Modified calculation method of ultrasonic velocity-based concrete damage based on poisson's ratio change
By introducing a fitting formula for the Poisson's ratio correction coefficient into concrete damage calculation, the calculation error caused by changes in Poisson's ratio is solved, achieving a simple and accurate damage assessment applicable to concrete members under axial compression or local compression.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG SCI-TECH UNIV
- Filing Date
- 2023-08-02
- Publication Date
- 2026-06-16
Smart Images
Figure CN117092219B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of concrete damage detection, and in particular relates to a method for correcting the calculation of ultrasonic-velocity-based concrete damage by taking into account changes in Poisson's ratio. Background Technology
[0002] The method of calculating damage variables using ultrasonic wave propagation velocity has advantages such as quick calculation and simple measurement. Based on damage and elastic wave theory, the commonly used formula for calculating damage using wave velocity is:
[0003]
[0004] Where: D is the damage variable; v is the ultrasonic wave propagation velocity of the material in its initial undamaged state. This represents the speed at which ultrasonic waves propagate through the material when it is damaged.
[0005] As can be seen from the relevant literature [1] and [2], the formula (1) uses the assumption that the Poisson's ratio is constant to simplify the calculation. However, under the condition that the actual Poisson's ratio of the material changes significantly, the damage calculation results will have theoretical errors.
[0006] On the other hand, if the change in Poisson's ratio is considered in damage calculation based on wave velocity, it is generally necessary to measure the change in Poisson's ratio of the material at the same time as measuring the change in wave velocity, and then calculate the Poisson's ratio correction coefficient according to elastic wave theory. The calculation process is cumbersome, which leads to difficulties in practical application.
[0007] [1]HOSEINI M.Effect of compressive loading on transport properties ofcement-based materials[D].Edmonton:University of Alberta,2013.
[0008] [2] Mao Zhenhao, Zhang Jicheng, Li Yuanqi, et al. Performance deterioration and microstructure of reactive powder concrete after high temperature [J]. Journal of Building Materials, 2022, 25(12):1225-1232.
[0009] [3]V Birtel,Mark P.Parameterised finite element modeling of RC beamshear failure[J].2006:95-108.
[0010] [4] Nie Jianguo, Wang Yuhang. Comparative study on concrete constitutive model in ABAQUS for simulating static behavior of structure [J]. Engineering Mechanics, 2013, 30(4): 59-67.
[0011] [5] Fang Zihu, Zhou Haijun, Lai Shaoying, Xie Qiang. Selection of ABAQUS stress-strain relationship for concrete [J]. Building Structures, 2014, (4): 719-721.
[0012] [6]ACI Committee.Building code requirements for structural concrete(ACI 318-08)and commentary[S].American Concrete Institute,2008.
[0013] [7]Fib model code for concrete structures 2010[S].Ernst&Sohn,Wiley,2013. Summary of the Invention
[0014] To address the aforementioned shortcomings, the present invention aims to provide a simple correction calculation method for ultrasonic velocity-based concrete damage that incorporates changes in Poisson's ratio. This method is applicable to ordinary plain concrete or reinforced concrete members that suffer damage under axial compression or localized compression. Based on the loading stress-Poisson's ratio correction coefficient fitting formula provided by the present invention, more accurate damage calculation values based on wave velocity can be obtained.
[0015] To achieve the above objectives, this invention provides a method for calculating ultrasonic-velocity concrete damage correction that takes into account changes in Poisson's ratio, comprising the following steps:
[0016] Step 1: Measure the ultrasonic velocity in the area of interest on the concrete member in the initial undamaged and damaged states using conventional methods.
[0017] Step 2: Estimate the average compressive stress in the measurement area based on the stress condition of the component;
[0018] Step 3: Calculate the Poisson's ratio correction factor using formula (3), and then substitute it into formula (2) to obtain the damage value of the concrete.
[0019]
[0020] Where: D is the damage variable; v is the ultrasonic wave propagation velocity of the material in its initial undamaged state. The ultrasonic wave propagation speed of the material under damaged conditions is α, which is the Poisson's ratio correction factor.
[0021]
[0022] in: σmax This represents the peak compressive stress in the concrete. The actual compressive stress value is represented by C1 to C3, which are coefficients.
[0023] Preferably, the ultrasonic velocity in step 1 includes longitudinal waves and transverse waves;
[0024] For the longitudinal wave case, C1 to C3 in step 3 are taken as follows: C1 = -0.0000114, C2 = 0.104, C3 = 0.984;
[0025] For the case of shear waves, C1 to C3 in step 3 are set as follows: C1 = 0.0000341, C2 = 0.125, C3 = 1.060.
[0026] Preferably, the corrected starting stress in step 3 is 0.3σ. max .
[0027] The beneficial effects of this invention are: by introducing an approximate fitting function calculation formula based on experimental data with a Poisson's ratio correction coefficient, errors caused by variations in Poisson's ratio can be conveniently corrected in concrete damage calculations based on wave velocity. This method facilitates actual measurements and reduces theoretical errors in calculations. Attached Figure Description
[0028] Figure 1 - Schematic diagram of experimental data fitting for Poisson's ratio correction coefficient (longitudinal wave);
[0029] Figure 2 - Schematic diagram of experimental data fitting for Poisson's ratio correction coefficient (transverse wave);
[0030] Figure 3 Verification test loading curve;
[0031] Figure 4 Schematic diagram of the loading device for the column specimen;
[0032] Figure 5 Comparison of horizontal damage values;
[0033] Figure 6 Comparison of axial damage values;
[0034] The components include: 1. transducer, 2. transducer fixture, 3. press plate, and 4. hydraulic controller. Detailed Implementation
[0035] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings.
