Bridge structure safety performance evaluation method and system, and medium

Abstract

This invention relates to the field of bridge technology, specifically to a method, system, and medium for evaluating the safety performance of bridge structures. The method for evaluating the safety performance of bridge structures includes the following steps: obtaining the steel reinforcement strain non-uniformity coefficient and concrete cracking parameters; establishing a numerical model based on the steel reinforcement strain non-uniformity coefficient and the concrete cracking parameters; performing numerical simulation on the numerical model based on the single-factor method and fitting the model to obtain the correspondence between the steel reinforcement strain non-uniformity coefficient and the concrete cracking parameters; and evaluating the safety performance of the bridge structure based on the correspondence. This invention demonstrates the relationship between the stiffness of reinforced concrete members and the development of surface cracks, and proves that the steel reinforcement strain non-uniformity coefficient is a characterizing factor of the stiffness of concrete members. B The study also examines important physical parameters related to the degradation process of concrete bridges, demonstrating that information on apparent defects in concrete bridges can be used to assess their overall safety performance.

Description

Technical Field

[0001] This invention relates to the field of bridge technology, specifically to methods, systems, and media for evaluating the safety performance of bridge structures. Background Technology

[0002] Reinforced concrete is an anisotropic multi-component composite material. During construction, various substances with different properties are bonded together by cement. However, due to improper design, unreasonable construction, and the inherent non-homogeneity of the materials, reinforced concrete structures inevitably suffer from minor structural damage during construction. Once in service, under the combined effects of external loads, environmental erosion, natural disasters, and human factors, this structural damage may accelerate, ultimately leading to the common defects found in reinforced concrete structures.

[0003] From the perspective of the causes of defects, the defects of reinforced concrete bridges can be summarized into three main categories: concrete cracking, concrete corrosion, and steel corrosion. Among these, concrete cracking is the most common defect in reinforced concrete bridges, and it can be further divided into two main categories based on its causes: load-bearing cracks and non-load-bearing cracks. As a material with strong compressive strength but weak tensile strength, concrete is prone to cracking when under tension under external loads; the resulting cracks are called load-bearing cracks. Besides load-bearing cracks, other types of cracks on the surface of reinforced concrete bridges are non-load-bearing cracks. Based on their causes, non-load-bearing cracks can be further classified into concrete shrinkage cracks, alkali-aggregate reaction cracks, temperature cracks, and steel corrosion cracks, etc.

[0004] The stiffness degradation process of reinforced concrete beams can be divided into three stages: the overall working stage, the normal working stage, and the yield hardening stage. In the overall working stage, the material has not yet cracked, and the entire cross-section of the reinforced concrete beam participates in the load. The normal working stage is the process of material property changes from the appearance of cracks in the concrete to the yielding of the tensile reinforcement. Currently, for reinforced concrete structures in the normal working stage, relevant research mainly uses the stiffness analysis method to analyze the stiffness of flexural members under short-term loads. Analysis shows that the coefficient of non-uniformity of steel strain is closely related to the stiffness of the member and its degradation process.

[0005] However, existing technologies have not demonstrated a link between the stiffness of reinforced concrete components and the development of surface cracks, meaning there is no evidence that it is feasible to assess the overall safety performance of concrete bridges using information on apparent defects. Summary of the Invention

[0006] In view of this, the present invention provides a method, system, and medium for evaluating the safety performance of bridge structures, demonstrating the relationship between the stiffness of reinforced concrete members and the development of surface cracks, and proving the coefficient of non-uniformity of steel strain. It characterizes the stiffness of concrete members BThe study also examines important physical parameters related to the degradation process of concrete bridges, demonstrating that information on apparent defects in concrete bridges can be used to assess their overall safety performance.

[0007] In a first aspect, the present invention provides a method for evaluating the safety performance of bridge structures, comprising the following steps: Obtaining the coefficient of non-uniformity of steel reinforcement strain And concrete cracking parameters, based on the aforementioned steel reinforcement strain non-uniformity coefficient A numerical model was established based on the concrete cracking parameters; Based on the single-factor method, the numerical model is numerically simulated and fitted to obtain the strain non-uniformity coefficient of the reinforcing steel. The correspondence between the parameters and the concrete cracking parameters; The safety performance of the bridge structure is evaluated based on the aforementioned correspondence.

[0008] In one possible implementation, the strain non-uniformity coefficient of the reinforcing steel The expression is: In the formula, The cracking moment of the component, M This represents the bending moment experienced by the member under the current external load.

[0009] In one possible implementation, the concrete cracking parameters include the average crack height. and average crack spacing Based on the average height of the crack and average crack spacing Characterizes concrete cracks.

[0010] In one possible implementation, the numerical model is built based on ANSYS software, and uses SOLID65 elements to simulate concrete material and PIPE20 elements to simulate steel reinforcement. For the concrete material in the cracked zone, a distributed crack model was used for simulation, combined with the average crack height. and the average spacing of the cracks The reinforcing bars characterize the stress state of the concrete.

