Method for evaluating compression-bending bearing performance of asymmetric corroded RC column

Abstract

The application discloses a kind of asymmetric corrosion RC column compression-bending bearing capacity evaluation method, comprising: determining the corrosion rate of each steel bar in the section of corrosion RC column;Combining corrosion rate and the direction of seismic action, the asymmetric corrosion rate of tensile side steel bar and compression side steel bar in the section of corrosion RC column is determined;Based on asymmetric corrosion rate and the performance parameter of steel bar, the mechanical property degradation model of tensile side corrosion steel bar, compression side corrosion steel bar and protective layer concrete is determined;Combined with the direction of seismic action, based on asymmetric corrosion rate and mechanical property degradation model, the equilibrium equation of control section is established;By iterative solution of equilibrium equation, the bending bearing capacity of corrosion RC column under different axial force N u M u , further obtain the correlation curve of corrosion RC column N u - M u And the compression-bending bearing capacity envelope surface of corrosion RC column;Based on compression-bending bearing capacity envelope surface, the compression-bending bearing capacity of corrosion RC column is evaluated.The application can accurately evaluate the residual bearing capacity of non-uniform corrosion RC column.​

Description

Technical Field

[0001] This invention belongs to the technical field of structural safety assessment and durability evaluation in civil engineering, specifically relating to a method for assessing the bending and compression bearing capacity of asymmetric corroded RC columns. Background Technology

[0002] In corrosive environments such as coastal areas, de-icing salt fields, or industrial pollution, the problem of steel corrosion in reinforced concrete structures is particularly prominent. Corrosion not only leads to the loss of steel cross-section and degradation of mechanical properties, but also causes the concrete cover to crack and peel off, and severely weakens the bond between the steel and concrete. This significantly reduces the load-bearing capacity, deformation capacity, and ductility of the structure (especially columns, which are the main load-bearing components), threatening the seismic safety of the structure.

[0003] In existing technologies, the assessment of the bearing capacity of corroded reinforced concrete columns is mostly based on the assumption of "average corrosion rate," which treats all longitudinal reinforcement as uniformly corroded. However, in actual engineering, due to the spatial differences in environmental exposure conditions, such as differences between indoor and outdoor environments and unilateral contact with corrosive media, the corrosion of reinforcement often exhibits a significant asymmetrical distribution, that is, the degree of corrosion of reinforcement on one side of the member (such as the tension side) is much higher than that on the other side (such as the compression side).

[0004] Numerous studies have shown that the mechanisms and degrees of degradation affecting the mechanical properties of structural members differ significantly between corrosion of tensile and compressive reinforcing bars.

[0005] 1. Corrosion on the tension side mainly leads to a reduction in the cross-sectional area of ​​the reinforcing steel and a sharp drop in ductility (making it prone to brittle fracture), thereby significantly reducing the deformation capacity and energy dissipation capacity of the component.

[0006] 2. Corrosion on the compression side is more prone to buckling under compression due to the weakening of the steel reinforcement cross section and the unevenness of the surface. At the same time, rust expansion and cracking lead to the peeling of the concrete cover, reducing the effective cross section and weakening the ultimate bearing capacity of the component more directly and severely.

[0007] Traditional uniform corrosion assessment models neglect this asymmetry and its different mechanical failure modes, leading to significant deviations in the prediction of the actual load-bearing capacity of components. This may overestimate the structural safety margin or result in unnecessary waste of reinforcement materials. Furthermore, as axial pressure increases, the compression-bending failure mode of RC columns may gradually shift from large eccentric compression failure to small eccentric compression failure, altering the effects of corrosion on tensile and compressive reinforcement. Simultaneously, due to the randomness of seismic loading, the tensile and compressive reinforcement in RC columns changes with different seismic input directions, causing the compression-bending capacity of corroded RC columns to vary with the loading direction. Therefore, using only a single moment-axial force correlation curve will not accurately reflect the impact of asymmetric corrosion on the load-bearing capacity of RC columns under different loading directions. Summary of the Invention

