A method for establishing a microscopic finite element model of hybrid fiber concrete

Abstract

The invention discloses a method for establishing a mesoscopic finite element model of a mixed fiber concrete. Aggregates are randomly generated in a set area, and an intrusion judgment is performed between the newly generated aggregates and the generated aggregates. If no intrusion occurs, the cumulative volume rate of the aggregates is calculated until the volume rate requirement is met. After the aggregate generation is completed, the first fiber is randomly generated according to fiber-related parameters, and an intrusion judgment is performed between the fiber and the aggregate, and between the fibers. If no intrusion occurs, the cumulative volume rate of the fibers is calculated until the volume rate requirement is met. Mesoscopic component units are identified by using Fortran programming to complete the establishment of a mesoscopic finite element model of a mixed fiber concrete. The invention incorporates mixed fibers on the basis of a mesoscopic aggregate concrete model, and solves the problem of grid division. The overall model adopts hexahedral grid division, which solves the problems of long tetrahedral grid calculation time and low convergence of calculation results, effectively improves the calculation efficiency and accuracy of the finite element model, and at the same time makes the contact between the mesoscopic components better, and can be applied to various static and dynamic experimental simulations.

Description

Technical Field

[0001] The invention relates to a method for establishing a hybrid fiber concrete microscopic finite element model, belonging to the technical field of fiber microscopic concrete simulation. Background Art

[0002] In recent years, many scholars at home and abroad have added a variety of fibers with different properties and sizes into concrete to form a high-performance composite concrete material, with the aim of optimizing the advantages of each fiber and improving the overall effect. Although mechanical testing is the most direct way to understand the constitutive relationship and mechanical properties of fiber concrete, this method can only analyze the reinforcement effect of fibers through test results. Considering the defects of physical and mechanical tests, it is impossible to analyze the reinforcement mechanism of fibers on the mechanical properties of concrete according to the force conditions of fibers. At the same time, it is difficult to conduct a macroscopic analysis of the effect of bonding slip during the pull-out process after the fibers are stressed. The use of finite element software to perform numerical simulation of fiber concrete can make up for the limitations of physical tests. At present, there is a lack of control over the volume ratio of aggregates and fibers at different sizes in the numerical model of hybrid fiber concrete. There are few models that consider aggregates, mortar, ITZ, and hybrid fibers at the same time. After the complex fiber concrete mesoscopic model is established, there is a lack of technology for further meshing the complex mesoscopic model. Therefore, it is of great theoretical and engineering significance to highly restore the mesoscopic components of hybrid fiber concrete at the mesoscopic scale and establish a finite element model of hybrid fiber concrete that can be directly numerically calculated. Summary of the invention

[0003] The object of the present invention is to provide a modeling method of a hybrid fiber concrete mesoscopic finite element model containing two kinds of fibers based on Monte Carlo which is simple to operate, flexible and has high result accuracy.

[0004] The technical solution to achieve the purpose of the present invention is: a modeling method for a hybrid fiber concrete microscopic finite element model containing two types of fibers, the steps are as follows:

[0005] S1: Taking the cylinder as an example, the size of the cylindrical hybrid fiber concrete matrix is ​​determined. The cross-sectional radius of the cylinder is R 基体 , the height of the cylindrical concrete is h, then the volume of the concrete matrix is:

[0006] V 基体 =π·R 基体 2 ·h

[0007] First, the volumes of the three aggregates are calculated: V1, V2, and V3; then the volumes of the two single fibers are calculated: V4 and V5.

[0008] S2: Complete the setting of relevant parameters required for aggregates and fibers. First, randomly generate aggregates in the specified area. Except for the first generated aggregate, each subsequent generated aggregate needs to be judged for intrusion with the generated aggregates. If none of them invade, the aggregate is generated and the volume rate is calculated. Otherwise, the aggregate is deleted and regenerated to perform intrusion judgment until the cumulative volume rate of the generated aggregates reaches the set value.