[0011] In one possible implementation, the fitting is performed using a quadratic polynomial regression model. The average height of the crack With respect to the average spacing of the crack The strain non-uniformity coefficient of the steel reinforcement, respectively Perform a quadratic polynomial regression model fitting.

[0012] In one possible implementation, the quadratic polynomial regression model is modified based on the least squares method to obtain a modified model, the expression of which is: In the formula, the average spacing of the cracks is... The unit is cm, and the average height of the crack is [missing information]. Relative cross-sectional height The coefficient of non-uniformity of steel reinforcement strain .

[0013] In one possible implementation, the verification of the correspondence is further included, which includes static load testing and visual inspection. The static load testing includes applying graded loads to the specimen, measuring the deflection at mid-span of the specimen under each load level using a displacement gauge and a dial indicator, and then calculating the test stiffness value of the specimen using the deflection-stiffness relationship. ; The visual inspection includes observing and recording the crack development of the specimen under various load levels, and then calculating the stiffness value of the specimen using the modified model and the cross-sectional bending stiffness expression of the reinforced concrete beam. ; Based on the above and stated The correspondence is verified.

[0014] In one possible implementation, the expression for the flexural stiffness of the reinforced concrete beam section is: In the formula, The effective height of the cross section, This is the coefficient of non-uniformity of the reinforcing steel strain. The elastic modulus of the steel reinforcement. For the area of ​​the reinforcing steel, This refers to the longitudinal tensile reinforcement ratio.

[0015] Secondly, the present invention provides a bridge structural safety performance evaluation system, comprising: The acquisition module is used to obtain the coefficient of uniformity of strain in steel bars. And concrete cracking parameters, based on the aforementioned steel reinforcement strain non-uniformity coefficient A numerical model was established based on the concrete cracking parameters; The fitting module is used to perform numerical simulation and fitting of the numerical model based on the single-factor method to obtain the strain non-uniformity coefficient of the reinforcing steel. The correspondence between the parameters and the concrete cracking parameters; The evaluation module is used to evaluate the safety performance of the bridge structure based on the aforementioned correspondence.

[0016] Thirdly, the present invention provides a computer-readable storage medium storing program instructions that, when executed, implement the bridge structure safety performance evaluation method as described above.

[0017] The present invention, employing the above-described solution, has at least the following beneficial effects: In this application, the relationship between the stiffness of reinforced concrete members and the development of surface cracks is demonstrated, and the coefficient of uniformity of strain in the reinforcing steel is also proven. It characterizes the stiffness of concrete members B The study also examines important physical parameters related to the degradation process of concrete bridges, demonstrating that information on apparent defects in concrete bridges can be used to assess their overall safety performance. Attached Figure Description

[0018] This application can be further illustrated by the non-limiting embodiments given in the accompanying drawings.

[0019] Figure 1 This is a flowchart of the bridge structure safety performance evaluation method in the embodiments of this application; Figure 2 This is a schematic diagram of the geometric dimensions and loads of the reinforced concrete beam in the embodiments of this application. The unit in the diagram is mm. Figure 3 This is a schematic diagram of the reinforcement details of the reinforced concrete beam in an embodiment of this application. The unit in the diagram is mm. Figure 4 This is a schematic diagram of the concrete model of beam L7.5-0.1 in the embodiments of this application; Figure 5 This is a schematic diagram of the reinforcement model of beam L7.5-0.1 in the embodiments of this application; Figure 6 This is a schematic diagram of the deformation of beam L7.5-0.1 under forced displacement in an embodiment of this application. The unit in the figure is mm. Figure 7 This is a schematic diagram of the cracking of beam L7.5-0.1 (semi-model) under forced displacement in an embodiment of this application; Figure 8 This refers to different crack spacings in the embodiments of this application. - Line graph; Figure 9 This is an embodiment of the present application. =7.5cm - Fitted curve; Figure 10 This refers to different crack initiation heights in the embodiments of this application. - Line graph; Figure 11 This is an embodiment of the present application. =0.2h - Fitted curve; Figure 12 This is an embodiment of the present application. and right Response surface plot; Figure 13 This is a side view of the test specimen in an embodiment of this application; the unit in the figure is mm. Figure 14 This is a cross-sectional view of the support of the test specimen in the embodiment of this application, and the unit in the figure is mm; Figure 15 This is a mid-span cross-sectional view of the test specimen in the embodiments of this application, with units in mm; Figure 16 This is a real-world image of the test specimen being loaded in an embodiment of this application; Figure 17 This is a block diagram of the system in the embodiments of this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] To demonstrate the close relationship between the stiffness of reinforced concrete members and the development of surface cracks, the inventors investigated the coefficient of uniformity of strain in the reinforcing steel. Stiffness of concrete components B The relationship between concrete cracking parameters was studied. It was found that in existing technologies, such as Chen Jue's "Research on the State Assessment Method of Steel-Concrete Simply Supported Beam Bridge Based on Crack Appearance Detection" [D]. Nanjing (Master's Thesis, Nanjing University of Aeronautics and Astronautics, 2009), it is pointed out that the nonlinear change region of reinforced concrete beams under compression is relatively small. Some theories suggest that compared to crack propagation, its effect on... The impact is much smaller and can be ignored.

