Numerical simulation method for chloride ion transmission of unsaturated concrete in anchoring area of post-tensioned member

Abstract

The invention relates to the technical field of concrete, in particular to a post-tensioned member anchoring area unsaturated concrete chloride ion transmission numerical simulation method which comprises the following steps: constructing an anchoring area chloride ion transmission calculation model: in anchoring area unsaturated concrete, establishing a chloride ion transmission numerical model considering dry-wet cycle action and stress influence, the model mainly comprises chloride ion diffusion flux and convection flux; initial conditions and boundary conditions are determined, wherein the initial conditions comprise initial chloride ion concentration distribution and moisture content of unsaturated concrete in the anchoring area, and the boundary conditions comprise surface chloride ion concentration and a dry-wet cycle period; according to the method, a comprehensive numerical simulation process is provided by systematically constructing an anchoring area chloride ion transmission calculation model and considering dry-wet cycle and stress influence, the chloride ion transmission process in a complex environment can be accurately simulated, and the method has the advantages that the operation is simple, the cost is low, and the method is suitable for large-scale popularization and application. And the applicability and reliability of the model are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and specifically to a numerical simulation method for chloride ion transport in unsaturated concrete in the anchorage zone of post-tensioned members. Background Art

[0002] Post-tensioned prestressed concrete members are widely used in projects such as bridges and buildings. However, due to long-term exposure to chloride ion environments such as the ocean, salt spray, and deicing salts, the anchorage zone of prestressed concrete members is prone to chloride ion erosion, leading to steel bar corrosion and affecting the durability and safety of the structure. Studying the transport process of chloride ions in unsaturated concrete in the anchorage zone and then evaluating the durability of concrete structures has important engineering significance;

[0003] Currently, research on chloride ion transport in concrete mainly focuses on saturated conditions, lacking a systematic study on the chloride ion transport process in unsaturated concrete. In addition, the anchorage zone is subjected to complex wet-dry cycles and stress actions, and traditional chloride ion transport models are difficult to accurately describe the chloride ion transport behavior under these complex environments. Therefore, it is particularly necessary to establish a numerical simulation method for chloride ion transport in unsaturated concrete in the anchorage zone that can consider the effects of wet-dry cycles and stress. Therefore, a numerical simulation method for chloride ion transport in unsaturated concrete in the anchorage zone of post-tensioned members is proposed to address the above problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a numerical simulation method for chloride ion transport in unsaturated concrete in the anchorage zone of post-tensioned members to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A numerical simulation method for chloride ion transport in unsaturated concrete in the anchorage zone of post-tensioned members, comprising the following steps:

[0007] a. Construct a calculation model for chloride ion transport in the anchorage zone: In unsaturated concrete in the anchorage zone, establish a numerical model for chloride ion transport considering the effects of wet-dry cycles and stress. The model mainly includes chloride ion diffusion flux and convective flux;

[0008] b. Determine the initial conditions and boundary conditions: The initial conditions include the initial chloride ion concentration distribution and moisture content of unsaturated concrete in the anchorage zone, and the boundary conditions include the surface chloride ion concentration and wet-dry cycle period;

[0009] c. Input material parameters: Input the physical and mechanical parameters of unsaturated concrete in the anchorage zone, including diffusion coefficient, moisture diffusion coefficient, and unsaturated characteristic parameters of the material;

[0010] d. Numerical solution: Use finite element analysis software (such as COMSOL, ABAQUS) to perform numerical solutions on the established model, simulate the chloride ion transport process under the action of wet-dry cycles and stress coupling, and obtain the chloride ion concentration distribution at different times and depths;

[0011] e. Result verification: Verify the accuracy of the numerical model by comparing with the measured data, and conduct parameter sensitivity analysis to determine the reliability of the model.

[0012] Preferably, the chloride ion diffusion flux and convective flux are calculated according to the following formulas respectively:

[0013] Chloride ion diffusion flux:

[0014] where, J d is the diffusion flux, D is the diffusion coefficient, C is the chloride ion concentration, and x is the transport path;

[0015] Convective flux: J c = ρ·v·C

[0016] where, J c is the convective flux, ρ is the density of water, and v is the convective velocity.

