CN117740664B - Method, system and device for evaluating durability of freezing and thawing environment of concrete structure - Google Patents
Method, system and device for evaluating durability of freezing and thawing environment of concrete structure Download PDFInfo
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Abstract
The invention provides a method, a system and a device for evaluating durability of a freeze thawing environment of a concrete structure, and relates to the technical field of durability evaluation of the concrete structure, wherein the method comprises the following steps: preparing a standard test piece; performing a freeze thawing test on the standard test piece; constructing a spectrum system; scanning to obtain spectral imaging data of a standard test piece; collecting normal image data of a standard test piece, and calculating the surface porosity; measuring the concrete compressive strength of the standard test piece; constructing a database; screening characteristic wavelengths; the training evaluation model is used for obtaining corresponding reflectivity through characteristic wavelength, and the compressive strength and the surface porosity of the concrete are evaluated through the reflectivity; and collecting spectral data of the tested component, inputting the spectral data into an evaluation model, and outputting the compressive strength and the surface porosity. The invention can not damage the integrity of the detected member or structure, has simple operation, high evaluation speed, high accuracy and strong expansibility, and can carry out integral evaluation on the durability of the freezing and thawing environment of the concrete structure by collecting the spectrum data.
Description
Technical Field
The invention relates to the technical field of durability evaluation of concrete structures, in particular to a method, a system and a device for evaluating durability of a freeze-thawing environment of a concrete structure.
Background
The concrete belongs to porous materials, free water in capillary holes in the concrete can be repeatedly frozen and melted due to the freeze-thawing circulation in the freeze-thawing environment, so that the effects of crystallization expansion pressure, hydrostatic pressure, osmotic pressure and the like are generated, defects such as pores and cracks in the concrete are continuously developed, the internal structure of the concrete is further degraded, the performances such as elastic modulus and flexural strength of the concrete are seriously reduced, and the service life of the concrete is finally seriously reduced due to the diseases such as degradation and cracking of the surface of the concrete.
In the identification of the safety of concrete structures in a freeze-thawing environment, it is necessary to assess, by means of relevant indicators, the internal damage of the concrete caused by the action of the freeze-thawing cycle. At present, indexes for evaluating damage caused by freeze thawing cycle in concrete mainly comprise strength loss, ultrasonic speed, dynamic elastic modulus, surface resistivity and the like: the strength loss is evaluated by a core drilling sampling method, a drawing method and the like in the engineering, so that the concrete strength is destructive to a concrete structure; the ultrasonic method utilizes the speed of the ultrasonic wave in the concrete to estimate the intensity and internal defects, but if water accumulation or slurry exists in the cracks, the accuracy of the measurement result is affected; the dynamic elastic modulus is measured by a professional instrument through a resonance method; the concrete resistivity is measured by adopting a four-electrode method, namely four electrodes are contacted on the surface of the concrete at equal intervals, two outer electrodes are current electrodes, two inner electrodes are voltage electrodes, and the concrete resistivity can be obtained by detecting the concrete resistance between the two voltage electrodes.
While these methods can identify the safety of concrete structures in a freeze-thaw environment, they are destructive to existing structures and may have an impact on the integrity or strength of the existing structure; in addition, the methods often need to use various professional equipment, have complex operation steps and long test period, and are easy to introduce errors; and each test can only evaluate the freezing and thawing damage condition of local concrete, and the whole safety of the concrete member or structure in the freezing and thawing environment can not be rapidly and accurately identified.
Disclosure of Invention
The invention aims to provide a method, a system and a device for evaluating the durability of a concrete structure in a freeze thawing environment, so as to solve at least one of the technical problems in the prior art.
