Method for evaluating stability of thick-walled high-strength steel pipe concrete bridge pier foundation

Abstract

The application provides a thick-walled high-strength steel pipe concrete bridge pier foundation stability evaluation method, and relates to the technical field of civil safety evaluation.The three-dimensional geometric model of the high-strength steel pipe concrete bridge pier is divided into a bridge pier core area and a steel pipe concrete area, the core area is finely divided by a mode shape partition method, the characteristic parameters related to the stability of the bridge pier in the stress weak position of each sub-area are extracted, a core area stability evaluation function is constructed and evaluated, the axial ultimate bearing capacity and the total normal stress of the overall area are calculated for the steel pipe concrete area, finally, the cross-section ultimate bearing stress is calculated according to the radius ratio of the core area and the overall area, the comprehensive stability coefficient is generated, and the stability evaluation standard of the steel pipe concrete bridge pier is provided.The application realizes the accurate evaluation of the safety of the steel pipe concrete bridge pier structure by the multi-scale partition analysis and the collaborative mechanics method, and constructs a comprehensive stability evaluation system.

Description

Technical Field

[0001] This invention relates to the field of civil safety assessment technology, specifically to a method for evaluating the stability of thick-walled high-strength steel-concrete composite bridge pier foundations. Background Technology

[0002] With the continuous development of urban infrastructure construction, the safety and stability of bridge pier structures, as important transportation hubs, are receiving increasing attention. High-strength steel-concrete composite piers are widely used in bridge engineering due to their excellent load-bearing capacity and good durability. However, in practical engineering applications, the heterogeneity of materials, structural complexity, and diverse load conditions of thick-walled high-strength steel-concrete composite piers lead to complex stress states and make stability evaluation difficult. Furthermore, due to the influence of static and dynamic loads, the cross-sectional dimensions of the piers cannot be too small and must meet the structural stress requirements. At the same time, the durability of underwater piers will also constrain the design of pier structures.

[0003] In existing technologies, traditional stability assessments mostly focus on calculating the overall structural bearing capacity, lacking regional division and detailed evaluation methods. This makes it difficult to accurately identify the different stress behaviors of the core area of ​​the pier and the outer structure and their impact on overall stability. Furthermore, traditional stability assessment methods often evaluate high-strength steel-concrete composite piers as a whole, easily neglecting the structural stability of the pier itself. In addition, while finite element analysis is widely used in structural mechanics and can provide detailed stress and strain distribution information, how to combine finite element results to scientifically divide structural regions, extract key characteristic parameters, and construct a reasonable stability assessment model remains a technical challenge.

[0004] Therefore, it is necessary to propose a stability evaluation method for thick-walled high-strength steel-concrete composite bridge pier foundations to solve the aforementioned problem.

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for evaluating the stability of thick-walled high-strength steel tube concrete bridge pier foundations, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for evaluating the stability of thick-walled high-strength steel-concrete composite bridge pier foundations, comprising the following steps:

[0009] Step 1: Collect the geometric and material parameters of the steel-concrete composite pier to be analyzed, establish a three-dimensional geometric model of the steel-concrete composite pier based on finite element analysis software, apply simulated loads to the three-dimensional geometric model, and divide the three-dimensional geometric model of the steel-concrete composite pier into the core area of ​​the pier and the steel-concrete composite area based on the stress distribution.

[0010] Step 2: Based on the modal zoning method, the core area of ​​the bridge pier is divided into several sub-regions. The weak stress locations in each sub-region are screened out according to the stress structure analysis method. The structural parameters of the weak stress locations are calculated to obtain the characteristic parameters related to the stability of the steel-concrete composite bridge pier in each sub-region.

[0011] Step 3: Normalize the feature parameters of each sub-region, and construct a stability evaluation function for the core region of the pier based on the principle of structural stability evaluation. Evaluate the stability of the core region of the pier based on the constructed stability evaluation function.

[0012] Step 4: For the steel-concrete composite area on the outer layer of the pier, based on the theory of synergistic mechanics, axial compression analysis and eccentric compression analysis are performed on the steel-concrete composite area with the pier as the core, and the axial ultimate bearing capacity and total normal stress in the cross section of the entire pier area are calculated respectively.

[0013] Step 5: Calculate the ultimate bearing stress of the pier section in the whole area based on the radius ratio of the core area of ​​the pier to the whole area of ​​the pier. Combine the axial ultimate bearing capacity in the pier section in the whole area with the normalized total normal stress to generate a comprehensive stability coefficient as the stability evaluation standard for steel-concrete composite piers.

[0014] Furthermore, a three-dimensional geometric model of the steel-concrete composite bridge pier was established and simulated loads were applied. Based on the stress distribution, the three-dimensional geometric model was divided into regions. The method used was as follows:

[0015] The geometric parameters of the steel-concrete composite pier to be analyzed are obtained, including the pier height, wall thickness, and top and bottom diameters. At the same time, the connection dimensions between the pier and the foundation and abutment are obtained, as well as the relevant material parameters, including the elastic modulus, yield strength and Poisson's ratio of the steel pipe, and the elastic modulus, compressive strength and Poisson's ratio of the concrete.

[0016] A three-dimensional geometric model of a steel-concrete composite pier is established using ANSYS finite element analysis software. The ANSYS workbench is started, the geometry module is selected, the inner and outer cylinders of the steel tube are drawn, and the steel tube solid is generated by the "Extrude" command. The solid of the concrete filling area is drawn according to the design cross-sectional dimensions of the pier, which is usually the solid filling inside the steel tube. The connecting parts such as the abutment and foundation are drawn. Boolean operations such as "merge", "intersect" and "shear" are performed to form the three-dimensional geometric model of the steel-concrete composite pier in the initial state.

