State monitoring system used in pouring period of main beam section of large-span bridge

Abstract

The invention discloses a state monitoring system for a main beam section of a large-span bridge during pouring, and relates to the technical field of bridge construction. Comprising a data acquisition module, a data processing module, a judgment module and a terminal module, the data acquisition module is used for acquiring bridge structure parameters, the data processing module is used for constructing a finite element model and obtaining key nodes, and the judgment module is used for judging whether predicted node values and actually measured node values of the finite element model exceed threshold values or not. The method is used for obtaining judgment results and generating corresponding reports. Finite element analysis of a bridge structure can be perfected, the automatic process of bridge monitoring is achieved, manpower resource waste is reduced, and the method is more universal.

Description

Technical Field

[0001] The invention relates to the technical field of bridge construction, and in particular to a state monitoring system during casting of main beam segments of a large-span bridge. Background Art

[0002] With the rapid development of science and economy, the scale and progress of bridge construction have also developed rapidly. Prestressed concrete continuous bridges have the characteristics of large structural rigidity, small deformation, smooth road driving, small amount of later maintenance, good structural stress performance, beautiful appearance, strong earthquake resistance, etc., and are widely used in highway, railway, municipal and other industries.

[0003] Due to social development and demand, the span of prestressed concrete continuous bridges continues to increase, which puts higher requirements on the design and construction of bridges. In order to meet the demand for large spans of prestressed concrete continuous beam bridges and not affect the normal traffic under the bridge, cantilever casting is often used for construction. Controlling the deflection and stress of each segment during the construction process to ensure the perfect docking of the bridge, and ensuring that the line shape and stress of the bridge meet the design requirements after completion are the key difficulties in the control of the construction process. The closing of the prestressed concrete continuous beam bridge will form a transformation of the structural mechanics system, causing changes in the line shape of the bridge and changes in the stress of the structural section. When the stress is too large, it will cause damage such as cracking of the beam body. As the span of the bridge continues to increase, ensuring the smooth closing of the bridge faces new challenges. To ensure the smooth closing of the bridge, it is necessary to ensure that during the cantilever casting construction process, the elevation difference of the beam sections on both sides of the closing section cannot be too large, and the axis cannot have a large offset. During the cantilever casting construction process, due to the influence of factors such as material properties, construction errors, and ambient temperature, the theoretical values ​​of the structural parameters will vary greatly compared to the actual values, which will seriously affect the linear shape and stress of the structure during the bridge construction process as well as the closing accuracy, resulting in excessive deflection of the main beam. The above problems will not only prevent the bridge from closing smoothly, but also affect the linear shape and comfort of the bridge.

[0004] Therefore, it is an urgent problem for technical personnel in this field to propose a status monitoring system for the casting of main beam segments of large-span bridges to solve the problem that the existing technology cannot detect bridge errors in time and continuous bridges cannot be perfectly connected. Summary of the invention

[0005] In view of this, the present invention provides a status monitoring system for the casting of main beam segments of a long-span bridge, which can achieve the effect of timely monitoring errors.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A state monitoring system for main beam segment casting of a long-span bridge, comprising a data acquisition module, a data processing module, a judgment module and a terminal module:

[0008] Data acquisition module, used to collect bridge structure parameters;

[0009] A data processing module is connected to the first output terminal of the data acquisition module and is used to construct a finite element model and obtain key nodes;

[0010] A judgment module, connected to the second output terminal of the data acquisition module and the output terminal of the data processing module respectively, for judging whether the node value predicted by the finite element model and the node value actually measured exceed a threshold value;

[0011] The terminal module is connected to the output end of the judgment module and is used to obtain the judgment result and generate a corresponding report.

[0012] In the above system, optionally, the data acquisition module collects data by means of an internal pre-buried sensor group, and the sensor group includes but is not limited to a vibrating-wire strain gauge, a resistance strain gauge, and a grating optical fiber sensor.

[0013] In the above system, optionally, in the data processing module, the finite element model construction includes the following contents:

[0014] Establish a finite element model of the bridge structure of the main beam segment according to the bridge structure parameters, divide the grid and assign units;

[0015] Establish a finite element model of the unit, determine the properties of the unit, decompose the unit into several sub-units, and set different nodes in the sub-units;

[0016] In the sub-unit, a single-direction force is applied to the node of the unit, and fixed constraints are applied to the other directions of the node to form constraint conditions;

[0017] Analyze the unit under constraints and complete the unit construction.

[0018] In the above system, optionally, the unit structure in the finite element model includes but is not limited to concrete shrinkage creep and pre-camber.

[0019] In the above system, optionally, the measured node values ​​in the judgment module include but are not limited to displacement and camber.