[0036] According to relevant literature [3]-[7], the elastic limit compressive stress of concrete can be taken as the peak compressive stress σ of concrete. max The stress is 0.4 to 0.5 times the normal value; exceeding this stress triggers the concrete to enter the damage stage. Therefore, this patent conservatively uses 0.3σ. max The starting stress for damage value correction is only for compressive stress of 0.3σ. max ~σ max Damage correction calculations for staged concrete axially compressed members are performed to account for changes in Poisson's ratio, while when the compressive stress is less than 0.3σ... max No correction is needed at this time.
[0037] This invention provides a method for calculating concrete damage correction based on ultrasonic velocity that takes into account changes in Poisson's ratio, comprising the following steps:
[0038] Step 1: Measure the ultrasonic velocity in the area of interest on the concrete member in the initial undamaged and damaged states using conventional methods.
[0039] Step 2: Estimate the average compressive stress in the measurement area based on the stress condition of the component;
[0040] Step 3: Calculate the Poisson's ratio correction factor using formula (3), and then substitute it into formula (2) to obtain the damage value of the concrete.
[0041]
[0042] Where: D is the damage variable; v is the ultrasonic wave propagation velocity of the material in its initial undamaged state. The ultrasonic wave propagation speed of the material under damaged conditions is α, which is the Poisson's ratio correction factor.
[0043]
[0044] in: σ max This represents the peak compressive stress in the concrete. This represents the actual compressive stress value; C1 to C3 are coefficients. The ultrasonic velocity in step 1 includes both longitudinal and transverse waves.
[0045] The results were obtained by fitting the axial compression test data as shown in the attached figure. Figure 1 and Figure 2 The fitted plot, and the values of coefficients C1 to C3 are shown in Table 1 below.
[0046] Table 1. Values of the coefficients in the Poisson's ratio correction coefficient fitting function.
[0047]
[0048] Example 1
[0049] A C30 plain concrete column specimen measuring 200mm × 200mm × 600mm was subjected to axial compression until failure. The loading curve is shown below. Figure 3 As shown, damage assessment is now performed according to the method given in this patent.
[0050] To illustrate the corrective effect and relative error of this patent, the following methods are used: Figure 4 The loading device shown is used to measure axial strain and calculate elastic modulus by arranging strain gauges on the four sides of the specimen during the test. Then, the damage value based on the equivalent strain method is calculated according to formula (4) as the accurate value for comparison. Among them, 1 is the transducer, which is the probe of the multifunctional ultrasonic instrument; 2 is the clamp of the transducer, which is used to assist in axial testing; 4 is the hydraulic controller; and 3 is the press plate used to provide the test pressure.
[0051]
[0052] Where: E is the elastic modulus of the material in its initial state; This refers to the elastic modulus of the material when it is damaged.
[0053] The ultrasonic measurement was performed using the NM4A multi-functional ultrasonic instrument manufactured by Beijing Concord Co., Ltd. The transducer used was a longitudinal wave transducer with a working frequency of 40kHz. The ultrasonic pulse velocity (UPV) was measured along two paths: the line connecting the midpoints of the bottom surface of the component (axial direction) and the line connecting the midpoints of the side surface (horizontal direction). The axial distance was 600mm and the horizontal distance was 200mm.
[0054] To determine the axial compressive stress corresponding to each load level, in this example, based on... Figure 3 Loading curve and cross-sectional average compressive stress formula σ=F N Find A;
[0055] The Poisson's ratio correction coefficient was calculated using the fitting formula (3), and then substituted into formula (2) to obtain the damage value of concrete under different compressive stresses (where the initial ultrasonic velocity is 0 to 0.3σ). max (The average value of the stage). This yields... Figure 5 and Figure 6 The comparison curves of damage calculation results by different methods are shown: As can be seen from the figure, the damage value calculated by formula (1) without taking Poisson's ratio into account has the risk of underestimating the damage and is significantly different from the accurate value obtained by formula (4). The average relative error can reach 58% (axial damage). However, after substituting the Poisson's ratio correction factor, the error can be reduced to 13%. It can be seen that the damage value calculated according to this patent is closer to the accurate value.
[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.
Claims
1. A method for calculating concrete damage correction based on ultrasonic speed, taking into account changes in Poisson's ratio, characterized in that, Includes the following steps: Step 1: Measure the ultrasonic velocity in the area of interest on the concrete member in the initial undamaged and damaged states using conventional methods. Step 2: Estimate the average compressive stress in the measurement area based on the stress condition of the component; Step 3: Calculate the Poisson's ratio correction factor using formula (3), and then substitute it into formula (2) to obtain the damage value of the concrete. Where: D is the damage variable; v is the ultrasonic wave propagation velocity of the material in its initial undamaged state. The ultrasonic wave propagation speed of the material under damaged conditions is α, which is the Poisson's ratio correction factor. in: σ max This represents the peak compressive stress in the concrete. The actual compressive stress value is represented by C1 to C3, which are coefficients.
2. The method for calculating ultrasonic concrete damage correction based on Poisson's ratio variation according to claim 1, characterized in that, In step 1, ultrasonic speeds include longitudinal waves and transverse waves; For the longitudinal wave case, C1 to C3 in step 3 are: C1 = -0.0000114, C2 = 0.104, C3 = 0.984; for the transverse wave case, C1 to C3 in step 3 are: C1 = 0.0000341, C2 = 0.125, C3 = 1.
060.
3. The method for calculating ultrasonic-velocity concrete damage correction based on Poisson's ratio variation according to claim 1, characterized in that, The corrected starting stress in step 3 is: 0.3σ max .