Control method suitable for flexible closure of midspan of three-tower steel box girder cable-stayed bridge

Abstract

The invention relates to a control method suitable for flexible closure of a midspan of a three-tower steel box girder cable-stayed bridge, which comprises the following steps: predicting the temperature of a closure gap, correcting the length of a closure section steel box girder, and determining a theoretical stress-free closure target attitude; when the main span on one side has the closure condition, measuring the elevation and the end face angle of the cantilever end main beams on the two sides of the closure gap, and determining the unstressed closure attitude adjustment amount through calculation; adjusting the elevation and the inclination angle of the main beam at the cantilever end to be consistent with a theoretical stress-free closure target posture in a temporary ballasting or stay cable force adjusting mode; the position of the tower side crane in the closure opening is not changed, and closure of the main span on one side is completed; the closure step is repeated, and closure of the other span of main beam is completed; and the bridge deck crane loosens the hook, and the cable force of the stay cable is adjusted to the theoretical cable force after closure. Compared with the prior art, the method has the advantages that the operation waiting time of large cantilever construction is shortened, the structural safety risk during construction is reduced, meanwhile, the construction efficiency is improved, and accurate closure of the steel box girder cable-stayed bridge is achieved.

Description

Technical Field

[0001] The present invention relates to the field of bridge construction control, and particularly to a control method suitable for flexible closure of the middle span of a three-tower steel box girder cable-stayed bridge. Background Art

[0002] In the traditional cable-stayed bridge construction technology, when the double main spans of a three-tower separated steel box girder cable-stayed bridge are closed, the closure sections of the two main spans usually adopt a symmetric synchronous closure method. This closure method mainly ensures the symmetry of the structural linear shape and the stress state, and avoids irreversible deviations in tower deviation, main girder linear shape, and internal force caused by asymmetric construction. However, the prerequisite for the symmetric synchronous closure of the double main spans is that the main girders of the three cable towers under cantilever construction have reached the maximum cantilever stage. If this prerequisite is not met, the situation of waiting for closure at the maximum cantilever will be faced, making the control of the wind resistance safety of the structure during the construction process face great challenges.

[0003] Currently, the hoisting construction of the closure section of a steel box girder cable-stayed bridge adopts the method of "lifting by cranes on both sides of the closure opening or lifting by a single crane on one side + counterweight on the other side", and the closure techniques mainly include the temperature matching cutting method and the jacking method. For the closure of the middle span of a three-tower cable-stayed bridge, no matter which closure section hoisting method and closure technique are adopted, it is required that the closure sections of the two main spans be hoisted symmetrically. The specific steps of its closure construction and control are as follows: (1) Continuously observing the dimensions and temperatures of the closure openings on both sides to determine control parameters such as the ideal closure temperature and the cutting length of the closure section; (2) Sensitivity analysis of each parameter of the closure opening to determine the adjustment measures for closure; (3) Cutting the closure section and transporting it to the position below the closure opening of the bridge; (4) Symmetrically and synchronously lifting the closure section by the cranes at the closure openings of the two main spans to below the closure opening; (5) Measuring the linear data of the closure opening and eliminating or reducing the linear deviation through control measures; (6) Waiting for the ideal closure temperature to be inserted into the closure opening, accurately matching the closure opening, and temporarily locking it; (7) Permanently welding and connecting, and the deck crane unhooks. The synchronous closure of the double main spans requires the linkage observation of the dimensions of the two closure openings. The closure adjustment measures and temperature changes have a mutual influence on the dimensions of the two closure openings, with a large correlation, and a high requirement for the synchronism of the crane hook lifting and lifting processes, which increases the difficulty of deformation measurement and linear control of the closure opening, resulting in problems such as a long closure construction period and low construction efficiency. If the cantilever construction progress is inconsistent, there is also an unfavorable situation of waiting for closure at the large cantilever. How to reduce the construction time of a long-span steel box girder cable-stayed bridge in the large cantilever state, achieve asynchronous flexible closure of the double main spans of a three-tower cable-stayed bridge, and improve the closure accuracy has become a common concern of builders. Summary of the Invention

[0004] The object of the present invention is to overcome the disadvantages of the existing technology, such as the unfavorable construction state of large cantilever waiting for closure due to different construction progress of the main girders of the three towers during cantilever construction, and the defects such as asymmetry of the structural linearity and internal force state caused by asynchronous closure. A control method for flexible closure of the mid-span of a three-tower steel box girder cable-stayed bridge is provided. At the closure joint, a single-side crane is used to hoist the closure segment steel box girder. By means of temporary ballast and local stay cable force adjustment, the stress-free closure state of the main girder is ensured, that is, the elastic curve of the main girder at the closure is continuous. This technology does not need to consider the problem of symmetric synchronous closure of the double main spans of the three-tower steel box girder cable-stayed bridge, that is, one side of the main span can be closed first or the two sides of the main span can be closed synchronously, avoiding the structural wind resistance safety risk faced by the unfavorable state of large cantilever waiting for closure of the cable-stayed bridge due to construction progress differences, improving the construction efficiency, and reflecting the flexibility of closure control.

