Method for establishing microscopic finite element model of single-layer reinforced ultra-high performance concrete structure

Abstract

The present invention discloses a method for establishing a microscopic finite element model of a single-layer reinforced ultra-high performance concrete structure, which belongs to the field of fiber microscopic concrete simulation technology. The present invention first generates steel bars that meet the layout requirements in a set area, and randomly places fibers in the area. According to the relevant parameters of the fibers and the steel bars, the fibers are adjusted until it is confirmed that there is no intrusion or intersection between the fibers and all the steel bars. The reinforced concrete component model finally established ensures that there is no intrusion. By setting up a large number of fiber modeling and accurately modeling a single-layer steel bar arranged in two directions, the intrusion defect between the fiber and the steel bar is solved, the simulation model is closer to reality, and the accuracy of the simulation results is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fiber meso-concrete simulation, and in particular relates to a method for establishing a meso-finite element model of a single-layer reinforced ultra-high performance concrete structure. Background Art

[0002] At the macroscale, reinforced ultra-high performance concrete (UHPC) structures are often simplified as homogeneous materials for mechanical analysis. However, in reality, reinforced ultra-high performance concrete (UHPC) structures are typically heterogeneous materials, consisting of a multiphase composite material composed of a matrix, reinforcement, and steel fibers. Currently, modeling methods for such structures often rely on macroscopic mechanical models, which often ignore the complex internal properties of the structure. Although this simplified approach is suitable for studying overall performance, it cannot fully reveal the complexity, deformation patterns, and failure mechanisms of the internal components of the composite structure. In addition, size effects often exist in macroscopic mechanical tests. As the size of the structure increases, the size effect becomes more significant, reducing the applicability of macroscopic constitutive models applicable to a certain size at different sizes. Therefore, by establishing an accurate microscopic model, the size effect in the macroscopic mechanical model can be effectively circumvented. Developing a microscopic model that can accurately reflect the internal components and their distribution of reinforced ultra-high performance concrete structures is crucial for a deep understanding and prediction of the performance of such structures. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for establishing a mesoscopic finite element model of reinforced ultra-high performance concrete structures based on Monte Carlo with flexible layout and high accuracy. By establishing an accurate mesoscopic model, the size effect in the macroscopic mechanical model is avoided, and the internal components and their distribution of the reinforced ultra-high performance concrete structure are accurately reflected, thereby achieving an in-depth understanding and prediction of the performance of the structure.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for establishing a microscopic finite element model of a single-layer reinforced ultra-high performance concrete structure is characterized by comprising the following steps:

[0006] S1. Determine the size and volume of the concrete cube: the length of the cube is LX, the width of the cube is LY, and the height of the cube is LZ. Then the volume of the concrete is: V = LX·LY·LZ;

[0007] S2. Complete the setting and calculation of steel bar related parameters: set the thickness of the concrete cover in the X-axis, Y-axis, and Z-axis directions, and the length, width, and height of the cube in the placement area, and calculate the length of the steel bars in the X-axis and Y-axis directions; calculate the spacing of the transverse and longitudinal steel bars based on the number of transverse and longitudinal steel bars arranged; arrange the first transverse and longitudinal steel bars in the placement area and determine the coordinates, complete the steel bar arrangement based on the spacing, and save the steel bar coordinates;

[0008] S3. Fiber delivery area and related parameter settings: Determine the minimum and maximum delivery coordinate points of the X, Y, and Z axes, and then determine the fiber delivery range. Determine the delivery quantity based on the selected fiber size parameters and perform random delivery.

[0009] S4. Adjusting the fiber placement boundary and determining the intrusion between the fibers and the steel bars: After all fibers are randomly placed, their starting and ending coordinates are determined, and the coordinates of fibers that exceed the placement boundary are adjusted. After the adjustment is completed, the intrusion between the fibers and the steel bars is determined, and the fibers that have intruded into the steel bars are deleted and regenerated until all fibers have no intrusion or intersection with any steel bars, and the fiber coordinates are saved.

[0010] S5: Finite element model establishment: After completing all required fiber placement and steel bar arrangement, arrange and number the coordinate information of the fibers and steel bars, convert their endpoint coordinates into finite element simulation nodes, renumber and arrange the node information so that it becomes unit information that can be recognized by the finite element software, and use the fopen function in the MATLAB software to save it in the form of a keyword K file that can be recognized by the finite element analysis software ANSYS / LS-DYNA; the matrix finite element model can be generated by finite element software such as ANSYS / LS-DYNA, and the generated homogeneous finite element model can be exported as a k file.