[0017] In the ANSYS engineering data module, create material libraries for steel pipes and concrete, accurately input the elastic modulus, Poisson's ratio, yield strength, and compressive strength, and then mesh the model. The specific method is as follows: enter the "Mesh" module, perform reasonable meshing for steel pipes and concrete respectively, use shell elements for steel pipes and solid elements for concrete, and use a dense mesh for the connection area of ​​the model. Apply zero displacement constraints to all degrees of freedom of the relevant nodes at the bottom of the pier to simulate the rigid fixation of the foundation, and simulate the elastic deformation of the foundation through spring elements. Define the spring stiffness in different directions to simulate the interaction between the foundation and the subgrade. Set the interface between steel pipes and concrete to "bond" condition, that is, the nodes of both are shared and set to no relative slip. Based on the above steps, the final three-dimensional geometric model of the steel-concrete composite pier is obtained.

[0018] Simulated loads are applied to the model, concrete compressive stress is selected as the key stress index, and a stress discrimination threshold is preset. The average stress level of the main steel-concrete composite area of ​​the entire pier is calculated. The core stress range is determined by combining the set stress discrimination threshold. The core area is separated from the main area using software functions, and the three-dimensional geometric model is divided into the pier core area and the steel-concrete composite area.

[0019] Furthermore, based on the stress-structure analysis method, the weak points in each sub-region were identified, and the characteristic parameters related to the stability of the bridge piers in each sub-region were obtained. The method used was as follows:

[0020] Based on the modal zoning method, the core area of ​​the bridge pier is divided into the pier main body area, the pier top connection area, and the pier bottom support area. The method for determining the weak points in the pier main body area is as follows: calculate the stress at each section along the pier height, and identify the section corresponding to the location of the maximum normal stress as the weak cross section. Combine this with a finite element stress cloud diagram to confirm the weak cross section as the weak point in the pier main body area. The method for determining the weak points in the pier top connection area is as follows: calculate the local stiffness at different sections of the cap beam, use a finite element model to simulate the stiffness transfer at the connection between the cap beam and the pier, identify areas of abrupt stiffness changes, calculate the maximum local normal stress at the connection, and combine this with the modal zoning method to determine the weak points. The specific locations with large amplitude and low stiffness in the connection area, i.e., the nodes where the cross-sectional stiffness of the connection area between the cap beam and the pier column changes abruptly and stress concentrates, are designated as the weak points in the connection area at the top of the pier column. The method for determining the weak points in the support area at the bottom of the pier column is as follows: calculate the contact area between the foundation cap and the ground, obtain the average contact pressure of the foundation cap in combination with the load, analyze the contact pressure distribution using elastic contact theory, identify the local pressure peak area, and combine the shear force and bending moment in this area to perform superimposed analysis on the stress of the bottom section. Use finite element local refinement to simulate the stress and deformation at the support, and designate the edge area of ​​the contact surface between the cap and the ground as the weak points in the support area at the bottom of the pier column.

[0021] For the identified weak points in each sub-region, structural parameters are calculated to obtain characteristic parameters related to the stability of the steel-concrete composite piers in each sub-region. The formula used is as follows:

[0022]

[0023]

[0024]

[0025] in, The geometric efficiency coefficient of the cross section at the weakest point in the main body of the pier column. The area of ​​the weak cross section. The perimeter of the weak cross section. This represents the stiffness coefficient of the cap beam connection node at the weakest point in the connection zone at the top of the pier column. The elastic modulus of the cap beam is the material modulus of elasticity. Let be the second moment of inertia of the section at the connection of the cap beam. This represents the local stress coefficient at the weakest point in the support zone at the bottom of the pier column. This refers to the vertical load at the edge of the contact surface between the foundation cap and the ground. This refers to the bearing area at the edge of the contact surface between the foundation and the ground.

[0026] Furthermore, a stability evaluation function for the core area of ​​the bridge pier is constructed to evaluate the stability of the core area of ​​the bridge pier. The method used is as follows:

[0027] A stability evaluation function for the core area of ​​the bridge pier is constructed by combining the normalized characteristic parameters of each sub-region with the structural stability evaluation principle. The structural stability evaluation principle consists of two parts: the first part is the structural bearing capacity index, which is composed of normalized characteristic parameters characterizing the structural bearing performance. , The first part is constructed using a linear weighting method. The second part is the stress effect index on the structure, which consists of normalized characteristic parameters that characterize the magnitude of stress concentration. The linear weighted average is based on the following formula:

[0028]

[0029] in, Indicates the stability of the core area of ​​the bridge pier. , , These are the weighting coefficients of the feature parameters for each sub-region. , , These represent the normalized feature parameters of each sub-region;

[0030] When the calculation results of the stability evaluation function of the core area of ​​the bridge pier When the calculation result indicates that the core area of ​​the bridge pier is in a stable state, it means that the core area of ​​the bridge pier is in a stable state. This indicates that there is a risk of instability in the core area of ​​the bridge pier.

[0031] Furthermore, the method used to calculate the axial ultimate bearing capacity and total normal stress within the overall cross-section of the bridge pier is as follows:

[0032] Based on the theory of synergistic mechanics, assuming good bonding between the steel pipe and concrete, no relative slippage within the cross-section, and that the axial compressive ultimate bearing capacity of the pier is jointly borne by the steel pipe and concrete, the formula used to calculate the axial ultimate bearing capacity of the entire pier region is as follows:

[0033]

[0034] in, This represents the axial ultimate bearing capacity of the entire pier area. , These represent the cross-sectional areas of the steel pipe and the concrete, respectively. Design yield strength for steel pipes, The ultimate axial compressive stress is designed for concrete. This is the resistance coefficient;

[0035] After determining the eccentricity of the entire pier area, the ultimate bending moment limit of the pier section is calculated based on the fundamental conditions of synergistic mechanics theory. The formula used is as follows:

[0036]

[0037] in, Indicates the eccentricity of the entire area of ​​the bridge pier. This represents the ultimate bending moment that the bridge pier section can withstand.

[0038] The total normal stress within the cross-section of the bridge pier is mainly composed of the uniform normal stress generated by axial pressure and the additional stress generated by bending moment, based on the following formula:

[0039]

[0040] in, This represents the total normal stress within the cross-section of the entire pier region. This represents the cross-sectional area of ​​the entire bridge pier area. This represents the perpendicular distance from the edge point of the cross-section to the neutral axis of the cross-section, and The sign is used to distinguish the vertical position of the cross-section. Let be the moment of inertia of the cross section about the neutral axis.

