Hysteresis capability degradation evaluation method for in-service BRB buckling-restrained brace
By establishing the correspondence between the corrosion surface morphology characteristics of BRB buckling-restrained braces and the environment and age, a stochastic model was constructed and cyclic loading tests and numerical simulations were conducted. This solved the problem of assessing the degradation of hysteresis capacity of in-service BRB buckling-restrained braces, and improved the accuracy and safety of the assessment.
Patent Information
- Application Number
- CN202511799272.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-02
- Publication Date
- 2026-02-06
AI Technical Summary
Existing technologies cannot effectively assess the degradation of hysteresis capacity in in-service BRBs, leading to corrosion problems that affect the seismic resistance and safety of the structure.
By establishing the correspondence between the corrosion surface morphology characteristics of BRB buckling braces and the service environment and age, a stochastic model was constructed, and cyclic loading tests and numerical simulations were conducted to determine the relationship between corrosion characteristic parameters and hysteresis performance, and an evaluation model was established.
This enables a reliable assessment of the residual hysteretic performance of in-service BRB buckling-resistance braces, improving the accuracy of their service safety and energy dissipation capacity assessment.
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Figure CN121480192A_ABST
Abstract
Description
Technical Field
[0001] This invention pertains to the evaluation technology of seismic mitigation measures for building structures, and particularly relates to a method for evaluating the degradation of hysteresis capacity of in-service BRB buckling-restrained braces. Background Technology
[0002] Buckling-restrained braces (BRBs), as superior damping and energy-dissipating components, have been widely used in construction, industry, and energy sectors due to their outstanding hysteretic damping effect, effectively ensuring the seismic resistance and safety of engineering structures. However, long-term exposure to corrosive media in the service environment, coupled with the limited durability of current buckling-restrained brace materials, means that even with anti-corrosion measures and construction, rust cannot be avoided. This leads to degradation of their hysteretic performance, a decrease in energy dissipation capacity, and seriously affects the overall seismic resistance and safe use of the structure.
[0003] Unlike other load-bearing members, buckling-restrained braces (BRBs) are primarily used to reduce the structural energy introduced by seismic loads, rather than serving as the main load-bearing members. Therefore, performance degradation caused by corrosion is easily overlooked. However, since their main load-bearing component is the seismic load, they are highly sensitive to stress concentration caused by localized corrosion defects. Thus, it is essential to establish a method for assessing the hysteretic performance and energy dissipation capacity degradation of in-service BRBs.
[0004] Currently, quantitative characterization techniques for corrosion damage in metal structures are relatively mature, which provides a technical basis for constructing input parameters for corrosion damage in in-service BRB buckling braces. Summary of the Invention
[0005] To address the above problems, this invention provides a method for assessing the degradation of hysteresis capability in in-service BRB buckling-restrained braces.
[0006] The present invention provides a method for assessing the degradation of hysteresis capacity in in-service buckling-restrained braces, comprising the following steps:
[0007] Step 1: Establish the correspondence between the corrosion surface morphology characteristics of the main components such as the BRB buckling brace sleeve, steel core and fixed end and the service environment characteristics and service age.
[0008] First, through field surveys, corrosion samples of major components of BRB buckling-restrained braces under different service environments and service years were collected. Their morphological characteristics were analyzed to obtain morphological parameters such as pit shape, pit depth, and pit density. Second, accelerated indoor testing of BRB buckling-restrained braces was conducted, setting different corrosion environment indicators (such as pH value, humidity, temperature, and chloride-sulfur ion concentration) and age plans. The morphological parameters such as pit shape, pit depth, and pit density of the corrosion surfaces of major components of BRB buckling-restrained braces under different corrosion environments and ages were recorded throughout the process. Third, the morphological parameters of the corrosion surfaces of major components of BRB buckling-restrained braces under actual service conditions were compared and analyzed with the data obtained from the accelerated indoor tests to establish the correspondence between the morphological characteristics of the corrosion surface of the BRB buckling-restrained brace substrate and the service environment indicators and service age.
[0009] Step 2: Establish a stochastic model of the rusted surface morphology of BRB substrate under corrosive environment based on random field theory.
[0010] Statistical methods were used to analyze the corrosion surface morphology data of the main components of the BRB buckling-restrained brace. Using random field theory, considering the randomness of the corrosion surface morphology, the shape, depth, and density of rust pits were used as random variables to construct a stochastic model that can reflect the randomness of the corrosion surface morphology of the BRB buckling-restrained brace under service conditions.
