A method and system for evaluating the durability of a fabricated hollow sandwich steel pipe concrete bridge pier

Abstract

The application provides an assembled hollow sandwich steel pipe concrete pier durability evaluation method and system, and relates to the technical field of pier durability evaluation. The method comprises the following steps: obtaining monitoring data of the pier during service, calculating the corrosion activity index of the outer steel pipe and the interface peeling risk coefficient of the inner layer based on the corrosion potential and temperature strain in the monitoring data, and determining the water saturation degree grade value based on the difference between the relative humidity and the preset threshold value; constructing a durability state evaluation model based on the corrosion activity index, the peeling risk coefficient and the water saturation degree grade value, determining the current time durability comprehensive score, and combining the time domain characteristics of the pier top displacement time series data to determine whether the pier has a stiffness degradation trend; correcting the durability comprehensive score according to the stiffness degradation trend determination result, comparing the corrected score with the preset grade threshold value, and outputting the pier durability grade evaluation result.

Description

Technical Field

[0001] This invention relates to the field of bridge pier durability assessment technology, specifically to a method and system for assessing the durability of prefabricated hollow-core steel-concrete composite bridge piers. Background Technology

[0002] Prefabricated hollow-core steel-concrete composite piers are a new type of composite structure pier, consisting of two layers of steel tubes and a middle layer of concrete. The core is a hollow structure, which has advantages such as light weight, high bending stiffness, fast construction speed, and easy passage of pipelines, and has been increasingly widely used in modern bridge engineering. However, during long-term service, these piers face multiple durability deterioration problems, including electrochemical corrosion of the outer steel tube, delamination between the inner steel tube and the concrete interface, and moisture penetration into the middle layer of concrete. These damage factors are coupled and jointly affect the overall safety and service life of the pier. Therefore, how to scientifically and accurately assess the durability status of prefabricated hollow-core steel-concrete composite piers has become an urgent technical problem to be solved in the field of bridge maintenance and management.

[0003] In the prior art, a method for in-situ monitoring, deduction, and evaluation of the durability of concrete structures in marine environments, disclosed in CN117695692A, uses concrete comparative specimens to monitor durability limit state assessment indicators such as the time when the reinforcing steel begins to corrode, the chloride ion concentration evaluation value, and the time when the concrete cover rusts and cracks under chloride salt conditions. This allows for the calculation of durability grading indicators to determine the durability level of the concrete structure. While this method primarily addresses the durability assessment of traditional reinforced concrete structures in marine chloride salt environments, it does not cover special composite structures like prefabricated hollow-core steel-concrete composite piers. For such piers, durability deterioration involves not only chloride ion corrosion of the interlayer concrete but also electrochemical corrosion of the outer steel tube, the risk of delamination between the inner steel tube and the concrete interface, and the overall structural stiffness degradation trend. Existing methods cannot comprehensively cover these key assessment indicators and are therefore unable to accurately reflect the actual durability state of prefabricated hollow-core steel-concrete composite piers.

[0004] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for evaluating the durability of prefabricated hollow steel-concrete composite bridge piers, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method and system for evaluating the durability of prefabricated hollow-core steel-concrete composite bridge piers, comprising the following steps: Step 1: Obtain monitoring data of the prefabricated hollow steel tube concrete bridge pier during its service life. The monitoring data includes corrosion potential of the outer steel tube, temperature and strain at the interface between the inner steel tube and the concrete, relative humidity inside the sandwich concrete, and time series data of pier top displacement. Step 2: Based on the corrosion potential of the outer steel pipe and the temperature strain at the interface between the inner steel pipe and the concrete, calculate the corrosion activity index of the outer steel pipe and the peeling risk coefficient of the inner interface, and determine the water saturation level of the interlayer concrete based on the difference between the relative humidity inside the interlayer concrete and the preset humidity threshold. Step 3: Construct a durability status assessment model based on the corrosion activity index of the outer steel pipe, the peeling risk coefficient of the inner interface, and the water saturation level of the interlayer concrete. Use the model to determine the comprehensive durability score of the pier at the current moment. Based on the comprehensive durability score and the time-domain characteristics of the pier top displacement time series data, determine whether the pier has a stiffness degradation trend. Step 4: Correct the overall durability score based on the determination result of stiffness degradation trend to obtain the corrected overall durability score. Compare the corrected overall durability score with the preset durability level threshold and output the durability level evaluation result of the pier.

[0007] Furthermore, the specific logic for acquiring monitoring data is as follows: A corrosion potential sensor is arranged on the outer wall of the outer steel pipe to collect the corrosion potential of the outer steel pipe, wherein the corrosion potential of the outer steel pipe refers to the electrochemical potential value of the outer steel pipe relative to the reference electrode; a fiber optic grating strain sensor is arranged at the interface between the inner steel pipe and the interlayer concrete to collect the temperature strain at the interface between the inner steel pipe and the concrete, wherein the temperature strain at the interface between the inner steel pipe and the concrete refers to the relative deformation between the inner steel pipe and the concrete at the interface caused by temperature changes; a humidity sensor is arranged at the depth inside the interlayer concrete to collect the relative humidity inside the interlayer concrete, wherein the relative humidity inside the interlayer concrete refers to the percentage of water vapor pressure in the concrete pores to the saturated water vapor pressure at the same temperature; Meanwhile, displacement monitoring equipment is installed on the top of the pier to continuously collect time-series data of the pier top displacement. The time-series data of the pier top displacement refers to the sequence of vertical displacement values ​​of the pier top changing over time during its service life. Monitoring data is continuously collected up to the current moment according to the preset time interval.

[0008] Furthermore, based on the corrosion potential of the outer steel pipe, the corrosion activity index of the outer steel pipe is calculated according to the following formula: In the formula, This indicates the corrosion activity index of the outer steel pipe at the current moment; This is the reference corrosion potential of the outer steel pipe in the passivated state; The corrosion potential of the outer steel pipe at the current moment is expressed in units of 1. ; The limiting corrosion potential of the outer steel pipe in a fully activated state is determined by accelerated corrosion testing, and the critical potential value at which general corrosion of the outer steel pipe occurs is obtained through pre-calibration. The unit is 1. ; Based on the temperature strain at the interface between the inner steel pipe and the concrete, the risk factor for peeling at the inner interface is calculated using the following formula: In the formula, This indicates the risk coefficient of inner interface stripping at the current moment; The temperature strain at the interface between the inner steel pipe and the concrete at the current moment is expressed in units of . ; The initial temperature strain reference value is the average value of the interfacial temperature strain under the same temperature conditions and in the initial stage of bridge operation when the interfacial bonding is intact. The unit is 1000 ppm. ; The critical strain threshold for interfacial peeling was determined by interfacial push-out tests, identifying the ultimate strain value at which peeling failure occurs at the interface between the inner steel pipe and the concrete. This value was obtained through pre-calibration and is expressed in units of... .

