A method for generating a tensile strength distribution of a concrete dog bone test piece

Abstract

The application discloses a method for generating a tensile strength distribution of a concrete dog bone test piece, comprising the following steps: measuring an initial defect distribution of a real concrete dog bone test piece; calculating a tensile strength distribution of the concrete dog bone test piece based on the defect distribution; and generating a simulated tensile strength distribution of the concrete dog bone test piece. Compared with the prior art, the application has the beneficial effects that the characterized tensile strength distribution reflects the defect law of the dog bone test piece in the concrete pouring process, the tensile behavior of the concrete dog bone test piece is more accurately predicted, and thus the correctness of the structural analysis is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of structural engineering, and particularly relates to a method for generating tensile strength distribution of a concrete dog bone specimen. BACKGROUND

[0002] The concrete dog bone specimen is generally used for tensile behavior test of high ductility concrete, and includes a middle gauge section and two end clamping sections. The middle gauge section with equal cross section is studied in the test. The high ductility concrete has the characteristics of multiple crack opening and strain hardening, and the tensile mechanical properties and the cracking behavior of the material are closely related. In the study of the tensile behavior of the material, the tensile strength distribution of the concrete dog bone specimen needs to be introduced. The reasonable tensile strength distribution of the concrete dog bone specimen has a great influence on the results of the subsequent cracking behavior study, and is crucial to the design of the high ductility concrete structure. At present, the Weibull distribution is generally used to randomly generate the tensile strength distribution for introduction. However, the tensile strength distribution generated by this method is irrelevant to the pouring defects of the actual specimen, and the introduced tensile strength distribution cannot represent the strength distribution characteristics of the actual specimen, which further leads to inaccurate cracking behavior research results, affects the reliability of the structure analysis, and brings difficulties to the design of the high ductility concrete structure. SUMMARY

[0003] The present application provides a method for generating tensile strength distribution of a concrete dog bone specimen, which solves the problems in the prior art that the existing method for generating tensile strength distribution of a concrete dog bone specimen is irrelevant to the pouring defects of the actual specimen, the introduced tensile strength distribution cannot represent the strength distribution characteristics of the actual specimen in the Weibull distribution random generation of tensile strength, which further leads to inaccurate cracking behavior research results, affects the reliability of the structure analysis, and brings difficulties to the design of the high ductility concrete structure.

[0004] TECHNICAL SOLUTION

[0005] A method for generating tensile strength distribution of a concrete dog bone specimen, comprising the following steps:

[0006] Step 1, measuring the initial defect distribution of the real concrete dog bone specimen:

[0007] Step 1.1, obtaining slice images of the real concrete dog bone specimen by CT scanning;

[0008] Step 1.2, reconstructing the defect distribution of the real concrete dog bone specimen based on the slice images;

[0009] Step 2, calculating the tensile strength distribution of the real concrete dog bone specimen based on the defect distribution:

[0010] Step 2.1, calculating the tensile strength distribution of the real concrete dog bone specimen;

[0011] Step 2.2, constructing the tensile strength spectrum of the real concrete dog bone specimen;

[0012] Step 3, generating the tensile strength distribution of the simulated concrete dog bone specimen:

[0013] Step 3.1, establishing the tensile strength distribution model of the dog bone specimen of the concrete based on the batch real specimen measurement;

[0014] Step 3.2, generating the tensile strength spectrum amplitude of the specimen based on the tensile strength distribution model;

[0015] Step 3.3, reconstructing the tensile strength distribution of the simulated specimen according to the generated simulated specimen tensile strength spectrum.

[0016] As a preferred technical solution of the present application: the step 1 real concrete dog bone specimen initial defect distribution measurement is specifically: obtaining high-precision internal defect distribution slice images of the real concrete dog bone specimen by nano-CT scanning technology, using Otsu threshold method to binarize the image, and using maximum connected domain algorithm to obtain the measured maximum defect distribution of each section of the real concrete dog bone specimen.

