Concrete column damage evaluation method based on piezoelectric sensing technology

Abstract

The invention provides a concrete column damage evaluation method based on a piezoelectric sensing technology, and the method comprises the steps: pre-burying a plurality of piezoelectric sensors in the most sensitive damage section of a column body before the pouring of a to-be-monitored concrete column; collecting charge signals output by each piezoelectric sensor in the process that the concrete column to be monitored is subjected to an external load, respectively converting the charge signals into concrete axial strain at the corresponding sensor arrangement position, and calculating concrete axial stress at the corresponding position based on the concrete axial strain; according to the concrete axial stress and axial strain data of each monitoring point, concrete compression damage factors of the corresponding monitoring points are calculated; calculating an average value of concrete compression damage factors of all monitoring points on the most sensitive damage section, and taking the average value as an average damage index of the section; and judging the overall damage grade of the to-be-monitored concrete column by taking the section average damage index as an evaluation index of the to-be-monitored concrete column from material damage to component overall damage.

Description

Technical Field

[0001] This invention belongs to the field of civil engineering structural health monitoring technology, specifically relating to a method for evaluating the damage of concrete columns based on piezoelectric sensing technology, which is particularly applicable to the damage monitoring and performance evaluation of steel-concrete composite columns and other reinforced concrete components under load. Background Technology

[0002] Current widely used methods for assessing concrete column damage primarily focus on seismic damage at the component level, generally neglecting the material-level damage evolution process. They cannot extrapolate the internal forces and deformation time histories of the component from material damage alone. These methods mainly propose quantitative performance indicators from macroscopic perspectives such as deformation, strength and stiffness degradation, and energy consumption to establish seismic damage models; a typical example is the Park-Ang damage model and its improved versions. While these methods are widely applied, they struggle to directly reflect the material-level damage evolution process and are difficult to obtain core evaluation indicators such as internal forces and energy dissipation in practical engineering.

[0003] The essence of structural and component failure lies in the failure of its constituent materials. Understanding the performance state of structures and components at the material level has an inherent theoretical advantage. Currently, component damage evaluation methods based on material damage information can only be applied to numerical simulation scenarios. How to effectively extract and quantify material damage information in experiments and actual engineering has become a core technical challenge in this field.

[0004] Existing methods for assessing damage to steel-concrete composite columns also focus on the component level. While component-level damage models based on experimental results can reflect the degree of damage to components macroscopically, these models are all constructed based on macroscopic indicators such as loads, displacements, and energy measured in experiments. The core evaluation parameters are also difficult to obtain in actual engineering. Furthermore, existing macroscopic component-level models are all based on statistical fitting of the overall macroscopic mechanical response of the component, failing to directly reveal and correlate the damage accumulation process inside the material. The connection between the theoretical basis and the component failure mechanism is not close enough. Summary of the Invention

[0005] To address the shortcomings and deficiencies of existing technologies, this invention provides a method and system for evaluating concrete column damage based on intelligent piezoelectric sensing technology. It primarily solves the industry pain points that existing concrete column damage assessment schemes mostly focus on the macroscopic level of the component, failing to correlate with the internal damage evolution process of the material. Furthermore, core evaluation parameters are difficult to obtain effectively in practical engineering, and material-level damage assessment methods are difficult to apply. This invention pre-embeds multiple piezoelectric sensors in the most sensitive damage section at a distance of 0.3 to 0.6 times the cross-sectional side length from the column bottom before concrete pouring. The sensors collect the charge signals output by each sensor during the application of external loads and convert them into axial stress and strain data of the concrete at the corresponding locations. Based on the strain equivalence assumption in continuous medium damage mechanics, the concrete stress and strain data at each monitoring point are converted into corresponding compressive damage factors. The average value of the damage factors at all monitoring points within the cross-section is used as the average damage index of the cross-section, serving as the core evaluation basis for the overall damage of the concrete column. Combined with damage threshold ranges corresponding to different performance stages determined through statistical testing, the damage level of the concrete column is determined. This invention constructs a multi-level, cross-scale damage evaluation system for materials, sections, and components, enabling direct, accurate, and real-time monitoring of hidden damage within concrete. It does not rely on macroscopic mechanical parameters that are difficult to obtain in engineering. The damage evaluation results are highly consistent with classical component damage models, and the theoretical basis is closely linked to the component failure mechanism. It can provide quantitative support for the performance-based design of concrete columns, post-earthquake safety assessment of structures, and reinforcement design. It is applicable to damage monitoring and performance evaluation of steel-concrete composite columns, asymmetric steel-concrete composite columns, and various reinforced concrete components under earthquake, impact, and other loads.