[0041] Furthermore, the ultimate bearing stress of the pier section in the entire pier region is calculated based on the radius ratio of the core area to the overall area of ​​the pier, and a comprehensive stability coefficient is generated to evaluate the overall stability of the pier. The method used is as follows:

[0042] The radius ratio is defined as the ratio of the radius of the core area of ​​the pier to the outer diameter of the entire pier area, based on the following formula:

[0043]

[0044] in, This represents the ratio of the radius of the core area of ​​the bridge pier to the radius of the entire bridge pier area. The radius of the core area of ​​the bridge pier. The outer diameter of the entire pier area;

[0045] Based on the synergistic load-bearing contribution of the steel pipe and the core concrete, and combined with the radius ratio, the ultimate bearing stress of the section is calculated using the following formula:

[0046]

[0047] in, This represents the ultimate bearing stress of the cross-section in the entire region of the bridge pier;

[0048] The axial stress parameter is normalized based on the uniform normal stress generated by the axial pressure acting on the entire cross-section of the bridge pier, and the bending moment stress parameter is normalized based on the additional stress caused by the bending moment acting on the entire cross-section of the bridge pier. The formula used is as follows:

[0049]

[0050]

[0051]

[0052] in, This represents the axial stress parameters of the entire cross-section of the bridge pier. The bending moment and stress parameters represent the overall cross-section of the bridge pier.

[0053] Based on the calculated ultimate bearing stress of the cross section in the overall region of the pier, a comprehensive stability coefficient is established by combining the axial ultimate bearing capacity and the normalized total normal stress within the cross section of the overall region of the pier. The influence of axial and bending moment stresses is comprehensively considered, and a weighting factor is adopted. The formula used to reflect the adjusting effect of bending moment on force is:

[0054]

[0055]

[0056] in, This represents the comprehensive stability coefficient used to characterize the overall regional stability of the bridge pier. , These are empirical parameters that reflect the nonlinear adjustment of the effect of changes in pier wall thickness on bending moment.

[0057] The overall stability of the bridge pier area is judged based on the established comprehensive stability coefficient. If the entire area of ​​the bridge pier meets the stability requirements; if If so, corresponding reinforcement or design optimization measures should be taken to improve structural stability.

[0058] Compared with the prior art, the beneficial effects of the present invention are:

[0059] This invention establishes a three-dimensional geometric model of a thick-walled, high-strength steel-concrete composite bridge pier based on finite element analysis software, accurately simulates the stress distribution of the pier under actual working conditions, realizes the refined regional division of the core area structure of the pier, clearly distinguishes the core area of ​​the pier from the steel-concrete composite area, and solves the problem of difficulty in identifying different stress behaviors of the structure in traditional methods.

[0060] This invention employs a modal zoning method combined with stress-structure analysis to scientifically identify weak points in each sub-region and extract key structural parameters, providing a quantitative basis for pier stability evaluation. Furthermore, it constructs a stability evaluation function based on structural bearing capacity and stress effects, which can comprehensively reflect the overall stability of the pier area and effectively predict the risk of instability in the overall pier area. Attached Figure Description

[0061] Figure 1 This is a schematic diagram of the overall method flow of the present invention. Detailed Implementation

[0062] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0063] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0064] Example:

[0065] Please see Figure 1 A method for evaluating the stability of thick-walled high-strength steel tube concrete bridge pier foundations, comprising the following specific steps:

[0066] Step 1: Collect the geometric and material parameters of the steel-concrete composite pier to be analyzed, establish a three-dimensional geometric model of the steel-concrete composite pier based on finite element analysis software, apply simulated loads to the three-dimensional geometric model, and divide the three-dimensional geometric model of the steel-concrete composite pier into the core area of ​​the pier and the steel-concrete composite area based on the stress distribution.

[0067] In a specific embodiment of this invention, since the thick-walled high-strength steel-concrete composite pier structure we analyzed is complex, its stress state is significantly affected by geometric parameters, material properties, and actual loads. The interaction between these parameters directly affects the overall stability of the pier. Therefore, we first established a three-dimensional geometric model of the steel-concrete composite pier using finite element analysis software. The simulated loads we used here mainly consist of the pier's self-weight, the standard live load specified in the code, and the horizontal load. By simulating the actual load conditions, we obtained the true stress distribution in each area of ​​the pier, providing data support for subsequent stability evaluation.

[0068] It should be noted that the three-dimensional geometric model of the steel-concrete composite pier is divided into the pier core area and the steel-concrete composite area because the two have significant differences in stress characteristics and structural functions. The pier core area usually bears higher stress concentration and complex stress conditions, and is the key part of the structure that is prone to instability or failure. On the other hand, the steel-concrete composite area mainly plays the role of overall load-bearing and restraint. By scientifically dividing these two areas, the key stress links of the structure can be accurately identified and analyzed, and stability characteristic parameters can be extracted more specifically. This effectively avoids ignoring local weak links due to overall averaging, and improves the detail and accuracy of stability analysis.

[0069] Therefore, it is necessary to establish a three-dimensional geometric model of the steel-concrete composite bridge pier and apply simulated loads. The three-dimensional geometric model is then divided into regions based on stress distribution. The method used is as follows:

[0070] The geometric parameters of the steel-concrete composite pier to be analyzed are obtained, including the pier height, wall thickness, and top and bottom diameters. At the same time, the connection dimensions between the pier and the foundation and abutment are obtained, as well as the relevant material parameters, including the elastic modulus, yield strength and Poisson's ratio of the steel pipe, and the elastic modulus, compressive strength and Poisson's ratio of the concrete.

