Numerical calculation method and device for interface of uhpc joint based on ultra-thin unit layer and storage medium

Abstract

The application relates to a UHPC joint interface numerical calculation method, device and storage medium based on a novel ultrathin unit layer, wherein the method comprises the following steps: S1, establishing an assembly model of a UHPC plate in finite element software ABAQUS, wherein the components of the geometric model of the assembly model comprise a UHPC cast-in-place plate, a UHPC prefabricated plate, a steel mesh, and a novel ultrathin unit layer arranged between the UHPC cast-in-place plate and the UHPC prefabricated plate, and initializing model parameters; S2, simulating the model in the finite element software ABAQUS to obtain a simulation result; and S3, optimizing the model parameters according to the simulation result and an actual test result. Compared with the prior art, the application has the advantages of low cost, short cycle and the like.

Description

Technical Field

[0001] This invention relates, and in particular, to a method, apparatus, and storage medium for numerical calculation of UHPC seam interfaces based on ultrathin unit layers. Background Technology

[0002] Precast bridge construction technology is the most commonly used rapid bridge construction technology, which can minimize the adverse impact on existing traffic and improve construction quality and speed. The joints between adjacent components are the key control sections of precast bridges, and their materials and detailed structures determine the structure's durability. Ultra-high performance concrete (UHPC), as a novel cementitious material, has superior mechanical properties and durability compared to traditional concrete, making it a popular choice for wet joint connections of precast components in precast bridge construction. Currently, research on the mechanical properties of UHPC wet joints is mainly experimental, which suffers from long cycles and high costs. Therefore, it is necessary to develop a numerical simulation method that can accurately simulate the complex mechanical behavior of the wet joint area to save costs and optimize structural design parameters.

[0003] Currently, there are three common finite element models for the complex mechanical behavior of joint regions. The first is the "tied" model, which assumes shared nodes between components and no relative motion. This method greatly reduces computational costs and has good convergence, but the "tied" interface assumption ignores the characteristics of interface debonding and low strength in the joint region, leading to an overestimation of load-bearing capacity. The second model sets the contact relationship between components as axial hard contact and normal friction. This model can only explain interface behavior by changing the friction coefficient, but cannot consider the influence of various interface treatments on the mechanical behavior of the joint region. The third is the "traction-separation" model, which considers the adhesion between the material and the interface, thus enabling a more accurate simulation of the mechanical behavior of the joint region. However, for complex contact problems, the "traction-separation" model is prone to convergence issues. Furthermore, for UHPC-UHPC interfaces treated with SWM (wire mesh preprocessing), experimental data on normal stiffness components, shear stiffness components, and total plastic displacement during damage evolution are lacking, preventing the application of this model in some structures. Summary of the Invention

[0004] The purpose of this invention is to provide a numerical calculation method, device, and storage medium for UHPC joint interfaces based on a novel ultrathin unit layer. By introducing a novel ultrathin unit layer and using the fit between the load-displacement curve of the overall component and the experimental curve as the verification target, the thickness and material properties of the introduced novel ultrathin unit layer are determined, thereby accurately simulating the bending performance of the joint area treated by SWM. This model has a simple modeling method, low computational cost, and high computational accuracy. It can be used to study the influence of the material parameters and geometric parameters of each component of the assembly structure on the bending performance of the structure, solving the problems of high cost and long cycle of experimental research methods.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A numerical calculation method for UHPC joint interfaces based on ultrathin unit layers includes:

[0007] Step S1: Establish the assembly model of the UHPC slab in the finite element software ABAQUS and initialize the model parameters. The components of the geometric model of the assembly model include the UHPC cast-in-place slab, the UHPC precast slab, the steel mesh, and the novel ultra-thin unit layer between the UHPC cast-in-place slab and the UHPC precast slab.

[0008] Step S2: Simulate the model in the finite element software ABAQUS and obtain the simulation results;

[0009] Step S3: Optimize model parameters based on simulation results and actual experimental results.

[0010] Step S1 specifically includes:

[0011] Step S11: Create the geometric model of the assembly model;

[0012] Step S12: Assign material properties to each component in the geometric model. Among them, the UHPC cast-in-place slab, UHPC precast slab and the new ultra-thin unit layer all adopt the concrete damage plasticity model, and the steel bars in the steel mesh adopt the bilinear constitutive model.

