A numerical simulation method for investigating the bond performance between unevenly corroded ribbed steel bars and concrete members

Abstract

The application provides a numerical simulation method for exploring the bonding performance of unevenly corroded ribbed steel bars and concrete members. Steel bar corrosion leads to loss of steel bar cross-sectional area, concrete corrosion cracking, and reduction of bonding performance, finally leading to reduction of structure durability and serious influence on overall performance of the structure. Since the process of testing the bonding performance of corroded steel bar concrete structures is relatively complex and the monitoring process is relatively difficult, it is particularly necessary to accurately simulate the process of testing the bonding performance of corroded steel bar concrete structures. The application analyzes the bonding failure of corroded steel bar concrete in two stages, combines the existing reference formula in model establishment, contact relationship and boundary conditions, skillfully simulates the bonding effect between the steel bar and the concrete and the influence of uneven corrosion on the structure, converts the complex corrosion and bonding failure process into a simple numerical analysis model, and thus realizes the analysis of the bonding performance and the failure process of the corroded steel bar concrete.

Description

Technical fields:

[0001] This invention relates to a numerical simulation analysis method based on ABAQUS for the bond performance between corroded steel bars and concrete, belonging to the field of finite element numerical simulation analysis technology. Background technology:

[0002] The bond behavior between reinforcing steel and concrete has a significant impact on the mechanical properties of reinforced concrete structures. The bond strength between deformed reinforcing steel and concrete is mainly provided by the mechanical interlocking action of the transverse ribs and the concrete between the ribs. Reinforced concrete structures face the problem of steel corrosion during service, which affects the contact area between the transverse ribs and the concrete between the ribs, thus impacting their bond performance. Therefore, it is necessary to conduct research on the bond performance between corroded reinforcing steel and concrete. Experimental research is the main means of investigating the bond performance between corroded reinforcing steel and concrete; however, experimental methods have drawbacks such as long cycles and complex operations. Existing finite element numerical simulation methods, such as inserting cohesive bond elements between plain round reinforcing steel and concrete, rely on bond-slip constitutive relations obtained experimentally. Therefore, it is necessary to provide a new three-dimensional finite element numerical simulation method that can reflect the bond-slip relationship. Summary of the Invention:

[0003] The purpose of this invention is to provide a numerical simulation method for investigating the bond performance between unevenly corroded ribbed steel bars and concrete members. The specific technical solution is as follows:

[0004] Step 1: Establish components for building a finite element model of the unevenly corroded ribbed steel bars and concrete: In the bonded portion of the steel bars to the concrete, the steel bars are ribbed; in the unbonded portion, they are modeled as plain round steel bars. For the ribbed steel bars, considering uneven corrosion, the corrosion rates of the steel bars on the far and near sides of the concrete cover are first obtained separately, and then the ribbed steel bars on both sides are modeled separately. The height, width, longitudinal height, width, and spacing of the uncorroded transverse ribs can be found in the national standard GB1499.2-2018. The height, width, longitudinal height, width, and diameter of the corroded transverse ribs can be obtained through calculation formulas. A concrete model is established, and the fine internal threads of the concrete are obtained through Boolean operations with the ribbed steel bars.

[0005] Step 2: Assigning properties to steel reinforcement and concrete materials: Set steel reinforcement material parameters, including: steel density, elastic modulus, Poisson's ratio, and yield strength; Set concrete material parameters, including: concrete density, elastic modulus, Poisson's ratio, and plasticity; wherein, the plasticity parameter is selected from the concrete plastic damage model.

[0006] Step 3: Assemble components, used to assemble and combine the reinforcing steel components with the concrete components; assemble the reinforcing steel into the corresponding positions of the concrete components, including the complete engagement of the transverse ribs of the reinforcing steel with the internal threads of the concrete.

[0007] Step 4: Set up the analysis steps, select the program type for the analysis steps, and check the required plant output variables and process output variables: Set analysis step 1 (corrosion process), use the dynamic display algorithm, set the step size to 0.2s, semi-automatic mass scaling, and scaling factor 0.0001; Set analysis step 2 (loading process), use the dynamic display algorithm, set the step size to 150s, semi-automatic mass scaling, and scaling factor 0.0001; Check the required field output variables and process output variables.

[0008] Step 5: Contact settings, used to set the contact properties between component models: In the bonded area between the ribbed steel bar and the concrete, set "face-to-face contact", set "hard contact" for the normal phase, and set "penalty friction" for the tangential direction. The friction coefficient is calculated using a formula related to the corrosion rate. In the non-bonded area between the ribbed steel bar and the concrete, set "face-to-face contact", set "hard contact" for the normal phase, and set "no friction" for the tangential direction.

