Method for evaluating service life of building shock insulation support and application

Abstract

The invention discloses a method for evaluating the service life of a building shock insulation support and application. According to the method, the aging time t at the critical value of the horizontal equivalent stiffness change rate is obtained through the horizontal equivalent stiffness change rate-aging time curve of the support sample, and then the service life of the support is evaluated through the fitting straight line of the aging time t and the thermodynamic temperature. The deduced evaluation method is simple, the adopted horizontal equivalent stiffness is matched with the actual use environment of the product, the test period can be greatly shortened, and safe use of the building is guaranteed more reliably.

Description

Technical Field

[0001] The present invention belongs to the technical field of bearing testing, and particularly relates to an evaluation method and application for the service life of building isolation bearings. Background Art

[0002] An isolation bearing refers to a supporting device provided for a structure to meet the isolation requirements. An isolation layer is added between the superstructure and the foundation, and a rubber isolation bearing is installed to achieve a soft connection with the ground. Through such technology, during an earthquake, when the ground generates a horizontal displacement, the isolation bearing needs to have sufficient shear performance to absorb and dissipate about 80% of the earthquake energy. The promulgated "Regulations on the Administration of Earthquake Resistance in Construction Projects" has greatly promoted the popularization and application of isolation and shock absorption technologies.

[0003] JG / T 118-2018 "Building Isolation Rubber Bearings" stipulates that under normal circumstances, the designed service life of the bearing should not be less than 60 years. However, it does not elaborate on how to predict its designed service life. And the rubber material in the bearing has a crucial impact on the designed service life of the bearing. If its performance deteriorates or fails, it will seriously affect the energy dissipation and shock absorption effect of the bearing.

[0004] The aging research of products mainly includes natural aging and artificial accelerated aging. Natural aging is the best method to evaluate product failure, but due to the difficulty in controlling environmental test conditions and the long test cycle, the application of this method is relatively difficult. Therefore, accelerated aging tests have become a research trend.

[0005] In the existing methods for predicting the service life of bearings, many use accelerated aging of the rubber material in the bearing structure that has a greater impact on performance, but do not consider that the bonding situation between the rubber and the steel plate in the bearing will also affect the service life of the bearing. In actual applications, the finished bearing is also used to protect the building. Therefore, the aging life of the rubber material cannot fully represent the life of the finished bearing. At the same time, considering the horizontal displacement caused by seismic action, horizontal equivalent stiffness and horizontal ultimate deformation performance tests need to be carried out to ensure that the bearing can still maintain the structural stability of the building under extreme conditions and prevent collapse.

[0006] The present invention mainly aims at the above problems, directly uses the finished bearing for accelerated aging, and at the same time, the horizontal equivalent stiffness performance adopted is consistent with the actual use environment of the product, which can better simulate actual applications and the prediction results are more accurate. Summary of the Invention

[0007] The present invention proposes an evaluation method for the designed service life of building isolation bearings based on accelerated aging tests. The evaluation method provided by the present invention is simple, and the horizontal equivalent stiffness performance adopted is consistent with the actual use environment of the product, which can greatly shorten the test cycle and provide a more reliable guarantee for the safe use of buildings.

[0008] One of the objectives of the present invention is to provide a method for evaluating the service life of a building isolation bearing, including: obtaining the aging time t when the critical value of the horizontal equivalent stiffness change rate is reached from the horizontal equivalent stiffness change rate - aging time curve of the bearing sample, and then evaluating the service life of the bearing through the fitting curve of the aging time t and the thermodynamic temperature. Among them, the horizontal equivalent stiffness change rate - aging time curve of the bearing sample is obtained by testing the horizontal equivalent stiffness change rate after aging treatment of the bearing sample with slow heating and cooling at a certain rate respectively and then fitting.