[0071] A three-dimensional geometric model of a steel-concrete composite pier is established using ANSYS finite element analysis software. The ANSYS workbench is started, the geometry module is selected, the inner and outer cylinders of the steel tube are drawn, and the steel tube solid is generated by the "Extrude" command. The solid of the concrete filling area is drawn according to the design cross-sectional dimensions of the pier, which is usually the solid filling inside the steel tube. The connecting parts such as the abutment and foundation are drawn. Boolean operations such as "merge", "intersect" and "shear" are performed to form the three-dimensional geometric model of the steel-concrete composite pier in the initial state.

[0072] In the ANSYS engineering data module, create material libraries for steel pipes and concrete, accurately input the elastic modulus, Poisson's ratio, yield strength, and compressive strength, and then mesh the model. The specific method is as follows: enter the "Mesh" module, perform reasonable meshing for steel pipes and concrete respectively, use shell elements for steel pipes and solid elements for concrete, and use a dense mesh for the connection area of ​​the model. Apply zero displacement constraints to all degrees of freedom of the relevant nodes at the bottom of the pier to simulate the rigid fixation of the foundation, and simulate the elastic deformation of the foundation through spring elements. Define the spring stiffness in different directions to simulate the interaction between the foundation and the subgrade. Set the interface between steel pipes and concrete to "bond" condition, that is, the nodes of both are shared and set to no relative slip. Based on the above steps, the final three-dimensional geometric model of the steel-concrete composite pier is obtained.

[0073] Simulated loads are applied to the model, concrete compressive stress is selected as the key stress index, and a stress discrimination threshold is preset. The average stress level of the main steel-concrete composite area of ​​the entire pier is calculated. The core stress range is determined by combining the set stress discrimination threshold. The core area is separated from the main area using software functions, and the three-dimensional geometric model is divided into the pier core area and the steel-concrete composite area.

[0074] Step 2: Based on the modal zoning method, the core area of ​​the bridge pier is divided into several sub-regions. The stress-structure analysis method is used to screen out the weak stress locations in each sub-region, and the structural parameters of the weak stress locations are calculated to obtain the characteristic parameters related to the stability of the steel-concrete composite bridge pier in each sub-region.

[0075] In a specific embodiment of this invention, we use modal zoning to divide the core area of ​​the bridge pier. The specific method is as follows: First, modal analysis is performed on the core area model of the bridge pier established in step 1 to calculate its multiple main modes of vibration and their corresponding shapes. Through modal analysis, the deformation modes of the bridge pier at different natural frequencies are identified, and the degree of influence of different modes of vibration on different parts of the structure is obtained. Based on the amplitude distribution characteristics of the mode shapes, the core area of ​​the bridge pier is divided into several sub-regions. Each sub-region corresponds to a structural part with a significant amplitude response in a certain mode of vibration, ensuring that the division reflects the spatial distribution characteristics of the structural dynamic response and facilitating the focus on key areas where the structural dynamics are easily affected. The stress structure analysis method is used to screen the weak stress locations in each sub-region. By calculating the stress concentration, strain energy density, and stiffness distribution of each sub-region, the weak locations with the maximum stress or the lowest stiffness are identified. These locations are often the potential starting points of structural failure.

[0076] It should be noted that the reason we need to calculate and obtain the characteristic parameters of the weak points in each sub-region is that by accurately identifying and quantifying the structural characteristic parameters of the weak points in each sub-region, we can comprehensively reflect the mechanical state and potential stability risks of the local weak links, and effectively capture the local instability trends in the overall structure that are not easily reflected by the overall average parameters.

[0077] Therefore, it is necessary to use stress-structure analysis to identify the weak points in each sub-region and obtain the characteristic parameters related to the stability of the bridge piers in each sub-region. The method used is as follows:

[0078] Based on the modal zoning method, the core area of ​​the bridge pier is divided into the pier main body area, the pier top connection area, and the pier bottom support area. The method for determining the weak points in the pier main body area is as follows: calculate the stress at each section along the pier height, and identify the section corresponding to the location of the maximum normal stress as the weak cross section. Combine this with a finite element stress cloud diagram to confirm the weak cross section as the weak point in the pier main body area. The method for determining the weak points in the pier top connection area is as follows: calculate the local stiffness at different sections of the cap beam, use a finite element model to simulate the stiffness transfer at the connection between the cap beam and the pier, identify areas of abrupt stiffness changes, calculate the maximum local normal stress at the connection, and combine this with the modal zoning method to determine the weak points. The specific locations with large amplitude and low stiffness in the connection area, i.e., the nodes where the cross-sectional stiffness of the connection area between the cap beam and the pier column changes abruptly and stress concentrates, are designated as the weak points in the connection area at the top of the pier column. The method for determining the weak points in the support area at the bottom of the pier column is as follows: calculate the contact area between the foundation cap and the ground, obtain the average contact pressure of the foundation cap in combination with the load, analyze the contact pressure distribution using elastic contact theory, identify the local pressure peak area, and combine the shear force and bending moment in this area to perform superimposed analysis on the stress of the bottom section. Use finite element local refinement to simulate the stress and deformation at the support, and designate the edge area of ​​the contact surface between the cap and the ground as the weak points in the support area at the bottom of the pier column.

[0079] For the identified weak points in each sub-region, structural parameters are calculated to obtain characteristic parameters related to the stability of the steel-concrete composite piers in each sub-region. The formula used is as follows:

[0080]

[0081]

[0082]

[0083] in, The geometric efficiency coefficient of the cross section at the weakest point in the main body of the pier column. The area of ​​the weak cross section. The perimeter of the weak cross section. This represents the stiffness coefficient of the cap beam connection node at the weakest point in the connection zone at the top of the pier column. The elastic modulus of the cap beam is the material modulus of elasticity. Let be the second moment of inertia of the section at the connection of the cap beam. This represents the local stress coefficient at the weakest point in the support zone at the bottom of the pier column. This refers to the vertical load at the edge of the contact surface between the foundation cap and the ground. This refers to the bearing area at the edge of the contact surface between the foundation and the ground.