In order to solve the technical problems, the invention provides a method for evaluating the durability of a concrete structure in a freeze thawing environment, which comprises the following steps:
step S10, preparing a plurality of groups of first standard test pieces in a classified mode based on concrete evaluation conditions, and collecting physical indexes of the first standard test pieces; the concrete evaluation conditions comprise concrete strength grade, freezing and thawing times and the like;
step S20, judging the compressive strength and physical index of the concrete with the structure losing the bearing capacity according to the technical specifications, calculating the number of freeze thawing cycles, and performing a freeze thawing test on the first standard test piece;
Step S30, constructing a spectrum system, such as a near infrared hyperspectral system, by a spectrum camera;
step S40, performing spectrum scanning on the surface of the first standard test piece to obtain corresponding spectrum imaging data;
S50, preprocessing the spectral imaging data;
Step S60, shooting the surface of the first standard test piece to obtain common image data, identifying a pore area in the common image data through an image processing and analyzing method, and calculating the surface porosity of the concrete after freezing and thawing;
Step S70, performing a concrete compressive strength test on the first standard test piece to obtain compressive strength;
Step S80, constructing a database based on the compressive strength, the surface porosity and the spectral imaging data;
step S90, simplifying the database by a mathematical analysis method, and extracting characteristic wavelengths which have correlation with the compressive strength and the surface porosity;
Step S100, constructing an evaluation model based on the compressive strength, the surface porosity and the characteristic wavelength, wherein the evaluation model is used for obtaining corresponding reflectivity through the characteristic wavelength, and evaluating the compressive strength and the surface porosity of the concrete by the reflectivity;
S110, collecting spectrum data of the concrete surface of a tested member; and inputting the concrete surface spectrum data into the evaluation model, and outputting the compressive strength and the surface porosity of the tested member for evaluating whether the tested member is safe or not.
By the method, the mathematical model is constructed by utilizing the spectral curve characteristics of the concrete surface spectral data after related freeze thawing cycles, so that the durability evaluation of the freeze thawing environment of the tested member is finished, and the damage to the tested member is avoided; and moreover, by shooting a large-range surface spectrum image of the detected member, the durability evaluation of the detected member in a large-range freeze-thawing environment can be realized, and the overall safety of the concrete member or structure can be rapidly and accurately evaluated.
In one possible embodiment, the standard test piece may be manufactured according to specifications, for example, standard for ordinary concrete mechanical property test methods (GB/T50081-2019).
In one possible implementation mode, the standard test piece seals certain two opposite sides parallel to the direction of the steel bar and two sides perpendicular to the direction of the steel bar, and spray water in the subsequent freezing and thawing test is subjected to one-dimensional diffusion according to Fick's second law.
In a possible embodiment, the physical index may be determined experimentally according to a technical specification, specifically including: the information such as cube compressive strength, prism compressive strength, age, water-cement ratio, water content, porosity, type and mass ratio of concrete admixture and the like; the porosity refers to the proportion of the pore volume in the concrete structure to the total volume of the concrete structure;
In a possible implementation manner, the specific collection method of the physical index is as follows: and preparing a second standard test piece according to the materials, equipment and construction process of the first standard test piece and the corresponding concrete strength grade, and collecting the actual physical index of the second standard as the physical index of the first standard test piece.
In one possible embodiment, the second standard test piece is prepared for at least 3 pieces per concrete strength grade, which reduces the effect of test errors on the measured data.
In one possible embodiment, the concrete strength levels may be C20, C30, C40, C50, C60, etc., respectively, according to the usual concrete strength levels.
In a possible embodiment, the number of freeze thawing cycles is used for setting a plurality of reference groups according to the number of freeze thawing cycles in the freeze thawing test, including the number of freeze thawing cycles N and the multiplying power thereof, and at least comprises: 0. 0.2N, 0.4N, 0.6N, 0.8N and N.
In a possible embodiment, the specific step of calculating the number of freeze-thaw cycles in step S20 includes:
Step S20-1, collecting the cube compressive strength of the first standard test piece in step S10 And prismatic compressive Strength/>;
Step S20-2, constructing a calculation formula of the number of freeze thawing cycles N through a basic mathematical model of relative compressive strength and compressive strength of a non-freeze thawing concrete cube, wherein the specific formula can be as follows:
；
wherein, The prismatic compressive strength of the concrete after freezing and thawing is shown;
according to the technical specifications, the compressive strength loss rate in the termination condition of the freeze-thaw cycle test is taken as And/>And carrying out calculation by taking the ratio into the formula to obtain the freezing and thawing cycle times N.
In one possible embodiment, the rate of loss of compressive strength is determined to be 25% according to the freeze-thaw cycle test termination conditions given in technical Specification Standard test method for Long term Performance and durability of ordinary concrete (GB/T50082-2009).
In a possible implementation manner, the freeze-thawing test is an artificial climate freeze-thawing test, and the temperature in the laboratory is controlled to perform freeze-thawing, so that the actual freeze-thawing cycle process can be more truly reproduced compared with a quick freeze method, a slow freeze method, a single-sided freeze-thawing method and the like.