[0020] For the above system, optionally, the periods for measuring the actual node values ​​include after moving the hanging basket, before steel bar tying, after steel bar tying, after pouring concrete, before prestressing, and after prestressing.

[0021] It can be seen from the above technical solution that, compared with the prior art, the present invention provides a status monitoring system for the casting of main beam segments of large-span bridges, which has the following beneficial effects: 1) The present invention sets a judgment module to perform real-time analysis and evaluation of the information of the construction bridge, eliminate unreasonable data and provide feedback on abnormal values; 2) The present invention performs coupling analysis on multiple influencing factors in the construction process, and more accurately reflects the coupling analysis results of the cantilever casting construction control factors to the structure, thereby achieving accurate finite element analysis of the structure; 3) Automated monitoring and adjustment are used to achieve better control of the entire construction process and reduce the waste of human resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0023] Figure 1 The present invention discloses a flow chart of a system for monitoring the state of a main beam segment during casting of a long-span bridge. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In this application, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, the elements defined by the sentence "comprise one..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0026] Reference Figure 1As shown, the present invention discloses a state monitoring system for main beam segment casting of a long-span bridge, including a data acquisition module, a data processing module, a judgment module and a terminal module:

[0027] Data acquisition module, used to collect bridge structure parameters;

[0028] A data processing module is connected to the first output terminal of the data acquisition module and is used to construct a finite element model and obtain key nodes;

[0029] A judgment module, connected to the second output terminal of the data acquisition module and the output terminal of the data processing module respectively, for judging whether the node value predicted by the finite element model and the node value actually measured exceed a threshold value;

[0030] The terminal module is connected to the output end of the judgment module and is used to obtain the judgment result and generate a corresponding report.

[0031] Furthermore, the data acquisition module collects data by means of an internally embedded sensor group, and the sensor group includes but is not limited to a vibrating-wire strain gauge, a resistance strain gauge, and a grating optical fiber sensor.

[0032] Furthermore, in the data processing module, the finite element model construction includes the following contents:

[0033] Establish a finite element model of the bridge structure of the main beam segment according to the bridge structure parameters, divide the grid and assign units;

[0034] Establish a finite element model of the unit, determine the properties of the unit, decompose the unit into several sub-units, and set different nodes in the sub-units;

[0035] In the sub-unit, a single-direction force is applied to the node of the unit, and fixed constraints are applied to the other directions of the node to form constraint conditions;

[0036] Analyze the unit under constraints and complete the unit construction.

[0037] Furthermore, the unit structure in the finite element model includes but is not limited to concrete shrinkage creep and pre-camber.

[0038] Specifically, concrete shrinkage creep includes: during cantilever casting construction, the shrinkage creep of concrete starts to grow rapidly and then gradually slows down, and tends to be stable after long-term action, which has a great influence on the deformation of components. The basic stress-strain equation of concrete shrinkage creep under constant stress σ is:

[0039] During the cantilever construction process, the stress on the cross section of the bridge structure changes continuously. Under the action of variable stress, according to the linear creep theory and the superposition principle, a digital model of concrete shrinkage creep is obtained. The basic stress-strain equation of shrinkage creep is expressed as:

[0040]

[0041] in, is the creep coefficient of concrete (t0 and ti are loading age and calculation age respectively), E(t0) is the elastic modulus of concrete at age t0, ε sh (t,t0) is the strain caused by concrete shrinkage, Δσ(t i ) is t i Stress increment at each moment.

[0042] Pre-camber includes: Usually the sum of these influence values ​​can be taken as the maximum value of the mid-span pre-camber, with the two pier supports as the zero point, and the remaining points can be approximately distributed according to a quadratic parabola.

[0043] During the hanging basket suspended pouring construction process, the elastic deformation of the hanging basket is a factor that must be considered in the pre-camber setting. Its specific size is mainly related to factors such as the weight of the poured beam section and the tightness of the hanging basket sling. The expression is:

[0044]

[0045] Then a digital model of the pre-camber is obtained, and then a finite element model is synthesized for unified discussion.

[0046] Furthermore, the measured node values ​​in the judgment module include but are not limited to displacement and camber.

[0047] Specifically, the displacement includes: setting up monitoring points, reference points and working points, setting up a total station at the working point to observe the reference points and monitoring points, setting up the total station at the working point to observe and obtain the initial coordinates of the monitoring point △ 初始值 , in the actual measurement, observe the coordinates △i of all monitoring points in the i-th monitoring 正 and △i 倒 , and the total displacement and settlement displacement values ​​are calculated by the following formula:

[0048] △i 总 =(△i 正 +△i 倒 ) / 2-△ 初始值 , △i 值 =△i 总 -△(i-1) 总 ;

[0049] Wherein, i represents the i-th monitoring.

