A method for evaluating the damage degree of a structural sealant

Abstract

The present invention provides a method for evaluating the damage degree of structural sealant, belonging to the technical field of damage detection of glass curtain walls. This method first conducts finite element modeling on the hidden frame glass curtain wall panel unit. Under different damage degrees, the cross-point frequency response function of the response at the eighth point of excitation at the sixteenth point of the long side and the short side of the panel unit is calculated using the harmonic response analysis method and the logarithm is taken. The relative cumulative difference of the logarithmic cross-point frequency response function is calculated, and the relative cumulative difference and the damage degree are linearly fitted to obtain the functional relationship between the damage degree of the structural sealant and the relative cumulative difference. Then, a hammering test of the response at the eighth point of excitation at the sixteenth point of the panel unit is carried out to obtain the relative cumulative difference E of the logarithmic cross-point frequency response function of the panel unit. t , and the damage degree of the structural sealant of the panel unit is calculated according to the fitting equation. This method has the advantages of on-site detection, real-time prediction, and timely repair for predicting the damage degree of structural sealant, and is applicable to engineering practice.

Description

Technical Field

[0001] The present invention relates to the technical field of glass curtain wall damage detection, and particularly to a method for evaluating the damage degree of structural sealant. Background Art

[0002] Glass curtain walls are widely used in modern architecture due to their beautiful appearance and unique shape. However, during use, due to exposure to sunlight and heavy rain, they are prone to damage and aging, resulting in a reduction in the firmness of the glass panels or even detachment, threatening people's lives and property safety. Therefore, it is necessary to conduct damage detection in a timely manner to determine the curtain wall units that need to be repaired and reinforced. In the prior art, damage detection methods for structural sealants of glass curtain walls without a reference model and damage identification methods for structural sealants of glass curtain walls based on the origin frequency response function have been disclosed. There are also techniques that illustrate an increase in modal displacement at the position where the structural sealant glass is missing and a decrease in frequency with an increase in the degree of structural sealant missing through modal tests. Additionally, there is a technique that discloses estimating the damage of the structural sealant glass sealant using the fundamental frequency of the acceleration Fourier spectrum of a Doppler laser vibrometer. The above damage identification methods based on dynamic characteristics or dynamic responses all identify the damage of the structural sealant, but none of them evaluate the damage degree. In actual detection, although many hidden frame curtain walls have minor damage, it does not affect their basic use, so no measures need to be taken. When the structural sealant has damage but the risk is low, it can be directly reinforced. For relatively large damage, the structural sealant needs to be replaced immediately. Therefore, in this field, there is an urgent need for a method for evaluating the damage degree of structural sealant. Summary of the Invention

[0003] In order to solve the deficiencies of the existing glass curtain wall damage detection methods, the present invention provides a method for evaluating the damage degree of structural sealant. The method first performs finite element modeling on the panel unit of a hidden frame glass curtain wall. Under different damage degrees, the cross-point frequency response function of the response at the one-eighth point excited by the one-sixteenth point on the long side and the short side of the panel unit is calculated using the harmonic response analysis method. On this basis, the relative cumulative difference of the logarithmic cross-point frequency response function is calculated, and a linear fit is performed between the relative cumulative difference and the damage degree to obtain the functional relationship between the damage degree of the structural sealant and the relative cumulative difference. Then, a hammer test of the response at the one-eighth point excited by the one-sixteenth point is performed on the panel unit to obtain the relative cumulative difference E t of the logarithmic cross-point frequency response function of the panel unit, and the damage degree of the structural sealant of the panel unit is calculated according to the fitting equation.