[0009] Furthermore, the difference between the relative humidity inside the interlayer concrete at the current moment and the preset humidity threshold is calculated as the relative humidity difference at the current moment; Based on the relative humidity difference, the water saturation level of the interlayer concrete at the current moment is determined according to the following water saturation level classification rules. : when At that time, the water saturation level of the interlayer concrete was determined to be Level 1. This refers to a state with low water saturation. when At that time, the water saturation level of the interlayer concrete was determined to be level 2. This refers to a state of moderate water saturation. when At that time, the water saturation level of the interlayer concrete was determined to be level 3. This refers to a state of high water saturation. when At that time, the water saturation level of the interlayer concrete was determined to be level 4. This refers to a supersaturated state. in, This represents the relative humidity difference at the current moment. , These are preset first and second humidity difference thresholds, pre-calibrated based on the characteristics of the concrete pore structure, and satisfying... .

[0010] Furthermore, the expression for the durability state assessment model is as follows: In the formula, This is the overall durability score at the current moment. The initial durability baseline score represents the integrity score of the bridge pier at the initial moment of being put into operation; This indicates the corrosion activity index of the outer steel pipe at the current moment; This indicates the risk coefficient of inner interface stripping at the current moment; This represents the water saturation level of the interlayer concrete at the current moment. , , The preset weights for the corresponding indicators are determined using the Analytic Hierarchy Process (AHP).

[0011] Furthermore, based on the Analytic Hierarchy Process (AHP), determine , and The specific logic behind the weighting of durability in the overall score calculation is as follows: Will be fixed , and Three indicators are labeled, and the relative importance between each pair is determined using the nine-scale method. A judgment matrix is ​​constructed, in which... Marked as 1, Marked as 2, Marked as 3, the constructed judgment matrix is: in, , Both represent indexes of indicators, and , , Indicates that the index is The metrics relative to the index are The importance of the indicators was determined using a 1-9 scale, and... The larger the value, the higher the index. The metrics compared to the index are The greater the importance of the indicator, and , ; Divide each element value in the judgment matrix by the sum of its columns to obtain the normalized judgment matrix. Calculate the mean of the elements in each row of the normalized judgment matrix, and take the mean of the elements in the first row as the normalized judgment matrix. The weights are determined by using the mean of the values ​​in the second row as the basis for the calculation. The weights are determined by using the mean of the values ​​in the third row as the basis for the calculation. The weights are scaled proportionally to the three weights, with the sum of the scaled values ​​equal to 1 as a constraint, and the scaled weights are used as the proportional coefficients of the corresponding indicators.

[0012] Furthermore, starting from the current moment, we trace back continuously... Each monitoring cycle serves as the total backtracking window. The monitoring cycle refers to the basic time unit for sampling the time series data of the pier top displacement. Each monitoring cycle contains multiple sampling points. Within the overall backtracking window, the amplitude of the pier top displacement time series data within each monitoring period is extracted to obtain an amplitude sequence; with a length of The sliding window moves sequentially over the amplitude sequence to calculate the moving average sequence of displacement amplitudes: In the formula, For the first The average displacement amplitude of each sliding window, in units of , For the first The amplitude of the pier top displacement time series data within each monitoring period, in units of ; Index of the sliding window ; For the index of the monitoring period; The length of the sliding window is preset based on the bridge's dynamic characteristics and monitoring frequency. Based on the moving average sequence of displacement amplitudes, the stiffness degradation trend discrimination coefficient is calculated using the following formula: In the formula, The coefficient for judging the stiffness degradation trend at the current moment; The length of the moving average sequence is denoted as . ; For the first The time identifier corresponding to each sliding window is taken as the midpoint of the monitoring period within that window; For all The arithmetic mean; This is the arithmetic mean of the average displacement values ​​across all sliding windows. If satisfied and If the stiffness of the bridge pier is determined to be degraded, then the bridge pier is determined to have a stiffness degradation trend; otherwise, the bridge pier is determined to have no stiffness degradation trend. in, The preset stiffness degradation trend threshold, This is the preset durability rating threshold.

[0013] Furthermore, based on the results of the stiffness degradation trend assessment, the stiffness degradation correction coefficient is determined as follows: If it is determined that the bridge piers exhibit a tendency for stiffness degradation, then the stiffness degradation correction factor... ; If it is determined that the bridge pier does not exhibit a stiffness degradation trend, then the stiffness degradation correction factor... ; in, This is the upper threshold of the stiffness degradation trend discrimination coefficient; The strength coefficient is used to correct for stiffness degradation. ; The stiffness degradation correction coefficient is multiplied by the overall durability score at the current moment, and the product is used as the corrected overall durability score.

[0014] Furthermore, the revised overall durability score is used as the final overall durability score, and compared with the preset durability level threshold to determine the pier durability assessment result at the current moment. The specific logic is as follows: when At that time, the durability assessment result of the bridge pier at the current moment is judged to be excellent; when At that time, the durability assessment result of the bridge pier at the current moment is judged to be good; when At that time, the durability level assessment result of the bridge pier at the current moment is judged to be general; when At that time, the durability assessment result of the bridge pier at the current moment is judged to be poor; in, The final overall durability score; , , The preset first durability level threshold, second durability level threshold, and third durability level threshold are defined, and the following conditions are met: .

[0015] This invention also provides a durability assessment system for prefabricated hollow steel tube concrete bridge piers. This system is used to perform the aforementioned durability assessment method for prefabricated hollow steel tube concrete bridge piers, and includes: The monitoring data acquisition module is used to acquire monitoring data of prefabricated hollow steel tube concrete bridge piers during service. The monitoring data includes corrosion potential of the outer steel tube, temperature and strain at the interface between the inner steel tube and the concrete, relative humidity inside the interlayer concrete, and time series data of pier top displacement. The data processing module is used to calculate the corrosion activity index of the outer steel pipe and the peeling risk coefficient of the inner interface based on the corrosion potential of the outer steel pipe and the temperature strain of the interface between the inner steel pipe and the concrete, and to determine the water saturation level of the interlayer concrete based on the difference between the relative humidity inside the interlayer concrete and the preset humidity threshold. The trend discrimination module is used to construct a durability status assessment model based on the corrosion activity index of the outer steel pipe, the peeling risk coefficient of the inner interface, and the water saturation level of the interlayer concrete. The model is used to determine the comprehensive durability score of the pier at the current moment. Based on the comprehensive durability score and the time-domain characteristics of the pier top displacement time series data, it is determined whether the pier has a stiffness degradation trend. The durability assessment module is used to correct the overall durability score based on the judgment result of stiffness degradation trend, obtain the corrected overall durability score, compare the corrected overall durability score with the preset durability level threshold, and output the durability level assessment result of the pier.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention addresses the unique structural form of prefabricated hollow steel-concrete composite bridge piers by establishing a multi-source monitoring data system encompassing the corrosion activity index of the outer steel pipe, the peeling risk coefficient of the inner interface, and the water saturation level of the sandwich concrete. This system overcomes the shortcomings of existing technologies that only focus on chloride ion erosion in traditional reinforced concrete structures and cannot comprehensively assess the multiple deterioration factors of composite structures, thus achieving a refined characterization of the durability status of this type of bridge pier. Meanwhile, this invention constructs a durability status assessment model, which weights and integrates the corrosion activity index of the outer steel pipe, the peeling risk coefficient of the inner interface, and the water saturation level of the interlayer concrete to obtain a comprehensive durability score, overcoming the shortcomings of the prior art where the assessment indicators are scattered and difficult to comprehensively judge. At the same time, it introduces time-domain feature analysis of pier top displacement time series data to identify the pier stiffness degradation trend and dynamically correct the comprehensive durability score, so that the assessment results can reflect the evolution law of the overall mechanical performance of the structure. Furthermore, this invention compares the revised comprehensive durability score with a preset level threshold and outputs the durability level assessment result of the bridge pier, providing a clear decision-making basis for bridge maintenance and management, and has strong engineering practical value. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall method flow of the present invention; Figure 2 A multi-Y-axis image showing the corrosion activity index of the outer steel pipe, the peeling risk coefficient of the inner interface, the water saturation level of the interlayer concrete, and the comprehensive durability score. Figure 3 This is a schematic diagram of the overall system modules of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0019] 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.

