Design method of special-shaped large-section circular prestressed beams based on finite element model

Abstract

The present invention discloses a design method for special-shaped large-section annular prestressed beams based on a finite element model, and relates to the field of civil engineering technology. In order to solve the problem that the symmetrical arrangement of the special-shaped ring beam for tensioning will cause uneven local stress, which may cause local concrete cracking and affect the stability of the overall structure; the present invention uses a finite element model and finite element analysis technology, combined with the specific stress characteristics of the special-shaped large-section ring beam, to achieve an optimized arrangement of prestressed tendons, ensuring the uniformity and stability of the structure. The asymmetric arrangement of prestressed tendons can be flexibly adjusted according to the needs of the specific project, so that the tension value of the cross section is consistent, so that the integrity of the tensioned ring beam is better, and the construction accuracy and economy of the structure are improved. Moreover, through the application of step-by-step construction and life-and-death unit technology, the risks in the construction process are effectively reduced, and the construction efficiency and structural safety are improved.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering, in particular to a design method of a special-shaped large-section annular prestressed beam based on a finite element model. Background Art

[0002] The main function of the large ring beam is to transfer the roof load to the columns. The large ring beam is generally a perfect circle with a parallelogram cross-section with an inner curved surface. It mainly serves as the load-bearing member of the overall roof structure. However, in the existing technology, the beam-column joints are densely packed with steel bars and are complexly interwoven. The ring beams, columns, roof cross beams, and prestressed steel strand tubes are interspersed at the same time. The diameter of the longitudinal bars and stirrups in the ring beams is large. The layout of the prestressing force must avoid areas with dense steel bars and meet the overall tensile stress requirements. This makes the design of the prestressing force arrangement for large-section annular prestressed concrete structural beams with special shapes difficult. The traditional symmetrical arrangement method cannot meet the load requirements of special-section beams, which can easily cause localized uneven load and concrete cracking, affecting the stability of the structure. Summary of the Invention

[0003] The purpose of the present invention is to provide a design method for special-shaped large-section annular prestressed beams based on a finite element model. By establishing a finite element model for finite element calculation and adopting an asymmetric prestressing arrangement according to the characteristics of the special-shaped section, it is ensured that the prestressing meets the design requirements and that the tensioning is feasible, so as to solve the problems raised in the above-mentioned background technology.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] The design method of the special-shaped large-section annular prestressed beam based on the finite element model includes the following steps:

[0006] Step 1: Divide the construction sections: Obtain the actual conditions of the construction site, determine the basic geometric parameters and material properties of the ring beam, determine a layout plan for the ring beam based on the basic geometric parameters and material properties of the ring beam, and divide the entire ring beam into several construction sections based on the layout plan;

[0007] Step 2: Establishing a finite element model: Establishing a finite element model of the ring beam based on its basic geometric parameters and material properties. The finite element model uses birth-death element technology to simulate the different structural states of each construction section.

[0008] Step 3: Finite element calculation: Based on the finite element model, simulate the prestressed tendon tensioning and post-casting joint needle reinforcement tensioning process, calculate the stress, displacement and internal force distribution of the ring beam at each stage, and make optimization adjustments based on the calculation results;

[0009] Step 4: Determine the distribution of prestressed tendons: Analyze the stress distribution in the ring beam after tensioning, adjust the distribution of prestressed tendons based on the tensioning analysis results, and adopt an asymmetric prestressing arrangement;

[0010] Step 5: Design verification and construction plan optimization: Based on the calculation results, a comprehensive analysis is conducted on the prestressed reinforcement layout plan, construction section division and construction technology, and the construction plan is optimized based on the comprehensive analysis results.

[0011] Furthermore, the division of the construction sections specifically includes:

[0012] Based on the geometric parameters of the ring beam and the actual conditions of the construction site, the layout design of the ring beam is carried out to determine the prestressed reinforcement layout, construction sequence, support and connection methods of the ring beam;

[0013] Determine the ring beam segmentation plan based on the construction environment and construction schedule, including the length, load characteristics and coordination between each construction segment;

[0014] Based on the geometric characteristics of the ring beam and the tensioning requirements of the prestressed tendons, the construction sections are divided into detailed sections, and the construction nodes and key processes of each section are determined;

[0015] Set the corresponding operation sequence and duration for each construction node, clarify the construction progress of each construction section, the connection time of key processes and the required material transportation cycle.

[0016] Furthermore, step 2: establishing a finite element model, specifically including:

[0017] Extract the three-dimensional geometric information of the ring beam and determine the mechanical performance parameters of the ring beam based on the material properties of the ring beam;

[0018] Input the three-dimensional geometric information of the ring beam into a three-dimensional modeling tool to construct a three-dimensional geometric model of the ring beam, and set mechanical properties for each part of the ring beam based on the mechanical performance parameters of the ring beam;

[0019] Set up life and death units for each ring beam structure, determine the specific structural state of each structure in different construction sections, and simulate the mechanical behavior of each construction section of the ring beam based on the specific structural state of each structure in different construction sections;

[0020] Among them, each construction section activates or kills the corresponding units according to the actual construction progress and scheduled construction nodes, and dynamically adjusts the construction process and the specific structural status of each structure in the finite element model.

[0021] Furthermore, the finite element model further includes:

[0022] According to the mechanical behavior of each construction section of the ring beam and the actual construction conditions, the position of the support point, the support type and the support reaction force are set, the constraint conditions of the support are determined, and the contact relationship between the various structures of the ring beam is set;

[0023] In each construction section, loads are applied to the ring beam according to the construction process to simulate the stress state of the ring beam in different construction sections. The load application method for each construction section is determined based on the actual construction conditions, and the load changes over time are modeled.

[0024] Furthermore, the construction process and the specific structural status of each structure in the finite element model are dynamically adjusted, including:

[0025] Monitor the load, deformation, and stress changes of each construction section in real time, and adjust the structural status according to predetermined rules at the end of each construction cycle;

[0026] At the end of the monitoring period, obtain the magnitude of changes in various types of data within the current detection period and determine the type of data with the largest change;

[0027] Determine the target data type that needs to be adjusted in the next cycle based on the data change magnitude assessment results. At the same time, adjust the frequency of data collection based on changes in load and mechanical behavior during the construction process.