[0011] As a further description of the technical solution of the present invention:

[0012] After all the steel bars are arranged in S2, the starting coordinates of all the horizontal and vertical steel bars are saved in the matrix form in g_node1 according to the generation order, and the ending coordinates of all the horizontal and vertical steel bars are saved in the matrix form in g_node2 according to the generation order;

[0013] After the fiber placement is completed in S4, the starting coordinates of the fibers that meet the requirements are saved in end_node1 in matrix form, and the ending coordinates of the fibers are saved in end_node2 in matrix form;

[0014] The steps for arranging node information in S5 are as follows: create a column vector BH4 with a length equal to the number of steel bars O, define its value as 0, connect BH4 with g_node1 and g_node2 to form a longer node vector; extract the row number A of end_node1 (i.e., the number of nodes in end_node1) and the row number B of end_node2 (i.e., the number of nodes in end_node2), create a column vector BH from 1 to A+B+O (the sum of the number of steel bars and the number of fibers), which is used for subsequent node numbering; arrange the node information in end_node1 and end_node2 in order, and connect the arranged node matrix with BH to form a longer node vector; initialize a zero matrix NODE of size (3·A+3·O, 5) to store the coordinates and other information of the nodes, and arrange the processed node information in the required order to obtain the total node set;

[0015] The steps for arranging the cell information are: create a column vector BH1 from 1 to A+O, create a column vector BH2 ​​from A+O+1 to A+B+2·O, create a column vector BH3 from A+B+2·O+1 to A+B+3·O for element numbering, create a column vector PART with a length of A+B, define its row values ​​from 1 to A as 100, define its values ​​from A+1 to A+O as 101, and combine PART, BH1, BH2, and BH3 into an overall cell matrix.

[0016] As a further description of the technical solution of the present invention:

[0017] The length of the steel bar in S2 is:

[0018] G-lx=LX-2·px,

[0019] G-ly=LY-2·py,

[0020] Wherein, px is the concrete cover thickness in the X-axis direction, py is the concrete cover thickness in the Y-axis direction, G-lx is the steel bar length in the X-axis direction, and G-ly is the steel bar length in the Y-axis direction;

[0021] Determine the number of longitudinal reinforcement arrangements nx and the number of transverse reinforcement arrangements ny, and calculate the spacing between the reinforcements:

[0022] JX=G-lx / (nx-1),

[0023] JY=G-ly / (ny-1),

[0024] Among them, JX is the spacing between longitudinal reinforcements, and JY is the spacing between transverse reinforcements.

[0025] As a further description of the technical solution of the present invention:

[0026] In S2, the starting coordinates of the first transverse reinforcement are first specified in the placement area, and the end coordinates of the first reinforcement are calculated using the reinforcement-related parameters. The three coordinates of the reinforcement corresponding to the Cartesian coordinate system are saved, and the starting coordinates and end coordinates of the first transverse reinforcement are translated to obtain the starting coordinates and end coordinates of the second transverse reinforcement until the arrangement of the transverse reinforcement is completed.

[0027] The starting point coordinates of the transverse reinforcement (X1 g , Y1 g , Z1 g ) is calculated as follows:

[0028] X1 g =px,

[0029] Y1 g =py+JY·(i-1)i∈[1,ny],

[0030] Z1 g =pz,

[0031] Transverse reinforcement end point coordinates (X2 g , Y2 g , Z2 g ) is calculated as follows:

[0032] X2 g =px+G-lx,

[0033] Y2 g =py+JY·(i-1)i∈[1,ny],

[0034] Z2 g =pz,

[0035] After completing the layout of all transverse reinforcements, first calculate the starting coordinates of the first longitudinal reinforcement in the placement area, calculate the end coordinates of the first longitudinal reinforcement using the reinforcement-related parameters, save the three coordinates of the reinforcement in the Cartesian coordinate system, translate the starting coordinates and end coordinates of the first longitudinal reinforcement, and obtain the starting coordinates and end coordinates of the second longitudinal reinforcement until the layout of the longitudinal reinforcement is completed.

[0036] Coordinates of the starting point of the longitudinal reinforcement (X3 g , Y3 g , Z3 g ) is calculated as follows:

[0037] X3 g =px+JX·(i-1)i∈[1,nx]

[0038] Y3 g =py,

[0039] Z3 g =pz+G-dia,

[0040] End point coordinates of longitudinal reinforcement (X4 g , Y4 g , Z4 g ) is calculated as follows:

[0041] X4 g =px+JX·(i-1)i∈[1,nx],

[0042] Y4 g =py+G-ly,

[0043] Z4 g =pz+G-dia,

[0044] Where pz is the thickness of the concrete cover in the Z-axis direction, and G-dia is the diameter of the steel bar section.

[0045] As a further description of the technical solution of the present invention:

[0046] The formula for calculating the delivery range in S3 is as follows:

[0047] x-min=x0,

[0048] x-max=x0+Lx1,

[0049] y-min=y0,

[0050] y-max=y0+Ly1,

[0051] z-min=z0,

[0052] z-max=z0+Lz1,

[0053] Among them, x0 is the minimum delivery coordinate point of the delivery range on the X axis, y0 is the minimum delivery coordinate point of the delivery range on the Y axis, z0 is the minimum delivery coordinate point of the delivery range on the Z axis, Lx1 is the maximum delivery coordinate point of the delivery range on the X axis, Ly1 is the maximum delivery coordinate point of the delivery range on the Y axis, and Lz1 is the maximum delivery coordinate point of the delivery range on the Z axis.