[0009] Step 6: Loads and boundary conditions, used to set the loads and boundary conditions of the model: Define a reference point at the loading end of the reinforcement and "couple" the top surface of the reinforcement at the loading end to the reference point; apply a displacement load in the z direction at the above reference point and set the loading rate to 0.1 mm / s; set boundary conditions in the xyz directions on the concrete model; set radial displacement at the contact surface between the reinforcement and the concrete inside the concrete.

[0010] Step 7: Mesh the model, select the appropriate mesh type, and assign mesh properties: Set tetrahedral mesh for the reinforcing bars, and use local seeding for the ribbed reinforcing bars bonded to the concrete; Set tetrahedral mesh for the concrete, and use local seeding for the parts bonded to the reinforcing bars; Set the tetrahedral mesh properties to linear elements.

[0011] Step 8: Submit the model to the software for execution;

[0012] Step 9: Post-processing to obtain the software processing results;

[0013] Preferably, the calculation formula for the corrosion rate of the far and near steel bars of the concrete cover in step 1 is as follows: by performing a three-dimensional scan of the steel bars in the bonded zone after the test, and dividing the steel bars in Geomagic Wrap software, the mass loss ratio of the far and near steel bars of the concrete cover under a certain corrosion rate is obtained, and an empirical formula for the corrosion rate of the far and near steel bars of the concrete cover under any corrosion rate is obtained by fitting.

[0014] Preferably, the calculation formulas for the height of the transverse ribs, the width of the transverse ribs, the height of the longitudinal ribs, the width of the longitudinal ribs, and the diameter of the reinforcing bars after corrosion in step 1 are as follows:

[0015]

[0016]

[0017]

[0018] In the formula: η is the corrosion rate; δ is the size reduction rate; R0 and R η These represent the radii before and after corrosion, respectively; Lx η Lx0 and Lx0 are the dimensions of each side of the ribs before and after corrosion, respectively.

[0019] Preferably, the process output variables in step 4 include: AE (pseudo-strain energy), IE (total energy beam), and KE (kinetic energy), and AE+KE cannot exceed 5% of IE.

[0020] Preferably, the formula for calculating the friction coefficient and corrosion rate in step 5 is as follows:

[0021] μ(x) = 0.37 - 0.26(xx) cr )

[0022] Where: μ is the friction coefficient; x is the depth of steel corrosion; x cr This refers to the corrosion depth of the reinforcing steel when concrete cracks due to rust expansion (critical corrosion depth). The formula for calculating the critical corrosion depth of reinforcing steel is:

[0023] x cr =0.012c / d + 0.00084f cuk +0.018

[0024] Where: c is the thickness of the protective layer; d is the initial diameter of the reinforcing bar; f cuk This refers to the concrete strength.

[0025] Preferably, the radial displacement in step 6 is calculated using a formula related to the corrosion rate:

[0026]

[0027] In the formula: u is the radial displacement of concrete; r is the radius of steel bar; ρ is the expansion rate of steel bar corrosion products, ρ = 3; δ0 is the thickness of the transition zone (VTZ) between steel bar and concrete, δ0 = 12.5 μm.

[0028] Compared with related technologies, the numerical simulation method for investigating the bond performance between corroded steel bars and concrete provided by this invention has the following advantages:

[0029] This invention employs a two-stage analysis of bond failure in corroded reinforced concrete. By combining model establishment, contact relationships, and boundary conditions with existing reference formulas, it cleverly simulates the bond between steel reinforcement and concrete, as well as the impact of uneven corrosion on the structure. This transforms the complex corrosion and bond failure processes into a simple numerical analysis model, thereby enabling the analysis of the bond performance and failure process of corroded reinforced concrete. Specifically, the results are as follows:

[0030] The bond performance between corroded steel bars and concrete is analyzed in two stages: the first stage is steel bar corrosion, and the second stage, based on the results of the first stage, applies load until bond failure occurs. This simplifies the multi-factor coupled physical process into two independent physical processes.

