Method and system for evaluating bearing performance of fish-bellied box girder based on corrosion rate of prestressed tendons

Abstract

The invention provides a method and system for evaluating the bearing performance of a fish-bellied box girder based on the corrosion rate of prestressed tendons, and the method comprises the steps: screening out a defective prestressed tendon pipeline, and carrying out the positioning detection, thereby obtaining a defect position; acquiring potential data, and determining a corrosion area; measuring prestressed tendon parameters of the corrosion area, and calculating a corrosion rate and probability distribution thereof; establishing a relation model between the corrosion rate and the mechanical property; obtaining a sample of mechanical property parameters according to a relation model between the probability distribution of the corrosion rate and the mechanical property, and further obtaining a mean value and a standard deviation of bearing capacity indexes; applying load to the model to obtain stress of the prestressed tendons, and further obtaining a mean value and a standard deviation of action effect indexes; according to the method, the residual bearing performance of the fish-bellied box girder is evaluated according to the actual corrosion condition, potential structure risks can be found in advance, and the service life of the bridge is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bridge performance detection, and particularly relates to a fish-belly box girder bearing performance evaluation method and system based on a prestressed tendon corrosion rate. BACKGROUND

[0002] The fish-belly box girder is a common main girder form of elevated bridges in coastal cities, and its service environment is complex and susceptible to chloride ion corrosion. If the prestressed duct grouting is insufficient or the anchor head sealing is not tight, the chloride ions in the external environment will continuously invade and accumulate in the prestressed pipe, eventually causing the corrosion of the prestressed tendon. The corrosion will significantly reduce the mechanical properties of the prestressed tendon, and then affect the overall stress state and safety of the fish-belly box girder, increase the risk of structural failure, and induce serious safety accidents.

[0003] At present, the detection method for the service performance of the main girder prestressed tendon has not realized the complete technical chain from the prestressed pipe cavity detection to the main girder residual bearing performance evaluation. This lack of coherent detection means leads to information gaps when identifying the damage of the prestressed tendon and its influence on the overall performance of the main girder, and it is difficult to provide comprehensive and accurate evaluation results. SUMMARY

[0004] The present application is carried out to solve the above problems, and aims to provide a fish-belly box girder bearing performance evaluation method and system based on a prestressed tendon corrosion rate.

[0005] The application provides a fish-belly box girder bearing performance evaluation method based on a prestressed tendon corrosion rate, and the fish-belly box girder comprises a prestressed tendon pipeline and has the following characteristics: step S1, prestressed tendon pipelines with defective grouting quality are screened out according to a preset standard qualitative detection, and the defects of the prestressed tendon pipelines are positioned and detected by using an impact echo method to obtain defect positions; step S2, the surface concrete and the prestressed tendon pipeline are chiseled at the defect positions to fully expose the prestressed tendons, potential measurement points are arranged, potential data are collected, and a corrosion area is determined according to the potential data; step S3, the corrosion area is cleaned and prestressed tendon parameters of the corrosion area are measured, a corrosion rate and a probability distribution of the corrosion rate are calculated according to the prestressed tendon parameters; step S4, a relationship model between the corrosion rate and mechanical properties is established according to an accelerated corrosion test; step S5, a preset number of corrosion rate samples are generated by using Monte Carlo sampling according to the probability distribution of the corrosion rate, the corrosion rate samples are brought into the relationship model between the corrosion rate and the mechanical properties to obtain a preset number of mechanical property parameter samples, and statistical analysis is performed on the preset number of mechanical property parameter samples to obtain a mean value and a standard deviation of a bearing capacity index; step S6, a fish-belly box girder model is established according to fish-belly box girder parameters, the preset number of mechanical property parameter samples are substituted into the fish-belly box girder model to generate a preset number of fish-belly box girder models with updated mechanical property parameters, a load is applied to the preset number of fish-belly box girder models with updated mechanical property parameters to obtain a preset number of prestressed tendon stresses, and statistical analysis is performed on the preset number of prestressed tendon stresses to obtain a mean value and a standard deviation of an action effect index; and step S7, a reliability index of the fish-belly box girder is obtained according to the mean value and the standard deviation of the bearing capacity index and the mean value and the standard deviation of the action effect index.

[0006] In the fish-belly box girder bearing performance evaluation method based on a prestressed tendon corrosion rate provided by the application, the following characteristics can also be provided: step S1 comprises the following sub-steps: step S101, when the prestressed tendon satisfies a qualitative detection condition, vibration is performed at a beam end; step S102, a comprehensive grouting index is obtained according to the wave speed, frequency, received signal energy and excitation signal energy ratio of the excited elastic wave in the prestressed tendon pipeline of the exposed prestressed tendon, and when the comprehensive grouting index is less than a preset standard, the prestressed tendon pipeline is a defective prestressed tendon pipeline; step S103, the defective prestressed tendon pipeline is positioned and detected, the running line of the prestressed tendon in the prestressed tendon pipeline is marked on the beam plate of the defective prestressed tendon pipeline, and a first measurement point is marked on the running line; and step S104, vibration is performed at the first measurement point to obtain a first measurement point frequency peak value, and when the first measurement point frequency peak value is less than a preset frequency value, the first measurement point is a defect position.

[0007] In the method for evaluating the bearing performance of a fish-belly box girder based on the corrosion rate of prestressed tendons provided by the present invention, it can also have the following characteristics: wherein, step S1 also includes the following sub-steps: step S105, when the prestressed tendons do not meet the qualitative detection conditions, positioning detection is performed according to the gravity bending moment response distribution diagram of the fish-belly box girder.