[0054] As a further description of the technical solution of the present invention:

[0055] The calculation formula for the number of fibers m put in S3 is as follows:

[0056]

[0057] Where dia is the fiber cross-sectional diameter, ratio is the fiber volume content, and Ln is the fiber length.

[0058] As a further description of the technical solution of the present invention:

[0059] The method for determining the starting point and direction vector of the fiber in S3 is as follows:

[0060] Use the rand function rand(1), which generates a random number between 0 and 1. The formula for calculating the starting point coordinates is as follows:

[0061] The X coordinate of the starting point of each fiber is randomly generated as: x1 = LX rand (1),

[0062] The Y coordinate of the starting point of each fiber is randomly generated as: y1 = LY rand (1),

[0063] The Z coordinate of the starting point of each fiber is randomly generated as: z1 = LZ rand (1),

[0064] Use angle1 to represent the angle of the direction vector in the xy plane, and angle2 to represent the tilt angle of the direction vector in the zy plane. The calculation formula is as follows:

[0065] angle1=2·π·rand(1),

[0066] angle2=2·π·rand(1),

[0067] angle1 and angle2 represent random angles in the range of 0 to 2π;

[0068] The fiber end point coordinates are calculated using the starting point coordinates and random angles angle1 and angle2. The calculation formula is as follows:

[0069] The X coordinate of the end point of each fiber is randomly generated as: x2 = x1 + Ln·cos(angle2)·cos(angle1),

[0070] The Y coordinate of the end point of each fiber is randomly generated as: y2 = y1 + Ln·cos(angle2)·sin(angle1),

[0071] The Z coordinate of the end point of each fiber is randomly generated as: z2=z1+Ln·sin(angle2).

[0072] As a further description of the technical solution of the present invention:

[0073] After all fibers are placed, their starting and ending coordinates are determined. When the starting and ending coordinates exceed the minimum placement boundary of the placement area, their coordinates are automatically corrected to be offset 1 mm inward from the minimum placement boundary. The calculation formula is as follows:

[0074] x1=x-min+0.001,

[0075] y1=y-min+0.001,

[0076] z1=z-min+0.001,

[0077] x2=x-min+0.001,

[0078] y2=y-min+0.001,

[0079] z2=z-min+0.001,

[0080] When the starting point coordinates and the end point coordinates exceed the maximum delivery boundary of the delivery area, the coordinates are automatically corrected to be offset 1 mm inward from the maximum delivery boundary. The calculation formula is as follows:

[0081] x1=x-max-0.001,

[0082] y1=y-max-0.001,

[0083] z1=z-max-0.001,

[0084] x2=x-max-0.001,

[0085] y2=y-max-0.001,

[0086] z2=z-max-0.001.

[0087] As a further description of the technical solution of the present invention:

[0088] When the intrusion between the fiber and the steel bar is judged in S4, the starting coordinates POINT-P1 (x1, y1, z1) and the end coordinates POINT-P2 (x2, y2, z2) of the first fiber are extracted, and the starting coordinates POINT-A (X G 1,Y G 1,Z G 1) The corresponding end point coordinates POINT-B (X G 2,Y G 2,Z G 2) When the fiber and the steel bar intrude and intersect in the matrix space, the shortest distance from the coordinates of the two end points of the fiber to the direction vector of the steel bar is calculated respectively. The calculation formula is as follows:

[0089]

[0090]

[0091]

[0092]

[0093]

[0094] Calculate the two intersection points of the shortest distance vector and the reinforcement direction vector using the following formula:

[0095]

[0096]

[0097] After finding the midpoint coordinates C of the two intersection points, use the midpoint coordinates C to calculate the shortest distance Dist from the midpoint coordinates to the fiber. The calculation formula is as follows:

[0098]

[0099]

[0100]

[0101]

[0102]

[0103]

[0104]

[0105]

[0106] Finally, the minimum value among Dist, Dist1, and Dist2 is taken as the shortest distance between the fiber and the steel bar. By judging the relationship between the minimum value and the sum of the cross-sectional radius of the fiber and steel bar, it is decided whether to delete the fiber and regenerate it.

[0107] After completing the judgment of the intrusion relationship between the first fiber and the first steel bar in the matrix g_node1 and g_node2, the intrusion relationship between the first fiber and all the remaining steel bars in g_node1 and g_node2 is judged cyclically;

[0108] After completion, the intrusion relationship between the second fiber and all the steel bars in g_node1 and g_node2 is judged until the intrusion judgment of all fibers and all steel bars is completed;

[0109] The newly generated fiber needs to re-judge whether it intrudes into each steel bar in g_node1 and g_node2, until all fibers do not intrude or intersect with all steel bars.

