A method for assessing the stress reserve state of precast beams

Abstract

This invention belongs to the field of precast beam monitoring technology, and particularly relates to a precast beam full life cycle stress monitoring system and method. The system involves deploying stress monitoring sensors inside and outside pre-set stress monitoring points on the precast beam; obtaining the theoretical linear structure of the precast beam through a precast beam stress theoretical change generation module, constructing a finite element model for simulation analysis to generate the theoretical stress change; collecting the linear structure of the precast beam before and after tensioning, as well as the stress values ​​at the stress monitoring points before and after tensioning, through a precast beam actual stress change generation module, constructing a three-dimensional model to analyze the stress change state of the precast beam, and generating the actual stress change; and comparing the theoretical stress change with the actual stress change through a precast beam stress reserve state assessment module to evaluate the stress reserve state of the precast beam. This invention solves the problem of low reliability in existing precast beam full life cycle stress monitoring implementation schemes.

Description

[0001] This application is a divisional application of Chinese patent application 202211201859.X, filed on September 29, 2022, entitled "A precast beam full life cycle stress monitoring system and method". Technical Field

[0002] This invention belongs to the field of precast beam monitoring technology, and in particular relates to a precast beam full life cycle stress monitoring system and method. Background Technology

[0003] Precast beams are beams that are prefabricated in a factory and then transported to the construction site for installation and fixation according to the design requirements. Precast beam technology is being used more and more widely in the field of civil engineering, mainly in highway bridge construction. In the construction plan of precast beams, there are strict implementation measures for the inspection of prestressed materials, the construction of steel strands, and prestressing tensioning. Stress monitoring and prestressing tension control are important parts to ensure the structural health of precast beams.

[0004] After prestressing is applied to a precast beam, its prestress reserve and uniformity will affect the structural safety of the precast beam under later loads. Therefore, in order to enhance the control of prestressing tension and realize the monitoring of stress throughout its entire life cycle, the current implementation plan mainly uses the strain gauge method to conduct experimental research on the effective prestress of the precast beam. By attaching strain gauges to the prestressing tendons of the precast beam, the change in resistance of the strain gauges is used to reflect the stress change relationship of the prestressing tendons. The problem with this approach is that the strain gauges are prone to damage during the tensioning process, and there is a problem that all strain gauges on some sections are completely damaged, resulting in low reliability. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a precast beam full life cycle stress monitoring system and method to solve the problem of low reliability in existing precast beam full life cycle stress monitoring implementation schemes.

[0006] The basic solution provided by this invention is: a precast beam full life cycle stress monitoring system, comprising several stress monitoring sensors, a precast beam theoretical stress change generation module, a precast beam actual stress change generation module, and wherein:

[0007] The stress monitoring sensors are respectively deployed inside and outside the pre-set stress monitoring points of the precast beam;

[0008] The precast beam stress theoretical change generation module is used to obtain the theoretical linear structure of the precast beam, construct a finite element model to simulate and analyze the stress change state of the precast beam, and generate the precast beam stress theoretical change.

[0009] The precast beam stress actual change generation module is used to collect the linear structure of the precast beam before tensioning, the linear structure after tensioning, and the stress values ​​of stress monitoring points before and after tensioning, construct a three-dimensional model to analyze the stress change state of the precast beam, and generate the actual change of precast beam stress.

[0010] The precast beam stress reserve state assessment module is used to compare the theoretical change in precast beam stress with the actual change in precast beam stress to assess the stress reserve state of the precast beam.

[0011] The principle and advantages of this invention are as follows: Currently, the prestress control of precast beams mainly relies on the elongation of steel strands and tension to indirectly control the prestress reserve of the beam. However, due to factors such as anchor retraction and pipe friction, there is an uncontrollable loss of prestress. The existing method of attaching strain gauges to the prestressing tendons of precast beams and using the resistance change of the strain gauges to reflect the stress change relationship of the prestressing tendons has the problem of low reliability.