[0084] It should be noted that the geometric efficiency coefficient of the cross-section at the weakest point in the main body of the pier reflects the shape and size characteristics of the weakest cross-section, and its area. With perimeter The ratio of the geometric efficiency coefficient to the cross-sectional stability and resistance to local buckling of the cross-section reflects the cross-sectional stability and resistance to local buckling. A larger geometric efficiency coefficient indicates that the cross-section has better load-bearing capacity and resistance to local instability. It can accurately characterize the cross-sectional stability features of weak points in the main body of the pier column; the stiffness of the cap beam connection node directly affects the overall stiffness distribution and force transmission efficiency of the structure, and the material elastic modulus. Represents the rigidity of the material, while the second moment of inertia The product of the two reflects the bending resistance of the cross section. The data comprehensively demonstrates the deformation resistance and bending instability resistance of the connection node, effectively reflecting the structural stiffness characteristics of the connection area and its contribution to overall stability. The local stress coefficient at the weakest point in the pier bottom support area reflects the vertical load from the pile cap and foundation borne by the pier bottom support area, and its local stress level is key to stability analysis. This represents the vertical load acting on the edge of the contact surface. The ratio of the two to the carrying area. It represents the stress per unit area, directly reflecting the load-bearing state and potential risks of indentation or slippage in the area. This parameter can accurately characterize the load concentration and stability hazards in the bottom support area, and is an important characteristic parameter of the weak stress location in this sub-region.

[0085] Step 3: Normalize the feature parameters of each sub-region, and construct a stability evaluation function for the core region of the pier based on the principle of structural stability evaluation. Evaluate the stability of the core region of the pier based on the constructed stability evaluation function.

[0086] In a specific embodiment of the present invention, since the physical dimensions and numerical ranges of the characteristic parameters may differ greatly, direct comparison or input into the model can easily lead to weight imbalance. Normalization can convert each parameter to a uniform dimensional scale, making them comparable. Combining the structural stability evaluation principle, a stability evaluation of the core area of ​​the bridge pier is constructed, realizing a comprehensive quantitative analysis of the mechanical properties and weak points of different areas.

[0087] It should be noted that the principle of structural stability evaluation is usually based on performance functions. ,in For the load-bearing capacity of the structure, corresponding to the evaluation function we established, This part, The stress effect on the structure corresponds to the value in our established evaluation function. In this part, based on this principle, when the performance function When the load is greater than the load, it indicates that the structure is in a safe state and can stably bear the load; when When this occurs, it indicates that the stress effect on the structure exceeds or equals its bearing capacity, and the structure is at risk of instability.

[0088] Furthermore, a stability evaluation function for the core area of ​​the bridge pier is constructed to evaluate the stability of the core area of ​​the bridge pier. The method used is as follows:

[0089] A stability evaluation function for the core area of ​​the bridge pier is constructed by combining the normalized characteristic parameters of each sub-region with the structural stability evaluation principle. The structural stability evaluation principle consists of two parts: the first part is the structural bearing capacity index, which is composed of normalized characteristic parameters characterizing the structural bearing performance. , The first part is constructed using a linear weighting method. The second part is the stress effect index on the structure, which consists of normalized characteristic parameters that characterize the magnitude of stress concentration. The linear weighted average is based on the following formula:

[0090]

[0091] in, Indicates the stability of the core area of ​​the bridge pier. , , These are the weighting coefficients of the feature parameters for each sub-region. , , This represents the normalized feature parameters of each sub-region; in the stability evaluation function constructed above, The bearing capacity of the main pier area is represented by normalization and multiplied by weights. This can effectively reflect the area's contribution to the overall carrying capacity. Representing the load-bearing capacity of the top connection zone, using a logarithmic function can improve the sensitivity of the evaluation, highlighting the weakening effect of structural load-bearing capacity when the parameter is small, while ensuring that the function is defined when the parameter is zero. The two together constitute the load-bearing capacity index in the stability evaluation function. This represents the stress concentration in the bottom support area. Since stress concentration is a common cause of structural instability, it is used as a stress effect index in the stability evaluation function, with the weighting coefficients set to [value missing]. Furthermore, each weight coefficient is greater than zero. The purpose of this setting is that, in the structural stability of the core area of ​​the pier, the stress concentration in the bottom support area is often the main weak link and potential source of danger leading to structural instability or damage. Once the stress concentration exceeds the limit, it can easily induce serious problems such as cracks and shear failure. Therefore, setting the weight of the local stress coefficient in the bottom support area to twice that of the other weights can more effectively warn of the risk of structural instability.

[0092] When the calculation results of the stability evaluation function of the core area of ​​the bridge pier When the calculation result indicates that the core area of ​​the bridge pier is in a stable state, it means that the core area of ​​the bridge pier is in a stable state. This indicates that there is a risk of instability in the core area of ​​the bridge pier.

[0093] Step 4: For the steel-concrete composite area on the outer layer of the pier, based on the theory of synergistic mechanics, axial compression analysis and eccentric compression analysis are performed on the steel-concrete composite area with the pier as the core, and the axial ultimate bearing capacity and total normal stress in the cross section of the entire pier area are calculated respectively.

[0094] In a specific embodiment of this invention, the steel-concrete composite material region on the outer layer of the bridge pier is an important component of the core structure of the pier. It possesses the mechanical properties of composite materials and good load-bearing capacity. Mechanical analysis of this region, especially axial compression and eccentric compression analysis, is fundamental to ensuring the stability and safety of the bridge pier under complex loads. We conduct axial compression analysis and eccentric compression analysis on the steel-concrete composite material. Axial compression analysis reflects the bearing limit of the bridge pier under vertical loads, determining whether the bridge pier has sufficient bearing capacity to resist vertical pressure. Eccentric compression analysis considers the unavoidable eccentric loads in actual working conditions, reflecting the stress state of the bridge pier under the combined action of bending moment and axial force, providing a more realistic structural stress representation. Through this analysis, additional stress concentration areas caused by eccentricity can be identified, preventing local instability or failure.