[0011] Step 3: Conduct cyclic loading tests to determine the correlation.
[0012] Mechanical tests were conducted on the substrates of the BRB buckling-restrained braces and their main components with different degrees of corrosion. For substrates with different degrees of corrosion, the main mechanical properties and hysteretic performance parameters were obtained through tests, and the relationship between corrosion characteristic parameters and hysteretic performance of the corroded substrate was determined. Similarly, for BRB buckling-restrained braces with different degrees of corrosion, the relationship between corrosion characteristic indicators and seismic performance of corroded BRB buckling-restrained braces was determined through tests.
[0013] Step 4: Numerical simulation.
[0014] Using numerical simulation, the corrosion surface morphology characteristics of the main components of the BRB buckling-restrained brace, obtained by controlling the service environment characteristics and service age, are used as input parameters. Based on the previously established stochastic model of the corrosion surface morphology of the main components of the BRB buckling-restrained brace under corrosive conditions, a numerical model of the corroded BRB buckling-restrained brace is constructed. The mechanical behavior of the corroded BRB buckling-restrained brace under different working conditions is simulated through this numerical model.
[0015] Step 5: Validation and evaluation method acquisition.
[0016] By comparing the hysteresis test results and numerical analysis results of corroded BRB buckling-resisted braces, the numerical simulation is considered reasonable when the error between the two is within an acceptable range, i.e., the accuracy meets the engineering requirements. Based on a numerical analysis method with sufficient accuracy, the number of cases is expanded by changing the service environment characteristic indicators and service age. Using the exhaustive method, through the analysis of a large number of cases, an evaluation method is proposed to convert the residual hysteresis performance of in-service BRB buckling-resisted braces into service environment characteristic indicators and service age, and an evaluation model is established.
[0017] Furthermore, the service environment in step 1 includes, but is not limited to, pH value, humidity, temperature, and concentration of chloride and sulfur ions; the morphological characteristics of the corroded surface include, but are not limited to, the shape of the rust pit, the depth of the pit, the width of the pit, and the density of the pit.
[0018] Furthermore, in step 2, the statistical methods for the corrosion surface morphology data mentioned include, but are not limited to, random field theory analysis methods.
[0019] Furthermore, in step 3, the mechanical properties and hysteretic performance parameters include, but are not limited to, yield strength, ultimate strength, and ductility; the seismic performance parameters include, but are not limited to, bearing capacity and energy dissipation capacity.
[0020] Furthermore, the methods for expanding the numerical test cases in step 5 include, but are not limited to, exhaustive enumeration.
[0021] The beneficial technical effects of this invention compared to the prior art are as follows:
[0022] This invention expands the evaluation perspective of the hysteresis capacity and energy dissipation performance of in-service BRB buckling-resistance braces, and provides a method for evaluating the working status of such vibration reduction measures during their service life, thereby improving the service safety of such vibration reduction measures.
[0023] This invention comprehensively considers the influence of factors such as corrosion on its hysteresis capability, and accurately establishes a relationship model between the service environment, age and corrosion surface morphology characteristics of in-service BRB buckling-resisted braces, which can realize a reliable and effective assessment of the remaining hysteresis performance and energy dissipation capability of in-service BRB buckling-resisted braces. Attached Figure Description
[0024] Figure 1 This diagram shows the relationship between the morphological characteristics of the corroded surface of the BRB buckling brace and its service environment indicators and service age.
[0025] Figure 2 A schematic diagram of a random model of the morphology of a rusted surface on a BRB substrate (including a probability cloud map of rust pit distribution).
[0026] Figure 3 The curves show the relationship between the corrosion characteristic parameters of the substrate and its hysteretic properties (yield strength, ductility index).
[0027] Figure 4 The figure shows the fitted equations relating corrosion characteristic parameters of BRB buckling-resistance braces to hysteretic performance (bearing capacity and hysteretic parameters).
[0028] Figure 5 A comparison of the numerical simulation hysteresis curve and the experimental hysteresis curve for the corroded BRB support.
[0029] Figure 6 The curves represent the residual hysteresis performance evaluation curves of in-service BRB buckling-resistance braces. Detailed Implementation
[0030] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0031] Example:
[0032] Test subject: The BRB buckling-restrained brace, which has been in service for about 10 years in a large frame building structure, was selected as the evaluation object. The total length of the buckling-restrained brace is 3500mm, the cross-sectional dimensions are 150mm×80mm, and it is welded from the outer cylinder restraint unit (made of Q345 steel), the fixed end, and the side plate, all of which are made of Q345 steel (currently replaced by domestic Q355 steel). The core material is LYP160 strip steel with dimensions of 120mm×50mm.