[0008] In the method for evaluating the bearing performance of a fish-belly box girder based on the corrosion rate of prestressed tendons provided by the present invention, it may also have the following characteristics: wherein, step S3 includes the following sub-steps: step S301, cleaning the rusted area and marking a second measuring point in the rusted area; step S302, using a vernier caliper or an ultrasonic thickness gauge to measure the residual diameter of each steel wire of the prestressed tendons and the initial diameter of the non-rusted prestressed tendon steel wire of the same specification at the second measuring point; step S302, calculating the corrosion rate of the second measuring point based on the residual diameter and the initial diameter; step S303, measuring the corrosion rate of a preset number of second measuring points, obtaining an average value of the corrosion rate, and obtaining a probability distribution of the corrosion rate of the second measuring point based on the average value of the corrosion rate.

[0009] The method for evaluating the bearing performance of a fish-belly box girder based on the corrosion rate of prestressed tendons provided by the present invention may also have the following characteristics: wherein, in step S302, the corrosion rate of the second measuring point is calculated based on the residual diameter and the initial diameter, which can be obtained according to the following formula:

[0010]

[0011] Among them, D j is the residual diameter of the prestressed steel wire at the second measuring point, D0 is the initial diameter of the non-corroded prestressed steel wire of the same specification, n is the number of steel wires in a bundle of prestressed steel bars, and n i is the corrosion rate of the measuring point.

[0012] Step S303: measuring the corrosion rates of a preset number of second measurement points, and obtaining an average value of the corrosion rates can be obtained according to the following formula:

[0013]

[0014] Among them, m is the preset number, n i is the corrosion rate of the measuring point, μ η is the average value of the corrosion rate; the probability distribution of the corrosion rate of the second measuring point can be obtained according to the average value of the corrosion rate according to the following formula:

[0015]

[0016] Among them, m is the preset number, n i is the corrosion rate of the measuring point, μ η is the average value of the corrosion rate, σ ηThe standard deviation of the corrosion rate.

[0017] In the fish-belly box girder bearing performance evaluation method based on the corrosion rate of the prestressed tendon provided by the application, the step S4 can further have the following characteristics:

[0018] In step S401, the prestressed tendon is used as an anode, and a carbon rod is used as a cathode. After being immersed in a sodium chloride solution and connected to a constant current power supply, the prestressed tendon reaches a preset corrosion rate according to Faraday's law, and the formula is as follows:

[0019]

[0020] Wherein, η t is the target corrosion rate, I is the applied current intensity, t is the current time, M is the molar mass of iron, n is the number of electrons transferred in the electrochemical reaction, and F is the Faraday constant; in step S402, the stress-strain curve of the prestressed tendon reaching the preset corrosion rate is obtained, the mechanical property parameters are obtained according to the stress-strain curve of the prestressed tendon, and the relationship model between the corrosion rate and the mechanical property is established according to the preset corrosion rate and the mechanical property parameters.

[0021] In the fish-belly box girder bearing performance evaluation method based on the corrosion rate of the prestressed tendon provided by the application, the step S5 can further have the following characteristics: in step S5, the statistical analysis of the preset number of mechanical property parameter samples obtains the mean value of the bearing capacity index, and the formula is as follows:

[0022]

[0023] Wherein, μ R is the average value of the bearing capacity index, f puci is the sample of the mechanical property parameter, and k is the preset number; the statistical analysis of the preset number of mechanical property parameter samples obtains the standard deviation of the bearing capacity index, and the formula is as follows:

[0024]

[0025] Wherein, σ R is the standard deviation of the bearing capacity index, f puci is the sample of the mechanical property parameter, μ R is the average value of the bearing capacity index, and k is the preset number.

[0026] In the fish-belly box girder bearing performance evaluation method based on the corrosion rate of the prestressed tendon provided by the application, the step S6 can further have the following characteristics: in step S6, the statistical analysis of the stress of the preset number of prestressed tendons obtains the mean value of the action effect index, and the formula is as follows:

[0027]

[0028] wherein, μ S is the average value of the action effect index, f pi is the stress of the prestressed tendon, and k is a preset number; statistical analysis is performed on the stress of the prestressed tendon of the preset number to obtain the formula of the average value of the action effect index as follows:

[0029]

[0030] wherein, σ S is the standard deviation of the action effect index, μ S is the average value of the action effect index, f pi is the stress of the prestressed tendon, and k is a preset number.

[0031] In the fish-belly box girder bearing performance evaluation method based on the corrosion rate of the prestressed tendon provided by the application, the following features can also be provided: in step S7, the formula of the reliability index of the fish-belly box girder is obtained according to the average value and the standard deviation of the bearing capacity index and the average value and the standard deviation of the action effect index as follows:

[0032]

[0033] wherein, β is the reliability index of the fish-belly box girder, μ R is the average value of the bearing capacity index, μ S is the average value of the action effect index; σ R is the standard deviation of the bearing capacity index, σ S is the standard deviation of the action effect index.

[0034] The application also provides a fish-belly box girder bearing performance evaluation system based on the corrosion rate of the prestressed tendon, which has the following features and comprises:

[0035] A defect position detection module is configured to qualitatively detect and screen prestressed tendon pipes with defective grouting quality according to a preset standard, and to detect and locate defects of the prestressed tendon pipes by using an impact echo method to obtain defect positions.

