Construction linear control method of large-span non-equal-span cast-in-situ box girder

Abstract

The application discloses a construction linear control method for a large-span non-equal-span cast-in-situ box girder, and comprises the following measures: pre-camber optimization, theoretical deflection simulation based on a coupling model of the box girder and a movable formwork, model correction combined with pre-test, and selection of a sectional pre-camber design curve according to the span stiffness difference; deformation collaborative control, concrete pouring according to a layered sequence, control of the bottom form elevation and pouring interval time, and synchronous monitoring and coordination of the deformation of the movable formwork and the box girder; inter-span constraint control, rigid connection structure arranged in the unequal-span connection area to constrain the non-longitudinal displacement, and review of the elevation difference at the connection after pouring; stress adaptation control, real-time monitoring of the deflection and stress of the stress concentration area, and control through adjustment of the formwork elevation, adjustment of the pouring rhythm or addition of local reinforcing structure when the data is out of limit. The method can ensure that the bridge linear shape meets the design requirements and reduce the risk of structural stress concentration.

Description

Technical Field

[0001] This invention relates to the field of bridge construction technology, and in particular to a method for controlling the construction alignment of large-span non-equal-span cast-in-place box girders. Background Technology

[0002] In the construction of long-span cast-in-place box girders with unequal spans, the moving formwork method is widely used due to its continuous operation and strong adaptability. However, the structural layout with unequal spans poses unique challenges to the setting of pre-camber and the control of alignment throughout the construction process. The existing technology usually has the following limitations: (1) It often uses empirical formulas or single-condition simulation results of equal-span bridges, without fully considering the stiffness differences and additional internal forces caused by non-equal-span combinations, resulting in mismatch between the pre-camber curve and the actual deformation, and the linear deviation of mid-span deflection or support elevation; (2) It has not established a coordinated deformation control system for the moving formwork and the box girder. The cumulative effect of formwork deflection, support settlement and concrete layered pouring deformation is superimposed, and the deflection of the whole bridge pouring stage is easy to exceed the standard limit; (3) Additional stress is generated at the non-equal-span connection due to the sudden change in stiffness. The traditional linear control does not combine the stress distribution law, which is easy to cause the stress to exceed the limit at the junction of the web and the bottom plate, the corbel support area and other parts; (4) During the construction process, it does not make real-time corrections for the time-varying characteristics such as the increase of concrete age and the evolution of elastic modulus, and it is difficult to cope with the stage changes of load transfer in non-equal-span construction.

[0003] To overcome the above-mentioned shortcomings, this invention aims to provide a comprehensive method that integrates precise pre-camber optimization and multi-dimensional collaborative control, so as to achieve the dual goals of high-precision control of the construction alignment of non-equal span box girders and structural safety. Summary of the Invention

[0004] The main technical problem to be solved by this invention is to provide a construction alignment control method for large-span non-equal-span cast-in-place box girders, so as to ensure that the completed bridge alignment meets the design requirements while reducing the risk of structural stress concentration.

[0005] To address the aforementioned technical problems, this invention provides a method for controlling the construction alignment of large-span non-equidistant cast-in-place box girders, comprising the following measures:

[0006] Measure 1: Pre-camber optimization

[0007] Based on the coupled model of non-equal span box girder and moving formwork, the theoretical deflection of box girders with different spans during the layered casting construction process is simulated and calculated; a pre-stressing test is carried out on at least one span of box girder, and the simulation parameters of the coupled model are corrected based on the comparison results of measured deflection and theoretical deflection; according to the structural stiffness difference of different spans, a segmented pre-camber design curve matching the span is selected.

[0008] Measure 2: Deformation Coordination Control

[0009] Concrete is poured in a pre-defined layered sequence, and the following steps are taken during the pouring process: the elevation of the bottom formwork is positioned within the design limit; the interval between layer pours is controlled within the range of concrete age to control the difference in deformation between layers; the deflection of the box girder that has been constructed in each construction stage is monitored; the deflection of the moving formwork is monitored simultaneously, and construction parameters are adjusted to coordinate the deformation of the moving formwork with that of the box girder.