[0020] Example: Please see Figure 1-2 The present invention provides a technical solution: A method for evaluating the durability of prefabricated hollow-core steel-concrete composite bridge piers, comprising the following steps: Step 1: Obtain monitoring data of the prefabricated hollow steel tube concrete bridge pier during its service life. The monitoring data includes corrosion potential of the outer steel tube, temperature and strain at the interface between the inner steel tube and the concrete, relative humidity inside the sandwich concrete, and time series data of pier top displacement. In this embodiment, the specific logic for acquiring monitoring data is as follows: A corrosion potential sensor is arranged on the outer wall of the outer steel pipe to collect the corrosion potential of the outer steel pipe. The corrosion potential of the outer steel pipe refers to the electrochemical potential value of the outer steel pipe relative to the reference electrode, which is used to characterize the degree of electrochemical corrosion activity on the surface of the steel pipe. The larger the negative shift of the potential, the more significant the corrosion tendency. A fiber optic strain sensor is arranged at the interface between the inner steel pipe and the interlayer concrete to collect the temperature strain at the interface between the inner steel pipe and the concrete. The temperature strain at the interface between the inner steel pipe and the concrete refers to the relative deformation between the inner steel pipe and the concrete at the interface caused by temperature changes, which is used to characterize the change in the bonding state of the interface between the two. An abnormal increase in strain indicates that there is a risk of delamination at the interface. A humidity sensor is arranged at the depth inside the interlayer concrete to collect the relative humidity inside the interlayer concrete. The relative humidity inside the interlayer concrete refers to the percentage of water vapor pressure in the concrete pores to the saturated water vapor pressure at the same temperature, which is used to characterize the degree of water saturation inside the concrete. The higher the humidity, the more serious the water penetration. The temperature strain at the interface between the inner steel pipe and the concrete specifically refers to the strain data collected under conditions where there is no external load or the external load is basically constant. In this embodiment, the data is collected during a period of low traffic flow at night. At this time, the external forces such as vehicle load and wind load on the structure can be ignored. The strain change at the interface is mainly due to the relative deformation caused by the difference in the thermal expansion coefficients of the steel pipe and the concrete material caused by the change in ambient temperature. Therefore, it is defined as temperature strain.

[0021] Meanwhile, displacement monitoring equipment is installed on the top of the pier to continuously collect time-series data of the pier top displacement. The time-series data of the pier top displacement refers to the sequence of vertical displacement values ​​of the pier top changing over time during its service life. It is used to characterize the deformation response of the pier under external loads. The gradual trend of the displacement values ​​reflects the degree of degradation of the overall stiffness of the pier. In this embodiment, a differentiated multi-point deployment strategy was adopted for different monitoring data when deploying sensors. Specifically, for the corrosion potential of the outer steel pipe, multiple corrosion potential sensors were uniformly arranged circumferentially along the outer wall of the steel pipe to capture the differences in corrosion activity in different directions. For the temperature strain at the interface between the inner steel pipe and the concrete, multiple fiber optic strain sensors were uniformly arranged circumferentially at the interface to monitor the circumferential distribution characteristics of the interface bonding state. For the relative humidity inside the interlayer concrete, multiple humidity sensors were arranged at different depths radially inside the concrete to obtain the depth gradient information of water penetration. For the time series data of the pier top displacement, a high-precision displacement monitoring device was arranged at the pier top for continuous acquisition. Based on the multi-point deployment, monitoring data was continuously collected up to the current moment according to a preset time interval, and the arithmetic mean of the collected values ​​from multiple measurement points of various sensors was used as the monitoring data value of the entire pier, effectively eliminating the influence of local measurement errors and spatial non-uniformity on the evaluation results.

[0022] Step 1 of this invention achieves comprehensive monitoring of multi-dimensional durability indicators of prefabricated hollow steel-concrete composite bridge piers by arranging corrosion potential sensors on the outer wall of the outer steel pipe, fiber optic strain sensors at the interface between the inner steel pipe and the concrete, humidity sensors at different depths inside the sandwich concrete, and displacement monitoring equipment on the pier top. It collects local state parameters such as corrosion potential of the outer steel pipe, interface temperature and strain, and internal relative humidity at the current moment, and continuously collects time-series data of vertical displacement of the pier top over time during service. This forms a multi-source monitoring system from local material deterioration to overall structural deformation, providing a comprehensive and accurate data foundation for subsequent durability assessment. It overcomes the shortcomings of existing technologies that only focus on a single deterioration factor and cannot fully reflect the complex deterioration characteristics of composite structures.

[0023] Step 2: Based on the corrosion potential of the outer steel pipe and the temperature strain at the interface between the inner steel pipe and the concrete, calculate the corrosion activity index of the outer steel pipe and the peeling risk coefficient of the inner interface, and determine the water saturation level of the interlayer concrete based on the difference between the relative humidity inside the interlayer concrete and the preset humidity threshold. In this embodiment, based on the corrosion potential of the outer steel pipe, the corrosion activity index of the outer steel pipe is calculated according to the following formula: In the formula, This indicates the corrosion activity index of the outer steel pipe at the current moment; The reference corrosion potential of the outer steel pipe in the passivated state was obtained through pre-calibration by referring to electrochemical test data of steel pipes of the same material in simulated pore fluid. The unit is 1. ; The corrosion potential of the outer steel pipe at the current moment is expressed in units of 1. ; The limiting corrosion potential of the outer steel pipe in a fully activated state is determined by accelerated corrosion testing, and the critical potential value at which general corrosion of the outer steel pipe occurs is obtained through pre-calibration. The unit is 1. ; For this formula, the corrosion activity index of the outer steel pipe Used to characterize the degree of electrochemical corrosion activity on the surface of the outer steel pipe at the current moment, that is, whether the steel pipe is in a passivated or activated state. The value ranges from 0 to 1. A higher value indicates stronger corrosion activity of the outer steel pipe and a higher risk of corrosion. Specifically, when... When the potential is close to 0, it indicates that the current corrosion potential is close to the reference potential, the steel pipe surface is in a passivated state, and the tendency to corrode is extremely low; when... When the value is close to 1, it indicates that the current corrosion potential is close to the limit corrosion potential, the surface of the steel pipe is in a fully activated state, the corrosion tendency is extremely high, and total corrosion has occurred or is about to occur.