[0013] Step S13: Initialize the component mesh size and perform mesh division for each component. Among them, the UHPC cast-in-place slab, UHPC precast slab and new ultra-thin unit layer all adopt eight-node hexahedral linear reduced integral elements, and the steel bars of the steel mesh adopt linear truss elements.

[0014] In step S12, the elastic modulus and axial tensile and compressive strength of the novel ultrathin unit layer are lower than those of the UHPC mixture used in the UHPC cast-in-place slab and the UHPC precast slab.

[0015] The compressive stress-strain relationship of the concrete damage plasticity model used for the UHPC cast-in-place slab and the UHPC precast slab is as follows:

[0016]

[0017] Where: x = σ c / f c , σ c and f c These represent the compressive stress and axial compressive strength of the UHPC, respectively; y = ε c / ε c0 , ε c and ε c0 These represent the concrete compressive strain and peak compressive strain, respectively; α is a correction coefficient determined experimentally, based on experimental data: α = 1.2 when 0 ≤ x ≤ 1; and α = 2.41 when 1 ≤ x.

[0018] The tensile stress-strain relationship is as follows:

[0019]

[0020] Where: σ t f is the tensile stress in concrete. t ε represents the tensile strength of concrete. t For the tensile strain of concrete, ε t0 ε represents the initial tensile strain of concrete cracking. tu This represents the ultimate tensile strain of the concrete.

[0021] Step S2 specifically includes:

[0022] Step S21: Define the contact relationship, wherein the contact property between the new ultrathin unit layer and the UHPC precast slab and the UHPC cast-in-place slab is axial hard contact, and the normal friction coefficient is set to 1.0;

[0023] Step S22: Set constraints and determine loading method, wherein the UHPC precast slab and UHPC cast-in-place slab are simply supported at both ends, one end is set as a movable hinge support, and the other end is set as a fixed hinge support;

[0024] Step S23: Set the solver, select the static general analysis step and turn on the large deformation switch.

[0025] The loading method specifically involves applying a uniformly distributed load to both ends of the plate using a displacement loading method.

[0026] Step S3 specifically includes:

[0027] Step S31: Output load-displacement curve;

[0028] Step S32: Optimize the mesh size of each component based on simulation results and actual test results. The mesh size of the area near the joint and the new ultrathin unit layer is smaller than that of other areas.

[0029] Step S33: Optimize the thickness of the new ultrathin unit layer based on the fit between the load-displacement curve of the simulation model and the experimental curve.

[0030] The initial thickness of the novel ultrathin unit layer is 30 mm.

[0031] A numerical calculation device for UHPC seam interfaces based on a novel ultrathin unit layer includes a memory, a processor, and a program stored in the memory. When the processor executes the program, it implements the method described above.

[0032] A storage medium having a program stored thereon, characterized in that the program, when executed, implements the method described above.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. By introducing a novel ultrathin unit layer and using the fit between the load-displacement curve of the overall component and the experimental curve as the verification target, the thickness and material properties of the introduced novel ultrathin unit layer are determined, thereby accurately simulating the bending performance of the joint area treated by SWM. This model has a simple modeling method, low calculation cost, and high calculation accuracy. It can be used to study the influence of the material parameters and geometric parameters of each component of the assembly structure on the bending performance of the structure, solving the problems of high cost and long cycle of experimental research methods.

[0035] 2. By setting the elastic modulus and axial tensile and compressive strength of the new ultra-thin unit layer to be lower than those of the UHPC mixture used in UHPC cast-in-place slabs and UHPC precast slabs, the mechanical properties of the joints are reflected to be worse than those of the whole specimen.

[0036] 3. A concrete damage plasticity model was adopted, which is suitable for simulating materials with different tensile and compressive yield strengths. This model introduces the concept of damage, which can well simulate the ductile behavior of concrete and is suitable for nonlinear analysis.

[0037] 4. Optimizing the mesh size and the thickness of the new ultrathin unit layer based on simulation results and actual test results can optimize the assembly model and further improve accuracy. Attached Figure Description

[0038] Figure 1 This is an overall model of the UHPC board with dovetail joints as described in the embodiment;

[0039] Figure 2This is a finite element simulation flowchart of a numerical calculation method for UHPC joint interfaces based on ultrathin unit layers, as described in this invention.