[0009] The formula for calculating the aggregate volume ratio is as follows:

[0010]

[0011] S3: Determine the coordinates of the first endpoint A of each fiber, the process is as follows:

[0012] First, use the rand function rand(n1+n2,1), which represents the generation of n1+n2 random numbers between 0 and 1, and then determine the three coordinates of points A1 and A2 in the Cartesian coordinate system:

[0013] Randomly generate the x coordinate of the first endpoint A1 of each fiber of the first type:

[0014] X A1 =L1+rand(n1+n2,1)·(a-2L1)

[0015] Randomly generate the y coordinate of the first endpoint A1 of each fiber of the first type:

[0016] Y A1 =L1+rand(n1+n2,1)·(b-2L1)

[0017] Randomly generate the z coordinate of the first endpoint A1 of each fiber of the first type:

[0018] Z A1 =L1+rand(n1+n2,1)·(c-2L1)

[0019] Randomly generate the x coordinate of the first endpoint A2 of each fiber of the second type:

[0020] X A2 =L2+rand(n1+n2,1)·(a-2L2)

[0021] Randomly generate the y coordinate of the first endpoint A2 of each fiber of the second type:

[0022] Y A2 =L2+rand(n1+n2,1)·(b-2L2)

[0023] Randomly generate the z coordinate of the first endpoint A2 of each fiber of the second type:

[0024] Z A2 =L2+rand(n1+n2,1)·(c-2L2)

[0025] The second end point B and the midpoint C of each fiber are randomly generated based on the Monte Carlo method, and the hybrid mathematical modeling is finally completed. The process is as follows:

[0026] Extract the first fiber in the Monte Carlo cycle and randomly select its angle θ with the x-axis x :

[0027] θ x =rand(1)·2π

[0028] Its angle with the y-axis is θ y :

[0029] θ y =rand(1)·2π

[0030] Its angle with the z-axis is θ z :

[0031] θ z =rand(1)·2π

[0032] Thus, the coordinates of the second end point B1 of the fiber can be obtained. The values ​​of the x, y, and z coordinates of point B1 are:

[0033] X B1 =X A1 +L1·cos(θ x )

[0034] Y B1 =Y A1 +L1·cos(θ y )

[0035] Z B1 =Z A1 +L1·cos(θ z )

[0036] The coordinates of the midpoint C of the fiber can also be obtained. The x, y, and z coordinates of point C are:

[0037] X C1 =X A1 +L1·cos(θ x ) / 2

[0038] Y C1 =Y A1 +L1·cos(θ y ) / 2

[0039] Z C1 =ZA1 +L1·cos(θ z ) / 2

[0040] S4: Generate the first type of fiber in the specified area. The first fiber only needs to be judged for intrusion with the existing aggregate. Each subsequent fiber needs to be judged for intrusion with the generated aggregate and the generated fiber. If neither of them invades, the fiber is generated and the volume rate is calculated. Otherwise, the fiber is deleted and the fiber is regenerated for intrusion judgment until the cumulative volume rate of the generated fibers reaches the set value. The generation method of the second fiber is the same as that of the first fiber.

[0041] The fiber volume fraction calculation formula is as follows:

[0042]

[0043] S5: After the center coordinates, radius and linear fiber coordinates of the aggregate are output, the mesoscopic component units are identified using Fortran programming, and the fiber concrete mesoscopic model is directly projected into the homogeneous finite element model of the container; the establishment of the hybrid fiber concrete mesoscopic finite element model is completed.

[0044] The present invention in step S1:

[0045] Three types of aggregate volumes, aggregate volume calculation method:

[0046]

[0047] V1, V2, and V3 refer to the volume of the first, second, and third aggregates, respectively. D1, D2, and D3 are the diameter parameters of the three aggregates, respectively. S1, S2, and S3 are the number of the three aggregates, respectively. The volume of a single fiber of the two fibers is calculated as follows:

[0048] V4=S 截面积 A×L1×S4

[0049] V5=S 截面积 B×L2×s5

[0050] V4 is the volume of the first type of fiber, V5 is the volume of the second type of fiber; L1 and L2 are the lengths of the two fibers respectively, s4 and s5 are the number of the two fibers respectively.

[0051] Preferably, in step S2 of the present invention: the relevant parameters of the aggregate include three groups of continuously graded aggregate diameter ranges D1∈[dia1,dia2], D2∈(dia2,dia3], D3∈(dia3,dia4], and the cumulative volume of aggregates in each group of particle size ranges is V1, V2, and V3; an aggregate array file is established, that is, the number of aggregates is generated: the number of aggregates in the range of D1 is s1, the number of aggregates in the range of D2 is s2, the number of aggregates in the range of D3 is s3, and the diameter R of the aggregate is 骨料 , the coordinates of the center of the aggregate (X 骨料 , Y 骨料 , Z 骨料 );

[0052] The relevant parameters of the fiber include the length range of the two fibers L1∈[len1,len2], L2∈[len3,len4], the number of the first fiber is s4, and the cross-sectional area is S 截面积A , the number of the second type of fibers is s5, and the cross-sectional area is S 截面积B .