[0024] Corrosion potential of outer steel pipe The corrosion potential is a core parameter characterizing the electrochemical state of a steel pipe surface. Its changes directly reflect the electrochemical reaction activity between the steel pipe and the surrounding environment. In the principle of electrochemical corrosion, the more negative the corrosion potential, the greater the tendency of the steel pipe surface to lose electrons, that is, the more intense the oxidation-dissolution reaction and the stronger the corrosion activity; conversely, the more positive the corrosion potential, the more the steel pipe surface is in a passivation film protection state, and the weaker the corrosion activity. Therefore, when... When a negative shift (numerical decrease) occurs, the molecule Enlargement, leading to An increase in the value indicates that the passivation film on the steel pipe surface is damaged and the corrosion activity is enhanced; when When the value shifts positively (increases), the molecule decreases. A decrease in the value indicates that the passivation film on the steel pipe surface has been repaired or remains intact, and the corrosion activity has been reduced.

[0025] This formula employs a linear normalization structure, mapping corrosion potential values ​​with different dimensions and magnitudes to a unified range of 0-1, thus ensuring that the corrosion activity index has clear physical boundaries and comparability. Secondly, the formula uses the passivation state as a reference potential. and the limit potential of the fully activated state As upper and lower limit benchmarks, it covers the entire state space of the steel pipe from complete passivation to full corrosion, so that the calculation results can accurately reflect the relative position of the current corrosion state in the whole deterioration process.

[0026] Based on the temperature strain at the interface between the inner steel pipe and the concrete, the risk factor for peeling at the inner interface is calculated using the following formula: In the formula, This indicates the risk coefficient of inner interface stripping at the current moment; The temperature strain at the interface between the inner steel pipe and the concrete at the current moment is taken as the temperature strain at the interface between the inner steel pipe and the concrete most recently measured during the nighttime data collection period. The value of is in units of ; The initial temperature strain reference value is the average value of the interfacial temperature strain under the same temperature conditions and in the initial stage of bridge operation when the interfacial bonding is intact. The unit is 1000 ppm. ; The critical strain threshold for interfacial peeling was determined by interfacial push-out tests, identifying the ultimate strain value at which peeling failure occurs at the interface between the inner steel pipe and the concrete. This value was obtained through pre-calibration and is expressed in units of... .

[0027] For this formula, It is used to characterize the degree of deterioration of the bonding state at the interface between the inner steel pipe and the interlayer concrete at the current moment, that is, the risk of interface peeling. The value of is a non-negative real number; the larger the value, the more severe the deterioration of the interfacial adhesion state and the higher the risk of peeling. Specifically, when When the temperature is close to 0, it indicates that the current interface temperature strain is close to the initial reference value, the interface adhesion is good, and there are no obvious signs of peeling; when As the value gradually increases, it indicates that the degree of deviation of the interfacial strain from the initial state intensifies, suggesting that microcracks or local debonding may occur at the interface; when When the value is close to or exceeds 1, it indicates that the interfacial strain has reached or exceeded the critical peel strain threshold, indicating that peel failure has occurred or is about to occur at the interface.

[0028] Temperature strain difference at the interface between the inner steel pipe and the concrete This reflects the degree of deviation of the current interfacial strain from its initial intact state, and its change directly reveals the evolution process of the interfacial bonding state. In the actual physical mechanism, due to the different thermal expansion coefficients of the inner steel pipe and concrete, relative deformation will occur under the action of temperature changes. When the interfacial bonding is intact, this relative deformation is constrained by the interfacial bonding force, and the strain is within a stable range. With the extension of service time, the interface gradually deteriorates under the action of fatigue load, temperature cycling, moisture erosion and other factors, the bonding force decreases, and the relative deformation at the interface increases, thus increasing the measured strain. Deviation from initial reference value Therefore, when An increase in the relative slippage indicates a degradation in interfacial adhesion and aggravation of relative slippage, directly leading to... An increase in the value reflects an increased risk of divestiture; when When the value decreases, it indicates that the interfacial strain is near the baseline value, and the bonding state is relatively stable. The value decreases.

[0029] The formula uses the absolute value of the relative deviation to quantify the degree of deviation of the interfacial strain from its initial intact state. This objectively reflects the extent of degradation of the interfacial adhesion performance and avoids interference from fluctuations in the absolute value of strain caused by temperature changes. Secondly, the formula uses the critical strain threshold for interfacial peeling. As a normalization benchmark, it gives the calculation results a clear physical meaning, when This indicates that the interfacial strain has reached the critical delamination state. This indicates that the critical value has been exceeded. This design directly links the stripping risk coefficient to the limit state of interface failure. The formula has a simple structure and clear physical meaning. It quantifies the stripping risk by comparing the relative deviation between the current strain and the initial reference value.

[0030] Calculate the difference between the current relative humidity inside the interlayer concrete and the preset humidity threshold, and use it as the relative humidity difference at the current moment; Based on the relative humidity difference, the water saturation level of the interlayer concrete at the current moment is determined according to the following water saturation level classification rules. : when At that time, the water saturation level of the interlayer concrete was determined to be Level 1. This refers to a state with low water saturation. when At that time, the water saturation level of the interlayer concrete was determined to be level 2. This refers to a state of moderate water saturation. when At that time, the water saturation level of the interlayer concrete was determined to be level 3. This refers to a state of high water saturation. when At that time, the water saturation level of the interlayer concrete was determined to be level 4. This refers to a supersaturated state. in, This represents the relative humidity difference at the current moment. , These are preset first and second humidity difference thresholds, pre-calibrated based on the characteristics of the concrete pore structure, and satisfying... .

[0031] By calculating the difference between the relative humidity inside the interlayer concrete at the current moment and a preset humidity threshold, and classifying the water saturation level according to the different intervals in which this difference falls, a graded assessment of the water permeability state inside the interlayer concrete is achieved. This fully considers the continuous evolution of pore water in the concrete from gaseous to liquid states, and from unsaturated to supersaturated states. A negative difference indicates that the humidity is below the critical threshold, the water exists in the form of water vapor, and the permeation risk is low. A positive difference indicates that the humidity exceeds the critical threshold, pore water is interconnected, forming liquid water channels, and the permeation risk is significantly increased. In this embodiment, based on the characteristics of the concrete pore structure, [the following is not specified in the original text]. Set the critical humidity difference threshold at which continuous water channels begin to form in the capillaries of concrete. The critical humidity difference threshold for concrete pore water to reach full saturation is set by establishing two levels of humidity difference thresholds. and The system scientifically classifies moisture state into four levels: low water saturation, medium water saturation, high water saturation, and supersaturation. This provides a quantitative input that reflects the progressive law of moisture penetration risk for subsequent comprehensive durability scoring, overcoming the shortcomings of existing technologies that simply judge humidity levels and cannot distinguish the form of moisture and its different degrees of influence on durability.

