Design method of special-shaped large-section annular prestressed beam based on finite element model

Abstract

The invention discloses a design method of a special-shaped large-section annular prestressed beam based on a finite element model, and relates to the technical field of civil engineering. The problems that due to the fact that a special-shaped ring beam is symmetrically arranged and tensioned, local stress is uneven, local concrete cracks possibly occur, and the stability of the whole structure is affected are solved. Through the finite element model and the finite element analysis technology, in combination with the specific stress characteristics of the special-shaped large-section ring beam, optimized arrangement of the prestressed tendons is achieved, the stress uniformity and stability of the structure are ensured, asymmetric prestressed tendon arrangement can be flexibly adjusted according to specific engineering requirements, the tension values borne by the section are consistent, and the construction efficiency is improved. According to the ring beam tensioning method, the integrity of the tensioned ring beam is better, the construction precision and economical efficiency of the structure are improved, risks in the construction process are effectively reduced through step-by-step construction and application of the life and death unit technology, and the construction efficiency and the structure safety are improved.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering, and 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 column. The large ring beam is a perfect circle as a whole, and its cross section is a parallelogram with an inner curved surface. It mainly serves as a load-bearing member of the overall roof structure. However, in the prior art, the steel bars at the beam-column joints are dense and complex, and the ring beams, columns, roof cross beams, and prestressed steel strand pipes are interspersed at the same time. The diameter of the longitudinal bars and stirrups of the ring beam is large. The arrangement of prestress needs to consider avoiding the densely reinforced parts and meet the overall tensile stress requirements. As a result, the prestressing arrangement design of the special-shaped large-section annular prestressed concrete structure beam is difficult. The traditional symmetrical arrangement method is difficult to meet the force requirements of the special-shaped cross-section beam, which is easy to cause local uneven force 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 a special-shaped large-section annular prestressed beam based on a finite element model. The finite element model is established to perform finite element calculations, and an asymmetric prestressing arrangement is adopted according to the characteristics of the special-shaped section, so as to ensure that the prestressing meets the design requirements and ensure 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: The design method of the special-shaped large-section annular prestressed beam based on the finite element model includes the following steps: Step 1: Divide the construction sections: obtain the actual situation of the construction site, determine the basic geometric parameters and material properties of the ring beam, determine the layout of 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; Step 2: Establishing a finite element model: Establishing a finite element model of the ring beam based on basic geometric parameters and material properties of the ring beam, wherein the finite element model uses birth-death unit technology to simulate different structural states of each construction section; Step 3: Finite element calculation: Based on the finite element model, simulate the prestressed tendon tensioning and post-casting band seam needle reinforcement tensioning process, calculate the ring beam stress, displacement and internal force distribution at each stage, and make optimization adjustments based on the calculation results; Step 4: Determine the distribution of prestressed tendons: Analyze the stress distribution in the ring beam after tensioning, adjust the distribution of prestressed tendons according to the tensioning analysis results, and adopt an asymmetric prestressing arrangement; Step 5: Design verification and construction scheme optimization: Based on the calculation results, conduct a comprehensive analysis of the prestressed reinforcement arrangement plan, construction section division and construction technology, and optimize the construction plan based on the comprehensive analysis results.

[0005] Furthermore, the division of the 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 layout plan of the prestressed tendons, construction sequence, support and connection methods of the ring beam; According to the construction environment and construction schedule, determine the segmentation plan of the ring beam, including the length of each construction segment, the stress characteristics and the coordination relationship between the construction segments; According to the geometric characteristics of the ring beam and the tensioning requirements of the prestressed tendons, the division of the construction sections is refined, and the construction nodes and key processes of each construction 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.

[0006] Further, step 2: establish a finite element model, specifically 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 structure of the ring beam, 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 the scheduled construction nodes, and dynamically adjusts the construction process and the specific structural status of each structure in the finite element model.

