A finite element simulation method for compartment joints in foundation slabs using the skip-compartment method

Abstract

The present invention discloses a finite element simulation method for compartment joints in foundation slabs using a skip-bin method. The method comprises the following steps: a commonly used compartment joint structure in a foundation slab includes a compartment block A, a compartment block B, a contact surface, a waterstop steel plate, and bottom slab reinforcement; solid elements are used to simulate the compartment blocks, viscous elements are used to simulate the contact surface, bushing elements are used to simulate the waterstop steel plate, and truss elements are used to simulate the reinforcement; the bond-slip characteristics of the compartment joints are simulated using viscous elements, and the parameters of the traction-separation constitutive model are determined by inverse analysis using a PSO-SVM algorithm based on uniaxial tension test results. The finite element simulation method for compartment joints in foundation slabs using the skip-bin method can simultaneously consider detailed components such as the contact surface, the waterstop steel plate, and the bottom slab reinforcement. Furthermore, the mechanical properties of the compartment joints can be refined by simulating the bond-slip characteristics of the contact surface and the waterstop steel plate, and the mechanical parameters of the viscous elements can be quickly and accurately determined. This improves the accuracy of the finite element simulation of foundation slabs using the skip-bin method.

Description

Technical Field

[0001] The present invention relates to the technical field of numerical simulation of building structures, and in particular to a finite element simulation method for a foundation bottom plate compartment seam using a skipping compartment method. Background Art

[0002] The skip-bin method controls cracks according to the principle of "placement first, then reinforcement," and adheres to the principles of "block planning, spaced-block construction, layered pouring, and overall shaping." By dividing a large volume of concrete into several smaller bins, these are then connected together after short-term thermal and shrinkage stresses are released. This prevents cracking during the pouring of the large foundation slab due to thermal stress or hardening shrinkage. Accordingly, due to varying pouring times, partition joints are required between the different bins.

[0003] Large-area foundation slabs have numerous compartments and numerous compartment joints, which significantly impact the overall load of the slab. Therefore, the impact of compartment joints needs to be considered in early load analysis. However, current load simulations of structural slabs are relatively crude, lacking refined finite element simulation methods that consider the bonding properties of compartment joints. Furthermore, the relevant mechanical parameters of compartment joints are difficult to determine, resulting in inaccurate overall load analysis of the foundation slab. Summary of the Invention

[0004] The purpose of the present invention is to provide a finite element simulation method for the compartment joints of the foundation bottom plate using the skipping method to address the above-mentioned shortcomings, thereby solving the problem that the simulation of the compartment joints in the stress simulation of the structural bottom plate at the current stage is relatively rough, there is a lack of a finite element refined simulation method that considers the bonding characteristics of the compartment joints, and at the same time, it is difficult to determine the relevant mechanical parameters of the compartment joints, resulting in inaccurate overall stress analysis of the foundation bottom plate.

[0005] The present invention is achieved through the following solutions:

[0006] A finite element simulation method for compartment joints in foundation slabs using a skip-bin method comprises the following steps: a commonly used compartment joint structure in a foundation slab includes a compartment block A, a compartment block B, a contact surface, a waterstop steel plate, and bottom slab reinforcement; solid elements are used to simulate the compartment blocks, viscous elements are used to simulate the contact surface, bushing elements are used to simulate the waterstop steel plate, and truss elements are used to simulate the reinforcement; the bond-slip characteristics of the compartment joints are simulated using viscous elements, and the parameters of the traction-separation constitutive model are determined by inversion using a PSO-SVM algorithm based on the results of a uniaxial tension test.

[0007] In the above steps, the viscous element adopts the traction separation criterion to simulate its damage evolution: at the same time, the quadratic stress criterion is used as the damage initiation criterion: after the initial damage occurs, the interface stiffness degradation rate is described by the damage evolution criterion.

[0008] In the above steps, the uniaxial tensile test is specifically as follows: test blocks A and B are used to simulate bin blocks A and B respectively. The casting time sequence and interface treatment method are the same as the actual project. The two ends of bin blocks A and B are bonded and fixed to the upper bracket and the lower bracket respectively. A universal testing machine is used to support the two ends of the upper and lower brackets. The force and displacement data are read synchronously during the loading process.