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

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

[0007] S2: Predict the temperature at the closure joint, consider the influence of the temperature at the closure joint and the construction method on the length of the closure segment, and correct the length of the closure segment steel box girder; Before the construction reaches the closure stage, predict the temperature at the closure joint according to historical meteorological data, and calculate the deviation value from the design reference temperature.

[0008] S3: Establish a single-beam finite element analysis model of the closure segment steel box girder according to the corrected beam length, calculate the relative elevation of the top and bottom plates of the beam ends at the small mileage and large mileage and the inclination angle of the beam end face near the lifting points under the self-weight load (longitudinal uniform load of the main girder and concentrated load of the diaphragm), and determine the theoretical stress-free closure target attitude; The magnitude and distribution of the load are determined according to the design drawings, and the lifting point positions of the closure segment steel box girder are determined according to the construction plan. At the same time, the influence of the longitudinal slope of the main girder on the closure target attitude is considered.

[0009] S4: Calculate the installation elevation of the beam top at the lifting point positions of the small mileage and large mileage of the closure segment steel box girder;

[0010] S5: Consider the influence of the longitudinal slope i% on the closure target attitude, and correct the closure target attitude (relative elevation and inclination angle of the beam end face) of the beam end;

[0011] S6: When one side of the main span meets the closure condition, use a total station to measure the elevation of the top and bottom plates and the longitudinal bridge coordinates of the center line position of the main girder at the end of the large cantilever on the side of the middle tower and the side tower, calculate the inclination angle of the main girder end face at the end of the large cantilever, and determine the elevation adjustment amount and the inclination angle adjustment amount of the stress-free closure of the main girder end on the side of the middle tower and the side tower according to the measurement results;

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

[0013] S8: Change the cable forces of the two pairs of stay cables on the large cantilevers of the middle tower and side tower close to the closure gap respectively in the overall model, and check the elevation change and the inclination change of the end face of the large cantilever beam caused by the change of the cable forces of the two pairs of stay cables respectively;

[0014] S9: Calculate the required cable force adjustment of the stay cables on the middle tower side and side tower side, adjust the cable forces of the stay cables on site, and control the elevation error within ±10 mm and the inclination error within 0.001 rad;

[0015] S10: Use the deck crane on the side tower of the closure gap to lift the closure segment steel box girder. The position of the deck crane on the middle tower remains unchanged. Lifting the closure segment has no impact on the force and deformation of the middle tower structure, thus ensuring the symmetry of the force and alignment of the middle tower structure; After lifting the closure segment and embedding it into the closure gap for precise alignment and matching, install temporary connections to lock the closure gap;

[0016] S11: Carry out the circumferential welding of the closure segment. After one side of the main span is closed, the deck crane remains in the lifting state and does not release the hook;

[0017] S12: When the other side of the main span meets the closure conditions, repeat steps S5 - S9 to complete the closure of the other side of the main span;

[0018] S13: After the whole bridge is closed, release the hook of the deck crane for lifting the closure segment on both sides to complete the weight transfer of the closure segment, install the longitudinal limit bearing or damper of the middle tower, and remove the longitudinal temporary anchorage of the middle tower; Remove the temporary loads applied before closure, and adjust the cable forces of the stay cables adjusted before closure to the theoretical cable forces after closure.

[0019] Furthermore, in S2, calculate the deviation value ΔT between the predicted temperature of the closure gap and the design reference temperature. The corrected length of the closure segment steel box girder is [L - (L 1 +L 2 )·ΔT·α - 2×0.015] m;

[0020] In the formula, L is the designed length of the closure segment steel box girder; L 1 is the cantilever length of the main girder from the middle tower to the closure gap; L 2 is the cantilever length of the main girder from the side tower to the closure gap; α is the linear expansion coefficient of the steel box girder; 0.015 m is the reserved welding construction length.