[0007] Furthermore, the finite element model further includes: According to the mechanical behavior of each construction section of the ring beam and the actual construction situation, 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 of each structure of the ring beam is set; In each construction section, load is 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 of each construction section is determined based on the actual construction situation, and the load change over time is modeled.

[0008] Furthermore, the construction process and the specific structural status of each structure in the finite element model are dynamically adjusted, 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 change amplitude of various types of data in the current detection period, and determine the data type with the largest change; Determine the target data type that needs to be adjusted in the next cycle based on the data change amplitude assessment results. At the same time, adjust the frequency of data collection based on the 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.

[0009] Further, finite element calculations include: 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 through the finite element model, focusing 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 possible crack location, shape and expansion trend 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.

[0010] Furthermore, determining the distribution of prestressed tendons also includes: The stress distribution of each construction section of the ring beam is analyzed. In the prestressing tendon tensioning stage, the axial stress, bending stress and shear stress of each area are analyzed; 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 the arrangement of prestressed tendons are determined; According to 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 low-stress areas. 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 construction section division of the ring beam, the layout angle, quantity and distribution form of the prestressed tendons are adjusted.

[0011] Furthermore, a comprehensive analysis of the prestressed reinforcement arrangement scheme, construction section division and construction technology is conducted, including: Conduct a comprehensive assessment of prestressed reinforcement arrangement, construction section division and construction technology to ensure that the adjusted prestressed reinforcement arrangement plan, construction section division and construction technology meet the design requirements; conduct a risk assessment during the construction process based on the comprehensive assessment results, propose corresponding emergency plans, and match corresponding corrective measures according to the risk characteristics of different construction stages.

[0012] Furthermore, the establishment of the finite element model specifically includes: A hybrid grid combining structured grid and unstructured grid is used for finite element basic division, where structured grid is given priority. Structured grid is used for regular parts of large-section annular prestressed beams, and unstructured grid is used for irregular parts at the edges. Different types of grids are used in different areas to adapt to the special-shaped structures of large-section annular prestressed beams. According to the basic theory of structural stress, the stress focus areas of large-section annular prestressed beams are preliminarily determined, including stress concentration areas, large deformation areas and boundary condition action areas. Grid density is refined for the stress focus areas. A transition area of ​​grid density change is formed between the grid refinement area and the finite element basic division part to ensure a smooth transition of grid density. The boundary fitting technology is used to make the boundary of the finite distance grid unit as close as possible to the boundary of the actual large-section annular prestressed beam; Finite element simulation analysis is carried out, and according to the error estimation of the simulation analysis calculation results, or the stress and deformation changes of physical quantities, the mesh is automatically optimized and adjusted to finally form an optimized finite element model.

[0013] Furthermore, the implementation of finite element simulation analysis includes using a genetic algorithm to perform simulation analysis, as follows: Within the range of the design variables, a set of initial populations is randomly generated, and the initial population is ensured to have a certain degree of diversity; Constructing the 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. The constraints are transformed into a part of the fitness function through the penalty function method. 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 initial population The probability of selection of an individual; Indicates the initial population The fitness value of each individual; Indicates the number of individuals contained in the initial population; Indicates 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 according to the fitness value, eliminate individuals with low fitness, and retain individuals with high fitness until the termination condition is met, and obtain 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 verify whether it meets all design requirements and constraints. If not, the design optimization of the special-shaped large-section circular prestressed beam is carried out, and the finite element division, simulation analysis and verification are carried out again after optimization until all design requirements and constraints are met.