[0022] However, in practice, the coefficient of uniformity of steel strain... Stiffness of concrete components BThere is a close relationship between the stiffness of reinforced concrete members and the cracking parameters. The inventors proved the connection between the stiffness of reinforced concrete members and the development of surface cracks by using the theory of cross-sectional stiffness of reinforced concrete members, the parameter characterization of structural stiffness degradation caused by concrete cracking, numerical model establishment and analysis, and proved the coefficient of non-uniformity of steel strain. It characterizes the stiffness of concrete members B The study also examines important physical parameters related to the degradation process of concrete bridges, demonstrating that information on apparent defects in concrete bridges can be used to assess their overall safety performance.

[0023] In view of this, firstly, such as Figure 1 As shown in the figure, this application proposes a method for evaluating the safety performance of bridge structures, including the following steps: S1. Obtain the coefficient of non-uniformity of steel strain. And concrete cracking parameters, based on the coefficient of uniformity of steel strain Establish a numerical model for concrete cracking parameters; S2. Based on the single-factor method, numerical simulation is performed on the numerical model, and then fitting is performed to obtain the coefficient of non-uniformity of steel strain. Correspondence between parameters and concrete cracking parameters; S3. Evaluate the safety performance of the bridge structure based on the corresponding relationship.

[0024] First, obtain the strain non-uniformity coefficient of the reinforcing steel. The corresponding calculation formula, combined with concrete cracking parameters, is used to establish a numerical model. Based on the single-factor method, numerical simulation is performed to obtain the coefficient of non-uniformity of steel reinforcement strain. The correspondence between the parameters and concrete cracking parameters is used to evaluate the condition of concrete components and the cracking situation. This allows for the assessment of the overall safety performance of concrete bridges based on their cracking conditions, meaning that the apparent defects of concrete bridges can be used to evaluate the overall safety performance of the bridges.

[0025] In one embodiment of the present invention, in step S1, the strain non-uniformity coefficient of the reinforcing steel is... The expression is: In the formula, The cracking moment of the component, M This represents the bending moment experienced by the member under the current external load. It is expressed by the coefficient of uniformity of strain in the reinforcing steel. From the expression, it can be seen that when the load borne by the member reaches the cracking load, the coefficient of non-uniformity of the reinforcing steel strain is... As the external load increases, the coefficient of non-uniformity of the steel reinforcement gradually increases from zero until it reaches a certain stable value, indicating that the coefficient of non-uniformity of the steel reinforcement strain is increasing. With component stiffness B It is closely related to its degradation process.

[0026] Specifically, the flexural stiffness of a section refers to the bending moment required to produce a unit curvature of the section, usually expressed as... B Indicates. According to the definition:

[0027] In the formula, M The bending moment experienced by the component. Let be the curvature of the component.

[0028] Understandably, the entire stiffness degradation process of a reinforced concrete beam can be divided into three stages: the overall working stage, the normal working stage, and the yield hardening stage. In the overall working stage, the material has not yet cracked, and the entire cross-section of the reinforced concrete beam participates in the work. At this time, The curve is approximately a straight line, and the structural bending stiffness can be calculated as that of an elastic material, expressed as: In the formula, For concrete elastic modulus, The moment of inertia of the beam section is... This is the equivalent moment of inertia for the uncracked section.

[0029] The normal working stage is the process of material property changes from the appearance of cracks in the concrete to the yielding of the tensile reinforcement. For ordinary reinforced concrete structures, this stage represents the normal working state of the structure. During this stage, the appearance of cracks causes changes in structural stiffness, making stiffness calculations more complex than during the overall working stage. Generally, we can disregard the effects of steel corrosion and consider the degradation of structural stiffness in this stage as an effect of crack development and plastic changes in the compression zone of the concrete. Therefore, once crack development and plastic changes in the compression zone stabilize, the beam stiffness also becomes relatively stable.

[0030] The yield hardening stage refers to the process from the yielding of the reinforcing steel to the complete failure of the structure. During this stage, the plasticity of the concrete in the compression zone is fully utilized, and the bending moment that the structure can withstand reaches its limit.