[0021] Further, in S3, the weight of the diaphragm is applied to the corresponding nodes in the form of a concentrated load. The weight of the steel box girder model is adjusted according to the design drawings to ensure that the weight of the steel box girder in the closure section is consistent with the design drawings, and general support boundary conditions are added to the nodes at the positions of the suspension points in the model. From the model calculation, under the self-weight load, the relative elevation Δh 1 and the end face inclination angle θ 1 of the small mileage beam end and the adjacent suspension point are obtained. The relative elevation Δh 2 and the end face inclination angle θ 2 of the large mileage beam end and the adjacent suspension point are obtained.

[0022] Further, in S4, according to the installation alignment of the main girder, the installation elevations of the beam tops at the suspension point positions of the small mileage and large mileage of the steel box girder in the closure section are calculated as H 1 and H 2 respectively; H 1 and H 2 are calculated according to the design alignment, pre-camber and paving thickness.

[0023] Further, in S5, considering the influence of the longitudinal slope i% of the route where the steel box girder in the closure section is located on the closure target attitude, the closure target attitude (relative elevation and end face inclination angle of the beam end) is corrected. After correction, the relative elevation and end face inclination angle of the small mileage beam end are respectively The relative elevation and end face inclination angle of the large mileage beam end are respectively

[0024] Further, in S6, the elevation of the top and bottom plates and the longitudinal bridge coordinates of the center line of the main girder at the end of the large cantilever on the middle tower and side tower sides are measured using a total station, and the end face inclination angle of the main girder at the end of the large cantilever is calculated. Specifically: The prism is placed at the positions of the top and bottom plates of the main girder at the ends of the cantilevers on both sides of the closure gap, and the elevation of the top plate at the center line position of the main girder at the end of the large cantilever on the middle tower side is measured using a total station The longitudinal bridge coordinates The elevation of the bottom plate at the center line position of the main girder at the end of the large cantilever on the middle tower side The longitudinal bridge coordinates And the elevation of the top plate at the center line position of the main girder at the end of the large cantilever on the side tower side The longitudinal bridge coordinates The elevation of the bottom plate at the center line position of the main girder at the end of the large cantilever on the side tower side The longitudinal bridge coordinates The end face angle of the main girder at the end of the large cantilever on the middle tower side is calculated The end face angle of the main girder at the end of the large cantilever on the side tower side

[0025] Further, in S7 and S8, the elevation adjustment amount and end face inclination adjustment amount of the mid-tower and side-tower side large cantilever beam ends during stress-free closure are characterized in that: the elevation adjustment amount and inclination adjustment amount of the mid-tower side large cantilever beam end during stress-free closure are respectively The elevation adjustment amount and inclination adjustment amount of the side-tower side large cantilever beam end during stress-free closure are respectively

[0026]

[0027] wherein, i is the percentage of the longitudinal slope of the route where the closure segment steel box girder is located; H 1 、H 2 are respectively the installed elevation of the beam top at the hoisting points of the small mileage and large mileage of the closure segment steel box girder; are respectively the elevation of the top plate at the center line position of the main beam at the ends of the mid-tower and side-tower side large cantilevers measured before closure; θ 1 ', θ 2 ' are respectively the end face inclination angles of the main beam at the ends of the mid-tower and side-tower side large cantilevers calculated before closure.

[0028] Further, in S9, the cable force adjustment amounts required for the two pairs of stay cables M1 and M2 on the mid-tower side large cantilever near the closure opening are respectively δ M1 ·ΔN M1 、δ M2 ·ΔN M2 , and the cable force adjustment amounts corresponding to the two pairs of stay cables S1 and S2 on the side-tower side large cantilever near the closure opening are respectively δ S1 ·ΔN S1 、δ S2 ·ΔN S2 ; the calculation process is as follows:

[0029]

[0030] In the formula, δ M1 、δ M2 、δ S1 、δ S2 are intermediate calculation quantities; ΔH M1 、ΔH M2 are the elevation change amounts of the large cantilever beam ends corresponding to the cable force adjustments ΔN M1 、ΔN M2 of the two pairs of stay cables M1 and M2 on the mid-tower side large cantilever near the closure opening in the integral model of the cable-stayed bridge, and Δθ M1 、Δθ M2 are the corresponding end face inclination change amounts; ΔH S1 、ΔH S2 are the elevation change amounts of the large cantilever beam ends corresponding to the cable force adjustments ΔN S1 、ΔN S2 of the two pairs of stay cables S1 and S2 on the side-tower side large cantilever near the closure opening in the integral modelThe elevation change of the large cantilever beam end corresponding to S1 , Δθ S2 is the change in the inclination angle of the beam end face corresponding thereto; ΔH G1 , Δθ G1 are the elevation change and the inclination angle change of the large cantilever beam end on the middle tower side caused by the temporary ballast in the overall model, ΔH G2 , Δθ G2 are the elevation change and the inclination angle change of the large cantilever beam end on the side tower side caused by the temporary ballast.