[0032] Step 3: Construct a durability status assessment model based on the corrosion activity index of the outer steel pipe, the peeling risk coefficient of the inner interface, and the water saturation level of the interlayer concrete. Use the model to determine the comprehensive durability score of the pier at the current moment. Based on the comprehensive durability score and the time-domain characteristics of the pier top displacement time series data, determine whether the pier has a stiffness degradation trend. In this embodiment, the expression of the durability state assessment model is as follows: In the formula, This is the overall durability score at the current moment. The initial durability baseline score represents the integrity score of the bridge pier at the initial moment of being put into operation; This indicates the corrosion activity index of the outer steel pipe at the current moment; This indicates the risk coefficient of inner interface stripping at the current moment; This represents the water saturation level of the interlayer concrete at the current moment. , , The preset weights for the corresponding indicators are determined using the Analytic Hierarchy Process (AHP).

[0033] Overall durability score Used to characterize the overall durability status of prefabricated hollow-core steel-concrete composite bridge piers at the current moment, that is, the comprehensive level at which the pier maintains its design performance and service capability under the combined effect of multiple deterioration factors. The value range is from 0 to Between these ranges, the larger the value, the better the durability of the bridge piers and the higher their overall health; specifically, when... near At this time, it indicates that the outer steel pipe is well passivated, the interface is firmly bonded, and the internal moisture penetration of the concrete is slight, meaning the bridge pier is in a near-initial, intact durability state; when When the value gradually decreases, it indicates that the cumulative effect of various deterioration indicators is increasing, and the durability of the bridge pier is gradually deteriorating; when When the value approaches 0, it indicates that the bridge pier has suffered serious durability damage and is approaching or has reached a failure state.

[0034] Corrosion activity index of outer steel pipe Risk factor of inner layer interface peeling and the water saturation grade value of interlayer concrete The degree of durability degradation of bridge piers is characterized by different physical mechanisms, and these three factors together determine the overall durability status of the bridge piers. An increase in the thickness of the outer steel pipe surface means damage to the passivation film and enhanced electrochemical corrosion activity, which leads to a reduction in the effective cross-section of the steel pipe and a decrease in its mechanical properties, thereby... Decrease; The increase in this value implies a degradation of the bond performance between the inner steel pipe and the concrete interface, and an intensification of relative slippage. This leads to a weakening of the combined effect and a reduction in load transfer efficiency, thereby... Decrease; The increase in [amount] means that the infiltration of water into the interlayer concrete is intensified, and the interconnection of pore water forms liquid phase channels, which will accelerate the corrosion of steel pipes and the deterioration of concrete, thereby [causing further damage]. These three indicators comprehensively reflect the process of durability deterioration of bridge piers from three dimensions: material corrosion, interface damage, and environmental erosion. The deterioration of any one of these indicators will have a negative impact on overall durability.

[0035] This formula employs a linear weighted summation structure, integrating three degradation indicators with clearly defined physical meanings. This allows for a comprehensive reflection of the multiple degradation mechanisms affecting prefabricated hollow-core steel-concrete composite bridge piers, from material corrosion and interface damage to environmental erosion. Furthermore, the formula uses an initial durability benchmark score. The current score is calculated by subtracting the weighted sum from 1, with the upper limit set. The score is calculated when all degradation indicators are 0. When each degradation index reaches its maximum value, the score approaches 0; third, the formula uses weighting coefficients. , , It enables differentiated expression of the importance of different degradation indicators, and can reasonably allocate the contribution of each indicator based on engineering practice and expert experience.

[0036] Table 1: Statistical Table of Overall Durability Score In this embodiment, 15 representative sets of bridge pier durability monitoring data were selected, and the following graphs were plotted: Figure 2 The image shows a multi-Y-axis graph of the corrosion activity index of the outer steel pipe, the peeling risk coefficient of the inner interface, the water saturation level of the interlayer concrete, and the comprehensive durability score; combined with... Figure 2It can be clearly seen that as the corrosion activity index of the outer steel pipe, the peeling risk coefficient of the inner interface, and the water saturation level of the interlayer concrete show a continuous upward trend, the overall durability score of the bridge pier shows a monotonically decreasing trend, gradually decreasing from the initial 98.2 points to 15.5 points. This change pattern fully verifies the rationality and effectiveness of the durability status assessment model. That is, when the corrosion activity of the outer steel pipe increases, the peeling risk of the inner interface rises, and the water saturation level of the interlayer concrete increases, the overall durability score of the bridge pier decreases accordingly. The negative impacts of the three factors on durability show a clear cumulative effect. The curves of the corrosion activity index of the outer steel pipe and the peeling risk coefficient of the inner interface in the image are basically synchronized but slightly different, reflecting the correlation and independence of the two deterioration mechanisms. The stepwise increase of the water saturation level of the interlayer concrete contrasts sharply with the smooth decrease of the overall durability score, intuitively demonstrating the mapping relationship between discrete indicators and continuous scores, providing reliable data support for subsequent stiffness degradation trend judgment and durability level classification.

[0037] Determined based on the analytic hierarchy process , and The specific logic behind the weighting of durability in the overall score calculation is as follows: Will be fixed , and Three indicators are labeled, and the relative importance between each pair is determined using the nine-scale method. A judgment matrix is ​​constructed, in which... Marked as 1, Marked as 2, Marked as 3, the constructed judgment matrix is: in, , Both represent indexes of indicators, and , , Indicates that the index is The metrics relative to the index are The importance of the indicators was determined using a 1-9 scale, and... The larger the value, the higher the index. The metrics compared to the index are The greater the importance of the indicator, and , ; Divide each element value in the judgment matrix by the sum of its columns to obtain the normalized judgment matrix. Calculate the mean of the elements in each row of the normalized judgment matrix, and take the mean of the elements in the first row as the normalized judgment matrix. The weights are determined by using the mean of the values ​​in the second row as the basis for the calculation. The weights are determined by using the mean of the values ​​in the third row as the basis for the calculation. The weights are scaled proportionally to the three weights, with the sum of the scaled values ​​equal to 1 as a constraint, and the scaled weights are used as the proportional coefficients of the corresponding indicators.