[0014] Furthermore, the mesh encryption is specifically as follows: Obtain finite element force analysis data under various grid density division conditions and the corresponding force analysis accuracy data; The stress limit data of concrete with different steel bar configurations at different ambient temperatures are obtained. The stress limit data of concrete with different steel configurations at different ambient temperatures is used as the basis to determine the conversion of the stress limit data of concrete with different steel configurations at different ambient temperatures to the ambient temperature of Temperature influence coefficient of stress limit data at time; According to the stress theory of prestressed beams, stress analysis is carried out on different parts of the special-shaped large-section circular prestressed beams to obtain theoretical stress data of each part, including theoretical stress data of the stress-focused areas; combined with the accuracy requirements of the design of special-shaped large-section circular prestressed beams, the following formula is used to calculate the mesh density coefficient of the stress-focused areas: in, is the mesh density factor of the stress-focused area, The finite element mesh density is the theoretical force data of the key stress-related area when the corresponding force 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 focus area and non-transition area is The ambient temperature of the special-shaped large-section annular prestressed beam for finite element analysis The corresponding temperature influence coefficient; According to the calculated mesh encryption coefficient, style encryption is performed on the stress-focused area, and finite element stress analysis is performed. If the deviation between the stress data of the stress-focused area obtained by analysis and the theoretical stress data exceeds the set value, the stress data of the stress-focused area obtained by analysis replaces the theoretical stress data, and the above steps are repeated, and the calculation is iterated in this way until the deviation between the stress data of the stress-focused area obtained by analysis and the theoretical stress data does not exceed the set value; The mesh encryption coefficient of the stress-related key focus area calculated in the last iteration is used to implement finite element mesh encryption on the stress-related key focus area.

[0015] Compared with the prior art, the present invention has the following beneficial effects: Through the finite element model and finite element analysis technology, combined with the specific stress characteristics of the special-shaped large-section ring beam, 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 value of the cross-section is 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, improves the construction accuracy and economy of the structure, and 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

[0016] Figure 1 It is a step diagram of the design method of the special-shaped large-section annular prestressed beam based on the finite element model of the present invention; Figure 2 It is a top view geometrical schematic diagram of the overall structure of the ring beam of the present invention; Figure 3 It is a schematic diagram of the finite element model of the ring beam of the present invention; Figure 4 It is a schematic diagram of the hoop stress of the ring beam cross section of the present invention; Figure 5 It is a schematic diagram of the arrangement position of the prestressed tendons of the present invention. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0018] In order to solve the technical problem that the symmetrical arrangement of the special-shaped ring beam will cause uneven local stress, which may cause local concrete cracks and affect the stability of the overall structure, please refer to Figure 1-Figure 5 , this embodiment provides the following technical solutions: The design method of the special-shaped large-section annular prestressed beam based on the finite element model includes the following steps: Step 1: Divide the construction sections: Obtain the actual conditions of the construction site, including the location of the ring beam, the geometry of the construction site, the surrounding environmental conditions, the layout of the structural columns and the support system, etc., determine the basic geometric parameters and material properties of the ring beam, and determine the layout of the ring beam based on the basic geometric parameters and material properties of the ring beam. Based on the layout, divide the ring beam into several construction sections, including: 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 layout plan of the prestressed tendons, construction sequence, support and connection methods of the ring beam; According to the construction environment and construction schedule, determine the segmentation plan of the ring beam, including the length of each construction segment, the stress characteristics and the coordination relationship between the construction segments; According to the geometric characteristics of the ring beam and the tensioning requirements of the prestressed tendons, the division of the construction sections is refined, and the construction nodes and key processes of each construction section are determined, such as the specific steps and sequence of prestressed tendon tensioning, concrete pouring, and seam needle tendon tensioning; 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; Step 2: Establish a finite element model: Establish a finite element model of the ring beam based on the basic geometric parameters and material properties of the ring beam, including the ring beam structure, prestressed tendons, seam needle tendons and supports, etc. The finite element model uses the life-and-death unit technology to simulate the different structural states of each construction section, and clearly defines the design requirements, including the horizontal tension and prestress values, which are verified by finite element calculation results; Step 3: Finite element calculation: Based on the finite element model, simulate the tensioning process of prestressed tendons and post-casting seam needle tendons, including prestressed tendons tensioning and post-casting seam needle tendons tensioning, observe the stress, deformation and crack development of the ring beam, calculate the stress, displacement and internal force distribution of the ring beam at each stage, evaluate the effects of prestressed tendons and seam needle tendons, and optimize and adjust according to the calculation results to avoid problems such as local overload, excessive deformation or uneven structural stress; Step 4: Determine the distribution of prestressed tendons: Analyze the stress distribution in the ring beam after tensioning, including the axial stress, bending stress and shear stress on the cross section of the ring beam, adjust the distribution of prestressed tendons according to 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; Step 5: Design verification and construction scheme optimization: Based on the calculation results, conduct a comprehensive analysis of the prestressed reinforcement arrangement plan, construction section division and construction technology, and optimize the construction plan based on the comprehensive analysis results.