[0010] Measure 3: Inter-border constraint control

[0011] In the connection area between two adjacent box girders with different spans, a rigid connection structure is set to constrain the relative displacement of the area in the non-longitudinal direction of the bridge, and to suppress the linear abrupt change of the precamber curve of different spans at the connection point; after the casting is completed, the elevation difference between the box girders on both sides of the connection area is checked.

[0012] Measure 4: Stress Adaptation Control

[0013] Throughout the construction process, the deflection and stress in the stress concentration areas of the structure are monitored in real time. When the monitoring data deviates from the preset threshold, the stress and alignment are controlled to match the design value through a construction adjustment mechanism. The construction adjustment mechanism includes one or more of the following measures: adjusting the elevation of the movable formwork; adjusting the pouring rhythm; and adding local reinforcement structures.

[0014] In a preferred embodiment, in measure 1, the coupling model adopts a finite element analysis model based on hybrid element partitioning, including tetrahedral elements arranged at the junction of the web and bottom plate, top plate, and complex areas including the support anchorage area, and hexahedral elements arranged in regular areas including the top plate and bottom plate.

[0015] In a preferred embodiment, in measure 1, when simulating the coupled model, a time-varying parameter of the elastic modulus of concrete as a function of age is input to simulate the dynamic change of structural stiffness during construction.

[0016] In a preferred embodiment, in measure 1, the segmented pre-camber design curve is as follows: the long span adopts a quadratic parabolic distribution, the middle span adopts a linear transition curve, and the short span is adjusted by reducing the deformation of adjacent spans.

[0017] In a preferred embodiment, in measure 2, the layering sequence of concrete pouring is the bottom slab pouring stage, the web pouring stage, and the top slab pouring stage; the web pouring stage is divided into two stages: half pouring and full pouring.

[0018] In a preferred embodiment, in measure 2, during the bottom slab pouring stage, the pouring speed is controlled and the bottom formwork deflection is monitored after pouring is completed; during the web pouring stage, the mid-span deflection of the box girder is monitored during the half-pouring stage and the coordinated deformation of the web and bottom formwork is monitored during the full pouring stage; during the top slab pouring stage, the bottom formwork elevation is checked before pouring and the mid-span deflection is monitored in real time during pouring.

[0019] In a preferred embodiment, in measure 2, the deflection monitoring of the constructed box girder includes setting up monitoring points at mid-span, 1 / 4 span and support, and using a total station to collect the lateral displacement and elevation changes of the above monitoring points in real time, with data collection performed after each layer is poured.

[0020] In a preferred embodiment, in measure 3, if the elevation difference between the box girders on both sides of the connection area is greater than the limit after the casting is completed, it is corrected by grinding the top plate and / or adjusting the prestressed structure.

[0021] In a preferred embodiment, in measure 4, the preset threshold for deviation from deflection is a difference of more than 2 mm from the design deflection value; the preset threshold for deviation from stress is more than 70% of the allowable stress.

[0022] In a preferred embodiment, the method further includes measure 5: inter-span iterative correction. After the previous span of box girder is poured and reaches the design strength, the final alignment after the removal of the movable formwork is monitored, so as to use the recorded alignment deviation as the basis for adjusting the precamber of the next span of box girder.

[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0024] (1) Traditional methods often focus on setting a single pre-camber. This invention establishes a control strategy that runs through the entire construction process through four aspects: "pre-camber optimization, layered coordination, span constraints, and stress adaptation." This strategy not only accurately controls deformation but also incorporates structural stress safety into the real-time control scope, solving the engineering problems of uneven stress and cumulative alignment deviations in non-equal span construction. (2) This invention abandons the traditional approach of relying on empirical formulas and establishes a process of "simulation simulation - pre-stress correction - dynamic monitoring - span correction." Through high-fidelity simulation and mutual verification and iteration with measured data, the pre-camber can dynamically adapt to the complex time-varying effects during construction. This method significantly improves the accuracy of pre-camber setting and controls the alignment deviation of the completed bridge within a high standard. (3) Unlike the uniform pre-camber curve in traditional technologies, this invention innovatively designs matching curve forms for long spans, middle spans, and short spans, taking into account the large differences in stiffness of irregular span combinations. This “one span, one line” design ensures that the pre-camber is highly compatible with the actual deformation characteristics of each span, effectively suppresses the abrupt change in the line shape at the span connection, and ensures the smoothness of the entire bridge line. (4) For the first time, the time-varying characteristics of concrete, namely the growth of the elastic modulus, are coupled with the layered pouring load to realize the coordinated deformation control of the moving formwork and the box girder, which greatly reduces the risk of the entire bridge pouring deflection exceeding the limit. Attached Figure Description