[0038] Starting from the current moment, backtrack continuously. Each monitoring cycle serves as the total backtracking window. The monitoring cycle refers to the basic time unit for sampling the time series data of the pier top displacement. Each monitoring cycle contains multiple sampling points. Within the overall backtracking window, the amplitude of the pier top displacement time series data within each monitoring period is extracted to obtain an amplitude sequence; with a length of The sliding window moves sequentially over the amplitude sequence to calculate the moving average sequence of displacement amplitudes: In the formula, For the first The average displacement amplitude of each sliding window, in units of , For the first The amplitude of the pier top displacement time series data within each monitoring period, in units of ; Index of the sliding window ; For the index of the monitoring period; The length of the sliding window is preset based on the bridge's dynamic characteristics and monitoring frequency. Based on the moving average sequence of displacement amplitudes, the stiffness degradation trend discrimination coefficient is calculated using the following formula: In the formula, The coefficient for judging the stiffness degradation trend at the current moment; The length of the moving average sequence is denoted as . ; For the first The time identifier corresponding to each sliding window is taken as the midpoint of the monitoring period within that window; For all The arithmetic mean; This is the arithmetic mean of the average displacement values ​​across all sliding windows. If satisfied and If the stiffness of the bridge pier is determined to be degraded, then the bridge pier is determined to have a stiffness degradation trend; otherwise, the bridge pier is determined to have no stiffness degradation trend. in, The threshold for stiffness degradation trend is set based on the statistical patterns of historical monitoring data of similar bridges under normal service conditions. The preset durability score threshold is pre-set based on bridge design specifications, safety level requirements, and durability assessment experience.

[0039] This is used to characterize the rate of change of the overall stiffness of the bridge pier over time at the current moment, that is, the slope of the linear trend of the pier top displacement amplitude within the total backtracking window. Its magnitude and sign reflect the direction and degree of stiffness degradation; specifically, when... When the value is positive and large, it indicates a significant increasing trend in displacement amplitude, suggesting that the pier stiffness is degrading at an accelerated rate; when... When the value is positive but small, it indicates that the displacement amplitude is increasing slowly and the stiffness is showing a slight degradation trend; when... When the value is close to 0, it indicates that the displacement amplitude has no obvious trend change, and the stiffness is relatively stable; when... When the value is negative, it indicates that the displacement amplitude is decreasing. This situation is relatively rare in actual engineering and may be caused by structural repair or changes in environmental conditions.

[0040] and These represent the deviations of the time variable and the displacement amplitude variable from their mean values, respectively. Their coordinated changes jointly determine the coefficient for judging the stiffness degradation trend. Size and orientation; in molecules In this context, when the displacement amplitude of earlier windows is lower than the mean and the displacement amplitude of later windows is higher than the mean, meaning the displacement amplitude increases over time, then... and The sign of the product terms is negative at the beginning and positive at the end on the time axis. The sum of the positive and negative signs of the product terms makes the numerator positive; conversely, if the displacement amplitude decreases over time, the numerator is negative; the denominator... Represents the dispersion of a time variable; the larger the value, the longer the time span or the more dispersed the time distribution. It represents the slope of the trend calculated for the same amount of displacement change. The smaller the value, the more it reflects the normalization of the time scale in the trend judgment; therefore, the numerator reflects the covariant relationship between displacement amplitude and time change, while the denominator normalizes the time dispersion. The combined effect of these two factors makes... It can objectively quantify the linear rate of change of displacement amplitude over time.

[0041] This formula uses the least squares linear regression slope calculation formula, which is a standard method in statistics for quantifying the linear relationship between variables. It has a rigorous mathematical theoretical foundation and has been widely verified through applications. Secondly, the formula uses a moving average sequence... As input, it effectively eliminates the interference of short-term random fluctuations and measurement noise on trend judgment, making the calculation results more reflective of the true evolution law of structural stiffness; third, the formula achieves unbiased estimation of the displacement amplitude change trend through the covariance term in the numerator and the variance term in the denominator, and the calculation results It can intuitively reflect the rate of stiffness degradation; in addition, the formula does not depend on the absolute magnitude of the displacement amplitude, but only on its relative change trend, avoiding the interference of the difference in absolute displacement value under different bridges and different load conditions on the trend judgment, and has strong universality and engineering applicability.

[0042] In step 3, starting from the current time, backtrack continuously. The monitoring period serves as the overall backtracking window. Each monitoring period contains multiple displacement sampling points. First, the amplitude of the pier top displacement time series data within each monitoring period is extracted to form an amplitude sequence. Then, the amplitudes are arranged in a sequence with a length of [missing information]. A sliding window is sequentially slid across the amplitude sequence, and the average displacement amplitude within each window is calculated to obtain a moving average sequence. This sequence effectively eliminates the interference of short-term random fluctuations on the displacement data and reveals the evolution law of displacement amplitude over time. Based on the moving average sequence and its corresponding time marker, a stiffness degradation trend discrimination coefficient is obtained using a linear regression slope calculation formula. This coefficient quantifies the rate of change of displacement amplitude over time; a positive value indicates that the displacement amplitude is increasing. Greater than the preset stiffness degradation trend threshold And the current overall durability score Less than the preset durability score threshold If the bridge pier is found to have a stiffness degradation trend, it indicates that the overall stiffness of the structure has significantly decreased; otherwise, it is determined that there is no stiffness degradation trend. This step, by introducing time-domain feature analysis of the displacement time series data of the pier top, enables the identification of stiffness degradation trend from the overall deformation response of the structure, so that the durability assessment results can reflect the evolution law of the structural mechanical performance, and overcomes the defect of existing technology that only focuses on local material deterioration and cannot perceive the overall performance degradation.

[0043] Step 4: Correct the overall durability score based on the determination result of stiffness degradation trend to obtain the corrected overall durability score. Compare the corrected overall durability score with the preset durability level threshold and output the durability level evaluation result of the pier. In this embodiment, the stiffness degradation correction coefficient is determined based on the determination result of the stiffness degradation trend, specifically as follows: If it is determined that the bridge piers exhibit a tendency for stiffness degradation, then the stiffness degradation correction factor... ; If it is determined that the bridge pier does not exhibit a stiffness degradation trend, then the stiffness degradation correction factor... ; in, This is the upper threshold of the stiffness degradation trend discrimination coefficient; The strength coefficient is used to correct for stiffness degradation. The requirements are pre-set based on the bridge's importance level and design safety reserve requirements; The stiffness degradation correction coefficient is multiplied by the overall durability score at the current moment, and the product is used as the corrected overall durability score.

[0044] When a bridge pier is determined to exhibit a stiffness degradation trend, it indicates a significant decrease in the overall structural stiffness. This necessitates a reduction in the original comprehensive durability score to reflect this adverse effect. The reduction amount is determined by the stiffness degradation trend discrimination coefficient. Relative to its upper limit threshold The ratio and Joint decision, The larger the value, the more severe the stiffness degradation and the greater the reduction. When it is determined that there is no stiffness degradation trend in the pier, it indicates that the overall stiffness of the structure is relatively stable and no reduction is required. The correction factor is 1. The correction factor is multiplied by the overall durability score at the current moment to obtain the corrected overall durability score, so that the evaluation results can truly reflect the evolution law of the overall mechanical performance of the structure.