[0031] In the analytical method of stiffness, to analyze the stiffness of flexural members under short-term loads, the method makes the following assumptions: First, it simultaneously considers the participation of the concrete in the tension zone and the nonlinear effects of the concrete in the compression zone; second, it adopts the geometric relationships of elementary beam theory; third, it establishes equilibrium conditions at the section where cracks occur. Based on the above assumptions, the following expression can be obtained: In the formula, This is the internal lever arm coefficient. The effective height of the cross section, This is the coefficient of non-uniformity of the reinforcing steel strain. This is the coefficient of non-uniformity of concrete strain. The elastic modulus of the steel reinforcement. For the area of ​​the reinforcing steel, The fullness coefficient of the stress pattern. The parameters affecting the plastic deformation of concrete in the compression zone are as follows: This refers to the elastic modulus of concrete in the elastic stage. This represents the area of ​​the concrete in the compression zone. In practical applications, the coefficients in the above formula... , , It is difficult to determine, but through equivalent transformation, the following expression is obtained: In the formula, , , This refers to the longitudinal tensile reinforcement ratio. This is the height coefficient of the pressure zone.

[0032] Since the bending moment level of the component does not change significantly during its service life, crack development is relatively stable. It is also relatively stable, generally taking a value of 0.875. Furthermore, based on numerous experimental results: .

[0033] Therefore, the expression for the flexural stiffness of a reinforced concrete beam during normal operation can be further simplified to: .

[0034] Understandably, for a known structure, the parameters in the expression for the flexural stiffness of the cross section... , , , , They are all quantitative; they do not change with variations in the external loads applied to the structure. However, it is a variable related to the external loads borne by the structure. Therefore, the coefficient of uniformity of strain in the reinforcing steel is... It is closely related to the flexural stiffness of reinforced concrete beams and its degradation process.

[0035] Some studies have found that reinforced concrete beams under external loads undergo two types of physical changes during stiffness degradation: crack propagation and the development of plastic deformation in the compression zone. This indicates that crack propagation and the development of plastic deformation in the compression zone are also related to the stiffness of the member. B It is closely related to its degradation process. Therefore, the coefficient of non-uniformity of steel strain is... It is necessarily closely related to the development of cracks and the plastic deformation of concrete in the compression zone.

[0036] Understandable, the coefficient of uniformity of strain in steel reinforcement When characterizing the influence of tensile concrete between cracks on the strain of longitudinal tensile reinforcement, the structure will develop its first batch of cracks under the cracking moment. Due to the bond between the concrete and the reinforcement, the reinforcement and concrete in the uncracked area maintain a deformation coordination relationship, resulting in a much smaller strain in the reinforcement in the uncracked area compared to the reinforcement strain at the crack. The average strain of the reinforcement differs significantly from that at the crack. The value is relatively small. As the load increases, the tensile concrete between the cracks gradually ceases to function due to excessive deformation. At this point, the crack spacing continuously decreases, while large strains occur in the reinforcing steel in the originally uncracked areas. This causes the average strain of the reinforcing steel to gradually approach the strain of the reinforcing steel at the cracked areas. The value gradually increases. Furthermore, with the increase in load, the curvature of the beam also increases. Under the action of bending tensile stress on both sides, the stress at the crack tip also gradually increases. The concrete at the tip is continuously damaged and decomposition occurs, leading to an increase in the crack's propagation height. Therefore, crack propagation is related to... Values ​​are closely related; it is The main reason for the continuous change in values. The development of plastic deformation in concrete may also cause... Changes in value.

[0037] In one embodiment of the present invention, in step S1, the concrete cracking parameters include the average crack height. and average crack spacing Based on the average crack height and average crack spacing Characterizing concrete cracks. In this embodiment, because... The value can be used as a characterizing parameter for the stiffness degradation of reinforced concrete beams caused by concrete cracking. That is, by analyzing the influence of concrete cracking parameters (average crack propagation height and average crack spacing) on ​​the characterizing parameters of the stiffness of reinforced concrete beams, it is possible to further analyze its relationship with the coefficient of uniformity of steel strain. The relationship.

[0038] In one embodiment of the present invention, in step S2, the numerical model is established based on ANSYS software, and SOLID65 elements are used to simulate concrete material and PIPE20 elements are used to simulate steel bars. For the concrete material in the cracked zone, a distributed crack model is used for simulation, combined with the average crack height. and average crack spacing Reinforcing steel bars characterize the stress state of concrete.

[0039] Understandably, ANSYS is a mature commercial software; the distributed crack model adopts the distributed crack model from (Chen Jue. Research on the State Assessment Method of Steel-Concrete Simply Supported Beam Bridge Based on Crack Appearance Detection [D]. Nanjing: Master's Thesis of Nanjing University of Aeronautics and Astronautics, 2009.). The distributed crack model assumes that the cracked concrete still maintains some continuity and can be treated as an orthogonal anisotropic material. The advantage of this model is that the location of the crack can be controlled manually, but the disadvantage is that it cannot consider the crack width.