[0036] An corrosion area detection module is configured to chisel the surface concrete and the prestressed tendon pipe at the defect positions to fully expose the prestressed tendon, arrange a potential measurement point, collect potential data, and determine a corrosion area according to the potential data.

[0037] A first calculation module is configured to clean the corrosion area and measure prestressed tendon parameters of the corrosion area, calculate a corrosion rate and a probability distribution of the corrosion rate according to the prestressed tendon parameters.

[0038] A model establishment module is configured to establish a relationship model between the corrosion rate and the mechanical property according to an accelerated corrosion test.

[0039] The second calculation module is configured to generate a preset number of corrosion rate samples by using Monte Carlo sampling according to a probability distribution of the corrosion rate, to obtain a preset number of mechanical property parameter samples by bringing the corrosion rate samples into a relationship model between the corrosion rate and the mechanical property, and to obtain a mean value and a standard deviation of the bearing capacity index by statistically analyzing the preset number of mechanical property parameter samples.

[0040] The third calculation module is configured to establish a fish-belly box girder model according to fish-belly box girder parameters, to generate a preset number of fish-belly box girder models with updated mechanical property parameters by substituting the preset number of mechanical property parameter samples into the fish-belly box girder model, to obtain a preset number of prestressed tendon stresses by applying loads to the preset number of fish-belly box girder models with updated mechanical property parameters, and to obtain a mean value and a standard deviation of the action effect index by statistically analyzing the preset number of prestressed tendon stresses.

[0041] The fourth calculation module is configured to obtain a reliability index of the fish-belly box girder according to the mean value and the standard deviation of the bearing capacity index and the mean value and the standard deviation of the action effect index.

[0042] Effects of the application

[0043] According to the prestressed tendon corrosion rate-based fish-belly box girder bearing performance evaluation method and system, the prestressed tendon pipeline with defective grouting quality is screened out through qualitative detection according to a preset standard, and the defect position of the prestressed tendon pipeline is obtained through positioning detection by using an impact echo method; the surface concrete and the prestressed tendon pipeline are chiseled at the defect position, the prestressed tendon is fully exposed, a potential measurement point is arranged, potential data is collected, and a corrosion area is determined according to the potential data; the corrosion area is cleaned and the prestressed tendon parameters of the corrosion area are measured, the corrosion rate and the probability distribution of the corrosion rate are calculated according to the prestressed tendon parameters; a relationship model between the corrosion rate and the mechanical property is established according to an accelerated corrosion test; according to the probability distribution of the corrosion rate, a preset number of corrosion rate samples are generated by using Monte Carlo sampling, the corrosion rate samples are brought into the relationship model between the corrosion rate and the mechanical property to obtain a preset number of mechanical property parameter samples, and statistical analysis is performed on the preset number of mechanical property parameter samples to obtain the mean value and the standard deviation of the bearing capacity index; a fish-belly box girder model is established according to the fish-belly box girder parameters, the preset number of mechanical property parameter samples are substituted into the fish-belly box girder model to generate a preset number of fish-belly box girder models with updated mechanical property parameters, a load is applied to the preset number of fish-belly box girder models with updated mechanical property parameters to obtain a preset number of prestressed tendon stresses, and statistical analysis is performed on the preset number of prestressed tendon stresses to obtain the mean value and the standard deviation of the action effect index; and the reliability index of the fish-belly box girder is obtained according to the mean value and the standard deviation of the bearing capacity index and the mean value and the standard deviation of the action effect index, so that the prestressed tendon corrosion condition can be comprehensively and accurately evaluated by combining various nondestructive detection methods, the residual bearing performance of the fish-belly box girder under the actual corrosion condition is evaluated after the mechanical property parameters of the model are updated according to the actual corrosion condition, potential structural risks can be found in advance, the maintenance and reinforcement scheme can be optimized, the service life of the bridge can be prolonged, and the method has a wide engineering application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is a flowchart of the prestressed tendon corrosion rate-based fish-belly box girder bearing performance evaluation method in the embodiment of the present application.

[0045] Figure 2 is a schematic diagram of prestressed tendon pipeline detection in the prestressed tendon corrosion rate-based fish-belly box girder bearing performance evaluation method in the embodiment of the present application.

[0046] Figure 3 is a prestressed tendon distribution diagram for qualitative detection and positioning detection in the prestressed tendon corrosion rate-based fish-belly box girder bearing performance evaluation method in the embodiment of the present application.

[0047] Figure 4 is the gravity moment shear response distribution diagram of the fish belly box girder of the fish belly box girder load carrying performance evaluation method based on the prestressed tendon corrosion rate in the embodiment of the application.

[0048] Figure 5 is the positioning detection prestressed tendon distribution profile of the fish belly box girder load carrying performance evaluation method based on the prestressed tendon corrosion rate in the embodiment of the application. DETAILED DESCRIPTION

[0049] In the description of the present application, it should be explained that, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected, it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal communication of two elements or the interaction relationship of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0050] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the following embodiments combine the drawings to specifically describe the fish belly box girder load carrying performance evaluation method and system based on the prestressed tendon corrosion rate of the present application.

[0051] EMBODIMENT

[0052] Figure 1 is the flowchart of the fish belly box girder load carrying performance evaluation method based on the prestressed tendon corrosion rate in the embodiment of the application.

[0053] As shown in Figure 1 , the present embodiment provides a fish belly box girder load carrying performance evaluation method based on the prestressed tendon corrosion rate, the fish belly box girder includes a prestressed tendon pipeline, comprising:

[0054] Step S1, according to the preset standard, the prestressed tendon pipeline with defective pressure grouting quality is qualitatively detected and screened, and the impact echo method is used to positionally detect the defects of the prestressed tendon pipeline, so as to obtain the defect position.

