the main beam installation alignment, the installation elevations of the top of the steel box girder at the small and large mileage lifting points of the closure section are calculated as follows: , ; , It is calculated based on the design alignment, pre-camber, and paving thickness.

[0023] Furthermore, in S5, the longitudinal slope of the route where the steel box girder of the closure section is located is taken into consideration. The impact on the target closure attitude was addressed by correcting the target closure attitude (relative elevation and beam end face inclination) at the beam end. After correction, the relative elevation and beam end face inclination at the lower mileage were as follows: , The relative elevation of the beam end at the high mileage and the inclination angle of the beam end face are respectively , .

[0024] Furthermore, in S6, a total station is used to measure the elevation of the top and bottom plates and the longitudinal coordinates of the main beams at the center line of the large cantilever ends on the middle tower and side tower sides, and to calculate the inclination angle of the end face of the main beams at the large cantilever ends. Specifically, a prism is placed at the positions of the top and bottom plates of the main beams at the cantilever ends on both sides of the closure joint, and the elevation of the top plate at the center line of the main beams at the large cantilever ends on the middle tower side is measured using a total station. Longitudinal bridge coordinates The elevation of the bottom plate at the center line of the main beam at the end of the large cantilever on the side of the middle tower. Longitudinal bridge coordinates And the elevation of the top plate at the center line of the main beam at the end of the large cantilever on the side tower. Longitudinal bridge coordinates The elevation of the bottom plate at the center line of the main beam at the end of the large cantilever on the side of the middle tower. Longitudinal bridge coordinates ; Calculate the angle of the end face of the main beam at the end of the large cantilever on the side of the middle tower. Angle of the end face of the main beam at the end of the large cantilever on the side tower .

[0025] Furthermore, in S7 and S8, the elevation adjustment and end face inclination adjustment of the stress-free closure of the large cantilever beam ends on the central tower and side tower sides are characterized in that: the elevation adjustment and inclination adjustment of the stress-free closure of the large cantilever beam ends on the central tower side are respectively... , The elevation and tilt adjustment amounts for stress-free closure of the large cantilever beam end on the side tower are respectively , ;

[0026] in, This represents the percentage of the longitudinal slope of the route where the steel box girder of the closure section is located; , These are the installation elevations of the top of the steel box girder at the small and large mileage lifting points of the closure section, respectively. , These are the top plate elevations of the main beam centerline positions at the large cantilever ends of the central tower and side tower, measured before the closure. , These are the inclination angles of the main beam end faces at the large cantilever ends of the central tower and side towers, calculated before the closure.

[0027] Furthermore, in S9, the required cable force adjustments for the two pairs of stay cables M1 and M2 near the closure point on the large cantilever of the central tower are as follows: , The cable tension adjustment amounts corresponding to the two pairs of stay cables S1 and S2 near the closure point on the side tower's large cantilever are respectively , The calculation process is as follows:

[0028] ;

[0029] In the formula, , , , To calculate intermediate process quantities; , For the overall model of the cable-stayed bridge, the tension adjustment of the two pairs of stay cables M1 and M2 on the large cantilever side of the middle tower near the closure point. , The corresponding change in elevation at the end of the large cantilever beam. , This represents the change in the inclination angle of the corresponding beam end face. , For the overall model, the cable tension of the two pairs of stay cables S1 and S2 near the closure point on the large cantilever of the side tower is adjusted. , The corresponding change in elevation at the end of the large cantilever beam. , This represents the change in the inclination angle of the corresponding beam end face. , This represents the changes in elevation and end face inclination of the large cantilever beam on the middle tower side caused by temporary counterweights in the overall model. , The changes in elevation and inclination angle of the large cantilever beam end on the side tower caused by temporary ballast are considered.

[0030] Furthermore, in S13, the theoretical cable force after the closure of the cable-stayed bridge is calculated using the overall model of the cable-stayed bridge construction stage.

[0031] Furthermore, in S10, the longitudinal temporary anchorages on the side towers of the main span that has been closed are removed, while the longitudinal temporary anchorages on the middle tower are retained, allowing the main beam of the main span on the closed side to undergo free deformation under the influence of temperature.

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

[0033] (1) This invention does not require the simultaneous closure of the two main spans. When one main span is ready for closure, it can be closed first; when both main spans are ready for closure at the same time, they can also be closed simultaneously, which greatly reduces the duration of the unfavorable wind resistance condition when the flexible steel box girder cable-stayed bridge is waiting for closure in a large cantilever state, and reduces the safety risks in the structural construction process.