[0025] Figure 1 This is a three-dimensional solid model diagram of the large-span non-equal-span cast-in-place box girder described in the embodiment of the present invention;

[0026] Figure 2 This is a finite element model diagram of the box girder in the coupling model described in this embodiment of the invention;

[0027] Figure 3 This is a finite element model diagram of the movable mold frame described in this embodiment of the invention;

[0028] Figure 4 This is a schematic diagram of the working conditions of the box girder during the bottom slab pouring stage in an embodiment of the present invention;

[0029] Figure 5 This is a schematic diagram of the working condition of the web of the box girder in the semi-casting stage according to an embodiment of the present invention;

[0030] Figure 6 This is a schematic diagram of the working conditions of the web of the box girder in the full casting stage according to an embodiment of the present invention;

[0031] Figure 7 This is a schematic diagram of the working conditions of the box girder during the top slab pouring stage in an embodiment of the present invention;

[0032] Figure 8 This is a schematic diagram of the load arrangement of the box girder during the preloading test in an embodiment of the present invention;

[0033] Figure 9 This is a construction flowchart of the box girder described in an embodiment of the present invention.

[0034] The markings in the diagram are: 1-box girder, 11-bottom plate, 12-web plate, 13-top plate, 2-moving formwork, 3-preload 3. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0036] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed", "equipped", "sleeved / connected", "connected", etc., should be interpreted broadly. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0038] like Figures 1-9 As shown in the figure, this invention provides a method for controlling the construction alignment of a large-span non-equal-span cast-in-place box girder, the method including the following measures:

[0039] Pre-construction preparation

[0040] Collect engineering design data, clarify non-equal span layout parameters such as span combination and box girder 1 section dimensions, time-varying curve of concrete elastic modulus, material performance parameters such as steel yield strength, and construction conditions such as the type of movable formwork 2 and pouring sequence.

[0041] Clean the contact areas of the movable formwork 2 brackets, bottom formwork, etc., remove loose rust and debris, check the rigidity of movable formwork 2, and control the main beam rigidity at 1 / 500 to ensure that the support system is not loose.

[0042] An elevation monitoring point is set up every 10 meters along the longitudinal direction of the bridge. Strain gauges are used to add stress monitoring points at the mid-span, quarter-span, support, and inter-span junctions to ensure that the monitoring covers the key stress areas.

[0043] Measure 1: Pre-camber optimization

[0044] The pre-camber optimization measures are based on a coupled model of the non-equal span box girder 1 and the moving formwork 2. First, the coupled model is established using finite element analysis software, with MIDAS software being the preferred choice. This coupled model employs a modeling strategy based on hybrid element partitioning. Specifically, tetrahedral elements are used in complex areas, including the junctions of the web 12 with the bottom plate 11 and the top plate 13, and the support anchorage zone, to accurately simulate stress concentration; hexahedral elements are used in regular areas, including the top plate 13 and the bottom plate 11, to improve computational efficiency. In the model, the box girder 1 is built according to the actual cross-sectional dimensions, while the moving formwork 2 includes key components such as the outer formwork, main beam, and corbels. The boundary conditions of the model are set according to the actual support conditions; the pier supports are treated as vertically fixed, longitudinally sliding, and laterally limited, while corresponding constraints are set at the span connections.

[0045] When simulating the coupled model, time-varying parameters of the concrete elastic modulus as a function of age are input to simulate the dynamic changes in structural stiffness during construction. The simulation process is based on a layered construction flow of "bottom slab pouring, web half-pouring, web full-pouring, and top slab pouring," applying corresponding loads in stages to calculate the theoretical deflection of box girder 1 with different spans at each construction stage.

[0046] To correct the model and obtain reliable pre-camber, a pre-loading test was conducted on at least one span of the box girder 1. Preferably, a pre-loading test with 100% design load was performed on the first span, using sandbags or water bags as the pre-loading load 3 in stages, and the measured deflection under each stage of pre-loading load 3 was measured. The measured deflection was compared with the aforementioned theoretical deflection, and based on the comparison results, the simulation parameters such as the support stiffness in the coupled model were inverted and corrected to ensure that the model's prediction accuracy met engineering requirements.