[0017] As a preferred technical solution of the present application: the method of step 2, the tensile strength distribution calculation of the concrete dog bone specimen based on the defect distribution, is: according to the strength calculation algorithm obtained based on the principle of fracture mechanics and the measured maximum defect distribution of each section of the real concrete dog bone specimen, obtaining the cracking strength distribution of each section of the real concrete dog bone specimen, and describing the tensile strength of the real concrete dog bone specimen with the strength distribution spectrum of the specimen.

[0018] As a preferred technical solution of the present application: the strength α of each section of the real concrete dog bone specimen is:

[0019]

[0020] Wherein, c is the maximum defect size of the section; π is the circular constant; σ b is the fiber bridging stress; δ(X) is the crack opening displacement.

[0021] As a preferred technical solution of the present application: the distribution of the tensile strength of the specimen in the stress direction is inversely extended along the length direction of the specimen, the strength signal of the specimen is extended to a complete signal period, and the discrete Fourier transform is used on the extended defect signal to describe the tensile strength spectrum A(k) of the real concrete dog bone specimen:

[0022]

[0023] Wherein, k=0, 1, …, N-1, N is the total frequency number, and n is the nth frequency when summing. e is the natural logarithm, j is the imaginary unit; a is the cross-sectional strength; L is the length of the test piece.

[0024] As a preferred technical solution of the present application: the method for generating the tensile strength distribution of the simulated concrete dog bone test piece in step 3 is:

[0025] S1. According to the measurement results of the batch of real test pieces, the random distribution type and the corresponding statistical parameters of the real test piece strength spectrum are determined through statistical analysis and distribution test, and the dog bone test piece tensile strength distribution model of the concrete is established;

[0026] S2. According to the dog bone test piece tensile strength distribution model of the concrete, the simulated concrete dog bone test piece tensile strength spectrum amplitude with the same random distribution is generated;

[0027] S3. According to the strength spectrum, the tensile strength distribution of the simulated concrete dog bone test piece is calculated.

[0028] As a preferred technical solution of the present application: the method for generating the tensile strength distribution of the simulated concrete dog bone test piece in step 3 is:

[0029] According to the amplitude distribution characteristics of the established dog bone test piece tensile strength distribution model of the concrete, the same distribution of simulated amplitudes is randomly generated according to the random distribution and parameters of each frequency, to form the simulated concrete dog bone test piece tensile strength spectrum, and the higher frequency components generated without measurement are supplemented to obtain the supplemented defect amplitude spectrum X(k), and the inverse discrete Fourier transform is applied, that is, a group of tensile strength distribution x i (z) is obtained.

[0030]

[0031] Wherein, n=0, 1, …, N-1.

[0032] Beneficial effects:

[0033] Compared with the prior art, the present application has the following advantages:

[0034] 1. The tensile strength distribution generation method of the concrete dog bone test piece can describe and generate complex strength distribution through a small number of strength amplitudes.

[0035] 2. The tensile strength distribution of the actual test piece can be extracted with high precision, non-damage and automation, and a large amount of manpower can be saved.

[0036] 3. It has the characteristics of high efficiency and reality, and can generate a large number of dog bone test piece tensile strength distribution samples conforming to the real strength distribution mode based on a small number of real test piece defects in a short time.

[0037] 4. The application can replace the existing method for generating the tensile strength distribution of the concrete dog bone specimen, and further improve the reliability of the cracking behavior research and structural analysis of the high ductility concrete dog bone specimen;

[0038] 5. Compared with the prior art, the application can well reflect the continuous characteristics of the tensile strength distribution of the concrete dog bone specimen and the strong correlation with the defect distribution, and improve the application performance of the tensile strength distribution of the concrete in the simulation of the tensile behavior of the concrete. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without any creative labor under the premise of the drawings.

[0040] Figure 1 It is a flowchart of the method for generating the tensile strength distribution of the concrete dog bone specimen.

[0041] Figure 2 It is a CT scanning sectional image of the actual concrete dog bone specimen according to the method for generating the tensile strength distribution of the concrete dog bone specimen.

[0042] Figure 3 It is the result of the binaryzation processing of the CT scanning sectional image of the actual concrete dog bone specimen according to the method for generating the tensile strength distribution of the concrete dog bone specimen.