[0095] Furthermore, the method used to calculate the axial ultimate bearing capacity and total normal stress within the overall cross-section of the bridge pier is as follows:

[0096] Based on the theory of synergistic mechanics, assuming good bonding between the steel pipe and concrete, no relative slippage within the cross-section, and that the axial compressive ultimate bearing capacity of the pier is jointly borne by the steel pipe and concrete, the formula used to calculate the axial ultimate bearing capacity of the entire pier region is as follows:

[0097]

[0098] in, This represents the axial ultimate bearing capacity of the entire pier area. , These represent the cross-sectional areas of the steel pipe and the concrete, respectively. Design yield strength for steel pipes, The ultimate axial compressive stress is designed for concrete. This is the resistance coefficient;

[0099] After determining the eccentricity of the entire pier area, the ultimate bending moment limit of the pier section is calculated based on the fundamental conditions of synergistic mechanics theory. The formula used is as follows:

[0100]

[0101] in, Indicates the eccentricity of the entire area of ​​the bridge pier. This represents the ultimate bending moment that the bridge pier section can withstand.

[0102] The total normal stress within the cross-section of the bridge pier is mainly composed of the uniform normal stress generated by axial pressure and the additional stress generated by bending moment, based on the following formula:

[0103]

[0104] in, This represents the total normal stress within the cross-section of the entire pier region. This represents the cross-sectional area of ​​the entire bridge pier area. This represents the perpendicular distance from the edge point of the cross-section to the neutral axis of the cross-section, and The sign is used to distinguish the vertical position of the cross-section. Let be the moment of inertia of the cross section about the neutral axis.

[0105] Step 5: Calculate the ultimate bearing stress of the pier section in the whole area based on the radius ratio of the core area of ​​the pier to the whole area of ​​the pier. Combine the axial ultimate bearing capacity in the pier section in the whole area with the normalized total normal stress to generate a comprehensive stability coefficient as the stability evaluation standard for steel-concrete composite piers.

[0106] In a specific embodiment of the present invention, we introduce the radius ratio of the core area of ​​the pier to the overall area in step 5, organically combining local structural features with overall stress performance, and calculating a more accurate ultimate bearing stress of the overall pier section. Then, we combine the axial ultimate bearing capacity with the normalized total normal stress to form a comprehensive stability coefficient, realizing a multi-dimensional and quantitative evaluation of the stability of steel-concrete composite piers. This radius ratio-based calculation method breaks through the limitations of traditional single-section bearing capacity analysis, and can more comprehensively reflect the mechanical contributions and mutual influences of different areas of the pier section, improving the scientificity and practicality of stability evaluation.

[0107] Furthermore, the ultimate bearing stress of the pier section in the entire pier region is calculated based on the radius ratio of the core area to the overall area of ​​the pier, and a comprehensive stability coefficient is generated to evaluate the overall stability of the pier. The method used is as follows:

[0108] The radius ratio is defined as the ratio of the radius of the core area of ​​the pier to the outer diameter of the entire pier area, based on the following formula:

[0109]

[0110] in, This represents the ratio of the radius of the core area of ​​the bridge pier to the radius of the entire bridge pier area. The radius of the core area of ​​the bridge pier. The outer diameter of the entire pier area;

[0111] Based on the synergistic load-bearing contribution of the steel pipe and the core concrete, and combined with the radius ratio, the ultimate bearing stress of the section is calculated using the following formula:

[0112]

[0113] in, This represents the ultimate bearing stress of the cross-section in the entire region of the bridge pier;

[0114] The axial stress parameter is normalized based on the uniform normal stress generated by the axial pressure acting on the entire cross-section of the bridge pier, and the bending moment stress parameter is normalized based on the additional stress caused by the bending moment acting on the entire cross-section of the bridge pier. The formula used is as follows:

[0115]

[0116]

[0117]

[0118] in, This represents the axial stress parameters of the entire cross-section of the bridge pier. The bending moment and stress parameters represent the overall cross-section of the bridge pier.

[0119] Based on the calculated ultimate bearing stress of the cross section in the overall region of the pier, a comprehensive stability coefficient is established by combining the axial ultimate bearing capacity and the normalized total normal stress within the cross section of the overall region of the pier. The influence of axial and bending moment stresses is comprehensively considered, and a weighting factor is adopted. The formula used to reflect the adjusting effect of bending moment on force is:

[0120]

[0121]

[0122] in, This represents the comprehensive stability coefficient used to characterize the overall regional stability of the bridge pier. , These are empirical parameters that reflect the nonlinear adjustment of the effect of changes in pier wall thickness on bending moment; in the above formula for establishing the comprehensive stability coefficient, It is the average normal stress generated by axial pressure on the overall cross section of the bridge pier. It is the effect of the foundation axial load on the structure. The larger the value, the greater the axial pressure on the bridge pier, and the stress is close to or exceeds the bearing limit of the material, which poses a structural safety hazard. This refers to the additional stress generated by the bending moment on the overall cross-section of the bridge pier. It reflects the additional stress concentration caused by eccentric loads or lateral forces. The larger the value, the more significant the bending effect, leading to a more uneven stress distribution within the cross-section. Local areas of the bridge pier may experience higher tensile or compressive stresses, increasing the risk of local buckling, cracking, or instability of the structure. It is the ultimate bearing stress of the overall cross section of the bridge pier, which reflects the maximum bearing capacity of the structure under comprehensive stress conditions. The larger the value, the higher the stress the bridge pier cross section can withstand without failure, and the stronger the structure has a higher bearing capacity and a higher safety margin.

[0123] It should be noted that we are using weighting coefficients here. Come to The adjustment is made because the additional stress corresponding to the bending moment has an uneven effect at different locations or cross-sectional angles of the pier; the weighting coefficient... It is used to reflect the non-uniformity and direction dependence of stress distribution caused by bending moment, and can more accurately describe the true stress state of each part of the pier section, thereby improving the calculation accuracy of the comprehensive stability coefficient and the reliability of structural safety assessment. This method is used to adjust the magnitude of the bending moment's influence on stress, taking into account the nonlinear adjustment of the influence of pier wall thickness variations and the ratio of the core region's radius to the overall region's radius on the bending moment. When the value is close to 1, the wall thickness is relatively thin. When the bending moment is smaller, its effect is weakened; when If the wall thickness is relatively small, the influence of bending moment on stress will increase.

