A method and system for correcting concrete elastoplastic model based on confining pressure and strength

Abstract

The present invention provides a method and system for correcting a concrete elastoplastic model based on confining pressure and strength, which relates to the field of concrete material design. Aiming at the problem that the current theoretical model has not been reliably corrected, resulting in limited application of the theoretical model, a correction model for the plastic volume deformation threshold considering the concrete strength and confining pressure, and a correction model for the softening section parameters considering the concrete strength are proposed by verifying and calculating the test results of uniaxial, biaxial and triaxial experiments, so as to improve the consistency between the test value and the theoretical value, ensure accuracy and theoretical reliability, and meet the needs of the application of the theoretical model.

Description

Technical Field

[0001] The invention relates to the field of concrete material design, and in particular to a concrete elastoplastic model correction method and system based on confining pressure and strength. Background Art

[0002] In bridge engineering, bridge piers are often reinforced by gluing steel plates or wrapping FRP. Regardless of the reinforcement method, it is essentially to improve the strength and ductility of concrete by constraining concrete to achieve the purpose of strengthening bridge piers. The strength of concrete under triaxial stress state can be obtained through experimental research and theoretical analysis.

[0003] At present, the constitutive model of concrete under confining pressure has been developed based on different strength criteria. However, the current research on the plastic constitutive model of concrete has relatively complex theoretical problems. Different theoretical models require a large number of parameters for calibration. There are also the following defects: In order to ensure that the theoretical strength and deformation characteristics of concrete can match the measured values, a large number of parameter correction calculations are required, but no complete and reliable correction scheme is given. The theoretical model obtained without a reliable correction scheme cannot guarantee its accuracy and theoretical reliability, which limits the application of the theoretical model and makes it difficult to meet the demand for the application of the theoretical model. Summary of the invention

[0004] The purpose of the present invention is to address the defects of the prior art and provide a method and system for correcting the concrete elastoplastic model based on confining pressure and strength. By verifying and calculating the test results of uniaxial, biaxial and triaxial experiments, a correction model for the plastic volume deformation threshold considering the concrete strength and confining pressure and a correction model for the softening section parameters considering the concrete strength are proposed, so as to improve the consistency between the experimental values ​​and the theoretical values, ensure accuracy and theoretical reliability, and meet the needs of theoretical model application.

[0005] The first object of the present invention is to provide a method for correcting a concrete elastic-plastic model based on confining pressure and strength, comprising:

[0006] Obtain the experimental data of concrete stress and strain under uniaxial, biaxial and triaxial states, and obtain the theoretical stress and strain curves of concrete under uniaxial, biaxial and triaxial states according to the concrete properties;

[0007] Under the uniaxial state, the theoretical values ​​of the stress-strain curves at different concrete strengths are compared with the experimental values ​​to obtain the modified plastic volume strain threshold model and softening section parameter model.

[0008] Based on the test values ​​and stress-strain theoretical curves under biaxial state, the modified plastic volume strain threshold model and softening section parameter model are verified.

[0009] Based on the test values ​​and stress-strain theoretical curves under triaxial state, the plastic volume strain threshold is corrected, and the plastic volume strain threshold model based on concrete confining pressure and strength and the softening section parameter model based on concrete strength are obtained.

[0010] Furthermore, based on existing tests, stress-strain test value data of concrete under uniaxial, biaxial and triaxial states are obtained respectively.

[0011] Furthermore, corrections are made under the uniaxial state to adjust the plastic volume strain threshold and softening section parameters so that the experimental values ​​are consistent with the theoretical values.

[0012] Furthermore, under the uniaxial state, a plastic volume strain threshold model based on concrete strength and a softening section parameter model based on concrete strength are obtained.

[0013] Furthermore, the stress-strain test value data and stress-strain theoretical curve of the proportional biaxial stress are obtained and brought into the model verification process under the biaxial state.

[0014] Furthermore, the modified plastic volumetric strain threshold model and softening section parameter model were used in combination with the proportional biaxial compression concrete stress-strain curve to calculate the theoretical values, which were compared with the experimental values ​​to verify the validity and accuracy of the model.