[0043] Figure 4 It is the calculation result of the defect distribution and the tensile strength distribution of the actual concrete dog bone specimen according to the method for generating the tensile strength distribution of the concrete dog bone specimen.

[0044] Figure 5 It is a tensile strength spectrum of the simulated concrete dog bone specimen and three specific embodiment graphs of the tensile strength distribution of the simulated concrete dog bone specimen generated by the method for generating the tensile strength distribution of the concrete dog bone specimen, wherein Fig. a is a tensile strength spectrum of the simulated concrete dog bone specimen and a tensile strength distribution graph of the simulated concrete dog bone specimen of embodiment 1, Fig. b is a tensile strength spectrum of the simulated concrete dog bone specimen and a tensile strength distribution graph of the simulated concrete dog bone specimen of embodiment 2, and Fig. c is a tensile strength spectrum of the simulated concrete dog bone specimen and a tensile strength distribution graph of the simulated concrete dog bone specimen of embodiment 3.

[0045] Figure 6It is the effect comparison chart of the present application and prior art, wherein figure a is the tensile strength distribution of a concrete dog bone specimen based on the prior art, and figure b is the tensile strength distribution of a concrete dog bone specimen based on the concrete dog bone specimen tensile strength distribution generation method provided by the present application. DETAILED DESCRIPTION

[0046] To make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0047] A concrete dog bone specimen tensile strength distribution generation method,

[0048] As Figure 1 shown, a concrete dog bone specimen tensile strength distribution generation method comprises the following steps:

[0049] Step 1, measurement of initial defect distribution of a real concrete dog bone specimen:

[0050] Step 1.1, CT scanning to obtain slice images of the real concrete dog bone specimen;

[0051] Step 1.2, reconstruction of the defect distribution of the real concrete dog bone specimen based on the slice images;

[0052] Step 2, calculation of the tensile strength distribution of the real concrete dog bone specimen based on the defect distribution:

[0053] Step 2.1, calculation of the tensile strength distribution of the real concrete dog bone specimen;

[0054] Step 2.2, construction of the tensile strength spectrum of the real concrete dog bone specimen;

[0055] Step 3, generation of the tensile strength distribution of the simulated concrete dog bone specimen:

[0056] Step 3.1, establishment of a tensile strength distribution model of the concrete dog bone specimen based on measurement of a batch of real specimens;

[0057] Step 3.2, generation of the tensile strength spectrum amplitude of the specimen based on the tensile strength distribution model;

[0058] Step 3.3, reconstruction of the tensile strength distribution of the simulated specimen according to the generated simulated specimen tensile strength spectrum.

[0059] The step 1 real concrete dog bone specimen initial defect distribution measurement, in particular, the real concrete dog bone specimen initial defect distribution measurement described in the embodiment, through the nanometer CT scanning technology, the high-precision internal defect distribution slice image of the real concrete dog bone specimen is obtained, the Otsu threshold method is used to binarize the image, and the maximum connected domain algorithm is used to obtain the maximum defect distribution of each section of the real concrete dog bone specimen.

[0060] First, the initial defect distribution of the real specimen is measured;

[0061] As shown in Figure 2 ,the initial defect distribution of the real existing concrete dog bone specimen gauge section is collected using the nanometer CT technology, and the slice defect distribution image in 3 is obtained. The Otsu threshold method is used to binarize each cross-sectional CT image, and the black and white defect image in Figure 2 is obtained, which separates the defect pixels and the concrete pixels. The maximum connected domain algorithm is applied to the binarized image to obtain the area of each defect on the section, and the maximum defect is retained as the section defect size c. Figure 3

[0062] Specifically, as shown in Figure 4 , the concrete dog bone specimen tensile strength distribution calculation based on defect distribution described in the embodiment is obtained according to the strength calculation algorithm obtained from the principle of fracture mechanics and the real measured maximum defect distribution of each section of the real concrete dog bone specimen, and the cracking strength distribution of each section of the real concrete dog bone specimen is obtained. The tensile strength of the real concrete dog bone specimen is described by the strength distribution spectrum of the specimen.