[0031] Furthermore, in S13, the theoretical cable force after the cable-stayed bridge is closed is calculated from the overall model of the cable-stayed bridge construction stage.

[0032] Furthermore, in S10, the longitudinal temporary anchorage on the side tower side of the closed main span is removed, and the longitudinal temporary anchorage of the middle tower is retained, so that the main beam of the closed side of the main span can deform freely under the action of temperature.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] (1) The present invention does not need to follow the requirement of synchronous closure of the two main span closure segments. When one main span meets the closure condition, the closure can be carried out first; when both main spans meet the closure condition at the same time, the closure can also be carried out synchronously, which greatly reduces the duration of the unfavorable wind-resistant state when the steel box girder cable-stayed bridge with system flexibility waits for closure in the large cantilever state and reduces the safety risk during the structural construction process.

[0035] (2) A calculation method for adjusting the elevation of the main beam at the closure joint and the deviation of the stress-free inclination angle during the flexible asynchronous closure of the double main spans is provided. During the closure process of the main beam, the cable force adjustment data is determined in advance, and the number of on-site measurement data is small, and the closure can be completed in a short time, effectively avoiding large changes in the on-site temperature and thus affecting the closure accuracy and quality.

[0036] (3) This closure method ensures the continuity of the elastic curve of the main beam, so that the final structural internal force formed is independent of the structural formation process, that is, the construction method of asynchronous closure of the double main spans does not affect the final structural internal force. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic diagram of the overall finite element analysis model of the cable-stayed bridge construction stage.

[0038] Figure 2 is a schematic diagram of the corrected steel box girder length of the closure segment considering the temperature at the closure joint and the construction method.

[0039] Figure 3 is a schematic diagram of the single beam finite element analysis model of the steel box girder of the closure segment established according to the corrected beam length.

[0040] Figure 4 To study the influence of the longitudinal slope of the route where the closure segment steel box girder is located on the target attitude of closure, the target attitude of the beam ends for closure (relative elevation and inclination angle of the beam end face) is corrected. The schematic diagrams of the relative elevation of the beam ends at the short mileage and long mileage and the inclination angle of the beam end face after correction are shown.

[0041] Figure 5 Schematic diagram of the elevation of the top and bottom plates and the longitudinal bridge coordinates of the center line of the main girder at the end of the large cantilever for measuring the closure joint of the main span on the side where the closure condition is met using a total station.

[0042] Figure 6 Schematic diagram of using the crane on the side tower to lift the closure segment steel box girder with the position of the crane on the middle tower side unchanged during closure. Specific implementation manner

[0043] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. In the technical solution of the present invention, components such as model numbers, material names, connection structures, control methods, algorithms, etc. that are not clearly described are regarded as common technical features disclosed in the prior art.

[0044] Embodiment 1

[0045] The present invention provides a control method suitable for the flexible closure of the middle span of a three-tower steel box girder cable-stayed bridge, including the following steps:

[0046] S1: Establish an overall finite element analysis model for the construction stage of the cable-stayed bridge; the model is as Figure 1 shown.

[0047] S2: Predict the temperature of the closure joint, consider the influence of the temperature of the closure joint and the construction method on the length of the closure segment, and correct the length of the closure segment steel box girder; before the on-site construction reaches the closure stage, predict the temperature of the closure joint according to historical meteorological data and calculate the deviation value from the design reference temperature.

[0048] S3: Establish a single-beam finite element analysis model of the closure segment steel box girder according to the corrected beam length. The model is as Figure 3 shown. Calculate the relative elevation of the top plate of the beam ends at the short mileage and long mileage and the adjacent lifting points and the inclination angle of the beam end face under the self-weight load (longitudinal uniform load of the main girder and concentrated load of the diaphragm), and determine the theoretical stress-free closure target attitude; the magnitude and distribution of the load are determined according to the design drawings, and the lifting point positions of the closure segment steel box girder are determined according to the construction plan. At the same time, consider the influence of the longitudinal slope of the main girder on the closure target attitude.