[0034] (2) A calculation method is provided for adjusting the elevation and stress-free tilt angle deviation of the main beam at the closure joint during flexible asynchronous closure of the double main span. During the closure of the main beam, the cable force adjustment data is determined in advance, the number of on-site measurements is reduced, and the closure can be completed in a short time. This effectively avoids large changes in on-site temperature that could affect the closure accuracy and quality.

[0035] (3) This closure method ensures the continuity of the elastic curve of the main beam, so that the final internal force of the structure is independent of the formation process of the structure. That is, the construction method of asynchronous closure of the double main span will not affect the final internal force of the structure. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the overall finite element analysis model for the construction phase of a cable-stayed bridge.

[0037] Figure 2 To take into account the temperature at the closure section and the construction method, the schematic diagram of the steel box girder length of the closure section has been revised.

[0038] Figure 3 A schematic diagram of a single beam model for finite element analysis of the closure segment of the steel box girder, based on the corrected beam length.

[0039] Figure 4To assess the impact of the longitudinal slope of the route where the steel box girder of the closure section is located on the target attitude of the closure, the target attitude (relative elevation and beam end face inclination) of the beam end is corrected. The corrected diagrams show the relative elevation and beam end face inclination of the beam end at small and large mileages.

[0040] Figure 5 This diagram illustrates the elevation of the top and bottom slabs and the longitudinal coordinates of the main span closure section on the side with closure conditions, using a total station to measure the location of the centerline of the main beam at the end of the large cantilever.

[0041] Figure 6 A schematic diagram showing the use of a side tower crane to lift the steel box girder of the closure section, ensuring the central tower crane remains in the same position during the closure process. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms, and other features not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0043] Example 1

[0044] This invention provides a control method for flexible closure of the mid-span of a three-tower steel box girder cable-stayed bridge, comprising the following steps:

[0045] S1: Establish a finite element analysis model for the overall construction phase of the cable-stayed bridge; the model is as follows: Figure 1 As shown.

[0046] S2: Predict the closure temperature, consider the impact of closure temperature and construction method on the length of the closure section, and correct the length of the steel box girder of the closure section; before the closure stage of on-site construction, predict the closure temperature based on historical meteorological data and calculate the deviation value from the design reference temperature.

[0047] S3: Based on the corrected beam length, establish a finite element analysis model of the closure segment steel box girder as a single beam. The model is as follows: Figure 3 As shown, the relative elevation of the top plate of the beam end and the adjacent lifting point and the inclination angle of the beam end face are calculated under self-weight load (uniformly distributed longitudinal load of the main beam and concentrated load of the transverse diaphragm) at small and large mileages to determine the theoretical stress-free closure target posture. The load magnitude and distribution are determined according to the design drawings. The lifting point position of the steel box girder of the closure section is determined according to the construction plan, while considering the influence of the longitudinal slope of the main beam on the closure target posture.

[0048] S4: Calculate the installation elevation of the top of the steel box girder at the small and large mileage points of the closure section;

[0049] S5: Considering the longitudinal slope of the route The impact on the target attitude of the closure is investigated, and the target attitude of the beam end closure (relative elevation and beam end face inclination angle) is corrected.

[0050] S6: When the main span on one side is ready for closure, use a total station to measure the elevation of the top and bottom plates and the longitudinal coordinates of the center line of the main beam at the end of the large cantilever on the middle tower and the side tower. Calculate the inclination angle of the end face of the main beam at the end of the large cantilever. Based on the measurement results, determine the elevation adjustment amount and the inclination angle adjustment amount of the beam end face for stress-free closure of the large cantilever beam at the middle tower and the side tower.

[0051] S7: Determine the changes in the elevation of the closure point and the inclination angle of the beam end by the temporary counterweight at the closure point or the adjustment of the cable tension of the cable near the closure point through finite element model calculation;

[0052] S8: On-site, the elevation error is controlled within ±10mm and the tilt angle error is controlled within 0.001rad by temporary ballast or adjustment of the cable tension.

[0053] S9: Using the bridge deck crane on one side of the closure tower, the steel box girder of the closure segment is lifted. The bridge deck crane position on the middle tower remains unchanged. Lifting the closure segment has no impact on the stress and deformation of the middle tower structure, thus ensuring the stress and linear symmetry of the middle tower structure. After the closure segment is lifted and precisely aligned into the closure joint, a temporary connection is installed to lock the closure joint. Figure 6 As shown.