[0019] In this embodiment, combined with the arrangement of the ring beam and structural columns on site, the ring beam is divided into 12 construction sections, and the finite element model of the prestressed tendons, seam needle tendons, concrete ring beam and columns in the ring beam is established. The design requirements are: the horizontal tension design value is 120000kN, and the prestressing stress is not less than 4.3MPa; the finite element calculation is performed using abaqus software; 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 annular compressive stress of the ring beam concrete is 3.1-9.8MPa; the overall annular 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 annular compressive stress of the post-cast zone section is 3.6-6.2MPa, and the overall stress level About 4.5MPa, the first principal compressive stress of the section is 0.3-0.18MPa, the minimum stress is located in the middle area of ​​the section, and the overall stress level is about 0.07MPa; after the overall tensioning is completed, the overall stress of the prestressed tendons in the ring beam is about 880MPa; the internal force of the concrete ring beam section is about 126000kN; the overall stress of the seam needle tendons is about 920MPa; the compressive stress result is >4.3MPa, and the axial force 126000KN>120000KN, which meets the design requirements; thereby determining the arrangement position of the prestressed tendons.

[0020] In this embodiment, step 2: establishing a finite element model, specifically includes: Extract the three-dimensional geometric information of the ring beam, including the complex special-shaped cross-section 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 3D geometric information of the ring beam into the 3D modeling tool to construct a 3D geometric model of the ring beam, including the shape of the ring beam, the layout of the prestressed tendons, the layout of the seam needle tendons, the position of the supports and the relationship between the structural columns, accurately express the structural characteristics of the ring beam, including the geometric changes of each construction section, and prepare for the subsequent finite element analysis. Based on the mechanical performance parameters of the ring beam, set the mechanical properties of each part of the ring beam structure, 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; In this embodiment, for concrete, a stress-strain curve model (such as a nonlinear model) suitable for large-section beams is used to simulate its behavior under different stress states (including yield, failure, shrinkage and other effects); for prestressed tendons and seam needle tendons, an elastic-plastic or ideal elastic model suitable for prestressed tendons is used. Ensure that the mechanical properties of these materials (such as elastic modulus, yield strength, etc.) are consistent with the materials used in actual projects; Set up life and death units for each structure of the ring beam, 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 the 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.

[0021] In this embodiment, the construction process and the specific structural state of each structure in the finite element model are dynamically adjusted, specifically 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 change amplitude of various data in the current detection period, such as the increase of tension load, the hardening speed of concrete, etc., and determine the data type with the largest change; Determine the target data type that needs to be adjusted in the next cycle based on the data change amplitude assessment results. For example, if the stress change amplitude in the prestressed tendon tensioning stage is too large, it may be necessary to adjust the tensioning rate, or appropriately extend the tensioning time in the next cycle. At the same time, adjust the frequency of data collection based on the changes in load and mechanical behavior during the construction process. For example, if the stress changes drastically in a certain construction section, it may be necessary to shorten the monitoring cycle and increase the frequency of data collection to ensure that structural abnormalities are discovered in a timely manner. 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 killing different structural units at the end of each construction cycle, adjusting the supports and boundary conditions according to the changes in the stress state of the ring beam, etc. At the same time, the material mechanical properties in the model are dynamically updated. 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.

[0022] 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.