[0045] The revised overall durability score is used as the final overall durability score, and it is compared with the preset durability level threshold to determine the pier durability assessment result at the current moment. The specific logic is as follows: when At that time, the durability assessment result of the bridge pier at the current moment is judged to be excellent; when At that time, the durability assessment result of the bridge pier at the current moment is judged to be good; when At that time, the durability level assessment result of the bridge pier at the current moment is judged to be general; when At that time, the durability assessment result of the bridge pier at the current moment is judged to be poor; in, The final overall durability score; , , The preset first durability level threshold, second durability level threshold, and third durability level threshold are defined, and the following conditions are met: ; , , The determination method is as follows: based on bridge design specifications, safety level requirements and historical assessment experience, the comprehensive durability score is divided into four intervals from high to low, corresponding to four durability levels: excellent, good, average and poor.

[0046] Step 4 of this invention dynamically corrects the comprehensive durability score based on the stiffness degradation trend judgment result, and outputs the pier durability level assessment result based on the comparison between the corrected score and the preset level threshold. This achieves a fusion assessment from local material deterioration indicators to overall structural mechanical performance. When a stiffness degradation trend is determined, the comprehensive score is reduced accordingly based on the degree of stiffness degradation, so that the assessment result can truly reflect the adverse effects of overall structural stiffness reduction on durability. This overcomes the shortcomings of existing technologies that only focus on local deterioration indicators and cannot perceive overall performance degradation. At the same time, by comparing the corrected comprehensive score with the four level thresholds of excellent, good, average, and poor, a clear durability level assessment result is output, providing an intuitive and quantitative decision-making basis for bridge maintenance management, and facilitating maintenance personnel to take targeted maintenance measures according to different durability levels.

[0047] Please see Figure 3 The present invention also provides a durability assessment system for prefabricated hollow-core steel-concrete composite bridge piers, comprising: The monitoring data acquisition module is used to acquire monitoring data of prefabricated hollow steel tube concrete bridge piers during service. The monitoring data includes corrosion potential of the outer steel tube, temperature and strain at the interface between the inner steel tube and the concrete, relative humidity inside the interlayer concrete, and time series data of pier top displacement. The data processing module is used to calculate the corrosion activity index of the outer steel pipe and the peeling risk coefficient of the inner interface based on the corrosion potential of the outer steel pipe and the temperature strain of the interface between the inner steel pipe and the concrete, and to determine the water saturation level of the interlayer concrete based on the difference between the relative humidity inside the interlayer concrete and the preset humidity threshold. The trend discrimination module is used to construct a durability status assessment model based on the corrosion activity index of the outer steel pipe, the peeling risk coefficient of the inner interface, and the water saturation level of the interlayer concrete. The model is used to determine the comprehensive durability score of the pier at the current moment. Based on the comprehensive durability score and the time-domain characteristics of the pier top displacement time series data, it is determined whether the pier has a stiffness degradation trend. The durability assessment module is used to correct the overall durability score based on the judgment result of stiffness degradation trend, obtain the corrected overall durability score, compare the corrected overall durability score with the preset durability level threshold, and output the durability level assessment result of the pier.

[0048] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0049] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0050] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0051] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for evaluating the durability of prefabricated hollow-core steel-concrete composite bridge piers, characterized in that, The specific steps include: Step 1: Obtain monitoring data of the prefabricated hollow steel tube concrete bridge pier during its service life. The monitoring data includes corrosion potential of the outer steel tube, temperature and strain at the interface between the inner steel tube and the concrete, relative humidity inside the sandwich concrete, and time series data of pier top displacement. Step 2: Based on the corrosion potential of the outer steel pipe and the temperature strain at the interface between the inner steel pipe and the concrete, calculate the corrosion activity index of the outer steel pipe and the peeling risk coefficient of the inner interface, and determine the water saturation level of the interlayer concrete based on the difference between the relative humidity inside the interlayer concrete and the preset humidity threshold. Step 3: Construct a durability status assessment model based on the corrosion activity index of the outer steel pipe, the peeling risk coefficient of the inner interface, and the water saturation level of the interlayer concrete. Use the model to determine the comprehensive durability score of the pier at the current moment. Based on the comprehensive durability score and the time-domain characteristics of the pier top displacement time series data, determine whether the pier has a stiffness degradation trend. Step 4: Correct the overall durability score based on the determination result of stiffness degradation trend to obtain the corrected overall durability score. Compare the corrected overall durability score with the preset durability level threshold and output the durability level evaluation result of the pier.

2. The method for evaluating the durability of prefabricated hollow-core steel-concrete composite bridge piers according to claim 1, characterized in that: The specific logic for acquiring monitoring data is as follows: A corrosion potential sensor is arranged on the outer wall of the outer steel pipe to collect the corrosion potential of the outer steel pipe, which refers to the electrochemical potential value of the outer steel pipe relative to the reference electrode; a fiber optic grating strain sensor is arranged at the interface between the inner steel pipe and the interlayer concrete to collect the temperature strain at the interface between the inner steel pipe and the concrete, which refers to the relative deformation between the inner steel pipe and the concrete at the interface caused by temperature changes; a humidity sensor is arranged at the depth inside the interlayer concrete to collect the relative humidity inside the interlayer concrete, which refers to the percentage of water vapor pressure in the concrete pores to the saturated water vapor pressure at the same temperature. Meanwhile, displacement monitoring equipment is installed on the top of the pier to continuously collect time-series data of the pier top displacement. The time-series data of the pier top displacement refers to the sequence of vertical displacement values ​​of the pier top changing over time during its service life. Monitoring data is continuously collected up to the current moment according to the preset time interval.

3. The method for evaluating the durability of prefabricated hollow-core steel-concrete composite bridge piers according to claim 2, characterized in that: Based on the corrosion potential of the outer steel pipe, the corrosion activity index of the outer steel pipe is calculated according to the following formula: In the formula, This indicates the corrosion activity index of the outer steel pipe at the current moment; This is the reference corrosion potential of the outer steel pipe in the passivated state; The corrosion potential of the outer steel pipe at the current moment is expressed in units of 1. ; The limiting corrosion potential of the outer steel pipe in a fully activated state is determined by accelerated corrosion testing, and the critical potential value at which general corrosion of the outer steel pipe occurs is obtained through pre-calibration. The unit is 1. ; Based on the temperature strain at the interface between the inner steel pipe and the concrete, the risk factor for peeling at the inner interface is calculated using the following formula: In the formula, This indicates the risk coefficient of inner interface stripping at the current moment; The temperature strain at the interface between the inner steel pipe and the concrete at the current moment is expressed in units of . ; The initial temperature strain reference value is the average value of the interfacial temperature strain under the same temperature conditions and in the initial stage of bridge operation when the interfacial bonding is intact. The unit is 1000 ppm. ; The critical strain threshold for interfacial peeling was determined by interfacial push-out tests, identifying the ultimate strain value at which peeling failure occurs at the interface between the inner steel pipe and the concrete. This value was obtained through pre-calibration and is expressed in units of... .