[0006] The specific technical solution adopted by this invention to solve its technical problem is as follows:

[0007] A method for evaluating the damage of concrete columns based on piezoelectric sensing technology includes:

[0008] Before the concrete column to be monitored is poured, multiple piezoelectric sensors are pre-embedded in the most sensitive damage section of the column.

[0009] The charge signals output by each piezoelectric sensor are collected during the process of the concrete column under external load.

[0010] Each of the charge signals is converted into the axial strain of the concrete at the corresponding sensor placement location, and the axial stress of the concrete at the corresponding location is calculated based on the axial strain of the concrete.

[0011] Based on the concrete axial stress and axial strain data at each monitoring point, calculate the concrete compressive damage factor at the corresponding monitoring point, ignoring the influence of concrete tensile damage on the evaluation results.

[0012] Calculate the average value of the concrete compressive damage factor at all monitoring points on the most sensitive damage section, and use this average value as the average damage index of the section.

[0013] The average damage index of the cross section is used as an evaluation index for the concrete column under monitoring, from material damage to overall component damage, to determine the overall damage level of the concrete column under monitoring.

[0014] Furthermore, the height range of the most sensitive damage section is 0.3 meters from the bottom of the concrete column to be monitored. Up to 0.6 ,in The side length of the cross section of the concrete column to be monitored.

[0015] Furthermore, the process of converting the charge signal into concrete axial strain and axial stress is as follows: First, an external calibration test is carried out on the piezoelectric sensor before pre-embedding to obtain the calibration parameters of the sensor; then, based on the calibration parameters and the collected charge signal, the concrete axial strain at the corresponding position is calculated in combination with the pre-embedding environment correction factor; finally, based on the concrete axial strain and the adapted concrete constitutive model, the concrete axial stress at the corresponding position is obtained.

[0016] Furthermore, the pre-embedded environment correction factor is used to correct the difference in medium and boundary constraints between the sensor after it is pre-embedded in the concrete and the external calibration environment, and is fixed at a value of 1.1.

[0017] Furthermore, the formula for calculating the concrete compressive damage factor is as follows:

[0018]

[0019] in, It is a factor of concrete compressive damage. =0 corresponds to an undamaged state of the concrete. =1 corresponds to the state of complete concrete failure; The elastic strain of the concrete due to damage; The non-destructive elastic modulus of concrete; For the nominal stress of concrete without considering damage effects, The actual stress of concrete after taking into account damage effects.

[0020] Furthermore, the piezoelectric sensors are symmetrically and uniformly arranged along the cross-section of the concrete column to be monitored, with a number of no less than 5, covering different areas from the edge of the cross-section to the interior.

[0021] Furthermore, the damage threshold range used to determine the damage level of concrete columns is determined in the following way: Based on the statistical results of experiments and numerical simulations, the Kolmogorov-Smirnov test is used to obtain the normal distribution curve of damage values ​​at each key performance point of the macroscopic plastic development of concrete columns. The upper limit of the normal distribution function corresponding to each key performance point is taken as the critical damage value of that performance point, thus forming the damage threshold range corresponding to different performance stages.