[0028] The specific structural status of each structure in the finite element model is adjusted according to the construction progress and load changes. At the same time, it is dynamically updated according to the material mechanical properties in the model.

[0029] Further, finite element calculations specifically include:

[0030] Stress analysis: For each construction section, calculate the distribution of hoop stress, axial stress, shear stress and bending stress of the ring beam;

[0031] Deformation analysis: The displacement and deformation of the ring beam at each construction stage are calculated using a finite element model, with a focus on analyzing whether the structural deformation meets the design requirements and whether there is a risk of excessive deformation.

[0032] Crack development prediction: Based on stress analysis and deformation analysis, the finite element model is used to simulate the location, shape and expansion trend of possible cracks in the ring beam;

[0033] Analysis of the internal force distribution of the ring beam at each stage: During the finite element model simulation process, the internal force distribution of the ring beam at each construction stage is calculated, and the distribution of stress, displacement and internal force of the ring beam is determined based on the calculation results.

[0034] Furthermore, determining the distribution of prestressed tendons also includes:

[0035] Analyze the stress distribution of each construction section of the ring beam. During the prestressing tendon tensioning stage, analyze the axial stress, bending stress, and shear stress in each area.

[0036] Based on the simulation results of the finite element model, the stress concentration characteristics in the ring beam are identified and the key areas for prestressing reinforcement arrangement are determined;

[0037] Based on the stress analysis results of the ring beam, the appropriate number and layout of prestressed tendons are determined. The number of prestressed tendons can be increased in areas with concentrated stress, and the arrangement of prestressed tendons can be reduced in areas with low stress.

[0038] According to the stress requirements of the special-shaped section and the stress conditions at different positions of the ring beam, combined with the construction section division of the ring beam, the layout angle, quantity and distribution form of the prestressed tendons are adjusted.

[0039] Furthermore, a comprehensive analysis of the prestressed reinforcement arrangement scheme, construction section division and construction technology is conducted, including:

[0040] Conduct a comprehensive assessment of prestressed reinforcement layout, construction section division, and construction technology to ensure that the adjusted prestressed reinforcement layout, construction section division, and construction technology meet the design requirements. Based on the comprehensive assessment results, conduct a risk assessment during the construction process, propose corresponding emergency plans, and match corresponding corrective measures according to the risk characteristics of different construction stages.

[0041] Furthermore, the establishment of the finite element model specifically includes:

[0042] A hybrid grid combining structured and unstructured grids is used for finite element basic division. The structured grid is given priority. The regular parts of the large-section annular prestressed beam are divided by structured grids, while the irregular parts at the edges are divided by unstructured grids. By using different types of grids in different areas, it is adapted to the special-shaped structure of the large-section annular prestressed beam.

[0043] Based on the basic theory of structural stress, the key stress-bearing areas of large-section annular prestressed beams were preliminarily determined, including stress concentration areas, areas with large deformation, and areas where boundary conditions act. Mesh density was then refined for these key stress-bearing areas. A transition area for mesh density change was formed between the mesh refinement area and the finite element basic division to ensure a smooth transition of mesh density.

[0044] The boundary fitting technology is used to make the boundary of the finite distance grid unit match the boundary of the actual large cross-section annular prestressed beam as closely as possible;

[0045] Implement finite element simulation analysis, automatically perform adaptive optimization and adjustment of the grid based on the error estimation of the simulation analysis calculation results, or the stress and deformation changes as physical quantities, and finally form an optimized finite element model.

[0046] Furthermore, the implementation of finite element simulation analysis includes using a genetic algorithm to perform simulation analysis, as follows:

[0047] Randomly generate a set of initial populations within the range of the design variables, and ensure that the initial population has a certain degree of diversity;

[0048] Constructing a fitness function , determine the objective function of the fitness function optimization, the objective function involves the performance index of the structure, including minimizing stress, deformation and weight, or maximizing stiffness and stability;

[0049] The constraints of the design variables are incorporated into the fitness function. The constraints include the upper and lower limits of the design variables, the strength and stability requirements of the structure, and the penalty function method is used to transform the constraints into part of the fitness function. That is, when the constraints are violated, the fitness value is penalized to reduce the fitness value.

[0050] According to the fitness value of individuals in the initial population, the selection probability of individuals is calculated using the following formula:

[0051]

[0052] in, Indicates the number of the initial population The probability of selection of an individual; Indicates the number of the initial population The fitness value of each individual; Indicates the number of individuals contained in the initial population; Indicates the number of the initial population The fitness value of each individual;

[0053] Set the crossover probability, mutation probability, and iteration termination condition. In each iteration, perform fitness selection, multi-point crossover, and Gaussian mutation operations to generate a new population and calculate the fitness value of the new population. Evaluate and select the new population based on the fitness value, eliminate individuals with low fitness, and retain individuals with high fitness until the termination condition is met, thus obtaining the optimal solution of the genetic algorithm.

[0054] After the above genetic algorithm simulation analysis, the optimal solution of the genetic algorithm is substituted into the finite element model for verification to check whether all design requirements and constraints are met. If not, the design optimization of the special-shaped large-section annular prestressed beam is carried out, and after optimization, the finite element division, simulation analysis and verification are re-performed until all design requirements and constraints are met.

