Damage Constitutive Model For Concrete Research Articles

Mechanical properties and damage constitutive model of concrete containing waste glass and rice husk ash in high-temperature environments

The application of waste glass and rice husk ash in concrete promotes sustainable development by reducing resource consumption and environmental pollution. This study evaluates the high-temperature performance of concrete containing glass sand, glass powder, and rice husk ash. Results show that waste glass increases mass loss, while rice husk ash reduces it and enhances concrete compactness. At ambient temperature, compressive strength is lower in rice husk ash samples compared to waste glass concrete, but higher at elevated temperatures. Particle size differences between glass sand and glass powder mainly influence high-temperature performance. Waste glass does not significantly mitigate cyclic loading damage, whereas rice husk ash reduces damage in glass sand concrete but not in glass powder concrete. A uniaxial compression thermo-mechanical coupling damage model and an improved Broutman-Hull cyclic compression damage model are established, providing a basis for the design and safety evaluation of concrete structures in high-temperature environments.

A Static Damage Constitutive Model of Concrete Based on Microscopic Damage Mechanism.

In this article, a microscopic constitutive model is established that includes friction, plastic, and spring elements and has clear physical meaning. The friction unit reflects the mutual friction between crack surfaces, the plastic unit reflects the development of concrete plasticity, and the fracture of the spring unit reflects the formation and expansion of interior cracks in concrete. In addition, the integration of the random field theory into this model uncovers the physical underpinnings of the relationship between concrete's nonlinearity and randomness. The multi-scale modeling of the concrete static damage constitutive model is then realized once the parameters of the random field are discovered using the macro test results. In order to apply the model's applicability in finite element programs, a subroutine was ultimately constructed. The experimental data and the anticipated values from the numerical simulation are in good agreement, supporting the model's realism.

The Study on the Constitutive Model of Concrete for Explicit Dynamic of ABAQUS Based on Damage Energy

In this paper, the elastoplastic damage constitutive model of concrete is established based on the damage energy release rate to analyze the failure of concrete structures. Based on the user-defined material program VUMAT interface provided by the ABAQUS, the explicit algorithm is used to secondary develop the concrete model. The model is verified from mechanical behavior, mesh-dependence, and stress state under reciprocating loading. The results show that the model can reasonably simulate the mechanical state of concrete under compression and tension and can effectively solve the mesh-dependence problem in finite element problems. The simulation results were still consistent when the mesh size was 2.5 mm. The low cycle reciprocating simulation test of the concrete column also proves that the model has better hysteretic and bidirectional coupling performance. It is verified that the VUMAT material subroutine can meet the analysis requirements of reinforced concrete structures and can be used to simulate the dynamic response of structures with strong nonlinear stages.

Research on Dynamic Response Characteristics for Basement Structure of Heavy Haul Railway Tunnel with Defects

Based on the basic principle of thermodynamics, an elastoplastic damage constitutive model of concrete is constructed in this paper. The model is realized and verified in FLAC3D, which provides a solid foundation for the study of dynamic response and fatigue damage to the base structure of a heavy haul railway tunnel. The dynamic response and damage distribution of the base structure of a heavy-duty railway tunnel with defects were numerically simulated by the concrete elastic-plastic damage constitutive model. Then, by analyzing the response characteristics of the tunnel basement structure under different surrounding rock softening degrees, different foundation suspension range and different foundation structure damage degree are determined. The results show the following: (1) The elastoplastic damage constitutive model of concrete can well describe the stress–strain relationship of materials, especially with the simulation results of post peak softening being in good agreement with the test results, and the simulation effect of the unloading–reloading process of the cyclic loading and unloading test also meet the requirements. (2) The initial stress field and dynamic response of the tunnel basement structure under the action of train vibration load are very different from the ideal state of the structure design when the surrounding rock of the base is softened, the base is suspended, or the basement structure is damaged. With the surrounding rock softening, basement hanging, or basement structure damage developing to a certain extent, the basement structure will be damaged. (3) The horizontal dynamic stress amplitude increases with the increase in the softening degree of the basement surrounding rock. The horizontal dynamic stress of the measuring point increases with the increase in the width of the hanging out area when the hanging out area is located directly below the loading line. When the degree of damage to the basement structure is aggravated, the horizontal dynamic tensile stress of each measuring point gradually decreases. (4) The maximum principal stress increment increases with the increase in the fracture degree of the basement structure, while the minimum principal stress increment decreases with the increase in the fracture degree of the basement structure, but the variation range of the large and minimum principal stress increments is small. The research results have important theoretical and practical significance for further analysis of the damage mechanism and control technology of the foundation structure of a heavy haul railway tunnel with defects.