[0040] Furthermore, the crack control in the Highway Bridge and Culvert Maintenance Specification (JTG H11-2004) [S] is mainly achieved by controlling the crack width. As can be seen from the research on the condition assessment method of steel-concrete simply supported beam bridge based on crack appearance detection, this single-parameter control method is conservative. Existing technology (He Shuanhai, Song Yifan, Zhao Xiaoxing, Cui Jun. Experimental study on crack characteristics and damage assessment method of reinforced concrete beam structure [J]. Journal of Civil Engineering, 36(2): 6-9, 2003.) proposes a method to describe cracks using statistical parameters (i.e., average crack spacing, average development height, and average width). This method can not only reflect the overall stress of bending members well, but this application also uses statistical parameters to characterize cracks.

[0041] However, due to the use of a distributed crack model, this application can only simulate crack spacing and crack height, and cannot simulate crack width. Nevertheless, numerous studies have shown a close relationship between average crack width, average crack propagation height, and average crack spacing; average crack width is not an independent variable of the other two quantities. Therefore, using average crack height... and average crack spacing It can already describe the stress state of bending members very well.

[0042] In one embodiment of the present invention, in step S3, a quadratic polynomial regression model is used for fitting during the fitting process. Average crack height Average spacing of cracks Respectively related to the coefficient of non-uniformity of steel strain A quadratic polynomial regression model was used for fitting. By employing a quadratic polynomial regression model for single-factor fitting analysis, the nonlinear relationship between the single factor and the target variable can be described more flexibly, thus enabling a more accurate analysis of the non-uniformity coefficient of steel reinforcement strain. With average crack height and average crack spacing The relationship.

[0043] In one embodiment of the present invention, the quadratic polynomial regression model is modified based on the least squares method to obtain a modified model, the expression of which is: In the formula, the average spacing of the cracks is... The unit is cm, and the average height of the crack is [missing information]. Relative cross-sectional height The coefficient of non-uniformity of steel reinforcement strain By refining the model, a more reasonable and accurate fitting formula for estimating the true stiffness of cracked reinforced concrete beams can be obtained.

[0044] In one embodiment of the present invention, the bridge structure safety performance evaluation method further includes verifying the above-mentioned correspondence. Verification includes static load testing and visual inspection. The static load testing includes applying graded loads to the specimen, measuring the mid-span deflection of the specimen under each load level using a displacement gauge and a dial gauge, and then calculating the test stiffness value of the specimen using the deflection-stiffness relationship. .

[0045] The visual inspection includes observing and recording the crack development of the specimen under various load levels, and then calculating the stiffness value of the specimen using the modified model and the cross-sectional bending stiffness expression of the reinforced concrete beam. ; based on and The correspondence was verified. The above verification demonstrates that the expression of the modified model in this application is accurate and reliable.

[0046] The safety performance of bridge structures is evaluated through the following specific implementation methods; in the specific implementation methods, as follows: Figure 2-3 The following explanation uses a simply supported reinforced concrete beam as an example. This simply supported beam is equipped with tensile main bars, compressive bars, and stirrups. The geometric dimensions of this simply supported beam and the load it bears are determined by... Figure 2 As shown, the reinforcement details of this simply supported beam are as follows: Figure 3 The material properties of the simply supported beam are as follows: concrete elastic modulus E = 24000 MPa, Poisson's ratio... =0.2, uniaxial tensile strength =3MPa. At the crack location, the crack opening transmission factor is 0.4, and the crack closing transmission factor is 1. Concrete crushing is not considered. The reinforcing steel is considered a bilinear kinematic hardening material; the elastic modulus of the tensile steel is E = 2e5MPa, and the Poisson's ratio is... =0.3, yield stress is =350MPa, the elastic modulus of the compression steel bars and stirrups is E=2e5MPa, Poisson's ratio =0.25, yield stress is =200MPa.

[0047] Numerous experimental studies both domestically and internationally have shown that, throughout the entire process from cracking to failure, reinforced concrete beams... In [0.1 h 0.8 h ]( h The height varies within the range of the cross-section. The range of variation is [4cm, 50cm]. The crack parameters for concrete cracking used in this application are given in Table 1.

[0048] Table 1 Crack parameter values ​​and beam model numbers

[0049] Note: Average crack spacing in Table 1 The unit is cm, and the average height of the crack is [missing information]. This represents the relative cross-sectional height.

[0050] As shown in Table 1, this application established 48 reinforced concrete beam models with different crack parameters. The concrete element size in the crack zone of these models was 1 cm. To improve calculation speed and convergence, the concrete element size between cracks was approximately 7.5 cm. The concrete and reinforcing steel parts were respectively constructed by... Figure 4 and Figure 5 Given. By loading point P (see Figure 2 A forced vertical displacement of 5 mm was applied, and the static response of the L7.5-0.1 beam model was calculated. The calculation results are as follows: Figure 6 and Figure 7 Provided.

[0051] Depend on Figure 6 It can be seen that under forced displacement, the maximum vertical displacement of beam L7.5-0.1 occurs at mid-span, with a magnitude of 6.5 mm; Figure 7 It can be seen that under forced displacement, all the concrete in the crack zone of beam L7.5-0.1 cracked. These results are consistent with basic mechanical laws, proving that the beam model L7.5-0.1 established in this application is correct and reliable. Similar conclusions can be obtained by using the same method to verify the reliability of other models.