[0055] Furthermore, the grid encryption is specifically as follows:

[0056] Obtain finite element force analysis data under various grid density division conditions and the corresponding force analysis accuracy data;

[0057] Obtain the stress limit data of concrete with different steel bar configurations at different ambient temperatures, taking the ambient temperature as The stress limit data of concrete with different steel bar configurations at different ambient temperatures is used as the basis to determine the stress limit data of concrete with different steel bar configurations at different ambient temperatures to be converted into the ambient temperature of Temperature influence coefficient of the stress limit data at ;

[0058] Based on the stress theory of prestressed beams, stress analysis was performed on different parts of the special-shaped large-section circular prestressed beams to obtain theoretical stress data for each part, including theoretical stress data for key stress-bearing areas. In combination with the accuracy requirements for the design of special-shaped large-section circular prestressed beams, the mesh refinement coefficient for key stress-bearing areas was calculated using the following formula:

[0059]

[0060] in, is the mesh density factor of the stressed area, The finite element mesh density is the theoretical stress data of the stress-focused area when the corresponding stress analysis accuracy data is equal to the design accuracy requirement. In order to ensure that the force analysis accuracy data is equal to the design accuracy requirements, the finite element mesh density corresponding to the non-stress key focus area and non-transition area is The ambient temperature of the special-shaped large-section annular prestressed beam for finite element analysis Corresponding temperature influence coefficient;

[0061] Perform style encryption on the stress-focused area according to the calculated mesh encryption coefficient, and perform finite element stress analysis. If the deviation between the stress data of the stress-focused area obtained by analysis and the theoretical stress data exceeds a set value, the stress data obtained by analysis of the stress-focused area will replace the theoretical stress data. Repeat the above steps, and iterate the calculation until the deviation between the stress data of the stress-focused area obtained by analysis and the theoretical stress data does not exceed a set value.

[0062] The mesh encryption coefficient of the stress-sensitive area is calculated for the last time using the above iterative calculation, and the finite element mesh is encrypted for the stress-sensitive area.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] Through finite element model and finite element analysis technology, combined with the specific stress characteristics of special-shaped large-section ring beams, the optimal arrangement of prestressed tendons is achieved to ensure the uniformity and stability of the structure. The asymmetric prestressed tendon arrangement can be flexibly adjusted according to the needs of the specific project, so that the tension values ​​of the cross-section are consistent, thereby solving the problem of inconsistent tension values ​​caused by special-section ring beams, which leads to cracks in the concrete. The tensioned ring beam has better integrity, which improves the construction accuracy and economy of the structure. Through the application of step-by-step construction and life-and-death unit technology, the risks in the construction process are effectively reduced, and the construction efficiency and structural safety are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 A diagram showing the steps of a design method for a special-shaped large-section annular prestressed beam based on a finite element model of the present invention;

[0066] Figure 2 It is a top view geometric diagram of the overall structure of the ring beam of the present invention;

[0067] Figure 3 Schematic diagram of the finite element model of the ring beam of the present invention;

[0068] Figure 4 This is a schematic diagram of the hoop stress in the cross section of the ring beam of the present invention;

[0069] Figure 5 This is a schematic diagram of the arrangement position of the prestressed tendons of the present invention. DETAILED DESCRIPTION

[0070] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0071] In order to solve the technical problem that the symmetrical arrangement of special-shaped ring beams will cause uneven local stress, which may cause local concrete cracking and affect the stability of the overall structure, please refer to Figure 1-Figure 5 , this embodiment provides the following technical solutions:

[0072] The design method of the special-shaped large-section annular prestressed beam based on the finite element model includes the following steps:

[0073] Step 1: Divide the construction sections: Obtain the actual construction site conditions, including the location of the ring beam, the geometry of the construction site, the surrounding environmental conditions, the layout of the structural columns and support system, etc., determine the basic geometric parameters and material properties of the ring beam, and then determine the layout plan of the ring beam based on the basic geometric parameters and material properties of the ring beam. Based on the layout plan, divide the entire ring beam into several construction sections, specifically including:

[0074] Based on the geometric parameters of the ring beam and the actual conditions of the construction site, the layout design of the ring beam is carried out to determine the prestressed reinforcement layout, construction sequence, support and connection methods of the ring beam;

[0075] Determine the ring beam segmentation plan based on the construction environment and construction schedule, including the length, load characteristics and coordination between each construction segment;

[0076] Based on the geometric characteristics of the ring beam and the requirements for prestressed tendon tensioning, the construction sections were divided into detailed sections, and the construction nodes and key processes for each section were determined, such as the specific steps and sequence for prestressed tendon tensioning, concrete pouring, and seam reinforcement tensioning.

[0077] Set the corresponding operation sequence and duration for each construction node, clarify the construction progress of each construction section, the connection time of key processes and the required material transportation cycle;

[0078] Step 2: Establish a finite element model: Based on the basic geometric parameters and material properties of the ring beam, a finite element model of the ring beam is established, including the ring beam structure, prestressed tendons, seam reinforcement, and supports. The finite element model uses birth-death element technology to simulate the different structural states of each construction section, clarify the design requirements, including horizontal tension and precompression stress values, and verify them through finite element calculation results;

[0079] Step 3: Finite element calculation: Based on the finite element model, simulate the tensioning process of prestressed tendons and post-cast strip seam reinforcement, including prestressed tendon tensioning and post-cast strip seam reinforcement tensioning, observe the stress, deformation and crack development in the ring beam, calculate the stress, displacement and internal force distribution of the ring beam at each stage, evaluate the effect of prestressed tendons and seam reinforcement, and make optimization adjustments based on the calculation results to avoid problems such as local overload, excessive deformation or uneven structural stress;

[0080] Step 4: Determine the distribution of prestressed tendons: Analyze the stress distribution within the ring beam after tensioning, including the axial stress, bending stress, and shear stress on the ring beam cross section. Adjust the distribution of prestressed tendons based on the tensioning analysis results, and adopt an asymmetric prestressing arrangement. The asymmetric prestressing arrangement is adjusted according to the force requirements of the special-shaped cross-section beam to ensure that each part is subjected to uniform tension.

[0081] Step 5: Design verification and construction plan optimization: Based on the calculation results, a comprehensive analysis is conducted on the prestressed reinforcement layout plan, construction section division and construction technology, and the construction plan is optimized based on the comprehensive analysis results.

[0082] In this example, the ring beam is divided into 12 construction sections based on the on-site arrangement of the ring beam and structural columns. Finite element models of the prestressed tendons, seam reinforcement, concrete ring beam, and columns within the ring beam are established. The design requirements are: the horizontal tensile design value is 120,000 kN, and the precompressive stress is not less than 4.3 MPa. Finite element calculations are performed using Abaqus software.