[0047] Finally, based on the structural stiffness differences of different spans, a segmented pre-camber design curve matching the span is selected. Specifically, for the different characteristics of the long span, middle span, and short span, the segmented pre-camber design curve is determined according to the following principles: the long span uses a quadratic parabola to distribute its pre-camber value; the middle span uses a linear transition curve; and the short span is adjusted by reducing the pre-camber value in conjunction with the deformation of adjacent spans. Through the above method, a pre-camber setting scheme that precisely matches the non-equidistant span combination is formed to offset the calculated maximum deflection. In a specific embodiment, the spans of the long span, middle span, and short span are 70m, 60m, and 50m, respectively, where the first span mentioned above is the long span.

[0048] Before concrete construction, the movable formwork 2 needs to be installed, and the reinforcing steel and prestressing materials need to be laid out. Specifically, the side formwork and bottom formwork are adjusted to the design position, and the supports and embedded parts are repositioned and remeasured. Then, ordinary reinforcing steel is tied and laid, and prestressing ducts are installed. After this step is completed, the concrete construction stage begins.

[0049] Measure 2: Deformation Coordination Control

[0050] Deformation control measures are implemented during concrete pouring. First, before pouring, based on the determined segmented pre-camber design curve, the elevation of the bottom formwork of the movable formwork 2 is adjusted to the design value using hydraulic jacks. Positioning accuracy must be strictly controlled to ensure that the error between the bottom formwork elevation and the design value is within allowable limits; specifically, the elevation error between adjacent points in the transverse direction is no more than 1 mm, and the longitudinal direction alignment smoothness error is no more than 2 mm.

[0051] Concrete pouring is carried out according to a predetermined, clearly defined layering sequence: the bottom slab pouring stage, the web pouring stage, and the top slab pouring stage. The web pouring stage is further divided into two phases: half-pouring and full-pouring. To control the difference in deformation between layers, the interval between each layer of pouring needs to be calculated and controlled within the range of matching concrete ages, ensuring that the successively poured concrete layers deform in tandem.

[0052] During each construction phase, the deflection of the constructed box girder 1 needs to be monitored. Monitoring is achieved by setting up monitoring points at key sections such as mid-span, 1 / 4 span, and supports, and using a total station to collect the lateral displacement and elevation changes of these monitoring points in real time. The monitoring frequency is once after each layer is poured. Simultaneously, the deflection of the movable formwork 2 itself is monitored. By comparing and analyzing the deformation data of box girder 1 and movable formwork 2, construction parameters are dynamically adjusted to ensure that the deformation of movable formwork 2 is coordinated with the deformation of box girder 1.

[0053] Specifically, for each pouring stage: During the base slab pouring stage, the concrete pouring speed is controlled to be no more than 0.5 meters per hour, and the deflection of the bottom formwork is monitored after pouring and kept within the calculated value. During the half-pouring period of the web pouring stage, the mid-span deflection of box girder 1 is monitored and kept within the warning value, while the deflection growth rate is controlled to be no more than 1.8 times that of the base slab pouring stage. During the full web pouring stage, the coordinated deformation of web 12 and the lower bottom formwork is monitored. During the top slab pouring stage, the bottom formwork elevation is checked before pouring, and the mid-span deflection is monitored in real time during pouring to ensure that the maximum deflection when the entire section is poured does not exceed the specification limit.

[0054] Measure 3: Inter-border constraint control

[0055] The span constraint control measures target the connection area between two adjacent box girders 1 with unequal spans. During construction, a rigid connection structure is set in this connection area, specifically achieved by configuring longitudinal continuous reinforcement and dense stirrups. This structure aims to constrain the relative displacement in the vertical and transverse non-longitudinal directions of this area, thereby effectively suppressing abrupt changes in the linearity of the precamber curves of different spans at the connection point.

[0056] After the box girders 1 on both sides of the connection area are poured, the prestressing tendons in the transverse and longitudinal directions are tensioned and grouted. Then, after removing the movable formwork 2, the elevation difference between the two box girders 1 is checked and measured. If the check finds that the elevation difference is greater than the set limit, which is usually 1 mm, a correction procedure needs to be initiated. The correction method includes locally grinding the top slab 13 and / or adjusting the prestressing structure to ensure a smooth alignment at the connection. Adjusting the prestressing structure specifically involves fine-tuning the tension of the prestressing tendons.

