CN115221581B - A Determination Method of Shear Wall Damage Parameters Based on Different Bearing Capacity Indexes - Google Patents

Abstract

The invention discloses a shear wall damage parameter determination method based on different bearing capacity indexes, wherein the states of a material design value and a limit value are both equivalent to the damage state of a standard value model based on energy equivalence by finite element analysis of an integral shear wall, and the method comprises the following steps: establishing a finite element model adopting a material design value or a limit value to correspond to a component performance state, analyzing to obtain a wall bearing capacity-displacement curve, and taking the area enclosed by the force-displacement curve as an energy value of the state; and determining displacement values in a bearing capacity-displacement curve based on a standard value model according to an energy equivalent principle, so as to determine the damage state and damage parameters of the wall. According to the shear wall damage parameter determination method based on different bearing capacity indexes, as the shear wall damage model and parameter calculation are adopted in the general finite element software, the damage state can be rapidly and reasonably determined through processing in an energy equivalent mode, and the calculation and the prediction are more accurate.

Description

A Determination Method of Shear Wall Damage Parameters Based on Different Bearing Capacity Indexes

technical field

The invention relates to a method for realizing component performance state discrimination based on concrete damage parameters, in particular to a method for determining damage parameters of a shear wall based on different bearing capacity indexes.

Background technique

In the prior art, damage states to concrete shear walls are generally divided into five types, including: slight damage, mild damage, moderate damage, not serious damage, and relatively serious damage. Although there are various specifications for the judging criteria of these five states, for example, the content of "references for bearing capacity of components with different bearing capacity corresponding to different performance requirements" in "Code for Seismic Design of Buildings" (GB 50011-2010) is used to determine Component performance judgment. However, the way to confirm the five states in the prior art is generally through destructive tests, or through the analysis of artificial parameter settings, which is often inaccurate, and there are certain errors when evaluating the performance state of structural members under stress. wrong result.

Concrete has been an important building material for more than a hundred years. Considering the complexity of the material composition of concrete itself, although the research on the mechanical properties of concrete (including constitutive models) in the field of structural engineering has been extensively developed, the damage and The basic issues of crack propagation and damage and fracture mechanism in the fracture process still need to be further explored.

The finite element methods for simulating the nonlinear analysis of reinforced concrete shear walls include solid analysis method and shell element analysis method. The solid analysis method of the shear wall is to establish the three-dimensional geometric models of concrete and steel bars in general finite element software, and carry out loading solutions based on their respective material constitutive relations. In the solid model, the deformation of concrete and steel bars is coordinated through a reasonable boundary coupling relationship. The common boundary coupling relationships are: ① Common nodes, the solution cost is the least, but the grid division requirements are relatively high; ② Embed steel bars or section steel in concrete entities. When the spatial position meets the embedded geometric relationship during modeling, the coupling relationship between different materials can be realized; ③ spring units are set between different materials, and the spring properties are defined according to the bond constitutive between materials. The first two methods ignore the bond-slip between different materials. In short, the solid analysis method needs to consider the connection relationship of different materials, which has a high requirement for the fineness of the geometric division of the model. The calculation cost of this method for the overall structure is very high, and the convergence of the calculation is difficult to guarantee, so the solid method is basically only applicable to the analysis at the component level.

Therefore, using the two-dimensional shell element model to analyze the overall structure of reinforced concrete shear walls not only has relatively good accuracy and practicability, but also can take into account the calculation efficiency, and has been widely recognized and developed in the engineering and academic research circles. Among them, the two-dimensional concrete constitutive of the layered shell adopts the concrete damage model, which can intuitively and animatedly reflect the damage change history of the shear wall members under the load or earthquake. The damage parameter only indicates the degree of stiffness degradation of the component, and the damage parameter is between [0,1]. When the damage is 0, it means that the wall pier is intact, and when the damage is 1, it means that the wall pier is completely destroyed. For the aforementioned five failure states of the shear wall, the damage parameters corresponding to each state change in (0,1). Although "Code for Seismic Design of Buildings" (GB 50011-2010) has a clear criterion for judging the bearing capacity, there is still a lack of damage parameter ranges that can be directly used to guide the evaluation of the performance state of concrete.

