Method for designing airport cement concrete pavement structure based on stress database

Abstract

This invention discloses a design method for airport cement concrete pavement structures based on a stress database. The method involves establishing a model, calculating load stress values, extracting critical load stresses, determining the basic conditions of the pavement to be designed, and superimposing the cumulative damage of the pavement. Further, it determines whether each parameter meets the requirements. Once the required values ​​are met, the cement concrete pavement structure design result is obtained. The invention also discloses a pavement structure design system, storage medium, and equipment. This invention can efficiently shorten the design cycle and effectively ensure the accuracy, efficiency, and reliability of aircraft pavement thickness design, providing technical support for airport engineering construction.

Description

Technical Field

[0001] This invention relates to the field of pavement structures, and more specifically to a design method for airport cement concrete pavement structures based on a stress database. Background Technology

[0002] Current airport concrete pavement structure design methods primarily rely on Westergaard theory or finite element analysis for stress response calculations under aircraft loads, which has the following shortcomings: (1) The Westergaard theoretical analysis adopts a single-layer plate structure model based on Winkler elastic foundation. However, most of the current airport cement concrete pavement base courses are cement-stabilized crushed stone base courses, which have strong base plate properties. The double-layer plate structure on elastic foundation can better reflect the actual pavement structure. Therefore, the Westergaard theoretical analysis will result in poor accuracy of stress response calculation results. At the same time, the Westergaard theoretical analysis cannot adapt to complex load action forms, and the calculation process is complicated and the calculation efficiency is low.

[0003] (2) The pavement structure design is based on controlling cumulative fatigue damage. By initially proposing pavement structure parameters, the cumulative fatigue damage factor is continuously calculated iteratively until the design requirements are met, and finally the pavement structure parameters are obtained. If the stress response is directly analyzed by finite element method in the pavement structure design process, the computer performance requirements are high and the efficiency of finite element method is low, which directly leads to low efficiency of thickness design and affects the design process.

[0004] Precise design of concrete pavement structures is crucial for ensuring safe aircraft operation. Stress response analysis of pavement structures is fundamental to pavement design. Therefore, there is an urgent need for an accurate and efficient stress response calculation method to achieve accurate and rapid calculation of critical load stress, ensuring fast, accurate, and reliable pavement structure design. Summary of the Invention

[0005] One of the objectives of this invention is to provide a design method for airport cement concrete pavement structures based on a stress database, which can effectively improve the calculation efficiency and accuracy of load stress and ensure accurate, efficient and reliable pavement thickness design.

[0006] The second objective of this invention is to provide an airport cement concrete pavement structure design system based on a stress database. This system covers data from multiple aircraft types and operating conditions, and can quickly obtain the critical load stress under any combination of pavement structure parameters, thus significantly improving design efficiency.

[0007] The third objective of this invention is to provide a medium and device that stores an airport cement concrete pavement structure design system based on a stress database, capable of executing programs and quickly obtaining cement concrete pavement thickness design results by inputting proposed pavement information.

[0008] The first aspect of this invention discloses a design method for airport cement concrete pavement structures based on a stress database, which is carried out according to the following steps: S1. Establish a three-dimensional finite element model for calculating aircraft load stress. The model is a finite element analysis model of stress response of a double-layer plate "surface layer-base layer" on a Winkler elastic foundation. S2. Calculate the load stress values ​​of different machine models under different working conditions. The calculation of the load stress values ​​under different working conditions is based on the maximum principal stress at the bottom of the slab. A script is written using a programming language to automatically build a finite element model, submit the calculation model, and analyze the calculation results of the model, thereby realizing the batch automated calculation of stress response analysis of cement concrete pavement. The aircraft types mentioned are the 52 types of aircraft loads listed in Appendix A of the "Design Specification for Cement Concrete Pavement of Civil Airports" (MH / T 5004-2025).

[0009] S3: Extract critical load stress from the load stress of different models under different calculated operating conditions, and construct a critical load stress database: S4: Determine the natural environment of the location of the proposed pavement, the design life of the pavement, the combination of aircraft types within the design life, and the average annual number of flights of each aircraft type; the natural environment includes the natural zoning of the location of the pavement, soil type, the height of the top surface of the pavement subgrade from the groundwater level, and the local standard frost depth, etc.