[0009] According to the present invention, the evaluation method specifically includes the following steps:

[0010] (1) Conduct a horizontal equivalent stiffness test on the bearing sample to be tested that has not been aged;

[0011] (2) Gradually heat multiple groups of bearing samples to be tested to different aging temperatures for aging treatment with different aging times;

[0012] (3) Take out the bearing samples that have been aged in sequence according to the aging time, gradually cool them to room temperature (23 ± 5°C) and keep them warm, and test the horizontal equivalent stiffness of each bearing sample at room temperature;

[0013] (4) Make a curve with the horizontal equivalent stiffness change rate and aging time of the bearing samples measured at the same temperature, and obtain the aging time t corresponding to the critical value of the horizontal equivalent stiffness change rate of the bearing samples from the curves made at different temperatures;

[0014] (5) Make a graph with the logarithm lnt of the aging time t and the reciprocal of the corresponding thermodynamic temperature and obtain the fitting straight line of formula (1):

[0015] lnt = E / RT + B Formula (1)

[0016] In formula (1), t is the aging time corresponding to the critical value of the horizontal equivalent stiffness of the bearing sample; E is the activation energy, with the unit of J / mol; R is the gas constant, with a value of 8.314 J / (mol·K); T is the thermodynamic temperature, with the unit of K; B is the constant term, which is the intercept of the fitting straight line;

[0017] (6) Evaluate the service life of the building isolation bearing at a certain temperature through the fitting straight line of formula (1).

[0018] According to the present invention, in the method for evaluating the service life of the building isolation bearing:

[0019] The critical value is the change rate of the horizontal equivalent stiffness of the aged sample relative to that before aging; preferably, the critical value is 10 - 50%;

[0020] The horizontal ultimate deformation of the unaged bearing sample to be measured ≥ 400%;

[0021] The horizontal ultimate deformation of the bearing sample after aging ≥ 320%.

[0022] According to the present invention, the aging treatment in step (2) of the method for evaluating the life of the building isolation bearing can be realized by using common aging equipment, such as an aging chamber. There are no specific limitations on the aging temperature and aging time used in the aging treatment, and more than 2 different aging temperatures and aging times can be set according to actual needs. The number of samples for aging treatment can also be set according to actual needs. At least 2 bearing samples are set at different aging temperatures.

[0023] According to a preferred embodiment of the present invention, in step (2) of the method for evaluating the life of the building isolation bearing, the heating rate is 0.5 - 2.5 °C / min. Preferably, when the aging temperature does not exceed 80 °C, the heating rate is 0.5 - 1.2 °C / min, and when the aging temperature is higher than 80 °C, the heating rate is 1.8 - 2.5 °C / min.

[0024] According to a preferred embodiment of the present invention, in step (2) of the method for evaluating the life of the building isolation bearing:

[0025] The aging treatment uses at least 3 different temperatures, preferably 3 - 5 different temperatures;

[0026] The temperature of the aging treatment is 50 - 200 °C, for example, it can be any temperature among 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200 °C or the temperature between any two of the above numerical ranges; preferably, the temperature of the aging treatment is 60 - 150 °C.

[0027] According to a preferred embodiment of the present invention, in step (2) of the method for evaluating the life of the building isolation bearing:

[0028] The aging treatment uses at least 3 different times, preferably 3 - 10 different times; more preferably, the longest time of the aging treatment enables the horizontal equivalent stiffness of the sample to reach or exceed the critical value;

[0029] The time of the aging treatment is 24 - 5000 h, for example, it can be any time among 24, 48, 72, 100, 500, 1000, 1500, 2000, 2500, 2500, 3000, 3500, 4000, 4500, 5000 h or the time between any two of the above numerical ranges; preferably, the time of the aging treatment is 72 - 3000 h.

[0030] According to a preferred embodiment of the present invention, in step (2) of the method for evaluating the service life of the building isolation bearing, at least 4 bearing samples are set at different aging temperatures, preferably 8 - 10.

[0031] According to the present invention, in step (3) of the method for evaluating the service life of the building isolation bearing, the cooling rate is 0.5 - 2.5 °C / min. Preferably, when the aging temperature does not exceed 80 °C, the cooling rate is 0.5 - 1.2 °C / min; when the aging temperature is higher than 80 °C, the cooling rate is 1.8 - 2.5 °C / min.

[0032] According to the present invention, in the method for evaluating the service life of the building isolation bearing: in step (3), the heat preservation time is 16 - 144 h, preferably 48 - 96 h.