In the study of concrete damage models, a large number of scholars have proposed various damage constitutive models for specific engineering situations, but due to the particularity of the applicable conditions and the complexity of the established constitutive models, few of them can express simple, The general damage constitutive relationship that is easy for engineers to accept, and the damage parameter standard with clear physical meaning to evaluate the mechanical performance state of concrete is even more lacking. In short, the prior art has not had a good solution to the damage model parameters of concrete, and there are problems in the prior art that need to be solved.

Contents of the invention

The purpose of the present invention is to provide a shear wall damage parameter determination method based on different bearing capacity indexes, and provide a concrete damage model parameter determination method that is realistic and predictable, relatively accurate and in line with the actual situation.

Technical scheme of the present invention is as follows:

A method for determining damage parameters of shear walls based on different bearing capacity indexes, in which, through the analysis of general finite element software for integral shear walls, the state of material design values and limit values are equivalent to standard value models based on energy equivalence damage status and includes the following steps:

A. Establish a finite element model that uses the material design value or limit value to correspond to the performance state of the component, analyze and obtain the wall bearing capacity-displacement curve, and use the area enclosed by force-displacement as the energy value of the state;

B. According to the principle of energy equivalence, determine the displacement value in the bearing capacity-displacement curve based on the standard value model, so as to determine the damage state and damage parameters of the wall pier.

The method for determining the damage parameters of the shear wall based on different bearing capacity indexes, wherein, before the step A, there are steps:

A0. Establish the component model of the shear wall in the finite element processing software and perform parameter calculation.

In the method for determining damage parameters of a shear wall based on different bearing capacity indexes, one or more of Paco, Sausage, and Abaqus are used as the general-purpose finite element software.

The method for determining damage parameters of a shear wall based on different bearing capacity indexes, wherein, in the step B, the corresponding damage value of the slight damage in the damage state is (0,0.3], and the corresponding damage value of the slight damage is (0.3～ 0.5], the corresponding damage value of moderate damage is (0.5～0.7], the corresponding damage value of non-serious damage is (0.7～0.9] and the corresponding damaged wall accounts for 30% of the total section, and the corresponding damage value of more serious damage is (0.9, 1).

The method for determining damage parameters of a shear wall based on different bearing capacity indexes, wherein, for the material ultimate strength value in the step A, the concrete strength is 0.88 times the cubic strength, and the steel bar strength is 1.25 times the yield strength.

The method for determining damage parameters of a shear wall based on different bearing capacity indexes, wherein, the damage calculation steps of the design value model, limit value model and standard value model in the steps A and B are as follows: first apply the vertical load After that, the vertical load remains unchanged, and then the horizontal load is applied to determine the bearing capacity-displacement curve and damage distribution of the wall.

A method for determining shear wall damage parameters based on different bearing capacity indexes provided by the present invention can be processed in an energy equivalent manner due to the use of finite element processing software for shear wall damage models and parameter calculations. Quickly and reasonably determine the damage state, and the calculation prediction is more accurate.

Description of drawings

Fig. 1 is a schematic diagram of the processing flow of a preferred embodiment of the method for determining the damage parameters of a shear wall based on different bearing capacity indexes according to the present invention.

Fig. 2 is the schematic diagram of establishing the shear wall finite element model in the preferred embodiment of the method of the present invention, wherein (a) is the wall finite element model, (b) is the axial force applied on the top of the wall, (c) is the time history of horizontal displacement applied at the top of the wall.

Fig. 3 is a schematic diagram showing the calculation results of the last moment distribution of shear wall compression damage according to the method of the present invention.

Fig. 4 is a schematic diagram of base shear force and horizontal displacement curves corresponding to different material strength grades of the shear wall according to the method of the present invention.

Fig. 5 is a schematic diagram of unloading and reloading path curves of concrete materials in a preferred embodiment of the method of the present invention.

Fig. 6 is a schematic diagram of the stress-strain-damage corresponding curve of C60 concrete in a preferred embodiment of the method of the present invention.

Fig. 7 is a schematic diagram of finite element analysis of damage distribution of concrete materials corresponding to different states of components in a preferred embodiment of the method of the present invention.