[0110] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0111] Currently, most concrete micro-modeling technologies only include single fiber and steel components, and rarely include all components of ultra-high performance concrete steel composite structures. This method models a large number of fibers and accurately models single-layer steel bars arranged in two directions, solving the intrusion defects between fibers and steel bars. The simulation model is closer to reality, which improves the accuracy of the simulation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0112] Figure 1 This is a finite element model diagram of the fiber of the ultra-high performance concrete reinforced composite structure of the present invention;

[0113] Figure 2 This is a finite element model diagram of the steel bars of the ultra-high performance concrete reinforced composite structure of the present invention;

[0114] Figure 3 This is a finite element model diagram of the cross section of the ultra-high performance concrete reinforced composite structure of the present invention. DETAILED DESCRIPTION

[0115] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0116] Example 1: Establish a finite element model of a single-layer, bidirectional reinforced concrete composite structure. Figure 1-3 :

[0117] Step 1: Generate basic information for the ultra-high performance concrete reinforced composite structure using MATLAB software. Create two rows of horizontal and vertical line segments within the designated area. Since the geometry of rebar approximates line segments, these directional line segments can be considered rebar. Based on this, generate random fibers. Since the geometry of fibers approximates line segments, these random line segments can be considered fibers.

[0118] The specific process is as follows:

[0119] 1.1. Use MATLAB language to declare the relevant parameters required for fiber and steel bar

[0120] Determine the size and volume of a concrete cube: If the length of the cube is LX, the width of the cube is LY, and the height of the cube is LZ, then the volume of the concrete is:

[0121] V = LX·LY·LZ;

[0122] Related parameters include the concrete cover thickness px in the X-axis direction, the concrete cover thickness py in the Y-axis direction, the concrete cover thickness pz in the Z-axis direction, the steel bar cross-sectional diameter G-dia, the number of longitudinal steel bars arranged nx, and the number of transverse steel bars arranged ny; fiber-related parameters include the fiber cross-sectional diameter dia, the fiber volume content ratio, and the fiber length Ln.

[0123] 1.2. Complete the calculation of steel bar related parameters

[0124] Based on the thickness of the concrete cover in the X, Y, and Z directions and the length, width, and height of the cube in the deployment area, calculate the length of the steel bars in the X and Y directions. Based on the number of transverse and longitudinal bars arranged, calculate the spacing between the transverse and longitudinal bars. The transverse bar length G-lx and the longitudinal bar length G-ly, as well as the spacing between transverse bars JY and the spacing between longitudinal bars JX, are as follows:

[0125] G-lx=LX-2·px,

[0126] G-ly=LY-2·py,

[0127] Spacing between steel bars:

[0128] JX=G-lx / (nx-1),

[0129] JY = G-ly / (ny-1).

[0130] 1.3. Horizontal and vertical reinforcement arrangement

[0131] The reinforcement placement area is inside the concrete cube. First, specify the starting coordinates of the first transverse reinforcement in the placement area. Use the reinforcement-related parameters to calculate the end coordinates of the first reinforcement. Save the three coordinates of the reinforcement in the Cartesian coordinate system. Then translate the starting coordinates and end coordinates of the first transverse reinforcement to obtain the starting coordinates and end coordinates of the second transverse reinforcement until the arrangement of the transverse reinforcement is completed.

[0132] The starting point coordinates of the transverse reinforcement (X1 g , Y1 g , Z1 g ) is calculated as follows:

[0133] X1 g =px,

[0134] Y1 g =py+JY·(i-1)i∈[1,ny],

[0135] Z1 g =pz,

[0136] Transverse reinforcement end point coordinates (X2 g , Y2 g , Z2 g ) is calculated as follows:

[0137] X2 g =px+G-lx,

[0138] Y2 g =py+JY·(i-1)i∈[1,ny],

[0139] Z2 g =pz,

[0140] For easy identification, the numbers in the coordinates reflect the starting or ending point. The starting point of a transverse reinforcement is represented by the number 1 and the ending point by the number 2. The starting point of a longitudinal reinforcement is represented by the number 3 and the ending point by the number 4. The naming of coordinates is mainly used to distinguish the operation of computer programs, but other naming methods can also be used.

[0141] After completing the layout of all transverse reinforcements, first calculate the starting coordinates of the first longitudinal reinforcement in the placement area, calculate the end coordinates of the first longitudinal reinforcement using the reinforcement-related parameters, save the three coordinates of the reinforcement in the Cartesian coordinate system, translate the starting coordinates and end coordinates of the first longitudinal reinforcement, and obtain the starting coordinates and end coordinates of the second longitudinal reinforcement until the layout of the longitudinal reinforcement is completed.

[0142] Coordinates of the starting point of the longitudinal reinforcement (X3 g , Y3 g , Z3 g ) is calculated as follows:

[0143] X3 g =px+JX·(i-1)i∈[1,nx]

[0144] Y3 g =py,

[0145] Z3 g =pz+G-dia,

[0146] End point coordinates of longitudinal reinforcement (X4 g , Y4 g , Z4 g ) is calculated as follows:

[0147] X4 g =px+JX·(i-1)i∈[1,nx],

[0148] Y4 g =py+G-ly,

[0149] Z4g =pz+G-dia,

[0150] After completing the layout of all steel bars, save the starting coordinates of all horizontal and vertical steel bars in matrix form in g_node1 according to the generation order, and save the ending coordinates of all horizontal and vertical steel bars in matrix form in g_node2 according to the generation order.