[0055] Figure 2 is the prestressed tendon pipeline detection schematic diagram of the fish belly box girder load carrying performance evaluation method based on the prestressed tendon corrosion rate in the embodiment of the application.

[0056] Figure 3 is the prestressed tendon distribution diagram of the qualitative detection and positioning detection of the fish belly box girder load carrying performance evaluation method based on the prestressed tendon corrosion rate in the embodiment of the application. As shown in Figure 2 and Figure 3 , wherein, step S1 includes the following substeps:

[0057] Step S101, when the prestressed tendon 21 meets the qualitative detection condition, excitation is carried out at the beam end. For the prestressed tendon 21 that can expose the steel strand at both ends of the prestressed tendon duct 32, first, the mortar at the anchor position is drilled open using an electric drill to expose the prestressed tendon 21, the sensor 41 is fixed on the exposed steel strand at both ends of the prestressed tendon duct 32, and the excitation hammer and the excitation cone are combined to qualitatively detect the excitation point 42 at the beam end, and the wave speed, frequency, received signal energy and excitation signal energy of the steel strand are collected.

[0058] Step S102, the comprehensive compaction index is obtained according to the ratio of the wave speed, frequency, received signal energy and excitation signal energy of the elastic wave excited by the exposed prestressed tendon 21 in the prestressed tendon duct 32, and when the comprehensive compaction index is less than the preset standard, the prestressed tendon duct 32 is a defective prestressed tendon duct 32.

[0059] The comprehensive compaction index is calculated according to the full-length attenuation method, the full-length wave speed method and the transfer function method in the Technical Specification for Quality Inspection and Evaluation of Prestressed Construction of Highway Concrete Bridges DB35 / T 1638-2017.

[0060] Step S103, the defective prestressed tendon duct 32 is detected and positioned, and the running line of the prestressed tendon 21 in the prestressed tendon duct 32 is marked on the beam slab of the defective prestressed tendon duct 32, and the first measuring point is marked on the running line. Wherein, after marking the running line of the prestressed tendon duct 32 on the beam slab, the first measuring point 43 is marked at an interval of 20 cm, and the first measuring point 43 is at least one.

[0061] Step S104, excitation is carried out at the first measuring point 43 to obtain the frequency peak value of the first measuring point 43, and when the frequency peak value of the first measuring point 43 is less than the preset frequency value, the first measuring point is a defective position. Figure 3 The prestressed tendon 22 subjected to qualitative detection and the prestressed tendon 23 subjected to positioning detection are shown in the figure.

[0062] The sensor is fixed point by point on the first measuring point 43 marked on the beam slab, and the signal is collected by point excitation using the excitation hammer. According to the frequency peak value discrimination method in the Technical Specification for Impact Echo Method for Detecting Concrete Defects JGJ / T 411-2017, when the frequency peak value of the first measuring point 43 is less than the preset frequency value, the first measuring point 43 is a defective position.

[0063] Figure 4 is the gravity moment-shear response distribution diagram of the fish-belly box girder of the prestressed tendon corrosion rate-based fish-belly box girder bearing capacity evaluation method in the embodiment of the application.

[0064] Figure 5It is the positioning detection prestressed tendon distribution profile of the fish belly box girder load carrying performance evaluation method based on the prestressed tendon corrosion rate in the embodiment of the application.

[0065] As shown in Figure 4 and Figure 5 , step S105, when the prestressed tendon 21 does not meet the qualitative detection condition, the positioning detection is carried out according to the gravity bending moment response distribution diagram of the fish belly box girder.

[0066] In order to reduce the workload of positioning detection, the positioning can be carried out according to the gravity bending moment response distribution diagram of the fish belly box girder as shown in Figure 4 . Figure 4 As shown in the figure, the negative bending moment response 51 of the upper side of the beam section under tension, the positive bending moment response 52 of the lower side of the beam section under tension and the shear response 53 are shown, and the prestressed tendon 23 in the A-A profile, B-B profile, C-C profile and D-D profile with larger bending moment or shear response is positioned and detected.

[0067] Step S2, chisel the surface concrete and the prestressed tendon duct 32 at the defect position, fully expose the prestressed tendon 21, arrange the potential measurement point, collect the potential data, and determine the corrosion area according to the potential data.

[0068] Firstly, the surface concrete and the prestressed tendon duct 32 are chiseled using an electric drill to fully expose the prestressed tendon 21. Then, the potential measurement points are arranged on the surface of the main beam, a reasonable measurement grid is formed near the defect position, and it is ensured that the measurement range of the potential distribution can cover the potential corrosion area. The potential distribution on the surface of the prestressed tendon 21 is measured point by point by using a reference electrode, the data is recorded and the potential distribution diagram is drawn. The range and distribution law of the corrosion potential are analyzed in combination with the potential difference, the corrosion area of the prestressed tendon 21 is determined according to the standard specification and the corrosion evaluation criterion. In order to improve the detection accuracy, the corrosion products on the surface of the prestressed tendon 21 can be removed as necessary to reduce the influence of the corrosion products on the potential measurement results.

[0069] Step S3, clean the corrosion area and measure the prestressed tendon 21 parameters of the corrosion area, calculate the corrosion rate and the probability distribution of the corrosion rate according to the prestressed tendon 21 parameters.