[0012] To this end, this application pre-sets stress monitoring points during the casting stage of the precast beam, embedding stress sensors inside the monitoring points and attaching stress sensors to the external surfaces to achieve full life-cycle stress monitoring of the precast beam. Simultaneously, when an internally embedded stress sensor fails, the externally attached stress sensor monitors the stress changes in the precast beam, ensuring that at least one stress sensor at each monitoring point is functioning normally. Subsequently, the theoretical linear structure of the precast beam is obtained through a precast beam stress theoretical change generation module. A finite element model is used to simulate the stress change state of the precast beam, generating the theoretical stress change of the precast beam. Then, the actual stress change generation module collects the linear structure of the precast beam before tensioning, the linear structure after tensioning, and the stress values ​​at the monitoring points before and after tensioning. A three-dimensional model is used to analyze the stress change state of the precast beam, thereby obtaining the stress deformation amount of the precast beam before and after tensioning control. Finally, the precast beam stress reserve state assessment module compares the theoretical stress deformation amount of the precast beam with the actual stress deformation amount, obtaining a highly reliable precast beam stress reserve assessment result.

[0013] Therefore, the advantage of this application is that by pre-embedding sensors inside and attaching sensors to the same stress monitoring point of the precast beam during the casting stage, it is possible to achieve full life cycle stress monitoring of the precast beam and synchronous monitoring by internal and external sensors to obtain more accurate stress values. At the same time, even if the internally embedded sensor is damaged, monitoring can still be carried out through the externally attached sensor, avoiding the situation where the sensor cannot obtain the stress value of the stress monitoring point due to the tensioning of the precast beam, thus improving the reliability of the precast beam in the full life cycle stress monitoring process.

[0014] Furthermore, the stress monitoring sensors are respectively deployed inside and outside the pre-set stress monitoring points on the precast beam, specifically as follows:

[0015] Pre-store historical construction data and obtain the displacement change value of the precast beam at the stress monitoring point in the historical construction data of the precast beam;

[0016] The vulnerability is assessed based on the displacement change value, and compared with the preset vulnerability threshold to generate vulnerable points and several cooperating points.

[0017] Pre-embed stress sensors inside vulnerable locations and attach stress sensors to the surface at cooperating locations.

[0018] Beneficial Effects: Precast beam construction technology has been used for a long time, so construction workers usually store a lot of historical data on precast beam construction. In this historical data, stress monitoring points in the precast beam will cause displacement of the beam body during the tensioning process, generating displacement change values. The magnitude of displacement change values ​​varies at different stress monitoring points in the precast beam. Therefore, the vulnerability of the displacement change value is assessed and compared with the vulnerability threshold preset by the construction personnel. Points exceeding the preset vulnerability threshold are designated as vulnerable points. Multiple cooperating points are set near the vulnerable points at locations below the preset vulnerability threshold. The greater the vulnerability, the greater the displacement change value, and the greater the possibility of stress sensor failure at that point. Therefore, to avoid the stress sensor at the vulnerable point becoming unusable after failure, stress sensors are surface-mounted at the cooperating points as backup monitoring for the vulnerable point. This ensures that even if the stress sensor at the vulnerable point fails, monitoring can still be carried out through the stress sensors surface-mounted at the cooperating points.

[0019] Furthermore, the precast beam stress theoretical change generation module includes a precast beam linear structure acquisition unit, a theoretical stress value generation unit, a simulation unit, and a precast beam deformation calculation unit, wherein:

[0020] The precast beam linear structure acquisition unit is used to acquire the linear structure of the precast beam placed on the pedestal and to construct a finite element model of the precast beam.

[0021] The theoretical stress value generation unit is used to generate the theoretical stress value of the precast beam stress monitoring point;

[0022] The simulation unit is used to simulate the prestressing tensioning conditions at the actual construction site, and to simulate the stress value changes at the stress monitoring points of the precast beam finite element model and the linear structural changes of the precast beam as the stress value changes.

[0023] The precast beam deformation calculation unit is used to extract the displacement position of the precast beam before and after tensioning according to the preset deformation value extraction position of the precast beam finite element model, calculate the theoretical deformation of the precast beam, and draw the theoretical deformation curve of the precast beam based on the theoretical deformation of the precast beam and draw the theoretical stress change curve based on the simulation results of the stress value change at the stress monitoring point of the precast beam.

[0024] Beneficial effects: The linear structure of the precast beam placed on the platform is obtained by the linear structure acquisition unit of the precast beam. Since the platform does not deform during the tensioning control of the precast beam, it can be used as a reference plane before and after the tensioning of the precast beam, which is convenient for simulation. During the simulation, the theoretical stress change state and deformation of the precast beam under tension control can be obtained, thereby generating curves for more intuitive display and comparison.