Detailed ways

Preferred embodiments of the present invention are described in detail below.

In a preferred embodiment of a shear wall damage parameter determination method based on different bearing capacity indexes provided by the present invention, it is applied in common general-purpose finite element analysis software, such as one or more of Paco, Sausage, Abaqus, etc. One, setting the damage parameter determination process for the shear wall. When performing the overall finite element analysis of the shear wall, most of the walls of the shear wall are uniformly and directly adopt standard value materials, so when corresponding to the damage state, they are all based on the model of the standard strength of the material. In the preferred embodiment of the method of the present invention, the equivalent of the material design value and the state of the limit value model as the damage state of the standard value model is based on the assumption of energy equivalence, and the specific processing steps of the corresponding method are as follows: the first step, Establish a finite element model that uses the material design value or limit value to correspond to the performance state of the component, analyze and obtain the wall bearing capacity-displacement curve, and use the area enclosed by the force-displacement as the energy value of the state; in the second step, according to the energy equivalent According to the principle, the displacement value in the bearing capacity-displacement curve based on the standard value model is determined, so as to determine the damage state and damage parameters of the wall pier. At this time, it is considered that the damage state in the standard value model is the bearing capacity range that characterizes the component state.

The method for determining the damage parameters of the shear wall based on different bearing capacity indicators in the present invention is to establish the concrete damage parameters of the shear wall and the bearing capacity of the wall pier by analyzing the finite element model and following the existing criteria for determining the performance of the bearing capacity evaluation members. Correspondence, such as through the bearing capacity-displacement enclosed area of the material standard value strength and limit value strength curve, based on the principle of energy equivalence, the conversion of damage states corresponding to different material strength levels is realized. Correspondingly, the stress state of the limit value can be replaced by the stress state of the standard value or design value, and the law of damage parameters under different performance states can be obtained, and then equivalently realize the judgment of the performance state of the shear wall by the criterion of the bearing capacity. The concept clearer and more precise.

In the preferred embodiment of the shear wall damage parameter determination method based on different bearing capacity indexes of the present invention, as shown in Figure 1, the basic processing steps include: firstly, establish the model of the component in the finite element processing software and perform parameter calculation ;Secondly, output the bearing capacity-displacement curve of the component according to the process of finite element analysis; Thirdly, determine the different states of slight damage, mild damage, moderate damage, not serious damage, severe damage, etc. according to the judgment criteria of component performance; Fourth, through the principle of energy equivalence, the damage parameters of each performance state based on the material model can be obtained, and the above damage states can be corresponding to five different damage ranges 1-5, for example but not limited to, the damage parameters (0,0.3 ] is damage 1, damage parameter (0.3～0.5] is damage 2, damage parameter (0.5～0.7] is damage 3, damage parameter (0.7～0.9] is damage 4, damage parameter >=0.9 is damage 5, and according to the component The performance judgment criteria correspond to slight damage, mild damage, moderate damage, not serious damage and relatively serious damage.

In the shear wall damage parameter processing example of the specific embodiment of the present invention, the length of the shear wall is 4m, the height is 5.4m, the wall thickness is 0.4m, and the vertical and horizontal reinforcement ratio of the wall is 0.3%. The concrete material is C60, and the steel bar material is HRB400. The finite element model is established by software, as shown in Figure 2(a)-(c), and the axial force exerted on the top of the wall shown in Figure 2(b), controls the wall to maintain an axial compression ratio of 0.5. According to the calculation, a total of 0.5*27.5E6*4*0.4=22e3 kN is applied on the top of the wall, where 27.5E6 is the concrete C60 strength design value in N/m ² , 4m is the wall length, and 0.4m is the wall thickness. Figure 2(c) shows the horizontal displacement applied on the top of the wall when the axial compression ratio of the wall is kept constant at 0.5.

According to the content in Appendix M of "Code for Seismic Design of Buildings" (GB 50011-2010), the "bearing capacity reference of components with different bearing capacity corresponding to different performance requirements", determine the performance judgment criteria of components. Table 1 is the reference index list of bearing capacity for structural components to achieve seismic performance requirements provided by the appendix of the seismic code. From Table 1, it can be seen that several states of components can be intuitively judged: intact, basically intact, slightly damaged, slightly damaged, and moderately damaged. These six levels are damaged and not severely damaged.