In a possible implementation manner, the step S30 specifically includes:
Step S30-1, black and white calibration: firstly, shooting a full white calibration image W, then shooting a full black calibration image S, and calculating a calibrated relative image R, wherein the specific formula can be as follows:
；
Wherein I represents an original image;
Step S30-2, setting scanning parameters: the height of the upper surface of the standard test piece from the camera lens is measured, parameters such as exposure time and scanning speed during spectrum image acquisition are calculated according to the height, and the scanning distance is determined according to the size of the surface to be detected of the standard test piece, so that the image of the whole surface to be detected of the standard test piece can be acquired.
In a possible embodiment, the method of preprocessing in step S50 includes: the prior methods such as multi-element scattering correction, standard normal variable transformation, scaling, smoothing algorithm, derivative algorithm, principal component filtering, independent component filtering, wavelet transformation and the like can select a proper preprocessing method according to actual conditions.
In a possible embodiment, the image processing and analyzing method in step S60 includes: edge detection, region growing, thresholding, morphological processing, etc.:
The edge detection method is characterized in that an edge detection operator (such as a Sobel operator, a Canny operator and the like) is used for extracting the edge position and the intensity in the common image data, and a pore area is judged; thus, the purpose of identifying the pore area can be achieved through the obvious edge characteristics of the pore area;
The region growing method uses a region growing algorithm to segment and identify the pore region in the common image data by selecting proper seed points and growing criteria; thus, the purpose of identifying the pore area can be achieved by utilizing the obvious color or texture characteristics of the pore area;
The threshold segmentation method is used for segmenting according to the color difference or the brightness difference between the pore area and the material area in the common image data through a preset threshold value to obtain the pore area; therefore, the purpose of identifying the pore region can be achieved by utilizing the obvious contrast difference between the pore region and the material region;
The morphological processing method removes noise of the pore region in the normal image data through morphological operations such as expansion, corrosion, open operation, and close operation, so as to obtain a more accurate pore region.
In a possible embodiment, in the step S60, the calculation formula of the surface porosity may be:
；
the common image area represents the area of the tested surface of the first standard test piece in the common image data;
therefore, the proportion of the occupied area of the pore area can be used as the surface porosity of the first standard test piece, and the calculation is facilitated by matching with the image processing and analysis method.
In one possible embodiment, the porosity of the surface is verified by the porosity to remove abnormal noise data generated in the image processing and analysis method, so as to facilitate optimization of parameters in the image processing and analysis method.
In a possible embodiment, the step S70 is performed according to the standard of the ordinary concrete mechanical property test method (GB/T50081-2019).
In a possible implementation manner, the database in the step S80 specifically includes first standard test pieces with different concrete strength levels, and after undergoing different freeze thawing times, the first standard test pieces have one-to-one correspondence among compressive strength, surface porosity and spectrum curves.
In a possible embodiment, the mathematical analysis method in step S90 includes a correlation coefficient method, a weight coefficient method, a principal component analysis method, a band ratio, a genetic algorithm, a stepwise regression method, etc., by which characteristic wavelengths having a strong correlation with the compressive strength and the surface porosity of concrete can be obtained.
In one possible embodiment, step S100 includes: dividing the data in the database into a training set, a verification set and a test set according to the proportion of 70%, 15% and 15%, and taking the compressive strength and the surface porosity as labels; the data is standardized by using a standardized method such as z-score or min-max scaling, so that the model training process is more stable; training, verifying and testing a neural network model, such as a one-dimensional convolutional neural network (1D-CNN), to obtain an assessment model, thereby establishing a mathematical model between the compressive strength and the surface porosity of the concrete and the spectral curve characteristics.
In a possible implementation manner, the database may further include freeze thawing times, physical indexes, and the like, so that an assessment model including any of the above items as an assessment result may be constructed according to actual requirements.