[0033] The second object of the present invention is to provide a method for evaluating the service life of the above - mentioned building isolation bearing, which is used to evaluate the service life of the building isolation bearing.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The present invention uses the finished bearing for accelerated aging, and the adopted horizontal equivalent stiffness performance is consistent with the actual use environment of the product, which can greatly shorten the test period and provide a reliable basis for the safe use of buildings.

[0036] (2) The present invention adopts the method of slow heating and cooling, which will not cause large instantaneous changes in the environment where the product is located, and is closer to the actual working environment of the product.

[0037] (3) The present invention obtains the horizontal equivalent stiffness change rate - aging time curve measured at the same temperature, and by using the interpolation method, the aging time t at the critical value of the horizontal equivalent stiffness change rate can be obtained more quickly and accurately, while reducing the labor consumption and saving the test cost.

[0038] (4) In the accelerated aging test adopted by the present invention, considering the horizontal displacement caused by the earthquake action, the horizontal equivalent stiffness and horizontal ultimate deformation performance of the bearing samples before and after aging should be tested to ensure that the bearing can still maintain the structural stability of the building under extreme conditions and prevent collapse. Description of the Drawings

[0039] Figure 1 is the curve of the change of the horizontal equivalent stiffness change rate with the aging time measured according to Example 1.

[0040] Figure 2 is the linear fitting straight line of lnt and the reciprocal of the temperature made according to Example 1.

[0041] Figure 3This is a curve showing the change rate of the horizontal equivalent stiffness versus the aging time measured in Example 2.

[0042] Figure 4 It is the linear fitting straight line of lnt and the inverse of temperature made according to Example 2.

[0043] Figure 5 This is a curve showing the change rate of the horizontal equivalent stiffness versus the aging time measured in Example 3.

[0044] Figure 6 It is the linear fitting straight line of lnt and the inverse of temperature made according to Example 3. DETAILED DESCRIPTION

[0045] The present invention provides a method for evaluating the life of a building seismic isolation bearing, which specifically comprises the following steps:

[0046] 1) Before the test, the same batch of bearing products are tested for horizontal equivalent stiffness and horizontal limit deformation performance using a compression shear tester to ensure that their performance meets the standard requirements;

[0047] 2) Place multiple support samples to be tested in a slowly heated aging chamber, with the aging chamber at a temperature of 80°C or below heated at a rate of 0.5-1.2°C / min, and the aging chamber at an aging temperature exceeding 80°C heated at a rate of 1.8-2.5°C / min, and perform aging treatments at different temperatures for different times;

[0048] 3) Take out the aged samples in the order of aging time, put them into a slowly cooling aging box, cool down the aging box with an aging temperature of more than 80°C at a rate of 1.8-2.5°C / min, cool down the aging box with a temperature of 80°C or below at a rate of 0.5-1.2°C / min, keep them warm for a certain period of time after cooling to room temperature, and test the horizontal equivalent stiffness and horizontal limit deformation performance of each bearing sample at room temperature;

[0049] 4) The horizontal equivalent stiffness data of different temperatures and different aging times were summarized and analyzed, and the curves of the horizontal equivalent stiffness change rate and aging time at different temperatures were drawn using Origin software. The time lnt1, lnt2, lnt3, and lnt4 when the critical value was reached at different temperatures were obtained from the fitting curves;

[0050] 5) According to the Arrhenius equation K(T) = A·e -E / RT , the logarithm of the time to reach the critical value at different aging temperatures lnt and the reciprocal of the corresponding thermodynamic temperature Plot the graph. By depicting each point and then using Origin software to obtain the best-fit straight line \(ln t = E / RT + B\) (where \(t\) is the aging time corresponding to the critical value of the horizontal equivalent stiffness of the bearing sample; \(E\) is the activation energy, with the unit of J / mol; \(R\) is the gas constant, with a value of 8.314 J / (mol·K); \(T\) is the thermodynamic temperature, with the unit of K; \(B\) is the constant term), evaluate the service life of the bearing through the above-mentioned fitted straight line.

[0051] Among them, in the method for evaluating the life of the building isolation bearing:

[0052] The critical value is the change rate of the horizontal equivalent stiffness of the sample after aging relative to that before aging; preferably, the critical value is 10 - 50%;

[0053] The horizontal ultimate deformation of the unaged bearing sample to be tested is ≥ 400%, and the horizontal ultimate deformation of the bearing sample after aging is ≥ 320%.