[0049] S4: Calculate the installation elevation of the beam top at the lifting point positions of the short mileage and long mileage of the closure segment steel box girder;

[0050] S5: Consider the influence of the longitudinal slope i% of the route on the closing target attitude, and correct the closing target attitude of the beam end (relative elevation and beam end end face inclination angle).

[0051] S6: When one side of the main span meets the closing conditions, use a total station to measure the elevation of the top and bottom plates and the longitudinal bridge coordinates at the center line position of the main beam at the end of the large cantilever on the side of the middle tower and the side tower, calculate the end face inclination angle of the main beam at the end of the large cantilever, and determine the elevation adjustment amount and the beam end end face inclination angle adjustment amount for stress-free closing of the main beam at the end of the middle tower and the side tower according to the measurement results.

[0052] S7: Determine the change amount of the elevation and beam end inclination angle of the closure gap through calculation using a finite element model for the temporary counterweight at the closure gap or the cable force adjustment of the stay cables near the closure gap.

[0053] S8: Control the elevation error within ±10 mm and the inclination angle error within 0.001 rad on-site by means of temporary counterweight or adjusting the cable force of the stay cables.

[0054] S9: Use the deck crane on one side of the side tower at the closure gap to lift the closure segment steel box girder. The position of the deck crane at the middle tower remains unchanged. Lifting the closure segment has no impact on the force and deformation of the middle tower structure, thus ensuring the symmetry of the force and alignment of the middle tower structure. After lifting the closure segment and inserting it into the closure gap for precise alignment and matching, install temporary connections to lock the closure gap; as Figure 6 shown.

[0055] S10: After the temporary locking of the closure segment, remove the longitudinal temporary anchor at the side tower on the closure side, and retain the longitudinal temporary anchor at the middle tower, so that the main beam on the closed side can deform freely under the action of temperature.

[0056] S11: Carry out the circumferential seam welding of the closure segment. When one side of the main span is closed, the deck crane remains in the lifting state and does not release the hook.

[0057] S12: When the other side of the main span meets the closing conditions, repeat steps S5 - S9 to complete the closing of the other side of the main span.

[0058] S13: After the whole bridge is closed, release the hook of the deck crane for lifting the closure segment on both sides to complete the weight transfer of the closure segment, install the longitudinal limit bearing or damper at the middle tower, and remove the longitudinal temporary anchor at the middle tower; remove the temporary load applied before closing, and adjust the cable force of the stay cables adjusted before closing to the theoretical cable force after closing.

[0059] In the specific implementation manner, as Figure 2 shown, in S2, calculate the deviation value ΔT between the predicted temperature at the closure gap and the design reference temperature. The corrected length of the closure segment steel box girder is [L - (L 1 +L 2 )·ΔT·α - 2×0.015] m;

[0060] In the formula, L is the designed length of the closure segment steel box girder; L 1 is the cantilever length of the main girder from the middle tower to the closure joint; L 2 is the cantilever length of the main girder from the side tower to the closure joint; α is the linear expansion coefficient of the steel box girder; 0.015 m is the reserved welding construction length.

[0061] In the specific implementation manner, in S3, the weight of the diaphragm is applied to the corresponding nodes in the form of concentrated loads, and the weight of the steel box girder model is adjusted according to the design drawings to ensure that the weight of the closure segment steel box girder is consistent with the design drawings, and general support boundary conditions are added to the nodes at the positions of the lifting points in the model; from the model calculation, under the self-weight load, the relative elevation Δh 1 between the top plate of the small mileage beam end and the adjacent lifting point and the end face inclination angle θ 1 are obtained; for the large mileage beam end, the relative elevation Δh 2 between the top plate of the large mileage beam end and the adjacent lifting point and the end face inclination angle θ 2 are obtained. According to the construction plan, determine the position of the lifting point for hoisting the closure segment steel box girder (assuming the distance from the lifting point to the beam end is a), add general support boundary conditions to the nodes at the positions of the lifting points in the model, and calculate the relative elevation Δh 1 between the top plate of the small mileage beam end and the adjacent lifting point and the end face inclination angle θ 1 , for the large mileage beam end, the relative elevation Δh 2 between the top plate of the large mileage beam end and the adjacent lifting point and the end face inclination angle θ 2 , and determine the theoretical stress-free closure target attitude. (When the temporary lifting point is higher than the top plate of the beam end, Δh 1 , Δh 2 are positive, otherwise negative; when the beam end section can be obtained by rotating counterclockwise from the vertical section, θ 1 , θ 2 are positive, otherwise negative.)