Table 1 Example of bearing capacity reference index for structural components to achieve seismic performance requirements

According to these contents, the relationship between different performance objectives, damage degree and bearing capacity of components can be established, as shown in Table 2. The "material design strength value" and "standard strength value" in Table 2 correspond to the specified ranges in the concrete specification; for the ultimate strength value, the concrete strength is 0.88 times the cubic strength, and the steel bar strength is 1.25 times the yield strength.

Table 2 Corresponding relationship between structural component status, damage degree and component bearing capacity

In a preferred embodiment of the method of the present invention, the skeleton curve of its concrete material model is taken from the concrete uniaxial tension-compression constitutive relationship of appendix C of "Code for Design of Concrete Structures" (GB50010-2010), and the peak value of concrete compression is introduced. Stress f _c and the increase factor K of its corresponding strain ε _c modify the uniaxial compression skeleton curve of concrete and consider the restraint of stirrups. The modified compression skeleton curve is described as formula (1).

α_a＝2.4-0.0125f_c；α_d＝0.157f_c ^0.785-0.905；In the formula

α _a =2.4-0.0125f _c ; α _d =0.157f _c ^0.785-0.905 ;

For ordinary concrete section, K=1+ρ _v f _yh /f _c , where ρ _v is volume hoop ratio, f _yh is stirrup yield strength, f _c is peak stress of concrete compression skeleton curve; for steel tube concrete Section, K=1+(A _a /A _cc )(1.8f _a /f _c -E _a /E _c ), where f _a , E _a , and A _a are the yield strength, elastic modulus and cross-sectional area of the steel , E _c , A _cc are the elastic modulus and cross-sectional area of the concrete inside the steel.

Under repeated loads, the unloading and reloading path of concrete under tension or compression is a diameter, as shown in Figure 5, where Er represents the elastic modulus of the unloading curve at point F, and E0 is the initial elastic modulus of concrete. The relationship between the two satisfies Formula (2).

For the relationship between concrete damage and skeleton curve, refer to the help of general finite element software (such as ABAQUS, Paco or Sausage, etc.). The relationship between concrete strain and stress is shown in formula (3). The stress in the formula can be expressed as a function of strain, so formula (3) can consider that the damage dc is also a function of strain.

Draw the stress-strain skeleton curve and strain-damage curve of concrete together, taking C60 as an example, as shown in Figure 6.

The reinforcement adopts the Menegotto-Pinto model (MP for short), and the basic formula is:

σ ^* ＝(σ-σ _r )/(σ ₀ -σ _r ) (5)

ε ^* ＝(ε-ε _r )/(ε ₀ -ε _r ) (6)

b=E _h /E _s (7)

R＝R ₀ -a ₁ ξ/(a ₂ +ξ) (8)

ξ＝|(ε _m -ε ₀ )/ε _y | (9)

In the formula: (ε _r , σ _r ) is the strain turning point; (ε ₀ , σ ₀ ) is the intersection of the elastic asymptote and the yield asymptote; E _h is the hardening modulus; E _s is the elastic modulus; ε _m is the maximum or minimum value of the strain in the loading history (depending on the increase or decrease of the current strain); ε _y is the yield strain of the steel bar; R ₀ , a ₁ , and a ₂ are determined by experiments, and the default values are 18.5, 0.925 and 0.15.

In the implementation method embodiment of the present invention, the material of the calculation model adopts the design value, standard value and limit value respectively, and the design value, standard value and limit value of the corresponding material are determined by taking the energy of the design value, standard value and limit value to be consistent damage status. In actual processing, the calculation time of the model of the present invention is 10s, 0-5s is used as the application process of the vertical load, after that the vertical load remains unchanged, and the horizontal displacement starts to be applied in 5-10s.

According to the above calculation process, in the preferred embodiment of the method for judging the performance state of the concrete damage parameters of the shear wall according to the present invention, the compression damage distribution of the wall can be calculated according to the design value, standard value and limit value of the material , to obtain the damage state distribution of the wall at different moments. As shown in Figure 3, it is an example of the output of the shear wall damage distribution diagram at the last moment in the finite element analysis software.

