Method and system for establishing a modified continuous damage plasticity constitutive model of UHPC under multi-axial constraint

Abstract

The application provides a method and system for revising a continuous damage plastic constitutive model of UHPC under multi-axial constraint, which can comprehensively describe the behavior of UHPC under passive constraint and effectively simulate complex FRP-UHPC composite structures. The method comprises the following steps: step 1, determining a yield criterion; considering the introduction of steel fibers and coarse aggregates and the influence of constraint, a yield function of the revised CDP model is proposed; step 2, determining a hardening and softening criterion; considering the constraint effect of UHPC, the content of aggregate, the content of fiber and residual stress, a stress-strain model of the revised CDP of UHPC is proposed, and a hardening / softening function is obtained; step 3, determining a plastic flow criterion; considering the influence of constraint, plastic history and scale parameter on plastic flow, the CDP model is revised by using an improved dilatancy angle parameter; and step 4, determining a damage evolution law; the damage evolution process in the CDP model is revised.

Description

Technical Field

[0001] This invention belongs to the field of fiber-reinforced concrete simulation technology, specifically relating to a method and system for establishing a UHPC modified continuous damage plastic constitutive model under multiaxial constraints. Background Technology

[0002] UHPC-filled fiberglass cylindrical column components are favored for their excellent corrosion resistance and high load-bearing capacity. However, due to limitations in measurement methods, the underlying working mechanisms of these elements cannot be fully understood without a suitable numerical approach.

[0003] Previous finite element models have been effective for plain concrete fiberglass tube column elements. For example, the recognized concrete damage-plasticity (CDP) model can be used. Alternatively, a modified concrete hardening law can be employed, taking into account the impact of constraints on load-bearing capacity in advance, which can accurately describe the load-bearing capacity of the structure with less computation time. Existing solutions have greatly facilitated the simulation research of UHPC-filled fiberglass tube column elements, but they are also subject to many limitations. They cannot simulate the behavior of UHPC under passive constraints, and it is difficult to accurately model complex FRP (fiber reinforced plastic)-UHPC composite structures, thus making it impossible to effectively predict stress-strain relationships based on model simulation. Summary of the Invention

[0004] This invention is made to solve the above-mentioned problems. Its purpose is to provide a method and system for establishing a modified continuous damage plastic constitutive model of UHPC under multiaxial constraints, which can comprehensively describe the behavior of UHPC under passive constraints, effectively simulate complex FRP-UHPC composite structures, and accurately predict stress-strain relationships.

[0005] To achieve the above objectives, the present invention adopts the following solution:

[0006] <Method>

[0007] like Figure 1 As shown, the present invention provides a method for establishing a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints, characterized by comprising the following steps:

[0008] Step 1: Determine the yield criterion;

[0009] The introduction of steel fibers and coarse aggregates affects concrete properties by bridging cracks and defects, thus influencing the initial yield and yield surface migration of UHPC. Furthermore, constraints affect the yield surface migration by closing cracks and increasing friction on the damaged surface. Considering the effects of the introduction of steel fibers and coarse aggregates, as well as the effects of constraints, a modified yield function for the CDP model is proposed:

[0010]

[0011] In the formula, such as Figure 2 As shown, α is the yield surface shape parameter, determined by experimental results of UHPC under biaxial and uniaxial compression conditions. These represent effective compressive cohesion and effective tensile cohesion, respectively. For Mises equivalent stress, For hydrostatic pressure, For the maximum effective principal stress, For plastic strain, the subscript c indicates compression; the subscript t indicates tension, σ r For the confining stress (i.e., confining pressure), K c V is the ratio of the second stress invariant on the tensile meridian to the second stress invariant on the compressive meridian of the pressure invariant p (which typically controls the shape of the yield surface off the stress plane) on the initial yield surface; f V represents fiber content. ca This refers to the coarse aggregate content; such as... Figure 2 As shown, α and K c Two parameters control the shape of the yield surface; such as Figure 3 As shown, based on the comparison between the yield surface and the experimental results, when α=0.083(σ b0 / σ c0 When =1.1), the shape of the yield surface is basically consistent with the experimental results;

[0012] Step 2, determine the hardening and softening criteria;

[0013] Considering the UHPC constraint effect, aggregate content, fiber content, and residual stress, a stress-strain model for UHPC-corrected CDP is proposed:

[0014]

[0015] In the formula, ε c and σ c ε represents axial compressive strain and axial compressive stress, respectively. c,r with f c,+ Let λ1 and λ2 represent the axial compressive strain and axial compressive stress under confining pressure, respectively. n and A control the slopes of the ascending and descending segments, respectively. Two parameters, λ1 and λ2, are used to describe the influence of constraints on the ascending and descending segments, respectively.