[0040] Figure 3 Specific information about the novel ultrathin unit described in the embodiments;

[0041] Figure 4 The structural load-displacement curves obtained by the numerical calculation method of UHPC joint interface based on ultrathin unit layer described in the embodiment are compared with the load-displacement curves obtained by experiments. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0043] like Figure 1 As shown, two precast UHPC slabs and one cast-in-place UHPC slab are connected by dovetail joints and reinforced with steel mesh. A novel interface treatment technology—the wire mesh method—is used at the interface between the precast and cast-in-place UHPC slabs. To investigate the bending performance, structural ductility, and post-cracking stiffness of this UHPC slab, a finite element simulation model of the structure can be established. The specific construction process of the model is as follows: Figure 2 As shown.

[0044] A numerical calculation method for UHPC joint interfaces based on ultrathin unit layers includes:

[0045] Step S1: Establish the assembly model of the UHPC slab in the finite element software ABAQUS and initialize the model parameters. The geometric components of the assembly model include the UHPC cast-in-place slab, the UHPC precast slab, the steel mesh, and a new ultra-thin unit layer between the UHPC cast-in-place slab and the UHPC precast slab. Specifically, due to the discontinuity of the structure, the strength of the wet joint area is significantly lower than the strength of the overall precast component. A new ultra-thin unit layer is introduced, and the mechanical properties of the unit are recalibrated to accurately simulate the complex mechanical behavior of the joint area, thereby enabling a more accurate simulation of the bending performance of the overall component.

[0046] Step S1 specifically includes:

[0047] Step S11: Create the geometric model of the assembly model, in which the new ultra-thin unit layer is located between the UHPC cast-in-place slab and the UHPC precast slab. The initial proposed thickness of the new ultra-thin unit layer is 30mm. The steel mesh consists of longitudinal U-shaped bars and transverse steel bars. The longitudinal bar spacing is 95mm, the longitudinal U-shaped bar lap length is 150mm, and the transverse bar spacing is 100mm.

[0048] Step S12: Assign material properties to each component in the geometric model. The UHPC cast-in-place slab, UHPC precast slab, and new ultrathin unit layer all adopt the concrete damage plasticity (CDO) model. The steel bars in the steel mesh adopt the bilinear constitutive model. The CDO model is suitable for simulating materials with different tensile and compressive yield strengths. This model introduces the concept of damage, which can well simulate the ductile behavior of concrete and is suitable for nonlinear analysis.

[0049] In step S12, the elastic modulus and axial tensile and compressive strength of the new ultrathin unit layer are lower than those of the UHPC mixture used in the UHPC cast-in-place slab and UHPC precast slab.

[0050] The compressive stress-strain relationship of the concrete damage plasticity model used for UHPC cast-in-place slabs and UHPC precast slabs is as follows:

[0051]

[0052] Where: x = σ c / f c , σ c and f c These represent the compressive stress and axial compressive strength of the UHPC, respectively; y = ε c / ε c0 , ε c and ε c0 These represent the concrete compressive strain and peak compressive strain, respectively; α is a correction coefficient determined experimentally, based on experimental data: α = 1.2 when 0 ≤ x ≤ 1; and α = 2.41 when 1 ≤ x.

[0053] The tensile stress-strain relationship is as follows:

[0054]

[0055] Where: σ t f is the tensile stress in concrete. t ε represents the tensile strength of concrete. t For the tensile strain of concrete, ε t0 ε represents the initial tensile strain of concrete cracking. tu This represents the ultimate tensile strain of the concrete.

[0056] Step S13: Initialize the component mesh size and mesh each component. Among them, the UHPC cast-in-place slab, UHPC precast slab and new ultra-thin unit layer all adopt eight-node hexahedral linear reduced integral element (C3D8R), and the steel bars of the steel mesh adopt linear truss element (T3D2).

[0057] Step S2: Simulate the model in the finite element software ABAQUS and obtain the simulation results;

[0058] Step S2 specifically includes:

[0059] Step S21: Define the contact relationships. The contact property between the novel ultrathin unit layer and the UHPC precast slab and UHPC cast-in-place slab is axial hard contact, with a normal friction coefficient set to 1.0. The contact between the novel ultrathin unit layer and the UHPC precast slab and UHPC cast-in-place slab is surface-to-surface contact. Considering that the interface treatment using wire mesh fully utilizes the fiber bridging effect of UHPC and enhances the interface roughness, the normal friction coefficient is set to 1.0. Specific information about the novel ultrathin unit layer, including its constitutive relationship and contact relationship with the UHPC slab, is as follows: Figure 3 As shown.