[0008] The purpose of this invention is to overcome the limitations of the prior art and provide a method for evaluating the bending load-bearing capacity of asymmetric corroded RC columns, so as to improve the above-mentioned problems.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for evaluating the bending load-bearing capacity of an asymmetric corroded RC column includes the following steps: S1. Determine the corrosion rate of each steel bar in the cross section of the corroded RC column to be evaluated; S2. Based on the corrosion rate and the direction of the seismic action, determine the first average corrosion rate η of the steel reinforcement on the tension side within the corroded RC column section. t The second average corrosion rate η of the steel bars corroded on the compression side c ; S3, based on the first average corrosion rate η t and the second average corrosion rate η c Based on the performance parameters of corroded and uncorroded steel bars, a mechanical property degradation model for corroded steel bars on the tension side, corroded steel bars on the compression side, and concrete cover was determined. S4. Based on the direction of the seismic action and the first average corrosion rate η t Second average corrosion rate η c And the aforementioned mechanical property degradation model, and establish the equilibrium equations for the control section; S5. By iteratively solving the equilibrium equations, the corrosion of the RC column under different axial forces is obtained. N u Flexural bearing capacity under M u Thus, the rusted RC column was obtained. N u - M u Correlation curve; S6. Change the direction of the seismic force and repeat steps S2-S5 to obtain different directions. N u - M u The correlation curve forms the envelope of the compressive-bending bearing capacity of the corroded RC column; S7, The bending capacity of the corroded RC column is evaluated based on the bending capacity envelope.

[0010] Preferably, in step S1, the corrosion rate of each reinforcing bar within the corroded RC column section is calculated using the following method: At predetermined intervals along the rust-expansion cracks of the corroded RC column, a measuring point is selected to measure the width of the rust-expansion crack at each measuring point. The average width of the rust-expansion crack at all measuring points is taken as the average rust-expansion crack width W.cr ; Based on the average rust expansion crack width W cr The corrosion rate η of each steel bar is calculated based on the concrete column's protective layer thickness c and the diameter d of the corroded steel bars; where, .

[0011] Preferably, for RC columns with rectangular cross-sections, the direction of the seismic action includes at least two orthogonal directions, and the seismic action in each direction includes both positive and negative directions.

[0012] Preferably, in step S2, the average corrosion rate of all longitudinal reinforcing bars on the tension side is taken as the first average corrosion rate η. t The average corrosion rate of all longitudinal steel bars on the compression side is taken as the second average corrosion rate η. c .

[0013] Preferably, the mechanical property degradation model of the steel reinforcement on the tension side adopts a three-segment constitutive model, the mechanical property degradation model of the steel reinforcement on the compression side adopts a segmented constitutive model that introduces buckling effect reduction, and the mechanical property degradation model of the protective concrete adopts a strength reduction model.

[0014] Preferably, the mechanical property degradation model for the steel reinforcement corroded on the tension side is as follows:

[0015] in, ,

[0016]

[0017]

[0018] In the formula, σ sc For the stress of the rusted steel bars on the tension side, E s The elastic modulus of uncorroded reinforcing steel. e sc For the strain of corroded steel bars f yc The yield strength of the corroded steel bar. E shc ε is the modulus of the hardened section of the corroded steel reinforcement. shc This represents the initial hardening strain of the corroded steel reinforcement. f y0 The yield strength of the uncorroded steel reinforcement. f uc The ultimate strength of the corroded steel reinforcement. f u0 The ultimate strength of the uncorroded steel reinforcement. e ycThe yield strain of the corroded steel reinforcement. e sh0 The initial hardening strain of the uncorroded steel reinforcement. e y0 The yield strain of the uncorroded steel reinforcement. or cr ε is the critical corrosion rate. suc This represents the ultimate tensile strain of the corroded steel reinforcement. e su0 This represents the ultimate tensile strain of the uncorroded steel reinforcement.