[0054] The present invention will be specifically described below in conjunction with specific embodiments. It is necessary to point out here that the following embodiments are only used for further illustration of the present invention and cannot be understood as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art to the present invention based on the content of the present invention still fall within the protection scope of the present invention.

[0055] The test instruments and test conditions adopted in the embodiments are as follows:

[0056] Test for horizontal equivalent stiffness and horizontal ultimate deformation performance: JG / T 118 - 2018 "Building Isolation Rubber Bearings";

[0057] The accelerated aging test is carried out in accordance with the provisions of GB / T 3512 - 2014.

[0058] Example 1

[0059] (1) Before the test, use a compression-shear testing machine to test the horizontal equivalent stiffness and horizontal ultimate deformation performance of the finished bearings of the same batch (natural rubber bearing LNR500). The measured horizontal equivalent stiffness of the bearing is 1.027 kN / mm, and the horizontal ultimate deformation performance is ≥ 400%;

[0060] (2) Put the natural rubber bearings LNR500 of the same batch into aging ovens with slow temperature rise at 80°C, 90°C, 100°C, and 110°C respectively. The aging oven at 80°C heats up at a rate of 1°C / min, and the aging ovens above 80°C heat up at a rate of 2°C / min. Put 8 bearings in each aging oven and carry out accelerated aging tests for different times;

[0061] (3) Take out the specimens after aging treatment successively according to the aging times of 72h, 168h, 336h, 552h, 864h, 1224h, 1632h, and 2000h, and put them into an aging oven with slow cooling. For the aging oven with a temperature exceeding 80°C, cool it at a rate of 2°C / min, and for the 80°C aging oven, cool it at a rate of 1°C / min. After cooling to room temperature, keep it warm for 48h, and test the horizontal equivalent stiffness of each bearing sample at room temperature (the test results are shown in Table 1). The horizontal ultimate deformation performance at different aging times is measured to be ≥320%;

[0062] Table 1 Aging test data at different temperatures and different aging times in Example 1

[0063]

[0064] (4) Take the horizontal equivalent stiffness change rate and heating time of the bearing samples measured at the same temperature, and use Origin software to make the horizontal equivalent stiffness change rate and heating time curves of the bearing samples at different temperatures respectively (as Figure 1 ), and obtain that the times t1, t2, t3, and t4 corresponding to the horizontal equivalent stiffness critical values of the bearing samples at 80°C, 90°C, 100°C, and 110°C are 1998h, 812h, 365h, and 185h respectively;

[0065] (5) According to the Arrhenius equation K(T) = A·e -E / RT , plot the logarithm lnt of the times t1, t2, t3, t4 against the reciprocal of the corresponding thermodynamic temperature , and obtain the fitting straight line y = 1.0835x - 23.107 by plotting each point and then using Origin software, where y represents lnt and x represents

[0066] (6) Through the fitting straight line y = 1.0835x - 23.107, the service life of the bearing at a service temperature of 23°C can be evaluated to be 714973h. In the actual use process, the service life of the bearing can be further evaluated by combining environmental impact factors (various complex factors such as light, heat, humidity, and mechanical stress), and a safety factor of 1.5 needs to be divided (Zhang Kai et al., Prediction of the storage life of butyl rubber sealing materials [J]. Sichuan Chemical Industry, 2004, 7(1): 4). Therefore, the estimated life is 54 years.

[0067] Example 2

[0068] (1) Before the test, use a compression-shear testing machine to test the horizontal equivalent stiffness and horizontal ultimate deformation performance of the bearing finished products (lead rubber bearing LRB500) of the same batch. The measured horizontal equivalent stiffness of the bearing is 1.113 kN / mm, and the horizontal ultimate deformation performance is ≥400%;

[0069] (2) Place the lead-rubber bearings LRB500 of the same batch into aging ovens with a slow temperature increase to 80°C, 90°C, 100°C, and 110°C respectively. The aging oven at 80°C is heated at a rate of 1°C / min, and the aging ovens above 80°C are heated at a rate of 2°C / min. Put 8 bearings in each aging oven and conduct accelerated aging tests for different durations.