[0151] 1.4 Fiber calculation and placement

[0152] A certain amount of random fibers are placed in a designated area, and the fiber placement area and related parameters are set. The minimum placement coordinate point on the X axis of the placement range is x0, the minimum placement coordinate point on the Y axis of the placement range is y0, the minimum placement coordinate point on the Z axis of the placement range is z0, the maximum placement coordinate point on the X axis of the placement range is Lx1, the maximum placement coordinate point on the Y axis of the placement range is Ly1, the maximum placement coordinate point on the Z axis of the placement range is Lz1, the fiber cross-sectional diameter is dia, the fiber volume content is ratio, and Ln is the fiber length. The placement range calculation formula is as follows:

[0153] x-min=x0,

[0154] x-max=x0+Lx1,

[0155] y-min=y0,

[0156] y-max=y0+Ly1,

[0157] z-min=z0,

[0158] z-max=z0+Lz1,

[0159] The calculation formula for the fiber input quantity m is as follows:

[0160]

[0161] The fibers are randomly placed. The method of randomly placing the fibers is as follows:

[0162] To determine the starting point and direction vector of the fiber, use the rand function rand(1), which generates a random number between 0 and 1. The formula for calculating the starting point coordinates is as follows:

[0163] Randomly generate the X coordinate of the starting point of each fiber: x1 = LX rand (1)

[0164] Randomly generate the Y coordinate of the starting point of each fiber: y1 = LY rand (1),

[0165] Randomly generate the Z coordinate of the starting point of each fiber: z1 = LZ rand (1),

[0166] Use angle1 to represent the angle of the direction vector in the xy plane, and angle2 to represent the tilt angle of the direction vector in the zy plane. The calculation formula is as follows:

[0167] angle1=2·π·rand(1),

[0168] angle2=2·π·rand(1),

[0169] angle1 and angle2 represent random angles in the range of 0 to 2π;

[0170] The fiber end point coordinates are calculated using the starting point coordinates and random angles angle1 and angle2. The calculation formula is as follows:

[0171] The X coordinate of the end point of each fiber is randomly generated as: x2 = x1 + Ln·cos(angle2)·cos(angle1),

[0172] The Y coordinate of the end point of each fiber is randomly generated as: y2 = y1 + Ln·cos(angle2)·sin(angle1),

[0173] The Z coordinate of the end point of each fiber is randomly generated as: z2=z1+Ln·sin(angle2),

[0174] 1.5. Fiber coordinate adjustment

[0175] After all fibers are placed, their starting and ending coordinates are determined. When the starting and ending coordinates exceed the minimum placement boundary of the placement area, their coordinates are automatically corrected to be offset 1 mm inward from the minimum placement boundary. The calculation formula is as follows:

[0176] x1=x-min+0.001,

[0177] y1=y-min+0.001,

[0178] z1=z-min+0.001,

[0179] x2=x-min+0.001,

[0180] y2=y-min+0.001,

[0181] z2=z-min+0.001,

[0182] When the starting point coordinates and the end point coordinates exceed the maximum delivery boundary of the delivery area, the coordinates are automatically corrected to be offset 1 mm inward from the maximum delivery boundary. The calculation formula is as follows:

[0183] x1=x-max-0.001,

[0184] y1=y-max-0.001,

[0185] z1=z-max-0.001,

[0186] x2=x-max-0.001,

[0187] y2=y-max-0.001,

[0188] z2=z-max-0.001.

[0189] 1.6. Determination of fiber and steel bar intrusion

[0190] After all fibers are placed and processed, the intrusion between the fibers and the steel bars is determined, and the starting coordinates POINT-P1 (x1, y1, z1) and the end coordinates POINT-P2 (x2, y2, z2) of the first fiber are extracted, and the starting coordinates POINT-A (X G 1,Y G 1,Z G 1) The corresponding end point coordinates POINT-B (X G 2,Y G 2,Z G 2) When the fiber and the steel bar intrude and intersect in the matrix space, the shortest distance from the coordinates of the two end points of the fiber to the direction vector of the steel bar is calculated respectively. The calculation formula is as follows:

[0191]

[0192]

[0193]

[0194]

[0195]

[0196] Calculate the two intersection points of the shortest distance vector and the reinforcement direction vector using the following formula:

[0197]

[0198]

[0199] After finding the midpoint coordinates C of the two intersection points, use the midpoint coordinates C to calculate the shortest distance Dist from the midpoint coordinates to the fiber. The calculation formula is as follows:

[0200]

[0201]

[0202]

[0203]

[0204]

[0205]

[0206]

[0207]

[0208] Finally, the minimum value among Dist, Dist1, and Dist2 is taken as the shortest distance from the fiber to the rebar. By comparing this value with the sum of the cross-sectional radius of the fiber and rebar, a decision is made as to whether to delete the fiber and regenerate it. After determining the intrusion relationship between the first fiber and the first rebar in the matrix g_node1 and g_node2, the intrusion relationship between the first fiber and all remaining rebars in g_node1 and g_node2 is determined in a loop. After this, the intrusion relationship between the second fiber and all rebars in g_node1 and g_node2 is determined, until all fibers and all rebars have been determined. Newly generated fibers must then be re-evaluated for intrusion with each rebar in g_node1 and g_node2, until all fibers and all rebars are clear of intrusion or intersection.