Study on damage rules on concrete under corrosion of freeze-thaw and saline solution

Coastal concrete in cold area is subjected to chemical attacks and freeze-thaw cycles, which both considerably decrease the service life of concrete structures. In this research, we mainly analyzed and assessed the durability of concrete under the coupling action of chlorine ion, sulfate ion and freeze-thaw cycles by designing the orthogonal experiment. In the process of conducting the experiment, the relative dynamic elastic modulus, the mass loss rate, the thickness of damage layer, the velocity of ultrasonic wave and other damage indexes which reflect the damage law of concrete under the coupling action were measured or calculated and the range analysis and variance analysis were used to study the influence degree of different factors. Then the damage evolution equation and the damage constitutive model of concrete were established on the basis of the analysis for damage indexes and the results of mechanical tests. The comparison results showed that the theoretical values well agreed with the experimental ones and the damage model acquired can potentially be used to predict the damage degree of concrete under the coupling effect of chlorine ion, sulfate ion and freeze-thaw cycles.

Experimental and numerical studies of T-shaped reinforced concrete members subjected to combined compression-bending-shear-torsion

The study of reinforced concrete members subjected to combined loads always has been an important research topic in the field of engineering, but the torsional behavior of T-shaped reinforced concrete members subjected to combined loads has yet to be determined. This paper is focused on providing a detailed explanation of the torsional behavior of T-shaped reinforced concrete members subjected to combined compression-bending-shear-torsion. From the perspective of experimental tests and numerical analyses, in this paper, we discuss the effects of combined loads on the torsion bearing capacity, the development of cracks and the failure mode, strains of key points in the concrete and longitudinal reinforcement, and the relation of torsion and angular displacement. We conducted experiments and numerical analyses of four groups of reinforced concrete members by using the main variables of the axial pressure ratio and the bending moment. Also, the experimental and calculated results are compared based on the elastic-plastic damage constitutive model of concrete. Based on the test data and the existing formula, we also extended the formula used to calculate the torsion bearing capacity and provided diagrams of the interaction when combined loads were applied. In addition, the results of this study highlight the turning point from torsion failure to compression-bending-torsion failure. The test results demonstrated that torsion capability increases in the specified range of axial pressure ratio and decreases as bending increases. The test results also indicate the importance of considering the effects of compression-shear-bending on the torsion bearing capacity in the engineering design.

Damage mechanism modelling of shield tunnel with longitudinal differential deformation based on elastoplastic damage model

Shield tunnels with great longitudinal differential deformations will adversely affect the service performance and optional safety of the metro system. Previous studies on the longitudinal mechanical behavior of shield tunnel are mostly carried out within the framework of elastic or elastic–plastic theory. However, assuming the concrete as elastoplastic body cannot properly reflect its nonlinear mechanical characteristics such as strain softening, stiffness degradation, etc., while damage or crack inevitably occurs when shield tunnel suffers large deformations. Therefore, the nonlinear damage characteristics of concrete material are considered in this paper, a novel positive/negative decomposition of stress tensor in energy norm is introduced herein to consider the asymmetric tensile/compressive material behavior of concrete, and a bi–scalar damage constitutive model of concrete is developed in turn. Then, to investigate the damage and degradation mechanisms of shield tunnel with differential deformation, the 3D discontinuous contact model is employed to develop the elaborate tunnel–soil numerical model. Results show that when shield tunnel suffers differential deformation, tensile damage dominates while compressive damage is minor, additional shear force and bending moment are induced, the ovality of tunnel cross section and serviceability also vary along the longitudinal direction. The damage and degradation of concrete material will reduce the tunnel integral stiffness and attenuate its ability to resist longitudinal and circumferential deformation. Besides, the segmental rebar is hard to yield, while the longitudinal coupling bolts on the lower half of tunnel segments with large deformation are inclined to yield. It should be noted that, the segmental rings near the inflection point of longitudinal deformation profile are most severely damaged, and exhibit the largest convergence deformation and lowest serviceability, where special attentions should be paid.

