Method for rapidly evaluating accumulated damage of concrete under simulated long-term sunlight environment
By using a resonator in a constant temperature and humidity box to measure the elastic modulus of concrete samples, calculate the elastic modulus ratio and evaluate the accumulated damage degree, the problem of inaccurate damage assessment of concrete in the prior art under long-term sunshine environment is solved, and a rapid and accurate damage rating is achieved.
Patent Information
- Application Number
- CN202411957669.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-30
- Publication Date
- 2025-05-16
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
The prior art is difficult to accurately evaluate the degree of accumulated damage of concrete in long-term sunshine environments, resulting in a large difference in the measurement results from the actual situation.
By measuring the elastic modulus of concrete samples in a constant temperature and humidity chamber using a resonator in a constant temperature and humidity chamber, the elastic modulus ratio is calculated, and the cumulative damage degree of concrete is evaluated using formulas.
A rapid and accurate assessment of the accumulated damage degree of concrete in long-term sunshine environments is achieved, providing a specific damage rating.
Smart Images
Figure CN120009155A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of building material performance detection and evaluation, in particular to a method for quickly evaluating the cumulative damage of concrete in a simulated long-term sunshine environment. Background Art
[0002] Existing studies have shown that sunlight can improve the strength of concrete, but at the same time it will have an adverse effect on the crack resistance of concrete. The tensile strength and compressive strength loss of concrete under sunlight is greater than that of concrete without sunlight. In addition, the erosion of concrete structures by external environmental factors causes physical or chemical changes in the concrete structure, thus causing damage or destruction; the main manifestations include concrete carbonization, chloride ion erosion, alkali aggregate reaction, freeze-thaw damage, and steel corrosion.
[0003] In order to simulate the measurement of the cumulative damage of concrete under long-term sunlight environment in the laboratory, a common method is to divide the degree of concrete damage into different cumulative damage levels by comparing and analyzing the concrete deformation modulus, static equivalent strain and residual strain damage indicators.
[0004] However, when stress is applied to concrete, it is easy to cause certain mechanical damage to the inside of the concrete specimen, which makes the measurement results under simulated sunlight environment often differ greatly from the actual situation. Therefore, there is an urgent need for an in-situ assessment method that can directly determine the degree of cumulative damage of existing structural concrete. Summary of the invention
[0005] In order to solve the above technical problems, the present invention provides a method for quickly assessing the cumulative damage of concrete in a simulated long-term sunlight environment.
[0006] To achieve the above object, the present invention is implemented according to the following technical solutions:
[0007] A method for rapidly assessing the cumulative damage of concrete in a simulated long-term sunlight environment comprises the following steps:
[0008] S1. The concrete sample is placed on the support of the resonator in a constant temperature and humidity chamber, and a xenon lamp simulating long-term sunlight is installed on the top of the constant temperature and humidity chamber, and the xenon lamp is irradiated on the concrete sample;
[0009] S2. Data Collection
[0010] Before the xenon lamp is turned on, the initial elastic modulus of the concrete sample is collected by a resonance instrument; after the xenon lamp is turned on, the elastic modulus of the concrete sample at different irradiation times is collected;
[0011] S2. Calculation of elastic modulus ratio
[0012] Calculate the elastic modulus ratio E / E0 at each time point, where E is the elastic modulus of the concrete sample at the current irradiation time, and E0 is the initial elastic modulus of the concrete sample;
[0013] S3. Damage Assessment
[0014] According to the change of elastic modulus ratio, the cumulative damage degree of concrete is evaluated using the following formula:
[0015] D p =1-(E / E0);
[0016] Where: D p is the degree of damage, and its value range is [0,1]. The closer the D value is to 1, the higher the cumulative damage degree of concrete is. p The closer the value is to 0, the lower the cumulative damage of concrete;
[0017] S4. Damage level assessment
[0018] According to the degree of damage p , the cumulative damage degree of concrete is divided into four levels: slight damage, moderate damage, severe damage and failure.