[0209] After the fiber placement is completed, the starting coordinates of the fiber that meets the requirements are saved in end_node1 in matrix form, and the ending coordinates of the fiber are saved in end_node2 in matrix form.

[0210] Step 2: After completing all the required fiber placement and steel bar layout, arrange and number the coordinate information of the fibers and steel bars, convert their endpoint coordinates into finite element simulation nodes, renumber the node information so that it becomes unit information that can be recognized by the finite element software, and use the fopen function in the MATLAB software to save it in the form of a keyword K file that can be recognized by the finite element analysis software ANSYS / LS-DYNA.

[0211] 2.1. Converting steel bar and fiber coordinate information into finite element simulation model information

[0212] Node information arrangement: Create a column vector BH4 with a length equal to the number of rebars, O, and define its value as 0. Concatenate BH4 with g_node1 and g_node2 to form a longer node vector. Extract the row number A of end_node1 (i.e., the number of nodes in end_node1) and the row number B of end_node2 (i.e., the number of nodes in end_node2), and create a column vector BH ranging from 1 to A+B+O (the sum of the number of rebars and fibers) for subsequent node numbering. Arrange the node information in end_node1 and end_node2 in sequence and concatenate the arranged node matrix with BH to form a longer node vector. Initialize a zero matrix NODE of size (3·A+3·O, 5) to store node coordinates and other information. Arrange the processed node information in the desired order to obtain the total node set.

[0213] Cell information arrangement: Create a column vector BH1 from 1 to A+O, a column vector BH2 ​​from A+O+1 to A+B+2·O, and a column vector BH3 from A+B+2·O+1 to A+B+3·O for element numbering. Create a column vector PART of length A+B, define its row values ​​from 1 to A as 100, and define its row values ​​from A+1 to A+O as 101. Combine PART, BH1, BH2, and BH3 into the overall cell matrix.

[0214] 2.2. Open the file model.k in write mode, write different model data into the file, add the file header information and format description, and obtain the finite element model file.

[0215] 2.3. Use the finite element analysis software ANSYS / LS-DYNA to directly open the obtained K file, where PART-100 is fiber and PART-101 is steel bar.

[0216] 2.4. Use the finite element analysis software ANSYS / LS-DYNA to open the K file and establish a homogeneous matrix model by determining the dimensions of the cube concrete, cube length LX, cube width LY, and cube height LZ. Then use the software to save it in the same K file with the fiber and steel bar models.

[0217] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. The method for establishing a microscopic finite element model of a single-layer reinforced ultra-high performance concrete structure is characterized by The steps include: S1. Determine the size and volume of concrete cube; S2. Complete the setting and calculation of steel bar related parameters: Set and calculate the steel bar parameters according to the parameters of the cubic concrete, arrange the first horizontal and vertical steel bars in the placement area and determine the coordinates, complete the steel bar arrangement according to the spacing, and save the steel bar coordinates; S3. Fiber delivery area and related parameter settings: Determine the fiber delivery range, determine the delivery quantity based on the selected fiber size parameters, and perform random delivery; S4. Adjusting the fiber placement boundary and determining the intrusion between the fiber and the steel bar: Adjust the coordinates of the fibers that exceed the placement boundary. After the adjustment is completed, determine the intrusion between the fiber and the steel bar. Based on the spatial vector geometric relationship, calculate the shortest distance between the fiber and the steel bar and determine its relationship with the sum of the radii of the two to determine whether intrusion occurs. Fibers that intrude into the steel bar are deleted and regenerated until all fibers do not intrude or intersect with all steel bars, and save the fiber coordinates. S5: Finite element model establishment: After completing all required fiber placement and reinforcement layout, arrange and number the coordinate information of the fibers and reinforcements, convert their endpoint coordinates into finite element simulation nodes, renumber and arrange the node information so that it becomes unit information that can be recognized by the finite element software, and use the fopen function in MATLAB software to save it in the form of a keyword K file that can be recognized by the finite element analysis software ANSYS / LS-DYNA; The matrix finite element model is generated by ANSYS / LS-DYNA finite element software, and the generated homogeneous finite element model is exported in the form of a k-file.

2. The method for establishing a microscopic finite element model of a single-layer reinforced ultra-high performance concrete structure according to claim 1, wherein: After all the steel bars are arranged in S2, the starting coordinates of all the horizontal and vertical steel bars are saved in the matrix form in g_node1 according to the generation order, and the ending coordinates of all the horizontal and vertical steel bars are saved in the matrix form in g_node2 according to the generation order; After the fiber placement is completed in S4, the starting point coordinates of the fiber that meets the requirements are saved in end_node1 in matrix form, and the ending point coordinates of the fiber are saved in end_node2 in matrix form.