[0052] In one specific implementation, the cracking moment of the reinforced concrete beam M cr The following formula can be used to approximate the determination based on the plain concrete section: In the formula, This refers to the standard value of the axial tensile strength of concrete. The width of the cross section; This represents the cross-sectional height.

[0053] Regarding the application Figure 2 Utilizing cracking moment M crThe calculation formula is used to calculate... M cr =11.8125 kN·m, therefore, the cracking load to be applied at loading point P in this application is P=17.5 kN. Furthermore, using structural mechanics knowledge, the mid-span deflection of the bridge under external load can be determined. f and its bending stiffness B There exists a specific mathematical relationship between them. Based on theoretical derivation, under cracking load, the relationship between deflection and stiffness can be estimated using the following formula: In the formula, f The unit is m; B The unit is kN·m 2 .

[0054] A cracking load of P=17.5kN was applied to the 48 reinforced concrete beam models with different crack parameters, and the mid-span deflection of each beam model was calculated. The results are shown in Table 2.

[0055] Table 2 Calculation results of mid-span deflection of beam model

[0056] Note: Average crack spacing in the table The unit is cm, and the average height of the crack is [missing information]. The value represents the relative cross-sectional height, and the deflection is expressed in mm.

[0057] Based on the data given in Table 2, using the expression The stiffness of each beam model in Table 1 was calculated, as shown in Table 3: Table 3. Calculation results of beam model stiffness

[0058] Note: Average crack spacing in the table The unit is cm, and the average height of the crack is [missing information]. The height is the relative cross-section height, and the stiffness unit is kN·m. 2 .

[0059] Based on the expression for the flexural stiffness of reinforced concrete beams Calculate the stress non-uniformity coefficient of the tensile reinforcement in each beam model in Table 1 based on the data in Table 3. The values ​​and results are shown in Table 4: Table 4. Stress non-uniformity coefficient of tensile reinforcement in beam model Value calculation results

[0060] Note: Average crack spacing in the table The unit is cm, and the average height of the crack is [missing information]. Relative cross-sectional height It is a dimensionless unit.

[0061] In one specific implementation, the data in Table 4 are used to plot the crack spacing under different conditions. - Curves, such as Figure 8 As shown. From Figure 8 From this, we can see that when <0.5 h hour, The value increases linearly with the increase of the average crack propagation height; when >0.5 h hour, - The slope of the curve tends to flatten. Especially when >0.7 h hour, The value remains basically unchanged.

[0062] In one specific implementation, utilizing Figure 8 middle =7.5cm - The curve was fitted using two methods: linear regression and quadratic polynomial regression. The results were obtained from... Figure 9 As shown. From Figure 9 It can be seen that the quadratic polynomial model has a better fitting effect, while the linear model has a poor fitting effect. Figure 9 In the linear regression curve, the goodness-of-fit index R = 0.947, and the goodness-of-fit index R of the quadratic polynomial regression curve is... 2 =0.995, which indicates that the fitting effect of the quadratic polynomial model is better than that of the linear model. Figure 8 Other - The same conclusion can be obtained by fitting the curve.

[0063] Using the data in Table 4, plot the average crack development height for different values. - Curves, such as Figure 10 As shown. By Figure 10 It can be seen that when When <30cm, The value decreases as the average crack spacing increases; when When >30cm, each - The slope of the curve tends to flatten.

[0064] Furthermore, regarding Figure 10 Given =0.2h - The curve is fitted, and the result is... Figure 11 Given. By Figure 11 It can be seen that the fitting effect of the quadratic polynomial model is significantly better than that of the linear model. Figure 11 In the quadratic polynomial regression curve, the goodness-of-fit index R0 is... 2 =0.999, proving that the fitting effect is excellent. Using Figure 11 Other - Fitting the curve yields the same conclusion. The single-factor parameter analysis above shows that the average crack propagation height under various working conditions is related to... The relationship between the average crack spacing and The relationships between them should be expressed using a quadratic polynomial regression model.

[0065] In one specific implementation, if it is to establish simultaneous consideration and Two factors To obtain a two-dimensional expression, it is necessary to examine the interaction between the average crack propagation height and the average crack spacing, and then determine a reasonable form of the fitted expression. In this application, a response surface methodology is used to study the interaction between the average crack propagation height and the average crack spacing through statistical analysis. and The significance of the interaction between the two factors.

[0066] First, a central composite design (CCD) was used to select the experimental sample set. and For factors, In response, this application reasonably determined 9 sample points within the parameter variation space. The sample set constructed using the original data in Table 4 and the newly added data obtained through finite element calculation is shown in Table 5.