[0025] Furthermore, the module for generating the actual stress variation of the precast beam includes a data acquisition unit, a data preprocessing unit, a data registration unit, and a data calculation unit, wherein:

[0026] The data acquisition unit is used to acquire point cloud data of several stations before and after the precast beam tensioning by scanning with a 3D scanner and to acquire the actual stress value change of the precast beam stress monitoring points.

[0027] The data preprocessing unit is used to preprocess the acquired point cloud data and generate preprocessing results;

[0028] The data registration unit is used to construct a precast beam point cloud model 1 before prestressing tension and a precast beam point cloud model 2 after prestressing tension after preprocessing, and to register the precast beam point cloud model 1 and the precast beam point cloud model 2 to generate a precast beam registration model.

[0029] The data calculation unit obtains the deformation values ​​of the precast beam before and after tensioning according to the preset extraction positions and methods of the deformation values ​​of the precast beam registration model, calculates the actual deformation of the precast beam, and plots the actual deformation curve of the precast beam based on the actual deformation of the precast beam and the actual stress change curve based on the actual stress value changes monitored at the stress monitoring points of the precast beam.

[0030] Beneficial effects: Obtaining point cloud data facilitates the subsequent point cloud registration process. Preprocessing can remove useless points and make the model data more accurate, avoiding interference. After registration, the preprocessed model can accurately obtain the actual deformation of the precast beam and display it through a curve graph, allowing construction workers to intuitively understand the deformation and stress change of the precast beam.

[0031] Furthermore, the precast beam stress reserve state assessment module includes a precast beam deformation curve comparison unit, a local prestress reserve assessment unit, an overall prestress reserve assessment unit, and a stress value comparison unit, wherein:

[0032] The precast beam deformation curve comparison unit is used to compare the theoretical deformation curve with the actual deformation curve and generate a comparison curve.

[0033] The local prestress reserve assessment unit is used to calculate the location of vulnerable points in the comparison curve to obtain the local prestress reserve assessment result;

[0034] The overall prestress reserve assessment unit is used to calculate the area enclosed by the theoretical deformation curve and the coordinate axis and to calculate the area enclosed by the actual deformation curve and the coordinate axis, and to compare the areas to generate the overall prestress reserve assessment result.

[0035] The stress value comparison unit is used to compare the theoretical stress variation curve of the precast beam with the actual stress variation curve of the precast beam in the same way as the local prestress reserve assessment unit and the overall prestress reserve assessment unit, to generate local stress value comparison results and overall stress value comparison results, and to verify the generated local stress value comparison results and overall stress value comparison results with the local prestress reserve assessment results and overall prestress reserve assessment results.

[0036] Beneficial effects: By comparing the theoretical and actual variation curves, the prestress reserve state of the precast beam can be reflected. Through local and overall analysis, the prestress assessment of the precast beam is more comprehensive and the data is more accurate. At the same time, by verifying the stress value change state, the consistency of the prestress assessment can be reflected.

[0037] A method for monitoring stress throughout the entire life cycle of precast beams, comprising:

[0038] S1: Several stress monitoring points are pre-set during the casting of precast beams. Stress sensors are pre-embedded inside the stress monitoring points of the precast beams and external surface-mounted stress sensors are used to construct a full life cycle stress monitoring system.

[0039] S2: Obtain the theoretical linear structure of the precast beam, construct a finite element model to simulate and analyze the stress change state of the precast beam, and generate the theoretical stress change of the precast beam;

[0040] S3: Collect the linear structure of the precast beam before tensioning, the linear structure after tensioning, and the stress values ​​of stress monitoring points before and after tensioning. Construct a three-dimensional model to analyze the stress change state of the precast beam and generate the actual stress change of the precast beam.

[0041] S4: Compare the theoretical change in precast beam stress with the actual change in precast beam stress to assess the stress reserve status of the precast beam.

[0042] Furthermore, S1 includes:

[0043] S1-1: Preset historical construction data of precast beams and obtain the displacement change value of the precast beam at the stress monitoring point in the historical construction data of precast beams;

[0044] S1-2: Evaluate the vulnerability based on the displacement change value, and compare it with the preset vulnerability threshold to generate vulnerable points and several cooperating points;

[0045] S1-3: Pre-embed stress sensors inside vulnerable points and attach stress sensors to the surface at cooperating points.

[0046] Furthermore, S2 includes:

[0047] S2-1: Obtain the linear structure of the precast beam placed on the pedestal and construct the finite element model of the precast beam;

[0048] S2-2: Generate the theoretical stress values ​​at the stress monitoring points of the precast beam;

[0049] S2-3: Simulate the prestressing tensioning conditions at the actual construction site, simulate the stress value changes at the stress monitoring points of the precast beam finite element model, and simulate the linear structural changes of the precast beam as the stress value changes.