[0019] The mechanical property degradation model for steel bars corroded on the compression side is as follows:

[0020]

[0021] The mechanical property degradation model for concrete cover is as follows:

[0022] In the formula, σ sc ' represents the stress of the corroded reinforcing steel on the compression side, ε sc σ represents the strain of the corroded reinforcing steel on the compression side. tc This represents the elastic limit stress of the corroded reinforcing steel on the compression side. e sci 'and f sci 'This represents the strain and stress at a characteristic point in the middle of a corroded steel bar under compression.' f scy 'and e scy 'This represents the compressive yield stress and corresponding strain of the corroded steel reinforcement.' E sc f is the elastic modulus of corroded steel bars. sci The strain on the tensile skeleton curve of the corroded steel reinforcement is e sci ' stress, f c The axial compressive strength of undamaged concrete. e 1 represents the average tensile strain perpendicular to the crack direction. e c0 This represents the compressive strain at peak stress in concrete. K The coefficient related to the diameter and roughness of the reinforcing bar is taken as 0.1. This represents the axial compressive strength of the concrete used for the rust protection layer.

[0023] Preferably, in step S4, the equilibrium equations include static equilibrium equations and moment equilibrium equations:

[0024]

[0025] In the formula, N u For axial force, α 1 represents the coefficient of the equivalent rectangular stress diagram of concrete. e The distance is the point of application of the axial compressive force to the point of resultant force on the tensile reinforcement. f cc To the compressive strength of the protective layer concrete, b For the cross-sectional width, x This is the equivalent height of the compression zone. h For the cross-sectional height, h 0 represents the effective height of the cross-section. α s and α s 'These are the distances from the resultant force point of the rusted reinforcing bars on the tension side and the rusted reinforcing bars on the compression side to the edge of the cross-section, respectively. s sc1 , s sc2 , s sc The stresses are respectively the stresses of the rusted reinforcing bars on the tension side, the middle reinforcing bars, and the rusted reinforcing bars on the compression side. A sc1 , A sc2 , A sc ' represents the corresponding cross-sectional area of ​​the reinforcing steel. M u To control the flexural capacity of the cross section, e 0 represents the eccentricity of the axial compressive force relative to the center of the cross section. e a This is for the additional eccentricity.

[0026] Preferably, in step S5: The given axial force is calculated by iteratively solving the equilibrium equations. N u The relationship curve between bending moment and curvature φ at the lower section is obtained until the section reaches the limit state, thus obtaining the corrosion RC column under a given axial force. N u Flexural bearing capacity under M u ; Calculate different axial forces N u Flexural bearing capacity under M u To obtain the rusted RC column N u - Mu Correlation curve.

[0027] Preferably, in step S7, the bending capacity envelope is compared with the design load effect. If the bending capacity is greater than the design load effect, the component is deemed safe; otherwise, reinforcement measures are required.

[0028] This invention can precisely consider the asymmetric distribution of steel reinforcement corrosion within the cross-section, distinguish different corrosion conditions on the tension and compression sides, and introduce separate mechanical property degradation models for the tension and compression sides of the steel reinforcement. By reasonably evaluating the corrosion rate and applying the corresponding corrosion damage model, a more accurate and safer assessment of the bending capacity of corroded reinforced concrete (RC) columns can be achieved. Compared with existing technologies, this invention has the following significant advantages: (1) For the first time, the corrosion rate of steel bars on the tension side and the compression side and the differential influence of mechanical property degradation model were distinguished in the bearing capacity assessment, which more realistically reflects the mechanical failure mechanism of non-uniform corrosion RC columns.

[0029] (2) It avoids the risk of overestimating the bearing capacity of the “average corrosion rate” model and has significant economic benefits.

[0030] (3) All parameters can be obtained through routine testing. The steps are clear and easy for engineering technicians to use.