[0063] First, the strength calculation algorithm obtained from the principle of fracture mechanics:

[0064] For each section, the strength calculation algorithm obtained from the principle of fracture mechanics is used to obtain the dashed line in Figure 4 , the tensile strength of the section α:

[0065]

[0066] Where c is the maximum defect size of the section; π is the circular constant; σ b is the fiber bridging stress; δ(X) is the crack opening displacement;

[0067] Second, the strength spectrum of the specimen is calculated. The distribution of the tensile strength of the specimen in the stress direction is reversed along the length direction of the specimen, the tensile strength signal of the specimen is extended to a complete signal period, and the discrete Fourier transform is used for the defect signal after extension, and the tensile strength spectrum A(k) of the specimen for describing the tensile strength of the real concrete dog bone specimen is obtained:

[0068]

[0069] wherein k = 0, 1, …, N-1, N is the total frequency number, and n is the nth frequency in summation; e is a natural logarithm, j is an imaginary unit, a is a cross-sectional strength, and L is a specimen length.

[0070] Statistical analysis and random distribution discrimination are performed on the amplitude of the tensile strength of the actual measured concrete dog bone specimen, so as to establish the tensile strength distribution model of the concrete dog bone specimen. The tensile strength distribution of the real concrete dog bone specimen is measured by using the technology, so that high-precision, non-destructive and automatic tensile strength distribution extraction of the specimen can be realized, and continuous acquisition of the tensile strength of the specimen based on the real measured defect distribution can be realized.

[0071] Further, as shown in Figure 5 The tensile strength distribution of the simulated concrete dog bone specimen is generated according to the tensile strength distribution model of the concrete dog bone specimen, the tensile strength spectrum amplitude of the simulated concrete dog bone specimen with the same random distribution is generated, and the tensile strength distribution of the simulated concrete dog bone specimen is calculated according to the defect spectrum.

[0072] Figure 5 The steps 1.1-3.1 of the three groups of examples are consistent, different tensile strength spectrum amplitudes are generated in step 3.2, and different tensile strength distributions are reconstructed in step 3.3. Each specific example includes the simulated tensile strength spectrum of the concrete dog bone specimen generated according to the tensile strength distribution model of the concrete dog bone specimen in the example, and the simulated tensile strength distribution of the concrete dog bone specimen corresponding to the simulated tensile strength spectrum.

[0073] According to the amplitude distribution characteristics of the established tensile strength distribution model of the concrete dog bone specimen, the mean and variance of the strength amplitude of each frequency are statistically obtained, and normal distribution test is performed. If the test is passed, the strength amplitude of the frequency is described by using normal distribution; if not, other random distribution is used for test. According to the test results and statistical parameters, the simulated amplitude with the same distribution is randomly generated, the simulated tensile strength spectrum of the concrete dog bone specimen is constructed, the higher frequency components generated by the measurement are supplemented to obtain the supplemented strength amplitude spectrum X(k), and the inverse discrete Fourier transform is applied, so that a set of tensile strength distribution x i (z) is obtained.

[0074]

[0075] wherein n = 0, 1, …, N-1.

[0076] Figure 6The present application is compared with the prior art in the effect diagram, wherein figure a is the tensile strength distribution of the concrete dog bone specimen based on the prior art, and figure b is the tensile strength distribution of the concrete dog bone specimen based on the concrete dog bone specimen tensile strength distribution generation method of the present application. The tensile strength distribution of the concrete dog bone specimen based on the concrete dog bone specimen tensile strength distribution generation method of the present application can well reflect the continuous characteristics of the tensile strength distribution of the concrete dog bone specimen and the strong correlation with the defect distribution, and improve the application performance of the tensile strength distribution of the concrete dog bone specimen in the simulation of the tensile behavior of the concrete.

[0077] The simulation of the tensile strength distribution of the concrete dog bone specimen generated by the present application has the characteristics of high efficiency and authenticity, and can improve the reliability of the current high-performance concrete cracking behavior research and structure analysis.