[0009] The traction separation criterion is used to simulate the damage evolution of the viscous element. Specifically:

[0010]

[0011] Where, t n , t s , t t are the stresses in the normal and two tangential directions of the contact surface; K nn , K ss , K tt are the contact stiffness in three directions; δ n , δ s , δ t They are the contact displacements in three directions.

[0012] The quadratic stress criterion is used as the damage initiation criterion as follows:

[0013]

[0014] Where, are the peak stresses in the normal and two tangential directions, respectively.

[0015] Under the linear damage criterion, the damage variable D follows the following evolution law:

[0016]

[0017] Where, is the effective contact displacement at complete destruction; is the maximum effective contact displacement of the contact during the loading process; is the effective contact displacement when initial damage occurs.

[0018] In the above steps, K nn , K ss , K tt 、 The interface parameters are determined by inversion using the PSO-SVM algorithm;

[0019] The specific steps include:

[0020] S1: Start;

[0021] S2: Determine the value range of interface parameters;

[0022] S3: Use the LHS sampling algorithm to extract and set the parameter combinations used in the uniaxial tension numerical model. A total of n groups of parameter combinations are extracted and set:

[0023] S4: Based on the uniaxial tension test of the compartment joint, a uniaxial tension finite element model of the compartment joint is established: test blocks A and B are simulated using solid elements; the test contact surface is simulated using contact surface viscosity elements, and its element parameters are set according to the parameter combination extracted in S3; the upper bracket and the lower bracket are simulated using solid elements respectively. After substituting each test parameter combination, axial tension loads are applied at both ends and simulation is carried out to obtain a sample database;

[0024] S5: Substitute the sample database into the SVM model for training; select the kernel function of the SVM model, set the initial penalty parameters and kernel function parameters of the SVM model, and use them to initialize the PSO algorithm particle swarm;

[0025] S6: Run the PSO algorithm to calculate the individual optimum and the global optimum, calculate the particle fitness, iteratively update the particle fitness until it meets the termination condition, and then map the optimal particle to the penalty parameter and kernel function parameter of the SVM model;

[0026] S7: Input the uniaxial tension test data into the interface parameter inversion SVM model to obtain the optimal interface parameter values;

[0027] S8: Substitute the optimal interface parameters into the uniaxial tension numerical model of the compartment joint and compare with the uniaxial tension test data to verify the effect;

[0028] S9: End.

[0029] Specifically in S3:

[0030] a. Divide each parameter m into n equal probability intervals:

[0031]

[0032] b. For the i-th interval, the cumulative probability of sampling can be written as:

[0033]

[0034] c. Use the inverse probability distribution function F-1 to convert the probability into a sample value x:

[0035] m i =F -1 (p i )

[0036] The n values ​​obtained for each variable m are paired with the n values ​​of the other variables randomly or in some specific order.

[0037] In the above steps, the steel truss element is embedded, the waterproof steel plate is simulated by the bushing element, and the displacement-force curve of the bushing element is:

[0038] p=2dlsτ(x)

[0039] Where l is the anchorage length; d is the spacing of the bushing units; l is the length of the waterproof steel plate 2-2 embedded in the bin block A or bin block B; s is the circumference of the steel plate section within the spacing distance d; τ(x) is the bond stress curve between the steel plate and the concrete.