[0031] For the model of corroded reinforcing bars, considering the different corrosion conditions on the near and far sides of the concrete cover, the corroded reinforcing bars are divided into near-side and far-side sections of the concrete cover, and modeled separately. The corroded reinforcing bars are then 3D scanned, and the scanned 3D model is segmented in Geomagic Wrap software to obtain the volumes of the reinforcing bars near and far from the concrete cover, allowing for the calculation of the corrosion rate on each side. An empirical formula is obtained by fitting the ratio of the two sides' reinforcing bars to the overall corrosion rate, which can be used to calculate the ratio of the two sides' corrosion rates under any given corrosion rate, and thus calculate the dimensions of each part of the reinforcing bars under any given corrosion rate. This modeling method effectively considers the impact of uneven corrosion of the reinforcing bars on the structural member.

[0032] The model defines the contact relationship as "face-to-face contact" and sets the normal direction to "hard contact." This ensures that in the bond zone between the reinforcing steel and concrete, the steel cannot penetrate the concrete surface, allowing the normal pressure to be infinite. Since the reinforcing steel in the bond zone is ribbed, the interlocking action between the ribs and the concrete between them is the primary source of bond force. Setting "hard contact" perfectly replicates this interlocking action. Setting "penalty friction" in the tangential direction also effectively replicates the friction between the steel and concrete contact surfaces.

[0033] A radial displacement is applied to the concrete surface at the reinforced concrete interface, with the magnitude of the displacement calculated using a known mathematical formula to simulate the corrosion and expansion process of the reinforcing steel. In practice, the impact of steel corrosion on concrete is mainly due to the expansion of corrosion products, which causes cracking and affects bond performance. Therefore, this method effectively accounts for the concrete cracking process caused by steel corrosion.

[0034] By refining the model of unevenly corroded ribbed steel bars, adding the rust expansion displacement at the steel bar-concrete interface, and conducting a two-stage analysis of the bond failure process between corroded steel bars and concrete, numerical simulation of the rust expansion cracking and bond failure process of unevenly corroded steel bars and concrete was achieved. This simplifies the actual steel bar corrosion and bond failure process into a highly operable numerical analysis process, allowing for intuitive analysis of the rust expansion cracking and bond failure processes of the structure, including the internal steel bar stress and bond-slip behavior. It can be effectively used for the analysis and evaluation of the bond performance between corroded steel bars and concrete. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the dimensions and reinforcement of the beam in the simulated test of this invention.

[0036] Figure 2 This is a schematic diagram of the steel bar segmentation in the Geomagic Wrap software in this invention.

[0037] Figure 3 This is a fitting graph showing the ratio of mass loss rate of the near and far reinforcing bars in the protective layer in this invention.

[0038] Figure 4 This is a schematic diagram of the cross-sectional dimensions of the transverse and longitudinal ribs in this invention.

[0039] Figure 5 This is a schematic diagram of the internal threads of the concrete in the bonding zone and the ribbed steel bars in the bonding zone in this invention.

[0040] Figure 6 This is a schematic diagram comparing the failure modes of the beam model in this invention with the experimental results.

[0041] Figure 7 This is a schematic diagram comparing the bond-slip curve with the experimental results in this invention. Detailed Implementation

[0042] The present invention will be further illustrated below with reference to examples, but it should not be construed as the present invention being limited to the examples described below.

[0043] The following will be based on the corrosion-resistant reinforced concrete beam specimens from the research group's previous experiments (reinforcement details and dimensions are attached). Figure 1 The model was established, and the results of the model were compared with the experimental results to prove the correctness of the model.

[0044] Step 1: Build the component for creating a finite element model of the unevenly corroded ribbed steel bar and concrete: In the bonded portion of the steel bar to the concrete, the steel bar is ribbed; in the unbonded portion, it is modeled as a plain round steel bar. The ribbed steel bar is designed to withstand uneven corrosion. This is achieved through 3D scanning of the bonded area steel bar after testing, and the steel bar is segmented in Geomagic Wrap software (see attached). Figure 2This yields the mass loss ratio of the reinforcing bars on the far and near sides of the concrete cover at a certain corrosion rate, and empirical formulas for the corrosion rates of the reinforcing bars on the far and near sides of the concrete cover at any corrosion rate are obtained through fitting (see appendix). Figure 3 The height, width, length, and spacing of the uncorroded transverse ribs can be found in the national standard GB 1499.2-2018 (see appendix for the cross-sectional dimensions of the transverse and longitudinal ribs). Figure 4 The height and width of the transverse ribs, the height and width of the longitudinal ribs, and the diameter of the reinforcing bars after corrosion can be obtained through calculation formulas. Then, the ribbed reinforcing bars on both sides are modeled separately. A concrete model is created, and the fine internal threads of the concrete are obtained through Boolean operations with the ribbed reinforcing bars (see attached). Figure 5 ).