[0053] Preferably, in step S2 of the present invention, the method for determining whether intrusion occurs between aggregates is as follows:

[0054] If the distance between the coordinates of the center of the first aggregate and the coordinates of the center of the second aggregate in the established three-dimensional concrete micro-model is greater than or equal to the sum of the maximum radii of the aggregates, it is determined that they do not intersect; otherwise, they are determined to intersect, that is, whether the aggregate particles intrude is determined according to the following formula:

[0055]

[0056] (X 骨料i , Y 骨料i , Z 骨料i ) is the coordinate of the center of the first aggregate sphere, (X 骨料n , Y 骨料n , Z 骨料n ) is the coordinate of the center of the second aggregate sphere.

[0057] Preferably, in step S4 of the present invention, the method for determining whether the aggregate and the fiber have intrusion is as follows:

[0058] Aggregate and fiber intrusion determination only requires determining that the shortest distance between the fiber and the center of the aggregate sphere is greater than or equal to the aggregate radius, that is, determining the distance between the two end points and the midpoint and the center of the aggregate sphere. The determination process is as follows:

[0059] Take the coordinates of the center of the aggregate sphere (X 骨料i ,Y 骨料i ,Z 骨料i ), the distance between the center of the ball and the first end point of the fiber:

[0060]

[0061] The distance between the center of the sphere and the second end point of the fiber:

[0062]

[0063] Distance between sphere center and fiber midpoint:

[0064]

[0065] (X A1 , Y A1 , Z A1 ) is the coordinate of the first endpoint, (X B1 , Y B1 , Z B1 ) is the coordinate of the first endpoint, (X C1 , Y C1 , Z C1 ) are the coordinates of the fiber midpoint.

[0066] Preferably, in step S4 of the present invention, the method for determining whether the fiber-to-fiber intrusion phenomenon occurs is as follows: it is only necessary to determine that the line-fiber vector product is not 0, and the determination process is as follows:

[0067] Take the first fiber coordinates and the two end points A1(X A1 ,Y A1 ,Z A1 ), B1(X B1 ,Y B1 ,Z B1 )

[0068] Take the coordinates of the second fiber and the two end points A2(X A2 ,Y A2 ,Z A2 ), B1(X B2 ,Y B2 ,Z B2 )

[0069]

[0070] Preferably, in step S4 of the present invention: the homogeneous finite element model of the container can be generated by finite element software such as ANSYS / APDL or HyperMesh, and the homogeneous finite element model of the container is exported in the form of a k-file.

[0071] Preferably, the present invention uses Fortran programming to identify the micro-component units, and the identification method is as follows:

[0072] a. Use Fortran language in Visual Studio software to identify and define the aggregate coordinate file format and the k file of the homogeneous finite element model; the identification and definition contents mainly include: ① the number of aggregates of different diameters s1, s2, s3, the array format of aggregate diameter and aggregate sphere center coordinates; ② the total number of units E, the total number of nodes N, and the array format of k file units and nodes of the homogeneous finite element model k file;

[0073] b. Calculate the center coordinates (X E , Y E , Z E ), determine its distance to the first aggregate sphere center (X 骨料1 , Y 骨料1 , Z 骨料1 ) is smaller than the radius of the first aggregate, the unit is determined as the aggregate + interface group Part_1, otherwise it is the mortar group Part_2; then the distance to the second aggregate center (X 骨料2 , Y 骨料2 , Z 骨料2 ), and so on, until all aggregates have been gone through;

[0074] c. Repeat the operation in b to calculate the center coordinates (X E , Y E , Z E ), determine its distance to the first aggregate sphere center (X 骨料1 , Y 骨料1 , Z 骨料1 ), if the distance is less than the radius of the first aggregate minus the interface thickness T, the unit is identified as aggregate group Part_3, and only the interface remains in Part_1, which is the interface group; hence, the identification of different micro-component units is completed, and the finite element models of the interface (Part_1), mortar (Part_2) and aggregate (Part_3) are generated.