[0070] (3) Take out the specimens after aging treatment successively according to the aging times of 72h, 168h, 336h, 552h, 864h, 1224h, 1632h, and 2280h, and place them in an aging oven with a slow temperature decrease. The aging ovens above 80°C are cooled at a rate of 2°C / min, and the aging oven at 80°C is cooled at a rate of 1°C / min. After cooling to room temperature, keep them at room temperature for 72h, and test the horizontal equivalent stiffness of each bearing sample at room temperature (the test results are shown in Table 2). The horizontal ultimate deformation performance at different aging times is all ≥ 320%.

[0071] Table 2 Aging test data at different temperatures and different aging times in Example 2

[0072]

[0073] (4) Using the horizontal equivalent stiffness change rate and heating time of the bearing samples measured at the same temperature, use Origin software to make curves of the horizontal equivalent stiffness change rate and heating time of the bearing samples at different temperatures (see Figure 3 ), and obtain the times t1, t2, t3, and t4 corresponding to the critical values of the horizontal equivalent stiffness of the bearing samples at 80°C, 90°C, 100°C, and 110°C, which are 2208h, 1097h, 446h, and 181h respectively.

[0074] (5) According to the Arrhenius equation K(T) = A·e -E / RT , use the logarithm lnt of the times t1, t2, t3, and t4 and the reciprocal of the corresponding thermodynamic temperature to plot a graph. By plotting each point and then using Origin software, obtain the fitted straight line y = 1.1346x - 24.348, where y represents lnt and x represents

[0075] (6) Through the fitted straight line y = 1.1346x - 24.348, it can be evaluated that the service life of the bearing at a service temperature of 23°C is 1159694h. In the actual use process, the service life of the bearing can be further evaluated by combining environmental influence factors (various complex factors such as light, heat, humidity, and mechanical stress), and it needs to be divided by a safety factor of 1.5. Therefore, the estimated service life is 88 years.

[0076] Example 3

[0077] (1) Before the test, use a compression-shear testing machine to test the horizontal equivalent stiffness and horizontal ultimate deformation performance of the finished bearings of the same batch (natural rubber bearing LNR600). The measured horizontal equivalent stiffness of the bearing is 1.078 kN / mm, and the horizontal ultimate deformation performance ≥ 400%;

[0078] (2) Place the natural rubber bearings LNR500 of the same batch into aging ovens with slow temperature increases of 70°C, 80°C, 90°C, and 100°C respectively. The aging ovens at 70°C and 80°C are heated at a rate of 1°C / min, and the aging ovens at 90°C and 100°C are heated at a rate of 2°C / min. Put 10 bearings in each aging oven and conduct accelerated aging tests for different times;

[0079] (3) Take out the specimens after aging treatment successively according to the aging times of 72h, 168h, 336h, 552h, 864h, 1224h, 1632h, 2000h, 2336h, and 3000h, and put them into aging ovens with slow temperature decreases. The aging ovens at 90°C and 100°C are cooled at a rate of 2°C / min, and the aging ovens at 70°C and 80°C are cooled at a rate of 1°C / min. After cooling to room temperature, keep them warm for 96h, and test the horizontal equivalent stiffness of each bearing sample at room temperature (the test results are shown in Table 3). The measured horizontal ultimate deformation performance at different aging times is ≥ 320%;

[0080] Table 3 Aging test data at different temperatures and different aging times

[0081]

[0082] (4) Use Origin software to make curves of the horizontal equivalent stiffness change rate and heating time of the bearing samples at different temperatures respectively with the horizontal equivalent stiffness change rate and heating time of the bearing samples measured at the same temperature (see Figure 3 ), and obtain that the times t1, t2, t3, and t4 corresponding to the horizontal equivalent stiffness critical values of the bearing samples at 70°C, 80°C, 90°C, and 100°C are 2981h, 1212h, 446h, and 178h respectively;

[0083] (5) According to the Arrhenius equation K(T) = A·e -E / RT , make a graph with the logarithm lnt of the times t1, t2, t3, and t4 and the reciprocal of the corresponding thermodynamic temperature . By plotting each point and then using Origin software, obtain the fitting straight line y = 1.2031x - 27.024, where y represents lnt and x represents

[0084] (6) By fitting the straight line y = 1.2031x - 27.024, the service life of the bearing at a service temperature of 23°C can be evaluated to be 806681 h. During actual use, the service life of the bearing can be further evaluated by combining environmental impact factors (various complex factors such as light, heat, humidity, mechanical stress, etc.), and a safety factor of 1.5 needs to be divided, so the estimated service life is 61 years.