[0031] (4) Taking into account the randomness of ground motion, the envelope of the RC column bending bearing capacity corresponding to different loading directions is obtained, which can comprehensively consider the bending performance of corroded RC columns in different directions and is convenient for the bearing capacity assessment of RC columns. Attached Figure Description

[0032] Figure 1 This is a flowchart illustrating the implementation of the method for evaluating the bending load-bearing capacity of asymmetric corroded RC columns according to the first embodiment of the present invention. Figure 2 A schematic diagram of the mechanical property degradation model of steel bars corroded on the tension side; Figure 3 A schematic diagram of the mechanical property degradation model of steel bars corroded on the compression side; Figure 4 A schematic diagram illustrating the principle of constructing equilibrium equations; where (a) represents the stress analysis of the RC column; (b) represents the strain distribution of the control section; and (c) represents the stress distribution of the control section. Figure 5 This is a schematic diagram showing the direction of earthquake action. Figure 6 This is a schematic diagram of the compression-bending capacity envelope of a corroded RC column. Detailed Implementation

[0033] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0034] Please see Figure 1 to Figure 3 This invention provides a method for evaluating the bending load-bearing capacity of an asymmetric corroded RC column, which includes the following steps S1 to S7.

[0035] S1. Determine the corrosion rate of each steel bar in the cross section of the corroded RC column to be evaluated.

[0036] In this embodiment, the corrosion rate of each steel bar in the cross section of the RC column to be evaluated can be determined by combining on-site testing with empirical models.

[0037] Specifically, due to the volume expansion caused by steel reinforcement corrosion, rust-induced expansion cracks appear in the concrete cover along the direction of the steel reinforcement. The width of these expansion cracks is clearly correlated with the degree of steel reinforcement corrosion. Therefore, the corrosion rate of the steel reinforcement can be estimated by measuring the width of the expansion cracks on the surface of the concrete column.

[0038] Specifically, at predetermined intervals (e.g., 200 mm) along the rust-expansion crack, a measuring point is taken, and the width of the rust-expansion crack at each measuring point is measured. The average value of all the measurement results is taken as the average rust-expansion crack width W. cr (Unit: mm), the corrosion rate of the reinforcing steel can be calculated using the following empirical formula:

[0039] In the formula, η is the corrosion rate of the corroded steel bar, c is the thickness of the concrete column's protective layer, and d is the diameter of the corroded steel bar.

[0040] It should be noted that the number of measuring points and the spacing between them can be adjusted according to the actual detection conditions, and are not limited to the values ​​mentioned above. This invention will not elaborate on these points here.

[0041] S2. Based on the corrosion rate and the direction of the seismic action, determine the first average corrosion rate η of the steel reinforcement on the tension side within the corroded RC column section. t The second average corrosion rate η of the steel bars corroded on the compression side c .

[0042] In this embodiment, the tension side and compression side of the RC column section under horizontal load in the direction of the seismic action can be determined based on the direction of the seismic action.

[0043] In this embodiment, the x-direction (or y-direction) of the RC column section is taken as the direction of seismic action. When a horizontal load acts along this direction, one side of the RC column section is under tension (called the tension side), and the other side is under compression (called the compression side). The specific locations of the tension side and the compression side change with the direction of the load.

[0044] For a given loading direction, the average corrosion rate of all longitudinal reinforcement bars on the tension side is taken as the first average corrosion rate η on the tension side. t The average corrosion rate of all longitudinal steel bars on the compression side is taken as the second average corrosion rate η of the compression side. c When the longitudinal reinforcement bars on one side have different degrees of corrosion, the arithmetic mean is used as the average corrosion rate of that side.

[0045] S3. Based on the first average corrosion rate η t and the second average corrosion rate η c By combining the performance parameters of corroded and uncorroded reinforcing bars, a mechanical property degradation model for corroded reinforcing bars on the tension side, corroded reinforcing bars on the compression side, and concrete cover was determined.