[0083] The life and death unit is used to realize step-by-step construction, and the prestressed tendons in the ring beam are tensioned to kill the concrete of the post-cast zone; the concrete of the post-cast zone is activated to tension the seam needle tendons; after the prestressed tendons are tensioned, the circumferential compressive stress of the ring beam concrete is 3.1-9.8MPa; the overall circumferential stress is about 5.5MPa; the first principal stress of the ring beam concrete is 0.4-0.7MPa; the overall stress level is about 0.2MPa; after the seam needle tendons are tensioned, the circumferential compressive stress of the post-cast zone section is 3.6-6.2MPa, and the overall stress level is about 5.5MPa. The first principal compressive stress of the section is 0.3-0.18 MPa, the minimum stress is located in the middle area of ​​the section, and the overall stress level is about 0.07 MPa; after the overall tensioning is completed, the overall stress of the prestressed tendons in the ring beam is about 880 MPa; the internal force of the concrete ring beam section is about 126,000 kN; the overall stress of the seam needle reinforcement is about 920 MPa; the compressive stress result is >4.3 MPa, and the axial force 126,000 KN>120,000 KN, which meets the design requirements; thereby determining the arrangement position of the prestressed tendons.

[0084] In this embodiment, step 2: establishing a finite element model, specifically includes:

[0085] Extract the 3D geometric information of the ring beam, including its complex, irregular cross-section, and determine the mechanical performance parameters of the ring beam based on its material properties;

[0086] Input the 3D geometric information of the ring beam into a 3D modeling tool to construct a 3D geometric model of the ring beam, including the ring beam's shape, the layout of the prestressed tendons, the layout of the seam pins, the location of the supports, and the relationship between the structural columns. This accurately expresses the structural characteristics of the ring beam, including the geometric changes in each construction section, and prepares for subsequent finite element analysis. Based on the mechanical performance parameters of the ring beam, mechanical properties are set for each component of the ring beam, including elastic modulus, Poisson's ratio, density, tensile and compressive strength, etc., to ensure that these mechanical properties can reflect the deformation and stress response of each material in different construction sections.

[0087] In this embodiment, a stress-strain curve model (e.g., a nonlinear model) suitable for large-section beams is used for concrete to simulate its behavior under different stress states (including effects such as yielding, failure, and shrinkage). Elastic-plastic or ideal elastic models suitable for prestressed tendons and stitching are used to ensure that the mechanical properties of these materials (e.g., elastic modulus, yield strength, etc.) are consistent with those used in actual projects.

[0088] Set up life and death units for each ring beam structure, determine the specific structural state of each structure in different construction sections, and simulate the mechanical behavior of each construction section of the ring beam based on the specific structural state of each structure in different construction sections;

[0089] Among them, each construction section activates or kills the corresponding units according to the actual construction progress and scheduled construction nodes, and dynamically adjusts the construction process and the specific structural status of each structure in the finite element model. For example, in the stage of tensioning prestressed tendons, the prestressed tendon units are activated and the post-cast concrete units are killed.

[0090] In this embodiment, the construction process and the specific structural state of each structure in the finite element model are dynamically adjusted, specifically including:

[0091] Monitor the load, deformation, and stress changes of each construction section in real time, and adjust the structural status according to predetermined rules at the end of each construction cycle;

[0092] At the end of the monitoring period, the change amplitude of various data within the current detection period is obtained, such as the increase in tension load, the hardening speed of concrete, etc., and the data type with the largest change is determined;

[0093] Based on the data change magnitude assessment results, determine the target data types that need to be adjusted in the next cycle. For example, if the stress variation during the prestressing tendon tensioning stage is too large, the tensioning rate may need to be adjusted, or the tensioning time may need to be appropriately extended in the next cycle. At the same time, the frequency of data collection can be adjusted based on changes in load and mechanical behavior during construction. For example, if the stress in a certain construction section changes dramatically, the monitoring period may need to be shortened and the data collection frequency increased to ensure timely detection of structural anomalies.

[0094] The specific structural status of each structure in the finite element model is adjusted according to the construction progress and load changes, including dynamically activating or deactivating different structural units at the end of each construction cycle, adjusting supports and boundary conditions according to changes in the stress state of the ring beam, etc. At the same time, dynamic updates are performed based on the material mechanical properties in the model. For example, after the concrete pouring is completed, the strength of the concrete will gradually increase, so the mechanical properties of the concrete need to be updated according to the actual strength changes.

[0095] In this embodiment, the finite element model and dynamic adjustment technology are combined to accurately simulate the mechanical behavior of each stage in the construction process, adjust the construction process and the status of each structure according to real-time monitoring data, and ensure that all adjustments meet the needs of the actual project, thereby ensuring the flexibility and adaptability of the construction process, effectively optimizing the construction progress, improving structural stability and reducing construction risks.

[0096] In this embodiment, the finite element model further includes:

[0097] According to the mechanical behavior of each construction section of the ring beam and the actual construction conditions, the position of the support points, the support type (such as hinged support, fixed support, etc.) and the support reaction force are set, the constraint conditions of the support are determined, the deformation and mechanical behavior of the ring beam during the simulation are consistent with the actual project, and the contact relationship between the various structures of the ring beam is set;

[0098] In each construction section, loads are applied to the ring beam according to the construction process, such as the deadweight of concrete, construction loads, and tension loads of prestressed tendons. The stress state of the ring beam under different construction sections is simulated. The load application method for each construction section is determined based on the actual construction conditions, and the change of load over time is modeled.

[0099] In this embodiment, the finite element model can accurately reflect the deformation of the ring beam at different construction stages, ensuring that the constraints in the model match the support system in the actual project, thereby making the simulation results more realistic and better able to predict and control the mechanical behavior of the ring beam during the construction process. According to the actual conditions of different construction stages, the application methods of concrete deadweight, construction load, prestressed tendon tensioning load, etc. are simulated, and the change of load over time is taken into account. It can more realistically reflect the actual order and method of load application during the construction process, avoid structural abnormalities caused by improper load application, improve the safety and stability of the construction process, and improve construction efficiency and quality control.