[0067] Table 5. Sample set based on CCD ( α (Value is 1.68179)

[0068] Next, use specialized software (such as Python) to perform regression fitting on the two-dimensional data in Table 5. Set the initial regression model to a complete quadratic polynomial, and use the F-value method (with a significance threshold of 5%) to test the significance of each term in the complete quadratic polynomial regression model. The results are shown in Table 6. Based on Table 6, B 2 The term with a high Prob>F value indicates weak significance; therefore, term B should be removed from the response surface function. 2 Select the item and retain the rest.

[0069] Table 6. Significance tests of terms in the complete quadratic polynomial regression model (threshold 5%)

[0070] Table 7 presents the significance test results of the modified quadratic regression model using the least squares method. As shown in Table 7, the model's... This indicates that the regression model is extremely significant, while the lack-of-fit term is not significant; The test result is 0.979, indicating that the model fits well and the experimental error is small; the sufficient accuracy (signal-to-noise ratio) is much greater than 4, indicating that there is sufficient signal and the model fit is effective throughout the entire design space.

[0071] Table 7. Significance test of the modified regression model

[0072] As shown in Table 8, the significance of each item in the modified regression model is extremely significant. The effect of the average crack spacing on the stress non-uniformity coefficient of the tensile steel bars is not a simple linear relationship, and the interaction between the average crack spacing and the average crack propagation height cannot be ignored.

[0073] Table 8. Significance tests of each term in the modified quadratic regression model (threshold 5%)

[0074] The coefficients of each term in the modified quadratic regression model are estimated using the least squares method to obtain the final model expression: In the formula, the average spacing of the cracks is... The unit is cm, and the average height of the crack is [missing information]. Relative cross-sectional height It is a dimensionless unit.

[0075] The response surface spectrum is plotted on the final model expression, such as... Figure 12 As shown. Figure 12 In the map, the contour lines are elliptical, indicating a significant interaction between the average crack spacing and the average crack propagation height. The response surface model should include the interaction term.

[0076] In one embodiment of the present invention, static load testing and visual inspection are used to verify the accuracy of the final model expression. The test specimens used for verification are as follows: Figure 13-15 As shown, Figure 13-15 The test specimens shown are two reinforced concrete standard analog beams with a scale ratio of 1:2, numbered Tbeam1 and Tbeam2. The two beams have the same dimensions, with a span of 6.5m, a beam height of 550mm, and a web thickness of 100mm.

[0077] Static load testing mainly involves applying graded loads to the specimen, using displacement gauges and dial indicators to measure the mid-span deflection of the specimen under each load level, and then calculating the test stiffness value of the specimen using the deflection-stiffness relationship. Visual inspection mainly involves observing and recording the crack development of the specimens under various load levels, and then substituting the crack statistical parameters into the final model expression and the expression for the flexural stiffness of the reinforced concrete beam section.

[0078] The static load test employed a symmetrical loading method at two points symmetrically positioned at mid-span, with the two symmetrical loading points 3.25m apart. During the test, the load was manually applied to the distribution beam using jacks, and then the distribution beam evenly distributed the load to the design loading points, such as... Figure 16 As shown in Table 9; the results of the static load test are shown in Table 10-11.

[0079] Table 9. Stiffness test values ​​of specimens under various load levels

[0080]

[0081] Table 10 Statistical parameters of surface cracks in Tbeam1 specimens under various load levels

[0082] Table 11 Statistical parameters of surface cracks in Tbeam2 specimens under various load levels

[0083] Note: The average crack spacing in the table is in cm, and the average crack propagation height is the relative cross-sectional height.

[0084] In one specific implementation, the data in Tables 10 and 11 are processed using the final model expression to obtain the stress non-uniformity coefficient of the tensile reinforcement in the two specimens under various load levels, as shown in Table 12. The data in Table 12 are further processed using the expression for the flexural stiffness of reinforced concrete beam sections to obtain the calculated stiffness values ​​of the specimens under various load levels. The results are shown in Table 13.

[0085] Table 12. Variation of stress non-uniformity coefficient in tensile reinforcement of specimens caused by crack propagation under various load levels.

[0086] Table 13 Calculated stiffness values ​​of specimens under various load levels

[0087]

[0088] In one specific implementation, the stiffness test values ​​of Tbeam1 and Tbeam2 are compared, as shown in Tables 14 and 15.

[0089] Table 14 Tbeam1 and Compare

[0090] Table 15 Tbeam2 and Compare

[0091] As shown in Tables 14 and 15, the experimental stiffness values ​​of the specimens are close to the calculated values. In most cases, the relative error between the two is within ±20%, and the maximum relative error is approximately 30%. The above data demonstrate that the values ​​obtained in this application for estimating the true stiffness of cracked reinforced concrete beams... The value fitting formula (the expression of the corrected model) is relatively accurate and reliable.