[0017] Preferably, the initial conditions include the initial chloride ion concentration gradient and initial moisture content in the concrete of the anchorage area, and the boundary conditions include the change of surface chloride ion concentration and the frequency and time ratio of wet-dry cycles; the initial chloride ion concentration gradient is determined by laboratory measurement or on-site sampling, and the initial moisture content is set according to the environmental conditions and the curing situation of the concrete; the boundary conditions need to consider the change of the concentration of environmental chloride ion sources, specifically including the chloride ion concentration in the air, the frequency and intensity of rainfall or seawater erosion, etc.

[0018] Preferably, the material parameters include the diffusion coefficient of concrete, moisture diffusion coefficient, porosity, and unsaturated characteristic parameters, and these parameters are determined through experiments; further, the diffusion coefficient and moisture diffusion coefficient of concrete are obtained through ion diffusion experiments and water absorption experiments, and the porosity is determined through pore structure analysis methods (such as mercury intrusion method, nitrogen adsorption method); the unsaturated characteristic parameters include the moisture absorption isotherm and desorption isotherm of concrete.

[0019] Preferably, the numerical solution adopts the finite element method, and through sub-region and sub-step iterative calculations, the concentration distribution of chloride ions at different depths and times is gradually obtained; the numerical solution process includes steps such as mesh generation, initial value setting, boundary condition application, and solver selection; mesh generation needs to consider the balance between calculation accuracy and calculation efficiency, the initial value setting is based on the initial conditions; the boundary condition application needs to combine the actual engineering situation, and the solver selection is determined according to the nonlinear degree and calculation scale of the problem.

[0020] Preferably, the result verification includes comparing and analyzing the numerical simulation results with the measured data of chloride ion concentration in the actual anchorage zone, and verifying the accuracy and reliability of the model through methods such as goodness of fit and error analysis; the goodness of fit is evaluated by indicators such as correlation coefficient and mean square error, and the error analysis is carried out by analyzing the deviation between the simulation results and the measured data.

[0021] Preferably, by performing a sensitivity analysis on the parameters, the influence degrees of wet-dry cycle frequency, principal tensile stress, diffusion coefficient, etc. on chloride ion transport are determined, the model parameters are optimized, and the accuracy of the numerical simulation results is improved; the sensitivity analysis includes single-factor analysis and multi-factor analysis. By changing the value ranges of each parameter, the changes in chloride ion concentration distribution are observed to determine the influence degree of each parameter on the results; advanced optimization methods such as genetic algorithm and particle swarm optimization algorithm can be used to optimize the model parameters to improve the calculation accuracy and stability of the numerical model.

[0022] Preferably, the chloride ion diffusion coefficient D is calculated according to the following empirical formula with the change of concrete humidity:

[0023]

[0024] where D0 is the reference diffusion coefficient, w is the current humidity, w0 is the reference humidity, and n is an empirical constant.

[0025] Preferably, the influence of the wet-dry cycle action on chloride ion transport is calculated by the following formula:

[0026]

[0027] where C(x, t) is the chloride ion concentration at time t and position x, C0 is the average chloride ion concentration, ΔC is the chloride ion concentration fluctuation amplitude, and T is the wet-dry cycle period.

[0028] Preferably, the stress influence describes the stress coupling effect in the chloride ion transport process by the following formula:

[0029]

[0030] where J is the chloride ion flux caused by stress, R is the gas constant, T is the absolute temperature, and σ is the stress.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] 1. In the present invention, by systematically constructing a calculation model for chloride ion transport in the anchorage zone, considering the influence of wet-dry cycle and stress, a comprehensive numerical simulation process is provided, which can accurately simulate the chloride ion transport process in a complex environment, and improves the applicability and reliability of the model.

