• Computers and Concrete
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• 제33권3호
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• pp.301-308
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• 2024

This paper proposes a numerically-based methodology to implicitly model irreversible deformations in concrete through a damage model. Plasticity theory is not explicitly employed, although resemblances are still present. A scalar isotropic damage model is adopted and the damage variable is split in two: one contributing for stiffness degradation (cracking) and other contributing for irreversible deformations (plasticity). The proposed methodology is thermodynamically consistent as it consists in a damage model rewritten in different terms. Its Finite Element coding is presented, indicating that minor changes are necessary. It is also demonstrated that nonlinear algorithms are unnecessary to model concrete cracking and plasticity. Experimental data from direct tension and four-point bending tests under cyclic loading are compared to the proposed methodology. A numerical case study of a low-cycle fatigue is also presented. It can be concluded that the model is simple, feasible and capable to capture the essentials concerning cracking and plasticity.

• International Journal of Concrete Structures and Materials
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• 제2권2호
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• pp.123-136
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• 2008

A new plastic-damage constitutive model applicable to lightweight concrete (LWC) and normal weight concrete (NWC) is proposed in this paper based on both continuum damage mechanics and plasticity theories. Two damage variables are used to represent tensile and compressive damage independently. The effective stress is computed in the Drucker-Prager multi-surface plasticity framework. The stress is then computed by multiplication of the damaged part and the effective part. The proposed model is coded as a user material subroutine and incorporated in a finite element analysis software. The constitutive integration algorithm is implemented by adopting the operator split involving elastic predictor, plastic corrector and damage corrector. The numerical study shows that the algorithm is efficient and robust in the finite element analysis. Experimental investigation is conducted to verify the proposed model involving both static and dynamic tests. The very good agreement between the numerical results and experimental results demonstrates the capability of the proposed model to capture the behaviors of LWC and NWC structures for static and impact loading.

• International Journal of Concrete Structures and Materials
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• 제9권1호
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• pp.45-54
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• 2015

This paper describes a three-dimensional approach to modeling the nonlinear behavior of partial-depth precast prestressed concrete bridge decks under increasing static loading. Six full-size panels were analyzed with this approach where the damage plasticity constitutive model was used to model concrete. Numerical results were compared and validated with the experimental data and showed reasonable agreement. The discrepancy between numerical and experimental values of load capacities was within six while the discrepancy of mid-span displacement was within 10 %. Parametric study was also conducted to show that higher accuracy could be achieved with lower values of the viscosity parameter but with an increase in the calculation effort.

• 콘크리트학회논문집
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• 제19권5호
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• pp.655-664
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• 2007

콘크리트의 인장균열에 따른 방향적 비국소 손상이라는 특징은 인장-압축을 받는 철근콘크리트 전단 부재에서 회전인장균열 특성 및 압축강도 감소 현상을 일으킨다. 본 연구에서는 인장과 압축거동에 대하여 다른 손상 모델을 사용하는 기존의 방법과는 달리, 동일한 인장균열 손상 모델을 사용하여, 인장균열거동과 압축연화거동을 나타낸다. 이러한 비국소 균열 손상의 영향을 나타낼 수 있는 소성모델을 개발하기 위하여 미소면 모델의 개념을 도입한다. 기존의 소성모델과 달리, 비국소 균열 손상을 나타내기 위하여 인장과 압축의 소성파괴면은 각 미소면에서 정의하며, 각 미소파괴면의 조합에 의하여 대표파괴면을 정의한다. 이때, 방향적 비국소 균열 손상을 나타내는 소성인장변형률의 영향에 의하여 각 미소면의 인장과 압축 소성변형률의 크기가 결정된다. 본 연구에서 개발된 소성모델은 유한요소해석에 적용되며, 다양한 전단패널의 기존 실험 결과들과 비교하여 제안된 재료 모델의 유효성을 검증한다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.914-921
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• 2006

To describe the effect of the numerous and various oriented microcracks on the compressive and tensile concrete behaviors, the directional nonlocality is defined. The plasticity model using multiple failure criteria is developed for RC planar members in tension-compression. The crack damages are defined in the pre-determined reference orientations, and then the total crack damage is calculated by integrating multi-oriented crack damages. To describe the effect of directional nonlocality on the anisotropic tensile damage, based on the existing test results, the nonlocal damage factor is defined in each reference orientation. The reduced compressive strength in the cracked concrete is defined by the multi-oriented crack damages defined as excluding the tensile normal plastic strain from the compressive equivalent plastic strain. The proposed model is implemented to finite element analysis, and it is verified by comparisons with various existing panel test results.