[0045] The formulas for calculating the height and width of the transverse ribs, the height and width of the longitudinal ribs, and the diameter of the reinforcing bars after corrosion are as follows:

[0046]

[0047]

[0048]

[0049] In the formula: δ is the size reduction rate; R0 and R η These represent the radii before and after corrosion, respectively; Lx η Lx0 and Lx0 are the dimensions of each side of the ribs before and after corrosion, respectively.

[0050] Step 2: Assigning properties, used to assign properties to steel reinforcement and concrete materials: Set steel reinforcement material parameters, including: steel density, elastic modulus, Poisson's ratio, and yield strength; Set concrete material parameters, including: concrete density, elastic modulus, Poisson's ratio, and plastic damage plasticity.

[0051] Step 3: Assemble components, used to assemble and combine the reinforcing steel components with the concrete components; assemble the reinforcing steel into the corresponding positions of the concrete components, including the complete engagement of the transverse ribs of the reinforcing steel with the internal threads of the concrete.

[0052] Step 4: Set up the analysis step, select the program type for the analysis step, and check the required plant output variables and history output variables: Set up analysis step 1 (corrosion process), use the dynamic display algorithm, set the step size to 0.2s, semi-automatic mass scaling, and scaling factor 0.0001; Set up analysis step 2 (loading process), use the dynamic display algorithm, set the step size to 150s, semi-automatic mass scaling, and scaling factor 0.0001; Check the required field output variables S (stress), U (displacement), DAMAGE (damage) and history output variables AE (pseudo-strain energy), IE (total energy beam), and KE (kinetic energy).

[0053] Step 5: Contact Settings, used to set the contact properties between component models: In the bonded area between the ribbed steel bar and concrete, set "Surface-to-Surface Contact," "Hard Contact" for the normal phase, and "Penalty Friction" for the tangential direction. The friction coefficient is calculated using a formula related to the corrosion rate. In the non-bonded area between the ribbed steel bar and concrete, set "Surface-to-Surface Contact," "Hard Contact" for the normal phase, and "No Friction" for the tangential direction. The formula related to the corrosion rate for calculating the friction coefficient is as follows:

[0054] μ(x) = 0.37 - 0.26(xx) cr )

[0055] Where: μ is the friction coefficient; x is the depth of steel corrosion; x cr The critical corrosion depth of steel bars is the depth of corrosion of the steel bars when the concrete expands and cracks. The formula for calculating the critical corrosion depth of steel bars is

[27] :

[0056] x cr =0.012c / d + 0.00084f cuk +0.018

[0057] Where: c is the thickness of the protective layer; d is the initial diameter of the reinforcing bar; f cuk This refers to the concrete strength.

[0058] Step 6: Load and Boundary Conditions, used to set the loads and boundary conditions for the model: Define a reference point at the loading end of the reinforcement and "couple" the top surface of the reinforcement at the loading end to the reference point; apply a displacement load in the z-direction at the reference point and set the loading rate to 0.1 mm / s; set boundary conditions in the xyz directions on the concrete model; inside the concrete, set radial displacement at the contact surface between the reinforcement and the concrete. The radial displacement is calculated using a formula related to the corrosion rate:

[0059]

[0060] In the formula: u is the radial displacement of concrete; r is the radius of steel bar; ρ is the expansion rate of steel bar corrosion products, ρ = 3; δ0 is the thickness of the transition zone (VTZ) between steel bar and concrete, δ0 = 12.5 μm.

[0061] Step 7: Mesh the model, select the appropriate mesh type, and assign mesh properties: Set tetrahedral mesh for the reinforcing bars, and use local seeding for the ribbed reinforcing bars bonded to the concrete; Set tetrahedral mesh for the concrete, and use local seeding for the parts bonded to the reinforcing bars; Set the tetrahedral mesh properties to linear elements.

[0062] Step 8: Submit the model to the software for execution;

[0063] Step 9: Post-processing to obtain software processing results: Obtain the failure modes of the beam model (see appendix). Figure 6 ) and bond-slip curves (attached) Figure 7 The results showed good agreement with the experimental results.