3. The method for establishing a microscopic finite element model of a single-layer reinforced ultra-high performance concrete structure according to claim 2, wherein: The steps for arranging node information in S5 are as follows: create a column vector BH4 with a length equal to the number of steel bars O, define its value as 0, and connect BH4 with g_node1 and g_node2 to form a longer node vector; extract the row number A of end_node1 and the row number B of end_node2, and create a column vector BH from 1 to A+B+O for subsequent node numbering; arrange the node information in end_node1 and end_node2 in sequence, and connect the arranged node matrix with BH to form a longer node vector; initialize a zero matrix NODE of size (3 • A + 3 • O, 5) to store information including node coordinates, and arrange the processed node information in the required order to obtain the total node set; The steps for arranging cell information are: create a column vector BH1 from 1 to A+O, create a column vector BH2 ​​from A+O+1 to A+B+2 • O, create a column vector BH3 from A+B+2 • O+1 to A+B+3 • O for element numbering, create a column vector PART with a length of A+B, define its row values ​​from 1 to A as 100, define its values ​​from A+1 to A+O as 101, and combine PART, BH1, BH2, and BH3 into an overall cell matrix.

4. The method for establishing a microscopic finite element model of a single-layer reinforced ultra-high performance concrete structure according to claim 3, wherein: In S1, the length of the concrete cube is LX, the width of the cube is LY, and the height of the cube is LZ, so the volume of the concrete is: V = LX • LY • LZ; In S2, the length of the steel bars in the X-axis and Y-axis directions is calculated based on the thickness of the concrete cover in the X-axis, Y-axis and Z-axis directions and the length, width and height of the cube in the delivery area; the spacing between the transverse and longitudinal steel bars is calculated based on the number of transverse and longitudinal steel bars arranged; The length of steel bars is: G-lx = LX - 2 • px, G-ly = LY - 2 • py, Wherein, px is the concrete cover thickness in the X-axis direction, py is the concrete cover thickness in the Y-axis direction, G-lx is the steel bar length in the X-axis direction, and G-ly is the steel bar length in the Y-axis direction; The number of longitudinal reinforcement is nx, the number of transverse reinforcement is ny, and the spacing between reinforcements is: JX = G-lx / (nx - 1), JY = G-ly / (ny - 1), Among them, JX is the spacing of longitudinal reinforcement and JY is the spacing of transverse reinforcement.

5. The method for establishing a microscopic finite element model of a single-layer reinforced ultra-high performance concrete structure according to claim 4, characterized in that: In S2, the starting coordinates of the first transverse reinforcement are first specified in the placement area, and the end coordinates of the first reinforcement are calculated using the reinforcement-related parameters. The three coordinates of the reinforcement corresponding to the Cartesian coordinate system are saved, and the starting coordinates and end coordinates of the first transverse reinforcement are translated to obtain the starting coordinates and end coordinates of the second transverse reinforcement until the arrangement of the transverse reinforcement is completed. Coordinates of starting point of transverse reinforcement ( , , ) is calculated as follows: = px, = py+JY • (i-1) i∈[1,ny], = pz, Transverse reinforcement end point coordinates ( , , ) is calculated as follows: = px + G-lx, = py + JY • (i-1) i∈[1 ,ny], = pz, After completing the layout of all transverse reinforcements, first calculate the starting coordinates of the first longitudinal reinforcement in the placement area, calculate the end coordinates of the first longitudinal reinforcement using the reinforcement-related parameters, save the three coordinates of the reinforcement in the Cartesian coordinate system, translate the starting coordinates and end coordinates of the first longitudinal reinforcement, and obtain the starting coordinates and end coordinates of the second longitudinal reinforcement until the layout of the longitudinal reinforcement is completed. Coordinates of the starting point of the longitudinal reinforcement ( ) is calculated as follows: = px+ JX •(i-1) i∈[1 ,nx] = py, = pz + G-dia, End point coordinates of longitudinal reinforcement ( ) is calculated as follows: = px + JX •(i-1) i∈[1 ,nx], = py +G-ly, = pz + G-dia, Where pz is the thickness of the concrete cover in the Z-axis direction, and G-dia is the diameter of the steel bar section.

6. The method for establishing a microscopic finite element model of a single-layer reinforced ultra-high performance concrete structure according to claim 5, characterized in that: In S3, the minimum and maximum delivery coordinate points of the X, Y, and Z axes are first determined, and then the fiber delivery range is determined; After all fibers are randomly placed in S4, their starting point coordinates and end point coordinates are determined to determine whether they exceed the placement boundary; The formula for calculating the fiber delivery range is as follows: x-min=x0, x-max=x0 + Lx1, y-min=y0, y-max=y0 + Ly1, z-min=z0, z-max=z0 + Lz1, Among them, x0 is the minimum delivery coordinate point of the delivery range on the X axis, y0 is the minimum delivery coordinate point of the delivery range on the Y axis, z0 is the minimum delivery coordinate point of the delivery range on the Z axis, Lx1 is the maximum delivery coordinate point of the delivery range on the X axis, Ly1 is the maximum delivery coordinate point of the delivery range on the Y axis, and Lz1 is the maximum delivery coordinate point of the delivery range on the Z axis.