[0050] During the cantilever casting of each beam section, due to some unforeseen factors such as the different tightness of the hanging basket straps, the actual elastic deformation of the hanging basket often deviates from the result obtained by preloading. This requires monitoring the actual elastic deformation of the hanging basket during the casting process and comparing it with the preloading result, so as to correctly predict the elastic deformation of the next beam section.

[0051] In the invention, the expression for calculating the actual deformation value of the hanging basket is:

[0052]

[0053] Where: f f is the elastic deformation value of the hanging basket when pouring the nth block, Δf n , Δf n-1 , Δf n-2 is the displacement of the front end of the nth, n-1th, and n-2th beam segments after pouring the nth concrete block, l n , l n-1 is the length of the nth and n-1th beam sections.

[0054] In addition, Δf n is the displacement of the front end of the concrete bottom formwork, which is the difference between the positioning elevation of the hanging basket in this section and the elevation after pouring concrete. It includes the rigid body displacement caused by the positioning of the constructed section and the elastic deformation of the hanging basket. n-1 = l n When , we can get: f f =Δf n -(2Δf n-1 -Δf n-2 ). Then the deformation of the hanging basket of the constructed section can be inferred, and the deformation law of the hanging basket can be inferred by referring to the load test results after the hanging basket is assembled, and then the elastic deformation of the hanging basket of the next section can be predicted more accurately.

[0055] Furthermore, the periods of numerical measurement of measured nodes include after moving the hanging basket, before steel bar tying, after steel bar tying, after pouring concrete, before prestressing, and after prestressing.

[0056] Furthermore, the measurement period also includes the selection of the measurement time.

[0057] Specifically, the beam body is in a uniform temperature state and is measured in time with each process. Temperature measurement must be carried out while observing the elevation. A measurement must be carried out after all the work of each section is completed, and the time and temperature must be noted. According to the analysis of previous temperature parameters, temperature changes are closely related to structural deflection. In order to minimize the impact of temperature on the measurement work, elevation measurement should be carried out in the early morning when the temperature change range is the smallest. At the same time, to ensure the accuracy of monitoring, re-measurements should be carried out every night when the temperature change is small, and then the results obtained should be compared with the results in the early morning. As the cantilever casting construction proceeds, the structural deformation increases. After each measurement of the current section, the adjacent sections must also be measured to ensure that the construction accuracy meets the requirements.

[0058] Furthermore, the judgment module eliminates larger errors by using the format of mean difference standard deviation.

[0059] Specifically, the judgment module includes but is not limited to comparing whether the influence of concrete shrinkage creep stress exceeds a threshold, whether the pre-camber is consistent with the measured camber, and whether the displacement during the construction stage is consistent.

[0060] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can refer to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment. The system and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without creative work.

[0061] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A condition monitoring system for main beam segment casting of a long-span bridge, characterized in that: Including data acquisition module, data processing module, judgment module and terminal module: Data acquisition module, used to collect bridge structure parameters; A data processing module is connected to the first output terminal of the data acquisition module and is used to construct a finite element model and obtain key nodes; A judgment module, connected to the second output terminal of the data acquisition module and the output terminal of the data processing module respectively, for judging whether the node value predicted by the finite element model and the node value actually measured exceed a threshold value; The terminal module is connected to the output end of the judgment module and is used to obtain the judgment result and generate a corresponding report.

2. A condition monitoring system for main beam segment casting of a long-span bridge according to claim 1, characterized in that: The data acquisition module collects data by means of an internally embedded sensor group, which includes but is not limited to a vibrating-wire strain gauge, a resistance strain gauge, and a grating optical fiber sensor.

3. A condition monitoring system for main beam segment casting of a long-span bridge according to claim 1, characterized in that: In the data processing module, the finite element model construction includes the following: Establish a finite element model of the bridge structure of the main beam segment according to the bridge structure parameters, divide the grid and assign units; Establish a finite element model of the unit, determine the properties of the unit, decompose the unit into several sub-units, and set different nodes in the sub-units; In the sub-unit, a single-direction force is applied to the node of the unit, and fixed constraints are applied to the other directions of the node to form constraint conditions; Analyze the unit under constraints and complete the unit construction.

4. A condition monitoring system for main beam segment casting of a long-span bridge according to claim 3, characterized in that: The unit structure in the finite element model includes but is not limited to concrete shrinkage creep and pre-camber.

5. The system for monitoring the state of a main beam segment during casting of a long-span bridge according to claim 1, characterized in that: The measured node values ​​in the judgment module include but are not limited to displacement and camber.

6. A condition monitoring system for main beam segment casting of a long-span bridge according to claim 5, characterized in that: The periods for measuring the numerical values ​​of the measured nodes include after moving the hanging basket, before steel bar tying, after steel bar tying, after pouring concrete, before prestressing, and after prestressing.

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