[0010] S5: Determine the air traffic volume level of the proposed pavement, and preliminarily formulate the structural design parameters of the proposed pavement based on the air traffic volume level; the air traffic volume level is determined based on the type of aircraft operating on the pavement and the average number of flights per year within the design life, and the pavement structural design parameters refer to the "Design Specification for Cement Concrete Pavement of Civil Airports" (MH / T 5004-2025).

[0011] S6: Obtaining the critical load stress of different aircraft models under the proposed pavement structure based on the critical load stress database. ; S7: Computer-type combined aircraft i Main landing gear load on strip j Cumulative number of times at the location N ij With the number of permissible actions N e And calculate the aircraft i strip under main landing gear load jcumulative damage factor of pavement fatigue CDF ij ; S8: The cumulative damage generated by the aircraft combination at each strip of the pavement is obtained by superposition, and the maximum cumulative pavement damage CDF is determined. max Does it satisfy 0.925≤CDF? max If the requirement of ≤1.00 is met, proceed to S9; otherwise, return to S5, redefine the pavement layer thickness, and repeat S5~S7 until the requirement is met. S9: According to the provisions of the "Design Specification for Cement Concrete Pavement of Civil Airport" (MH / T 5004-2025), verify whether the proposed pavement structure parameters meet the value requirements under the corresponding air traffic volume level. If they do not meet the requirements, return to S5, redefine the pavement structure parameters, and repeat S5~S8 until the value requirements are met, and obtain the cement concrete pavement structure design results.

[0012] Specifically, the automated batch calculation of stress response analysis described in S2 mainly includes the following steps: Generate the initial model: Input the initial model parameters into the ABAQUS / CAE software to establish a single-condition finite element model; Generate initial script: Use ABAQUS / CAE's macro recording function to automatically generate a script equivalent to manual modeling during the model building process; Write the target script: Modify the script of the single-condition finite element model above to obtain a script that can realize automated calculation of multiple conditions.

[0013] Furthermore, the script for modifying the single-condition finite element model refers to classifying the aircraft's main landing gear into three categories according to the main landing gear configuration: single-axle dual-wheel, dual-axle dual-wheel, and three-axle dual-wheel. The load application positions for each configuration are divided into the center of the plate, the center of the transverse seam plate edge, and the center of the longitudinal seam plate edge. Target scripts are written for each of these categories to achieve automated batch calculation of load stress.

[0014] Preferably, the load stress mentioned in S3 includes the stress in the slab panel, the stress at the middle of the transverse joint edge, and the stress at the middle of the longitudinal joint edge. The critical load stress is taken as the maximum value of the slab stress, the reduced stress at the middle of the longitudinal joint edge, and the reduced stress at the middle of the transverse joint edge calculated for this model. The reduced stress at the middle of the longitudinal joint edge and the reduced stress at the middle of the transverse joint edge are obtained by multiplying the stress at the middle of the longitudinal and transverse joint edges obtained from the finite element analysis model by the stress reduction factor.

[0015] Preferably, the pavement structure design parameters mentioned in S5 include: surface layer thickness, surface layer modulus, flexural strength and Poisson's ratio of cement concrete; base layer thickness, base layer modulus and Poisson's ratio; subbase material and thickness; reaction modulus of the top surface of the pavement subgrade; local standard frost depth; pavement subgrade dry / wet category and minimum frost protection layer thickness.