[0054] S10: After the closure section is temporarily locked, the longitudinal temporary anchorage of the side tower on the closure side is removed, while the longitudinal temporary anchorage of the middle tower is retained, so that the main beam on the closed side can undergo free deformation under the action of temperature.

[0055] S11: Perform circumferential welding on the closure section. The main span on one side is closed. The bridge deck crane remains in the lifting state and does not release the hook.

[0056] S12: When the other main span is ready for closure, repeat steps S5~S9 to complete the closure of the other main span.

[0057] S13: After the entire bridge is closed, the bridge deck cranes on both sides that lift the closure section will be released to complete the weight transfer of the closure section. The longitudinal limit support or damper of the middle tower will be installed, and the longitudinal temporary anchorage of the middle tower will be removed. The temporary load applied before the closure will be removed, and the cable force of the stay cable adjusted before the closure will be adjusted to the theoretical cable force after the closure.

[0058] In specific implementation methods, such as Figure 2 As shown in Figure S2, the deviation between the predicted closure temperature and the design reference temperature is calculated. The corrected length of the steel box girder in the closure section is... m;

[0059] In the formula, The design length of the steel box girder for the closure section; The length of the cantilever of the main beam from the central tower to the closure point; The length of the cantilever of the main beam from the side tower to the closure point; 0.015m is the coefficient of linear expansion of the steel box girder; 0.015m is the length reserved for welding construction.

[0060] In the specific implementation, in S3, the weight of the diaphragm is applied to the corresponding nodes as a concentrated load. The steel box girder model is modified according to the design drawings to ensure that the weight of the closure section steel box girder is consistent with the design drawings. General support boundary conditions are added to the nodes at the location of the lifting points in the model. The relative elevation between the top plate of the beam end at the small mileage and the adjacent lifting point under self-weight load is calculated from the model. and the inclination angle of the beam end face The relative elevation between the beam end at high mileage and the nearest lifting point and the inclination angle of the beam end face The lifting points for the closure section steel box girder were determined according to the construction plan (assuming the distance from the lifting point to the beam end is...). Add general support boundary conditions to the nodes at the location of the lifting points in the model, and calculate the self-weight load (uniformly distributed longitudinal load on the steel box girder). and diaphragm concentrated load Below, the relative elevation between the top plate of the beam end at the small mileage and the adjacent lifting point. and the inclination angle of the beam end face The relative elevation between the top plate of the beam end at high mileage and the adjacent lifting point and the inclination angle of the beam end face Determine the theoretical stress-free closure target posture. (When the temporary lifting point is higher than the top plate of the beam end,) , A positive value indicates a positive value, and a negative value indicates a negative value; when the beam end section is obtained by rotating the vertical section counterclockwise, it can be seen that... , (Positive value, negative value.)

[0061] In the specific implementation, in S4, based on the main beam installation alignment, the installation elevations of the top of the steel box girder at the small and large mileage lifting points of the closure section are calculated as follows: , ; , It is calculated based on the design alignment, pre-camber, and paving thickness.

[0062] In the specific implementation, S5 takes into account the longitudinal slope of the route where the steel box girder of the closure section is located. The impact on the target closure attitude was addressed by correcting the target closure attitude (relative elevation and beam end face inclination) at the beam end. After correction, the relative elevation and beam end face inclination at the lower mileage were as follows: , The relative elevation of the beam end at the high mileage and the inclination angle of the beam end face are respectively , .like Figure 4 As shown.

[0063] In a specific implementation, in step S6, a total station is used to measure the elevation of the top and bottom plates and the longitudinal coordinates of the main beam at the center line of the large cantilever end of the central tower and side towers, and to calculate the inclination angle of the end face of the main beam at the large cantilever end. Specifically, a prism is placed at the positions of the top and bottom plates of the main beam at the cantilever end on both sides of the closure joint, and the elevation of the top plate at the center line of the main beam at the large cantilever end of the central tower is measured using a total station. Longitudinal bridge coordinates The elevation of the bottom plate at the center line of the main beam at the end of the large cantilever on the side of the middle tower. Longitudinal bridge coordinates And the elevation of the top plate at the center line of the main beam at the end of the large cantilever on the side tower. Longitudinal bridge coordinates The elevation of the bottom plate at the center line of the main beam at the end of the large cantilever on the side of the middle tower. Longitudinal bridge coordinates ;like Figure 5 As shown, the angle of the main beam end face at the end of the large cantilever on the middle tower side is calculated. Angle of the end face of the main beam at the end of the large cantilever on the side tower .