[0022] Furthermore, when using the cross-sectional average damage index as the overall damage evaluation index, the cross-sectional average damage index is compared with the occurrence time of the key points of macroscopic plastic development of concrete columns to establish the correlation between the cross-sectional average damage index and the plastic development and performance state of concrete columns; the key points of macroscopic plastic development of concrete columns include concrete cracking, longitudinal reinforcement yielding, steel section yielding, and concrete crushing.

[0023] Furthermore, the concrete column to be monitored is a steel-concrete composite column or a reinforced concrete column, wherein the steel-concrete composite column includes asymmetric steel-concrete composite columns.

[0024] Furthermore, a concrete column damage evaluation system is provided for performing the methods described above, comprising a piezoelectric sensing module, a data acquisition module, a data processing module, and a damage evaluation module; the piezoelectric sensing module includes several piezoelectric sensors embedded in the most sensitive damage section of the concrete column to be monitored, for acquiring charge signals during the loading process of the concrete column; the data acquisition module is communicatively connected to the piezoelectric sensing module and is used to acquire the charge signals output by each piezoelectric sensor; the data processing module is communicatively connected to the data acquisition module and is used to convert the charge signals into concrete axial strain and axial stress, and calculate the concrete compressive damage factor and cross-sectional average damage index at each monitoring point; the damage evaluation module is communicatively connected to the data processing module and is used to use the cross-sectional average damage index as the overall damage evaluation index of the concrete column to determine the overall damage level of the concrete column.

[0025] Compared to existing technologies, this invention and its preferred solutions construct a multi-level, cross-scale damage evaluation system encompassing materials, sections, and components. Starting from the material nature of structural component failure, it directly links the damage accumulation process within concrete materials with the overall performance state of the component. This effectively compensates for the shortcomings of existing component-level macroscopic damage models, which lack a strong connection between theoretical foundation and structural failure mechanisms, allowing damage evaluation results to more fundamentally reflect the actual performance state of the structure. Based on piezoelectric sensing technology, this invention enables the direct and real-time extraction of hidden damage information within concrete, eliminating the need to rely on macroscopic mechanical parameters such as internal forces and energy consumption, which are difficult to obtain effectively in actual engineering. This solves the industry pain point that existing material-level damage evaluation methods are only applicable to numerical simulation scenarios and difficult to implement in experimental and practical engineering applications. The operation process is convenient and efficient, possessing strong engineering practicality. By deploying sensors in the damage-sensitive areas of concrete columns, this invention can comprehensively cover the concrete damage state at different locations along the cross-section, accurately capturing the damage evolution information of concrete under various loads, ensuring the comprehensiveness of damage monitoring data and the accuracy of damage evaluation results. Meanwhile, the damage evaluation results of this invention are highly consistent with the classic component damage evaluation models in the field, and the scientificity and reliability of the method have been fully verified. Furthermore, the damage threshold range corresponding to different performance stages of the structure has been determined through statistical methods, realizing the quantitative and standardized determination of the damage level of concrete columns. This can provide stable quantitative technical support for the performance-based design of concrete structures, post-earthquake safety assessment, and reinforcement design, and can be widely applied to damage monitoring and performance evaluation scenarios of various types of steel-concrete columns and reinforced concrete components under various loads. Attached Figure Description

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0027] Figure 1 This is a flowchart illustrating the technical solution of the concrete column damage evaluation method based on intelligent piezoelectric sensing technology according to an embodiment of the present invention.

[0028] Figure 2 This is a flowchart illustrating the internal stress monitoring process of concrete based on intelligent piezoelectric sensing technology, as described in an embodiment of the present invention.

[0029] Figure 3 This is a cross-sectional information diagram of an asymmetric steel reinforced concrete (SRC) column specimen according to an embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram showing the arrangement of the intelligent piezoelectric sensor within the target cross-section of a concrete column according to an embodiment of the present invention;

[0031] Figure 5The figure shows the relationship between horizontal load, charge, stress, damage and time for specimen SRC2 in this embodiment of the invention. In the figure, (a) is the time history curve of horizontal load of specimen, (b) is the time history curve of charge obtained by sensor, (c) is the time history curve of concrete stress change at the sensor placement location, and (d) is the time history curve of concrete damage factor at the sensor placement location.