Figure 4 shows the wall base shear force and horizontal displacement curves corresponding to the material standard value strength and limit value strength. According to the judgment method of force-displacement enclosed area representing the energy value corresponding to the proposed performance state, the same energy value is used to determine the Determine the corresponding damage state in the standard value model, and the damage state represents the proposed mechanical performance state of the shear wall.

In the overall finite element analysis, most of the wall is based on the standard value material, so the corresponding damage state is based on the model of the standard strength of the material. Equivalenting the state of the material design value and limit value model to the damage state of the standard value model is based on the assumption of energy equivalence. The specific corresponding method is as follows: the first step is to establish a finite The element model is used to analyze the bearing capacity-displacement curve of the wall, and the area enclosed by the force-displacement is used as the energy value of the state; the second step is to determine the load-bearing capacity-displacement curve based on the standard value model based on the principle of energy equivalence. The displacement value of the wall pier can be determined to determine the damage state and damage parameters of the wall pier. At this time, it is considered that the damage state in the standard value model represents the proposed mechanical performance state of the shear wall.

According to the aforementioned method, each state in Figure 7 is determined, which are (a) slightly damaged, (b) slightly damaged, (c) moderately damaged, and (d) not seriously damaged, and the corresponding damage values are about are (0, 0.3], (0.3, 0.50], (0.5, 0.7] and (0.7, 0.90], where the wall corresponding to no serious damage accounts for about 30% of the total section.

In the preferred embodiment of the method for determining shear wall damage parameters based on different bearing capacity indicators in the present invention, since the calculation of the shear wall damage model and parameters in the finite element processing software is adopted, the energy equivalent method is used to process , the damage state can be quickly and reasonably determined, and the calculation prediction is more accurate.

It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should belong to the protection scope of the appended claims of the present invention.

Claims (5)

1. The shear wall damage parameter determining method based on different bearing capacity indexes is characterized by comprising the following steps of:

A. establishing a finite element model adopting a material design value and a limiting value to correspond to the performance state of a component, analyzing to obtain a bearing capacity-displacement curve of the wall, and taking the area enclosed by the bearing capacity-displacement in the bearing capacity-displacement curve as the energy value of the damage state of a standard value model;

B. according to the energy equivalent principle, determining a displacement value in a bearing capacity-displacement curve based on a standard value model, so as to determine the damage state and damage parameters of the wall limb;

determining a performance judgment criterion of the component according to bearing capacity references of components with different bearing capacities and corresponding to different performance requirements, and determining the damage state of the component according to the component performance judgment criterion, wherein the damage state comprises slight damage, moderate damage, no serious damage and serious damage;

in the step B, the slight damage corresponding damage value of the damaged state is (0, 0.3), the slight damage corresponding damage value is (0.3, 0.5), the moderate damage corresponding damage value is (0.5,0.7), the no serious damage corresponding damage value is (0.7,0.9) and the corresponding damaged wall accounts for 30% of the whole section, and the more serious damage corresponding damage value is (0.9,1).

2. The method for determining shear wall damage parameters based on different bearing capacity indexes according to claim 1, wherein the step a is further preceded by the steps of:

a0, building a component model of the shear wall in finite element processing software and calculating parameters.

3. The method for determining shear wall damage parameters based on different bearing capacity indicators according to claim 2, wherein the general purpose finite element software adopts one or more of Paco, sausage, abaqus.

4. The method for determining the damage parameters of the shear wall based on different bearing capacity indexes according to claim 3, wherein the ultimate strength value of the material in the step A is 0.88 times of the cubic strength of the concrete, and the strength of the steel bar is 1.25 times of the yield strength.

5. The method for determining shear wall damage parameters based on different bearing capacity indexes according to claim 4, wherein the design value model, the limit value model and the standard value model damage calculation step in step A, B are as follows: firstly, carrying out a vertical load application process, then keeping the vertical load unchanged, and then carrying out a horizontal load application process, so as to determine the bearing capacity-displacement curve and damage distribution of the wall body.

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