[0016] Specifically, S7 refers to 40 strips, each 0.25m wide, on either side of the aircraft's taxiing or runway centerline, on which the aircraft's main landing gear load rests. j Cumulative number of times at the location N ij The calculation formula is: In the formula: -airplane i Standard deviation of the lateral offset distribution of the main landing gear wheel tracks, m; D j —band j The distance between the centerline and the guide line on the pavement, in meters; -airplane i Main landing gear wheels f ( f =1,2,……, F The distance (m) between the centerline and the guide centerline of the pavement. F The number of side-by-side lateral landing gear wheels in the main landing configuration is determined based on the number of side-by-side lateral landing gear wheels in the main landing configuration. F The possible values ​​of ; W — Main landing gear wheel imprint width, in meters; The formula for calculating the permissible number of actions Ne is as follows: In the formula: DF —Design factors, representing the flexural tensile strength and critical load stress of cement concrete. The ratio; k d —Reaction modulus of the top surface of the track bed (MN / m) 3 ); The aircraft i strip under main landing gear load j cumulative damage factor of pavement fatigue CDF ij The calculation method is as follows: When the aircraft has wing main landing gear and fuselage main landing gear, the strip loads under the loads of the wing main landing gear and fuselage main landing gear should be calculated separately. jcumulative fatigue damage factor of the pavement surface: Specifically, the maximum cumulative fatigue damage of the pavement described in S8 CDF max The calculation formula is: Among them, CDF j This refers to the cumulative damage caused by different combinations of aircraft types at various sections of the pavement. The calculation formula is as follows: The second aspect of this invention discloses an airport cement concrete pavement structure design system based on a stress database, comprising: The model building module is used to build a three-dimensional finite element model for calculating aircraft load stress. The input module is used to input the proposed pavement information, which includes the design year, aircraft type combination, average annual number of flights for different aircraft types, and air traffic volume level. The calculation module is used to calculate fixed parameter data and fatigue cumulative damage factor. The fixed parameter data are the load stress values ​​of different models under different working conditions and the critical load stress of different models under the proposed pavement structure. The judgment module is used to determine whether the calculated pavement surface layer thickness meets the minimum value requirement under the corresponding air traffic volume level. If it does not meet the requirement, it returns to the calculation module to recalculate. If it meets the requirement, it passes the conclusion to the output module. The output module is used to output the design results of the airport's cement concrete pavement.

[0017] A third aspect of the present invention discloses a medium storing the pavement structure design system, which, when executed, is used to implement the airport cement concrete pavement structure design method based on a stress database.

[0018] The fourth aspect of the present invention discloses an apparatus including a processor and a memory, wherein the processor is used to execute a computer program stored in the memory, causing the apparatus to execute the airport cement concrete pavement structure design method based on a stress database.

[0019] This invention addresses the problems of time-consuming and inaccurate load stress calculations in traditional design by proposing a method for rapidly obtaining the critical load stress of aircraft loads under arbitrary combinations of pavement structural parameters. Based on the critical load stress calculation, the cumulative fatigue damage of the pavement is obtained, and by controlling the pavement fatigue damage within a certain range, the design thickness of the structural layer is derived. The minimum thickness of the structural layer is then verified according to industry standards, achieving a dual improvement in the efficiency and accuracy of load stress calculations, ensuring accurate, efficient, and reliable pavement thickness design.

[0020] Specifically, the present invention uses a finite element stress response model of a double-layer plate, "surface layer-base layer", based on Winkler elastic foundation to accurately simulate the actual pavement structure, and the calculation results are accurate and reliable. A systematic critical load stress database covering multiple models and working conditions was constructed. Using the five-dimensional quadratic interpolation method, the critical load stress was quickly obtained under any combination of pavement structural parameters, which significantly improved design efficiency. An automated modeling and data extraction method for the finite element analysis model of load stress response was proposed, laying the foundation for subsequent updates to the load stress database and thus enhancing the applicability of pavement structure design methods based on stress databases.

[0021] Overall, the critical stress database constructed by this invention can not only achieve rapid and accurate acquisition of critical stress under different calculation conditions, but also shorten the design cycle of a single project, reduce engineering design costs, and effectively ensure the accuracy, efficiency and reliability of aircraft pavement thickness design, providing technical support for airport engineering construction. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the calculation process for a stress database-based design method for airport cement concrete pavement structures.

[0023] Figure 2 This is the batch processing calculation flow for load stress on cement concrete pavement.

[0024] Figure 3 This is a schematic diagram of the structure of the finite element analysis model for load stress.

[0025] Figure 4 The cumulative fatigue damage distribution curves of the pavement for each aircraft type are shown.

[0026] Figure 5 This is a 3D model of the road surface structure.

[0027] Figure 6 This is a schematic diagram of load application.

[0028] Figure 7 This is a cloud map showing the results of load stress calculation. Detailed Implementation

[0029] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, examples, and comparative examples. The following examples and comparative examples are only used to more clearly illustrate the technical solutions of the present invention, so that those skilled in the art can better understand and utilize the present invention, and are not intended to limit the scope of protection of the present invention.

[0030] The experimental methods, production processes, instruments, and equipment involved in the embodiments and comparative examples of this invention are all conventional names in the art, and are very clear and distinct in the relevant application fields. Those skilled in the art can understand the conventional process steps and apply the corresponding equipment based on the names, and implement them according to conventional conditions or conditions recommended by the manufacturer. Example 1: Design of airport cement concrete pavement structure based on stress database.