[0033] 2. In the present invention, by describing in detail the setting methods of initial conditions and boundary conditions, the input parameters of numerical simulation are ensured to be more scientific and reasonable, which can better reflect the complex environmental conditions in actual engineering and improve the accuracy and practicality of simulation results.

[0034] 3. In the present invention, by accurately measuring and inputting the physical and mechanical parameters of concrete, such as diffusion coefficient, moisture diffusion coefficient, porosity and unsaturated characteristic parameters, the description of material characteristics in the numerical simulation model is made more accurate, thereby improving the reliability and repeatability of simulation results.

[0035] 4. In the present invention, the finite element method is adopted for numerical solution, and iterative calculations are carried out regionally and step by step, which improves the calculation efficiency and accuracy, can describe in detail the transport process of chloride ions in concrete, provides high-precision simulation results, and is helpful for engineering design and evaluation.

[0036] 5. In the present invention, through detailed result verification steps, the accuracy and reliability of the numerical simulation model are ensured, so that the simulation results can truly reflect the chloride ion transport behavior in actual engineering and provide a reliable basis for engineering design and durability evaluation.

[0037] 6. In the present invention, by carrying out sensitivity analysis and optimization on parameters, the accuracy and reasonableness of model parameters are improved, making the numerical simulation results more accurate and reliable, providing a scientific basis for chloride ion transport simulation, and being able to better predict the durability of concrete structures under complex environmental conditions.

[0038] 7. In the present invention, by providing an empirical formula for the variation of chloride diffusion coefficient with humidity, the model can dynamically adjust the diffusion coefficient, more accurately reflect the chloride ion transport behavior in actual situations, and improve the accuracy of simulation results.

[0039] 8. In the present invention, by describing the influence of wet-dry cycles on chloride ion transport with a formula, the numerical model can accurately simulate the change of chloride ion concentration under wet-dry cycles, and improve the authenticity and reliability of simulation results.

[0040] 9. In the present invention, by describing the influence of stress on chloride ion transport with a formula, the model can consider the stress coupling effect and improve the adaptability and accuracy of simulation results to complex stress conditions in actual engineering. Specific embodiments

[0041] The present invention provides a technical solution:

[0042] A numerical simulation method for chloride ion transport in unsaturated concrete in the anchorage zone of post-tensioned members, comprising the following steps:

[0043] a. Construct a calculation model for chloride ion transport in the anchorage zone: In unsaturated concrete in the anchorage zone, establish a numerical model for chloride ion transport considering the effects of wet-dry cycles and stress. The model mainly includes chloride ion diffusion flux and convective flux.

[0044] b. Determine the initial conditions and boundary conditions: The initial conditions include the initial chloride ion concentration distribution and moisture content of unsaturated concrete in the anchorage zone, and the boundary conditions include the surface chloride ion concentration and the wet-dry cycle period.

[0045] c. Input material parameters: Input the physical and mechanical parameters of unsaturated concrete in the anchorage zone, including the diffusion coefficient, moisture diffusion coefficient, and unsaturated characteristic parameters of the material.

[0046] d. Numerical solution: Use finite element analysis software (such as COMSOL, ABAQUS) to numerically solve the established model, simulate the chloride ion transport process under the coupling action of wet-dry cycles and stress, and obtain the chloride ion concentration distribution at different times and depths.

[0047] e. Result verification: Verify the accuracy of the numerical model by comparing with the measured data, and conduct a parameter sensitivity analysis to determine the reliability of the model.

[0048] By systematically constructing a chloride ion transport model, determining the initial and boundary conditions, inputting material parameters, and performing numerical solution and verification, a comprehensive numerical simulation process is provided, which can accurately simulate the chloride ion transport process in unsaturated concrete in the anchorage zone and help evaluate the durability of concrete structures.

[0049] The chloride ion diffusion flux and convective flux are calculated according to the following formulas respectively:

[0050] Chloride ion diffusion flux:

[0051] where J d is the diffusion flux, D is the diffusion coefficient, C is the chloride ion concentration, and x is the transport path.