[0075] d. Read the starting point coordinates (X 纤维1-start , Y 纤维1-start , Z 纤维1-start ) and the end point coordinate X 纤维1-end , Y 纤维1-end , Z 纤维1-end ), link161 unit is used to establish the finite element model of the fiber. The first fiber is Part_4 and the second fiber is Part_5.

[0076] Finally, based on the determined concrete size, aggregate quantity and fiber quantity, it is determined whether the fiber volume ratio meets the requirements.

[0077] What are the beneficial effects of the present invention:

[0078] Most of the existing concrete meso-modeling technologies only have model establishment, but no meshing, and thus cannot perform further finite element analysis. Most finite element modeling and analysis only use tetrahedral meshing, which takes a long time to calculate. The patent of the present invention adopts modeling mesh integration and uses background mapping method to perform hexahedral meshing on the model. After simulation analysis, the calculation time of the same model with hexahedral mesh is 100 times shorter than that with tetrahedral mesh, and the simulation results have better convergence. The existing meso-concrete modeling technology only considers the aggregate mortar interface, and does not consider the modeling and meshing methods of mixed fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 It is a finite element model diagram of the mixed fiber concrete aggregate of the present invention;

[0080] Figure 2 It is a finite element model diagram of hybrid fiber concrete fiber of the present invention;

[0081] Figure 3 It is a finite element model diagram of the hybrid fiber concrete section of the present invention. DETAILED DESCRIPTION

[0082] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to the contents described.

[0083] Example 1

[0084] The present invention uses Fortran language combined with ANSYS / LS-DYNA finite element software to simulate and obtain a hybrid fiber concrete finite element model as shown in the figure. Figure 1 shown.

[0085] The detailed steps include:

[0086] Step 1: Generate hybrid fiber concrete numerical model information using Fortran language in Visual Studio software: Use Fortran language to randomly generate spheres of different particle size ranges in the specified area. Since the geometric shape of aggregate is approximately sphere, the random sphere can be considered as aggregate. On this basis, randomly generate two different sizes of line segments. Since the geometric shape of fiber is approximately line, the random line segment can be considered as hybrid fiber. The specific process is as follows:

[0087] Step 1.1: Use Fortran language to declare the relevant parameter settings required for aggregate and fiber.

[0088] The relevant parameters of aggregates include three groups of continuously graded aggregate diameter ranges D1∈[dia1,dia2], D2∈(dia2,dia3], D3∈(dia3,dia4], and the cumulative volume of aggregates in each size range is V1, V2, and V3; an aggregate array file is established, that is, the number of aggregates is generated: the number of aggregates in the range of D1 is s1, the number of aggregates in the range of D2 is s2, the number of aggregates in the range of D3 is s3, and the diameter of the aggregate R 骨料 , the coordinates of the center of the aggregate (X 骨料 , Y 骨料 , Z 骨料 ); The fiber parameters include the length ranges of the two fibers L1∈[len1,len2], L2∈[len3,len4], the number of the first fiber is s4, and the cross-sectional area is S 截面积A , the number of the second type of fibers is s5, and the cross-sectional area is S 截面积B .

[0089] Step 1.2: Randomly place aggregates in the specified area. Except for the first generated aggregate, each subsequent aggregate must be judged for intrusion with the generated aggregates. If none of them invade, the aggregate is generated and the volume rate is calculated. Otherwise, the aggregate is deleted and the aggregate is placed again for intrusion judgment until the cumulative volume rate of the generated aggregate reaches the set value.

[0090] a) The method of random placement of aggregate is as follows:

[0091] According to the Monte Carlo principle, a random number n is declared, whose value is 0-1, and the diameter parameter of the randomly generated aggregate is controlled by the random number:

[0092] R 骨料 =dia1+(dia2-dia1)·n

[0093] According to the size parameters of aggregate and container, the coordinates of the center of aggregate sphere (X 骨料 , Y 骨料 , Z 骨料 ).

[0094] b) The method for judging whether intrusion occurs between aggregates is as follows:

[0095] If the distance between the generated aggregate sphere center coordinates in the established three-dimensional concrete micro-model and the aggregate sphere center coordinates being determined is greater than the sum of the two aggregate radii, it is determined that they do not intersect; otherwise, it is determined that they intersect, that is, whether the aggregate particles intrude is determined according to the following formula:

[0096]

[0097] Calculation method of aggregate volume ratio:

[0098]

[0099] Step 1.3: Randomly place mixed fibers in the specified area and make an intrusion determination on the fibers. If none of them intrude, the fiber is generated.