[0062] In the specific implementation manner, in S4, according to the installation alignment of the main girder, calculate the installation elevations of the top of the lifting points of the small mileage and large mileage of the closure segment steel box girder to be H 1 , H 2 ; H 1 , H 2 are calculated according to the design alignment, camber and paving thickness.

[0063] In the specific implementation manner, in S5, considering the influence of the longitudinal slope i% of the route where the closure segment steel box girder is located on the closure target attitude, correct the closure target attitude (relative elevation and end face inclination angle of the beam end), and after correction, the relative elevation and end face inclination angle of the small mileage beam end are respectively The relative elevation and end face inclination angle of the large mileage beam end are respectively Such asFigure 4 as shown

[0064] In the specific implementation manner, in S6, the elevation of the top and bottom plates and the longitudinal bridge coordinate at the center line position of the main girder at the end of the large cantilever on the middle tower and side tower sides are measured by using a total station, and the end face inclination angle of the main girder at the end of the large cantilever is calculated. Specifically: Place the prism at the positions of the top and bottom plates of the main girder at the ends of the two cantilevers on both sides of the closure gap, and use the total station to measure the elevation of the top plate at the center line position of the main girder at the end of the large cantilever on the middle tower side longitudinal bridge coordinate elevation of the bottom plate at the center line position of the main girder at the end of the large cantilever on the middle tower side longitudinal bridge coordinate and the elevation of the top plate at the center line position of the main girder at the end of the large cantilever on the side tower side longitudinal bridge coordinate elevation of the bottom plate at the center line position of the main girder at the end of the large cantilever on the middle tower side longitudinal bridge coordinate as Figure 5 shown, calculate the end face angle of the main girder at the end of the large cantilever on the middle tower side end face angle of the main girder at the end of the large cantilever on the side tower side

[0065] In the specific implementation manner, in S7 and S8, the elevation adjustment amount and end face inclination adjustment amount for stress-free closure of the large cantilever beam ends on the middle tower and side tower sides are characterized in that: the elevation adjustment amount and inclination adjustment amount for stress-free closure of the large cantilever beam end on the middle tower side are respectively the elevation adjustment amount and inclination adjustment amount for stress-free closure of the large cantilever beam end on the side tower side are respectively

[0066]

[0067] wherein, i is the percentage of the longitudinal slope of the steel box girder in the closure section; H 1 、H 2 are respectively the installed elevation of the beam top at the suspension point positions of the small mileage and large mileage of the steel box girder in the closure section; are respectively the elevation of the top plate at the center line position of the main girder at the end of the large cantilever on the middle tower and side tower sides measured before closure; θ 1 ', θ 2 ' are respectively the end face inclination angles of the main girder at the end of the large cantilever on the middle tower and side tower sides calculated before closure.

[0068] In the specific implementation manner, in S9, the cable force adjustment amounts required for the two pairs of stay cables M1 and M2 on the middle tower side of the large cantilever near the closure gap are respectively δ M1 ·ΔN M1 、δ M2 ·ΔN M2 , and the cable force adjustment amounts corresponding to the two pairs of stay cables S1 and S2 on the side tower side of the large cantilever near the closure gap are respectively δ S1 ·ΔNS1 、 δ S2 ·ΔN S2 ; The calculation process is as follows:

[0069]

[0070] In the formula, δ M1 、 δ M2 、 δ S1 、 δ S2 are intermediate calculation quantities; ΔH M1 、 ΔH M2 are the changes in the elevation of the large cantilever beam end corresponding to the cable force adjustments ΔN M1 、 ΔN M2 of the two pairs of stay cables M1 and M2 near the closure joint on the middle tower side in the overall cable-stayed bridge model, and Δθ M1 、 Δθ M2 are the corresponding changes in the inclination angle of the beam end face; ΔH S1 、 ΔH S2 are the changes in the elevation of the large cantilever beam end corresponding to the cable force adjustments ΔN S1 、 ΔN S2 of the two pairs of stay cables S1 and S2 near the closure joint on the side tower side in the overall model, and Δθ S1 、 Δθ S2 are the corresponding changes in the inclination angle of the beam end face; ΔH G1 、 Δθ G1 are 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 temporary ballast in the overall model, and ΔH G2 、 Δθ G2 are 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 temporary ballast on the side tower side.

[0071] In the specific implementation manner, in S13, the theoretical cable force after the cable-stayed bridge is closed is calculated by the overall model of the cable-stayed bridge construction stage.