[0031] Design of airport cement concrete pavement structures based on stress databases, such as Figure 1 As shown, proceed according to the following steps: S1: Establish a three-dimensional finite element model for calculating aircraft load stress.

[0032] A finite element analysis model of the stress response of a two-layer plate (surface layer-base layer) on a Winkler elastic foundation was constructed, and the mechanical properties were characterized by the foundation reaction modulus. Both the surface layer and the base layer are isotropic elastic bodies, and their mechanical properties are characterized by the elastic modulus and Poisson's ratio. The surface layer has dimensions of 10m × 10m, and the base layer has dimensions of 12m × 12m. The base layer uses a Winkler elastic foundation, simulated by spring elements in the model. The surface layer and base layer have a smooth horizontal contact and a "hard" contact vertically. The element type used is C3D8I.

[0033] The contact conditions between the surface layer and the base layer in the finite element analysis model are: smooth in the horizontal direction and "hard" contact in the vertical direction. The aircraft's action locations in the stress response finite element analysis model are the middle of the transverse joint plate edge, the center of the pavement panel, and the middle of the longitudinal joint plate edge.

[0034] The dimensions of the aircraft load are converted into rectangular load wheel imprints according to the principle of equivalent area. The calculation methods for the length and width of the rectangular load wheel imprints are as follows: In the formula: L- The wheel imprint length (m) of a single wheel of an aircraft's main landing gear; W- The width of the wheel imprint of a single wheel of an aircraft's main landing gear (m); q - Tire pressure of the aircraft's main landing gear (MPa); n w - The number of wheels on a single main landing gear of an aircraft.

[0035] In the finite element analysis model, the mesh sizes for the surface layer and the base layer are 0.1m and 0.2m, respectively, and the solid element type is C3D8I; the Winkler elastic foundation is simulated using spring elements.

[0036] S2: Calculate the load stress values ​​of commonly used models under different working conditions.

[0037] The commonly used aircraft types are the 52 types of aircraft loads listed in Appendix A of the "Design Code for Cement Concrete Pavement of Civil Airports" (MH / T 5004-2025). The main landing gear load of the aircraft is applied to the constructed finite element model, and the load application locations are the center of the plate, the center of the transverse joint plate edge, and the center of the longitudinal joint plate edge.

[0038] Table 1 shows the calculation conditions for different load stresses:

[0039] The load stress calculation under different working conditions uses the maximum principal stress at the bottom of the slab as an indicator. The script is written using Python language to automatically build the finite element model, submit the calculation model, and analyze the calculation results, thus realizing the batch automated calculation of stress response analysis of cement concrete pavement.

[0040] The automated batch calculation of finite element analysis of load stress mainly includes the following steps: (1) Generate the initial model: Input the initial model parameters into the ABAQUS / CAE software to establish a finite element model for a single working condition; (2) Generate initial script: During the process of establishing the finite element model, the recording macro function of ABAQUS / CAE is used to automatically generate a script equivalent to manual modeling. (3) Write the target script: Modify the script for the single working condition to obtain a script that can realize automated calculation for multiple working conditions. The specific process is as follows: Figure 2 As shown. Among them, the script modification for a single working condition refers to dividing the main landing gear into three categories according to the main landing gear configuration: single-axle dual-wheel, dual-axle dual-wheel, and three-axle dual-wheel. The load application position of each configuration is further divided into three cases: the middle of the plate, the middle of the transverse seam plate edge, and the middle of the longitudinal seam plate edge. Target scripts are written for each case to realize the batch automated calculation of load stress.

[0041] S3: Extract critical load stress from the load stress of various models under different calculation conditions, and construct a critical load stress database.

[0042] The load stress includes the stress in the slab panel, the stress at the mid-edge of the transverse joint slab, and the stress at the mid-edge of the longitudinal joint slab. The critical load stress is taken as the maximum value of the slab stress, the reduced stress at the mid-edge of the longitudinal joint slab, and the reduced stress at the mid-edge of the transverse joint slab calculated for this model.

[0043] The reduced stress at the mid-edge of the longitudinal and transverse seams is obtained by multiplying the stresses at the mid-edge of the longitudinal and transverse seams obtained from the finite element analysis model by a stress reduction factor. The stress reduction factor at the mid-edge of the longitudinal seam is 0.3, and the stress reduction factor at the mid-edge of the transverse seam is 0.25.