[0023] In this embodiment, the finite element model further includes: According to the mechanical behavior of each construction section of the ring beam and the actual construction situation, set the position of the support point, the support type (such as hinged support, fixed support, etc.) and the support reaction force, determine the constraint conditions of the support, ensure that the deformation and mechanical behavior of the ring beam during the simulation are consistent with the actual project, and set the contact relationship of each structure of the ring beam; In each construction section, loads are applied to the ring beam according to the construction process, such as concrete deadweight, construction load, tension load of prestressed tendons, etc., to simulate the stress state of the ring beam under different construction sections. The load application method of each construction section is determined based on the actual construction conditions, and the load change over time is modeled.

[0024] 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, so that the simulation results are more realistic, and can better 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 considered. It can more truly 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.

[0025] In this embodiment, the finite element calculation specifically includes: Stress analysis: For each construction section, for example, during the tensioning process of prestressed tendons and seam needle tendons, calculate the distribution of hoop stress, axial stress, shear stress and bending stress of the ring beam, evaluate the effects of prestressed tendons and seam needle tendons, and determine whether they can effectively reduce stress concentration and ensure the safety of the structure; In this embodiment, it includes prestressed tendon tensioning: in the process of prestressed tendon tensioning, 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, wherein the load application process of each tensioning section considers the initial stress of the prestressed tendon, the increase of subsequent tensioning force, and the tensioning adjustment during construction; post-casting belt seam needle tendon tensioning: in the post-casting belt construction section, the seam needle tendon tensioning process after the post-casting belt concrete is poured 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; Deformation analysis: The displacement and deformation of the ring beam at each construction stage are calculated through the finite element model, focusing 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 possible crack location, shape and expansion trend in the ring beam, especially during the tensioning of prestressed tendons or seam needle tendons, to monitor whether the cracks are over-extended and predict possible crack development trends; 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 stress, displacement and internal force distribution of the ring beam are determined based on the calculation results. For example, the effects of the prestressed tendons and stitching tendons in each construction stage are evaluated to analyze whether they can effectively balance the overall internal force of the ring beam to avoid local overload or mechanical unevenness.

[0026] In this embodiment, determining the distribution of prestressed tendons also includes: The stress distribution of each construction section of the ring beam is analyzed. In the prestressing tendon tensioning stage, the axial stress, bending stress and shear stress of each area are analyzed; 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 the arrangement of prestressed tendons are determined; According to the stress analysis results of the ring beam, determine the reasonable number and layout of prestressed tendons. In areas with concentrated stress, increase the number of prestressed tendons to ensure that the stress in these areas is balanced and reduce the risk of local overload. Reduce the arrangement of prestressed tendons in low-stress areas to avoid material waste. 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 construction section division of the ring beam, the layout angle, quantity and distribution of the prestressed tendons are adjusted to ensure that the stress on 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.

[0027] In this embodiment, by analyzing the stress of each construction stage of the ring beam, the effect 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 tensioning process of the prestressed tendons, the applied tensioning force and its gradual increase are simulated by the finite element model. Taking into account the changes in the initial stress of the prestressed tendons and the subsequent tensioning force, the load application process of each construction section is accurately simulated, and in the tensioning stage of the seam needle tendons of the post-casting belt, 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 the construction process, thereby improving construction efficiency and the safety and stability of the structure.

[0028] In this embodiment, a comprehensive analysis of the prestressed tendon arrangement scheme, construction section division and construction technology is performed, which also includes: Conduct a comprehensive assessment of the prestressed tendon arrangement, construction section division and construction technology to ensure that the adjusted prestressed tendon arrangement plan, construction section division and construction technology meet the design requirements. Based on the comprehensive assessment results, conduct a risk assessment during the construction process, such as uneven prestressed tendon tensioning, concrete cracks and other problems, and propose corresponding emergency plans. Match corresponding correction measures according to the risk characteristics of different construction stages to ensure rapid response in emergencies and smooth construction. In this embodiment, the length of each construction section, the construction sequence, the order of prestressing tendons tensioning and the timing of construction load application need to be reasonably arranged according to the deformation and mechanical behavior of the ring beam. When dividing the construction sections, the force characteristics of each section, the mutual coordination relationship and the feasibility of the construction progress are comprehensively considered to ensure the continuity and efficiency of the construction; it can ensure that the prestressing tendon layout plan, construction section division and construction technology are fully optimized, and ensure the stability and safety of the structure during the construction process.