[0124] The overall stability of the bridge pier area is judged based on the established comprehensive stability coefficient. If the entire area of ​​the bridge pier meets the stability requirements; if If so, corresponding reinforcement or design optimization measures should be taken to improve structural stability.

[0125] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0126] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0127] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0128] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for evaluating the stability of thick-walled high-strength steel-concrete composite bridge pier foundations, characterized in that, The specific steps include: Step 1: Collect the geometric and material parameters of the steel-concrete composite pier to be analyzed, establish a three-dimensional geometric model of the steel-concrete composite pier based on finite element analysis software, apply simulated loads to the three-dimensional geometric model, and divide the three-dimensional geometric model of the steel-concrete composite pier into the core area of ​​the pier and the steel-concrete composite area based on the stress distribution. Step 2: Based on the modal zoning method, the core area of ​​the bridge pier is divided into several sub-regions. The weak stress locations in each sub-region are screened out according to the stress structure analysis method. The structural parameters of the weak stress locations are calculated to obtain the characteristic parameters related to the stability of the steel-concrete composite bridge pier in each sub-region. Step 3: Normalize the feature parameters of each sub-region, and construct a stability evaluation function for the core region of the pier based on the principle of structural stability evaluation. Evaluate the stability of the core region of the pier based on the constructed stability evaluation function. Step 4: For the steel-concrete composite area on the outer layer of the pier, based on the theory of synergistic mechanics, axial compression analysis and eccentric compression analysis are performed on the steel-concrete composite area with the pier as the core, and the axial ultimate bearing capacity and total normal stress in the cross section of the entire pier area are calculated respectively. Step 5: Calculate the ultimate bearing stress of the pier section in the whole area based on the radius ratio of the core area of ​​the pier to the whole area of ​​the pier. Combine the axial ultimate bearing capacity in the pier section in the whole area with the normalized total normal stress to generate a comprehensive stability coefficient as the stability evaluation standard for steel-concrete composite piers.

2. The method for evaluating the stability of thick-walled high-strength steel-concrete composite bridge pier foundations according to claim 1, characterized in that, A three-dimensional geometric model of a steel-concrete composite bridge pier was established and simulated loads were applied. The three-dimensional geometric model was then divided into regions based on stress distribution. The method used was as follows: The geometric parameters of the steel-concrete composite pier to be analyzed are obtained, including the pier height, wall thickness, and top and bottom diameters. At the same time, the connection dimensions between the pier and the foundation and abutment are obtained, as well as the relevant material parameters, including the elastic modulus, yield strength and Poisson's ratio of the steel pipe, and the elastic modulus, compressive strength and Poisson's ratio of the concrete. A three-dimensional geometric model of a steel-concrete composite pier was established using ANSYS finite element analysis software. The ANSYS workbench was started, the geometry module was selected, and the inner and outer cylinders of the steel pipe were drawn. The steel pipe solid was generated by the "Extrude" command. The concrete filling area solid was drawn according to the design cross-sectional dimensions of the pier, which is the solid filling inside the steel pipe. The connecting parts such as the abutment and foundation were drawn. Boolean operations such as "merge", "intersect" and "shear" were performed to form the three-dimensional geometric model of the steel-concrete composite pier in the initial state. In the ANSYS engineering data module, create material libraries for steel pipes and concrete, accurately input the elastic modulus, Poisson's ratio, yield strength, and compressive strength, and then mesh the model. The specific method is as follows: enter the "Mesh" module, perform reasonable meshing for steel pipes and concrete respectively, use shell elements for steel pipes and solid elements for concrete, and use a dense mesh for the connection area of ​​the model. Apply zero displacement constraints to all degrees of freedom of the relevant nodes at the bottom of the pier to simulate the rigid fixation of the foundation, and simulate the elastic deformation of the foundation through spring elements. Define the spring stiffness in different directions to simulate the interaction between the foundation and the ground. Set the interface between steel pipes and concrete to "bond" condition, that is, the nodes of both are shared and set to no relative slip. Based on the above steps, the final three-dimensional geometric model of the steel-concrete composite pier is obtained. Simulated loads are applied to the model, concrete compressive stress is selected as the key stress index, and a stress discrimination threshold is preset. The average stress level of the main steel-concrete composite area of ​​the entire pier is calculated. The core stress range is determined by combining the set stress discrimination threshold. The core area is separated from the main area using software functions, and the three-dimensional geometric model is divided into the pier core area and the steel-concrete composite area.

3. The method for evaluating the stability of thick-walled high-strength steel-concrete composite bridge pier foundations according to claim 2, characterized in that, The stress-structure analysis method was used to screen out the weak points in each sub-region and obtain the characteristic parameters related to the stability of the bridge piers in each sub-region. The method used was as follows: Based on the modal zoning method, the core area of ​​the bridge pier is divided into the pier main body area, the pier top connection area, and the pier bottom support area. The method for determining the weak points in the pier main body area is as follows: calculate the stress at each section along the pier height, and identify the section corresponding to the location of the maximum normal stress as the weak cross section. Combine this with a finite element stress cloud diagram to confirm the weak cross section as the weak point in the pier main body area. The method for determining the weak points in the pier top connection area is as follows: calculate the local stiffness at different sections of the cap beam, use a finite element model to simulate the stiffness transfer at the connection between the cap beam and the pier, identify areas of abrupt stiffness changes, calculate the maximum local normal stress at the connection, and combine this with the modal zoning method to determine the weak points. The specific locations with large amplitude and low stiffness in the connection area, i.e., the nodes where the cross-sectional stiffness of the connection area between the cap beam and the pier column changes abruptly and stress concentrates, are designated as the weak points in the connection area at the top of the pier column. The method for determining the weak points in the support area at the bottom of the pier column is as follows: calculate the contact area between the foundation cap and the ground, obtain the average contact pressure of the foundation cap in combination with the load, analyze the contact pressure distribution using elastic contact theory, identify the local pressure peak area, and combine the shear force and bending moment in this area to perform superimposed analysis on the stress of the bottom section. Use finite element local refinement to simulate the stress and deformation at the support, and designate the edge area of ​​the contact surface between the cap and the ground as the weak points in the support area at the bottom of the pier column. For the identified weak points in each sub-region, structural parameters are calculated to obtain characteristic parameters related to the stability of the steel-concrete composite piers in each sub-region. The formula used is as follows: in, The geometric efficiency coefficient of the cross section at the weakest point in the main body of the pier column. The area of ​​the weak cross section. The perimeter of the weak cross section. This represents the stiffness coefficient of the cap beam connection node at the weakest point in the connection zone at the top of the pier column. The elastic modulus of the cap beam is given by [the material's elastic modulus]. Let be the second moment of inertia of the section at the connection of the cap beam. This represents the local stress coefficient at the weakest point in the support zone at the bottom of the pier column. This refers to the vertical load at the edge of the contact surface between the foundation cap and the ground. This refers to the bearing area at the edge of the contact surface between the foundation and the ground.