[0032] Figure 6 The figure shows a comparison of the damage factor calculation results of the damage evaluation method proposed in this embodiment of the invention and the classic Park-Ang damage model. In the figure, (a) is the damage factor comparison time history curve of the SRC1 specimen, (b) is the damage factor comparison time history curve of the SRC2 specimen, (c) is the damage factor comparison time history curve of the SRC3 specimen, and (d) is the damage factor comparison time history curve of the SRC4 specimen. Detailed Implementation

[0033] To make the features and advantages of the present invention more apparent and understandable, specific embodiments are described below in detail:

[0034] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0036] To address the shortcomings of existing technologies, this invention provides a concrete column damage evaluation scheme based on intelligent piezoelectric sensors. By pre-embedded sensors to monitor concrete stress in real time and combining this with damage mechanics theory, a multi-level quantitative evaluation of the overall damage to the component, from material to cross-section, is achieved. This provides technical support for damage assessment and reinforcement. The implementation process of this invention is as follows: Figure 1 As shown:

[0037] 1. Pre-embedded intelligent piezoelectric sensor

[0038] Before pouring the concrete column, multiple intelligent piezoelectric sensors are pre-embedded within the height range of the most sensitive damage section to monitor the axial stress inside the concrete. The pre-embedding range is 0.3h to 0.6h from the bottom of the column, where h is the side length of the column section. The sensors are symmetrically and evenly arranged along the section, covering different positions from the edge of the column section to the interior, and the number should preferably be more than 5 to ensure comprehensive monitoring of the concrete damage state at all locations of the section.

[0039] 2. Acquire the charge signal output by the sensor under external load.

[0040] Under external loads, the data acquisition instrument synchronously and continuously records the charge signals generated by each intelligent piezoelectric sensor in the concrete column: the external load can be seismic action, impact load, or load applied by laboratory instruments.

[0041] 3. The charge signal is converted into concrete stress.

[0042] The charge signal collected by the sensor is processed according to... Figure 2 The method converts the data into time history data of the axial stress of concrete at the sensor deployment location. Here, K1 is the external calibration sensitivity; γ is the correction factor with a value of 1.1; and E1 is the sensor's elastic modulus.

[0043] This step, through four core processes—pre-calibration of the piezoelectric sensor, acquisition of charge signals under load, calculation of concrete axial strain, and conversion of concrete axial stress—completely converts the charge signals acquired in real time by the sensor into time-history data of concrete axial stress at the sensor's location.

[0044] 3.1 External calibration of piezoelectric sensor to obtain core calculation parameters

[0045] Before embedding the sensor into the concrete structure, a standard external calibration test must be conducted on the smart piezoelectric sensor to pre-determine the two core basic parameters required for the calculation in this step. The calibration process must comply with the piezoelectric sensor metrology specifications to ensure that the parameters correspond one-to-one with the sensor used.

[0046] Sensor external calibration sensitivity K1: The charge value output by the sensor under a unit force is measured through a standard force loading calibration test, and the unit is pC / N;

[0047] Sensor elastic modulus E1: The elastic modulus of the piezoelectric sensor substrate is determined by material mechanical property testing. The unit is Pa. The standard elastic modulus value calibrated by the sensor manufacturer can be used directly.

[0048] 3.2 Sensor Embedding and Charge Signal Acquisition under Load

[0049] After calibration, the calibrated intelligent piezoelectric sensors are pre-embedded in the damage-sensitive section of the concrete column according to the deployment rules in Part 1 of this plan, and the component is poured and cured according to standard. When the component is subjected to external loads (earthquake load, impact load, load applied by laboratory instruments, etc.), the real-time charge signals output by each sensor are synchronously and continuously collected by the matching data acquisition instrument to form a charge time history curve Q2 that matches the loading time history, where Q2 is the instantaneous charge value output by the sensor at time t, and the unit is pC.