[0050] S2-4: Extract the displacement position of the precast beam before and after tensioning according to the preset deformation value extraction position of the precast beam finite element model, and calculate the theoretical deformation of the precast beam.

[0051] S2-5: Plot the theoretical deformation curve of the precast beam based on the theoretical deformation amount of the precast beam, and plot the theoretical stress variation curve based on the simulation results of the stress value changes at the stress monitoring points of the precast beam.

[0052] Furthermore, S3 includes:

[0053] S3-1: Use a 3D scanner to scan and obtain point cloud data of several stations before and after prestressing of the precast beam. After data preprocessing, construct point cloud model 1 of the precast beam before prestressing and point cloud model 2 of the precast beam after prestressing. Register the point cloud model 1 and the point cloud model 2 of the precast beam to generate a precast beam registration model.

[0054] S3-2: Obtain the actual stress value change and coordinate points of the stress monitoring points on the precast beam, and register the coordinate points with the precast beam point cloud model one and the precast beam point cloud model two;

[0055] S3-3: Obtain the deformation values ​​of the precast beam before and after tensioning according to the preset deformation value extraction position and method of the precast beam registration model, and calculate the actual deformation of the precast beam;

[0056] S3-4: Draw the actual deformation curve of the precast beam based on the actual deformation amount of the precast beam, and draw the actual stress change curve based on the actual stress value change monitored at the stress monitoring points of the precast beam.

[0057] Furthermore, S4 includes:

[0058] S4-1: Compare the theoretical deformation curve of the precast beam with the actual deformation curve of the precast beam to generate a comparison curve;

[0059] S4-2: Analyze and compare the vulnerable parts in the curves and perform calculations to obtain the local prestress reserve assessment results;

[0060] S4-3: Calculate the area enclosed by the theoretical deformation curve and the coordinate axis and the actual deformation curve and the coordinate axis, compare the areas, and generate the overall prestress reserve assessment results.

[0061] S4-4: Compare the theoretical stress variation curve of the precast beam with the actual stress variation curve of the precast beam in the manner described in S4-2 and S4-3 to generate local stress value comparison results and overall stress value comparison results. Then, verify the generated local stress value comparison results and overall stress value comparison results with the local prestress reserve assessment results and overall prestress reserve assessment results. Attached Figure Description

[0062] Figure 1 This is a functional block diagram of an embodiment of the present invention;

[0063] Figure 2 This is a flowchart of an embodiment of the present invention. Detailed Implementation

[0064] The following detailed description illustrates the specific implementation method:

[0065] Stress monitoring throughout the entire life cycle of precast beams is mainly achieved through feedback on the prestress reserve state during tension control. After applying prestress to the precast beam, its prestress reserve and its uniformity will affect the structural safety of the precast beam under subsequent loads. Therefore, in order to enhance the control of prestress tension and realize the monitoring of stress throughout the entire life cycle, the current implementation plan mainly uses the strain gauge method to conduct experimental research on the effective prestress of the precast beam. By attaching strain gauges to the prestressing tendons of the precast beam, the change in resistance of the strain gauges is used to reflect the stress change relationship of the prestressing tendons. The problem with this approach is that the strain gauges are prone to damage during tensioning, and there is a problem that all strain gauges on some sections are completely damaged, resulting in low reliability.

[0066] To address the aforementioned issues, this application provides a precast beam full life-cycle stress monitoring system, the embodiments of which are basically as shown in the appendix. Figure 1 As shown: This includes several stress monitoring sensors, a module for generating theoretical stress changes in precast beams, a module for generating actual stress changes in precast beams, and a module for assessing the stress reserve state of precast beams. The stress monitoring sensors are deployed both inside and outside the precast beams at preset stress monitoring points. The number of stress monitoring points is not limited in this embodiment, but the number of stress sensors exceeds the data of the stress monitoring points. The specific deployment method is as follows:

[0067] First, historical construction data of precast beams is stored. The displacement changes of the precast beams at stress monitoring points within this historical data are then obtained. This historical data primarily comes from historical data established by the construction team based on previous construction plans. This historical data includes the distribution of stress monitoring points and the displacement changes of these points before and after tensioning control of the precast beam. The resulting displacement changes are assessed for fragility based on their magnitude and compared with a preset fragility threshold to generate vulnerable points and associated points. The preset fragility threshold represents the maximum stress that the stress sensor can withstand at the monitoring point. Under maximum stress, the stress sensor will suffer varying degrees of damage. If the damage exceeds this threshold... If the stress is too high, the stress sensor will stop working. The vulnerable point is the stress monitoring point that exceeds the preset vulnerability threshold. The cooperative point is an auxiliary stress monitoring point set near the vulnerable point. The displacement change value of the auxiliary stress monitoring point is less than the preset vulnerability threshold, so the stress detection device at that point will basically not be damaged. There are at least two cooperative points. At the same time, the stress sensors located at the cooperative points and the stress sensors at the vulnerable points are correlated and matched through a correlation coefficient algorithm, so that the monitoring value of the stress sensor at the cooperative point can represent the monitoring value of the stress sensor at the vulnerable point. In this embodiment, the correlation coefficient algorithm adopts the Pearson correlation coefficient algorithm.

[0068] Therefore, based on the setting of vulnerable points and cooperating points, stress sensors are pre-embedded inside the same vulnerable points and surface-mounted stress sensors at cooperating points during the actual precast beam casting process.

[0069] Furthermore, the aforementioned vulnerable points are only considered to be highly vulnerable in historical data. In the actual precast beam tensioning control process, the location of these vulnerable points may be inaccurate, and some vulnerable points from historical data may have shifted to nearby locations. In such cases, the coordinated points set up can also serve the function of monitoring vulnerable points, enabling more comprehensive full life-cycle stress monitoring.

[0070] The precast beam stress theoretical variation generation module is used to obtain the theoretical linear structure of the precast beam, construct a finite element model to simulate and analyze the stress variation state of the precast beam, and generate the theoretical stress variation of the precast beam. The precast beam stress theoretical variation generation module includes a precast beam linear structure acquisition unit, a theoretical stress value generation unit, a simulation unit, and a precast beam deformation calculation unit. The precast beam linear structure acquisition unit is used to obtain the linear structure of the precast beam placed on the pedestal and construct a finite element model of the precast beam. In this embodiment, the linear structure of the precast beam placed on the pedestal is obtained by acquiring the construction drawings transmitted by the construction worker, using MIDAS. The FEA (Fine Elements Analysis) software is used to establish finite element models and perform subsequent simulations. The theoretical stress value generation unit is used to generate theoretical stress values ​​at the stress monitoring points of the precast beam. The simulation unit is used to simulate the prestressing tensioning conditions at the actual construction site, simulate the stress value changes at the stress monitoring points of the precast beam finite element model, and simulate the linear structural changes of the precast beam as a function of stress values. The precast beam deformation calculation unit is used to extract the displacement positions of the precast beam before and after tensioning according to the preset deformation value extraction positions of the precast beam finite element model, calculate the theoretical deformation of the precast beam, and plot the theoretical deformation curve of the precast beam based on the theoretical deformation of the precast beam and the theoretical stress change curve based on the simulation results of the stress value changes at the stress monitoring points of the precast beam.

[0071] In this embodiment, the preset location for extracting deformation values ​​from the finite element model of the precast beam is the flange of the precast beam. This is because the precast beam is placed on a pedestal, making it difficult to collect data from the bottom. Since the deformation of the precast beam is an overall deformation, the flange is used as the location for extracting deformation values. By extracting the vertical displacement value of the flange, the deformation state of the precast beam can be reflected.

[0072] The precast beam stress actual change generation module is used to collect the linear structure of the precast beam before tensioning, the linear structure after tensioning, and the stress values ​​of the stress monitoring points before and after tensioning, construct a model to analyze the stress change state of the precast beam, and generate the actual change of precast beam stress. The precast beam stress actual change generation module includes a data acquisition unit, a data preprocessing unit, a data registration unit, and a data calculation unit. The data acquisition unit is used to acquire point cloud data of several stations before and after precast beam tensioning and to acquire the actual stress value change of the precast beam stress monitoring points by scanning with a 3D scanner. The data preprocessing unit is used to preprocess the acquired point cloud data and generate preprocessing results. In this embodiment, the preprocessing includes: (1) manually deleting useless points that deviate from the precast beam structure and retaining only the precast beam structure point cloud data; (2) performing point cloud noise reduction processing on the surface of the precast beam due to noise and isolated points generated by the instrument itself and external environmental interference during the scanning process using a Gaussian filtering algorithm.