[0057] Measure 4: Stress adaptation control:

[0058] Stress adaptation control measures are implemented throughout the entire construction process. During construction, the deflection and stress in known structural stress concentration areas, such as the connection between the corbel and the main beam, and the junction of the web 12 and the bottom plate 11, are monitored in real time.

[0059] Specific preset thresholds are set for the monitoring data. Specifically, the preset threshold for deflection deviation is when the monitored deflection differs from the design value by more than 2 mm; the preset threshold for stress deviation is when the monitored stress exceeds 70% of the material's allowable stress. When the real-time monitoring data deviates from either of these thresholds, the system triggers the construction adjustment mechanism.

[0060] The construction adjustment mechanism includes one or more of the following measures: adjusting the elevation of the movable formwork 2, i.e., fine-tuning the elevation of the bottom formwork by operating jacks; adjusting the pouring rhythm, including changing the pouring sequence or adjusting the pouring speed; and adding local reinforcement structures, such as temporarily welding stiffening plates in areas of abnormal stress. By implementing these measures, the stress and alignment of the structure are controlled, allowing it to readjust to the design expectations.

[0061] V. Cross-border Iterative Correction

[0062] Inter-span iterative correction measures are implemented between spans in continuous construction. After the previous span of box girder 1 is poured and reaches its design strength, the moving formwork 2 is moved according to the process of "open-lower-through-close". After the movement is completed, the final alignment of the previous span of box girder 1 is monitored in detail, and all deviation data between it and the design alignment are recorded. These recorded alignment deviations will serve as the direct basis for adjusting the pre-camber of the next span of box girder 1. After the moving formwork 2 is moved to the next span and positioned, the pre-camber design curve of the next span is optimized and adjusted based on the feedback data of the previous span, thereby achieving iterative improvement in alignment control accuracy.

[0063] In summary, the method provided by the embodiments of the present invention has the following technical advantages: (1) Traditional methods focus on a single pre-camber setting. The present invention establishes a control strategy that runs through the entire construction process through four aspects: "pre-camber optimization, layered coordination, span constraint, and stress adaptation". This strategy not only accurately controls deformation, but also incorporates structural stress safety into the scope of real-time control, solving the engineering problems of uneven stress and cumulative alignment deviation in non-equal span construction. (2) The present invention abandons the traditional approach of relying on empirical formulas and establishes a process of "simulation simulation - pre-stress correction - dynamic monitoring - span correction". Through high-fidelity simulation and mutual verification and iteration with measured data, the pre-camber can dynamically adapt to the complex time-varying effects in construction. This method greatly improves the accuracy of pre-camber setting and controls the alignment deviation of the completed bridge within a high standard. (3) Unlike the unified pre-camber curve in traditional technology, the present invention innovatively designs matching curve forms for long spans, middle spans, and short spans, respectively, to address the characteristics of large differences in stiffness of irregular span combinations. This “one span, one line” design ensures that the pre-camber is highly compatible with the actual deformation characteristics of each span, effectively suppresses the abrupt change in the line shape at the span connection, and ensures the smoothness of the entire bridge line. (4) For the first time, the time-varying characteristics of concrete, namely the growth of the elastic modulus, are coupled with the layered pouring load to achieve coordinated deformation control of the moving formwork 2 and the box girder 1, which greatly reduces the risk of the entire bridge pouring deflection exceeding the limit.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the patent scope of the present invention. Any technically equivalent modifications made based on the content of this specification shall fall within the protection scope of the present invention.