[0015] Furthermore, under the triaxial state, the modified plastic volume strain threshold model and softening section parameter model are used, and the theoretical values ​​are calculated in combination with the triaxial concrete stress-strain curves under the same strength and different confining pressures. The theoretical values ​​are compared with the experimental values, and the experimental values ​​and theoretical values ​​are made consistent through correction.

[0016] Furthermore, by adjusting the plastic volume strain threshold, the agreement between the experimental value and the theoretical value is promoted.

[0017] Furthermore, according to the yield function and plastic potential function, the theoretical stress-strain curves of concrete under uniaxial, proportional biaxial and triaxial compression states are obtained.

[0018] The second object of the present invention is to provide a concrete elastoplastic model correction system based on confining pressure and strength, comprising:

[0019] The data acquisition module is configured to: acquire the test value data of concrete stress and strain under uniaxial, biaxial and triaxial states, and acquire the theoretical curves of concrete stress and strain under uniaxial, biaxial and triaxial states according to the concrete characteristics;

[0020] The modeling module is configured to: compare the theoretical value of the stress-strain theoretical curve at different concrete strengths with the experimental value under the uniaxial state to obtain the modified plastic volume strain threshold model and softening section parameter model;

[0021] The verification module is configured to: verify the modified plastic volume strain threshold model and softening section parameter model based on the test value and stress-strain theoretical curve under the biaxial state;

[0022] The correction module is configured to correct the plastic volume strain threshold based on the test value and stress-strain theoretical curve under the triaxial state, and obtain the plastic volume strain threshold model based on the concrete confining pressure and strength and the softening section parameter model based on the concrete strength.

[0023] Compared with the prior art, the present invention has the following advantages and positive effects:

[0024] (1) In order to solve the problem that the theoretical model has not been reliably revised, which limits its application, a revised model for the plastic volume deformation threshold considering concrete strength and confining pressure, as well as a revised model for the softening section parameters considering concrete strength, are proposed by verifying the test results of uniaxial, biaxial and triaxial tests. This improves the consistency between the experimental values ​​and the theoretical values, ensures accuracy and theoretical reliability, and meets the application requirements of the theoretical model.

[0025] (2) The plastic volume strain threshold model based on concrete confining pressure and strength and the softening section parameter model based on concrete strength are modified to make the experimental values ​​consistent with the theoretical values. The proposed modified model can provide a theoretical reference for the subsequent strength and deformation calculation of confined concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0027] Figure 1 Schematic diagram of the Heuvel-Westergaard coordinate system in Example 1 or 2 of the present invention.

[0028] Figure 2 Schematic diagram of the yield function f in Example 1 or 2 of the present invention.

[0029] Figure 3 Schematic diagram of the potential function g in Example 1 or 2 of the present invention.

[0030] Figure 4 Schematic diagram of the hardening function k and the softening function c in Example 1 or 2 of the present invention.

[0031] Figure 5 This is a flowchart of the iterative stress adjustment algorithm in Embodiment 1 or 2 of the present invention.

[0032] Figure 6Schematic diagram of the comparison between the stress-strain curve test and theoretical prediction of uniaxial compression concrete in Example 1 or 2 of the present invention.

[0033] Figure 7 Schematic diagram of the plastic volume strain threshold and softening stage parameter correction scheme in Example 1 or 2 of the present invention.

[0034] Figure 8 Schematic diagram of the plastic volume strain threshold and softening section parameter correction function in Example 1 or 2 of the present invention.

[0035] Fig. 9 Schematic diagram of the plastic volume strain threshold and softening section parameter correction model based on concrete strength in Example 1 or 2 of the present invention.

[0036] Fig.10 Schematic diagram of comparison between the stress-strain curve test and theoretical value of biaxially loaded concrete in Example 1 or 2 of the present invention.

[0037] Fig.11 Schematic diagram of comparison between the stress-strain curve test and theoretical value of triaxial compression concrete in Example 1 or 2 of the present invention.

[0038] Fig.12 Schematic diagram of the plastic volume strain threshold and softening section parameter correction model based on concrete strength and confining pressure in Example 1 or 2 of the present invention.

[0039] Fig.13 Schematic diagram of comparison between stress-strain curve test and theoretical prediction of triaxial compression concrete in Example 1 or 2 of the present invention.