[0060] Step S22: Set constraints and determine the loading method. The UHPC precast slab and UHPC cast-in-place slab are simply supported at both ends, with one end set as a movable hinge support and the other end set as a fixed hinge support. The loading method is as follows: uniformly distributed load is applied to both ends of the slab using displacement loading.

[0061] Step S23: Set the solver, select the static general analysis step and turn on the large deformation switch.

[0062] Step S3: Optimize model parameters based on simulation results and actual experimental results.

[0063] Step S3 specifically includes:

[0064] Step S31: Output load-displacement curves: Output the mid-span displacement of the plate and the history curves of the applied load, and plot the load-displacement curves of the UHPC plate.

[0065] Step S32: Optimize the mesh size of each component based on simulation and actual experimental results. Specifically, the mesh size near the joint area and the new ultrathin element layer should be smaller than that of other areas. The mesh should be refined based on the initially determined mesh size, especially near the joint area and the new ultrathin element layer. This ensures mesh independence of the solution and minimizes computational cost.

[0066] Initially, the mesh size for the panels far from the joints was set at 50mm, and the mesh size for the panels near the joints was set at 25mm. Based on this initial mesh size, the mesh sizes for both the areas far from and near the joints were refined. Further mesh refinement did not change the structural mechanical response, thus ensuring mesh independence. Mesh sensitivity testing ultimately determined the overall mesh size for the panels to be 50mm, and the mesh size for the areas near the joints to be 15mm.

[0067] Step S33: Optimize the thickness of the new ultrathin unit layer based on the fit between the load-displacement curve of the simulation model and the experimental curve.

[0068] The structural bending resistance is highly sensitive to the thickness of the unit layer. An initial unit layer thickness of 30mm was proposed. The thickness was gradually reduced using the fit between the simulation model's load-displacement curve and the experimental curve as a criterion, until a reasonable unit layer thickness was found. Further reduction of the unit layer thickness beyond this point had almost no impact on the structural bending resistance. When the thickness of the new ultrathin unit layer was reduced to 5mm, further reduction had almost no effect on the mechanical response of the structure. At this point, the load-displacement curve obtained from the simulation model was close to the experimental curve. Therefore, the final thickness of the new ultrathin unit layer for this structure was determined to be 5mm.

[0069] When the thickness of the novel ultrathin unit layer is 5mm, the structural load displacement obtained by the numerical calculation method of the UHPC joint interface based on the ultrathin unit layer is as follows: Figure 4 As shown. Compared to traditional simulation models (which do not introduce the new ultrathin unit layer), the numerical calculation method for UHPC seam interfaces based on the ultrathin unit layer can accurately simulate the bending performance of UHPC boards with seams.

[0070] In this application, the principle for optimizing the thickness of the novel ultrathin unit layer is as follows: after applying a load, the structure only has two main cracks in a joint area, but the introduction of the unit layer will cause new main cracks to appear in the joint area. With the appearance of new main cracks, the bending resistance of the structure decreases. Reducing the thickness of the unit layer helps to mitigate the impact of additional cracks on stiffness and bending resistance. However, if the unit layer thickness is too small, the mesh quality of the divided elements is prone to be poor, and the mesh distortion structure is difficult to converge. Therefore, it is necessary to use the fit between the load-displacement curve of the simulation model and the experimental curve as a judgment index to find a reasonable unit layer thickness, thereby reducing the impact of new main cracks generated with the introduction of the unit layer on the structural stiffness and load-bearing capacity and avoiding convergence problems during structural calculation.

[0071] In summary, this application proposes a numerical calculation method for UHPC joint interfaces based on ultrathin unit layers. By introducing a novel ultrathin unit layer, the flexural performance of UHPC slabs with wet joints is well simulated. This method provides a modeling approach that can accurately simulate the mechanical properties of concrete slabs (including UHPC and ordinary concrete) with joints, which can solve problems such as long experimental cycles and high costs in actual experiments. Moreover, structural design parameters can be optimized based on this numerical calculation method.