[0072] In the specific implementation manner, in S10, the longitudinal temporary anchor on the side tower side of the closed main span is removed, and the longitudinal temporary anchor of the middle tower is retained, so that the main beam on the side of the closed main span can deform freely under the action of temperature.

[0073] The components not described in detail in this embodiment are all existing components that can be purchased through public channels.

[0074] The above description of the embodiments is to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and all improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A control method for flexible closure of mid-span of a three-tower steel box girder cable-stayed bridge, characterized in that: The following steps are involved: S1: Establish the overall finite element analysis model of the cable-stayed bridge during the construction phase; S2: Predict the closure mouth temperature, consider the influence of closure mouth temperature and construction method on the length of closure section, and correct the length of steel box girder of closure section; S3: According to the corrected beam length, a single beam model of the steel box beam at the closure section is established by finite element analysis. The relative elevations of the top plates at the small and large mileage beam ends and the adjacent hanging points and the inclination angles of the beam ends are calculated under the deadweight load to determine the theoretical stress-free closure target posture. S4: Calculate the installation elevation of the top of the steel box girder at the small and large mileage lifting points of the joint section; S5: Considering the influence of the longitudinal slope i% of the route on the target posture of the joint, the target posture of the joint at the beam end is corrected; S6: When the main span on one side meets the conditions for closure, measure the top and bottom plate elevations and longitudinal bridge coordinates of the centerline of the main beams at the ends of the large cantilever at the middle tower and side tower sides, calculate the end face inclination angle of the closure, and determine the elevation adjustment amount of the stress-free closure of the main beams at both ends of the closure and the beam end inclination adjustment amount based on the measurement results; S7: Determine the change in the closure elevation and the beam end inclination caused by the temporary weight of the closure or the adjustment of the cable force of the inclined cable near the closure through finite element model calculation; S8: By temporarily pressing weight or adjusting the cable tension on site, the elevation error is controlled within ±10mm and the inclination error is controlled within 0.001rad; S9: Use the bridge crane on the side tower of the joint opening to lift the steel box girder of the joint section, and the bridge crane on the middle tower remains in the same position; lift the joint section and insert it into the joint opening for precise alignment and matching, and then install a temporary connection to lock the joint opening; S10: After the joint section is temporarily locked, the temporary longitudinal anchorage of the side tower on the joint side is removed, and the temporary longitudinal anchorage of the middle tower is retained, so that the main beam on the jointed side can deform freely under the action of temperature. S11: Carry out circumferential welding of the closure section, complete closure of the main span on one side, and keep the bridge crane in the hoisting state without loosening the hook; S12: When the main span on the other side meets the conditions for closure, repeat steps S5 to S9 to complete the closure of the main span on the other side; S13: After the entire bridge is closed, the bridge cranes on both sides that lift the closed section are unhooked to complete the weight transfer of the closed section; Remove the temporary loads applied before closure and adjust the cable tension adjusted before closure to the theoretical cable tension after closure.

2. A control method for flexible closure of mid-span of a three-tower steel box girder cable-stayed bridge according to claim 1, characterized in that: In S2, the deviation ΔT between the predicted closure mouth temperature and the design reference temperature is calculated, and the length of the steel box girder in the closure section after correction is [L-(L1+L2)·ΔT·α-2×0.015]m; Wherein, L is the design length of the steel box girder in the joint section; L1 is the cantilever length of the main beam from the middle tower to the joint mouth; L2 is the cantilever length of the main beam from the side tower to the joint mouth; α is the linear expansion coefficient of the steel box girder; 0.015m is the reserved welding construction length.

3. The control method for flexible closure of mid-span of a three-tower steel box girder cable-stayed bridge according to claim 1, characterized in that: In S3, the weight of the diaphragm is applied to the corresponding nodes in the form of concentrated load, the calculation model is reweighted according to the actual weight, and general support boundary conditions are added to the nodes where the hanging points are located in the calculation model; The calculation results show that under the deadweight load, the relative elevation Δh1 between the top plate of the small mileage beam end and the adjacent hanging point and the inclination angle θ1 of the beam end, and the relative elevation Δh2 between the large mileage beam end and the adjacent hanging point and the inclination angle θ2 of the beam end.

4. The control method for flexible closure of mid-span of a three-tower steel box girder cable-stayed bridge according to claim 1, characterized in that: In S4, according to the main beam installation line shape, the beam top installation elevations of the small and large mileage lifting points of the steel box beam in the joint section are calculated to be H1 and H2 respectively; H1 and H2 are calculated based on the design line shape, pre-camber and paving thickness.