Based on the same inventive concept, the application also provides a concrete structure freeze thawing environment durability evaluation system, which comprises a data receiving module, a data processing module and a result generating module:
The data receiving module is used for receiving the spectrum data of the concrete surface of the tested member;
the data processing module comprises a database, a model unit and an evaluation unit:
The database stores the compressive strength, the surface porosity and the spectral imaging data of the standard test piece;
the model unit simplifies the database through a mathematical analysis method, extracts characteristic wavelengths related to the compressive strength and the surface porosity, constructs an evaluation model, is used for obtaining corresponding reflectivity through the characteristic wavelengths, and evaluates the compressive strength and the surface porosity of the concrete through the reflectivity;
The evaluation unit calls the evaluation model, and inputs the concrete surface spectrum data of the tested member to obtain the compressive strength and the surface porosity of the concrete;
and the result generation module is used for outwards generating the compressive strength and the surface porosity of the concrete.
In a third aspect, based on the same inventive concept, the application further provides a concrete structure freeze-thaw durability assessment device, which comprises a processor, a memory and a bus, wherein the memory stores instructions and data read by the processor, the processor is used for calling the instructions and the data in the memory to execute the concrete structure freeze-thaw durability assessment method, and the bus is connected with all functional components and used for transmitting information.
By adopting the technical scheme, the invention has the following beneficial effects:
According to the method, the system and the device for evaluating the durability of the freeze thawing environment of the concrete structure, which are provided by the invention, the detection is carried out based on the spectral image, and the detected component or structure is not damaged; after the construction of the assessment model is completed, the method only needs to collect the spectrum image of the tested member, and finishes the durability assessment of the whole structure of the concrete according to the image data, so that the method is simple and convenient to operate, the assessment period can be greatly shortened, and the detection efficiency can be improved; according to the technical scheme, by identifying the spectral curve characteristics of the standard test piece under different freeze thawing times, the surface porosity and compressive strength of the material can be accurately detected, compared with the traditional method, the method is more accurate, and the identification and evaluation are mainly carried out through machine vision, so that errors are not introduced; according to the scheme, an evaluation model of the comprehensive index can be constructed according to actual requirements, and comprehensive data support is provided for evaluating the durability of the freeze thawing environment of the concrete structure.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings which are required in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are some embodiments of the invention and that other drawings may be obtained from these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method for evaluating the durability of a concrete structure in a freeze-thawing environment according to an embodiment of the present invention;
FIG. 2 is a flowchart of a specific method for calculating the number of freeze/thaw cycles in step S20 of FIG. 1;
FIG. 3 is a flowchart illustrating a specific method of step S30 in FIG. 1;
fig. 4 is a system diagram for evaluating the durability of a freeze-thawing environment of a concrete structure according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
In order to facilitate understanding of the following embodiments, the inventive concept of the present application is briefly described as follows:
Aiming at the technical problems in the background art, the application takes into consideration that a spectrum camera (such as a near infrared hyperspectral camera) is used for collecting a spectrum image of the surface of a detected concrete (such as silicate concrete) member, and the freeze thawing environment durability assessment is carried out by carrying out machine identification on spectrum curve characteristics related to the surface porosity and compressive strength in the spectrum image.
The standard test piece is subjected to a freeze thawing cycle test and a spectrum image is acquired and used as a data source of a database, so that the comparability of the evaluation standard is ensured; and then, the spectral curve characteristics in the database are screened, and neural network training is carried out on the basis of the spectral curve characteristics, so that the reliability of the assessment model is ensured.
The invention is further illustrated with reference to specific embodiments.
It should be further noted that the following specific examples or embodiments are a series of optimized arrangements of the present invention for further explaining specific summary, and these arrangements may be used in combination or in association with each other.