[0092] The bridge structural safety performance evaluation method provided in this application demonstrates the relationship between the stiffness of reinforced concrete members and the development of surface cracks, and proves the coefficient of uniformity of steel strain. It characterizes the stiffness of concrete members B The study also examines important physical parameters related to the degradation process of concrete bridges, demonstrating that information on apparent defects in concrete bridges can be used to assess their overall safety performance.

[0093] like Figure 17 As shown, this application also provides a bridge structural safety performance evaluation system, comprising: Module 10 is used to obtain the strain non-uniformity coefficient of the reinforcing bars. And concrete cracking parameters, based on the coefficient of uniformity of steel strain Establish a numerical model for concrete cracking parameters; The fitting module 20 is used to perform numerical simulation and fitting of the numerical model based on the single-factor method to obtain the coefficient of non-uniformity of steel strain. Correspondence between parameters and concrete cracking parameters; Evaluation module 30 is used to evaluate the safety performance of bridge structures based on the corresponding relationships.

[0094] The bridge structural safety performance evaluation system provided in this application can execute the evaluation method provided in the above-described method embodiments. Its implementation principle and technical effect are similar, and will not be described in detail here.

[0095] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.

[0096] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0097] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in the device.

[0098] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating the safety performance of bridge structures, characterized in that, Includes the following steps: Obtaining the coefficient of non-uniformity of steel reinforcement strain And concrete cracking parameters, based on the aforementioned steel reinforcement strain non-uniformity coefficient A numerical model was established based on the concrete cracking parameters; Based on the single-factor method, the numerical model is numerically simulated and fitted to obtain the strain non-uniformity coefficient of the reinforcing steel. The correspondence between the parameters and the concrete cracking parameters; The safety performance of the bridge structure is evaluated based on the aforementioned correspondence.

2. The bridge structural safety performance evaluation method according to claim 1, characterized in that, The strain non-uniformity coefficient of the reinforcing steel The expression is: In the formula, The cracking moment of the component, M This represents the bending moment experienced by the member under the current external load.

3. The method for evaluating the safety performance of bridge structures according to claim 1, characterized in that, The concrete cracking parameters include the average crack height. and average crack spacing Based on the average height of the crack and average crack spacing Characterizes concrete cracks.

4. The method for evaluating the safety performance of bridge structures according to claim 3, characterized in that, The numerical model was built based on ANSYS software, and SOLID65 elements were used to simulate concrete material and PIPE20 elements were used to simulate steel bars. For the concrete material in the cracked zone, a distributed crack model was used for simulation, combined with the average crack height. and the average spacing of the cracks The reinforcing bars characterize the stress state of the concrete.

5. The method for evaluating the safety performance of bridge structures according to claim 3, characterized in that, When performing the fitting, a quadratic polynomial regression model is used. The average height of the crack With respect to the average spacing of the crack The strain non-uniformity coefficient of the steel reinforcement, respectively Perform a quadratic polynomial regression model fitting.

6. The method for evaluating the safety performance of bridge structures according to claim 5, characterized in that, The quadratic polynomial regression model is modified using the least squares method to obtain the modified model, the expression of which is: In the formula, the average spacing of the cracks is... The unit is cm, and the average height of the crack is [missing information]. Relative cross-sectional height The coefficient of non-uniformity of steel reinforcement strain .

7. The method for evaluating the safety performance of bridge structures according to any one of claims 2-6, characterized in that, The process also includes verifying the correspondence, which involves static load testing and visual inspection. The static load test includes applying graded loads to the specimen, measuring the mid-span deflection of the specimen under each load level using a displacement gauge and a dial indicator, and then calculating the test stiffness value of the specimen using the deflection-stiffness relationship. ; The visual inspection includes observing and recording the crack development of the specimen under various load levels, and then calculating the stiffness value of the specimen using the modified model and the cross-sectional bending stiffness expression of the reinforced concrete beam. ; Based on the above and stated The correspondence is verified.

8. The method for evaluating the safety performance of bridge structures according to claim 7, characterized in that, The expression for the flexural stiffness of the reinforced concrete beam section is: In the formula, The effective height of the cross section, This is the coefficient of non-uniformity of the reinforcing steel strain. The elastic modulus of the steel reinforcement. For the area of ​​the reinforcing steel, This refers to the longitudinal tensile reinforcement ratio.

9. A bridge structural safety performance evaluation system, characterized in that, include: The acquisition module is used to obtain the coefficient of uniformity of strain in steel bars. And concrete cracking parameters, based on the aforementioned steel reinforcement strain non-uniformity coefficient A numerical model was established based on the concrete cracking parameters; The fitting module is used to perform numerical simulation and fitting of the numerical model based on the single-factor method to obtain the strain non-uniformity coefficient of the reinforcing steel. The correspondence between the parameters and the concrete cracking parameters; The evaluation module is used to evaluate the safety performance of the bridge structure based on the aforementioned correspondence.

10. A computer-readable storage medium, characterized in that, The storage medium stores program instructions, which, when executed, implement the bridge structure safety performance evaluation method as described in any one of claims 1-8.

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