[0070] Step S3 includes the following sub-steps:

[0071] Step S301, clean the corrosion area and mark the second measurement point in the corrosion area. The purpose of cleaning the corrosion area is to ensure the smoothness of the measurement area to improve the measurement accuracy.

[0072] Step S302, the residual diameter of each steel wire of the prestressed tendon 21 and the initial diameter of the steel wire of the non-corrosion prestressed tendon 21 of the same specification are measured at the second measurement point using a vernier caliper or an ultrasonic thickness gauge.

[0073] Step S302, calculating the corrosion rate of the second measurement point according to the residual diameter and the initial diameter.

[0074] The corrosion rate of the second measurement point according to the residual diameter and the initial diameter can be obtained according to the following formula:

[0075]

[0076] wherein D j is the residual diameter of the steel wire of the second measurement point, D0 is the initial diameter of the steel wire of the same specification and without corrosion, n is the number of steel wires of a bundle of the prestressed tendon 21, n i is the corrosion rate of the measurement point.

[0077] Step S303, measuring the corrosion rates of a preset number of second measurement points, obtaining the average value of the corrosion rates, and obtaining the probability distribution of the corrosion rates of the second measurement points according to the average value of the corrosion rates.

[0078] The preset number of second measurement points are arranged uniformly along the length direction in the corrosion area x.

[0079] The average value of the corrosion rates of the preset number of second measurement points can be obtained according to the following formula:

[0080]

[0081] wherein m is the preset number, n i is the corrosion rate of the measurement point, μ η is the average value of the corrosion rates.

[0082] The probability distribution of the corrosion rates of the second measurement points according to the average value of the corrosion rates can be obtained according to the following formula:

[0083]

[0084] wherein m is the preset number, n i is the corrosion rate of the measurement point, μ η is the average value of the corrosion rates, σ η is the standard deviation of the corrosion rates.

[0085] Step S4, establishing a relationship model between the corrosion rate and the mechanical properties according to the accelerated corrosion test.

[0086] Step S4 includes the following sub-steps:

[0087] Step S401, taking the prestressed tendon 21 as an anode and a carbon rod as a cathode, immersing them in a sodium chloride solution, connecting a constant current power supply, and making the prestressed tendon 21 reach a preset corrosion rate according to Faraday's law, the formula being as follows:

[0088]

[0089] wherein η t is the target corrosion rate, I is the applied current intensity, t is the current time, M is the molar mass of iron (55.85 g / mol), n is the number of electrons transferred in the electrochemical reaction, and F is the Faraday constant (9648 C / mol).

[0090] The middle part of the prestressed tendon 21 is taken as the corrosion area, and the end part is immersed in an electrolyte solution containing NaCl (the mass fraction can be taken as 3.5%) after insulation treatment. A constant current power supply is connected under the condition of controlling the current density and the current time, and a predetermined corrosion rate is reached. By setting different corrosion times or corrosion medium concentrations, prestressed tendons 21 with different corrosion rates can be obtained through accelerated corrosion tests. The stress-strain curve of the prestressed tendon 21 with each corrosion rate is obtained through a tensile test, and the mechanical property parameter is extracted from the stress-strain curve. In this embodiment, the mechanical property parameter is the ultimate strength.

[0091] In step S402, the stress-strain curve of the prestressed tendon 21 reaching the preset corrosion rate is obtained, the mechanical property parameter is obtained according to the stress-strain curve of the prestressed tendon, and the relationship model between the corrosion rate and the mechanical property is established according to the preset corrosion rate and the mechanical property parameter.

[0092] In addition, the relationship model between the corrosion rate and the mechanical property parameter proposed by the Journal of Building Materials can also be directly selected, and the model is as follows:

[0093]

[0094] wherein f pu is the ultimate strength of the uncorroded prestressed tendon 21, and f puc is the ultimate strength of the corroded prestressed tendon 21.

[0095] In step S5, according to the probability distribution of the corrosion rate, a preset number of corrosion rate samples are generated by Monte Carlo sampling, the corrosion rate samples are brought into the relationship model between the corrosion rate and the mechanical property to obtain a preset number of samples of the mechanical property parameter, and statistical analysis is performed on the preset number of samples of the mechanical property parameter to obtain the mean value and the standard deviation of the bearing capacity index.

[0096] The mean value formula of the bearing capacity index obtained by statistical analysis on the preset number of samples of the mechanical property parameter is as follows:

[0097]

[0098] wherein μ R is the average value of the bearing capacity index, f puci is the sample of the mechanical property parameter, and k is the preset number.

[0099] The standard deviation formula of the bearing capacity index obtained by statistical analysis of the preset number of samples of mechanical performance parameters is as follows:

[0100]

[0101] Wherein, σ R is the standard deviation of the bearing capacity index, f puci is the sample of mechanical performance parameters, μ R is the average value of the bearing capacity index, and k is the preset number.

[0102] Step S6, according to the fish belly box girder parameters to establish fish belly box girder model, the preset number of samples of mechanical performance parameters into the fish belly box girder model, generate the preset number of fish belly box girder model after updating the mechanical performance parameters, to the preset number of fish belly box girder model after updating the mechanical performance parameters to apply load to get the preset number of prestressed tendon 21 stress, the stress of the preset number of prestressed tendon 21 is statistically analyzed to obtain the mean and standard deviation of the action effect index.

[0103] Wherein, fish belly box girder parameters include: actual size, material properties and boundary conditions, the established fish belly box girder model includes the mechanical performance parameters of prestressed tendon pipe 32.