[0019] Furthermore, in step S2, the dynamic elastic modulus of the concrete sample is calculated according to the formula:
[0020]
[0021] Where: E is the dynamic elastic modulus of concrete, in MPa;
[0022] λ is the side length of the square cross section, in mm;
[0023] L is the length in mm;
[0024] M is the mass in kg;
[0025] f is the fundamental frequency of lateral vibration, in Hz.
[0026] Furthermore, the length×width×height of the concrete sample is 300 mm×150 mm×150 mm.
[0027] Furthermore, in step S2, each time the elastic modulus of the concrete sample is tested, the test is repeated twice, and the fluctuation range of the test result is ensured to be less than ±0.5%, and the average value of the two tests is taken as the measured value of the elastic modulus of the concrete sample.
[0028] Furthermore, in step S4, the assessment levels of the degree of cumulative damage to concrete are divided into:
[0029] Minor damage: 0.0 <Dp ≤0.20;
[0030] Medium damage: 0.2 <D p ≤0.625;
[0031] Severe damage: 0.625 <Dp≤0.876;
[0032] Failure: D p >0.876.
[0033] Compared with the prior art, the present invention tests the fundamental frequency of the lateral vibration of concrete samples under different irradiation times by a resonance instrument, thereby calculating the elastic modulus of the concrete by a formula, and then comparing it with the initial elastic modulus of the concrete sample, and finally obtaining the numerical value of the cumulative damage degree of the concrete, thereby obtaining a specific cumulative damage grade; the evaluation method of the present invention is simple and the evaluation result is accurate. BRIEF DESCRIPTION OF THE DRAWINGS
[0034] Figure 1 Schematic diagram of concrete specimens installed in a constant temperature and humidity insulation box. DETAILED DESCRIPTION
[0035] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the invention.
[0036] The concrete sample 3 used in the following examples has a size of 300 mm × 150 mm × 150 mm (length × width × height), and is cured for 28 days according to conventional standards; its mass and size are measured before the test. The allowable deviation of the mass of the three samples from their average is ±0.5%, and the allowable deviation of the size from its average is 1%. The mass of the concrete sample is finally determined to be 15.3 kg.
[0037] like Figure 1 As shown, the concrete sample 3 is placed on the support of the resonator 2 in the constant temperature and humidity box 1, and a xenon lamp 4 simulating long-term sunlight is installed on the top of the constant temperature and humidity box 1 (which can be directly purchased commercially), and the light intensity is 1200W / m 2, the xenon lamp 4 is irradiated on the concrete sample 3. By simulating a long-term sunshine environment in the laboratory, the controller 5 is used in this embodiment to adjust the temperature in the constant temperature and humidity chamber to maintain at 20°C and the humidity to maintain at 20%, so as to evaluate the performance changes of the concrete under the long-term sunshine environment; and determine the positions of the excitation transducer and the pickup when measuring the lateral fundamental frequency vibration frequency by the resonance method. When measuring with a resonator, adjust the excitation power and receiving gain knobs to appropriate positions, and quickly find the resonance point by coarse adjustment, and then make fine adjustments. When the amplitude values indicated by the microammeter and the oscilloscope increase consistently and reach the maximum amplitude, it is resonance. At this time, the frequency read from the digital counter is the natural frequency of. When observing, the test should be repeated twice, and the fluctuation range of the test results should be less than ±0.5%. The average value of the two tests is taken as the measured value of.