[0100] a) The method of random fiber placement is as follows:

[0101] First, use the rand function rand(n1+n2,1), which represents the generation of n1+n2 random numbers between 0 and 1, and then determine the three coordinates of points A1 and A2 in the Cartesian coordinate system:

[0102] Randomly generate the x coordinate of the first endpoint A1 of each fiber of the first type:

[0103] X A1 =L1+rand(n1+n2,1)·(a-2L1)

[0104] Randomly generate the y coordinate of the first endpoint A1 of each fiber of the first type:

[0105] Y A1 =L1+rand(n1+n2,1)·(b-2L1)

[0106] Randomly generate the z coordinate of the first endpoint A1 of each fiber of the first type:

[0107] Z A1 =L1+rand(n1+n2,1)·(c-2L1)

[0108] Randomly generate the x coordinate of the first endpoint A2 of each fiber of the second type:

[0109] X A2 =L2+rand(n1+n2,1)·(a-2L2)

[0110] Randomly generate the x coordinate of the first endpoint A2 of each fiber of the second type:

[0111] Y A2 =L2+rand(n1+n2,1)·(b-2L2)

[0112] Randomly generate the z coordinate of the first endpoint A2 of each fiber of the second type:

[0113] Z A2 =L2+rand(n1+n2,1)·(c-2L2)

[0114] Based on the Monte-Carlo method, the second end point B and the midpoint C of each fiber are randomly generated, and finally the hybrid fiber mathematical modeling is completed. The process is as follows:

[0115] Extract the first fiber in the Monte Carlo cycle and randomly select its angle θ with the x-axis x :

[0116] θ x =rand(1)·2π

[0117] Its angle with the y-axis is θ y :

[0118] θ y =rand(1)·2π

[0119] Its angle with the z-axis is θ z :

[0120] θ z =rnad(1)·2π

[0121] Thus, the coordinates of the second end point B1 of the fiber can be obtained. The values ​​of the x, y, and z coordinates of point B1 are:

[0122] X B1 =X A1 +L1·cos(θ x )

[0123] Y B1 =Y A1 +L1·cos(θ y )

[0124] Z B1 =Z A1 +L1·cos(θ z )

[0125] The coordinates of the midpoint C of the fiber can also be obtained. The x, y, and z coordinates of point C are:

[0126] X C1 =X A1 +L1·cos(θ x ) / 2

[0127] Y C1 =Y A1 +L1·cos(θ y ) / 2

[0128] Z C1 =Z A1 +L1·cos(θ z ) / 2

[0129] (b) After the fiber is placed, an intrusion assessment is required. The assessment includes the intrusion assessment between aggregate and fiber, and between fibers. The process is as follows:

[0130] The first fiber generated only needs to complete one intrusion judgment between the fiber and the aggregate, and each subsequent fiber needs to complete a secondary intrusion judgment between the fiber and the aggregate, and between the fibers. If none of them intrude, the fiber is generated and the volume rate is calculated, otherwise the fiber is deleted and the fiber is regenerated for intrusion judgment until the cumulative volume rate of the generated fibers reaches the set value; the generation method of the second fiber is the same as the generation method of the first fiber, the only difference is that the first fiber generated also needs to complete the secondary intrusion judgment between the fiber and the aggregate, and between the fibers.

[0131] Among them, the determination of aggregate and fiber intrusion only needs to determine that the shortest distance between the fiber and the center of the aggregate sphere is greater than or equal to the aggregate radius, that is, to determine the distance between the two end points and the midpoint and the center of the aggregate sphere. The determination process is as follows:

[0132] Take the coordinates of the center of the aggregate sphere (X 骨料i ,Y 骨料i ,Z 骨料i ), the distance between the center of the ball and the first end point of the fiber:

[0133]

[0134] Distance between the center of the sphere and the second end point of the fiber:

[0135]

[0136] Distance between sphere center and fiber midpoint:

[0137]

[0138] The fiber-to-fiber intrusion determination only requires that the line-fiber vector product is not 0. The determination process is as follows:

[0139] Take the first fiber coordinates and the two end points A1(X A1 ,Y A1 ,Z A1 ), B1(X B1 ,Y B1 ,Z B1 )

[0140] Take the coordinates of the second fiber and the two end points A2(X A2 ,Y A2 ,Z A2 ), B2(X B2 ,Y B2 ,Z B2 )

[0141]

[0142] Fiber volume fraction calculation method:

[0143] V4=S截面积 A×L1×s4

[0144] V5=S 截面积 B×L2×s5

[0145] Fiber volume ratio:

[0146]

[0147] Step 1.4: Export the data containing all aggregate diameters R 骨料 and the spherical center coordinates of the aggregate (X 骨料 , Y 骨料 , Z 骨料 ) array file, named dat1, which contains the starting point coordinates (X 纤维1-start , Y 纤维1-start , Z 纤维1-start ) and the end point coordinate X 纤维1-end , Y 纤维1-end , Z 纤维1-end ) array file, named dat2.