[0033] Step 1: Establish the correspondence between the morphology of the corroded surface and the service environment and age.
[0034] First, an on-site survey was conducted to monitor the service environment of the BRB support in the building. The characteristic parameters recorded are as follows: pH value 6.5, ambient humidity 70%, average temperature 25℃, chloride ion concentration in the air 0.05%, and service life 10 years.
[0035] Then, corrosion samples were collected and morphology measurements were performed. Three typical corrosion samples were collected from the surface of the BRB support, and the surface characteristics of the corrosion were measured using a three-dimensional morphologist. The results showed that the average depth of the rust pits was 0.2 mm, the average width was 0.5 mm, the density of rust pits was 5 pits / cm², and the maximum corrosion depth was 0.4 mm.
[0036] Next, supplementary indoor accelerated corrosion test data were obtained. Five groups of accelerated corrosion tests with different environmental parameters were set up (as shown in Table 1). The test duration of each group corresponded to different service ages (1 year, 3 years, 5 years, 8 years, and 10 years). Corrosion surface morphology data under each operating condition were obtained and combined with field data for analysis to establish the correspondence between "corrosion surface morphology characteristics (rust pit depth, density, etc.) - service environment indicators - service age" (see Table 1). Figure 1 ).
[0037] Table 1. Gradient settings for simulation experiments
[0038]
[0039] Step 2: Establish a stochastic model of the morphology of the rusted surface.
[0040] Based on the 100 sets of corrosion surface morphology data obtained in step 1 (50 sets from field testing and 50 sets from accelerated testing), statistical methods were used to analyze the probability distribution characteristics of rust pit depth, width, and density (such as normal distribution and Weibull distribution). A stochastic model was constructed based on random field theory: using service environment parameters and age as input variables, the output is a stochastic distribution function of factors such as rust pit depth, width, and density (see...). Figure 2 This model can randomly generate BRB surface morphology under different corrosion levels.
[0041] Step 3: Determine the correlation through cyclic loading tests.
[0042] First, material property tests were conducted on the main components of the BRB buckling-restrained brace. Five Q345 steel specimens with different corrosion degrees (rust pit depths of 0 mm, 0.1 mm, 0.2 mm, 0.3 mm, and 0.4 mm) were selected and subjected to cyclic loading tests (loading frequency 0.1 Hz, strain amplitude ±2%). The yield strength, ultimate strength, and ductility of each specimen were obtained, and relationship curves between "corrosion characteristic parameter (rust pit depth) - yield strength" and "corrosion characteristic parameter (rust pit density) - ductility" were established (see...). Figure 3 ).
[0043] Then, BRB support tests were conducted. Cyclic loading tests were performed on the BRB supports corresponding to the five corrosion levels mentioned above, and their load-bearing capacity and hysteresis performance (energy dissipation parameters) were measured. Relationship equations between "corrosion characteristic parameters - load-bearing capacity" and "corrosion characteristic parameters - energy dissipation parameters" were established (see...). Figure 4 ).
[0044] Step 4: Build and validate the numerical model.
[0045] First, a numerical analysis model of the corroded BRB buckling-restrained brace was constructed. Based on the stochastic model construction method in step 2, a three-dimensional geometric model of the corroded BRB buckling-restrained brace was established in the finite element software. The corrosion morphology characteristics parameters (rust pit depth 0.2 mm, density 5 pits / cm²) from the field survey were input, and the material properties (yield strength 235 MPa) and boundary conditions (fixed at both ends) were set.
[0046] Then, a numerical method was used to conduct hysteresis test analysis of the corroded BRB buckling-restrained brace. The cyclic loading process was simulated, and the hysteresis curves of the BRB brace were obtained (see...). Figure 5 (Solid line in the middle).
[0047] Finally, verification was performed. The numerical simulation results were compared with the experimental hysteresis curves of BRB supports with the same degree of corrosion in step 3 (see...). Figure 5 The error was 3.2% (less than 5%) when compared with the dashed line, verifying the correctness of the model.
[0048] Step 5: Expand the examples to obtain evaluation methods.