[0050] 3.3 Calculation of Axial Strain in Concrete

[0051] Based on the core parameters obtained from pre-calibration and the real-time acquired charge signals, combined with the pre-embedded environmental correction factor, the real-time axial strain of the concrete at the sensor placement location is calculated using the following formula. The calculation formula is:

[0052]

[0053] in, An environmental correction factor is embedded in the sensor to correct for differences in media and boundary constraints between the sensor and the external calibration environment after the sensor is embedded in the concrete.

[0054] The above formula can be used to completely convert the charge time history curve Q2 collected at each time step into the concrete axial strain time history data at the corresponding time step.

[0055] 3.4 Time History Transformation of Axial Stress in Concrete

[0056] Based on the calculated concrete axial strain time history data, combined with the measured material properties of the concrete used in the target component, a suitable concrete constitutive model is selected to convert the strain time history data into concrete axial stress time history data at the corresponding time points. The specific implementation requirements are as follows:

[0057] (1) Obtaining concrete material property parameters: The core material property parameters such as axial compressive strength, non-destructive elastic modulus, Poisson's ratio, peak strain, and ultimate strain of concrete are obtained through standard mechanical performance tests of the same batch of concrete in the component, and are used as the input basis for the constitutive model;

[0058] (2) Selection of concrete constitutive model: The uniaxial compression constitutive model of concrete recommended by the Code for Design of Concrete Structures GB 50010 should be given priority. Alternatively, a suitable constitutive model such as concrete damage plastic constitutive model or nonlinear elastic constitutive model can be selected according to the stress characteristics of the component to ensure that the strain-stress conversion relationship is fully matched with the actual mechanical properties of the concrete used.

[0059] (3) Stress time history output: The axial strain of concrete at each time step. Select the concrete constitutive model, solve to obtain the axial stress value of the concrete at the corresponding moment, and finally form the axial stress time history curve of the concrete that is completely synchronized with the loading time history and the charge time history, completing the full-process conversion from the charge signal to the concrete stress.

[0060] 4. Stress is converted into the damage factor

[0061] Based on the strain equivalence hypothesis in the continuum damage mechanics, use Equation (1) to convert the concrete stress-strain data at each monitoring point into the compressive damage factor, ignoring the influence of tensile damage on the evaluation result (under the combined action of compression and bending loads on the concrete column, compressive damage is the main controlling factor for component failure, and the influence of tensile damage on the overall damage evaluation result of the component is extremely small. Therefore, the influence of tensile damage is ignored in this scheme).

[0062] (1)

[0063] In the formula: ε is the damaged elastic strain; E is the undamaged elastic modulus of the material; is the nominal stress without considering damage; is the actual stress considering the damage effect. D is the damage factor, D = 0 for the undamaged state, D = 1 for complete failure, and 0 < D < 1 corresponds to different degrees of damage.

[0064] 5. Calculate the average damage index of the cross-section

[0065] Calculate the average value of the concrete compressive damage factors at all the monitoring points of the embedded piezoelectric sensors on the cross-section as the average damage index of this cross-section:

[0066] (2)

[0067] Among them, n is the number of monitoring points on the cross-section, and D c,i is the concrete damage factor of the i-th monitoring point.

[0068] 6. Evaluate the overall damage of the component

[0069] Take the average damage index of the cross-section as the overall damage evaluation index of the component, compare the average damage curve of the cross-section with the occurrence time of the key points of the macroscopic plastic development of the specimen (such as concrete cracking, longitudinal bar yielding, shape steel yielding, concrete crushing), and establish its correlation with the plastic development and performance state of the component.