[0064] In specific embodiments, S7 and S8, the elevation adjustment and end face tilt angle adjustment of the stress-free closure of the large cantilever beam ends on the middle tower and side tower sides are characterized in that: the elevation adjustment and tilt angle adjustment of the stress-free closure of the large cantilever beam ends on the middle tower side are respectively , The elevation and tilt adjustment amounts for stress-free closure of the large cantilever beam end on the side tower are respectively , ;

[0065] in, This represents the percentage of the longitudinal slope of the route where the steel box girder of the closure section is located; , These are the installation elevations of the top of the steel box girder at the small and large mileage lifting points of the closure section, respectively. , These are the top plate elevations of the main beam centerline positions at the large cantilever ends of the central tower and side tower, measured before the closure. , These are the inclination angles of the main beam end faces at the large cantilever ends of the central tower and side towers, calculated before the closure.

[0066] In the specific implementation, in S9, the required cable force adjustment amounts for the two pairs of stay cables M1 and M2 near the closure point on the large cantilever side of the central tower are respectively , The cable tension adjustment amounts corresponding to the two pairs of stay cables S1 and S2 near the closure point on the side tower's large cantilever are respectively , The calculation process is as follows:

[0067] ;

[0068] In the formula, , , , To calculate intermediate process quantities; , For the overall model of the cable-stayed bridge, the tension adjustment of the two pairs of stay cables M1 and M2 on the large cantilever side of the middle tower near the closure point. , The corresponding change in elevation at the end of the large cantilever beam. , This represents the change in the inclination angle of the corresponding beam end face. , For the overall model, the cable tension of the two pairs of stay cables S1 and S2 near the closure point on the large cantilever of the side tower is adjusted. , The corresponding change in elevation at the end of the large cantilever beam. , This represents the change in the inclination angle of the corresponding beam end face. , This represents the changes in elevation and end face inclination of the large cantilever beam on the middle tower side caused by temporary counterweights in the overall model. , The changes in elevation and inclination angle of the large cantilever beam end on the side tower caused by temporary ballast are considered.

[0069] In a specific implementation, in S13, the theoretical cable force after the closure of the cable-stayed bridge is calculated using the overall model of the cable-stayed bridge construction stage.

[0070] In a specific implementation, in S10, the longitudinal temporary anchorage on the side tower of the main span of the closure is removed, while the longitudinal temporary anchorage of the middle tower is retained, so that the main beam of the main span on the closed side can undergo free deformation under the action of temperature.

[0071] Components not described in detail in this embodiment are all existing components that can be purchased through public channels.

[0072] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A control method suitable for flexible closure of a middle span of a three-tower steel box girder cable-stayed bridge, characterized in that, The method comprises the following steps: S1: establishing a finite element analysis model of the whole cable-stayed bridge in the construction stage; S2: predicting the closure gap temperature, considering the influence of the closure gap temperature and the construction method on the length of the closure gap, and correcting the length of the closure gap steel box girder; S3: establishing a single-beam finite element analysis model of the closure gap steel box girder according to the corrected length, calculating the relative elevations of the small mileage and large mileage girder end top plates and the adjacent lifting points and the inclination of the girder end face under the dead load, and determining the theoretical unstressed closure target posture; S4: calculating the girder top installation elevation of the small mileage and large mileage lifting point position of the closure gap steel box girder; S5: considering the longitudinal slope of the route The influence on the target attitude of closure is corrected on the target attitude of closure of the beam end. S6: when one side of the main span has the closure condition, measuring the top and bottom plate elevations and the longitudinal bridge direction coordinates of the main girder center line position at the end of the large cantilever of the side tower, calculating the end face inclination of the closure gap, and determining the elevation adjustment amount and the girder end inclination adjustment amount of the unstressed closure of the closure gap according to the measurement results; S7: determining the change amount of the closure gap elevation and the girder end inclination through the finite element model calculation and the adjustment of the cable force of the cable in the vicinity of the closure gap; S8: controlling the elevation error within ±10mm and the inclination error within 0.001 rad through the temporary pressure weight or the adjustment of the cable force of the cable; S9: lifting the closure gap steel box girder by using the deck crane on one side of the closure gap side tower, keeping the deck crane of the middle tower unchanged, embedding the closure gap to the closure gap for accurate alignment and matching, and then installing the temporary connection to lock the closure gap; S10: after the temporary locking of the closure gap, removing the longitudinal temporary anchoring of the side tower on one side of the closure, keeping the longitudinal temporary anchoring of the middle tower, and allowing the main girder on the side of the closure to freely deform under the action of temperature; S11: performing the girth seam welding of the closure gap, completing the closure of one side of the main span, and keeping the deck crane in the lifting state without unhooking; S12: when the other side of the main span has the closure condition, repeating steps S5-S9 to complete the closure of the other side of the main span; S13: after the closure of the whole bridge, unhooking the deck crane lifting the closure gap on both sides to complete the weight transfer of the closure gap; Removing the temporary load applied before the closure and adjusting the cable force of the cable adjusted before the closure to the theoretical cable force after the closure.