[0029] On the basis of the above-mentioned embodiment, the establishment of the finite element model specifically includes: A hybrid grid combining structured grid and unstructured grid is used for finite element basic division, where structured grid is given priority. Structured grid is used for regular parts of large-section annular prestressed beams, and unstructured grid is used for irregular parts at the edges. Different types of grids are used in different areas to adapt to the special-shaped structures of large-section annular prestressed beams. According to the basic theory of structural stress, the stress focus areas of large-section annular prestressed beams are preliminarily determined, including stress concentration areas, large deformation areas and boundary condition action areas. Grid density is refined for the stress focus areas. A transition area of ​​grid density change is formed between the grid refinement area and the finite element basic division part to ensure a smooth transition of grid density. The boundary fitting technology is used to make the boundary of the finite distance grid unit as close as possible to the boundary of the actual large-section annular prestressed beam; Finite element simulation analysis is carried out, and according to the error estimation of the simulation analysis calculation results, or the stress and deformation changes of physical quantities, the mesh is automatically optimized and adjusted to finally form an optimized finite element model.

[0030] In this embodiment, by combining structured grids with unstructured grids, boundary fitting technology is used in the unstructured grid part, so that the boundary of the finite distance grid unit is as consistent as possible with the boundary of the actual large-section annular prestressed beam, thereby improving the flexibility and adaptability of grid division, so that the finite element grid division can better fit the special shape of the large-section annular prestressed beam, avoiding the increase in the complexity of the analysis by using all unstructured grids, and taking into account the balance between the amount of analysis and accuracy; by locally encrypting the grids in key parts, the accuracy is further improved without excessively increasing the amount of calculation, thereby ensuring the calculation efficiency; by setting a transition area from the encrypted area to the basic division part, a smooth transition of the grid density from high to low is ensured, thereby avoiding numerical errors and non-convergence problems caused by sudden changes in the grid size; through finite element simulation analysis, the adaptive optimization adjustment of the grid is automatically implemented.

[0031] Based on the above-mentioned embodiment, the implementation of finite element simulation analysis includes using genetic algorithm to perform simulation analysis, which is as follows: Within the range of the design variables, a set of initial populations is randomly generated, and the initial population is ensured to have a certain degree of diversity; Constructing the 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. The constraints are transformed into a part of the fitness function through the penalty function method. 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 initial population The probability of selection of an individual; Indicates the initial population The fitness value of each individual; Indicates the number of individuals contained in the initial population; Indicates 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 according to the fitness value, eliminate individuals with low fitness, and retain individuals with high fitness until the termination condition is met, and obtain 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 verify whether it meets all design requirements and constraints. If not, the design optimization of the special-shaped large-section circular prestressed beam is carried out, and the finite element division, simulation analysis and verification are carried out again after optimization until all design requirements and constraints are met.

[0032] In this embodiment, a genetic algorithm is used for simulation analysis, and low fitness is eliminated by iterative execution of fitness selection, multi-point crossover and Gaussian mutation operations to obtain the optimal solution, 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 and 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.