[0100] In this embodiment, the finite element calculation specifically includes:

[0101] Stress analysis: For each construction section, such as during the tensioning of prestressed and stitched reinforcement, the distribution of hoop stress, axial stress, shear stress, and bending stress in the ring beam is calculated to evaluate the effectiveness of the prestressed and stitched reinforcement to determine whether they can effectively reduce stress concentration and ensure structural safety.

[0102] In this embodiment, the prestressed tendon tensioning is performed: during the prestressed tendon tensioning process, the tensioning force applied by the prestressed tendon is simulated by a finite element model, and the tensioning steps of different construction sections are simulated, and the load is applied step by step. The load application process of each tensioning section takes into account the initial stress of the prestressed tendon, the subsequent increase in tensioning force, and the tensioning adjustment during construction; the post-cast strip seam needle reinforcement tensioning is performed: in the post-cast strip construction section, the post-cast strip seam needle reinforcement tensioning process after the concrete pouring is completed is simulated by a finite element model, the tensioning force is applied step by step, and the stress distribution and deformation of the structure at this stage are observed;

[0103] Deformation analysis: The displacement and deformation of the ring beam at each construction stage are calculated using a finite element model, with a focus on analyzing whether the structural deformation meets the design requirements and whether there is a risk of excessive deformation.

[0104] Crack development prediction: Based on stress and deformation analysis, the finite element model is used to simulate the location, morphology, and expansion trend of cracks that may occur in the ring beam. In particular, during the tensioning of prestressed tendons or seam pins, the system monitors whether cracks are excessively expanding and predicts possible crack development trends.

[0105] Analysis of the internal force distribution of the ring beam at each stage: During the finite element model simulation process, the internal force distribution of the ring beam at each construction stage is calculated. Based on the calculation results, the distribution of stress, displacement and internal force of the ring beam is determined. For example, the effect of the prestressed steel bars and seam reinforcements at each construction stage is evaluated to analyze whether they can effectively balance the overall internal force of the ring beam and avoid local overload or mechanical unevenness.

[0106] In this embodiment, determining the distribution of prestressed tendons further includes:

[0107] Analyze the stress distribution of each construction section of the ring beam. During the prestressing tendon tensioning stage, analyze the axial stress, bending stress, and shear stress in each area.

[0108] Based on the simulation results of the finite element model, the stress concentration characteristics in the ring beam are identified and the key areas for prestressing reinforcement arrangement are determined;

[0109] Based on the stress analysis results of the ring beam, determine the appropriate number and layout of prestressed tendons. Increase the number of tendons in areas of concentrated stress to ensure stress balance and reduce the risk of local overload. Reduce the number of tendons in low-stress areas to avoid material waste.

[0110] According to the stress requirements of the special-shaped cross-section and the stress conditions at different positions of the ring beam, combined with the division of the ring beam's construction sections, the layout angle, quantity and distribution of the prestressed tendons are adjusted to ensure that the stress in each construction section is uniform and meets the design requirements. It is also ensured that the effect of the prestressed tendons can be fully exerted during the tensioning process of each construction section. The stress and displacement characteristics of different construction sections need to be coordinated with the layout of the prestressed tendons to avoid local stress concentration or excessive deformation during the construction process.

[0111] In this embodiment, by analyzing the stress of the ring beam at each construction stage, the effects of the prestressed tendons and the seam needle tendons can be evaluated to ensure that they effectively reduce stress concentration and ensure structural safety. During the prestressed tendon tensioning process, the applied tensioning force and its gradual increase are simulated by the finite element model. Taking into account the initial stress of the prestressed tendons and the changes in the subsequent tensioning force, the load application process of each construction section is accurately simulated. In the post-casting strip seam needle tendon tensioning stage, dynamic monitoring and stress distribution analysis are also performed to ensure that the structural deformation at each stage meets the design requirements and prevent excessive deformation. In terms of crack development prediction, through stress and deformation analysis, the location, morphology and expansion trend of cracks that may appear in the ring beam can be identified, providing a basis for subsequent repair and prevention. Ensure that each construction section is evenly stressed to avoid local stress concentration or excessive deformation during construction, thereby improving construction efficiency and the safety and stability of the structure.

[0112] In this embodiment, a comprehensive analysis of the prestressed tendon arrangement scheme, construction section division, and construction technology is conducted, which also includes:

[0113] Conduct a comprehensive assessment of prestressed reinforcement layout, construction segmentation, and construction technology to ensure that the adjusted prestressed reinforcement layout, construction segmentation, and construction technology meet design requirements. Based on the comprehensive assessment results, conduct a risk assessment during the construction process, such as uneven prestressed reinforcement tensioning, concrete cracks, and other issues. Propose corresponding emergency plans and match corresponding corrective measures based on the risk characteristics of different construction stages to ensure rapid response in emergencies and smooth construction.

[0114] In this embodiment, the length of each construction section, the construction sequence, the order of prestressing tendon tensioning, and the timing of construction load application all need to be rationally arranged based on the deformation and mechanical behavior of the ring beam. When dividing the construction sections, the stress characteristics of each section, their coordination, and the feasibility of the construction schedule are comprehensively considered to ensure continuous and efficient construction. This ensures that the prestressing tendon layout, construction section division, and construction process are fully optimized, and guarantees the stability and safety of the structure during construction.

[0115] On the basis of the above-mentioned embodiment, the establishment of the finite element model specifically includes:

[0116] A hybrid grid combining structured and unstructured grids is used for finite element basic division. The structured grid is given priority. The regular parts of the large-section annular prestressed beam are divided by structured grids, while the irregular parts at the edges are divided by unstructured grids. By using different types of grids in different areas, it is adapted to the special-shaped structure of the large-section annular prestressed beam.

[0117] Based on the basic theory of structural stress, the key stress-bearing areas of large-section annular prestressed beams were preliminarily determined, including stress concentration areas, areas with large deformation, and areas where boundary conditions act. Mesh density was then refined for these key stress-bearing areas. A transition area for mesh density change was formed between the mesh refinement area and the finite element basic division to ensure a smooth transition of mesh density.