[0038] Before the xenon lamp is turned on, the natural frequency of the concrete sample is collected by a resonance instrument, and the initial elastic modulus is calculated using the following formula. The dynamic elastic modulus of the concrete sample is calculated according to the formula:
[0039]
[0040] Where: E is the dynamic elastic modulus of concrete, in MPa;
[0041] λ is the side length of the square cross section, in mm;
[0042] L is the length in mm;
[0043] M is the mass in kg;
[0044] f is the fundamental frequency of lateral vibration, in Hz;
[0045] After the xenon lamp is turned on, the natural frequencies of the concrete samples irradiated for 1, 7, 14, 21, 28, and 35 days are collected by a resonance instrument, and the elastic modulus of the concrete samples is calculated using the above formula;
[0046] Then the elastic modulus ratio E / E0 at each time point is calculated, where E is the elastic modulus of the concrete sample at the current irradiation time, and E0 is the initial elastic modulus of the concrete sample;
[0047] Finally, according to the change of elastic modulus ratio, the cumulative damage degree of concrete is evaluated using the following formula:
[0048] D p =1-(E / E0);
[0049] Where: D p is the degree of damage, and its value range is [0,1]. The closer the D value is to 1, the higher the cumulative damage degree of concrete is. pThe closer the value is to 0, the lower the cumulative damage of concrete;
[0050] According to the degree of damage p , the cumulative damage degree of concrete is divided into four levels: slight damage, moderate damage, severe damage and failure. The assessment level of the cumulative damage degree of concrete is divided into:
[0051] Minor damage: 0.0 <D p ≤0.20;
[0052] Medium damage: 0.2 <D p ≤0.625;
[0053] Severe damage: 0.625 <Dp≤0.876;
[0054] Failure: D p >0.876.
[0055] Through the above method, the degree of cumulative damage of concrete under a simulated long-term sunlight environment can be determined quickly and accurately.
[0056] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.
Claims
1. A method for rapid assessment of concrete cumulative damage in a simulated long-term sunlight environment, characterized in that: The following steps are involved: S1. The concrete sample is placed on the support of the resonator in a constant temperature and humidity chamber, and a xenon lamp simulating long-term sunlight is installed on the top of the constant temperature and humidity chamber, and the xenon lamp is irradiated on the concrete sample; S2. Data Collection Before the xenon lamp is turned on, the initial elastic modulus of the concrete sample is collected by a resonance instrument; after the xenon lamp is turned on, the elastic modulus of the concrete sample at different irradiation times is collected; S2. Calculation of elastic modulus ratio Calculate the elastic modulus ratio E / E0 at each time point, where E is the elastic modulus of the concrete sample at the current irradiation time, and E0 is the initial elastic modulus of the concrete sample; S3. Damage Assessment According to the change of elastic modulus ratio, the cumulative damage degree of concrete is evaluated using the following formula: D p =1-(E / E0); Where: D p is the degree of damage, and its value range is [0,1]. The closer the D value is to 1, the higher the cumulative damage degree of concrete is. p The closer the value is to 0, the lower the cumulative damage of concrete; S4. Damage level assessment According to the degree of damage p , the cumulative damage degree of concrete is divided into four levels: slight damage, moderate damage, severe damage and failure.
2. The method for rapid assessment of concrete cumulative damage in a simulated long-term sunlight environment according to claim 1 is characterized in that: In step S2, the dynamic elastic modulus of the concrete sample is calculated according to the formula: Where: E is the dynamic elastic modulus of concrete, in MPa; λ is the side length of the square cross section, in mm; L is the length in mm; M is the mass in kg; f is the fundamental frequency of lateral vibration, in Hz.
3. The method for rapid assessment of concrete cumulative damage in a simulated long-term sunlight environment according to claim 1 is characterized in that: The length×width×height of the concrete sample is 300 mm×150 mm×150 mm.
4. The method for rapid assessment of concrete cumulative damage in a simulated long-term sunlight environment according to claim 1 is characterized in that: In step S2, each time the elastic modulus of the concrete sample is tested, the test is repeated twice, and the fluctuation range of the test result is ensured to be less than ±0.5%, and the average value of the two tests is taken as the measured value of the elastic modulus of the concrete sample.
5. The method for rapid assessment of concrete cumulative damage in a simulated long-term sunlight environment according to claim 1 is characterized in that: In step S4, the assessment level of the degree of cumulative damage to concrete is divided into: Minor damage: 0.0 <D p ≤0.20; Medium damage: 0.2 <D p ≤0.625; Severe damage: 0.625 <Dp≤0.876; Failure: D p >0.876.