Copula-Based Quantification of Probabilistic Dependence Configurations of Material Parameters in Damage Constitutive Modeling of Concrete

The constitutive model of concrete is the key basis for nonlinear analysis of concrete structures under disastrous dynamic actions, e.g., earthquakes. The material parameters of the constitutive model of concrete are essentially probabilistically dependent. However, in practice, it is mostly assumed that these parameters are either independent or perfectly dependent. In the present paper, the quantification of probabilistic dependence configurations between random material parameters and their effects on stochastic structural responses are investigated. Based on the ample amount of data from tested complete curves of compressive stress-strain relationships of concrete with different strength grades, the parameters in the damage constitutive model of concrete are samplewise identified. Further, the probabilistic dependence configurations are studied based on copula theory, which is also considered as a data-mining tool. The complete constitutive curves of concrete are generated according to the obtained dependence configurations and marginal distributions. Then, combined with the probability density evolution method, the stochastic response analysis of concrete structures is carried out. The analysis results show that the dependence among the strength, peak strain, and the parameter of the descendent segment cannot be ignored. Due to the constraint of dependence configurations, the distribution characteristics of the generated point set are substantially consistent with the tested results, and the generated complete stress-strain curves agree well with the tested curves at both the level of sample and the level of second-order moments. In addition, no abnormal complete stress-strain curves, e.g., those with low strength and sharp descendent segment, which are unlikely to occur in the test, are generated. The dependence configuration of the parameters of concrete has considerable effects on the response and reliability of concrete structures, and may even lead to the change of overall structural failure mode. Consequently, ignoring the probabilistic dependence of material parameters may yield misleading results for decision making. Problems to be further studied are also discussed.

A variable parameters damage model for concrete

A novel four-parameters damage constitutive model for concrete in strain space is proposed in this paper. It is based on the Heish-Ting-Chen constitutive model and is derived in the framework of the thermodynamics of irreversible process. Because tension damage is a major fracture mode in concrete used for hydraulic structures, an equivalent strain is introduced that converts the multi-axial strain state into the equivalent tension strain to determine the tension damage. Considering the change in the equations' parameters during progressive failure, a variable parameters constitutive model is established. The parameters of the damage constitutive model are obtained by the increasing section and the decreasing section of stress-strain curve and it is demonstrated that the proposed model performs better than the regular constitutive model in the decreasing section. The numerical implementations provide a good description of the failure process as well as an accurate prediction of the behaviour of concrete.

Collapse Simulation and Response Assessment of a Large Cooling Tower Subjected to Strong Earthquake Ground Motions

Large cooling towers in thermal power plants and nuclear power plants are likely to suffer from strong earthquakes during service periods. The resulting destructions of the cooling towers would endanger the power plants and threaten the security of the related areas. It is important to use effective means to evaluate the safety status of the cooling towers and guide further precautions as well as retrofitting efforts. This paper is therefore focused on an elaborate numerical investigation to the earthquake-induced collapses of a large cooling tower structure. A complete numerical work for simulation of material failure, component fracture, structural buckling and system collapse is presented by integrating the stochastic damage constitutive model of concrete, refined structural element models, and some other key techniques. Numerical results indicate that the damage behavior and collapse mode of the cooling tower are affected notably by the randomness specification of ground motions. The collapse mechanisms of the cooling tower are studied from the energy absorption and dissipation points of view. An effective energy-based criterion is introduced to identify the collapse of the cooling tower under ground motion excitations. While distinct collapse modes are observed, the collapse criterion can predict well the damage and failure of the cooling tower. The proposed methodology is vital to better understanding the disastrous mechanisms and potential failure paths in optimal design of the cooling towers to ensure safety.