[0016]

[0017] A=λ2(b1V ca +b2V f +b3(f c -80)+b4)f c ≥80,

[0018]

[0019] In the formula, This represents the confining pressure; b1 to b8 are all constants, determined experimentally.

[0020] Based on the stress-strain model above, the hardening / softening function is obtained. σ min Let q be the minimum principal stress under the current stress condition, and q be the minimum deflection stress under the current stress condition; the stress-inelastic strain curve of the hardening / softening function is as follows: Figure 6 As shown.

[0021] Step 3: Determine the plastic flow criterion;

[0022] The uncorrelated plastic flow used in the CDP model is:

[0023]

[0024]

[0025] In the formula, G is the flow potential, i.e., the Drucker-Prager hyperbolic function; e represents the rate at which the function approaches the asymptote, usually represented by 0.1; σ t0 The failure stress of the material under uniaxial tension; The expansion angle, measured in the pq plane, is the angle of the linear Drucker-Prager potential and controls plastic flow rate, such as... Figure 7 As shown;

[0026] Considering the influence of constraints, plastic history, and proportional parameters on plastic flow, an improved expansion angle parameter is adopted.

[0027]

[0028] In the formula, V f and V ca The parameter D is considered in an incremental manner:

[0029] Step 4: Determine the damage evolution pattern;

[0030] Damage evolution in the modified CDP model is described by the following equation:

[0031]

[0032] In the formula, σ peak For the peak stress of UHPC, σ *The stress represents the axial stress after the peak value; the relationship between damage and axial strain can be determined through the stress-strain relationship; the stress-strain relationship proposed in this invention is used to determine the relationship between damage and axial strain. A typical damage evolution curve is shown below. Figure 9 As shown.

[0033] Step 5: Based on steps 1 to 4 above, construct a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints.

[0034] Preferably, in the method for establishing a modified UHPC continuous damage plastic constitutive model under multiaxial constraints provided by the present invention, in step 1, under isobaric lateral pressure triaxial compression, the yield surface function of the modified CDP model is:

[0035]

[0036] Preferably, in the method for establishing a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints provided by the present invention, in step 1, the parameter K... c The expression is:

[0037] K c =a1V f +a2,

[0038] In the formula, a1 and parameter a2 are both constants, determined experimentally. Experimental results and suggested yield surfaces, for example... Figure 4 As shown.

[0039] Preferably, in the method for establishing a UHPC modified continuous damage plastic constitutive model under multiaxial constraints provided by the present invention, it is suggested that in step 1, the values ​​be a1 = 0.01 and a2 = 0.7.

[0040] Preferably, in the method for establishing a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints provided by the present invention, in step 2, the compressive stress-strain relationship under multiaxial conditions is as follows:

[0041]

[0042]

[0043]

[0044]

[0045] In the formula, For effective stress components, the subscripts i = 1, 2, 3 indicate the directions of the three principal stresses; For equivalent plastic strain rate, and These are the maximum and minimum equivalent plastic strain rates, respectively.

[0046] Preferably, the method for establishing a modified continuous damage plastic constitutive model of UHPC under multiaxial constraints provided by the present invention may also have the following characteristics: In step 2, when no constraints are applied, λ1=λ2=1, and as the constraints increase, the parameters gradually approach zero; based on the experimental results of UHPC under multiaxial conditions and a large number of numerical calculations, the suggested values ​​for b1~b6 are: b1=0.015, b2=-0.85, b3=0.013, b4=3.99, b5=0.055, b6=0.017, b7=11, b8=18.18, which can obtain higher calculation accuracy. A comparison of the stress-strain curves of UHPC under constraints in simulation and experimental results is shown below. Figure 5 As shown.