Claims

1. A method for controlling the construction alignment of a large-span, non-equal-span cast-in-place box girder, characterized in that: Including the following measures: Measure 1: Pre-camber optimization Based on the coupled model of non-equal span box girder and moving formwork, the theoretical deflection of box girders with different spans during the layered casting construction process is simulated and calculated; a pre-stressing test is carried out on at least one span of box girder, and the simulation parameters of the coupled model are corrected based on the comparison results of measured deflection and theoretical deflection; according to the structural stiffness difference of different spans, a segmented pre-camber design curve matching the span is selected. Measure 2: Deformation Coordination Control Concrete is poured in the predetermined layer sequence, and during the pouring process, the following measures are taken: the elevation of the bottom formwork is positioned within the design value; the interval between layer pours is controlled within the range of concrete age to control the difference in deformation between layers. Monitor the deflection of the box girders that have been constructed in each construction stage; simultaneously monitor the deflection of the moving formwork and adjust the construction parameters to coordinate the deformation of the moving formwork with that of the box girder. Measure 3: Inter-border constraint control In the connection area between two adjacent box girders with different spans, a rigid connection structure is set to constrain the relative displacement of the area in the non-longitudinal direction of the bridge, and to suppress the linear abrupt change of the precamber curve of different spans at the connection point; after the casting is completed, the elevation difference between the box girders on both sides of the connection area is checked. Measure 4: Stress Adaptation Control Throughout the construction process, the deflection and stress in the stress concentration areas of the structure are monitored in real time. When the monitoring data deviates from the preset threshold, the stress and alignment are controlled to match the design value through a construction adjustment mechanism. The construction adjustment mechanism includes one or more of the following measures: adjusting the elevation of the movable formwork; adjusting the pouring rhythm; and adding local reinforcement structures.

2. The construction alignment control method for a large-span non-equal-span cast-in-place box girder according to claim 1, characterized in that: In measure 1, the coupling model adopts a finite element analysis model based on hybrid element partitioning, including tetrahedral elements in complex areas such as the junction of the web and bottom plate, top plate, and support anchorage area, and hexahedral elements in regular areas such as the top plate and bottom plate.

3. The construction alignment control method for a large-span non-equal-span cast-in-place box girder according to claim 1, characterized in that: In measure 1, when simulating the coupled model, time-varying parameters of the elastic modulus of concrete as a function of age are input to simulate the dynamic changes in structural stiffness during construction.

4. The construction alignment control method for a large-span non-equal-span cast-in-place box girder according to claim 1, characterized in that: In measure 1, the segmented pre-camber design curve is as follows: the long span adopts a quadratic parabolic distribution, the middle span adopts a linear transition curve, and the short span is adjusted by reducing the deformation of adjacent spans.

5. The construction alignment control method for a large-span non-equal-span cast-in-place box girder according to claim 1, characterized in that: In measure 2, the layering sequence of concrete pouring is the bottom slab pouring stage, the web pouring stage, and the top slab pouring stage; the web pouring stage is divided into two stages: half pouring and full pouring.

6. The construction alignment control method for a large-span non-equal-span cast-in-place box girder according to claim 5, characterized in that: In Measure 2, during the bottom slab pouring stage, the pouring speed is controlled and the bottom formwork deflection is monitored after pouring is completed; during the web pouring stage, the mid-span deflection of the box girder is monitored during the half-pouring stage and the coordinated deformation of the web and bottom formwork is monitored during the full pouring stage; during the top slab pouring stage, the bottom formwork elevation is checked before pouring and the mid-span deflection is monitored in real time during the pouring process.

7. The construction alignment control method for a large-span non-equal-span cast-in-place box girder according to claim 1, characterized in that: In Measure 2, the deflection monitoring of the constructed box girder includes setting up monitoring points at mid-span, 1 / 4 span, and supports, and using a total station to collect the lateral displacement and elevation changes of the above monitoring points in real time, with data collection performed after each layer is poured.

8. The construction alignment control method for a large-span non-equal-span cast-in-place box girder according to claim 1, characterized in that: In measure 3, if the elevation difference between the box girders on both sides of the connection area is greater than the limit after the pouring is completed, it will be corrected by grinding the top plate and / or adjusting the prestressed structure.

9. The construction alignment control method for a large-span non-equal-span cast-in-place box girder according to claim 1, characterized in that: In measure 4, the preset threshold for deviation from deflection is a difference of more than 2 mm from the design deflection value; the preset threshold for deviation from stress is more than 70% of the allowable stress.

10. The construction alignment control method for a large-span non-equal-span cast-in-place box girder according to claim 1, characterized in that: It also includes measure 5: inter-span iterative correction. After the previous span of box girder is completed and reaches the design strength, the final alignment after the removal of the moving formwork is monitored, and the recorded alignment deviation is used as the basis for adjusting the precamber of the next span of box girder.

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