Claims

1. A numerical simulation method for investigating the bond performance between non-uniformly corroded ribbed steel bars and concrete members, characterized in that: Step 1: Build components for creating a finite element model of unevenly corroded ribbed steel bars and concrete: In the bonded portion of the steel bars to the concrete, the steel bars are ribbed; in the unbonded portion, they are modeled as plain round steel bars. For the ribbed steel bars, considering uneven corrosion, the corrosion rates of the steel bars on the far and near sides of the concrete cover are first obtained, and then the ribbed steel bars on both sides are modeled separately. The height and width of the transverse ribs, the height and width of the longitudinal ribs, and the diameter of the steel bars after corrosion are obtained through calculation formulas. A concrete model is built, and the fine internal threads of the concrete are obtained through Boolean operations with the ribbed steel bars. Step 2: Assigning properties to steel reinforcement and concrete materials: Set steel reinforcement material parameters, including: steel density, elastic modulus, Poisson's ratio, and yield strength; Set concrete material parameters, including: concrete density, elastic modulus, Poisson's ratio, and plasticity; wherein, the plasticity parameter is selected from the concrete plastic damage model. Step 3: Assemble components, used to assemble and combine the reinforcing steel components with the concrete components; assemble the reinforcing steel into the corresponding positions of the concrete components, including the complete engagement of the transverse ribs of the reinforcing steel with the internal threads of the concrete; Step 4: Set up the analysis steps, select the program type for the analysis steps, and check the required plant output variables and history output variables: Set analysis step 1, i.e., the corrosion process, to use the dynamic display algorithm, with a step size of 0.2s, semi-automatic mass scaling, and a scaling factor of 0.0001; Set analysis step 2, i.e., the loading process, to use the dynamic display algorithm, with a step size of 150s, semi-automatic mass scaling, and a scaling factor of 0.0001; Check the required field output variables and history output variables. Step 5: Contact settings, used to set the contact properties between component models: In the bonded area between the ribbed steel bar and the concrete, set "face-to-face contact", set "hard contact" for the normal phase, and set "penalty friction" for the tangential direction. The friction coefficient is calculated using a formula related to the corrosion rate. In the non-bonded area between the ribbed steel bar and the concrete, set "face-to-face contact", set "hard contact" for the normal phase, and set "no friction" for the tangential direction. Step 6: Loads and boundary conditions, used to set the loads and boundary conditions of the model: Define a reference point at the loading end of the reinforcement and "couple" the top surface of the reinforcement at the loading end to the reference point; apply a displacement load in the z direction at the above reference point and set the loading rate to 0.1 mm / s; set boundary conditions in the xyz directions on the concrete model; set radial displacement at the contact surface between the reinforcement and the concrete inside the concrete. Step 7: Mesh the model and assign mesh properties: Set tetrahedral meshes for the reinforcing bars, and use local seeding for the ribbed reinforcing bars bonded to the concrete; Set tetrahedral meshes for the concrete, and use local seeding for the parts bonded to the reinforcing bars; Set the tetrahedral mesh properties to linear elements. Step 8: Submit the model to the software for execution; Step 9: Obtain the software processing results.

2. The method according to claim 1, characterized in that: The calculation formulas for the corrosion rates of the far and near steel bars in the concrete cover in step 1 are as follows: the steel bars in the bonded zone after the test are scanned in three dimensions, and the steel bars are divided in Geomagic Wrap software to obtain the mass loss ratio of the far and near steel bars in the concrete cover under a certain corrosion rate. Then, empirical formulas for the corrosion rates of the far and near steel bars in the concrete cover under any corrosion rate are obtained by fitting.

3. The method according to claim 1, characterized in that: The calculation formulas for the height and width of the transverse ribs, the height and width of the longitudinal ribs, and the diameter of the reinforcing bars after corrosion in step 1 are as follows: ； ； ； In the formula: Corrosion rate; This refers to the size reduction rate; and These are the radii before and after corrosion, respectively; and These are the dimensions of each side of the ribs before and after corrosion.

4. The method according to claim 1, characterized in that: The process output variables in step 4 include: AE (pseudo-strain energy), IE (total energy), and KE (kinetic energy), and AE+KE cannot exceed 5% of IE.

5. The method according to claim 1, characterized in that: The formula for calculating the friction coefficient and corrosion rate in step 5 is as follows: ； In the formula: x is the coefficient of friction; x is the depth of steel corrosion; x cr The critical corrosion depth is the depth of steel reinforcement that causes concrete to rust and crack. The formula for calculating the critical corrosion depth of steel reinforcement is: ； In the formula: c is the thickness of the protective layer; d is the initial diameter of the reinforcing bar; This refers to the concrete strength.

6. The method according to claim 1, characterized in that: The radial displacement in step 6 is calculated using a formula related to the corrosion rate: ； Where: u is the radial displacement of the concrete; The expansion rate of steel corrosion products. =3; Corrosion rate; The thickness of the transition zone between the steel reinforcement and the concrete. =12.5μm.

Images