2. The control method for flexible closure of the middle span of a three-tower steel box girder cable-stayed bridge according to claim 1, characterized in that, In S2, the deviation value of the predicted closure gap temperature from the design reference temperature is calculated , the corrected steel box girder length of the closure gap is m; In the formula, Design length of steel box girder of closure section; Cantilever length of main girder from middle tower to closure gap; Cantilever length of main girder from side tower to closure gap; Linear expansion coefficient of steel box girder; 0.015 m is the length reserved for welding construction.

3. The control method for flexible closure of the middle span of a three-tower steel box girder cable-stayed bridge according to claim 1, characterized in that, In S3, the transverse diaphragm weight is applied in the form of a concentrated load on the corresponding node, the calculation model is corrected according to the actual weight, and general support boundary conditions are added to the node at the position of the lifting point in the calculation model; The relative elevation of the small mileage beam end top plate and the adjacent lifting point under the self-weight load and the beam end face inclination angle The relative elevation of the large mileage beam end and the adjacent lifting point and the beam end face inclination angle .

4. The control method for flexible closure of the middle span of a three-tower steel box girder cable-stayed bridge according to claim 1, characterized in that, In S4, according to the girder installation line shape, the small mileage and large mileage hoisting point position girder top installation elevation of the closure section steel box girder is calculated respectively as , ; , According to the design line shape, the pre-camber and the pavement thickness, the calculation is obtained.

5. The control method for flexible closure of the middle span of a three-tower steel box girder cable-stayed bridge according to claim 1, characterized in that, In S5, the longitudinal slope where the closure segment steel box girder is located is considered The influence on the closure target attitude is considered, and the relative elevation and end face inclination angle of the small mileage beam end after correction are 、 The relative elevation and end face inclination angle of the large mileage beam end are 、 ; is the linear expansion coefficient of the steel box girder, is the relative elevation of the top plate of the small mileage beam end and the adjacent hoisting point, is the end face inclination angle of the small mileage beam end, is the relative elevation of the top plate of the large mileage beam end and the adjacent hoisting point, is the end face inclination angle of the large mileage beam end.

6. The control method for flexible closure of the middle span of a three-tower steel box girder cable-stayed bridge according to claim 1, characterized in that, In S6, the total station is used to measure the elevation and longitudinal bridge direction coordinates of the center line position of the large cantilever end main beam of the middle tower and the side tower, and the end face inclination angle of the large cantilever end main beam is calculated. Specifically, the prism is placed at the top plate and the bottom plate position of the large cantilever end main beam at both sides of the closure opening, and the total station is used to measure the elevation and longitudinal bridge direction coordinates of the center line position of the large cantilever end main beam of the middle tower , the longitudinal bridge direction coordinates of the bottom plate elevation and the longitudinal bridge direction coordinates of the large cantilever end main beam of the middle tower side, the elevation and longitudinal bridge direction coordinates of the large cantilever end main beam of the middle tower side, the elevation and longitudinal bridge direction coordinates of the large cantilever end main beam of the middle tower side, the elevation and longitudinal bridge direction coordinates of the large cantilever end main beam of the middle tower side, the elevation and longitudinal bridge direction coordinates of the large cantilever end main beam of the middle tower side, the elevation and longitudinal bridge direction coordinates of the large cantilever end main beam of the middle tower side, the elevation and longitudinal bridge direction coordinates of the large cantilever end main beam of the middle tower side, the elevation and longitudinal bridge direction coordinates of the large cantilever end main beam of the middle tower side.