4. The method for evaluating the durability of prefabricated hollow-core steel-concrete composite bridge piers according to claim 1, characterized in that: Calculate the difference between the current relative humidity inside the interlayer concrete and the preset humidity threshold, and use it as the relative humidity difference at the current moment; Based on the relative humidity difference, the water saturation level of the interlayer concrete at the current moment is determined according to the following water saturation level classification rules. : when At that time, the water saturation level of the interlayer concrete was determined to be Level 1. This refers to a state with low water saturation. when At that time, the water saturation level of the interlayer concrete was determined to be level 2. This refers to a state of moderate water saturation. when At that time, the water saturation level of the interlayer concrete was determined to be level 3. This refers to a state of high water saturation. when At that time, the water saturation level of the interlayer concrete was determined to be level 4. This refers to a supersaturated state. in, This represents the relative humidity difference at the current moment. , These are preset first and second humidity difference thresholds, pre-calibrated based on the characteristics of the concrete pore structure, and satisfying... .

5. The method for evaluating the durability of prefabricated hollow-core steel-concrete composite bridge piers according to claim 1, characterized in that: The expression for the durability condition assessment model is as follows: In the formula, This is the overall durability score at the current moment. The initial durability baseline score represents the integrity score of the bridge pier at the initial moment of being put into operation; This indicates the corrosion activity index of the outer steel pipe at the current moment; This indicates the risk coefficient of inner interface stripping at the current moment; This represents the water saturation level of the interlayer concrete at the current moment. , , The preset weights for the corresponding indicators are determined using the Analytic Hierarchy Process (AHP).

6. The method for evaluating the durability of prefabricated hollow-core steel-concrete composite bridge piers according to claim 5, characterized in that: Determined based on the analytic hierarchy process , and The specific logic behind the weighting of durability in the overall score calculation is as follows: Will be fixed , and Three indicators are labeled, and the relative importance between each pair is determined using the nine-scale method. A judgment matrix is ​​constructed, in which... Marked as 1, Marked as 2, Marked as 3, the constructed judgment matrix is: in, , Both represent indexes of indicators, and , , Indicates that the index is The metrics relative to the index are The importance of the indicators was determined using a 1-9 scale, and... The larger the value, the higher the index. The metrics compared to the index are The greater the importance of the indicator, and , ; Divide each element value in the judgment matrix by the sum of its columns to obtain the normalized judgment matrix. Calculate the mean of the elements in each row of the normalized judgment matrix, and take the mean of the elements in the first row as the normalized judgment matrix. The weights are determined by using the mean of the values ​​in the second row as the basis for the calculation. The weights are determined by using the mean of the values ​​in the third row as the basis for the calculation. The weights are scaled proportionally to the three weights, with the sum of the scaled values ​​equal to 1 as a constraint, and the scaled weights are used as the proportional coefficients of the corresponding indicators.

7. The method for evaluating the durability of prefabricated hollow-core steel-concrete composite bridge piers according to claim 5, characterized in that: Starting from the current moment, backtrack continuously. Each monitoring cycle serves as the total backtracking window. The monitoring cycle refers to the basic time unit for sampling the time series data of the pier top displacement. Each monitoring cycle contains multiple sampling points. Within the overall backtracking window, the amplitude of the pier top displacement time series data within each monitoring period is extracted to obtain an amplitude sequence; with a length of The sliding window moves sequentially over the amplitude sequence to calculate the moving average sequence of displacement amplitudes: In the formula, For the first The average displacement amplitude of each sliding window, in units of , For the first The amplitude of the pier top displacement time series data within each monitoring period, in units of ; Index of the sliding window ; For the index of the monitoring period; The length of the sliding window is preset based on the bridge's dynamic characteristics and monitoring frequency. Based on the moving average sequence of displacement amplitudes, the stiffness degradation trend discrimination coefficient is calculated using the following formula: In the formula, The coefficient for judging the stiffness degradation trend at the current moment; The length of the moving average sequence is denoted as . ; For the first The time identifier corresponding to each sliding window is taken as the midpoint of the monitoring period within that window; For all The arithmetic mean; This is the arithmetic mean of the average displacement values ​​across all sliding windows. If satisfied and If so, it is determined that the bridge pier has a tendency to degrade stiffness; Otherwise, it is determined that the bridge piers do not exhibit a trend of stiffness degradation; in, The preset stiffness degradation trend threshold, This is the preset durability rating threshold.

8. The method for evaluating the durability of prefabricated hollow-core steel-concrete composite bridge piers according to claim 7, characterized in that: Based on the results of the stiffness degradation trend assessment, the stiffness degradation correction coefficient is determined as follows: If it is determined that the bridge piers exhibit a tendency for stiffness degradation, then the stiffness degradation correction factor... ; If it is determined that the bridge pier does not exhibit a stiffness degradation trend, then the stiffness degradation correction factor... ; in, This is the upper threshold of the stiffness degradation trend discrimination coefficient; The strength coefficient is used to correct for stiffness degradation. ; The stiffness degradation correction coefficient is multiplied by the overall durability score at the current moment, and the product is used as the corrected overall durability score.

9. The method for evaluating the durability of prefabricated hollow-core steel-concrete composite bridge piers according to claim 8, characterized in that: The revised overall durability score is used as the final overall durability score, and it is compared with the preset durability level threshold to determine the pier durability assessment result at the current moment. The specific logic is as follows: when At that time, the durability assessment result of the bridge pier at the current moment is judged to be excellent; when At that time, the durability assessment result of the bridge pier at the current moment is judged to be good; when At that time, the durability level assessment result of the bridge pier at the current moment is judged to be general; when At that time, the durability assessment result of the bridge pier at the current moment is judged to be poor; in, The final overall durability score; , , The preset first durability level threshold, second durability level threshold, and third durability level threshold are defined, and the following conditions are met: .

10. A durability assessment system for prefabricated hollow-core steel-concrete composite bridge piers, used to perform the durability assessment method for prefabricated hollow-core steel-concrete composite bridge piers as described in any one of claims 1-9, characterized in that, include: The monitoring data acquisition module is used to acquire monitoring data of prefabricated hollow steel tube concrete bridge piers during service. The monitoring data includes corrosion potential of the outer steel tube, temperature and strain at the interface between the inner steel tube and the concrete, relative humidity inside the interlayer concrete, and time series data of pier top displacement. The data processing module is used to calculate the corrosion activity index of the outer steel pipe and the peeling risk coefficient of the inner interface based on the corrosion potential of the outer steel pipe and the temperature strain of the interface between the inner steel pipe and the concrete, and to determine the water saturation level of the interlayer concrete based on the difference between the relative humidity inside the interlayer concrete and the preset humidity threshold. The trend discrimination module is used to construct a durability status assessment model based on the corrosion activity index of the outer steel pipe, the peeling risk coefficient of the inner interface, and the water saturation level of the interlayer concrete, and to use the model to determine the comprehensive durability score of the pier at the current moment. Based on the comprehensive durability score and the time-domain characteristics of the pier top displacement time series data, it is determined whether the pier exhibits a stiffness degradation trend. The durability assessment module is used to correct the overall durability score based on the judgment result of stiffness degradation trend, obtain the corrected overall durability score, compare the corrected overall durability score with the preset durability level threshold, and output the durability level assessment result of the pier.

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