[0040] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0041] 1. The finite element simulation method for compartmentalized joints in foundation slabs using the skip-bin method adopted in this proposal can simultaneously account for detailed components such as the contact surface, waterstop steel plate, and bottom slab reinforcement. It can also refine the mechanical properties of the compartmentalized joints by simulating the bond-slip characteristics of the contact surface and waterstop steel plate. Furthermore, it can quickly and accurately determine the mechanical parameters of the viscous elements, thereby improving the accuracy of the finite element simulation of foundation slabs using the skip-bin method. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the compartment seam structure;

[0043] Figure 2 This is a structural diagram of another embodiment of the present application;

[0044] Figure 3 Schematic diagram of uniaxial tension test of compartment joint;

[0045] Figure 4 This is the flow chart of the inversion algorithm for mechanical parameters of the viscous unit of the compartment fracture;

[0046] Figure 5 It is the uniaxial tension finite element model of compartment joint;

[0047] Markings in the figure: 1-1, silo A; 1-2, silo B; 2-1, contact surface; 2-2, water-stop steel plate; 3, bottom plate reinforcement; 4, silo entity unit; 5, viscosity unit; 6, bushing unit; 7, truss unit; 8-1, test block A; 8-2, test block B; 9, test contact surface; 10-1, upper bracket; 10-2, lower bracket; 11-1, test block A entity unit; 11-2, test block B entity unit; 12, test contact surface viscosity unit; 13-1, upper bracket entity unit; 13-2, lower bracket entity unit. DETAILED DESCRIPTION

[0048] All features disclosed in this specification, or all steps in the disclosed methods or processes, except mutually exclusive features and / or steps, can be combined in any manner.

[0049] Any feature disclosed in this specification (including any appended claims and abstract), unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0050] In the description of the present invention, it should be understood that the terms "up", "down", "left", "right", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0051] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be understood to indicate or imply relative importance or to implicitly indicate the quantity of the technical features being referred to. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of such features.

[0052] Example 1

[0053] like Figures 1 to 5 As shown, the present invention provides a technical solution:

[0054] A finite element simulation method for a foundation bottom plate compartment seam of a skip-compartment method comprises the following steps:

[0055] The commonly used compartment joint structure of the foundation slab includes compartment block A1-1, compartment block B1-2, contact surface 2-1, waterstop steel plate 2-2 and bottom plate reinforcement 3. The solid element 4 is used to simulate the compartment block, the viscous element 5 is used to simulate the contact surface 2-1, the bushing element 6 is used to simulate the waterstop steel plate 2-2, and the truss element 7 is used to simulate the reinforcement. The viscous element 5 is used to simulate the bond-slip characteristics of the compartment joint. Based on the results of uniaxial tension tests, the PSO-SVM (particle swarm-support vector machine) algorithm is used to inversely determine the parameters of the traction-separation constitutive model.

[0056] This method solves the problem of refined finite element simulation of compartment joints; the present invention can simultaneously consider detailed components such as the contact surface 2-1, water-stop steel plate 2-2, and bottom plate steel bar 3 of the compartment joint, and can finely simulate the mechanical properties of the compartment joint by simulating the bonding-slip characteristics of the contact surface 2-1 and the water-stop steel plate 2-2, and can also quickly and accurately determine the mechanical parameters of the viscous unit 5.

[0057] In the above steps, the traction separation criterion is used to simulate the damage evolution of the viscous element 5:

[0058]

[0059] Where, t n , t s , t t are the stresses in the 2-1 normal and 2 tangential directions of the contact surface; K nn , K ss , K tt are the contact stiffness in three directions; δ n , δ s , δ t They are the contact displacements in three directions.

[0060] The quadratic stress criterion is used as the damage initiation criterion:

[0061]

[0062] Where, are the peak stresses in the normal and two tangential directions, respectively.

[0063] After the initial damage occurs, the interface stiffness degradation rate is described by the damage evolution criterion:

[0064]

[0065] Where, is the contact stress without considering damage.

[0066] Under the linear damage criterion, the damage variable D follows the following evolution law:

[0067]

[0068] Where, is the effective contact displacement at complete destruction; is the maximum effective contact displacement of the contact during the loading process; is the effective contact displacement when initial damage occurs.

[0069] In the above steps, the uniaxial tensile test is specifically as follows: test blocks A8-1 and B8-2 are used to simulate bin blocks A1-1 and B1-2 respectively. The casting time sequence and interface treatment method are the same as the actual project. The two ends of bin blocks A1-1 and B1-2 are bonded and fixed on the upper bracket 10-1 and the lower bracket 10-2 respectively. A universal testing machine is used to support the two ends of the upper and lower brackets 10-2. The force and displacement data are read synchronously during the loading process.