[0070] 7. Determine the damage grade

[0071] Based on extensive experimental and numerical statistical results, the KS test was used to obtain the normal distribution curve of the damage value at each performance point. The upper limit of the normal distribution function at each performance point with a 95% confidence level was taken as the critical damage value for that performance point, forming the damage threshold intervals corresponding to different performance stages, thus realizing the classification of damage levels, as shown in Table 1:

[0072] Table 1 Damage thresholds at different performance stages

[0073]

[0074] The implementation of the present invention will be further demonstrated and described below through more specific test examples:

[0075] Nine asymmetrical steel-reinforced reinforced concrete (SRC) columns were fabricated, with cross-sectional dimensions of 300mm × 300mm. Five varying parameters were considered: shear span ratio, flange width-to-thickness ratio, steel reinforcement method, loading angle, and vertical load eccentricity. Detailed test parameters are shown in Table 2. The concrete strength grade was C30, the steel grade was Q235, and four HRB400 grade longitudinal reinforcing bars with a diameter of 18mm were symmetrically arranged. Specimen cross-sectional information is as follows: Figure 3 As shown.

[0076] Table 2. Quasi-static test parameters for asymmetric steel reinforced SRC columns

[0077]

[0078] During specimen casting, five intelligent piezoelectric sensors were pre-embedded within a height range of 0.3h to 0.6h from the bottom of the column (h = 300mm, i.e., a height range of 90mm to 180mm), covering the edge of the cross-section to the interior. The specific arrangement is as follows: Figure 4 As shown in the figure. In a further preferred embodiment, five intelligent piezoelectric sensors are symmetrically and evenly arranged along the horizontal central axis of the cross section. Two sensors are respectively placed at the left and right edges of the cross section, and the remaining three sensors are evenly spaced along the central axis toward the interior of the cross section, completely covering different stress areas from the edge of the cross section to the core area, ensuring comprehensive capture of the concrete damage state at all locations of the cross section.

[0079] During loading, a constant vertical load was first applied to the top of the column using hydraulic jacks according to the axial compression ratio requirements of the specimen. Subsequently, a horizontal low-cycle repetitive load was applied to the top of the column using an electro-hydraulic servo actuator. Concrete stress data were collected by a data acquisition instrument, and the test process was controlled by a servo controller and a computer.

[0080] Taking SRC2 column as an example, the outermost sensor S5, which is embedded in the 110mm height section, is taken as the analysis object. Under horizontal load ( Figure 5 (a) The charge signal obtained by the sensor monitoring ( Figure 5(b) Convert the stress at that location to concrete stress using the method in step 3. Figure 5 (c) According to the concrete damage factor calculation method in step 4, the concrete stress is converted into the concrete damage factor. Figure 5 (d)).

[0081] Calculate the most sensitive section (110mm height, 0.37). The average damage factor of the five horizontal sensors (S1~S5) on the specimen is used as the overall damage index of the specimen.

[0082] Damage levels were determined based on damage indices: the initial damage index of a specimen was 0.05, indicating it was basically intact; the damage index was 0.32 when the longitudinal reinforcement yielded, indicating minor damage; the damage index was 0.61 when the bearing capacity peaked, indicating moderate damage; the damage index was 0.93 when the bearing capacity limit was reached, indicating severe damage; and the damage index reached 0.98 after the concrete cover was crushed, indicating specimen failure.

[0083] To verify the feasibility of the proposed damage index, the classic Park-Ang damage model for evaluating component levels was used as a comparison, such as... Figure 6 As shown. Among them, Figure 6 (a) shows the time history curves of damage factors for the SRC1 specimen. Figure 6 (b) shows the time history curves of damage factors for the SRC2 specimen. Figure 6 (c) shows the time history curves of damage factors for the SRC3 specimen. Figure 6 (d) shows the time history curves of damage factors for the SRC4 specimen. The comparison results show that the development trend of damage factors calculated by the method of the present invention is in high agreement with the classical Park-Ang model, which verifies the feasibility and accuracy of the method of the present invention.