[0047] Preferably, in the method for establishing a modified continuous damage plastic constitutive model of UHPC under multiaxial constraints provided by the present invention, in step 3, the expression for predicting the transverse plastic strain of UHPC under constraints is as follows:

[0048]

[0049] In the formula, the subscript x represents the axial direction, the subscripts y and z represent the two lateral directions, η1 and η2 respond to the effects of aggregate content and fiber content, respectively, and the ω parameter is the constraint effect factor of UHPC; under constraint conditions, the lateral plastic strain development of UHPC is relatively slow, and ω is determined by the following formula:

[0050]

[0051] In the formula, c1, c2, and c3 are constants that determine the influence of constraints on UHPC, and are determined experimentally.

[0052] The formulas for calculating η1 and η2 are:

[0053] L1=g1V ca +g2,

[0054] η2=g3V f +g4,

[0055] In the formula, g1 to g4 are all constants, determined experimentally. A comparison between the directional plastic strain model and the research results is shown below. Figure 8 As shown, the lines represent the lateral plastic strain-axial plastic strain curves of the established model, and the points represent the experimental results of previous studies. The results demonstrate that the model proposed in this invention can accurately predict most cases with different scaling parameters and constraints.

[0056] To establish parameters The relationship with other parameters is derived using the chain rule under isolateral pressure triaxial compression conditions. The plastic strain increment is:

[0057]

[0058] In the formula, θ is the unit vector matrix, which controls the direction of plastic flow. It is assumed that under the same plastic strain... Below, the plastic flow direction of the CDP model is consistent with the experimental results, and the relationship between the two is as follows:

[0059]

[0060] In the formula, Table 22 below represents the y-axis direction; 11 represents the x-axis direction.

[0061] Preferably, in the method for establishing a UHPC modified continuous damage plastic constitutive model under multiaxial constraints provided by the present invention, in step 3, the suggested values ​​for c1 to c3 are: c1 = 0.045, c2 = 5.153, c3 = 0.624; and the suggested values ​​for g1 to g4 are: g1 = 0.482, g2 = 6.4, g3 = 0.085, g4 = 1.21.

[0062] Preferably, the method for establishing a modified continuous damage plastic constitutive model of UHPC under multiaxial constraints provided by the present invention further includes: step 6, predicting the stress-strain relationship under different proportional parameters, different fiber content and coarse aggregate content, and different constraint conditions based on the modified continuous damage plastic constitutive model of UHPC under multiaxial constraints.

[0063] The method described above can be implemented in ABAQUS using the user subroutine USDFLD, with a corresponding UMAT subroutine written. This process first provides the UHPC with constant scaling and basic mechanical property parameters. Then, before each iteration, the parameters of the CDP model are corrected, taking into account variations in plasticity and stress conditions.

[0064] <System>

[0065] Furthermore, this invention also provides a system for establishing a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints, capable of automatically implementing the above-mentioned <method>, characterized in that it includes:

[0066] Yield setting section, determining the yield criterion; considering the introduction of steel fibers and coarse aggregate, as well as the influence of constraints, a modified yield function for the CDP model is proposed:

[0067]

[0068] In the formula, α is the yield surface shape parameter, determined by experimental results of UHPC under biaxial and uniaxial compression conditions. These represent effective compressive cohesion and effective tensile cohesion, respectively. Mises equivalent stress For hydrostatic pressure, For the maximum effective principal stress, For plastic strain, the subscript c indicates compression; the subscript t indicates tension, σ r For constrained stress, K c It is the ratio of the second stress invariant p on the tensile meridian to the second stress invariant on the compressive meridian at the initial yield surface; V f V represents fiber content. ca This refers to the coarse aggregate content;

[0069] The hardening and softening settings are defined, and the hardening and softening criteria are determined. Considering the UHPC constraint effect, aggregate content, fiber content, and residual stress, a stress-strain model for UHPC-modified CDP is proposed.