[0044] The critical load stress database is shown in Table 2.

[0045] S4: Determine the natural environment of the location of the proposed pavement, the design life of the pavement, and the combination of aircraft types and the average number of flights per year for each aircraft type within the design life.

[0046] In this example, the proposed cement concrete pavement has a design life of 30 years and is a runway equipped with a parallel taxiway. Investigation and analysis revealed that the local natural zoning is II4, and the average distance between the top surface of the pavement subgrade and the groundwater level is 2.2m. The subgrade soil is low-liquid-limit clay, and the reaction modulus of the subgrade top surface was determined through field tests after treatment. k 0 = 36 MN / m 3 The local freezing depth is 0.8m.

[0047] The air traffic volume of the designed pavement within its design life was predicted. According to the survey, the main aircraft types and average annual number of flights at the airport are shown in Table 3. According to the "Design Code for Civil Cement Concrete Pavement" (MH / T 5004-2025) (hereinafter referred to as "Code"), the main aircraft types operating on this runway are Category C and above aircraft, and Category E aircraft also operate. Therefore, the air traffic volume level is "Extra Heavy".

[0048] S5: Preliminary structural design parameters for the proposed pavement.

[0049] The air traffic volume level is determined based on the type of aircraft operating on the pavement and the average annual number of flights within the design life. Based on the air traffic volume level, the pavement structure design parameters to be used in the design are selected in accordance with the provisions of the "Design Specification for Cement Concrete Pavement of Civil Airports" (MH / T 5004-2025), including: surface layer thickness, surface layer modulus, flexural strength and Poisson's ratio of cement concrete; base layer thickness, base layer modulus and Poisson's ratio; subbase material and thickness; reaction modulus of the top surface of the subgrade; local standard frost depth; dry and wet subgrade category and minimum frost protection layer thickness.

[0050] In this example, the reaction modulus of the roadbed top surface obtained by field testing... k 0 = 36 MN / m 3 A subbase layer should be installed under the base course. The subbase layer is proposed to be 400mm thick, consisting of graded crushed stone, with an elastic modulus of 500MPa and a Poisson's ratio of 0.35.

[0051] The investigation revealed that the runway bed is of medium moisture type. Since the area where the runway is located is a seasonally frozen soil region, the minimum frost protection layer thickness needs to be calculated. The minimum frost protection layer thickness is proposed to be 0.60m.

[0052] The base course is planned to be a 400mm thick cement-stabilized crushed stone, divided into an upper base course and a lower base course, both 200mm thick; the elastic modulus of the base course is 2500MPa, and the Poisson's ratio is 0.20.

[0053] Based on the "Extra Heavy" air traffic level, the preliminary design for the cement concrete surface layer is 420mm thick, with an elastic modulus of 31GPa, a Poisson's ratio of 0.15, and a design flexural strength of 5.0MPa.

[0054] Therefore, the preliminary pavement structure parameters are shown in Table 4.

[0055] S6: Based on the critical load stress database, obtain the critical load stress of each aircraft type under the proposed pavement structure. .

[0056] There are two methods for obtaining the critical load stress based on the critical load stress database: (1) Extract directly from the critical load stress database; Extracting directly from the critical load stress database means that the proposed pavement structure parameters are one of the calculation conditions when constructing the critical load stress database. In this case, the critical load stress corresponding to the calculation condition is directly extracted from the database.

[0057] (2) Obtained by interpolation based on the critical load stress database.

[0058] Stress obtained by interpolation based on critical load stress database refers to the situation where the proposed pavement structure parameters are not one of the calculation conditions when constructing the critical load stress database. In this case, the critical load stress under this condition is obtained by interpolation.

[0059] Among them, the critical load stress interpolation is a five-dimensional interpolation, and the interpolation method is quadratic interpolation. Five-dimensional interpolation establishes the relationship between the critical load stress and five parameters (five dimensions): surface layer thickness, base layer thickness, surface layer modulus, base layer modulus, and the reaction modulus of the track bed top surface. Quadratic interpolation means that the interpolation function is a quadratic function when performing interpolation in each dimension. y = ax 2 + bx + c In the form of.