[0040] Fig.14 Schematic diagram of comparative verification of stress-strain curve test and theoretical prediction of triaxial compression concrete in Example 1 or 2 of the present invention. DETAILED DESCRIPTION

[0041] Example 1

[0042] In a typical embodiment of the present invention, Figure 1-Figure 14 As shown in the figure, a modification method of concrete elastic-plastic model based on confining pressure and strength is given.

[0043] The correction method of concrete elastoplastic model based on confining pressure and strength is used to correct the concrete constitutive model. By verifying and calculating the test results of uniaxial, biaxial and triaxial experiments, a correction model of the plastic volume deformation threshold considering concrete strength and confining pressure and a correction model of the softening section parameters considering concrete strength are proposed to improve the consistency between the experimental values ​​and the theoretical values, ensure accuracy and theoretical reliability, and meet the needs of theoretical model application.

[0044] The concrete elastoplastic model modification method based on confining pressure and strength includes the following steps:

[0045] Obtain the experimental data of concrete stress and strain under uniaxial, biaxial and triaxial states, and obtain the theoretical stress and strain curves of concrete under uniaxial, biaxial and triaxial states according to the concrete properties;

[0046] Under the uniaxial state, the theoretical values ​​of the stress-strain curves at different concrete strengths are compared with the experimental values ​​to obtain the modified plastic volume strain threshold model and softening section parameter model.

[0047] Based on the test values ​​and stress-strain theoretical curves under biaxial state, the modified plastic volume strain threshold model and softening section parameter model are verified.

[0048] Based on the test values ​​and stress-strain theoretical curves under triaxial state, the plastic volume strain threshold is corrected, and the plastic volume strain threshold model based on concrete confining pressure and strength and the softening section parameter model based on concrete strength are obtained.

[0049] In this embodiment, the above correction method is described in detail with reference to the accompanying drawings:

[0050] 1. Analysis preparation: The concrete elastic-plastic model involves the yield criterion, flow law and hardening-softening law, among which: the yield criterion is to determine the conditions for the stress state to enter the plastic state; the flow law is to determine the direction of the plastic deformation increment when the material is in the yield state; the hardening-softening law is to determine the change of the yield condition when the material reaches the yield condition.

[0051] 2. Based on existing literature, collect stress-strain test data of concrete under uniaxial, proportional biaxial and triaxial states.

[0052] 3. Such as Figure 1 As shown in the figure, in the principal stress space of the Haigh-Westergaard coordinate system, according to the yield function and the plastic potential function, a program is compiled based on the iterative stress adjustment algorithm to obtain the theoretical stress-strain curves of concrete under uniaxial, proportional biaxial and triaxial states.

[0053] 4. Compare the theoretical values ​​of stress-strain curves under uniaxial conditions of different concrete strengths with the experimental values, and adjust the threshold and t value, which promotes the degree of agreement between the test value and the theoretical value, thereby obtaining the threshold value for considering the concrete strength and t-value models.

[0054] 5. Use the threshold corrected in step 3 The theoretical values ​​of the proportional biaxial compression concrete stress-strain curve are obtained by using the threshold model and t-value model and compared with the experimental values ​​to prove the validity and accuracy of the threshold model and t-model obtained in step 3.

[0055] 6. Use the threshold modified in step 3 The theoretical value of the stress-strain curve of triaxial concrete under different confining pressures with the same concrete strength is obtained by using the t-value model, which is compared with the test value to adjust the threshold Improve the agreement between experimental and theoretical values, thus obtaining threshold values ​​that take into account concrete strength and confining pressure Model and t-value model considering concrete strength.

[0056] In this embodiment, the yield function f is Figure 2 , the potential function g is Figure 3 The hardening-softening function is shown in Figure 4 In the figure, k is the hardening function; c is the softening function; is the plastic volume strain threshold, expressed as Where f c is the compressive strength of concrete, E c is the elastic modulus of concrete, v is Poisson's ratio. t controls the slope of the softening section of the c function, and its value is t = 0.001f c / 15.

[0057] Specifically, in this embodiment, combined with Figure 1-Figure 14 A detailed explanation of the above steps:

[0058] exist Figure 1 In the principal stress space of the Haigh-Westergaard coordinate system, according to the yield function and plastic potential function, we use Figure 5 The iterative stress adjustment algorithm in was used to compile relevant programs to obtain the theoretical values ​​of concrete stress-strain curves under uniaxial, proportional biaxial and triaxial compression states.