[0070]

[0071] In the formula, n and A control the slopes of the rising and falling segments, respectively; two parameters λ1 and λ2 are used to describe the influence of constraints on the rising and falling segments, respectively:

[0072]

[0073] A=λ2(b1V ca +b2V f +b3(f c -80)+b4)f c ≥80,

[0074]

[0075] In the formula, ε0=0.75(f c ) 0.31 , b1 to b8 are all constants, determined experimentally.

[0076] Based on the stress-strain model above, the hardening / softening function is obtained. σ min is the minimum principal stress under the current stress condition, and q is the minimum deflection stress under the current stress condition;

[0077] The plastic flow setting section determines the plastic flow criteria; considering the influence of constraints, plastic history, and proportional parameters on plastic flow, an improved expansion angle parameter is adopted.

[0078]

[0079] In the formula, V f and V ca The parameter D is considered in an incremental manner:

[0080] The damage evolution setting section determines the damage evolution law; the damage evolution in the modified CDP model is described by the following equation:

[0081]

[0082] In the formula, σ peak For the peak stress of UHPC, σ * The axial stress is the stress after the peak value; the relationship between damage and axial strain can be determined through the stress-strain relationship.

[0083] The model construction section constructs a UHPC modified continuous damage plastic constitutive model under multiaxial constraints based on the yield setting section, hardening and softening setting section, plastic flow setting section, and damage evolution setting section.

[0084] The control unit is communicatively connected to the yield setting unit, hardening and softening setting unit, plastic flow setting unit, damage evolution setting unit, and model construction unit, and controls their operation.

[0085] Preferably, the system for establishing a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints provided by the present invention may further include: an input display unit, which is communicatively connected to the control unit, for allowing the user to input operation commands and displaying them accordingly.

[0086] The role and effect of invention

[0087] This invention relates to a method and system for establishing a modified continuous damage plastic constitutive model of UHPC under multiaxial constraints. It fully considers the influence of the introduction, constraint, aggregate content, fiber content, and residual stress of steel fibers and coarse aggregate under actual conditions. The yield criterion, hardening and softening criterion, plastic flow criterion, and damage evolution law in the CDP model have all been improved (modified). A modified continuous damage plastic constitutive model of UHPC has been established. This model can comprehensively describe and simulate the behavior of UHPC with different fiber and coarse aggregate contents under passive constraints. It can accurately construct models of complex FRP (fiber reinforced polymer)-UHPC composite structures, thereby accurately simulating and predicting stress-strain relationships under different proportional parameters, fiber and coarse aggregate contents, constraint conditions, and stresses. This provides a scientific and reliable tool for performance research and safety studies of FRP-UHPC composites in engineering applications. Attached Figure Description

[0088] Figure 1The flowchart of the method for establishing a UHPC modified continuous damage plastic constitutive model under multiaxial constraints, as disclosed in this invention, is shown below.

[0089] Figure 2 This is a schematic diagram of the shape of the yield surface involved in the present invention;

[0090] Figure 3 This is a comparison diagram of the proposed yield surface and experimental results under biaxial and uniaxial conditions as described in the present invention;

[0091] Figure 4 This is a comparison diagram of the proposed yield surface under triaxial conditions and the experimental results involved in this invention.

[0092] Figure 5 This is a comparison diagram of experimental and simulation stress-strain curves of UHPC under constrained conditions, as per the present invention.

[0093] Figure 6 This is a schematic diagram of the stress-inelastic strain curve of the hardening / softening function involved in the present invention;

[0094] Figure 7 This is a schematic diagram of the flow potential of the CDP model involved in the present invention in the principal stress space and the pq plane;

[0095] Figure 8 This is a comparison diagram between the directional plastic strain model and experimental research results involved in this invention;

[0096] Figure 9 This is a schematic diagram of the damage evolution curve involved in the present invention;

[0097] Figure 10 This refers to a single finite element model as described in Embodiment 1 of the present invention;

[0098] Figure 11 The figures show a comparison between the axial stress-axial strain curve (a) and the lateral strain-axial stress curve (b) obtained by simulating a single finite element using the modified CDP model (CDPM-R) and the CDP model (CDPM) in Embodiment 1 of the present invention and the proposed constitutive model.