[0060] quadratic function y = ax 2 + bx + c The problem contains three unknowns, therefore the solution requires stress data from three nodes in the critical load stress database. The critical load stress is related to five parameters, so a single stress interpolation requires at most three [unclear] nodes. 5 =Data from 243 nodes.

[0061] Select nodes near the point to be interpolated. For each dimension of a node, select the three nodes closest to the value of the dimension to be interpolated.

[0062] Critical load stress interpolation involves substituting the three nodes obtained above into a quadratic interpolation function to obtain... a , b and c This allows us to obtain the critical load stress values ​​at the interpolation nodes.

[0063] The pavement structure parameters initially proposed in this design are not nodes in the critical load stress database. It is necessary to interpolate from the database to obtain the critical load stress for each aircraft type under this operating condition. Specifically, the critical load stress for each aircraft type under the initially proposed pavement structure in this example is shown in Table 5. Furthermore, the allowable number of loading cycles for the three aircraft types were calculated based on the fatigue equations in the "Design Code for Cement Concrete Pavement of Civil Airports" (MH / T 5004-2025). N e The calculation results are shown in Table 5:

[0064] S7: Calculating the aircraft i strip under main landing gear load j cumulative damage factor of pavement fatigue CDF ij。

[0065] Calculate the aircraft using the formula below. i Main landing gear load on strip j Cumulative number of times at the location N ij The strips consist of 40 strips, each 0.25m wide, on either side of the aircraft's taxiing or runway centerline. In the formula: -airplane i Standard deviation of the lateral offset distribution of the main landing gear wheel tracks, m; D j —band j The distance between the centerline and the guide line on the pavement, in meters; -airplane i Main landing gear wheels f ( f =1, 2, ..., F The distance (m) between the centerline and the guide centerline of the pavement. F The number of side-by-side lateral landing gear wheels in the main landing configuration is determined based on the number of side-by-side lateral landing gear wheels in the main landing configuration. F The possible values ​​of ; W — Main landing gear wheel imprint width, m.

[0066] Calculate the aircraft using the formula below. i The allowable number of main landing gear loads at strip j N e : In the formula: DF —Design factor, which is the ratio of the flexural tensile strength of cement concrete to the critical load stress; k d —Reaction modulus of the top surface of the track bed (MN / m) 3 ); airplane i strip under main landing gear load j cumulative damage factor of pavement fatigue CDF ij The calculation method is as follows: when the aircraft has wing main landing gear and fuselage main landing gear, the strip loads under the loads of the wing main landing gear and fuselage main landing gear should be calculated separately. j cumulative fatigue damage factor of the pavement surface: .

[0067] S8: Calculate the maximum cumulative fatigue damage (CDF) of the pavement. max .

[0068] The superimposed combination of models is used in the noodle belt. j Cumulative damage CDF generated at the site j Determine the maximum cumulative fatigue damage of the pavement. CDF max Does it satisfy 0.925≤ CDF max If the requirement of ≤1.00 is met, proceed to S9; otherwise, return to S4, readjust the pavement layer thickness, and repeat S4~S7 until the requirement is met.

[0069] The method for calculating the cumulative damage (CDF) generated by the aircraft combination at various strips of the pavement is as follows: .

[0070] The maximum cumulative fatigue damage (CDFmax) of the pavement is shown below: .

[0071] The cumulative fatigue damage distribution curve of the pavement under the combined action of different aircraft types was calculated and obtained as follows: Figure 4 As shown, CDF max =0.959.

[0072] S9: Verification.

[0073] As shown in Table 3.0.8 of the standard, the reaction modulus of the top surface of the track bed when the air traffic volume level is extra heavy is... k d It should be no less than 60MN / m 3 Current reaction modulus of the top surface of the roadbed k 0 = 36MN / m 3 The proposed design uses a 400mm thick layer of graded crushed stone. According to clause 3.0.7 of the standard, this... k d =68MN / m 3 It meets the specifications, the thickness of the subbase also meets the requirement of a minimum value of 1500mm, and the values ​​of modulus and Poisson's ratio are also within the range specified in the specifications.

[0074] According to Table 4.3.2-1 of the specification, when the air traffic volume level is extra heavy, the minimum thickness of the base layer is 300mm. The preliminary proposed base layer thickness is 400mm, which meets the minimum base layer thickness requirement. The modulus is 2500MPa and the Poisson's ratio is 0.20, both of which are within the range given in the specification.