[0118] The boundary fitting technology is used to make the boundary of the finite distance grid unit match the boundary of the actual large cross-section annular prestressed beam as closely as possible;

[0119] Implement finite element simulation analysis, automatically perform adaptive optimization and adjustment of the grid based on the error estimation of the simulation analysis calculation results, or the stress and deformation changes as physical quantities, and finally form an optimized finite element model.

[0120] In this embodiment, by combining structured grids and unstructured grids, boundary fitting technology is used in the unstructured grid part, so that the boundaries of the finite distance grid units are made to match the boundaries of the actual large-section annular prestressed beams as closely as possible, thereby improving the flexibility and adaptability of the grid division, so that the finite element grid division can better fit the special shape of the large-section annular prestressed beams, avoiding the increase in analysis complexity caused by the use of all unstructured grids, and taking into account the balance between the amount of analysis and accuracy; by locally enlarging the grid in key parts, the accuracy is further improved without excessively increasing the amount of calculation, thereby ensuring calculation efficiency; by setting a transition area from the encrypted area to the basic division part to ensure a smooth transition of the grid density from high to low, numerical errors and calculation non-convergence problems caused by sudden changes in grid size are avoided; through finite element simulation analysis, adaptive optimization adjustment of the grid is automatically implemented.

[0121] Based on the above embodiment, the finite element simulation analysis includes using a genetic algorithm to perform simulation analysis, as follows:

[0122] Randomly generate a set of initial populations within the range of the design variables, and ensure that the initial population has a certain degree of diversity;

[0123] Constructing a fitness function , determine the objective function of the fitness function optimization, the objective function involves the performance index of the structure, including minimizing stress, deformation and weight, or maximizing stiffness and stability;

[0124] The constraints of the design variables are incorporated into the fitness function. The constraints include the upper and lower limits of the design variables, the strength and stability requirements of the structure, and the penalty function method is used to transform the constraints into part of the fitness function. That is, when the constraints are violated, the fitness value is penalized to reduce the fitness value.

[0125] According to the fitness value of individuals in the initial population, the selection probability of individuals is calculated using the following formula:

[0126]

[0127] in, Indicates the number of the initial population The probability of selection of an individual; Indicates the number of the initial population The fitness value of each individual; Indicates the number of individuals contained in the initial population; Indicates the number of the initial population The fitness value of each individual;

[0128] Set the crossover probability, mutation probability, and iteration termination condition. In each iteration, perform fitness selection, multi-point crossover, and Gaussian mutation operations to generate a new population and calculate the fitness value of the new population. Evaluate and select the new population based on the fitness value, eliminate individuals with low fitness, and retain individuals with high fitness until the termination condition is met, thus obtaining the optimal solution of the genetic algorithm.

[0129] After the above genetic algorithm simulation analysis, the optimal solution of the genetic algorithm is substituted into the finite element model for verification to check whether all design requirements and constraints are met. If not, the design optimization of the special-shaped large-section annular prestressed beam is carried out, and after optimization, the finite element division, simulation analysis and verification are re-performed until all design requirements and constraints are met.

[0130] In this embodiment, by using a genetic algorithm for simulation analysis, low fitness is eliminated through iterative execution of fitness selection, multi-point crossover and Gaussian mutation operations, and the optimal solution is obtained, thereby achieving further optimization of the finite element analysis. The algorithm formula used is simple and suitable for promotion, which not only achieves a balance between accuracy and computational efficiency, improves the reliability and stability of the optimization results, but also can apply the optimized design variables to actual engineering design, guide the manufacture and construction of the structure, and improve the performance and economy of the project.

[0131] Based on the above embodiment, the grid encryption is specifically as follows:

[0132] Obtain finite element force analysis data under various grid density division conditions and the corresponding force analysis accuracy data;

[0133] Obtain the stress limit data of concrete with different steel bar configurations at different ambient temperatures, taking the ambient temperature as The stress limit data of concrete with different steel bar configurations at different ambient temperatures is used as the basis to determine the stress limit data of concrete with different steel bar configurations at different ambient temperatures to be converted into the ambient temperature of Temperature influence coefficient of the stress limit data at ;

[0134] Based on the stress theory of prestressed beams, stress analysis was performed on different parts of the special-shaped large-section circular prestressed beams to obtain theoretical stress data for each part, including theoretical stress data for key stress-bearing areas. In combination with the accuracy requirements for the design of special-shaped large-section circular prestressed beams, the mesh refinement coefficient for key stress-bearing areas was calculated using the following formula:

[0135]

[0136] in, is the mesh density factor of the stressed area, The finite element mesh density is the theoretical stress data of the stress-focused area when the corresponding stress analysis accuracy data is equal to the design accuracy requirement. In order to ensure that the force analysis accuracy data is equal to the design accuracy requirements, the finite element mesh density corresponding to the non-stress key focus area and non-transition area is The ambient temperature of the special-shaped large-section annular prestressed beam for finite element analysis Corresponding temperature influence coefficient;

[0137] Perform style encryption on the stress-focused area according to the calculated mesh encryption coefficient, and perform finite element stress analysis. If the deviation between the stress data of the stress-focused area obtained by analysis and the theoretical stress data exceeds a set value, the stress data obtained by analysis of the stress-focused area will replace the theoretical stress data. Repeat the above steps, and iterate the calculation until the deviation between the stress data of the stress-focused area obtained by analysis and the theoretical stress data does not exceed a set value.

[0138] The mesh encryption coefficient of the stress-sensitive area is calculated for the last time using the above iterative calculation, and the finite element mesh is encrypted for the stress-sensitive area.