7. The control method for flexible closure of the middle span of a three-tower steel box girder cable-stayed bridge according to claim 1, characterized in that, In S7, the elevation adjustment amount and the end surface inclination adjustment amount of the stress-free closure of the closure gap, characterized in that the elevation adjustment amount and the inclination adjustment amount of the stress-free closure of the large cantilever beam end of the middle tower side are respectively , , the elevation adjustment amount and the inclination adjustment amount of the stress-free closure of the large cantilever beam end of the side tower side are respectively , ; is the linear expansion coefficient of the steel box girder, is the relative elevation of the top plate of the small mileage beam end and the adjacent hoisting point, is the end surface inclination of the small mileage beam end, is the relative elevation of the top plate of the large mileage beam end and the adjacent hoisting point, is the end surface inclination of the large mileage beam end; Wherein, is the percentage of the longitudinal slope of the route where the steel box girder is located; , are the girder top installation elevations of the small mileage and large mileage hoisting points of the steel box girder of the closure section, respectively; , are the top plate elevations of the main girder center line positions of the large cantilever end of the middle tower and the side tower before closure, respectively; , are the end face inclination angles of the main girder of the large cantilever end of the middle tower and the side tower calculated before closure, respectively.

8. The control method for flexible closure of the middle span of a three-tower steel box girder cable-stayed bridge according to claim 1, characterized in that, In S8, the adjustment amount of the cable force required by the two pairs of stay cables M1 and M2 of the middle tower side large cantilever near the closure gap is respectively , , the adjustment amount of the cable force corresponding to the two pairs of stay cables S1 and S2 of the side tower side large cantilever near the closure gap is respectively , ; the calculation process is as follows: ； In the formula, 、 、 、 is a calculation intermediate process quantity; 、 is the corresponding large cantilever beam end elevation change amount when the two pairs of stay cables M1 and M2 of the large cantilever on the side of the middle tower close to the closure gap are adjusted in the overall model of the cable-stayed bridge, 、 is the corresponding beam end face inclination change amount; 、 is the corresponding beam end face inclination change amount; 、 is the corresponding large cantilever beam end elevation change amount when the two pairs of stay cables S1 and S2 of the large cantilever on the side of the side tower close to the closure gap are adjusted in the overall model of the cable-stayed bridge, 、 is the corresponding beam end face inclination change amount; 、 is the corresponding beam end face inclination change amount; 、 is the corresponding large cantilever beam end elevation change amount and the beam end face inclination change amount caused by the temporary weight on the side of the middle tower in the overall model, 、 is the corresponding large cantilever beam end elevation change amount and the beam end face inclination change amount caused by the temporary weight on the side of the side tower, is the linear expansion coefficient of the steel box girder, is the relative elevation of the small mileage beam end roof and the adjacent lifting point, is the small mileage beam end face inclination, is the relative elevation of the large mileage beam end roof and the adjacent lifting point, is the large mileage beam end face inclination, is the percentage of the longitudinal slope of the route where the steel box girder of the closure section is located; 、 are the beam top installation elevations of the small mileage and large mileage lifting points of the steel box girder of the closure section, respectively; 、 are the roof elevations of the positions of the center lines of the main girders at the ends of the large cantilevers on the sides of the middle tower and the side tower measured before closure, 、 are the beam end face inclinations of the large cantilevers on the sides of the middle tower and the side tower calculated before closure.

9. The control method for flexible closure of the middle span of a three-tower steel box girder cable-stayed bridge according to claim 1, characterized in that, In S13, the theoretical cable force of the cable-stayed bridge after the closure is obtained through the whole model calculation in the construction stage of the cable-stayed bridge.

10. The control method for flexible closure of the middle span of a three-tower steel box girder cable-stayed bridge according to claim 1, characterized in that, In S10, the longitudinal temporary anchoring of the side tower on one side of the closure main span is removed, the longitudinal temporary anchoring of the middle tower is kept, and the main girder on the side of the closure can freely deform under the action of temperature. In S3, the transverse diaphragm weight is applied in the form of a concentrated load on the corresponding node, the calculation model is corrected according to the actual weight, and general support boundary conditions are added to the node at the position of the lifting point in the calculation model; In S13, the theoretical cable force of the cable-stayed bridge after the closure is obtained through the whole model calculation in the construction stage of the cable-stayed bridge. In S10, the longitudinal temporary anchoring of the side tower on one side of the closure main span is removed, the longitudinal temporary anchoring of the middle tower is kept, and the main girder on the side of the closure can freely deform under the action of temperature.

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