• Computers and Concrete
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• 제33권2호
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• pp.147-162
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• 2024

This study presents a random-aggregate mesoscale model integrating the random distribution of the coarse aggerates and the damage mechanics of the mortar and interfacial transition zone (ITZ). This mesoscale model can generate the random distribution of the coarse aggregates according to the prescribed particle size distribution which enables the automation of the current methodology with different coarse aggregates' distribution. The main innovation of this work is to propose the "correction factor" to eliminate the dimensionally dependent mesh sensitivity of the concrete damaged plasticity (CDP) model. After implementing the correction factor through the user-defined subroutine in the randomly meshed mesoscale model, the predicted fracture resistance is in good agreement with the average experimental results of a series of geometrically similar single-edge-notched beams (SENB) concrete specimens. The simulated cracking pattern is also more realistic than the conventional concrete material models. The proposed random-aggregate mesoscale model hence demonstrates its validity in the application of concrete fracture failure and statistical size effect analysis.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.451-454
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• 1999

An existing plasticity model using multiple failure criteria is modified to describe the behavior of reinforced concrete planar members under cyclic load. Multiple failure criteria are used to define both isotropic damage of compressive crushing and anisotropic damage of tensile cracking. A numerical method is developed to define multi-directional and non-orthogonal crack directions. The material model is implemented in the finite element analysis and verified by comparison with existing experiments of reinforced concrete shear wall.

• Computers and Concrete
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• 제23권3호
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• pp.171-188
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• 2019

This study proposed a new and efficient 2D damage-plasticity model within the framework of Isogeometric analysis (IGA) for the geometrically nonlinear damage analysis of concrete. Since concrete exhibits complicated material properties, two internal variables are introduced to measure the hardening/softening behavior of concrete in tension and compression, and an implicit gradient-enhanced formulation is adopted to restore the well-posedness of the boundary value problem. The numerical results calculated by the model is compared with the experimental data of three benchmark problems of plain concrete (three-point and four-point bending single-notched beams and four-point bending double-notched beam) to illustrate the geometrical flexibility, accuracy, and robustness of the proposed approach. In addition, the influence of the characteristic length on the numerical results of each problem is investigated.

• 콘크리트학회논문집
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• 제14권2호
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• pp.239-248
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• 2002

철근 콘크리트 면부재의 주기거동을 나타내기 위하여 소성모델과 손상모델의 통합구성모델을 개발하였다. 인장-압축을 받는 콘크리트의 응력은 개념적으로 콘크리트의 스트럿 작용에 의한 압축응력과 인장균열에 의한 인장응력의 합으로 정의하였다. 인장균열의 비등방손상에 의하여 영향을 받는 압축파괴의 등방손상을 나타내기 위하여 다중파괴기준을 갖는 소성모델을 사용하였으며, 다중균열 방향에서 인장응력-변형률 관계를 나타내기 위하여 다중고정균열손상모델과 인장균열의 소성유동모델의 개념을 사용하였다. 이러한 통합모델은 주기 인장-압축 상태의 철근 콘크리트의 거동측성, 즉 다중 인장균열 방향, 점진적으로 회전하는 균열 손상, 콘크리트의 압축파괴를 나타낼 수 있다. 제안된 구성모델은 유한요소해석에 적용되었으며, 주기하중을 받는 철근 콘크리트 전단패널 및 전단벽에 대한 기존의 실험결과들과의 비교를 통해 검증되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.633-636
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• 2006

Impact damage modeling of concrete under high strain rate loading conditions is investigated. A phenomenological penetration model that can account for complicated impact and penetration process such as the rate and loading history response of concrete, the microstructure-penetration interaction etc. is discussed. Constitutive law compatible with Second Law of thermodynamics and coupled damage and plasticity modelling based on continuum damage mechanics are also examined. The purpose of this paper is preliminarily to study with respect to impact and penetration models for concrete before the development of that model.