[0084] In summary, the correspondence between damage indices and damage levels based on material level was established, thereby determining the threshold of damage index for asymmetric steel reinforced concrete (SRC) components under different performance levels (Table 3). This can provide a basis for performance-based design, post-earthquake safety assessment of structures, and reinforcement design.

[0085] Table 3 Damage thresholds at different performance stages

[0086]

[0087] In summary, compared with the prior art, the present invention can accurately capture the damage information of concrete under seismic action by pre-embedding intelligent piezoelectric sensors at the most sensitive damage section (0.3h~0.6h away from the bottom of the column). The sensor arrangement covers the edge of the section to the inside, ensuring the comprehensiveness and accuracy of damage monitoring.

[0088] By utilizing the sensing characteristics of piezoelectric sensors, the charge signal of concrete can be directly acquired and converted into stress, thereby calculating the damage factor. This eliminates the need to extract the macroscopic mechanical parameters of the component, solving the problem of difficulty in extracting damage information in existing material-level damage evaluation methods. The method is convenient and efficient.

[0089] A multi-level damage evaluation correlation of "material-section-component" was established, and the average concrete compressive damage factor of the section was used as the overall damage index of the component. The evaluation results showed good consistency with the classic Park-Ang damage model, ensuring the reliability and scientific nature of the evaluation method.

[0090] The threshold values ​​of damage indicators corresponding to each damage level have been clearly defined, providing a quantitative basis for determining the damage level of concrete columns, assessing their safety, and designing reinforcement. This approach is highly practical and has broad prospects for engineering applications.

[0091] The key designs of the above-mentioned scheme of this invention include: ① Detecting concrete material damage using sensors: Direct and objective measurement of hidden material damage is achieved through piezoelectric sensors pre-embedded in the cross-section of a specific height of the SRC column. ② Identifying and assessing structural damage using material damage: By establishing a damage transmission correlation between "material-section-component", the concrete material damage factors obtained from multiple monitoring points are averaged across the cross-section, and this average damage factor is used as the core indicator to characterize and assess the overall damage degree and plastic development state of the SRC component. ③ Determining damage thresholds at different stages: Based on a large amount of experimental and numerical simulation data, statistical analysis is used to determine the damage factor threshold range corresponding to the four key performance stages of the asymmetric steel-reinforced SRC column: cracking, longitudinal reinforcement yielding, peak bearing capacity, and ultimate bearing capacity. This provides a clear criterion for the quantitative assessment of post-earthquake damage levels of the structure.

[0092] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

[0094] This invention is not limited to the preferred embodiment described above. Anyone inspired by this invention can derive various other forms of a method for evaluating the damage of concrete columns based on piezoelectric sensing technology. All equivalent variations and modifications made within the scope of the claims of this invention should be included within the scope of this invention.

Claims

1. A method for evaluating damage to concrete columns based on piezoelectric sensing technology, characterized in that, include: Before the concrete column to be monitored is poured, multiple piezoelectric sensors are pre-embedded in the most sensitive damage section of the column. The charge signals output by each piezoelectric sensor are collected during the process of the concrete column under external load. Each of the charge signals is converted into the axial strain of the concrete at the corresponding sensor placement location, and the axial stress of the concrete at the corresponding location is calculated based on the axial strain of the concrete. Based on the concrete axial stress and axial strain data at each monitoring point, calculate the concrete compressive damage factor at the corresponding monitoring point, ignoring the influence of concrete tensile damage on the evaluation results. Calculate the average value of the concrete compressive damage factor at all monitoring points on the most sensitive damage section, and use this average value as the average damage index of the section. The average damage index of the cross section is used as an evaluation index for the concrete column under monitoring, from material damage to overall component damage, to determine the overall damage level of the concrete column under monitoring.

2. The method for evaluating damage to concrete columns based on piezoelectric sensing technology according to claim 1, characterized in that: The height range of the most sensitive damage section is 0.3 meters from the bottom of the concrete column to be monitored. Up to 0.6 ,in The side length of the cross section of the concrete column to be monitored.