[0004] The method includes the following steps:

[0005] S1: Establish a finite element model based on the measured length, width, thickness, density, Poisson's ratio, elastic modulus of the glass and the length, width, thickness, and elastic modulus of the structural sealant of the hidden frame glass curtain wall panel unit;

[0006] S2: Under different damage degrees, apply a unit harmonic load perpendicular to the panel at the one-sixteenth point of the length and width of the panel unit, calculate the acceleration response amplitude at the one-eighth point of the length and width as the cross-point frequency response function H(ω), where ω is the frequency of the harmonic load, and then take the logarithm of the modulus of the cross-point frequency response function to obtain the logarithmic cross-point frequency response function ln|H(ω)|;

[0007] S3: Under different damage degrees, calculate the relative cumulative difference E of the logarithmic cross-point frequency response function before and after the damage of the structural sealant t , and perform a linear fit on the relative cumulative difference E t and the damage degree to obtain the functional relationship E t = c1 + c2d between the damage degree of the structural sealant and the relative cumulative difference, where c1 and c2 are fitting constants respectively, and d is the damage degree;

[0008] S4: Fabricate a panel unit identical to the panel unit to be detected and with an intact structural sealant, measure the cross-point frequency response function through experiments, and then calculate the logarithmic cross-point frequency response function as the non-damaged logarithmic cross-point frequency response function;

[0009] S5: Measure the cross-point frequency response function of the panel unit to be detected through experiments, calculate the logarithmic cross-point frequency response function, and then calculate the relative cumulative difference E of the logarithmic cross-point frequency response function of the panel unit to be detected relative to the non-damaged logarithmic cross-point frequency response function in S4 ts , and calculate the damage degree of the structural sealant of the panel unit to be detected using the fitting function in S3

[0010] Among them, in S1, the finite element model uses shell elements to simulate the glass. The length and width of the panel unit are equally divided into sixteen or an integer multiple of sixteen, and spring elements perpendicular to the glass are used to simulate the structural sealant.

[0011] In S2, the damage degree is the ratio of the reduction value of the stiffness coefficient of the spring element to the non-damaged stiffness coefficient of the spring element, that is, the damage degree d is:

[0012]

[0013] Among them, It is the stiffness coefficient when the spring element is damaged. α takes more than 10 numbers from 0, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1 for calculation.

[0014] Among them, the undamaged stiffness coefficient of the spring element is:

[0015]

[0016] Among them, E r is the elastic modulus of the structural sealant, l i is the length of the structural sealant corresponding to the i-th spring element, w is the width of the structural sealant, h r is the thickness of the structural sealant.

[0017] The relative cumulative difference E of the logarithmic cross-point frequency response function of the structural sealant before and after damage in S3 t is:

[0018]

[0019] In the formula, H u (ω) and H d (ω) respectively represent the cross-point frequency response function before and after damage. The upper limit frequency a is the length of the glass, b is the width of the glass, E g is the elastic modulus of the glass, v is the Poisson's ratio of the glass, h g is the thickness of the glass, ρ is the density of the glass;

[0020] The relative cumulative difference E of the logarithmic cross-point frequency response function of the panel unit to be detected in S5 relative to the undamaged logarithmic cross-point frequency response function in S4 ts is calculated in the same way above. The undamaged logarithmic cross-point frequency response function in S4 is the cross-point frequency response function before damage, and the logarithmic cross-point frequency response function of the panel unit to be detected is the cross-point frequency response function after damage.

[0021] The measurement method of the cross-point frequency response function in S4 and S5 is as follows: Use a force hammer to strike the one-sixteenth point of the length and width of the panel unit, install an acceleration sensor at the one-eighth point of the length and width, measure the force signal of the force hammer and the acceleration signal of the acceleration sensor at the same time, and calculate the ratio of the Fourier transform coefficient of the acceleration signal to the force signal, which is the measured value of the cross-point frequency response function.