[0046] In this embodiment, the mechanical property degradation model of the steel reinforcement on the tension side adopts a three-segment constitutive model, the mechanical property degradation model of the steel reinforcement on the compression side adopts a segmented constitutive model that introduces buckling effect reduction, and the mechanical property degradation model of the protective concrete adopts a strength reduction model.

[0047] Specifically, such as Figure 2 As shown, the mechanical property degradation model of the steel reinforcement on the tension side is as follows:

[0048] in, ,

[0049]

[0050]

[0051] In the formula, σ sc For the stress of the rusted steel bars on the tension side, E s The elastic modulus of uncorroded reinforcing steel. e sc For the strain of corroded steel bars f yc The yield strength of the corroded steel bar. E shc ε is the modulus of the hardened section of the corroded steel reinforcement. shc This represents the initial hardening strain of the corroded steel reinforcement. f y0 The yield strength of the uncorroded steel reinforcement. f uc The ultimate strength of the corroded steel reinforcement. f u0 The ultimate strength of the uncorroded steel reinforcement. e yc The yield strain of the corroded steel reinforcement. e sh0 The initial hardening strain of the uncorroded steel reinforcement. e y0 The yield strain of the uncorroded steel reinforcement. or cr ε is the critical corrosion rate. suc This represents the ultimate tensile strain of the corroded steel reinforcement. e su0 This represents the ultimate tensile strain of the uncorroded steel reinforcement.

[0052] like Figure 3 As shown, the mechanical property degradation model of the corroded steel bars on the compression side is as follows:

[0053]

[0054] The mechanical property degradation model for concrete cover is as follows:

[0055] In the formula, σ sc ' represents the stress of the corroded reinforcing steel on the compression side, ε sc σ represents the strain of the corroded reinforcing steel on the compression side. tc This represents the elastic limit stress of the corroded reinforcing steel on the compression side. e sci 'and f sci 'This represents the strain and stress at a characteristic point in the middle of a corroded steel bar under compression.' f scy 'and e scy 'This represents the compressive yield stress and corresponding strain of the corroded steel reinforcement.' E sc f is the elastic modulus of corroded steel bars. sci The strain on the tensile skeleton curve of the corroded steel reinforcement is e sci ' stress, f c The axial compressive strength of undamaged concrete. e 1 represents the average tensile strain perpendicular to the crack direction. e c0 This represents the compressive strain at peak stress in concrete. K The coefficient related to the diameter and roughness of the reinforcing bar is taken as 0.1. This represents the axial compressive strength of the concrete used for the rust protection layer.

[0056] In this embodiment, the limiting state is determined by the first of the following three conditions: the compressive strain of the concrete in the compression zone reaches the limiting value ε. cu(Usually taken as 0.0033); the rusted steel bars on the tension side reach the ultimate tensile strain; the rusted steel bars on the compression side reach the critical buckling strain.

[0057] S4. Based on the direction of the seismic action and the first average corrosion rate η t Second average corrosion rate η c And the aforementioned mechanical property degradation model, and establish the equilibrium equations for the control section.

[0058] S5. By iteratively solving the equilibrium equations, the corrosion of the RC column under different axial forces is obtained. N u Flexural bearing capacity under M u Thus, the rusted RC column was obtained. N u - M u Correlation curve.

[0059] In this embodiment, since the bond degradation between the steel reinforcement and concrete caused by corrosion has a relatively small impact on the cross-sectional strain distribution, the plane section assumption can still be used when the end anchorage of the member is reliable, i.e., the cross-sectional strain is linearly distributed along the height. Figure 4 As shown.

[0060] At this point, the equilibrium equations for the controlling section include the static equilibrium equations and the moment equilibrium equations for the section, which are as follows:

[0061]

[0062] In this embodiment, the given axial force is calculated by iteratively solving the above-mentioned cross-sectional equilibrium equations. N u Bending moment at lower section M u The curve showing the relationship between curvature φ and the cross section is shown until the cross section reaches its limit state.