[0139] In this embodiment, finite element force analysis data and corresponding force analysis accuracy data under various grid density division conditions can be obtained through experiments or network searches, which serve as basic data for the grid density that should be used to query the corresponding finite element force analysis data according to the accuracy requirements; based on the theoretical force analysis, the forces at different parts of the beam are obtained, combined with the project accuracy requirements, and considering the influence of ambient temperature, the above formula is used to calculate the grid encryption coefficient of the stress-focused area, and the deviation between the force analysis after grid encryption and the theoretical force analysis based on the encryption coefficient is used to determine whether iterative calculation is needed, and finally finite element mesh encryption is implemented for the stress-focused area with a mesh encryption coefficient corresponding to the set value whose deviation does not exceed the set value, thereby ensuring that the finite element analysis accuracy of different parts of the special-shaped large-section annular prestressed beam is consistent and meets the project accuracy requirements, and avoiding a significant increase in the amount of calculation due to excessive mesh encryption, so that all project accuracy requirements are met and relative consistency of accuracy is maintained under reasonable computing resource usage.

[0140] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. The design method of special-shaped large-section annular prestressed beam based on finite element model is characterized by: The following steps are involved: Step 1: Divide the construction sections: Obtain the actual conditions of the construction site, determine the basic geometric parameters and material properties of the ring beam, determine a layout plan for the ring beam based on the basic geometric parameters and material properties of the ring beam, and divide the entire ring beam into several construction sections based on the layout plan; Step 2: Establish a finite element model: Based on the basic geometric parameters and material properties of the ring beam, a finite element model of the ring beam is established. The finite element model uses the birth-death element technique to simulate the different structural states of each construction section. Specifically, the model includes: A hybrid grid combining structured and unstructured grids is used for finite element basic division. The structured grid is given priority. The regular parts of the large-section annular prestressed beam are divided by structured grids, while the irregular parts at the edges are divided by unstructured grids. By using different types of grids in different areas, it is adapted to the special-shaped structure of the large-section annular prestressed beam. Based on the basic theory of structural stress, the key stress-bearing areas of large-section annular prestressed beams were preliminarily determined, including stress concentration areas, areas with large deformation, and areas where boundary conditions act. Mesh density was then refined for these key stress-bearing areas. A transition area for mesh density change was formed between the mesh refinement area and the finite element basic division to ensure a smooth transition of mesh density. The grid encryption is specifically as follows: Obtain finite element force analysis data under various grid density division conditions and the corresponding force analysis accuracy data; Obtain the stress limit data of concrete with different steel bar configurations at different ambient temperatures, taking the ambient temperature as The stress limit data of concrete with different steel bar configurations at different ambient temperatures is used as the basis to determine the stress limit data of concrete with different steel bar configurations at different ambient temperatures to be converted into the ambient temperature of Temperature influence coefficient of the stress limit data at ; Based on the stress theory of prestressed beams, stress analysis was performed on different parts of the special-shaped large-section circular prestressed beams to obtain theoretical stress data for each part, including theoretical stress data for key stress-bearing areas. In combination with the accuracy requirements for the design of special-shaped large-section circular prestressed beams, the mesh refinement coefficient for key stress-bearing areas was calculated using the following formula: in, is the mesh density factor of the stressed area, The finite element mesh density is the theoretical stress data of the stress-focused area when the corresponding stress analysis accuracy data is equal to the design accuracy requirement. In order to ensure that the force analysis accuracy data is equal to the design accuracy requirements, the finite element mesh density corresponding to the non-stress key focus area and non-transition area is The ambient temperature of the special-shaped large-section annular prestressed beam for finite element analysis Corresponding temperature influence coefficient; Perform style encryption on the stress-focused area according to the calculated mesh encryption coefficient, and perform finite element stress analysis. If the deviation between the stress data of the stress-focused area obtained by analysis and the theoretical stress data exceeds a set value, the stress data obtained by analysis of the stress-focused area will replace the theoretical stress data. Repeat the above steps, and iterate the calculation until the deviation between the stress data of the stress-focused area obtained by analysis and the theoretical stress data does not exceed a set value. The mesh refinement coefficient of the stress-sensitive area of ​​the last focus is calculated using the above iterative calculation, and the finite element mesh is refined in the stress-sensitive area; Step 3: Finite element calculation: Based on the finite element model, simulate the prestressed tendon tensioning and post-casting joint needle reinforcement tensioning process, calculate the stress, displacement and internal force distribution of the ring beam at each stage, and make optimization adjustments based on the calculation results; Step 4: Determine the distribution of prestressed tendons: Analyze the stress distribution within the ring beam after tensioning, adjust the distribution of prestressed tendons based on the tensioning analysis results, and adopt an asymmetric prestressing arrangement. This also includes: According to the stress requirements of the special-shaped cross-section and the stress conditions at different positions of the ring beam, combined with the division of the ring beam construction sections, the arrangement angle, quantity and distribution of the prestressed tendons are adjusted; Step 5: Design verification and construction plan optimization: Based on the calculation results, a comprehensive analysis is conducted on the prestressed reinforcement layout plan, construction section division and construction technology, and the construction plan is optimized based on the comprehensive analysis results.

2. The design method of the special-shaped large-section annular prestressed beam based on the finite element model according to claim 1 is characterized in that: The division of construction sections specifically includes: Based on the geometric parameters of the ring beam and the actual conditions of the construction site, the layout design of the ring beam is carried out to determine the prestressed reinforcement layout, construction sequence, support and connection methods of the ring beam; Determine the ring beam segmentation plan based on the construction environment and construction schedule, including the length, load characteristics and coordination between each construction segment; Based on the geometric characteristics of the ring beam and the tensioning requirements of the prestressed tendons, the construction sections are divided into detailed sections, and the construction nodes and key processes of each section are determined; Set the corresponding operation sequence and duration for each construction node, clarify the construction progress of each construction section, the connection time of key processes and the required material transportation cycle.

3. The design method of the special-shaped large-section annular prestressed beam based on the finite element model according to claim 2 is characterized in that: Step 2: Establish a finite element model, including: Extract the three-dimensional geometric information of the ring beam and determine the mechanical performance parameters of the ring beam based on the material properties of the ring beam; Input the three-dimensional geometric information of the ring beam into a three-dimensional modeling tool to construct a three-dimensional geometric model of the ring beam, and set mechanical properties for each part of the ring beam based on the mechanical performance parameters of the ring beam; Set up life and death units for each ring beam structure, determine the specific structural state of each structure in different construction sections, and simulate the mechanical behavior of each construction section of the ring beam based on the specific structural state of each structure in different construction sections; Among them, each construction section activates or kills the corresponding units according to the actual construction progress and scheduled construction nodes, and dynamically adjusts the construction process and the specific structural status of each structure in the finite element model.