[0104] To the preset number of fish belly box girder model after updating the mechanical performance parameters, according to the relevant provisions of "highway bridge and culvert design general specification" JTG D60-2015, the load combination expression is:

[0105] S=G+γ c ·m h ·1+μ)·(P k +q k ·l)

[0106] Wherein, wherein, G is the dead load (structure self weight, bridge pavement, counterweight, etc.), γ c is the sub item coefficient of lane load, which is 1.4, m h is the transverse lane step load coefficient, μ is the impact coefficient, P k is the concentrated load standard value of lane load, q k is the uniform load standard value of lane load, and l is the span of the bridge.

[0107] Through the operation of the preset number of model analysis to get the stress f pi of the preset number of prestressed tendon 21.

[0108] The formula of the mean value of the action effect index obtained by statistical analysis of the preset number of prestressed tendon 21 stress is as follows:

[0109]

[0110] wherein μ S is the mean value of the action effect index, f pi is the stress of the prestressed tendon 21, and k is the preset number.

[0111] The formula of the mean value of the action effect index obtained by statistically analyzing the stress of the prestressed tendon 21 is as follows:

[0112]

[0113] wherein σ S is the standard deviation of the action effect index, μ S is the mean value of the action effect index, f pi is the stress of the prestressed tendon 21, and k is the preset number.

[0114] Step S7, obtaining the reliability index of the fish-belly box girder according to the mean value and the standard deviation of the bearing capacity index and the mean value and the standard deviation of the action effect index.

[0115] The formula of the reliability index of the fish-belly box girder obtained according to the mean value and the standard deviation of the bearing capacity index and the mean value and the standard deviation of the action effect index is as follows:

[0116]

[0117] wherein β is the reliability index of the fish-belly box girder, μ R is the mean value of the bearing capacity index, μ S is the mean value of the action effect index; σ R is the standard deviation of the bearing capacity index, and σ S is the standard deviation of the action effect index.

[0118] The embodiment also provides a fish-belly box girder bearing performance evaluation system based on a prestressed tendon corrosion rate, comprising:

[0119] A defect position detection module is configured to qualitatively detect and screen prestressed tendon pipes with defective grouting quality according to a preset standard, and to detect and locate defects of the prestressed tendon pipes by using an impact echo method to obtain defect positions.

[0120] An corrosion area detection module is configured to chisel the surface concrete and the prestressed tendon pipes at the defect positions to fully expose the prestressed tendons, arrange potential measurement points, collect potential data, and determine corrosion areas according to the potential data.

[0121] A first calculation module is configured to clean the corrosion areas and measure prestressed tendon parameters of the corrosion areas, calculate a corrosion rate and a probability distribution of the corrosion rate according to the prestressed tendon parameters.

[0122] a model establishing module configured to establish a relationship model between the corrosion rate and the mechanical property according to the accelerated corrosion test;

[0123] a second calculating module configured to generate a preset number of corrosion rate samples by using Monte Carlo sampling according to the probability distribution of the corrosion rate, to bring the corrosion rate samples into the relationship model between the corrosion rate and the mechanical property to obtain a preset number of samples of the mechanical property parameters, and to statistically analyze the preset number of samples of the mechanical property parameters to obtain the mean value and the standard deviation of the bearing capacity index;

[0124] a third calculating module configured to establish a fish-belly box girder model according to the parameters of the fish-belly box girder, to bring the preset number of samples of the mechanical property parameters into the fish-belly box girder model to generate a preset number of fish-belly box girder models with updated mechanical property parameters, to apply a load to the preset number of fish-belly box girder models with updated mechanical property parameters to obtain a preset number of stresses of the prestressed tendons, and to statistically analyze the preset number of stresses of the prestressed tendons to obtain the mean value and the standard deviation of the action effect index;

[0125] a fourth calculating module configured to obtain the reliability index of the fish-belly box girder according to the mean value and the standard deviation of the bearing capacity index and the mean value and the standard deviation of the action effect index.

[0126] Effects of the embodiment

[0127] The fish-belly box girder bearing performance evaluation method and system based on the prestressed tendon corrosion rate related by the application, because it includes: step S1, according to the preset standard qualitative detection screening out the prestressed tendon pipeline with defective grouting quality, and using the impact echo method to locate and detect the defects of the prestressed tendon pipeline, to obtain the defect position; step S2, chiseling the surface concrete and the prestressed tendon pipeline at the defect position, so that the prestressed tendon is fully exposed, arranging the potential measurement point, collecting the potential data, and determining the corrosion area according to the potential data; step S3, cleaning the corrosion area and measuring the prestressed tendon parameters of the corrosion area, calculating the corrosion rate and the probability distribution of the corrosion rate according to the prestressed tendon parameters; step S4, establishing the relationship model between the corrosion rate and the mechanical property according to the accelerated corrosion test; step S5, according to the probability distribution of the corrosion rate, using Monte Carlo sampling to generate a preset number of corrosion rate samples, bringing the corrosion rate samples into the relationship model between the corrosion rate and the mechanical property to obtain a preset number of mechanical property parameter samples, and statistically analyzing the preset number of mechanical property parameter samples to obtain the mean value and the standard deviation of the bearing capacity index; step S6, establishing the fish-belly box girder model according to the fish-belly box girder parameters, substituting the preset number of mechanical property parameter samples into the fish-belly box girder model, generating a preset number of fish-belly box girder models with updated mechanical property parameters, applying load to the preset number of fish-belly box girder models with updated mechanical property parameters to obtain the stress of the prestressed tendon, and statistically analyzing the stress of the prestressed tendon to obtain the mean value and the standard deviation of the action effect index; step S7, obtaining the reliability index of the fish-belly box girder according to the mean value and the standard deviation of the bearing capacity index and the mean value and the standard deviation of the action effect index, so that the fish-belly box girder bearing performance evaluation method and system based on the prestressed tendon corrosion rate of the application can comprehensively and accurately evaluate the corrosion condition of the prestressed tendon by combining various non-destructive testing methods, and can evaluate the residual bearing performance of the fish-belly box girder under the actual corrosion condition after updating the mechanical property parameters of the model according to the actual corrosion condition, so as to find out the potential structural risk in advance, optimize the maintenance and reinforcement scheme, prolong the service life of the bridge, and has wide engineering application prospect.