Embodiment one:
as shown in fig. 1, the method for evaluating the durability of the freeze-thawing environment of the concrete structure provided by the embodiment comprises the following steps:
S10, preparing a plurality of groups of first standard test pieces with different concrete strength grades and different freeze thawing times by adopting the same batch of materials, equipment and construction process, and collecting physical indexes of the first standard test pieces;
The appearance of the first standard test piece is a cube; the specific size of the first standard test piece can be set as follows ；
The first standard test piece seals certain two opposite side surfaces parallel to the direction of the steel bar and two side surfaces perpendicular to the direction of the steel bar, and spray water in a subsequent freezing and thawing test is subjected to one-dimensional diffusion according to Fick second law;
The physical index can be tested according to technical specifications, and specifically comprises the following steps: the information such as cube compressive strength, prism compressive strength, age, water-cement ratio, water content, porosity, type and mass ratio of concrete admixture and the like; the porosity refers to the proportion of the pore volume in the concrete structure to the total volume of the concrete structure;
the physical index specific acquisition method comprises the following steps: preparing a second standard test piece according to the materials, equipment and construction process of the first standard test piece and the corresponding concrete strength grade, and collecting the actual physical index of the second standard as the physical index of the first standard test piece;
at least 3 second standard test pieces are prepared for each concrete strength grade, so that the influence of test errors on measured data can be reduced;
The concrete strength grades can be C20, C30, C40, C50 and C60 according to the common concrete strength grade;
The freeze thawing times are used for setting a plurality of reference groups according to the freeze thawing cycle times in the freeze thawing test, wherein the reference groups comprise the freeze thawing cycle times N and multiplying power thereof, and the freeze thawing test at least comprises: 0. 0.2N, 0.4N, 0.6N, 0.8N and N;
Step S20, judging the compressive strength and physical index of the concrete with the structure losing the bearing capacity according to the technical specifications, calculating the number of freeze thawing cycles, and performing a freeze thawing test on the first standard test piece; as shown in fig. 2, the specific steps for calculating the number of freeze-thaw cycles include:
Step S20-1, collecting the cube compressive strength of the first standard test piece in step S10 And prismatic compressive Strength/>;
Step S20-2, constructing a calculation formula of the number of freeze thawing cycles N through a basic mathematical model of relative compressive strength and compressive strength of a non-freeze thawing concrete cube, wherein the specific formula can be as follows:
；
wherein, The prismatic compressive strength of the concrete after freezing and thawing is shown;
According to the standard of the test method for the long-term performance and the durability of common concrete (GB/T50082-2009), the termination condition of the freeze thawing cycle test is given in the technical specification: the loss rate of compressive strength reaches 25 percent, and the freezing and thawing cycle times N are obtained by carrying the calculation;
The freeze thawing test is an artificial climate freeze thawing test, and the temperature in a laboratory is controlled to perform freeze thawing, so that the actual freeze thawing cycle process can be more truly reproduced compared with a quick freezing method, a slow freezing method, a single-sided freeze thawing method and the like;
The temperature range of freezing and thawing in the test method standard of the long-term performance and the durability of common concrete (GB/T50082-2009) is defined as thawing at 15-20 ℃ and freezing at-20-15 ℃. In view of this, the maximum value of the melting temperature of the artificial climate freeze-thawing test is set to 15 ℃ and the minimum value of the freezing temperature is set to-17 ℃; the specific freeze-thawing control time distribution process comprises the following steps:
cooling from 15 deg.C to-17 deg.C for 2 hr;
freezing, wherein the temperature is kept at-17 ℃ and the time is 2 hours;
thawing, namely raising the temperature from-17 ℃ to 15 ℃ and taking 0.5 hour;
Melting, namely, the temperature is kept at 15 ℃ and takes 1 hour;
One cycle period was 5.5 hours;
Spraying, namely spraying water for 1 minute, wherein the interval is 2 minutes, and spraying water for 5 times in one cycle period takes 0.25 hour (internal time);
when the cycle period reaches the calculated freeze-thawing cycle times, ending the test;
if the freezing and thawing cycle times are decimal, rounding upwards;
Step S30, a near infrared hyperspectral system is built by a near infrared hyperspectral camera, as shown in fig. 3, specifically including:
step S30-1, black and white calibration: firstly, scanning and shooting a standard white board to obtain a full white calibration image W, then covering a lens cover to obtain a full black calibration image S, and calculating a calibrated relative image R, wherein the specific formula can be as follows:
；
Wherein I represents an original image;
Step S30-2, setting scanning parameters: the method comprises the steps of placing a first standard test piece on an electric displacement acquisition platform, measuring the height of the upper surface of the first standard test piece from a hyperspectral CCD camera lens, calculating parameters such as exposure time, scanning speed and the like during spectrum image acquisition according to the height, and determining a scanning distance according to the size of a surface to be detected of the first standard test piece so as to ensure that an image of the whole surface to be detected of the first standard test piece can be acquired;
Step S40, performing near infrared hyperspectral scanning on the surface of the first standard test piece to obtain corresponding spectral imaging data;
step S50, preprocessing the spectral imaging data, specifically including: the prior methods such as multi-element scattering correction, standard normal variable transformation, scaling, smoothing algorithm, derivative algorithm, principal component filtering, independent component filtering, wavelet transformation and the like can select a proper preprocessing method according to actual conditions;