4. The method for evaluating the stability of thick-walled high-strength steel-concrete composite bridge pier foundations according to claim 3, characterized in that, A stability evaluation function for the core area of ​​the bridge pier is constructed to evaluate the stability of the core area of ​​the bridge pier. The method used is as follows: A stability evaluation function for the core area of ​​the bridge pier is constructed by combining the normalized characteristic parameters of each sub-region with the structural stability evaluation principle. The structural stability evaluation principle consists of two parts: the first part is the structural bearing capacity index, which is composed of normalized characteristic parameters characterizing the structural bearing performance. , The first part is constructed using a linear weighting method. The second part is the stress effect index on the structure, which consists of normalized characteristic parameters that characterize the magnitude of stress concentration. The linear weighted average is based on the following formula: in, Indicates the stability of the core area of ​​the bridge pier. , , These are the weighting coefficients of the feature parameters for each sub-region. , , These represent the normalized feature parameters of each sub-region; When the calculation results of the stability evaluation function of the core area of ​​the bridge pier When the calculation result indicates that the core area of ​​the bridge pier is in a stable state, it means that the core area of ​​the bridge pier is in a stable state. This indicates that there is a risk of instability in the core area of ​​the bridge pier.

5. The method for evaluating the stability of thick-walled high-strength steel-concrete composite bridge pier foundations according to claim 4, characterized in that, The method used to calculate the axial ultimate bearing capacity and total normal stress within the overall cross-section of the bridge pier is as follows: Based on the theory of synergistic mechanics, assuming good bonding between the steel pipe and concrete, no relative slippage within the cross-section, and that the axial compressive ultimate bearing capacity of the pier is jointly borne by the steel pipe and concrete, the formula used to calculate the axial ultimate bearing capacity of the entire pier region is as follows: in, This represents the axial ultimate bearing capacity of the entire pier area. , These represent the cross-sectional areas of the steel pipe and the concrete, respectively. Design yield strength for steel pipes, The ultimate axial compressive stress is designed for concrete. This is the resistance coefficient; After determining the eccentricity of the entire pier area, the ultimate bending moment limit of the pier section is calculated based on the fundamental conditions of synergistic mechanics theory. The formula used is as follows: in, Indicates the eccentricity of the entire area of ​​the bridge pier. This represents the ultimate bending moment that the bridge pier section can withstand. The total normal stress within the cross-section of the bridge pier is mainly composed of the uniform normal stress generated by axial pressure and the additional stress generated by bending moment, based on the following formula: in, This represents the total normal stress within the cross-section of the entire pier region. This represents the cross-sectional area of ​​the entire bridge pier area. This represents the perpendicular distance from the edge point of the cross-section to the neutral axis of the cross-section, and The sign is used to distinguish the vertical position of the cross-section. Let be the moment of inertia of the cross section about the neutral axis.

6. The method for evaluating the stability of thick-walled high-strength steel-concrete composite bridge pier foundations according to claim 5, characterized in that, The ultimate bearing stress of the pier section in the entire pier region is calculated based on the radius ratio of the pier core area to the pier overall region, and a comprehensive stability coefficient is generated to evaluate the overall stability of the pier. The method used is as follows: The radius ratio is defined as the ratio of the radius of the core area of ​​the pier to the outer diameter of the entire pier area, based on the following formula: in, This represents the ratio of the radius of the core area of ​​the bridge pier to the radius of the entire bridge pier area. The radius of the core area of ​​the bridge pier. The outer diameter of the entire pier area; Based on the synergistic load-bearing contribution of the steel pipe and the core concrete, and combined with the radius ratio, the ultimate bearing stress of the section is calculated using the following formula: in, This represents the ultimate bearing stress of the cross-section in the entire region of the bridge pier; The axial stress parameter is normalized based on the uniform normal stress generated by the axial pressure acting on the entire cross-section of the bridge pier, and the bending moment stress parameter is normalized based on the additional stress caused by the bending moment acting on the entire cross-section of the bridge pier. The formula used is as follows: in, This represents the axial stress parameters of the entire cross-section of the bridge pier. The bending moment and stress parameters represent the overall cross-section of the bridge pier. Based on the calculated ultimate bearing stress of the cross section in the overall region of the pier, a comprehensive stability coefficient is established by combining the axial ultimate bearing capacity and the normalized total normal stress within the cross section of the overall region of the pier. The influence of axial and bending moment stresses is comprehensively considered, and a weighting factor is adopted. The formula used to reflect the adjusting effect of bending moment on force is: in, This represents the comprehensive stability coefficient used to characterize the overall regional stability of the bridge pier. , These are empirical parameters that reflect the nonlinear adjustment of the effect of changes in pier wall thickness on bending moment. The overall stability of the bridge pier area is judged based on the established comprehensive stability coefficient. If the entire area of ​​the bridge pier meets the stability requirements; if If so, corresponding reinforcement or design optimization measures should be taken to improve structural stability.

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