[0070] In the above steps, K nn , K ss , K tt 、 The interface parameters are determined by inversion using the PSO-SVM algorithm;

[0071] The specific steps include:

[0072] S1: Start;

[0073] S2: Determine the value range of the interface parameters as shown in Table 1.

[0074] S3: Use the LHS sampling algorithm to extract and set the parameter combinations used in the uniaxial tension numerical model. A total of n groups of parameter combinations are extracted and set:

[0075] S4: According to the uniaxial tensile test of the compartment joint ( Figure 3 ), establish the uniaxial tension finite element model of the compartment joint ( Figure 5 ): Test block A8-1 and test block B8-2 are simulated using test block A entity element 11-1 and test block B entity element 11-2, respectively; test contact surface 9 is simulated using contact surface 2-1 viscosity element 5, and its element parameters are set according to the parameter combination extracted in S3; upper bracket 10-1 and lower bracket 10-2 are simulated using upper bracket entity element 13-1 and lower bracket entity element 13-2, respectively; after substituting each test parameter combination, axial tensile loads are applied to both ends of upper bracket entity element 13-1 and lower bracket entity element 13-2 for simulation, thereby obtaining a sample database;

[0076] S5: Substitute the sample database into the SVM model for training. Select the kernel function of the SVM model, set the initial penalty parameters and kernel function parameters of the SVM model, and use them to initialize the PSO algorithm particle swarm;

[0077] S6: Run the PSO algorithm to calculate the individual optimum and the global optimum, calculate the particle fitness, iteratively update the particle fitness until it meets the termination condition, and then map the optimal particle to the penalty parameter and kernel function parameter of the SVM model;

[0078] S7: Input the uniaxial tension test data into the interface parameter inversion SVM model to obtain the optimal interface parameter values;

[0079] S8: Substitute the optimal interface parameters into the uniaxial tension numerical model of the compartment joint and compare with the uniaxial tension test data to verify the effect;

[0080] S9: End;

[0081] Table 1

[0082]

[0083]

[0084] Specifically in S3:

[0085] a. Divide each parameter m into n equal probability intervals:

[0086]

[0087] b. For the i-th interval, the cumulative probability of sampling can be written as:

[0088]

[0089] c. Use the inverse probability distribution function F-1 to convert the probability into a sample value x:

[0090] m i =F -1 (p i ) (7)

[0091] The n values ​​obtained for each variable m are paired with the n values ​​of the other variables randomly or in some specific order.

[0092] In the above steps, the waterproof steel plate is simulated by bushing unit 6, and the displacement-force curve of bushing unit 6 is:

[0093] p=2dlsτ(x) (8)

[0094] Where l is the anchoring length; d is the spacing of the bushing units 6; l is the length of the waterproof steel plate embedded in the bin block A1-1 or bin block B1-2; s is the circumference of the steel plate cross section within the spacing d of the steel plate; τ(x) is the bond stress curve between the steel plate and the concrete.

[0095] In the above steps, the steel bar truss unit 7 is in an embedded form.

[0096] The finite element simulation method for the foundation floor using the skip-bin method can simultaneously account for details such as the contact surface 2-1, the waterstop steel plate 2-2, and the floor reinforcement 3. It can also refine the mechanical properties of the compartment joint by simulating the bond-slip characteristics of the contact surface 2-1 and the waterstop steel plate 2-2. Furthermore, it can quickly and accurately determine the mechanical parameters of the viscous element 5. This improves the accuracy of the finite element simulation of the foundation floor using the skip-bin method.