[0052] Convective flux: J c = ρ·v·C

[0053] where J c is the convective flux, ρ is the density of water, and v is the convective velocity.

[0054] This method provides clear calculation formulas for chloride ion diffusion and convective flux, making the numerical model more accurate, capable of more accurately describing the transport behavior of chloride ions in unsaturated concrete, and improving the reliability of simulation results.

[0055] The initial conditions include the initial chloride ion concentration gradient and the initial moisture content in the concrete of the anchorage zone, and the boundary conditions include the change in the surface chloride ion concentration and the frequency and time ratio of wet-dry cycles; the initial chloride ion concentration gradient is determined by laboratory measurement or on-site sampling, and the initial moisture content is set according to environmental conditions and the curing condition of the concrete; the boundary conditions need to take into account the change in the concentration of environmental chloride sources, specifically including the chloride ion concentration in the air, the frequency and intensity of rainfall or seawater erosion, etc.

[0056] These conditions have an important impact on the chloride ion transport process. By reasonably setting the initial conditions and boundary conditions, it is possible to ensure that the numerical simulation results are consistent with the actual situation and improve the accuracy and reliability of the simulation.

[0057] The material parameters include the diffusion coefficient of concrete, the moisture diffusion coefficient, the porosity, and the unsaturated characteristic parameters, and these parameters are determined through experiments; further, the diffusion coefficient and moisture diffusion coefficient of concrete are obtained through ion diffusion experiments and water absorption experiments, and the porosity is determined through pore structure analysis methods (such as mercury intrusion porosimetry, nitrogen adsorption method); the unsaturated characteristic parameters include the moisture adsorption isotherm and the desorption isotherm of concrete.

[0058] These parameters reflect the water absorption and dehydration performance of concrete under different humidity conditions. By accurately determining the material parameters, it is possible to better describe the physical and mechanical properties of concrete, thereby improving the accuracy of the numerical model.

[0059] The numerical solution adopts the finite element method, and through sub-region and step-by-step iterative calculations, the concentration distribution of chloride ions at different depths and times is gradually obtained; the numerical solution process includes steps such as mesh generation, initial value setting, boundary condition application, and solver selection; mesh generation needs to consider the balance between calculation accuracy and calculation efficiency, and the initial value setting is based on the initial conditions; boundary condition application needs to be combined with the actual engineering situation, and the solver selection is determined according to the nonlinear degree and calculation scale of the problem.

[0060] Through a reasonable numerical solution strategy, it is possible to efficiently simulate the chloride ion transport process in concrete and obtain high-precision simulation results.

[0061] The result verification includes comparing and analyzing the numerical simulation results with the measured chloride ion concentration data in the actual anchorage zone, and verifying the accuracy and reliability of the model through methods such as goodness of fit and error analysis; the goodness of fit is evaluated through indicators such as the correlation coefficient and the mean square error, and the error analysis is carried out by analyzing the deviation between the simulation results and the measured data.

[0062] During the verification process, considering the consistency between the experimental conditions and the numerical simulation conditions, multiple simulations are carried out by adjusting the model parameters to improve the goodness of fit and reliability of the model.

[0063] By performing a sensitivity analysis on the parameters, determine the influence degrees of factors such as wet-dry cycle frequency, principal tensile stress, and diffusion coefficient on chloride ion transport, optimize the model parameters, and improve the accuracy of the numerical simulation results. The sensitivity analysis includes single-factor analysis and multi-factor analysis. By changing the value ranges of the parameters, observe the changes in the chloride ion concentration distribution, and determine the influence degrees of the parameters on the results. Advanced optimization methods such as genetic algorithms and particle swarm optimization algorithms can be used to optimize the model parameters, improving the calculation accuracy and stability of the numerical model.

[0064] Through sensitivity analysis and parameter optimization, the chloride ion transport process in complex environments can be simulated more accurately, providing a reliable basis for the durability assessment of concrete structures.