Claims

1. An evaluation method for the service life of a building isolation bearing, comprising: Obtain the aging time t when the critical value of the horizontal equivalent stiffness change rate is reached from the horizontal equivalent stiffness change rate - aging time curve of the bearing sample, and then evaluate the bearing life through the fitting line of the aging time t and the thermodynamic temperature.

2. The evaluation method according to claim 1, characterized in that, The evaluation method specifically includes the following steps: (1) Conduct a horizontal equivalent stiffness test on the unaged bearing sample to be measured; (2) Gradually heat multiple groups of bearing samples to be measured to different aging temperatures for aging treatment with different aging times; (3) Take out the bearing samples that have undergone aging treatment in sequence according to the aging time, gradually cool them to room temperature and keep them warm, and measure the horizontal equivalent stiffness of each bearing sample at room temperature; (4) Make a curve with the horizontal equivalent stiffness change rate and aging time of the bearing samples measured at the same temperature. Obtain the aging time t corresponding to the critical value of the horizontal equivalent stiffness change rate of the bearing samples from the curves made at different temperatures; (5) Plot the logarithm of the aging time \(t\), \(\ln t\), against the reciprocal of the corresponding thermodynamic temperature to obtain the fitted straight line of Equation (1): lnt = E / RT + B Equation (1) In Equation (1), t is the aging time corresponding to the critical value of the horizontal equivalent stiffness of the bearing sample; E is the activation energy, with the unit of J / mol; R is the gas constant, with a value of 8.314 J / (mol·K); T is the thermodynamic temperature, with the unit of K; B is the constant term; (6) Evaluate the life of the building isolation bearing at a certain temperature through the fitting line of Equation (1).

3. The evaluation method according to claim 1 or 2, characterized in that The critical value is the change rate of the horizontal equivalent stiffness of the aged sample relative to that before aging; preferably, the critical value is 10 - 50%; and / or, The horizontal ultimate deformation of the unaged bearing sample to be measured ≥ 400%; and / or, The horizontal ultimate deformation of the aged bearing sample ≥ 320%.

4. The evaluation method according to claim 2, wherein The heating rate in step (2) is 0.5 - 2.5 °C / min. Preferably, when the aging temperature does not exceed 80 °C, the heating rate is 0.5 - 1.2 °C / min, and / or, when the aging temperature is higher than 80 °C, the heating rate is 1.8 - 2.5 °C / min.

5. The evaluation method according to claim 2, wherein In step (2): The aging treatment uses at least 3 different temperatures, preferably 3 - 5 different temperatures; and / or, The aging temperature is 50 - 200 °C, preferably 60 - 150 °C.

6. The evaluation method according to claim 2, wherein In step (2): The aging treatment uses at least 3 different times, preferably 3 - 10 different times; and / or, The aging time is 24 - 5000 h, preferably 72 - 3000 h.

7. The evaluation method according to claim 2, wherein In step (2), at least 4 bearing samples are set at different aging temperatures, preferably 8 - 10.

8. The evaluation method according to claim 2, wherein The cooling rate in step (3) is 0.5 - 2.5 °C / min. Preferably, when the aging temperature does not exceed 80 °C, the cooling rate is 0.5 - 1.2 °C / min, and / or, when the aging temperature is higher than 80 °C, the cooling rate is 1.8 - 2.5 °C / min.

9. The evaluation method according to claim 2, wherein In step (3), the heat preservation time is 16 - 144 h, preferably 48 - 96 h.

10. An evaluation method for the life of the building isolation bearing according to any one of claims 1 - 9, used to evaluate the service life of the building isolation bearing.

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