[0148] Step 2: After the center coordinates, radius and linear fiber coordinates of the aggregate are output, Fortran programming is used to identify the mesoscopic component units, and the fiber concrete mesoscopic model is directly projected into the homogeneous finite element model of the container.

[0149] The homogeneous finite element model of the container can be generated by ANSYS / LS-DYNA or HyperMesh finite element software, and the homogeneous finite element model of the container can be exported in the form of a k-file.

[0150] Fortran programming is used to identify the micro-component units. The identification method is as follows:

[0151] Step 2.1: Use Fortran language in Visual Studio software to identify and define the aggregate coordinate file format and the k file of the homogeneous finite element model; the identification and definition contents are mainly: ① the number of aggregates with different diameters s1, s2, s3, the array format of aggregate diameter and aggregate sphere center coordinates; ② the total number of units E and the total number of nodes N of the k file of the homogeneous finite element model, and the array format of k file units and nodes.

[0152] Step 2.2: Calculate the center coordinates (X E , Y E , Z E), determine the distance to the center of the first aggregate (X aggregate 1, Y aggregate 1, Z aggregate 1). If the distance is less than the radius of the first aggregate, the unit is determined as the aggregate + interface group Part_1, otherwise it is the mortar group Part_2; then determine the distance to the center of the second aggregate (X aggregate 1, Y aggregate 1, Z aggregate 1) according to the above method. 骨料2 , Y 骨料2 , Z 骨料2 ), and so on, until all aggregates are gone through.

[0153] Step 2.3: Repeat the operation in step b to calculate the center coordinates (X E , Y E , Z E ), determine its distance to the first aggregate sphere center (X 骨料1 , Y 骨料1 , Z 骨料1 ), if the distance is less than the radius of the first aggregate minus the interface thickness T, the unit is identified as aggregate group Part_3, and only the interface remains in Part_1, which is the interface group; hence, the identification of different micro-component units is completed, and the finite element models of the interface (Part_1), mortar (Part_2) and aggregate (Part_3) are generated.

[0154] Step 2.4: Read the starting point coordinates (X 纤维1-start , Y 纤维1-start , Z 纤维1-start ) and the end point coordinate X 纤维1-end , Y 纤维1-end , Z 纤维1-end ), link161 unit is used to establish the finite element model of the fiber. The first fiber is Part_4 and the second fiber is Part_5.