[0072] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

Claims

1. A numerical calculation method for UHPC joint interfaces based on ultrathin unit layers, characterized in that, include: Step S1: Establish the assembly model of the UHPC slab in the finite element software ABAQUS and initialize the model parameters. The components of the geometric model of the assembly model include the UHPC cast-in-place slab, the UHPC precast slab, the steel mesh, and the novel ultra-thin unit layer between the UHPC cast-in-place slab and the UHPC precast slab. Step S2: Simulate the model in the finite element software ABAQUS and obtain the simulation results; Step S3: Optimize model parameters based on simulation results and actual experimental results; Step S3 specifically includes: Step S31: Output load-displacement curve; Step S32: Optimize the mesh size of each component based on simulation results and actual test results. The mesh size of the area near the joint and the new ultrathin unit layer is smaller than that of other areas. Step S33: Optimize the thickness of the new ultrathin unit layer based on the fitting between the load-displacement curve of the simulation model and the experimental curve.

2. The numerical calculation method for UHPC seam interface based on ultrathin unit layer according to claim 1, characterized in that, Step S1 specifically includes: Step S11: Create the geometric model of the assembly model; Step S12: Assign material properties to each component in the geometric model. Among them, the UHPC cast-in-place slab, UHPC precast slab and the new ultra-thin unit layer all adopt the concrete damage plasticity model, and the steel bars in the steel mesh adopt the bilinear constitutive model. Step S13: Initialize the component mesh size and mesh each component. The UHPC cast-in-place slab, UHPC precast slab and new ultra-thin unit layer all use eight-node hexahedral linear reduced integral elements, and the steel bars of the steel mesh use linear truss elements.

3. The numerical calculation method for UHPC seam interface based on ultrathin unit layer according to claim 2, characterized in that, In step S12, the elastic modulus and axial tensile and compressive strength of the novel ultrathin unit layer are lower than those of the UHPC mixture used in the UHPC cast-in-place slab and UHPC precast slab.

4. The numerical calculation method for UHPC joint interface based on ultrathin unit layer according to claim 3, characterized in that, The compressive stress-strain relationship of the concrete damage plasticity model used for the UHPC cast-in-place slab and the UHPC precast slab is as follows: Where: x =σ c / f c , σ c and f c These represent the compressive stress and axial compressive strength of the UHPC, respectively; y= ε c / ε c0 , ε c and ε c0 These represent the concrete compressive strain and peak compressive strain, respectively; α is a correction coefficient determined experimentally, based on experimental data: α = 1.2 when 0 ≤ x ≤ 1; α = 2.41 when 1 < x. The tensile stress-strain relationship is as follows: in: σ t For the tensile stress of concrete, f t The tensile strength of concrete, ε t For the tensile strain of concrete, ε t0 For the initial tensile strain of concrete cracking, ε tu This represents the ultimate tensile strain of the concrete.

5. The numerical calculation method for UHPC joint interface based on ultrathin unit layer according to claim 1, characterized in that, Step S2 specifically includes: Step S21: Define the contact relationship, wherein the contact property between the new ultrathin unit layer and the UHPC precast slab and the UHPC cast-in-place slab is axial hard contact, and the normal friction coefficient is set to 1.0; Step S22: Set constraints and determine loading method, wherein the UHPC precast slab and UHPC cast-in-place slab are simply supported at both ends, one end is set as a movable hinge support, and the other end is set as a fixed hinge support; Step S23: Set the solver, select the static general analysis step and turn on the large deformation switch.

6. The numerical calculation method for UHPC joint interface based on ultrathin unit layer according to claim 5, characterized in that, The loading method is specifically as follows: a displacement loading method is used to apply a uniformly distributed load to both ends of the plate.

7. The numerical calculation method for UHPC seam interface based on ultrathin unit layer according to claim 1, characterized in that, The initial thickness of the novel ultrathin unit layer is 30 mm.

8. A numerical calculation device for UHPC seam interfaces based on a novel ultrathin unit layer, comprising a memory, a processor, and a program stored in the memory, characterized in that, When the processor executes the program, it implements the method as described in any one of claims 1-7.

9. A storage medium having a program stored thereon, characterized in that, When the program is executed, it implements the method as described in any one of claims 1-7.

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