[0049] By varying the magnitude and duration of service environment indicators to achieve different corrosion environments and corrosion ages, numerical methods were used to expand the experimental data of the BRB hysteresis test for rust to a certain number (e.g., 2000 sets of cases), resulting in an evaluation chart of "service environment-age-residual hysteresis performance (load capacity, energy dissipation parameters)" (see...). Figure 6 The degree of hysteresis degradation supported by BRB can be directly queried based on actual environmental parameters and age.
[0050] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for assessing the degradation of hysteresis capacity in in-service BRB buckling-restrained braces, characterized in that, Includes the following steps: Step 1: Establish the correspondence between the corrosion surface morphology characteristics of BRB buckling braces and service environment characteristics and service age; First, through field surveys, corrosion samples of BRB buckling-restrained braces under different service environments and service ages were collected, and their corrosion surface morphology characteristics were recorded. At the same time, indoor accelerated tests were conducted, setting different service environment characteristic indicators and test times to simulate the corrosion process of BRB buckling-restrained braces and obtain corresponding corrosion surface morphology characteristics. Data obtained from field surveys and indoor accelerated tests were organized and analyzed to establish the correspondence between the corrosion surface morphology characteristics of each component of the BRB buckling brace and service environment indicators and service age. Step 2: Establish a stochastic model of the rusted surface morphology of BRB buckling-resistive braces under corrosive conditions based on random field theory; Statistical methods were used to analyze the corrosion surface morphology data of each component of the BRB buckling brace. Based on random field theory, considering the randomness of corrosion surface morphology, the shape, depth and density of rust pits were used as random variables to construct a stochastic model that can reflect the randomness of the corrosion surface morphology of the BRB substrate under corrosive environment. Step 3: Conduct cyclic loading tests to determine the correlation; Cyclic loading tests were conducted on various components of the BRB and the entire support system with different degrees of corrosion. For component materials with different degrees of corrosion, their mechanical properties and hysteresis parameters were obtained through tests, and the relationship between corrosion characteristic indicators and the mechanical properties and hysteresis parameters of each corroded component material was determined. Similarly, cyclic loading tests were conducted on BRB buckling-resisted braces with different degrees of corrosion to determine the relationship between corrosion characteristic indicators and the vibration damping and energy dissipation capacity of corroded BRB buckling-resisted braces. Step 4: Numerical simulation; Using numerical simulation, the corrosion surface morphology characteristics of each component of the BRB buckling-restrained brace, obtained by controlling the service environment characteristics and service age, are used as input parameters. Based on the previously established stochastic model of the corrosion surface morphology of the BRB substrate under corrosive conditions, a numerical model of the corroded BRB buckling-restrained brace is constructed. The mechanical behavior of the corroded BRB buckling-restrained brace under different working conditions is simulated through this numerical model. Step 5: Validation and evaluation method acquisition; By comparing the experimental results and numerical analysis results of the materials of each component of the corroded BRB buckling-restrained brace and the brace as a whole, the correctness of the numerical simulation is verified when the error between the two meets the engineering accuracy requirements. Based on a numerical analysis method with sufficient accuracy, the number of cases is expanded by changing the service environment characteristic indicators and service age. Through the analysis of a large number of cases, an evaluation method for converting the residual hysteretic performance of in-service BRB buckling-restrained braces by service environment characteristic parameters and service age is proposed, and an evaluation model is established.
2. The method for assessing the degradation of hysteresis capacity of in-service BRB buckling-restrained braces according to claim 1, characterized in that, The service environment in step 1 includes, but is not limited to, pH value, humidity, temperature, and concentration of chloride and sulfur ions; the morphological characteristics of the corroded surface include, but are not limited to, the shape of the rust pit, the depth of the pit, the width of the pit, and the density of the pit.
3. The method for assessing the hysteresis capacity degradation of in-service BRB buckling-restrained braces according to claim 1, characterized in that, In step 2, the statistical methods for corroded surface morphology data mentioned include, but are not limited to, random field theory analysis methods.
4. The method for assessing the degradation of hysteresis capacity of in-service BRB buckling-restrained braces according to claim 1, characterized in that, The mechanical properties and hysteretic performance parameters in step 3 include, but are not limited to, yield strength, ultimate strength, and ductility; the seismic performance parameters include, but are not limited to, bearing capacity and energy dissipation capacity.
5. The method for assessing the hysteresis capacity degradation of in-service BRB buckling-restrained braces according to claim 1, characterized in that, The methods for expanding the numerical test cases in step 5 include, but are not limited to, exhaustive enumeration.