5. The control method for flexible closure of mid-span of a three-tower steel box girder cable-stayed bridge according to claim 1, characterized in that: In S5, the influence of the longitudinal slope i% of the steel box girder in the closure section on the target posture of the closure is considered, and the target posture of the closure of the beam end is corrected. After the correction, the relative elevation of the beam end at the small mileage and the inclination angle of the beam end are The relative elevation of the long-mileage beam end and the inclination angle of the beam end are 6. The control method for flexible closure of mid-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 top and bottom plate elevations and longitudinal bridge coordinates of the centerline position of the main beams at the ends of the large cantilever at the middle tower and side tower, and the end face inclination angle of the main beam at the ends of the large cantilever is calculated. Specifically, the prism is placed at the top and bottom plates of the main beams at the ends of the cantilever on both sides of the joint, and the total station is used to measure the top plate elevation of the centerline position of the main beam at the ends of the large cantilever at the middle tower. Longitudinal bridge coordinates Bottom plate elevation of the center line of the main beam at the end of the large cantilever on the middle tower side Longitudinal bridge coordinates And the top plate elevation of the centerline of the main beam at the end of the large cantilever on the side tower Longitudinal bridge coordinates Bottom plate elevation of the center line of the main beam at the end of the large cantilever on the middle tower side Longitudinal bridge coordinates Calculate the end angle of the main beam at the end of the large cantilever on the middle tower side The end angle of the main beam at the large cantilever end of the side tower 7. The control method for flexible closure of mid-span of a three-tower steel box girder cable-stayed bridge according to claim 1, characterized in that: In S7, the height adjustment amount and the end face inclination adjustment amount of the stress-free closure of the closure mouth are characterized in that: the height adjustment amount and the inclination adjustment amount of the stress-free closure of the large cantilever beam end on the middle tower side are respectively The height adjustment and inclination adjustment of the stress-free closure at the end of the large cantilever beam on the side tower are Among them, i is the percentage of the longitudinal slope of the line where the joint section steel box girder is located; H1 and H2 are the beam top installation elevations of the small mileage and large mileage lifting points of the joint section steel box girder respectively; They are the top plate elevations of the centerline positions of the main beams at the ends of the large cantilevers on the middle tower and side towers measured before closure; θ1' and θ2' are the end face inclination angles of the main beams at the ends of the large cantilevers on the middle tower and side towers calculated before closure.

8. The control method for flexible closure of mid-span of a three-tower steel box girder cable-stayed bridge according to claim 1, characterized in that: In S8, the cable force adjustment required for the two pairs of inclined cables M1 and M2 near the closure of the large cantilever on the middle tower side is δ M1 ΔN M1 , δ M2 ΔN M2 The cable force adjustment values ​​of the two pairs of inclined cables S1 and S2 on the side tower of the large cantilever near the joint mouth are δ S1 ΔN S1 , δ S2 ΔN S2 ; The calculation process is as follows: In the formula, δ M1 , δ M2 , δ S1 , δ S2 To calculate the intermediate process quantity; ΔH M1 , ΔH M2 The cable force adjustment ΔN of the two pairs of cables M1 and M2 near the closure of the large cantilever on the middle tower side in the overall model of the cable-stayed bridge M1 , ΔN M2 The corresponding change in elevation of the cantilever beam end is Δθ M1 , Δθ M2 is the corresponding change in the inclination angle of the beam end surface; ΔH S1 , ΔH S2 The force adjustment ΔN of the two pairs of inclined cables S1 and S2 near the closure of the large cantilever on the side tower in the overall model S1 , ΔN S2 The corresponding change in elevation of the cantilever beam end is Δθ S1 , Δθ S2 is the corresponding change in the inclination angle of the beam end surface; ΔH G1 , Δθ G1 is the change in elevation of the large cantilever beam end and the change in the inclination angle of the beam end caused by the temporary pressure in the overall model, ΔH G2 , Δθ G2 It is the change in elevation of the large cantilever beam end on the side tower and the change in the inclination angle of the beam end caused by temporary weight.

9. The control method for flexible closure of mid-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 closure is calculated by the overall model of the cable-stayed bridge during the construction stage.

10. The control method for flexible closure of mid-span of a three-tower steel box girder cable-stayed bridge according to claim 1, characterized in that: In S10, the temporary longitudinal anchorage on the side tower of the main span that has been closed is removed, and the temporary longitudinal anchorage on the middle tower is retained, so that the main beam of the main span on the closed side can deform freely under the action of temperature.

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