[0063] Specifically, the height x of the equivalent rectangular stress diagram of the compression zone is used as the independent variable, ranging from 10 mm to... h The solution is divided into 3000 equal parts for iterative solving. The strains of concrete and reinforcement are determined based on the plane section assumption, and then the material constitutive parameters are input: the core concrete uses a non-degraded constitutive model, while the protective layer concrete, tension-side corroded reinforcement, and compression-side corroded reinforcement use the performance degradation models determined in step S3. The stresses of the core concrete, protective layer concrete, tension reinforcement, and compression reinforcement are then substituted into two equilibrium equations for solving. The iterative convergence condition is satisfied when the error between the calculated axial force and the input axial compressive force is sufficiently small.

[0064] Apply a constant vertical axial force Nu (corresponding to axial compression ratio) n In this embodiment, the axial compression ratio n Determined according to the definition in the national standard "Standard for Design of Concrete Structures" (GB / T50010-2010).

[0065] Extract the ultimate bending moment M from the bending moment-curvature relationship. u This refers to the cross-sectional bending bearing capacity considering asymmetric corrosion under this axial compression ratio.

[0066] In this embodiment, by changing the axial force N u Obtain the flexural bearing capacity M under different axial forces u N can then be plotted. u -M u Correlation curves. Among them, the estimated axis N of the RC column. u (Calculated according to the national standard "Standard for Design of Concrete Structures" (GB / T50010-2010)), starting from 0 and gradually increasing in 20kN intervals, repeat steps S4-S5 for each axial force to obtain the flexural bearing capacity M corresponding to each axial force. u Based on this, draw the N of the RC column. u -M u Correlation curve.

[0067] S6. Change the direction of the seismic force and repeat steps S2-S5 to obtain different directions. N u - M u The correlation curve forms the envelope of the compressive-bending bearing capacity of the corroded RC column.

[0068] In this embodiment, specifically, as Figure 5 As shown, the earthquake direction includes at least two orthogonal directions (e.g., along the x and y directions of the column section), and both positive and negative loading are considered in each direction. The corrosion rate (i.e., η) of the corresponding tension-side and compression-side corroded reinforcing bars is determined according to each loading direction. t and η c Repeat steps S2-S5 to obtain the direction. N u -M u Correlation curves. Plotting the curves in all directions on the same coordinate system, the outer boundary of which represents the envelope of the compressive-bending capacity of the corroded RC column, as shown below. Figure 6 As shown.

[0069] S7. The bending capacity envelope of the corroded RC column is evaluated based on the bending capacity envelope.

[0070] In this embodiment, the design values ​​of bending moments in each direction of the RC column are compared with the compression-bending capacity envelope obtained in step S6. If the designed (axial force, bending moment) point is located inside the envelope, the component is deemed safe; if it is located outside the envelope, the component is deemed unsafe and reinforcement measures are required.

[0071] It should be noted that the evaluation results of this embodiment can serve as a scientific basis for durability diagnosis, seismic performance assessment, and repair and reinforcement decisions for existing reinforced concrete structures. The evaluation report should clearly record the corrosion rate obtained in each testing direction. or t and or c Key parameters include axial compression ratio n, load-bearing capacity assessment, and safety margin.

[0072] In summary, this embodiment can precisely consider the asymmetric distribution of steel reinforcement corrosion within the cross-section, distinguish between different corrosion conditions on the tension and compression sides, and introduce separate mechanical property degradation models for tension and compression reinforcement. By reasonably assessing the corrosion rate and applying the corresponding corrosion damage model, a more accurate and safe assessment of the bending capacity of corroded RC columns can be achieved.