Step S60, shooting the surface of the first standard test piece through a high-resolution camera or a scanner to obtain common image data, identifying a pore area in the common image data through an image processing and analyzing method, and calculating the surface porosity of the concrete after freeze thawing;
the image processing and analyzing method specifically comprises the following steps: edge detection, region growing, thresholding, and morphological processing:
the edge detection method is characterized in that an edge detection operator (Sobel operator and Canny operator) is used for extracting the edge position and the intensity in the common image data, and a pore area is judged; thus, the purpose of identifying the pore area can be achieved through the obvious edge characteristics of the pore area;
The region growing method uses a region growing algorithm to segment and identify the pore region in the common image data by selecting proper seed points and growing criteria; thus, the purpose of identifying the pore area can be achieved by utilizing the obvious color or texture characteristics of the pore area;
The threshold segmentation method is used for segmenting according to the color difference or the brightness difference between the pore area and the material area in the common image data through a preset threshold value to obtain the pore area; therefore, the purpose of identifying the pore region can be achieved by utilizing the obvious contrast difference between the pore region and the material region;
The morphological processing method removes noise of the pore region in the common image data through morphological operations such as expansion, corrosion, open operation and close operation so as to obtain a more accurate pore region;
A proper image processing and analyzing method can be selected according to the specific condition of the common image data;
The calculation formula of the surface porosity can be:
；
the common image area represents the area of the tested surface of the first standard test piece in the common image data;
Therefore, the proportion of the occupied area of the pore area can be used as the surface porosity of the first standard test piece, and the calculation is facilitated by matching with the image processing and analysis method;
The surface porosity is verified through the porosity so as to remove abnormal noise data generated in the image processing and analyzing method, and parameters in the image processing and analyzing method are convenient to optimize and adjust;
step S70, performing a concrete compressive strength test on the first standard test piece according to the standard of a common concrete mechanical property test method (GB/T50081-2019), and measuring compressive strength;
step S80, constructing a database based on the compressive strength, the surface porosity and the spectrum imaging data, wherein the database specifically comprises first standard test pieces with different concrete strength grades, and the compressive strength, the surface porosity and the spectrum curve of the first standard test pieces have one-to-one correspondence after being subjected to different freeze thawing times;
step S90, simplifying the database by a mathematical analysis method, and extracting characteristic wavelengths which have correlation with the compressive strength and the surface porosity;
Theoretical analysis and compressive strength and surface porosity have characteristic wavelength of correlation:
Under the action of freeze thawing circulation, internal defects of the concrete start to sprout, expand, cross and gradually accumulate together, so that the concrete body is expanded and the structure is deteriorated, thereby further causing the performance attenuation of the concrete and even cracking and destruction;
For the concrete freeze-thaw failure mechanism, including: hydrostatic pressure hypothesis, osmotic pressure hypothesis, crystallization pressure hypothesis, etc., all of which describe freeze-thaw failure mechanisms: the more the freeze thawing cycle times are, the larger the porosity of the concrete is, and the smaller the compressive strength of the concrete is;
near infrared light is electromagnetic radiation which can penetrate through the surface of concrete, a near infrared light source irradiates the surface of the concrete, reflected light intensity or transmitted light intensity is measured, and characteristic wavelength related to the porosity of the surface of the concrete can be obtained;
meanwhile, as the apertures with different sizes have different absorbance, the reflectivity at the characteristic wavelength is affected, the reflectivity at the characteristic wavelength corresponding to the surface porosity is determined later, and the compressive strength of the concrete after freeze thawing cycle can be determined;
the mathematical analysis method comprises a correlation coefficient method, a weight coefficient method, a principal component analysis method, a wave band ratio, a genetic algorithm, a stepwise regression method and the like, and characteristic wavelength with stronger correlation with the compressive strength and the surface porosity of the concrete can be obtained through the methods;
Step S100, constructing an evaluation model based on the compressive strength, the surface porosity and the characteristic wavelength, wherein the evaluation model is used for obtaining corresponding reflectivity through the characteristic wavelength and evaluating the compressive strength and the surface porosity of the concrete through the reflectivity, and specifically comprises the following steps: dividing the data in the database into a training set, a verification set and a test set according to the proportion of 70%, 15% and 15%, and taking the compressive strength and the surface porosity as labels; the data is standardized by using a z-score or min-max scaling standardization method, so that the model training process is more stable; training, verifying and testing a one-dimensional convolutional neural network (1D-CNN) to obtain an evaluation model, thereby establishing a mathematical model between the compressive strength and the surface porosity of the concrete and the spectral curve characteristics;
Furthermore, the database can also comprise freeze thawing times, physical indexes and the like, so that an assessment model comprising any item as an assessment result can be constructed according to actual requirements;
S110, collecting spectrum data of the concrete surface of a tested member; and inputting the concrete surface spectrum data into the evaluation model, and outputting the compressive strength and the surface porosity of the tested member for evaluating whether the tested member is safe or not.