[0073] The data registration unit is used to construct a point cloud model 1 of the precast beam before prestressing and a point cloud model 2 of the precast beam after prestressing after preprocessing, and to register the point cloud model 1 and the point cloud model 2 of the precast beam to generate a precast beam registration model. In this embodiment, the registration process includes coarse registration and fine registration. Coarse registration is achieved by extracting at least three or more non-collinear points with the same name from two adjacent sites and performing point cloud registration. Fine registration is achieved by using the ICP algorithm registration principle to find the nearest neighbor point and calculating according to specific constraints to make the target point cloud match the matching point cloud. Specifically, stable parts of the precast beam are selected as registration features, such as the platform or the ground, and at least three feature surfaces must be non-coplanar to control the three coordinate directions, thereby achieving fine registration.

[0074] After registration, the data calculation unit obtains the deformation values ​​of the precast beam before and after tensioning according to the preset deformation value extraction position and method of the precast beam registration model, calculates the actual deformation of the precast beam, and plots the actual deformation curve of the precast beam based on the actual deformation and the actual stress change curve based on the actual stress value change monitored at the stress monitoring points of the precast beam. In this embodiment, the preset deformation value extraction position of the precast beam registration model is the point cloud data of the flange part, and the preset deformation value extraction method of the precast beam registration model is to extract the point cloud with a width of 0.02m along the length direction of the precast beam as the research object, divide it into a small interval of 0.25m, and divide it into 160 parts in total. By cyclically extracting the vertical deformation value between each small interval, the linear change of the precast beam before and after tensioning is obtained, and the actual deformation curve of the precast beam is plotted.

[0075] The stress value change is obtained in real time through the stress sensors at the stress monitoring points on the precast beam, thereby plotting the actual stress change curve.

[0076] The precast beam stress reserve status assessment module compares the theoretical stress change of the precast beam with the actual stress change to assess the stress reserve status. This module includes a precast beam deformation curve comparison unit, a local prestress reserve assessment unit, an overall prestress reserve assessment unit, and a stress value comparison unit. The precast beam deformation curve comparison unit compares the theoretical deformation curve of the precast beam with the actual deformation curve to generate a comparison curve. This comparison curve reflects undesirable tensioning phenomena in the precast beam flanges, such as under-tensioning or lateral bending. Based on these phenomena and construction experience, the construction worker can predict the causes and implement timely remedial measures or improve subsequent construction methods.

[0077] The local prestress reserve assessment unit is used to calculate the location of vulnerable points in the comparison curve to obtain the local prestress reserve assessment result; in this embodiment, the calculation formula is:

[0078]

[0079] Wherein, U1 is the local prestress reserve, h1 is the actual deformation at the vulnerable location, h0 is the theoretical deformation at the vulnerable location, and the local prestress reserve is the ratio of the local stress value to the design value.

[0080] The overall prestress reserve assessment unit is used to calculate the area enclosed by the theoretical deformation curve and the coordinate axis, and to calculate the area enclosed by the actual deformation curve and the coordinate axis, and to compare the areas to generate the overall prestress reserve assessment result; in this embodiment, the calculation formula is:

[0081]

[0082] Where U2 represents the overall prestress reserve, S0 is the area enclosed by the theoretical deformation curve and the coordinate axis, S1 is the area enclosed by the actual deformation curve on the left and the coordinate axis, and S2 is the area enclosed by the actual deformation curve on the right and the coordinate axis. The overall prestress reserve is the ratio of the final stress value to the stress value reaching the design value.

[0083] The stress value comparison unit is used to compare the theoretical stress variation curve of the precast beam with the actual stress variation curve of the precast beam in the same way as the local prestress reserve assessment unit and the overall prestress reserve assessment unit, generating local stress value comparison results and overall stress value comparison results. The generated local stress value comparison results and overall stress value comparison results are then verified against the local prestress reserve assessment results and the overall prestress reserve assessment results. The stress value comparison unit enables the verification of local prestress assessment results and overall prestress assessment results.

[0084] Therefore, the advantage of this application is that, compared with the existing compression method of attaching strain gauges to the prestressing tendons of precast beams, this application assesses vulnerable points and cooperating points based on historical data, pre-embeds stress sensors at vulnerable points, and attaches stress sensors to the surface at cooperating points. This reduces the damage to stress sensors caused by displacement due to tension control of the precast beam, thus preventing stress sensors from failing to achieve full life cycle monitoring.