[0059] The obtained stress-strain curves under uniaxial conditions of different concrete strengths are compared with the experimental values. Figure 6 .Depend on Figure 6 It can be seen that the final agreement is poor if the constitutive model is directly used for analysis. The current constitutive model cannot reflect the softening section of the concrete stress-strain curve.

[0060] Adjust the threshold The t value promotes the agreement between the experimental value and the theoretical value. The adjustment scheme is shown in Figure 7 .

[0061] according to Figure 7 The adjustment scheme of the plastic volume strain threshold is obtained by ε, and we also get the correction function C of t t ,See Figure 8 The model formula is as follows, see formula 1 and 2 (only considering the concrete strength). Formula 1 and formula 2 are used to obtain the theoretical value of the uniaxial compression concrete stress-strain curve, and compared with the test value, as shown in Fig. 9 , the match is good.

[0062]

[0063] t=0.017f c -0.856 (2)

[0064] Formula 1 and Formula 2 are used to obtain the theoretical value of the stress-strain curve of the equal-proportional biaxial compression concrete, and compared with the experimental value, as shown in Fig.10 As shown, the validity and accuracy of the threshold model of Formula 1 and the model of Formula 2 are demonstrated.

[0065] Formula 1 and Formula 2 are used to obtain the theoretical values ​​of the stress-strain curve of triaxial concrete under different confining pressures with the same concrete strength, which will be compared with the test values, such as Fig.11 As shown. Fig.11 It can be seen that Formula 1 and Formula 2 cannot simulate the influence of confining pressure on the stress-strain curve of concrete very well.

[0066] Adjust the threshold Improve the agreement between test and theoretical values, thus obtaining threshold values ​​that take into account concrete strength and confining pressure Models such as Fig.12 The model formula is as follows:

[0067]

[0068] In the formula, f r It is the lateral confining pressure.

[0069] Formula 3 and Formula 2 are used to obtain the theoretical values ​​of the stress-strain curve of triaxial concrete under different confining pressures with the same concrete strength, which will be compared with the test values, such as Fig.13 As shown. Figure 8 It can be seen that Formula 3 and Formula 2 can well simulate the influence of confining pressure on the stress-strain curve of concrete.

[0070] like Fig.14 As shown, Formula 3 and Formula 2 are used to verify the effectiveness and accuracy of the model.

[0071] The parameters represented by the symbols in the above content are shown in Table 1:

[0072] Table 1 Parameters

[0073]

[0074]

[0075] The plastic volume strain threshold model based on concrete confining pressure and strength and the softening section parameter model based on concrete strength are modified to make the experimental values ​​consistent with the theoretical values. The proposed modified model can provide a theoretical reference for the subsequent strength and deformation calculation of confined concrete.

[0076] Example 2

[0077] In another typical embodiment of the present invention, Figure 1-Figure 14 As shown, a concrete elastoplastic model correction system based on confining pressure and strength is given.

[0078] include:

[0079] The data acquisition module is configured to: acquire the test value data of concrete stress and strain under uniaxial, biaxial and triaxial states, and acquire the theoretical curves of concrete stress and strain under uniaxial, biaxial and triaxial states according to the concrete characteristics;

[0080] The modeling module is configured to: compare the theoretical value of the stress-strain theoretical curve at different concrete strengths with the experimental value under the uniaxial state to obtain the modified plastic volume strain threshold model and softening section parameter model;

[0081] The verification module is configured to: verify the modified plastic volume strain threshold model and softening section parameter model based on the test value and stress-strain theoretical curve under the biaxial state;

[0082] The correction module is configured to correct the plastic volume strain threshold based on the test value and stress-strain theoretical curve under the triaxial state, and obtain the plastic volume strain threshold model based on the concrete confining pressure and strength and the softening section parameter model based on the concrete strength.