[0075] According to Clause 3.0.10 and Table 4.5.2 of the standard, when the air traffic volume is extra heavy, the design flexural tensile strength of cement concrete should not be less than 5.0 MPa and the thickness should not be less than 340 mm. The initial proposed surface layer thickness is 420 mm, the elastic modulus is 31 GPa, the Poisson's ratio is 0.15, and the design flexural tensile strength is 5.0 MPa, which meets the requirements.

[0076] According to Appendix B of the standard, the runway subgrade is classified as medium wet. Since the runway area is located in a seasonally frozen soil region, a minimum frost protection layer thickness calculation is required. The initial minimum frost protection layer thickness is proposed to be 0.60m, and the calculation confirms that it meets the requirements.

[0077] The CDF of the pavement structure was calculated. Within the design life, the maximum CDF generated by the combination of aircraft on the initial structure was 0.959, which meets the requirement of being within the range of 0.925 to 1.00.

[0078] In summary, the initially proposed pavement structure parameters meet the requirements of the specifications for the values ​​of parameters for each structural layer, and the design is now complete. Therefore, the results of this pavement structure design are shown in Table 6. Example 2: Traditional finite element design method.

[0079] Using traditional finite element design methods, a three-dimensional finite element model of the initially proposed pavement structure is created, such as... Figure 5 As shown. Appropriate aircraft loads are applied to the pavement structure, such as... Figure 6 As shown, after submission and calculation, the load stress cloud diagram was obtained, as follows. Figure 7 As shown. The maximum bending tensile stress at the bottom of the plate at this point is extracted and substituted into the fatigue equation given in the standard to obtain the corresponding allowable number of loading cycles. The above method is used for each model to obtain the stress and thus the allowable number of loading cycles, and the corresponding CDF is obtained according to the calculation method given in the standard.

[0080] The traditional design method was compared with the stress database-based structural design method proposed in this invention. The time taken for six calculations was recorded, and the results are shown in Table 7.

[0081] Comparative analysis revealed that the method proposed in this invention significantly reduces computational time costs, thereby improving the efficiency of pavement structure design.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A design method for airport cement concrete pavement structures based on a stress database, comprising the following steps: S1: Establish a three-dimensional finite element model for calculating aircraft load stress. The model is a finite element analysis model of the stress response of a double-layer plate "surface layer-base layer" on a Winkler elastic foundation. S2: Calculate the load stress values ​​of different machine models under different working conditions. The calculation of the load stress values ​​under different working conditions is based on the maximum principal stress at the bottom of the slab. A script is written using a programming language to automatically establish a finite element model, submit the calculation model, and analyze the calculation results of the model, thereby realizing the batch automated calculation of stress response analysis of cement concrete pavement. S3: Extract critical load stress from the load stress of different models under different calculated operating conditions, and construct a critical load stress database: S4: Determine the natural environment of the location of the proposed pavement, the design life of the pavement, the combination of aircraft types within the design life, and the average annual number of flights of each aircraft type; S5: Determine the air traffic volume level of the proposed pavement, and preliminarily formulate the structural design parameters of the proposed pavement based on the air traffic volume level; S6: Obtaining the critical load stress of different aircraft models under the proposed pavement structure based on the critical load stress database. ; S7: Computer-type combined aircraft i Main landing gear load on strip j Cumulative number of times at the location N ij With the number of permissible actions N e and calculate the aircraft i strip under main landing gear load j cumulative damage factor of pavement fatigue CDF ij ; S8: The cumulative damage generated by the aircraft combination at each strip of the pavement is obtained by superposition, and the maximum cumulative pavement damage CDF is determined. max Does it satisfy 0.925≤CDF? max If the requirement of ≤1.00 is met, proceed to S9; otherwise, return to S5, redefine the pavement layer thickness, and repeat S5~S7 until the requirement is met. S9: Verify whether the proposed pavement structure parameters meet the value requirements under the corresponding air traffic volume level. If not, return to S5, redefine the pavement structure parameters, and repeat S5~S8 until the value requirements are met, and obtain the cement concrete pavement structure design results.

2. The design method according to claim 1, wherein the automated batch calculation of stress response analysis in step S2 mainly includes the following steps: Generate the initial model: Input the initial model parameters into the ABAQUS / CAE software to establish a single-condition finite element model; Generate initial script: Use ABAQUS / CAE's macro recording function to automatically generate a script equivalent to manual modeling during the model building process; Write the target script: Modify the script of the single-condition finite element model above to obtain a script that can realize automated calculation of multiple conditions.