[0099] Figure 12 This is the finite element model of the UHPC-filled FRP cylindrical column involved in Embodiment 2 of the present invention.

[0100] Figure 13This is a comparison chart of the normalized load-strain curve and the experimental curve obtained by simulating the UHPC-filled FRP cylinder model using the modified CDP model (CDPM-R) and the CDP model (CDPM) in Embodiment 2 of the present invention. Among them, (a) is a typical specimen of C-12#-20-85-4, and (b) is a typical specimen of C-12#-20-50-4. Detailed Implementation

[0101] The following describes in detail, with reference to the accompanying drawings, the specific implementation scheme of the method and system for establishing a UHPC modified continuous damage plastic constitutive model under multiaxial constraints, which is involved in this invention.

[0102] <Example 1>

[0103] The purpose of this first embodiment is to verify the effectiveness of the improved concrete continuous damage plastic constitutive model (UHPC modified continuous damage plastic constitutive model, hereinafter referred to as the modified CDP model) for finite element calculations. A single finite element model (computation length of 1) under triaxial compression conditions was established, and numerical verification was performed. Figure 10 As shown.

[0104] The axial stress-axial strain curves and lateral strain-axial stress curves obtained from the modified CDP model (CDPM-R) of this invention and the prior art CDP model (CDPM) were compared with the proposed constitutive model. Figure 11 As shown, the results indicate that the CDP model (CDPM, short dashed line) cannot accurately simulate the behavior of UHPC under multiaxial conditions, and the deviation from the experimental results (solid line) increases rapidly. On the other hand, the modified CDP model (CDPM-R, long dashed line) can accurately characterize the stress-strain relationship of UHPC under multiaxial conditions, as well as its lateral behavior at most constraint levels.

[0105] <Example 2>

[0106] like Figure 12As shown, the purpose of this second embodiment is to verify the effectiveness of the improved concrete continuous damage plastic model (UHPC modified continuous damage plastic constitutive model) for calculating UHPC short column members. A finite element model of a UHPC-filled FRP tube column was established. The column height is 600mm, and the FRP tube thickness is 4mm. The C3D8I element can better describe the out-of-plane bending behavior of the FRP tube. The shell component embedded in the UHPC is used with S4R elements to simulate the stress behavior of the profile. Two rigid loading plates are used to ensure uniform loading. The hard contact interaction between the FRP tube and the UHPC is considered, and the friction behavior is described by the penalty function at the interface between the two. Tangential hard contact and friction are set to consider the interaction between the ends of each component and the rigid loading plate. The mesh size of the FRP tube is 5mm in the longitudinal direction and 1mm in the radial direction. The mesh size of the UHPC and the profile is 5mm.

[0107] Select the same type of UHPC (steel fiber V) f =2%, aggregate V ca Two typical specimens, C-12#-20-85-4 and C-12#-20-50-4, cast with a 20% (=) ratio, were used for model verification using different outer fiberglass tubes (winding angles of 85° and 50°, representing samples with strong and weak constraints, respectively). Figure 13 As shown, the results indicate that the modified CDP model (CDPM-R, long dashed line) of the present invention can better simulate the shape of the experimental load-strain curve (solid line), especially the slope and constraint reinforcement after the peak load. In contrast, the existing CDP model (CDPM, short dashed line) shows a rapid drop in the curve after the peak load, with significant stress degradation, which differs greatly from the experimental curve.

[0108] <Example 3>

[0109] In this third embodiment, a system is provided that can automatically implement the above-mentioned method of the present invention to establish a UHPC modified continuous damage plastic constitutive model under multiaxial constraints. The system includes a yield setting unit, a hardening and softening setting unit, a plastic flow setting unit, a damage evolution setting unit, a model construction unit, an input display unit, and a control unit.

[0110] The yield setting section performs the steps described in step 1 above, taking into account the introduction of steel fibers and coarse aggregates as well as the influence of constraints, and proposes a modified yield function for the CDP model.