Embodiment two:
As shown in fig. 4, the embodiment provides a system for evaluating the durability of a freeze thawing environment of a concrete structure, which comprises a data receiving module, a data processing module and a result generating module:
The data receiving module is used for receiving the spectrum data of the concrete surface of the tested member;
the data processing module comprises a database, a model unit and an evaluation unit:
The database stores the compressive strength, the surface porosity and the spectral imaging data of the standard test piece;
the model unit simplifies the database through a mathematical analysis method, extracts characteristic wavelengths related to the compressive strength and the surface porosity, constructs an evaluation model, is used for obtaining corresponding reflectivity through the characteristic wavelengths, and evaluates the compressive strength and the surface porosity of the concrete through the reflectivity;
The evaluation unit calls the evaluation model, and inputs the concrete surface spectrum data of the tested member to obtain the compressive strength and the surface porosity of the concrete;
and the result generation module is used for outwards generating the compressive strength and the surface porosity of the concrete.
Embodiment III:
The embodiment provides a concrete structure freeze-thawing environment durability assessment device, which comprises a processor, a memory and a bus, wherein the memory stores instructions and data read by the processor, the processor is used for calling the instructions and the data in the memory so as to execute the concrete structure freeze-thawing environment durability assessment method, and the bus is connected with all functional components and used for transmitting information.
In yet another embodiment, the present solution may be implemented by means of an apparatus, which may include corresponding modules performing each or several steps of the above-described embodiments. A module may be one or more hardware modules specifically configured to perform the respective steps, or be implemented by a processor configured to perform the respective steps, or be stored within a computer-readable medium for implementation by a processor, or be implemented by some combination.
The processor performs the various methods and processes described above. For example, method embodiments in the present solution may be implemented as a software program tangibly embodied on a machine-readable medium, such as a memory. In some embodiments, part or all of the software program may be loaded and/or installed via memory and/or a communication interface. One or more of the steps of the methods described above may be performed when a software program is loaded into memory and executed by a processor. Alternatively, in other embodiments, the processor may be configured to perform one of the methods described above in any other suitable manner (e.g., by means of firmware).
The device may be implemented using a bus architecture. The bus architecture may include any number of interconnecting buses and bridges depending on the specific application of the hardware and the overall design constraints. The bus connects together various circuits including one or more processors, memories, and/or hardware modules. The bus may also connect various other circuits such as peripherals, voltage regulators, power management circuits, external antennas, and the like.
The bus may be an industry standard architecture (ISA, industry Standard Architecture) bus, a peripheral component interconnect (PCI, PERIPHERAL COMPONENT) bus, or an extended industry standard architecture (EISA, extended Industry Standard Component) bus, etc., and may be classified as an address bus, a data bus, a control bus, etc.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (4)
1. A method for evaluating the durability of a concrete structure in a freeze-thawing environment is characterized by comprising the following steps:
Step S10, preparing a plurality of groups of first standard test pieces in a classified mode based on concrete evaluation conditions, and collecting physical indexes of the first standard test pieces; the concrete evaluation conditions comprise concrete strength grade and freeze thawing times, wherein the freeze thawing times are used for setting a plurality of reference groups according to the freeze thawing cycle times in a freeze thawing test, and the reference groups comprise the freeze thawing cycle times N and multiplying power thereof, and at least comprise the following components: 0. 0.2N, 0.4N, 0.6N, 0.8N and N; the physical index specifically comprises: cubic compressive strength, prismatic compressive strength, age, water-cement ratio, water content, porosity and types and mass proportions of concrete admixture; the porosity refers to the proportion of the pore volume in the concrete structure to the total volume of the concrete structure;
step S20, judging the compressive strength and physical index of the concrete with the structure losing the bearing capacity according to the technical specifications, calculating the number of freeze thawing cycles, and performing a freeze thawing test on the first standard test piece;
the specific steps for calculating the freeze-thawing cycle times comprise:
Step S20-1, collecting the cube compressive strength of the first standard test piece in step S10 Compressive strength of prismatic body;
S20-2, constructing a calculation formula of the number of freeze thawing cycles N through a basic mathematical model of relative compressive strength and compressive strength of a non-freeze thawing concrete cube, wherein the concrete formula is as follows:
；
wherein, The prismatic compressive strength of the concrete after freezing and thawing is shown;
according to the technical specifications, the compressive strength loss rate in the termination condition of the freeze-thaw cycle test is taken as And/>Carrying out the calculation of the above formula to obtain the number N of freeze-thawing cycles;
The freeze thawing test is an artificial climate freeze thawing test, and specifically comprises the following steps: the maximum value of the melting temperature is set to 15 ℃, and the minimum value of the freezing temperature is set to-17 ℃; the specific freeze-thawing control time distribution process comprises the following steps:
cooling from 15 deg.C to-17 deg.C for 2 hr;
freezing, wherein the temperature is kept at-17 ℃ and the time is 2 hours;
thawing, namely raising the temperature from-17 ℃ to 15 ℃ and taking 0.5 hour;
Melting, namely, the temperature is kept at 15 ℃ and takes 1 hour;
One cycle period was 5.5 hours;
Spraying, namely spraying water for 1 minute at intervals of 2 minutes, wherein the total spraying time is 5 times in one cycle period;
when the cycle period reaches the calculated freeze-thawing cycle times, ending the test;
if the freezing and thawing cycle times are decimal, rounding upwards;
S30, constructing a spectrum system through a spectrum camera;
step S40, performing spectrum scanning on the surface of the first standard test piece to obtain corresponding spectrum imaging data;
S50, preprocessing the spectral imaging data;
step S60, shooting the surface of the first standard test piece to obtain common image data, identifying a pore area in the common image data through an image processing and analyzing method, and calculating the surface porosity of the concrete after freezing and thawing; the calculation formula of the surface porosity is as follows:
；
The common image area represents the area of the tested surface of the first standard test piece in the common image data;
Step S70, performing a concrete compressive strength test on the first standard test piece to obtain compressive strength;
Step S80, constructing a database based on the compressive strength, the surface porosity and the spectral imaging data;
step S90, simplifying the database by a mathematical analysis method, and extracting characteristic wavelengths which have correlation with the compressive strength and the surface porosity;
Step S100, constructing an evaluation model based on the compressive strength, the surface porosity and the characteristic wavelength, wherein the evaluation model is used for obtaining corresponding reflectivity through the characteristic wavelength, and evaluating the compressive strength and the surface porosity of the concrete by the reflectivity;
S110, collecting spectrum data of the concrete surface of a tested member; and inputting the concrete surface spectrum data into the evaluation model, and outputting the compressive strength and the surface porosity of the tested member for evaluating whether the tested member is safe or not.
2. The method of claim 1, wherein the compressive strength loss rate is 25%.
3. A system for evaluating the durability of a freeze thawing environment of a concrete structure by adopting the method as claimed in any one of claims 1-2, which is characterized by comprising a data receiving module, a data processing module and a result generating module:
The data receiving module is used for receiving the spectrum data of the concrete surface of the tested member;
the data processing module comprises a database, a model unit and an evaluation unit:
The database stores the compressive strength, the surface porosity and the spectral imaging data of the standard test piece;
the model unit simplifies the database through a mathematical analysis method, extracts characteristic wavelengths related to the compressive strength and the surface porosity, constructs an evaluation model, is used for obtaining corresponding reflectivity through the characteristic wavelengths, and evaluates the compressive strength and the surface porosity of the concrete through the reflectivity;
The evaluation unit calls the evaluation model, and inputs the concrete surface spectrum data of the tested member to obtain the compressive strength and the surface porosity of the concrete;
and the result generation module is used for outwards generating the compressive strength and the surface porosity of the concrete.
4. A device for evaluating the durability of a concrete structure in a freeze thawing environment, comprising a processor, a memory and a bus, wherein the memory stores instructions and data read by the processor, the processor is used for calling the instructions and data in the memory to execute the method as claimed in any one of claims 1-2, and the bus is connected with each functional component and is used for transmitting information.
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