A physically motivated model for fatigue damage of concrete

The fatigue problem of concrete is still a challenging topic in the researches and applications of concrete engineering. This paper aims to develop a fatigue damage evolution law based model for concrete motivated by the analysis of physical mechanism. In this model, the fatigue energy dissipation process at microscale is investigated with rate process theory. The concept of self-similarity is employed to bridge the scale gap between microscale cracking and mesoscale dissipative element. With the stochastic fracture model, the crack avalanches and macro-crack nucleation processes from mesoscale to macroscale are simulated to obtain the behaviors of macroscope damage evolution of concrete. In conjunction with continuum damage mechanics framework, the fatigue damage constitutive model for concrete is then proposed. Numerical simulations are carried out to verify the model, revealing that the proposed model accommodates well with physical mechanism of fatigue damage evolution of concrete whereby the fatigue life of concrete structures under different stress ranges can be predicted.

Development for twin shear damage constitutive model of concrete

The concrete material constitutive model has limitations at present stage. Mazars concrete damage equation obtained by uniaxial test was extended to the triaxial state based on Yu Maohong Twin Shear constitutive model and the concept of damage plane. Material stiffness damage degradation impact on the yield process of concrete yield plane was considered. This article developed a concrete Twin Shear damage constitutive model in FLAC3D environment. The model is simple and easy to practical engineering applications, and the model has high accuracy. Thereby, this paper tries to explore a new damage constitutive model for concrete.

Parameter Identification of a Plastic Damage Model

Studies on parameter identification of a plasticity-based damage constitutive model for concrete are presented in this paper. Differences between the stress-strain curves experimentally obtained and the ones numerically obtained at local level were used as the objective functional of a regularized least square method. For solving the inverse problem, the solution of the direct problem at local level obtained by a driver subroutine was embedded in the iterative solution procedure for the inverse problem proposed in this paper. The sensitivity matrix was calculated numerically by the finite difference method. Numerical examples are given for fitting the numerically obtained stress-strain curves on to a set of experimental results. Parameter identifications under various loading cases, which include uniaxial extension and triaxial compression with different confining stresses, were performed. Results indicate that the numerical scheme is stable and has reasonable accuracy.

Statistical Damage Constitutive Model for Concrete under Biaxial Tension

Based on the statistical damage theory and the experimental phenomena, the statistical damage constitutive model for concrete under biaxial tension is proposed. The two meso-scale damage modes, rupture and yield are considered, and the whole damage evolution process is driven by the principal tensile damage strain. The results show that the proposed statistical damage model can accurately predict the constitutive behavior in the uniform damage phase for concrete under biaxial tension. The damage mechanism is discussed in the view point of biaxial strength and deformation properties.

A thermodynamics-based damage constitutive model of concrete

A thermodynamics-based damage constitutive model is developed for concrete, which describes tensile and compressive damage well and follows the second thermodynamic law. Constitutive model should meet general thermodynamics, while it describes behaviour characteristic of concrete material, which are often not able to be satisfied by existing models because of various of hypotheses. Generalised stress functions and dissipative generalised stress functions are constructed from free energy function and energy dissipation function according to the physical meaning of the thermodynamic potential and the characteristic of the constitutive model of concrete. Then, a damage constitutive model of concrete is developed and the parameters of the model are identified. The numerical method of the model is also presented. The model in the paper can satisfy the second thermodynamic law automatically and simulate the tensile and compressive behaviour of concrete well. Finally, the feasibility and practicality of the model is verified by the analysis of classical experiments and Koyna dam.