[0065] The chloride ion diffusion coefficient D changes with the humidity of the concrete and is calculated according to the following empirical formula:

[0066]

[0067] Where D0 is the reference diffusion coefficient, w is the current humidity, w0 is the reference humidity, and n is an empirical constant.

[0068] By providing an empirical formula for the change of chloride ion diffusion coefficient with humidity, the model can dynamically adjust the diffusion coefficient, more accurately reflect the chloride ion transport behavior in the actual situation, and improve the accuracy of the simulation results.

[0069] The influence of the wet-dry cycle action on chloride ion transport is calculated by the following formula:

[0070]

[0071] Where C(x, t) is the chloride ion concentration at time T and position x, C 0 is the average chloride ion concentration, ΔC is the chloride ion concentration fluctuation amplitude, and T is the wet-dry cycle period.

[0072] By describing the influence of the wet-dry cycle on chloride ion transport with a formula, the numerical model can accurately simulate the change of chloride ion concentration under the wet-dry cycle, improving the authenticity and reliability of the simulation results.

[0073] The stress influence describes the stress coupling effect in the chloride ion transport process through the following formula:

[0074]

[0075] Where J σ is the chloride ion flux caused by stress, R is the gas constant, T is the absolute temperature, and σ is the stress.

[0076] Describe the influence of stress on chloride ion transport through formulas, enabling the model to consider the stress coupling effect and improving the adaptability and accuracy of simulation results to complex stress conditions in practical engineering.

[0077] In this article, specific examples are used to elaborate on the principle and implementation mode of the present invention. The description of the above examples is only used to help understand the method and its core idea of the present invention. The above is only the preferred implementation mode of the present invention. It should be noted that due to the limited nature of written expression and the objectively infinite specific structures, for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements, refinements or changes can be made, or the above technical features can be combined in an appropriate manner; these improvements, refinements, changes or combinations, or directly applying the concept and technical solution of the invention to other occasions without improvement, should all be regarded as the protection scope of the present invention.

Claims

1. Numerical simulation method for chloride ion transmission in unsaturated concrete in the anchorage zone of post-tensioned members, characterized by: The following steps are involved: a. Construct a calculation model for chloride ion transport in the anchorage area: In the unsaturated concrete in the anchorage area, a numerical model for chloride ion transport is established that takes into account the effects of dry-wet cycles and stress. The model mainly includes chloride ion diffusion flux and convection flux; b. Determine the initial conditions and boundary conditions: the initial conditions include the initial chloride ion concentration distribution and moisture content of the unsaturated concrete in the anchoring area, and the boundary conditions include the surface chloride ion concentration and the dry-wet cycle period; c. Input material parameters: Input the physical and mechanical parameters of the unsaturated concrete in the anchoring area, including diffusion coefficient, water diffusion coefficient and unsaturated characteristic parameters of the material; d. Numerical solution: Use finite element analysis software (such as COMSOL, ABAQUS) to numerically solve the established model, simulate the chloride ion transport process under the action of dry-wet cycle and stress coupling, and obtain the chloride ion concentration distribution at different time and depth; e. Result verification: Verify the accuracy of the numerical model by comparing it with the measured data, and conduct parameter sensitivity analysis to determine the reliability of the model.

2. The numerical simulation method for chloride ion transmission in unsaturated concrete in the anchorage zone of a post-tensioned member according to claim 1, characterized in that: The chloride ion diffusion flux and convection flux are calculated according to the following formulas: Chloride ion diffusion flux: Among them, J d is the diffusion flux, D is the diffusion coefficient, C is the chloride ion concentration, and x is the transmission path; Convective flux: J c =ρ·υ·C Among them, J c is the convective flux, ρ is the density of water, and υ is the convection velocity.

3. The numerical simulation method for chloride ion transmission in unsaturated concrete in the anchorage zone of a post-tensioned member according to claim 1, characterized in that: The initial conditions include the initial chloride ion concentration gradient and the initial moisture content in the concrete of the anchoring area, and the boundary conditions include the change in surface chloride ion concentration and the frequency and time ratio of dry-wet cycles; the initial chloride ion concentration gradient is determined by laboratory measurement or on-site sampling, and the initial moisture content is set according to environmental conditions and the curing condition of the concrete; the boundary conditions need to take into account the concentration changes of environmental chloride ion sources, specifically including the chloride ion concentration in the air, the frequency and intensity of rainfall or seawater erosion, etc.