Claims

1. A method for establishing a microscopic finite element model of a hybrid fiber concrete, characterized in that: The steps include: S1: Taking the cylinder as an example, the size of the cylindrical hybrid fiber concrete matrix is ​​determined. The cross-sectional radius of the cylinder is R 基体 , the height of the cylindrical concrete is h, then the volume of the concrete matrix is: V 基体 =π·R 基体 2 ·h First, calculate the volumes of the three aggregates: V1, V2, and V3: Then calculate the volumes of the two single fibers: V4 and V5: S2: Complete the setting of relevant parameters required for aggregates and fibers. First, randomly generate aggregates in the specified area. Except for the first generated aggregate, each subsequent generated aggregate needs to be judged for intrusion with the generated aggregates. If none of them invade, the aggregate is generated and the volume rate is calculated. Otherwise, the aggregate is deleted and regenerated to perform intrusion judgment until the cumulative volume rate of the generated aggregates reaches the set value. The formula for calculating the aggregate volume ratio is as follows: S3: Determine the coordinates of the first endpoint A of each fiber. The process is as follows: First, use the rand function rand(n1+n2, 1), which represents the generation of n1+n2 random numbers between 0 and 1, and then determine the three coordinates of points A1 and A2 in the Cartesian coordinate system: Randomly generate the x coordinate of the first endpoint A1 of each fiber of the first type: X A1 =L1+rand(n1+n2,1)·(a-2L1) Randomly generate the y coordinate of the first endpoint A1 of each fiber of the first type: AND A1 =L1+rand(n1+n2,1)·(b-2L1) Randomly generate the z coordinate of the first endpoint A1 of each fiber of the first type: Z A1 =L1+rand(n1+n2,1)·(c-2L1) Randomly generate the x coordinate of the first endpoint A2 of each fiber of the second type: X A2 =L2+rand(n1+n2,1)·(a-2L2) Randomly generate the y coordinate of the first endpoint A2 of each fiber of the second type: <h2 style=";text-align:left;direction:ltr">Y<h2 style=";text-align:left;direction:ltr"> A2 <h2 style=";text-align:left;direction:ltr"> = L2+rand(n1+n2,1)·(b-2L2) Randomly generate the z coordinate of the first endpoint A2 of each fiber of the second type: <h2 style=";text-align:left;direction:ltr">Z<h2 style=";text-align:left;direction:ltr"> A2 <h2 style=";text-align:left;direction:ltr"> = L2+rand(n1+n2,1)·(c-2L2) Based on the Monte-Carlo method, the second end point B and the midpoint C of each fiber are randomly generated, and finally the hybrid mathematical modeling is completed. The process is as follows: Extract the first fiber in the Monte Carlo cycle and randomly select its angle θ with the x-axis x : i x =rand(1)·2π Its angle with the y-axis is θ y : i y =rand(1)·2π Its angle with the z-axis is θ z : i z =rand(1)·2π Thus, the coordinates of the second end point B1 of the fiber can be obtained. The values ​​of the x, y, and z coordinates of point B1 are: X B1 =X A1 +L1·cos(θ x ) AND B1 =And A1 +L1 cos(θ y ) WITH B1 =Z A1 +L1 cos(θ z ) The coordinates of the midpoint C of the fiber can also be obtained. The x, y, and z coordinates of point C are: X C1 =X A1 +L1·cos(θ x ) / 2 AND C1 =And A1 +L1 cos(θ y ) / 2 WITH C1 =Z A1 +L1 cos(θ z ) / 2 S4: Generate the first type of fiber in the specified area. The first fiber only needs to be judged for intrusion with the existing aggregate. Each subsequent fiber needs to be judged for intrusion with the generated aggregate and the generated fiber. If neither of them intrudes, the fiber is generated and the volume rate is calculated. Otherwise, the fiber is deleted and the fiber is regenerated for intrusion judgment until the cumulative volume rate of the generated fibers reaches the set value. The generation method of the second fiber is the same as that of the first fiber. The fiber volume fraction calculation formula is as follows: S5: After the coordinates of the center of the aggregate, radius and line fiber coordinates are output, the mesoscopic component units are identified using Fortran programming, and the fiber concrete mesoscopic model is directly projected into the homogeneous finite element model of the container; the establishment of the hybrid fiber concrete mesoscopic finite element model is completed; In step S1: Three types of aggregate volumes, aggregate volume calculation method: V1, V2, and V3 refer to the volume of the first, second, and third aggregates, respectively. D1, D2, and D3 are the diameter parameters of the three aggregates, respectively. S1, S2, and S3 are the number of the three aggregates, respectively. The volume of a single fiber of the two fibers is calculated as follows: V4=S 截面积A ×L1×s4 V5=S 截面积B ×L2×s5 V4 is the volume of the first fiber, V5 is the volume of the second fiber; L1 and L2 are the lengths of the two fibers, s4 and s5 are the numbers of the two fibers, respectively; In step S2: The relevant parameters of aggregates include three groups of continuously graded aggregate diameter ranges D1∈[dial, dia2], D2∈[dia2, dia3], and D3∈[dia3, dia4]. The cumulative volume of aggregates in each size range is V1, V2, and V3. An aggregate array file is established, that is, the number of aggregates generated is: the number of aggregates in the range of D1 is s1, the number of aggregates in the range of D2 is s2, the number of aggregates in the range of D3 is s3, and the diameter of the aggregate R 骨料 , the coordinates of the center of the aggregate (X 骨料 , Y 骨料 , Z 骨料 ); The relevant parameters of the fiber include the length range of the two fibers L1∈[len1, len2], L2∈[len3, len4], the number of the first fiber is s4, and the cross-sectional area is S 截面积A , the number of the second type of fibers is s5, and the cross-sectional area is s 截面积B .