4. The design method of the special-shaped large-section annular prestressed beam based on the finite element model according to claim 3 is characterized in that: The finite element model further includes: According to the mechanical behavior of each construction section of the ring beam and the actual construction conditions, the position of the support point, the support type and the support reaction force are set, the constraint conditions of the support are determined, and the contact relationship between the various structures of the ring beam is set; In each construction section, loads are applied to the ring beam according to the construction process to simulate the stress state of the ring beam in different construction sections. The load application method for each construction section is determined based on the actual construction conditions, and the load changes over time are modeled.

5. The design method of the special-shaped large-section annular prestressed beam based on the finite element model according to claim 4 is characterized in that: Dynamically adjust the construction technology and specific structural status of each structure in the finite element model, including: Monitor the load, deformation, and stress changes of each construction section in real time, and adjust the structural status according to predetermined rules at the end of each construction cycle; At the end of the monitoring period, obtain the magnitude of changes in various types of data within the current detection period and determine the type of data with the largest change; Determine the target data type that needs to be adjusted in the next cycle based on the data change magnitude assessment results. At the same time, adjust the frequency of data collection based on changes in load and mechanical behavior during the construction process. The specific structural status of each structure in the finite element model is adjusted according to the construction progress and load changes. At the same time, it is dynamically updated according to the material mechanical properties in the model.

6. The design method of the special-shaped large-section annular prestressed beam based on the finite element model according to claim 5 is characterized in that: Finite element calculation, including: Stress analysis: For each construction section, calculate the distribution of hoop stress, axial stress, shear stress and bending stress of the ring beam; Deformation analysis: The displacement and deformation of the ring beam at each construction stage are calculated using a finite element model, with a focus on analyzing whether the structural deformation meets the design requirements and whether there is a risk of excessive deformation. Crack development prediction: Based on stress analysis and deformation analysis, the finite element model is used to simulate the location, shape and expansion trend of possible cracks in the ring beam; Analysis of the internal force distribution of the ring beam at each stage: During the finite element model simulation process, the internal force distribution of the ring beam at each construction stage is calculated, and the distribution of stress, displacement and internal force of the ring beam is determined based on the calculation results.

7. The design method of the special-shaped large-section annular prestressed beam based on the finite element model according to claim 6, characterized in that: Determine the distribution of prestressed tendons, including: Analyze the stress distribution of each construction section of the ring beam. During the prestressing tendon tensioning stage, analyze the axial stress, bending stress, and shear stress in each area. Based on the simulation results of the finite element model, the stress concentration characteristics in the ring beam are identified and the key areas for prestressing reinforcement arrangement are determined; Based on the stress analysis results of the ring beam, the reasonable number and layout of prestressed tendons are determined. The number of prestressed tendons can be increased in areas with concentrated stress, and the arrangement of prestressed tendons can be reduced in areas with low stress.

8. The design method of the special-shaped large-section annular prestressed beam based on the finite element model according to claim 7 is characterized in that: Comprehensive analysis of prestressed reinforcement arrangement, construction section division, and construction technology, including: Conduct a comprehensive assessment of prestressed reinforcement layout, construction section division, and construction technology to ensure that the adjusted prestressed reinforcement layout, construction section division, and construction technology meet the design requirements. Based on the comprehensive assessment results, conduct a risk assessment during the construction process, propose corresponding emergency plans, and match corresponding corrective measures according to the risk characteristics of different construction stages.

9. The design method of the special-shaped large-section annular prestressed beam based on the finite element model according to claim 1, characterized in that: The establishing of the finite element model further includes: The boundary fitting technology is used to make the boundary of the finite distance grid unit match the boundary of the actual large cross-section annular prestressed beam as closely as possible; Implement finite element simulation analysis, automatically perform adaptive optimization and adjustment of the grid based on the error estimation of the simulation analysis calculation results, or the stress and deformation changes as physical quantities, and finally form an optimized finite element model.

10. The design method of the special-shaped large-section annular prestressed beam based on the finite element model according to claim 9, characterized in that: The implementation of the finite element simulation analysis includes using a genetic algorithm to perform simulation analysis, specifically as follows: Randomly generate a set of initial populations within the range of the design variables, and ensure that the initial population has a certain degree of diversity; Constructing a fitness function , determine the objective function of the fitness function optimization, the objective function involves the performance index of the structure, including minimizing stress, deformation and weight, or maximizing stiffness and stability; The constraints of the design variables are incorporated into the fitness function. The constraints include the upper and lower limits of the design variables, the strength and stability requirements of the structure, and the penalty function method is used to transform the constraints into part of the fitness function. That is, when the constraints are violated, the fitness value is penalized to reduce the fitness value. According to the fitness value of individuals in the initial population, the selection probability of individuals is calculated using the following formula: in, Indicates the number of the initial population The probability of selection of an individual; Indicates the number of the initial population The fitness value of each individual; Indicates the number of individuals contained in the initial population; Indicates the number of the initial population The fitness value of each individual; Set the crossover probability, mutation probability, and iteration termination condition. In each iteration, perform fitness selection, multi-point crossover, and Gaussian mutation operations to generate a new population and calculate the fitness value of the new population. Evaluate and select the new population based on the fitness value, eliminate individuals with low fitness, and retain individuals with high fitness until the termination condition is met, thus obtaining the optimal solution of the genetic algorithm. After the above genetic algorithm simulation analysis, the optimal solution of the genetic algorithm is substituted into the finite element model for verification to check whether all design requirements and constraints are met. If not, the design optimization of the special-shaped large-section annular prestressed beam is carried out, and after optimization, the finite element division, simulation analysis and verification are re-performed until all design requirements and constraints are met.

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