[0111] The hardening and softening setting section performs the steps described in step 2 above, considering the UHPC constraint effect, aggregate content, fiber content, and residual stress, and proposes a stress-strain model for the UHPC modified CDP, and obtains the hardening / softening function.

[0112] The plastic flow setting unit performs the steps described in step 3 above, taking into account the influence of constraints, plastic history, and scaling parameters on plastic flow, and describes the plastic flow.

[0113] The damage evolution setting unit performs the steps described in step 4 above to determine the damage evolution law.

[0114] The model construction unit performs the steps described in step 5 above, and constructs a UHPC modified continuous damage plastic constitutive model under multiaxial constraints based on the yield setting unit, hardening and softening setting unit, plastic flow setting unit, and damage evolution setting unit.

[0115] The input display unit is connected to the control unit and is used to allow users to input operation commands and display the corresponding information. For example, the input and output data and processing procedures of each unit can be displayed in the form of text, tables, static or dynamic graphs, or two-dimensional or three-dimensional models.

[0116] The control unit is communicatively connected to the yield setting unit, hardening and softening setting unit, plastic flow setting unit, damage evolution setting unit, model building unit, and input display unit, controlling their operation.

[0117] The above embodiments are merely illustrative examples of the technical solutions of the present invention. The method and system for establishing a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints involved in the present invention are not limited to the content described in the above embodiments, but are defined by the scope of the claims. Any modifications, additions, or equivalent substitutions made by those skilled in the art based on these embodiments are within the scope of protection claimed by the claims of the present invention.

Claims

1. A method for establishing a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints, characterized in that, Includes the following steps: Step 1: Determine the yield criterion; Considering the introduction of steel fibers and coarse aggregate, as well as the influence of constraints, a modified yield function for the CDP model is proposed: In the formula, , , , and These represent effective compressive cohesion and effective tensile cohesion, respectively. For Mises equivalent stress, For hydrostatic pressure, For the maximum effective principal stress, For plastic strain, subscript c Indicates pressure; subscript t Indicates being pulled, σ r To constrain stress, K c It is a pressure invariant p The ratio of the second stress invariant on the tensile meridian to the second stress invariant on the compressive meridian at the initial yield surface; V f Fiber content, V ca This refers to the coarse aggregate content; Step 2, determine the hardening and softening criteria; Considering the UHPC constraint effect, aggregate content, fiber content, and residual stress, a stress-strain model for UHPC-corrected CDP is proposed: In the formula, x = , y = , and These represent axial compressive strain and axial compressive stress, respectively. and These represent the axial compressive strain and axial compressive stress under constrained stress, respectively. n and A The slopes of the rising and falling segments are controlled separately; two parameters are used. λ 1 and λ 2. Describe the effects of constraints on the rising and falling segments respectively: In the formula, , , ; Based on the stress-strain model above, the hardening / softening function is obtained. , , The minimum principal stress under the current stress condition. q This represents the minimum deflection stress under the current stress conditions. Step 3: Determine the plastic flow criterion; Considering the influence of constraints, plastic history, and proportional parameters on plastic flow, an improved expansion angle parameter is adopted. The plastic flow process in the modified CDP model; ， In the formula, , V f and V ca In parameters D The approach is to consider the incremental aspects: ; Step 4: Determine the damage evolution pattern; Damage evolution in the modified CDP model is described by the following equation: ， In the formula, This represents the peak stress of the UHPC. This refers to the axial stress after the peak value. The relationship between damage and axial strain can be determined through stress-strain relationships; Step 5: Based on steps 1 to 4 above, construct a UHPC modified continuous damage plastic constitutive model under multiaxial constraints.

2. The method for establishing a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints according to claim 1, characterized in that: in, In step 1, parameters K c The expression is: In the formula, a 1 and parameters a Both 2 are constants, determined experimentally.

3. The method for establishing a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints according to claim 2, characterized in that: in, In step 1, parameters a 1 = 0.01 a 2 = 0.

7.

4. The method for establishing a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints according to claim 1, characterized in that: in, In step 2, the compressive stress-strain relationship under multiaxial conditions is as follows: ， ， ， ， In the formula, , , For effective stress components, subscript i =1, 2, 3 represent the three principal stress directions; For equivalent plastic strain rate, and These are the maximum and minimum equivalent plastic strain rates, respectively.