4. The numerical simulation method for chloride ion transmission in unsaturated concrete in the anchorage zone of a post-tensioned member according to claim 1, characterized in that: The material parameters include the diffusion coefficient, moisture diffusion coefficient, porosity and unsaturated characteristic parameters of the concrete, and these parameters are determined through experiments; further, the diffusion coefficient and moisture diffusion coefficient of the concrete are obtained through ion diffusion experiments and water absorption experiments, and the porosity is determined by pore structure analysis methods (such as mercury injection method and nitrogen adsorption method); the unsaturated characteristic parameters include the moisture absorption isotherm and dehumidification isotherm of the concrete.

5. The numerical simulation method for chloride ion transmission in unsaturated concrete in the anchorage zone of a post-tensioned member according to claim 1, characterized in that: The numerical solution adopts the finite element method, and through iterative calculation in different regions and steps, the concentration distribution of chloride ions at different depths and times is gradually obtained; the numerical solution process includes the steps of grid division, initial value setting, boundary condition application and solver selection; grid division needs to consider the balance between calculation accuracy and calculation efficiency, and the initial value setting is based on the initial conditions; the boundary condition application needs to be combined with the actual engineering situation, and the solver selection is determined according to the nonlinear degree of the problem and the calculation scale.

6. The numerical simulation method for chloride ion transmission in unsaturated concrete in the anchorage zone of a post-tensioned member according to claim 1, characterized in that: The result verification includes comparing and analyzing the numerical simulation results with the chloride ion concentration measurement data of the actual anchoring area, and verifying the accuracy and reliability of the model through methods such as goodness of fit and error analysis; the goodness of fit is evaluated by indicators such as correlation coefficient and mean square error, and the error analysis is carried out by analyzing the deviation between the simulation results and the measured data.

7. The numerical simulation method for chloride ion transmission in unsaturated concrete in the anchorage zone of a post-tensioned member according to claim 1, characterized in that: By conducting sensitivity analysis on parameters, the influence of dry-wet cycle frequency, principal tensile stress, diffusion coefficient, etc. on chloride ion transport is determined, model parameters are optimized, and the accuracy of numerical simulation results is improved; Sensitivity analysis includes single-factor analysis and multi-factor analysis. By changing the value range of each parameter and observing the changes in the distribution of chloride ion concentration, the influence of each parameter on the result can be determined. Advanced optimization methods such as genetic algorithms and particle swarm optimization algorithms can be used to optimize model parameters to improve the calculation accuracy and stability of the numerical model.

8. The numerical simulation method for chloride ion transmission in unsaturated concrete in the anchorage zone of a post-tensioned member according to claim 1, characterized in that: The chloride ion diffusion coefficient D varies with the concrete humidity according to the following empirical formula: Among them, D0 is the reference diffusion coefficient, w is the current humidity, w0 is the reference humidity, and n is the empirical constant.

9. The numerical simulation method for chloride ion transmission in unsaturated concrete in the anchorage zone of a post-tensioned member according to claim 1, characterized in that: The effect of the dry-wet cycle on chloride ion transport is calculated by the following formula: Where C(x,t) is the chloride ion concentration at time t and position x, C0 is the average chloride ion concentration, ΔC is the fluctuation amplitude of chloride ion concentration, and T is the dry-wet cycle period.

10. The numerical simulation method for chloride ion transmission in unsaturated concrete in the anchorage zone of a post-tensioned member according to claim 1, characterized in that: The stress effect is described by the following formula to describe the stress coupling effect during chloride ion transport: Among them, J σ is the chloride ion flow caused by stress, R is the gas constant, T is the absolute temperature, and σ is the stress.

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