3. The method for evaluating damage to concrete columns based on piezoelectric sensing technology according to claim 1, characterized in that: The process of converting charge signals into concrete axial strain and axial stress is as follows: First, an external calibration test is carried out on the piezoelectric sensor before pre-embedding to obtain the calibration parameters of the sensor; then, based on the calibration parameters and the collected charge signals, the concrete axial strain at the corresponding position is calculated in combination with the pre-embedding environment correction factor; finally, the concrete axial stress at the corresponding position is obtained by converting the concrete axial strain with the adapted concrete constitutive model.

4. The method for evaluating damage to concrete columns based on piezoelectric sensing technology according to claim 3, characterized in that: The embedded environment correction factor is used to correct the difference in medium and boundary constraints between the sensor and the external calibration environment after the sensor is embedded in the concrete. The fixed value is 1.

1.

5. The method for evaluating damage to concrete columns based on piezoelectric sensing technology according to claim 1, characterized in that: The formula for calculating the concrete compressive damage factor is as follows: in, It is a factor of concrete compressive damage. =0 corresponds to an undamaged state of the concrete. =1 corresponds to the state of complete concrete failure; The elastic strain of the concrete due to damage; The non-destructive elastic modulus of concrete; For the nominal stress of concrete without considering damage effects, The actual stress of concrete after taking into account damage effects.

6. The method for evaluating damage to concrete columns based on piezoelectric sensing technology according to claim 1, characterized in that: The piezoelectric sensors are symmetrically and evenly arranged along the cross-section of the concrete column to be monitored, with a number of no less than 5, covering different areas from the edge of the cross-section to the interior.

7. The method for evaluating damage to concrete columns based on piezoelectric sensing technology according to claim 1, characterized in that: The damage threshold range used to determine the damage level of concrete columns is determined in the following way: Based on the statistical results of experiments and numerical simulations, the Kolmogorov-Smirnov test is used to obtain the normal distribution curve of damage values ​​at each key performance point of the macroscopic plastic development of concrete columns. The upper limit of the normal distribution function corresponding to each key performance point is taken as the critical damage value of that performance point, thus forming the damage threshold range corresponding to different performance stages.

8. The method for evaluating damage to concrete columns based on piezoelectric sensing technology according to claim 7, characterized in that: When using the cross-sectional average damage index as the overall damage evaluation index, the cross-sectional average damage index is compared with the occurrence time of the key points of macroscopic plastic development of concrete columns to establish the correlation between the cross-sectional average damage index and the plastic development and performance state of concrete columns; the key points of macroscopic plastic development of concrete columns include concrete cracking, longitudinal reinforcement yielding, steel section yielding, and concrete crushing.

9. The method for evaluating damage to concrete columns based on piezoelectric sensing technology according to claim 1, characterized in that: The concrete column to be monitored is a steel-concrete composite column or a reinforced concrete column, wherein the steel-concrete composite column includes asymmetric steel-concrete composite columns.

10. A concrete column damage evaluation system, characterized in that, The method for performing any one of claims 1 to 9 comprises a piezoelectric sensing module, a data acquisition module, a data processing module, and a damage evaluation module; the piezoelectric sensing module includes a plurality of piezoelectric sensors for pre-embedding in the most sensitive damage section of the concrete column to be monitored, for acquiring charge signals during the loading process of the concrete column; the data acquisition module is communicatively connected to the piezoelectric sensing module, for acquiring charge signals output by each piezoelectric sensor; the data processing module is communicatively connected to the data acquisition module, for converting the charge signals into axial strain and axial stress of the concrete, and calculating the concrete compressive damage factor and cross-sectional average damage index at each monitoring point; the damage evaluation module is communicatively connected to the data processing module, for using the cross-sectional average damage index as the overall damage evaluation index of the concrete column, and determining the overall damage level of the concrete column.

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