[0097] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A finite element simulation method for the compartment seam of the foundation bottom plate using the skip-compartment method, characterized in that: The method includes the following steps: the foundation bottom plate joint structure includes block A, block B, contact surface, waterstop steel plate and bottom plate steel bar; solid units are used to simulate the blocks, viscous units are used to simulate the contact surface, bushing units are used to simulate the waterstop steel plate, and truss units are used to simulate the steel bar; the bond-slip characteristics of the joint are simulated by viscous units, and the parameters of the traction-separation constitutive model are determined by inversion using the PSO-SVM algorithm based on the results of the uniaxial tension test; the viscous unit uses the traction-separation criterion to simulate its damage evolution: at the same time, the quadratic stress criterion is used as the damage initiation criterion: after the initial damage occurs, the interface stiffness degradation rate is described by the damage evolution criterion; the uniaxial tension test is specifically as follows: test blocks A and test blocks B are used to simulate block A and block B respectively, and the casting time sequence and interface treatment method are the same as the actual engineering practice, the two ends of block A and block B are bonded and fixed on the upper bracket and the lower bracket respectively, and the upper and lower brackets are supported by a universal testing machine, and the force and displacement data are read synchronously during the loading process; the viscous unit uses the traction-separation criterion to simulate its damage evolution specifically as follows: Where, 、 、 are the stresses in the normal and two tangential directions of the contact surface; K nn , K ss , K tt are the contact stiffness in three directions respectively; 、 、 are contact displacements in three directions respectively; the secondary stress criterion is used as the damage initiation criterion as follows: Where, 、 、 are the peak stresses in the normal and two tangential directions respectively; Under the linear damage criterion, the damage variable D follows the following evolution law: Where, is the effective contact displacement at complete destruction; is the maximum effective contact displacement of the contact during the loading process; is the effective contact displacement when initial damage occurs.

2. The finite element simulation method for the foundation floor compartment joint of the skip-compartment method according to claim 1, characterized in that: K nn , K ss , K tt 、 、 、 、 The interface parameters are determined by inversion using the PSO-SVM algorithm.

3. The finite element simulation method for the foundation floor compartment joint of the skip-compartment method according to claim 2, characterized in that: The specific steps include: S1: Start; S2: Determine the value range of interface parameters; S3: Use the LHS sampling algorithm to extract and set the parameter combinations used in the uniaxial tension numerical model. A total of n groups of parameter combinations are extracted and set: S4: Based on the uniaxial tension test of the compartment joint, a uniaxial tension finite element model of the compartment joint is established: test blocks A and B are simulated using solid elements; the test contact surface is simulated using contact surface viscosity elements, and its element parameters are set according to the parameter combination extracted in S3; the upper bracket and the lower bracket are simulated using solid elements respectively. After substituting each test parameter combination, axial tension loads are applied at both ends and simulation is carried out to obtain a sample database; S5: Substitute the sample database into the SVM model for training; select the kernel function of the SVM model, set the initial penalty parameters and kernel function parameters of the SVM model, and use them to initialize the PSO algorithm particle swarm; S6: Run the PSO algorithm to calculate the individual optimum and the global optimum, calculate the particle fitness, iteratively update the particle fitness until it meets the termination condition, and then map the optimal particle to the penalty parameter and kernel function parameter of the SVM model; S7: Input the uniaxial tension test data into the interface parameter inversion SVM model to obtain the optimal interface parameter values; S8: Substitute the optimal interface parameters into the uniaxial tension numerical model of the compartment joint and compare with the uniaxial tension test data to verify the effect; S9: End.

4. The finite element simulation method for the foundation floor compartment joint of the skip-compartment method according to claim 3, characterized in that: Specifically in S3: a. Divide each parameter m into n equal probability intervals: b. For the i-th interval, the cumulative probability of sampling is written as: r u is a random number distributed in the interval (0,1); c. Use the inverse probability distribution function F -1 Convert the probabilities to sample values ​​x: The n values ​​obtained for each variable m are paired with n values ​​of the other variables randomly or in some predetermined order.

5. The finite element simulation method for the foundation floor compartment joint of the skip-compartment method according to claim 4 is characterized by: In the above steps, the steel truss element is embedded, the waterproof steel plate is simulated by the bushing element, and the displacement-force curve of the bushing element is: Where d is the spacing of the bushing units; l is the length of the water-stop steel plate embedded in the bin block A or bin block B; s is the circumference of the steel plate section within the spacing d. is the bond stress curve between steel plate and concrete.

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