Coupled elasto-plasticity damage constitutive models for concrete

The paper is to design and construct a coupled elasto-plasticity damage constitutive model for concrete. Based on the energy dissipation principle, the Hsieh-Ting-Chen four-parameter yield function is used. The model can reflect different strength characteristics of concrete in tension and compression, and reduce the limitation and lacuna of the traditional damage constitutive models for concrete. Furthermore, numerical test for concrete stress-strain relation under uniaxial tension and compression is given. Moreover, the damage process of concrete gravity dam is calculated and analyzed in seismic load. Compared with other damage constitutive models, the proposed model contains only one unknown parameter and the other parameters can be found in the Hsieh-Ting-Chen four-parameter yield function. The same damage evolution law, which is used for tension and compression, is good for determining stress-strain constitutive and damage characteristics in complex stress state. This coupled damage constitutive models can be applied in analyzing damage of concrete gravity dam and arch dam.

An elastoplastic damage constitutive model for concrete

An elastoplastic damage constitutive model to simulate nonlinear behavior of concrete is presented. Similar to traditional plastic theory, the irreversible deformation is modeled in effective stress space. In order to better describe different stiffness degradation mechanisms of concrete under tensile and compressive loading conditions, two damage variables, i.e., tension and compression are introduced, to quantitatively evaluate the degree of deterioration of concrete structure. The rate dependent behavior is taken into account, and this model is derived firmly in the framework of irreversible thermodynamics. Fully implicit backward-Euler algorithm is suggested to perform constitutive integration. Numerical results of the model accord well with the test results for specimens under uniaxial tension and compression, biaxial loading and triaxial loading. Failure processes of double-edge-notched (DEN) specimen are also simulated to further validate the proposed model.

Rate dependent plastic–damage constitutive model of concrete

Generally, on the plastic and damage constitutive model, the plasticity consistency condition of the yield function and the damage consistency condition of the damage evolution could not be satisfied when the effect of strain rates was taken into account. The viscoplastic strain was determined by the viscoplastic flow theorem. In this paper, the rate dependent consistency plastic–damage model of concrete is proposed by imposing the consistency condition for the yield function and the damage evolution criterion. The Drucker–Prager yield function and the damage evolution criterion proposed by the authors, taken into account the effect of strain rates on dynamic behaviours of concrete, are adopted. Based on these assumptions, the dynamic damage evolution equation and the constitutive model of concrete are deduced. Then, a numerical algorithm similar to Euler backward mapping schemes for rate independent plasticity is proposed by the authors to calculate the rate dependent plastic–damage model of concrete. Finally, the model is compared with the uniaxial tensile and compressive damage experimental results.

Study on Non-Local Damage Constitutive Model of Concrete under Freeze-Thaw Action

Concrete is multi-phase composites. Due to the inhomogeneity of mechanical properties and complexity of physical properties, constitutive relations of concrete are more complicated. Starting from irreversible thermodynamics theory, internal state variable theory and nonlocal field theory, non-local damage constitutive model of concrete under freeze-thaw action is established in this paper. In the model, non-local influence functions are discussed which are used to describe interplay of damage between adjacent point.

Fracture and Damage Behaviors of Concrete in the Fractal Space

The fracture toughness, the driving force and the fracture energy for an infinite plate with a fractal crack are investigated in the fractal space in this work. The perimeter-area relation is adopted to derive the transforma-tion rule between damage variables in the fractal space and Euclidean space. A plasticity yield criterion is introduced and a damage variable tensor is decomposed into tensile and compressive components to describe the distinct behaviors in tension and compression. A plastic damage constitutive model for concrete in the Euclidean space is developed and generalized to fractal case according to the transformation rule of damage variables. Numerical calculations of the present model with and without fractal are conducted and compared with experimental data to verify the efficiency of this model and show the necessity of considering the fractal effect in the constitutive model of concrete. The structural response and mesh sensitivity of a notched unre-inforced concrete beam under 3-point bending test are theoretical studied and show good agreement with the experimental data.