[0022] The beneficial effects of the above technical solutions of the present invention are as follows:

[0023] In the above solution, by using a finite element model to simulate different degrees of damage to the structural sealant, a large amount of labor and time can be saved. Finally, the calculated degree of damage to the structural sealant can provide technical guidance for on-site inspection and maintenance. Description of the Drawings

[0024] Figure 1 It is a flowchart of the method for evaluating the degree of damage to the structural sealant of the present invention;

[0025] Figure 2 It is a diagram of the panel unit size in the embodiment of the present invention;

[0026] Figure 3 It is a finite element model diagram;

[0027] Figure 4 It is the logarithmic cross-point frequency response function under different degrees of damage simulated by finite element;

[0028] Figure 5 It is for E t Fitting curve;

[0029] Figure 6 It is the panel unit and detection system in the embodiment of the present invention;

[0030] Figure 7 It is the logarithmic cross-point frequency response function of the measured panel unit before and after damage.

[0031] Wherein: 1 - panel unit, 2 - structural sealant, 3 - acceleration sensor, 4 - impact hammer; 5 - signal collector; 6 - computer; 7 - damage location. Detailed Embodiment

[0032] To make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the drawings and specific embodiments.

[0033] The present invention provides a method for evaluating the degree of damage to a structural sealant in view of the current problem that the degree of damage to the structural sealant cannot be evaluated.

[0034] As Figure 1 shown, the method includes the following steps:

[0035] S1: According to the length, width, thickness, density, Poisson's ratio, elastic modulus of the glass measured from the panel unit of the hidden frame glass curtain wall and the length, width, thickness, and elastic modulus of the structural sealant, establish a finite element model;

[0036] S2: Under different degrees of damage, apply a unit harmonic load perpendicular to the panel at the one-sixteenth point of the length and width of the panel unit. The system damping ratio is taken as a constant value of 0.01 - 0.03. Calculate the acceleration response amplitude at the one-eighth point of the length and width as the cross-point frequency response function H(ω), where ω is the frequency of the harmonic load. Then take the logarithm of the modulus of the cross-point frequency response function to obtain the logarithmic cross-point frequency response function ln|H(ω)|;

[0037] S3: Under different degrees of damage, calculate the relative cumulative difference E of the logarithmic cross-point frequency response function before and after the damage of the structural sealant of the structure t , and linearly fit the relative cumulative difference E t and the degree of damage to obtain the functional relationship E t = c1 + c2d between the degree of damage of the structural sealant of the structure and the relative cumulative difference, where c1 and c2 are fitting constants respectively, and d is the degree of damage;

[0038] S4: Fabricate a panel unit identical to the panel unit to be detected and with intact structural sealant. Experimentally measure the cross-point frequency response function, and then calculate the logarithmic cross-point frequency response function as the non-damaged logarithmic cross-point frequency response function;

[0039] S5: Experimentally measure the cross-point frequency response function of the panel unit to be detected, calculate the logarithmic cross-point frequency response function, and then calculate the relative cumulative difference E of the logarithmic cross-point frequency response function of the panel unit to be detected relative to the non-damaged logarithmic cross-point frequency response function in S4 ts , and calculate the degree of damage of the structural sealant of the panel unit to be detected from the fitting function in S3

[0040] The following is illustrated with specific embodiments.

[0041] In specific applications, the dimensions of the panel unit of the glass curtain wall to be detected are as Figure 2 shown. According to the dimensions and physical parameters of the panel unit, establish a finite element model, as Figure 3 . The physical parameters of the glass in the finite element model are: length is 2.06 m, width is 1.46 m, thickness is 0.006 m, Poisson's ratio ν = 0.2, elastic modulus E g = 7.2×10 10 Pa, density ρ = 2500 kg / m 3. The glass is modeled using shell elements. The mesh of the elements is divided such that the length is divided into 80 equal parts and the width is divided into 64 equal parts. The structural sealant is simplified as a linear spring in the direction perpendicular to the panel. The elastic modulus of the structural sealant is 1 MPa, the thickness and width are both 0.01 m. The lengths of the structural sealant corresponding to the spring elements at the middle nodes of the length and width are 2.06 / 80 = 0.0258 m and 1.46 / 64 = 0.0228 m respectively, and the length of the structural sealant corresponding to the spring elements at the four corner points is (2.06 / 80 + 1.46 / 64) / 2 = 0.0243 m. The undamaged stiffness coefficients of the spring elements at the middle nodes of the length and width are

[0042] The undamaged stiffness coefficients of the spring elements at the four corner points are

[0043] It is defined that the stiffness of all the springs on the right side of the glass panel is reduced, and the spring stiffness on this side is multiplied by the corresponding value. The ratios of the reduction values of the spring element stiffness coefficients in the damaged state to the stiffness coefficients of the undamaged spring elements are 0, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 to calculate 16 different damage degrees of the structural sealant, as shown in Table 1.