3. The design method according to claim 2, wherein the script for modifying the single-condition finite element model refers to classifying the main landing gear of the aircraft into three categories according to the main landing gear configuration: single-axle dual-wheel, dual-axle dual-wheel, and three-axle dual-wheel. The load application positions of each configuration are divided into the middle of the plate, the middle of the transverse seam plate edge, and the middle of the longitudinal seam plate edge. Target scripts are written for each of these categories to realize batch automated calculation of load stress.

4. The design method according to claim 1, wherein the load stress in S3 includes the stress in the slab panel, the stress at the middle of the transverse joint edge, and the stress at the middle of the longitudinal joint edge; the critical load stress is taken as the maximum value of the stress in the slab panel, the reduced stress at the middle of the longitudinal joint edge, and the reduced stress at the middle of the transverse joint edge; the reduced stress at the middle of the longitudinal joint edge and the reduced stress at the middle of the transverse joint edge are obtained by multiplying the stress at the middle of the longitudinal and transverse joint edges obtained from the finite element analysis model by a stress reduction factor.

5. The design method according to claim 1, wherein the pavement structure design parameters in S5 include: Surface layer thickness, surface layer modulus, flexural strength and Poisson's ratio of cement concrete; base layer thickness, base layer modulus and Poisson's ratio; The reaction modulus of the top surface of the track bed.

6. The design method according to claim 1, wherein the strips in S7 are 40 strips with a width of 0.25m on both sides of the aircraft taxiing or runway centerline, and the main landing gear load is distributed on the strips. j Cumulative number of times at the location N ij The calculation formula is: In the formula: -airplane i Standard deviation of the lateral offset distribution of the main landing gear wheel tracks, m; D j —band j The distance between the centerline and the guide line on the pavement, in meters; -airplane i Main landing gear wheels f ( f =1,2,……, F The distance (m) between the centerline and the guide centerline of the pavement. F The number of side-by-side lateral landing gear wheels in the main landing configuration is determined based on the number of side-by-side lateral landing gear wheels in the main landing configuration. F The possible values ​​of ; W — Main landing gear wheel imprint width, in meters; The formula for calculating the permissible number of actions Ne is as follows: In the formula: DF —Design factors, representing the flexural tensile strength and critical load stress of cement concrete. The ratio; k d —Reaction modulus of the top surface of the track bed (MN / m) 3 ); The aircraft i strip under main landing gear load j cumulative damage factor of pavement fatigue CDF ij The calculation method is as follows: When the aircraft has wing main landing gear and fuselage main landing gear, the strip loads under the loads of the wing main landing gear and fuselage main landing gear should be calculated separately. j Cumulative fatigue damage factor of the pavement surface: 。 7. The design method according to claim 1, wherein the maximum cumulative fatigue damage of the pavement in step S8 is... CDF max The calculation formula is: in, CDF j This refers to the cumulative damage caused by different combinations of aircraft types at various sections of the pavement. The calculation formula is as follows: 。 8. A stress database-based airport cement concrete pavement structure design system, comprising: The model building module is used to build a three-dimensional finite element model for calculating aircraft load stress. The input module is used to input the proposed pavement information, which includes the design year, aircraft type combination, average annual number of flights for different aircraft types, and air traffic volume level. The calculation module is used to calculate fixed parameter data and fatigue cumulative damage factor. The fixed parameter data are the load stress values ​​of different models under different working conditions and the critical load stress of different models under the proposed pavement structure. The judgment module is used to determine whether the calculated pavement surface layer thickness meets the minimum value requirement under the corresponding air traffic volume level. If it does not meet the requirement, it returns to the calculation module to recalculate. If it meets the requirement, it passes the conclusion to the output module. The output module is used to output the design results of the airport's cement concrete pavement.

9. A medium storing the pavement structure design system of claim 8, wherein the pavement structure design system, when executed, is used to implement the airport cement concrete pavement structure design method based on a stress database as described in any one of claims 1 to 7.

10. An apparatus comprising a processor and a memory, the processor being configured to execute a computer program stored in the memory, causing the apparatus to perform the airport cement concrete pavement structure design method based on a stress database as described in any one of claims 1 to 7.

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