[0073] Compared with the prior art, this embodiment has the following significant advantages: (1) For the first time, the corrosion rate of steel bars on the tension side and the compression side and the differential influence of mechanical property degradation model were distinguished in the bearing capacity assessment, which more realistically reflects the mechanical failure mechanism of non-uniform corrosion RC columns.

[0074] (2) It avoids the risk of overestimating the bearing capacity of the “average corrosion rate” model and has significant economic benefits.

[0075] (3) All parameters can be obtained through routine testing. The steps are clear and easy for engineering technicians to use.

[0076] (4) Taking into account the randomness of ground motion, the envelope of the RC column bending bearing capacity corresponding to different loading directions is obtained, which can be conveniently used for the bearing capacity assessment of RC columns.

[0077] It should be understood that the above are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. For those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for evaluating the compressive-bending bearing capacity of an asymmetric corroded RC column, characterized in that, Includes the following steps: S1. Determine the corrosion rate of each steel bar in the cross section of the corroded RC column to be evaluated; S2. Based on the corrosion rate and the direction of the seismic action, determine the first average corrosion rate η of the steel reinforcement on the tension side within the corroded RC column section. t The second average corrosion rate η of the steel bars corroded on the compression side c Among them, the average corrosion rate of all longitudinal steel bars on the tension side is taken as the first average corrosion rate η. t The average corrosion rate of all longitudinal steel bars on the compression side is taken as the second average corrosion rate η. c ; S3, based on the first average corrosion rate η t and the second average corrosion rate η c Based on the performance parameters of both corroded and uncorroded reinforcing bars, a mechanical property degradation model was determined for the corroded reinforcing bars on the tension side, the corroded reinforcing bars on the compression side, and the concrete cover. The mechanical property degradation model for the corroded reinforcing bars on the compression side adopted a piecewise constitutive model incorporating buckling effect reduction, with the following formula: In the formula, E s σ is the elastic modulus of uncorroded reinforcing steel. sc ' represents the stress of the corroded reinforcing steel on the compression side, ε sc σ represents the strain of the corroded reinforcing steel on the compression side. tc This represents the elastic limit stress of the corroded reinforcing steel on the compression side. ε sci 'and f sci 'This represents the strain and stress at a characteristic point in the middle of a corroded steel bar under compression.' f scy 'and ε scy 'This represents the compressive yield stress and corresponding strain of the corroded steel reinforcement.' E sc f is the elastic modulus of corroded steel bars. sci The strain on the tensile skeleton curve of the corroded steel reinforcement is ε sci ' stress, f y0 The yield strength of the uncorroded steel reinforcement; S4. Based on the direction of the seismic action and the first average corrosion rate η t Second average corrosion rate η c And the aforementioned mechanical property degradation model, and establish the equilibrium equations for the control section; S5. By iteratively solving the equilibrium equations, the corrosion of the RC column under different axial forces is obtained. N u Flexural bearing capacity under M u Thus, the rusted RC column was obtained. N u - M u Correlation curve; S6. Change the direction of the seismic force and repeat steps S2-S5 to obtain different directions. N u - M u The correlation curve forms the envelope of the compressive-bending bearing capacity of the corroded RC column; S7. The bending capacity envelope of the corroded RC column is evaluated based on the bending capacity envelope.

2. The method for evaluating the compressive-bending bearing capacity of asymmetric corroded RC columns according to claim 1, characterized in that, In step S1, the corrosion rate of each steel bar within the corroded RC column section is calculated using the following method: At predetermined intervals along the rust-expansion cracks of the corroded RC column, a measuring point is selected to measure the width of the rust-expansion crack at each measuring point. The average width of the rust-expansion crack at all measuring points is taken as the average rust-expansion crack width W. cr ; Based on the average rust expansion crack width W cr The corrosion rate η of each steel bar is calculated based on the concrete column's protective layer thickness c and the diameter d of the corroded steel bars; where, 。 3. The method for evaluating the compressive-bending bearing capacity of asymmetric corroded RC columns according to claim 1, characterized in that, For a rectangular cross-section RC column, the direction of the seismic action includes at least two orthogonal directions, and the seismic action in each direction includes both positive and negative directions.