[0083] It can be understood that the working method of the above-mentioned concrete elastic-plastic model correction system based on confining pressure and strength is the same as the concrete elastic-plastic model correction method based on confining pressure and strength provided in Example 1. Please refer to the detailed description in the above-mentioned Example 1, which will not be repeated here.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for correcting the concrete elastoplastic model based on confining pressure and strength, characterized in that: include; Obtain the experimental data of concrete stress and strain under uniaxial, biaxial and triaxial states, and obtain the theoretical stress and strain curves of concrete under uniaxial, biaxial and triaxial states according to the concrete properties; Under the uniaxial state, the theoretical values ​​of the stress-strain curves at different concrete strengths are compared with the experimental values ​​to obtain the modified plastic volume strain threshold model and softening section parameter model; the modified plastic volume strain threshold model is ; The modified softening section parameter model is t =0.017 f c -0.856; f c is the compressive strength of concrete, E c is the elastic modulus of concrete, v is Poisson’s ratio; Based on the test values ​​and stress-strain theoretical curves under biaxial state, the modified plastic volume strain threshold model and softening section parameter model are verified. Based on the test values ​​and stress-strain theoretical curves under triaxial state, the plastic volume strain threshold is modified to obtain the plastic volume strain threshold model based on concrete confining pressure and strength; among them, the plastic volume strain threshold model based on concrete confining pressure and strength is: , f r It is the lateral confining pressure.

2. The method for correcting the concrete elastic-plastic model based on confining pressure and strength according to claim 1, characterized in that: Based on the existing tests, the stress-strain test data of concrete under uniaxial, biaxial and triaxial states are obtained respectively.

3. The method for correcting the concrete elastoplastic model based on confining pressure and strength according to claim 1, characterized in that: Correction is performed under the uniaxial state, and the plastic volume strain threshold and softening section parameters are adjusted to make the experimental values ​​consistent with the theoretical values.

4. The method for correcting the concrete elastoplastic model based on confining pressure and strength according to claim 1, characterized in that: Obtain the proportional biaxial stress-strain test data and stress-strain theoretical curve, and bring them into the model verification process under the biaxial state.

5. The method for correcting the concrete elastoplastic model based on confining pressure and strength according to claim 4, characterized in that: The modified plastic volumetric strain threshold model and softening section parameter model were used to calculate the theoretical values ​​in combination with the proportional biaxial compression concrete stress-strain curve, and compared with the experimental values ​​to verify the effectiveness and accuracy of the model.

6. The method for correcting the concrete elastoplastic model based on confining pressure and strength according to claim 1, characterized in that: Under the triaxial state, the modified plastic volume strain threshold model and softening section parameter model are used, and the theoretical values ​​are calculated by combining the triaxial concrete stress-strain curves under the same strength and different confining pressures. The theoretical values ​​are compared with the experimental values, and the experimental values ​​and theoretical values ​​are made consistent through correction.

7. The method for correcting the concrete elastic-plastic model based on confining pressure and strength according to claim 6, characterized in that: By adjusting the plastic volume strain threshold, the agreement between the experimental value and the theoretical value is improved.

8. The method for correcting the concrete elastoplastic model based on confining pressure and strength according to claim 1, characterized in that: According to the yield function and plastic potential function, the theoretical stress-strain curves of concrete under uniaxial, proportional biaxial and triaxial compression states are obtained.

9. A concrete elastoplastic model correction system based on confining pressure and strength, characterized in that: include: The data acquisition module is configured to: acquire the test value data of concrete stress and strain under uniaxial, biaxial and triaxial states, and acquire the theoretical stress and strain curves of concrete under uniaxial, biaxial and triaxial states according to the concrete characteristics; The modeling module is configured as follows: under the uniaxial state, the theoretical value of the stress-strain theoretical curve at different concrete strengths is compared with the experimental value to obtain the modified plastic volume strain threshold model and softening section parameter model; wherein the modified plastic volume strain threshold model is ; The modified softening section parameter model is t =0.017 f c -0.856; f c is the compressive strength of concrete, E c is the elastic modulus of concrete, v is Poisson’s ratio; The verification module is configured to: verify the modified plastic volume strain threshold model and softening section parameter model based on the test value and stress-strain theoretical curve under the biaxial state; The correction module is configured to: based on the test value and stress-strain theoretical curve under the triaxial state, correct the plastic volume strain threshold value to obtain the plastic volume strain threshold model based on the concrete confining pressure and strength; wherein the plastic volume strain threshold model based on the concrete confining pressure and strength is , f r It is the lateral confining pressure.

Images