[0033] Based on the above-mentioned embodiment, the mesh encryption is specifically as follows: Obtain finite element force analysis data under various grid density division conditions and the corresponding force analysis accuracy data; The stress limit data of concrete with different steel bar configurations at different ambient temperatures are obtained. The stress limit data of concrete with different steel configurations at different ambient temperatures is used as the basis to determine the conversion of the stress limit data of concrete with different steel configurations at different ambient temperatures to the ambient temperature of Temperature influence coefficient of stress limit data at time; According to the stress theory of prestressed beams, stress analysis is carried out on different parts of the special-shaped large-section circular prestressed beams to obtain theoretical stress data of each part, including theoretical stress data of the stress-focused areas; combined with the accuracy requirements of the design of special-shaped large-section circular prestressed beams, the following formula is used to calculate the mesh density coefficient of the stress-focused areas: in, is the mesh density factor of the stress-focused area, The finite element mesh density is the theoretical force data of the key stress-related area when the corresponding force 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 focus area and non-transition area is The ambient temperature of the special-shaped large-section annular prestressed beam for finite element analysis The corresponding temperature influence coefficient; According to the calculated mesh encryption coefficient, style encryption is performed on the stress-focused area, and finite element stress analysis is performed. If the deviation between the stress data of the stress-focused area obtained by analysis and the theoretical stress data exceeds the set value, the stress data of the stress-focused area obtained by analysis replaces the theoretical stress data, and the above steps are repeated, and the calculation is iterated in this way until the deviation between the stress data of the stress-focused area obtained by analysis and the theoretical stress data does not exceed the set value; The mesh encryption coefficient of the stress-related key focus area calculated in the last iteration is used to implement finite element mesh encryption on the stress-related key focus area.

[0034] 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 can be used 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.

[0035] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. The design method of the special-shaped large-section annular prestressed beam based on the finite element model is characterized by: The following steps are involved: Step 1: Divide the construction sections: obtain the actual situation of the construction site, determine the basic geometric parameters and material properties of the ring beam, determine the layout of 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; Step 2: Establishing a finite element model: Establishing a finite element model of the ring beam based on basic geometric parameters and material properties of the ring beam, wherein the finite element model uses birth-death unit technology to simulate different structural states of each construction section; Step 3: Finite element calculation: Based on the finite element model, simulate the prestressed tendon tensioning and post-casting band seam needle reinforcement tensioning process, calculate the ring beam stress, displacement and internal force distribution at each stage, and make optimization adjustments based on the calculation results; Step 4: Determine the distribution of prestressed tendons: Analyze the stress distribution in the ring beam after tensioning, adjust the distribution of prestressed tendons according to the tensioning analysis results, and adopt an asymmetric prestressing arrangement; Step 5: Design verification and construction scheme optimization: Based on the calculation results, conduct a comprehensive analysis of the prestressed reinforcement arrangement plan, construction section division and construction technology, and optimize the construction plan 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 as claimed in 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 layout plan of the prestressed tendons, construction sequence, support and connection methods of the ring beam; According to the construction environment and construction schedule, determine the segmentation plan of the ring beam, including the length of each construction segment, the stress characteristics and the coordination relationship between the construction segments; According to the geometric characteristics of the ring beam and the tensioning requirements of the prestressed tendons, the division of the construction sections is refined, and the construction nodes and key processes of each construction 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 as claimed in 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 structure of the ring beam, 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 the 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 as claimed in 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 situation, 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 of each structure of the ring beam is set; In each construction section, load is 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 of each construction section is determined based on the actual construction situation, and the load change over time is modeled.

5. The design method of the special-shaped large-section annular prestressed beam based on the finite element model as claimed in 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 change amplitude of various types of data in the current detection period, and determine the data type with the largest change; Determine the target data type that needs to be adjusted in the next cycle based on the data change amplitude assessment results. At the same time, adjust the frequency of data collection based on the 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 as claimed in claim 5, 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 through the finite element model, focusing 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 possible crack location, shape and expansion trend 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 as claimed in claim 6, characterized in that: Determine the distribution of prestressed tendons, including: The stress distribution of each construction section of the ring beam is analyzed. In the prestressing tendon tensioning stage, the axial stress, bending stress and shear stress of each area are analyzed; 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 the arrangement of prestressed tendons are determined; According to 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. 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 construction section division of the ring beam, the layout angle, quantity and distribution form of the prestressed tendons are adjusted.