4. The method for evaluating the compressive-bending bearing capacity of asymmetric corroded RC columns according to claim 1, characterized in that, The mechanical property degradation model of the steel reinforcement on the tension side is a three-segment constitutive model, and the mechanical property degradation model of the protective concrete is a strength reduction model.

5. The method for evaluating the compressive-bending bearing capacity of asymmetric corroded RC columns according to claim 4, characterized in that, The mechanical property degradation model for steel bars corroded on the tension side is as follows: in, , In the formula, σ sc For the stress of the rusted steel bars on the tension side, ε sc For the strain of corroded steel bars f yc The yield strength of the corroded steel bar. E shc ε is the modulus of the hardened section of the corroded steel reinforcement. shc The initial hardening strain of the corroded steel reinforcement. f uc The ultimate strength of the corroded steel reinforcement. f u0 The ultimate strength of the uncorroded steel reinforcement. ε yc The yield strain of the corroded steel reinforcement. ε sh0 The initial hardening strain of the uncorroded steel reinforcement. ε y0 The yield strain of the uncorroded steel reinforcement. η cr ε is the critical corrosion rate. suc This represents the ultimate tensile strain of the corroded steel reinforcement. ε su0 The ultimate tensile strain of the uncorroded steel reinforcement; The mechanical property degradation model for concrete cover is as follows: In the formula, f c The axial compressive strength of undamaged concrete. ε 1 represents the average tensile strain perpendicular to the crack direction. ε c0 This represents the compressive strain at peak stress in concrete. K A coefficient related to the diameter and roughness of the reinforcing bar. This represents the axial compressive strength of the concrete used for the rust protection layer.

6. The method for evaluating the compressive-bending bearing capacity of asymmetric corroded RC columns according to claim 5, characterized in that, In step S4, the equilibrium equations include static equilibrium equations and moment equilibrium equations: In the formula, N u For axial force, α 1 represents the coefficient of the equivalent rectangular stress diagram of concrete. e The distance is the point of application of the axial compressive force to the point of resultant force on the tensile reinforcement. f cc To the compressive strength of the protective layer concrete, b For the cross-sectional width, x This is the equivalent height of the compression zone. h For the cross-sectional height, h 0 represents the effective height of the cross-section. α s and α s 'These are the distances from the resultant force point of the rusted reinforcing bars on the tension side and the rusted reinforcing bars on the compression side to the edge of the cross-section, respectively. σ sc1 , σ sc2 , σ sc The stresses are respectively the stresses of the rusted reinforcing bars on the tension side, the middle reinforcing bars, and the rusted reinforcing bars on the compression side. A sc1 , A sc2 , A sc ' represents the corresponding cross-sectional area of ​​the reinforcing bar; M u To control the flexural capacity of the cross section, e 0 represents the eccentricity of the axial compressive force relative to the center of the cross section. e a This is for the additional eccentricity.

7. The method for evaluating the compressive-bending bearing capacity of asymmetric corroded RC columns according to claim 6, characterized in that, In step S5: The given axial force is calculated by iteratively solving the equilibrium equations. N u The relationship curve between bending moment and curvature φ at the lower section is obtained until the section reaches the limit state, thus obtaining the corrosion RC column under a given axial force. N u Flexural bearing capacity under M u ; Calculate different axial forces N u Flexural bearing capacity under M u To obtain the rusted RC column N u - M u Correlation curve.

8. The method for evaluating the compressive-bending bearing capacity of asymmetric corroded RC columns according to claim 1, characterized in that, In step S7, the bending capacity contained in the bending capacity envelope is compared with the design load effect. If the bending capacity is greater than the design load effect, the component is deemed safe; otherwise, reinforcement measures are taken.

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