5. The method for establishing a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints according to claim 1, characterized in that: in, In step 2, for: , , , , , , , .

6. The method for establishing a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints according to claim 1, characterized in that: in, In step 3, the expression for predicting the transverse plastic strain of UHPC under constraints is: ， In the formula, the subscript x Indicates the axial direction, subscript y and z Indicates two sides, η 1 and η 2. Responding to the effects of aggregate content and fiber content, respectively ω The parameter is the constraint effect factor of UHPC; under constraint conditions, the transverse plastic strain development of UHPC is relatively slow. ω Determined by the following formula: ， In the formula, c 1. c 2. c 3 is a constant that determines the effect of constraints on UHPC, which is determined experimentally; η 1 and η 2. The calculation formula is: In the formula, g 1~ g 4 are all constants, determined experimentally.

7. The method for establishing a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints according to claim 6, characterized in that: in, In step 3, c 1~ c Recommended value for 3: c 1 = 0.045, c 2 = 5.153, c 3 = 0.624; g 1~ g 4. Recommended value: g 1 = 0.482, g 2 = 6.4, g 3 = 0.085, g 4 = 1.

21.

8. The method for establishing a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints according to claim 1, characterized in that, Also includes: Step 6: Based on the UHPC modified continuous damage plastic constitutive model under multiaxial constraints, predict the stress-strain relationship under different proportional parameters, different fiber contents and coarse aggregate contents, and different constraint conditions.

9. A system for establishing a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints, characterized in that, include: Yield setting section, determining the yield criterion; Considering the introduction of steel fibers and coarse aggregate, as well as the influence of constraints, a modified yield function for the CDP model is proposed: In the formula, , , , and These represent effective compressive cohesion and effective tensile cohesion, respectively. For Mises equivalent stress, For hydrostatic pressure, For the maximum effective principal stress, For plastic strain, subscript c Indicates being under pressure; Subscript t Indicates being pulled, σ r To constrain stress, K c It is a pressure invariant p The ratio of the second stress invariant on the tensile meridian to the second stress invariant on the compressive meridian at the initial yield surface; V f Fiber content, V ca This refers to the coarse aggregate content; The hardening and softening settings are defined, and the hardening and softening criteria are determined. Considering the UHPC constraint effect, aggregate content, fiber content, and residual stress, a stress-strain model for UHPC-modified CDP is proposed. In the formula, x = , y = , and These represent axial compressive strain and axial compressive stress, respectively. and These represent the axial compressive strain and axial compressive stress under constrained stress, respectively. n and A The slopes of the rising and falling segments are controlled separately; two parameters are used. λ 1 and λ 2. Describe the effects of constraints on the rising and falling segments respectively: In the formula, , , ; Based on the stress-strain model above, the hardening / softening function is obtained. , , The minimum principal stress under the current stress condition. q This represents the minimum deflection stress under the current stress conditions. The plastic flow setting section determines the plastic flow criteria; considering the influence of constraints, plastic history, and proportional parameters on plastic flow, an improved expansion angle parameter is adopted. : ， In the formula, , V f and V ca In parameters D The approach is to consider the incremental aspects: ; The damage evolution setting section determines the damage evolution law; the damage evolution in the modified CDP model is described by the following equation: ， In the formula, This represents the peak stress of the UHPC. This refers to the axial stress after the peak value. The relationship between damage and axial strain can be determined through stress-strain relationships; The model construction unit constructs a UHPC modified continuous damage plastic constitutive model under multiaxial constraints based on the yield setting unit, the hardening and softening setting unit, the plastic flow setting unit, and the damage evolution setting unit. The control unit is communicatively connected to the yield setting unit, the hardening and softening setting unit, the plastic flow setting unit, the damage evolution setting unit, and the model construction unit, and controls their operation.

10. The system for establishing a UHPC-corrected continuous damage plastic constitutive model under multiaxial constraints according to claim 9, characterized in that, Also includes: The input display unit is connected in communication with the control unit and is used to allow users to input operation commands and display the corresponding commands.

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