[0085] like Figure 2 As shown, in another embodiment of this example, a method for monitoring the stress throughout the entire life cycle of a precast beam is also included, comprising:

[0086] S1: Several stress monitoring points are pre-set during the casting of precast beams. Stress sensors are embedded inside these monitoring points and externally attached to them to construct a full life-cycle stress monitoring system. S1 includes:

[0087] S1-1: Preset historical construction data of precast beams and obtain the displacement change value of the precast beam at the stress monitoring point in the historical construction data of precast beams;

[0088] S1-2: Evaluate the vulnerability based on the displacement change value, and compare it with the preset vulnerability threshold to generate vulnerable points and several cooperating points;

[0089] S1-3: Pre-embed stress sensors inside vulnerable points and attach stress sensors to the surface at cooperating points.

[0090] S2: Obtain the theoretical linear structure of the precast beam, construct a finite element model to simulate and analyze the stress variation state of the precast beam, and generate the theoretical stress variation of the precast beam; wherein, S2 includes:

[0091] S2-1: Obtain the linear structure of the precast beam placed on the pedestal and construct the finite element model of the precast beam;

[0092] S2-2: Generate the theoretical stress values ​​at the stress monitoring points of the precast beam;

[0093] S2-3: Simulate the prestressing tensioning conditions at the actual construction site, simulate the stress value changes at the stress monitoring points of the precast beam finite element model, and simulate the linear structural changes of the precast beam as the stress value changes.

[0094] S2-4: Extract the displacement position of the precast beam before and after tensioning according to the preset deformation value extraction position of the precast beam finite element model, and calculate the theoretical deformation of the precast beam.

[0095] S2-5: Plot the theoretical deformation curve of the precast beam based on the theoretical deformation amount of the precast beam, and plot the theoretical stress variation curve based on the simulation results of the stress value changes at the stress monitoring points of the precast beam.

[0096] S3: Collect the linear structure of the precast beam before tensioning, the linear structure after tensioning, and the stress values ​​at stress monitoring points before and after tensioning; construct a three-dimensional model to analyze the stress change state of the precast beam and generate the actual stress change of the precast beam; S3 includes:

[0097] S3-1: Use a 3D scanner to scan and obtain point cloud data of several stations before and after prestressing of the precast beam. After data preprocessing, construct point cloud model 1 of the precast beam before prestressing and point cloud model 2 of the precast beam after prestressing. Register the point cloud model 1 and the point cloud model 2 of the precast beam to generate a precast beam registration model.

[0098] S3-2: Obtain the actual stress value change and coordinate points of the stress monitoring points on the precast beam, and register the coordinate points with the precast beam point cloud model one and the precast beam point cloud model two;

[0099] S3-3: Obtain the deformation values ​​of the precast beam before and after tensioning according to the preset deformation value extraction position and method of the precast beam registration model, and calculate the actual deformation of the precast beam;

[0100] S3-4: Draw the actual deformation curve of the precast beam based on the actual deformation amount of the precast beam, and draw the actual stress change curve based on the actual stress value change monitored at the stress monitoring points of the precast beam.

[0101] S4: Compare the theoretical stress change of the precast beam with the actual stress change of the precast beam to assess the stress reserve state of the precast beam. S4 includes:

[0102] S4-1: Compare the theoretical deformation curve of the precast beam with the actual deformation curve of the precast beam to generate a comparison curve;

[0103] S4-2: Analyze and compare the vulnerable parts in the curves and perform calculations to obtain the local prestress reserve assessment results;

[0104] S4-3: Calculate the area enclosed by the theoretical deformation curve and the coordinate axis and the actual deformation curve and the coordinate axis, compare the areas, and generate the overall prestress reserve assessment results.

[0105] S4-4: Compare the theoretical stress variation curve of the precast beam with the actual stress variation curve of the precast beam in the manner described in S4-2 and S4-3 to generate local stress value comparison results and overall stress value comparison results. Then, verify the generated local stress value comparison results and overall stress value comparison results with the local prestress reserve assessment results and overall prestress reserve assessment results.