7. The method for establishing a microscopic finite element model of a single-layer reinforced ultra-high performance concrete structure according to claim 6, characterized in that: The calculation formula for the number of fibers m put in S3 is as follows: m = ， Where dia is the fiber cross-sectional diameter, ratio is the fiber volume content, and Ln is the fiber length.

8. The method for establishing a microscopic finite element model of a single-layer reinforced ultra-high performance concrete structure according to claim 7, wherein: The method for determining the starting point and direction vector of the fiber in S3 is as follows: Use the rand function rand(1), which generates a random number between 0 and 1. The formula for calculating the starting point coordinates is as follows: The X coordinate of the starting point of each fiber is randomly generated as: x1 = LX • rand(1), The Y coordinate of the starting point of each fiber is randomly generated as: y1 = LY • rand(1), The Z coordinate of the starting point of each fiber is randomly generated as: z1 = LZ • rand(1), Use angle1 to represent the angle of the direction vector in the xy plane, and angle2 to represent the tilt angle of the direction vector in the zy plane. The calculation formula is as follows: angle1 = 2 • • rand(1), angle2 = 2 • • rand(1), angle1 and angle2 represent random angles in the range of 0 to 2π; The fiber end point coordinates are calculated using the starting point coordinates and random angles angle1 and angle2. The calculation formula is as follows: The X coordinate of the end point of each fiber is randomly generated as follows: x2 = x1 +Ln • cos(angle2) • cos(angle1), The Y coordinate of the end point of each fiber is randomly generated as follows: y2 = y1 +Ln • cos(angle2) • sin(angle1), The Z coordinate of the end point of each fiber is randomly generated as: z2 = z1 + Ln • sin(angle2).

9. The method for establishing a microscopic finite element model of a single-layer reinforced ultra-high performance concrete structure according to claim 8, characterized in that: After all fibers are placed, their starting and ending coordinates are determined. When the starting and ending coordinates exceed the minimum placement boundary of the placement area, their coordinates are automatically corrected to be offset 1 mm inward from the minimum placement boundary. The calculation formula is as follows: x1 = x-min + 0.001, y1 = y-min + 0.001, z1 = z-min + 0.001, x2 = x-min + 0.001, y2 = y-min + 0.001, z2 = z-min + 0.001, When the starting point coordinates and the end point coordinates exceed the maximum delivery boundary of the delivery area, the coordinates are automatically corrected to be offset 1 mm inward from the maximum delivery boundary. The calculation formula is as follows: x1 = x-max - 0.001, y1 = y-max - 0.001, z1 = z-max - 0.001, x2 = x-max - 0.001, y2 = y-max - 0.001, z2 = z-max - 0.

001.

10. The method for establishing a microscopic finite element model of a single-layer reinforced ultra-high performance concrete structure according to claim 9, wherein: When determining the penetration between the fiber and the steel bar in S4, the starting coordinates of the first fiber are extracted. (x1, y1, z1) and the end point coordinates POINT- (x2, y2, z2), extract the starting coordinates of the first steel bar in the matrix g_node1 POINT-A ( , , ) and the corresponding end point coordinates POINT-B( , , ), when the fiber and the steel bar intrude and intersect in the matrix space, the shortest distance from the coordinates of the two end points of the fiber to the direction vector of the steel bar is calculated respectively. The calculation formula is as follows: ， ， ， ， ， Calculate the two intersection points of the shortest distance vector and the reinforcement direction vector using the following formula: ， ， After finding the midpoint coordinates C of the two intersection points, use the midpoint coordinates C to calculate the shortest distance Dist from the midpoint coordinates to the fiber. The calculation formula is as follows: ， ， ， ， ， Dist= , Dist1= , Dist2= , Finally, the minimum value among Dist, Dist1, and Dist2 is taken as the shortest distance between the fiber and the steel bar. By judging the relationship between the minimum value and the sum of the cross-sectional radius of the fiber and steel bar, it is decided whether to delete the fiber and regenerate it. After completing the judgment of the intrusion relationship between the first fiber and the first steel bar in the matrix g_node1 and g_node2, the intrusion relationship between the first fiber and all the remaining steel bars in g_node1 and g_node2 is judged cyclically; After completion, the intrusion relationship between the second fiber and all the steel bars in g_node1 and g_node2 is judged until the intrusion judgment of all fibers and all steel bars is completed; The newly generated fiber needs to re-judge whether it intrudes into each steel bar in g_node1 and g_node2, until all fibers do not intrude or intersect with all steel bars.

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