[0044] Table 1. Damage degrees of the structural sealant

[0045] Operating condition 1 2 3 4 5 6 7 8 Degree of damage (%) 0 0.704 1.408 2.113 2.817 3.521 4.225 4.930 Operating condition 9 10 11 12 13 14 15 16 Degree of damage (%) 5.634 6.338 7.042 7.746 8.451 9.155 9.859 10.563

[0046] A unit harmonic load perpendicular to the panel is applied at the one-sixteenth point of the length and width of the panel element, and the system damping ratio is taken as 0.025. Calculate the logarithmic cross-point frequency response function of the acceleration response amplitude at the one-eighth point of the length and width under different damage degrees, as Figure 4 shown, and calculate the upper limit frequency of the relative cumulative difference of the frequency response function Then calculate the relative cumulative difference of the logarithmic cross-point frequency response function, and the results are listed in Table 2.

[0047] Table 2 Results of damage degree and E t under the finite element model

[0048] Degree of damage % 0 0.704 1.409 2.113 2.817 3.521 4.225 4.930 <![CDATA[E t > 0 0.040 0.085 0.118 0.146 0.166 0.193 0.214 Degree of damage % 5.634 6.338 7.042 7.745 8.451 9.155 9.859 10.563 <![CDATA[E t > 0.220 0.218 0.255 0.256 0.273 0.281 0.290 0.301

[0049] Perform a linear fitting on the different damage degrees of the structural sealant and their corresponding relative cumulative difference magnitudes. The fitting curve is as Figure 5 shown, and the fitting result is as in Equation (1)

[0050] E t = 0.05189 + 0.02636d (1)

[0051] The correlation coefficient of the fitted curve is 0.93086, indicating a good fitting effect.

[0052] As Figure 6 shown, a complete glass panel unit 1 is fabricated. An acceleration sensor 3 is arranged at the intersection of the 1 / 8 of the long side and the 1 / 8 of the short side of the glass panel unit 1. A pulse load is applied at the intersection of the 1 / 16 of the long side and the 1 / 16 of the short side of the glass panel unit 1 sample with a force hammer 4. The signals of the acceleration sensor 3 and the force hammer 4 are transmitted to a computer 6 through a signal collector 5, and the logarithmic cross-point frequency response function is calculated from the force signal and the acceleration signal as the logarithmic cross-point frequency response function under non-damage. The damaged position 7 of the cut structural sealant in the structural sealant 2 is cut by 42.2 cm to obtain the damaged panel unit, and the logarithmic cross-point frequency response function of the damaged panel unit is measured. The logarithmic cross-point frequency response functions before and after damage are calculated as Figure 7 shown. The calculated relative cumulative difference before and after damage is 0.2067, and then the damage degree d of the structural sealant is calculated from Equation (1) s =(0.2067 - 0.05189) / 0.02636 = 0.0588, while the actual damage degree of the structural sealant is 0.06, indicating a good evaluation effect of the damage degree of the structural sealant.