[0128] The prestressed tendon which cannot be qualitatively detected is directly located and detected by the gravity bending moment response distribution diagram.

[0129] The mechanical property parameters of the prestressed tendon under the target corrosion rate are obtained by the accelerated corrosion test.

[0130] The corrosion rate samples are generated by Monte Carlo sampling.

[0131] Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application, and various changes and improvements can be made without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for evaluating the bearing capacity of a fish-belly box girder based on the corrosion rate of prestressed tendons, wherein the fish-belly box girder includes a prestressed tendon duct, characterized in that: include: Step S1, screening out prestressed tendon pipes with defective grouting quality through qualitative detection according to preset standards, and locating the defects of the prestressed tendon pipes using an impact echo method to obtain the defect locations; Step S2: chiseling the surface concrete and the prestressed tendon pipe at the defect location to fully expose the prestressed tendons, arranging potential measurement points, collecting potential data, and determining the rusted area based on the potential data; Step S3, cleaning the corroded area and measuring the parameters of the prestressed tendons in the corroded area, and calculating the corrosion rate and the probability distribution of the corrosion rate based on the prestressed tendon parameters; Step S4, establishing a relationship model between corrosion rate and mechanical properties based on the accelerated corrosion test; Step S5: generating a preset number of corrosion rate samples using Monte Carlo sampling based on the probability distribution of the corrosion rate, subjecting the corrosion rate samples to the relationship model between the corrosion rate and mechanical properties to obtain a preset number of mechanical property parameter samples, and performing statistical analysis on the preset number of mechanical property parameter samples to obtain a mean and standard deviation of a bearing capacity index; Step S6, establishing a fish-belly box girder model according to the fish-belly box girder parameters, substituting the preset number of mechanical performance parameter samples into the fish-belly box girder model, generating a preset number of fish-belly box girder models with updated mechanical performance parameters, applying loads to the preset number of fish-belly box girder models with updated mechanical performance parameters to obtain stresses of a preset number of prestressed tendons, and performing statistical analysis on the stresses of the preset number of prestressed tendons to obtain a mean and a standard deviation of an action effect index; Step S7: obtaining a reliability index of the fish-belly box girder according to the mean value and standard deviation of the bearing capacity index and the mean value and standard deviation of the action effect index.

2. The method for evaluating the bearing capacity of a fish-belly box girder based on the corrosion rate of prestressed tendons according to claim 1 is characterized in that: in, Step S1 includes the following sub-steps: Step S101, when the prestressed tendons meet the qualitative detection conditions, vibration is excited at the beam end; Step S102: obtaining a comprehensive grouting index based on the wave velocity, frequency, received signal energy, and excitation signal energy ratio of the elastic wave excited by the exposed prestressed tendons in the prestressed tendon pipe. When the comprehensive grouting index is less than a preset standard, the prestressed tendon pipe is considered defective. Step S103, performing a positioning inspection on the defective prestressed tendon pipe, marking a direction line of the prestressed tendon in the prestressed tendon pipe on the beam plate of the defective prestressed tendon pipe, and marking a first measuring point on the direction line; Step S104 : performing excitation at the first measurement point to obtain a frequency peak value of the first measurement point. When the frequency peak value of the first measurement point is less than a preset frequency value, the first measurement point is a defect location.

3. The method for evaluating the bearing capacity of a fish-belly box girder based on the corrosion rate of prestressed tendons according to claim 2 is characterized in that: in, Step S1 also includes the following sub-steps: Step S105: When the prestressed tendons do not meet the qualitative detection conditions, a positioning detection is performed according to the gravity bending moment response distribution diagram of the fish-belly box girder.

4. The method for evaluating the bearing capacity of a fish-belly box girder based on the corrosion rate of prestressed tendons according to claim 1 is characterized in that: in, Step S3 includes the following sub-steps: Step S301, cleaning the corroded area and marking a second measuring point in the corroded area; Step S302: Using a vernier caliper or an ultrasonic thickness gauge, the residual diameter of each prestressed steel wire and the initial diameter of a non-corroded prestressed steel wire of the same specification are measured at a second measuring point. Step S302, calculating the corrosion rate of the second measuring point according to the residual diameter and the initial diameter; Step S303 , measuring the corrosion rates of a preset number of second measurement points to obtain an average value of the corrosion rates, and obtaining a probability distribution of the corrosion rates of the second measurement points based on the average value of the corrosion rates.