2. The method for establishing a microscopic finite element model of a hybrid fiber concrete according to claim 1, characterized in that: In step S2: the method for determining whether intrusion occurs between aggregates is as follows: If the distance between the coordinates of the center of the first aggregate and the coordinates of the center of the second aggregate in the established three-dimensional concrete micro-model is greater than or equal to the sum of the maximum radii of the aggregates, it is determined that they do not intersect; otherwise, they are determined to intersect, that is, whether the aggregate particles intrude is determined according to the following formula: (X 骨料i , Y 骨料i , Z 骨料i ) is the coordinate of the center of the first aggregate sphere, (X 骨料n , Y 骨料n , Z 骨料n ) is the coordinate of the center of the second aggregate sphere.

3. The method for establishing a microscopic finite element model of a hybrid fiber concrete according to claim 1, characterized in that: In step S4, the method for determining whether the aggregate and fiber have intrusion is as follows: Aggregate and fiber intrusion determination only requires determining that the shortest distance between the fiber and the center of the aggregate sphere is greater than or equal to the aggregate radius, that is, determining the distance between the two end points and the midpoint and the center of the aggregate sphere. The determination process is as follows: Take the coordinates of the center of the aggregate sphere (X 骨料i , Y 骨料 i,Z 骨料i )Distance between the center of the sphere and the first end point of the fiber: The distance between the center of the sphere and the second end point of the fiber: Distance between sphere center and fiber midpoint: (X A1 , Y A1 , Z A1 ) is the coordinate of the first endpoint, (x B1 , Y B1 , Z B1 ) is the coordinate of the first endpoint, (X C1 , Y C1 , Z C1 ) are the coordinates of the fiber midpoint.

4. The method for establishing a microscopic finite element model of hybrid fiber concrete according to claim 1 is characterized in that: In step S4, the method for determining whether the fiber-to-fiber intrusion phenomenon occurs is as follows: it is only necessary to determine that the line-fiber vector product is not 0, and the determination process is as follows: Take the first fiber coordinates and the two end points A1(X A1 ,Y A1 ,Z A1 ), B1(X B1 ,Y B1 ,Z B1 ) Take the coordinates of the second fiber and the two end points A2(X A2 ,Y A2 ,Z A2 ), B2(X B2 ,Y B2 ,Z B2 ) 。 5. The method for establishing a microscopic finite element model of hybrid fiber concrete according to claim 1 is characterized in that: In step S4: the homogenous finite element model of the container can be generated by ANSYS / APDL or HyperMesh finite element software, and the homogenous finite element model of the container is exported in the form of a k-file.

6. The method for establishing a microscopic finite element model of hybrid fiber concrete according to claim 1, characterized in that: Fortran programming is used to identify the micro-component units. The identification method is as follows: a. Use Fortran language in Visual Studio software to identify and assign values ​​to the aggregate coordinate file format and the k file of the homogeneous finite element model. The contents of identification and assignment are: ① the number of aggregates of different diameters s1, s2, s3, the array format of the aggregate diameter and the coordinates of the aggregate sphere center; ② the total number of units E and the total number of nodes N of the k file of the homogeneous finite element model, and the array format of the k file units and nodes; b. Calculate the center coordinates (X E , Y E , Z E ), determine its distance to the first aggregate sphere center (X 骨料1 , Y 骨料1 , Z 骨料1 ) is smaller than the radius of the first aggregate, the unit is determined as the aggregate + interface group Part_1, otherwise it is the mortar group Part_2; then the distance to the center point of the second aggregate (X 骨料2 , Y 骨料2 , Z 骨料2 ), and so on, until all aggregates have been gone through; c. Repeat the operation in b to calculate the center coordinates (X E , Y E， Z E ), determine its distance to the first aggregate sphere center (X 骨料1 , Y 骨料1 , Z 骨料1 ), if the distance is less than the radius of the first aggregate minus the interface thickness T, the unit is determined to be the aggregate group Part_3, and only the interface remains in Part_1, which is the interface group; hence, the identification of different micro-component units is completed, and the finite element models of the interface Part_1, mortar Part_2, and aggregate Part_3 are generated; d. Read the starting point coordinates (X 纤维1-start , Y 纤维1-start , Z 纤维1-start ) and the end point coordinate X 纤维1-end , Y 纤维1-end , Z 纤维1-end ), link161 unit is used to establish the finite element model of the fiber. The first fiber is Part_4 and the second fiber is Part_5.

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