8. The design method of the special-shaped large-section annular prestressed beam based on the finite element model as claimed in claim 7, characterized in that: Comprehensive analysis of prestressed reinforcement arrangement, construction section division and construction technology, including: Conduct a comprehensive assessment of prestressed reinforcement arrangement, construction section division and construction technology to ensure that the adjusted prestressed reinforcement arrangement plan, construction section division and construction technology meet the design requirements; conduct a risk assessment during the construction process based on the comprehensive assessment results, 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 as claimed in claim 1, characterized in that: The establishment of the finite element model specifically includes: A hybrid grid combining structured grid and unstructured grid is used for finite element basic division, where structured grid is given priority. Structured grid is used for regular parts of large-section annular prestressed beams, and unstructured grid is used for irregular parts at the edges. Different types of grids are used in different areas to adapt to the special-shaped structures of large-section annular prestressed beams. According to the basic theory of structural stress, the stress focus areas of large-section annular prestressed beams are preliminarily determined, including stress concentration areas, large deformation areas and boundary condition action areas. Grid density is refined for the stress focus areas. A transition area of ​​grid density change is formed between the grid refinement area and the finite element basic division part to ensure a smooth transition of grid density. The boundary fitting technology is used to make the boundary of the finite distance grid unit as close as possible to the boundary of the actual large-section annular prestressed beam; Finite element simulation analysis is carried out, and according to the error estimation of the simulation analysis calculation results, or the stress and deformation changes of physical quantities, the mesh is automatically optimized and adjusted to 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 finite element simulation analysis includes using a genetic algorithm to perform simulation analysis, as follows: Within the range of the design variables, a set of initial populations is randomly generated, and the initial population is ensured to have a certain degree of diversity; Constructing the 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. The constraints are transformed into a part of the fitness function through the penalty function method. 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 initial population The probability of selection of an individual; Indicates the initial population The fitness value of each individual; Indicates the number of individuals contained in the initial population; Indicates 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 according to the fitness value, eliminate individuals with low fitness, and retain individuals with high fitness until the termination condition is met, and obtain 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 verify whether it meets all design requirements and constraints. If not, the design optimization of the special-shaped large-section circular prestressed beam is carried out, and the finite element division, simulation analysis and verification are carried out again after optimization until all design requirements and constraints are met.

11. 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 mesh encryption is specifically as follows: Obtain finite element force analysis data under various grid density division conditions and the corresponding force analysis accuracy data; The stress limit data of concrete with different steel bar configurations at different ambient temperatures are obtained. The stress limit data of concrete with different steel configurations at different ambient temperatures is used as the basis to determine the conversion of the stress limit data of concrete with different steel configurations at different ambient temperatures to the ambient temperature of Temperature influence coefficient of stress limit data at time; According to the stress theory of prestressed beams, stress analysis is carried out on different parts of the special-shaped large-section circular prestressed beams to obtain theoretical stress data of each part, including theoretical stress data of the stress-focused areas; combined with the accuracy requirements of the design of special-shaped large-section circular prestressed beams, the following formula is used to calculate the mesh density coefficient of the stress-focused areas: in, is the mesh density factor of the stress-focused area, The finite element mesh density is the theoretical force data of the key stress-related area when the corresponding force 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 focus area and non-transition area is The ambient temperature of the special-shaped large-section annular prestressed beam for finite element analysis The corresponding temperature influence coefficient; According to the calculated mesh encryption coefficient, style encryption is performed on the stress-focused area, and finite element stress analysis is performed. If the deviation between the stress data of the stress-focused area obtained by analysis and the theoretical stress data exceeds the set value, the stress data of the stress-focused area obtained by analysis replaces the theoretical stress data, and the above steps are repeated, and the calculation is iterated in this way until the deviation between the stress data of the stress-focused area obtained by analysis and the theoretical stress data does not exceed the set value; The mesh encryption coefficient of the stress-related key focus area calculated in the last iteration is used to implement finite element mesh encryption on the stress-related key focus area.

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