[0078] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for generating the tensile strength distribution of a concrete dog bone specimen, characterized in that, The method includes the following steps: Step 1, Measurement of initial defect distribution in real concrete dog bone specimens: Step 1.1: Obtain slice images of real concrete dog bone specimens using CT scans; Step 1.2: Reconstruct the defect distribution of the real concrete dog bone specimen based on the sliced ​​images; Step 2, Calculation of tensile strength distribution of real concrete dog bone specimens based on defect distribution: Step 2.1: Calculate the tensile strength distribution of the real concrete dog bone specimen; Step 2.2: Construct the tensile strength spectrum of a real concrete dog bone specimen; Step 3, generating the simulated tensile strength distribution of the concrete dog bone specimen: Step 3.1: Establish a tensile strength distribution model for dog bone specimens of this type of concrete based on batch measurements of real specimens; Step 3.2: Based on the tensile strength distribution model, generate the tensile strength spectrum amplitude of the specimen; Step 3.3: Reconstruct the tensile strength distribution of the simulated specimen based on the generated tensile strength spectrum of the simulated specimen; The method for calculating the tensile strength distribution of concrete dog bone specimens based on defect distribution in step 2 is as follows: based on the strength calculation algorithm obtained from the principle of fracture mechanics and the maximum defect distribution of each section of the actual concrete dog bone specimen, the cracking strength distribution of each section of the actual concrete dog bone specimen is obtained, and the tensile strength of the actual concrete dog bone specimen is described by the strength distribution spectrum of the specimen. The strength α of each section of the real concrete dog bone specimen is: Where c is the maximum defect size of the cross-section; π is pi; σ b δ(X) is the fiber bridging stress; δ(X) is the crack opening displacement. The distribution of tensile strength in the direction of force is extended backward along the length of the specimen, and the specimen strength signal is extended into a complete signal period. A discrete Fourier transform is then applied to the extended defect signal to describe the tensile strength spectrum A(k) of the real concrete dog bone specimen: Where k = 0, 1, ..., N-1, N is the total number of frequencies, and n is the nth frequency when summing; e is the natural logarithm, j is the imaginary unit; α is the cross-sectional strength; L is the specimen length; The method for generating the simulated tensile strength distribution of the concrete dog bone specimen in step 3 is as follows: S1. Based on the measurement results of batch real specimens, the random distribution type and corresponding statistical parameters of the strength spectrum of the test specimens are determined through statistical analysis and distribution test, and a tensile strength distribution model of dog bone specimens of this type of concrete is established. S2. Based on the tensile strength distribution model of the dog bone specimen of this type of concrete, generate the tensile strength spectrum amplitude of the simulated concrete dog bone specimen with the same random distribution; S3. Calculate the tensile strength distribution of the simulated concrete dog bone specimen based on the strength spectrum; Based on the tensile strength distribution model of dog bone specimens of this type of concrete, the method for generating simulated tensile strength spectrum amplitudes of dog bone specimens of concrete with the same random distribution is as follows: Based on the amplitude distribution characteristics of the established tensile strength distribution model of the concrete dog-bone specimen, simulated amplitudes with the same distribution are randomly generated according to the random distribution and parameters of each frequency, forming a simulated tensile strength spectrum of the concrete dog-bone specimen. Higher frequency components that were not measured are supplemented to obtain the supplemented strength amplitude spectrum X(k). Then, by applying the inverse discrete Fourier transform, the tensile strength distribution x of a set of cross-sections can be obtained. i (z): Where n = 0, 1, ..., N-1.

2. The method for generating tensile strength distribution of concrete dog bone specimens according to claim 1, characterized in that, The specific steps of step 1, measuring the initial defect distribution of the real concrete dog bone specimen, are as follows: obtaining a high-precision slice image of the internal defect distribution of the real concrete dog bone specimen using nano-CT scanning technology, binarizing the image using the Otsu thresholding method, and obtaining the maximum defect distribution of each section of the measured real concrete dog bone specimen using the maximum connected component algorithm.

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