[0106] The above are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for evaluating the stress reserve condition of a precast beam, characterized by: include: S1: Obtain pre-stored historical construction data of precast beams, and extract stress monitoring points and displacement change values ​​at stress monitoring points from the historical construction data of precast beams. S2: Evaluate the vulnerability based on the displacement change value and compare it with a preset vulnerability threshold. Stress monitoring points exceeding the preset vulnerability threshold are designated as vulnerable points, and auxiliary stress monitoring points near the vulnerable points are designated as coordinating points. Stress sensors are pre-embedded inside the vulnerable points and surface-mounted at the coordinating points. The stress sensors at the coordinating points and the vulnerable points are correlated and matched using a correlation coefficient algorithm. If a vulnerable point is damaged, the monitoring value at the coordinating points is obtained, and a vulnerable point monitoring value is generated using the correlation coefficient algorithm. If the actual vulnerable point shifts after the precast beam is poured, the coordinating points are used as vulnerable point monitoring locations. S3: Obtain the theoretical linear structure of the precast beam, construct a finite element model to simulate and analyze the stress change state of the precast beam, and generate the theoretical stress change of the precast beam; The linear structure of the precast beam before tensioning, the linear structure after tensioning, and the stress values ​​of stress monitoring points before and after tensioning are collected. A three-dimensional model is constructed to analyze the stress change state of the precast beam and generate the actual stress change of the precast beam. S4: Compare the theoretical change in precast beam stress with the actual change in precast beam stress to assess the stress reserve status of the precast beam. In S3, the linear structure of the precast beam before tensioning, the linear structure after tensioning, and the stress values ​​of stress monitoring points before and after tensioning are collected. A three-dimensional model is constructed to analyze the stress change state of the precast beam, and the actual stress change of the precast beam is generated as follows: Point cloud data of several stations before and after prestressing of the precast beam were obtained by scanning with a 3D scanner. After data preprocessing, a point cloud model 1 of the precast beam before prestressing and a point cloud model 2 of the precast beam after prestressing were constructed. The point cloud models 1 and 2 of the precast beam were then registered to generate a precast beam registration model. Specifically, the generation of the precast beam registration model includes coarse registration and fine registration. Coarse registration involves extracting at least three non-collinear points with the same name from two adjacent stations and performing point cloud registration. Fine registration involves using the ICP algorithm to find the nearest neighbor point and calculating according to specific constraints to make the target point cloud match the matching point cloud. Obtain the actual stress value change and coordinate points of the stress monitoring points on the precast beam, and register the coordinate points with the precast beam point cloud model one and the precast beam point cloud model two; The deformation values ​​of the precast beam before and after tensioning are obtained according to the preset deformation value extraction position and method of the precast beam registration model, and the actual deformation of the precast beam is calculated. The preset deformation value extraction position of the precast beam registration model is the point cloud data of the flange part. The specific method of the precast beam registration model deformation value extraction is to extract the point cloud of the preset width in the middle along the length direction of the precast beam as the research object, divide it into multiple small intervals, and extract the vertical deformation value between each small interval in a loop to obtain the linear change of the precast beam before and after tensioning, and draw the actual deformation curve of the precast beam. The actual deformation curve of the precast beam is plotted based on the actual deformation of the precast beam, and the actual stress change curve is plotted based on the actual stress value changes monitored at the stress monitoring points of the precast beam.

2. The method of claim 1, wherein: The preprocessing includes: Unnecessary points that deviate from the precast beam structure are manually deleted, and only the point cloud data of the precast beam structure is retained. Noise and isolated points on the surface of precast beams caused by interference from the instrument itself and the external environment during the scanning process are denoised using a Gaussian filtering algorithm.

3. The method of claim 1, wherein: In step S3, the theoretical linear structure of the precast beam is obtained, a finite element model is constructed to simulate and analyze the stress change state of the precast beam, and the theoretical stress change of the precast beam is generated as follows: Obtain the linear structure of the precast beam placed on the pedestal and construct the finite element model of the precast beam; Generate the theoretical stress values ​​for the stress monitoring points of the precast beam; Simulate the prestressing tensioning conditions at the actual construction site, simulate the stress value changes at the stress monitoring points of the precast beam finite element model, and simulate the linear structural changes of the precast beam as the stress value changes. The displacement positions of the precast beam before and after tensioning are extracted according to the preset deformation value extraction position of the precast beam finite element model, and the theoretical deformation of the precast beam is calculated. The theoretical deformation curve of the precast beam is plotted based on the theoretical deformation amount, and the theoretical stress variation curve is plotted based on the simulation results of stress value changes at stress monitoring points of the precast beam.

4. The method of claim 3, wherein: The preset deformation value extraction location of the precast beam finite element model is the flange of the precast beam.

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