5. The method for evaluating the bearing capacity of a fish-belly box girder based on the corrosion rate of prestressed tendons according to claim 4 is characterized in that: in, In step S302, the corrosion rate of the second measuring point is calculated based on the residual diameter and the initial diameter, which can be obtained according to the following formula: Among them, D j is the residual diameter of the prestressed steel wire at the second measuring point, D0 is the initial diameter of the non-corroded prestressed steel wire of the same specification, n is the number of steel wires in a bundle of prestressed steel bars, and n i is the corrosion rate of the measuring point; Step S303: measuring the corrosion rates of a preset number of second measurement points, and obtaining an average value of the corrosion rates can be obtained according to the following formula: Among them, m is the preset number, n i is the corrosion rate of the measuring point, μ η is the average value of the corrosion rate; The probability distribution of the corrosion rate at the second measuring point obtained based on the average value of the corrosion rate can be obtained according to the following formula: Among them, m is the preset number, n i is the corrosion rate of the measuring point, μ η is the average value of the corrosion rate, σ η is the standard deviation of the corrosion rate.

6. The method for evaluating the bearing performance of a fish-belly box girder based on the corrosion rate of prestressed tendons according to claim 1, Its characteristics are: Wherein, step S4 includes the following sub-steps: In step S401, the prestressed tendon is used as an anode and the carbon rod is used as a cathode. After being immersed in a sodium chloride solution and connected to a constant current power supply, the prestressed tendon is made to reach a preset corrosion rate according to Faraday's law, which is as follows: Among them, η t is the target corrosion rate, I is the applied current intensity, t is the power-on time, M is the molar mass of iron, n is the number of electrons transferred in the electrochemical reaction, and F is the Faraday constant; Step S402: Obtain a stress-strain curve of a prestressed tendon that reaches a preset corrosion rate, obtain mechanical property parameters based on the stress-strain curve of the prestressed tendon, and establish a relationship model between the corrosion rate and the mechanical property based on the preset corrosion rate and the mechanical property parameters.

7. The method for evaluating the bearing capacity of a fish-belly box girder based on the corrosion rate of prestressed tendons according to claim 1 is characterized in that: in, In step S5, statistical analysis is performed on the preset number of mechanical performance parameter samples to obtain the mean value formula of the bearing capacity index as follows: Among them, μ R is the average value of the bearing capacity index, f puci is the sample of mechanical performance parameters, k is the preset number; The standard deviation formula of the bearing capacity index obtained by statistical analysis of the preset number of mechanical performance parameter samples is as follows: Among them, σ R is the standard deviation of the bearing capacity index, f puci is the mechanical properties parameter of the sample, μ R is the average value of the bearing capacity index, and k is the preset number.

8. The method for evaluating the bearing capacity of a fish-belly box girder based on the corrosion rate of prestressed tendons according to claim 1, characterized in that: in, In step S6, the stress of the preset number of prestressed tendons is statistically analyzed to obtain the mean value of the effect index according to the following formula: Among them, μ S is the average value of the effect index, f pi is the stress of the prestressed tendon, k is the preset number; The formula for obtaining the mean value of the effect index by statistically analyzing the stress of the preset number of prestressed tendons is as follows: Among them, σ S is the standard deviation of the effect index, μ S is the average value of the effect index, f pi is the stress of the prestressed tendon, and k is the preset number.

9. The method for evaluating the bearing capacity of a fish-belly box girder based on the corrosion rate of prestressed tendons according to claim 1, characterized in that: in, In step S7, the formula for obtaining the reliability index of the fish-belly box girder is as follows based on the mean and standard deviation of the bearing capacity index and the mean and standard deviation of the action effect index: Among them, β is the reliability index of fish-belly box girder, μ R is the average value of the bearing capacity index, μ S is the average value of the effect index; σ R is the standard deviation of the bearing capacity index, σ S is the standard deviation of the effect index.

10. A fish-belly box girder bearing performance evaluation system based on prestressed tendon corrosion rate, characterized in that: include: A defect location detection module is used to qualitatively detect and screen out prestressed tendon pipes with defective grouting quality according to preset standards, and locate the defects of the prestressed tendon pipes using the impact echo method to obtain the defect locations; A corrosion area detection module is used to chisel away the surface concrete and prestressed tendon pipes at the defect location to fully expose the prestressed tendons, arrange potential measurement points, collect potential data, and determine the corrosion area based on the potential data; a first calculation module, configured to clean the corroded area and measure parameters of the prestressed tendons in the corroded area, and calculate the corrosion rate and the probability distribution of the corrosion rate based on the parameters of the prestressed tendons; Model building module, used to establish the relationship model between corrosion rate and mechanical properties based on accelerated corrosion test; a second calculation module, configured to generate a preset number of corrosion rate samples using Monte Carlo sampling based on the probability distribution of the corrosion rate, subject the corrosion rate samples to the relationship model between the corrosion rate and the mechanical property to obtain a preset number of mechanical property parameter samples, and perform statistical analysis on the preset number of mechanical property parameter samples to obtain a mean and standard deviation of a bearing capacity index; a third calculation module, for establishing a fish-belly box girder model according to the fish-belly box girder parameters, substituting the preset number of mechanical performance parameter samples into the fish-belly box girder model, generating a preset number of fish-belly box girder models with updated mechanical performance parameters, applying loads to the preset number of fish-belly box girder models with updated mechanical performance parameters to obtain stresses of a preset number of prestressed tendons, and performing statistical analysis on the stresses of the preset number of prestressed tendons to obtain a mean and a standard deviation of an action effect index; The fourth calculation module is used to obtain the reliability index of the fish-belly box girder according to the mean value and standard deviation of the bearing capacity index and the mean value and standard deviation of the action effect index.

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