[0053] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for evaluating the damage degree of a structural sealant, characterized in that, The steps are as follows: S1: Establish a finite element model based on the length, width, thickness, density, Poisson's ratio, elastic modulus of the glass measured for the unit of the hidden frame glass curtain wall panel, and the length, width, thickness, and elastic modulus of the structural sealant. S2: Under different damage degrees, apply a unit harmonic load perpendicular to the panel at the one-sixteenth point of the length and width of the panel unit, calculate the acceleration response amplitude at the one-eighth point of the length and width as the cross-point frequency response function H(ω), where ω is the frequency of the harmonic load. Then take the logarithm of the modulus of the cross-point frequency response function to obtain the logarithmic cross-point frequency response function ln|H(ω)|. S3: Calculate the relative cumulative difference E of the logarithmic cross-point frequency response function of the structural sealant before and after damage under different damage degrees t , and linearly fit the relative cumulative difference E t and the damage degree to obtain the functional relationship E t = c1 + c2d between the damage degree of the structural sealant and the relative cumulative difference, where c1 and c2 are fitting constants respectively, and d is the damage degree; S4: Fabricate a panel unit identical to the panel unit to be detected and with the structural sealant intact. Experimentally measure the cross-point frequency response function, and then calculate the logarithmic cross-point frequency response function as the non-damaged logarithmic cross-point frequency response function. S5: Experimentally measure the cross-point frequency response function of the panel unit to be detected, calculate the logarithmic cross-point frequency response function, and then calculate the relative cumulative difference E of the logarithmic cross-point frequency response function of the panel unit to be detected with respect to the logarithmic cross-point frequency response function of the non-damaged one in S4 ts , and calculate the damage degree of the structural sealant of the panel unit to be detected by the fitting function in S3 2. The method for evaluating the damage degree of a structural sealant according to claim 1, characterized in that, In the finite element model in S1, the shell element is used to simulate the glass, and the length and width of the panel unit are equally divided into sixteen or an integer multiple of sixteen. The spring element perpendicular to the glass is used to simulate the structural sealant.

3. The method for evaluating the damage degree of a structural sealant according to claim 1, characterized in that, In S2, the damage degree is the ratio of the reduction value of the stiffness coefficient of the spring element to the non-damaged stiffness coefficient of the spring element, that is, the damage degree d is: Among them, is the undamaged stiffness coefficient of the spring element, is the stiffness coefficient of the spring element when damaged. α takes more than 10 numbers from 0, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1 for calculation.

4. The method for evaluating the damage degree of a structural sealant according to claim 3, characterized in that, The non-damaging stiffness coefficient of the spring unit is as follows: Among them, E r is the elastic modulus of the structural sealant, l i is the length of the structural sealant corresponding to the i-th spring unit, w is the width of the structural sealant, h r is the thickness of the structural sealant.

5. The method for evaluating the damage degree of a structural sealant according to claim 1, characterized in that, The relative cumulative difference E of the logarithmic cross-point frequency response function of the structural sealant before and after damage in S3 t is as follows: Where, H u (ω) and H d (ω) represent the cross-point frequency response functions before and after damage respectively, and the upper limit frequency of the relative cumulative difference of the frequency response function a is the length of the glass, b is the width of the glass, E g is the elastic modulus of the glass, v is the Poisson's ratio of the glass, h g is the thickness of the glass, and ρ is the density of the glass; The logarithmic cross-point frequency response function relative cumulative difference E of the logarithmic cross-point frequency response function of the panel unit to be detected in S5 with respect to the logarithmic cross-point frequency response function of the non-damaged logarithmic cross-point frequency response function in S4 ts The calculation method is the same as above. The logarithmic cross-point frequency response function of the non-damaged S4 is the cross-point frequency response function before damage, and the logarithmic cross-point frequency response function of the panel unit to be detected is the cross-point frequency response function after damage.

6. The method for evaluating the damage degree of a structural sealant according to claim 1, characterized in that: In S4 and S5, the method for measuring the cross-point frequency response function is: strike the one-sixteenth point of the length and width of the panel unit with a force hammer, install an acceleration sensor at the one-eighth point of the length and width, simultaneously measure the force signal of the force hammer and the acceleration signal of the acceleration sensor, and calculate the ratio of the Fourier transform coefficient of the acceleration signal to the force signal, which is the measured value of the cross-point frequency response function.

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