• Coupled systems mechanics
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• 제8권4호
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• pp.289-298
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• 2019

Reinforced concrete can be considered as a heterogeneous material consisting of coarse aggregate, mortar mix and reinforcing bars. This paper presents a two-dimensional mesoscopic analysis of reinforced concrete beams using a simple two-phase mesoscopic model for concrete. The two phases of concrete, coarse aggregate and mortar mix are bonded together with reinforcement bars so that inter force transfer will occur through the material surfaces. Monte Carlo's method is used to generate the random aggregate structure using the constitutive model at mesoscale. The generated models have meshed such that there is no material discontinuity within the elements. The proposed model simulates the load-deflection behavior, crack pattern and ultimate load of reinforced concrete beams reasonably well.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.53-59
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• 2004

Rough surfaces are taking into account to estimate the contact fatigue life. A computational methodology and the theoretical basis in this case is presented in this paper. Displacement solution technique by Cho and Love is applied to calculate the stress history beneath the surface subjected to loading. Mesoscopic multiaxial fatigue criterion is then applied to predict fatigue life. This fatigue criterion yields satisfactory results for non-proportional loading and can satisfactorily describe the physical mechanisms of crack initiation as well. As a result of analysis the relation between the life and the roughness as well as the most probable depth of the crack nucleation is discussed.

• Interaction and multiscale mechanics
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• 제3권1호
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• pp.23-37
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• 2010

Concrete is a heterogeneous material consisting of coarse aggregate, mortar matrix and interfacial zones at the meso level. Though studies have been done to interpret the fracture process in concrete using meso level models, not much work has been done for simulating the macroscopic behaviour of reinforced concrete structures using the meso level models. This paper presents a procedure for the mesoscopic analysis of reinforced concrete beams using a modified micro truss model. The micro truss model is derived based on the framework method and uses the lattice meshes for representing the coarse aggregate (CA), mortar matrix, interfacial zones and reinforcement bars. A simple procedure for generating a random aggregate structure is developed using the constitutive model at meso level. The study reveals the potential of the mesoscopic numerical simulation using a modified micro truss model to predict the nonlinear response of reinforced concrete structures. The modified micro truss model correctly predicts the load-deflection behaviour, crack pattern and ultimate load of reinforced concrete beams failing under different failure modes.

• Structural Engineering and Mechanics
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• 제37권2호
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• pp.215-231
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• 2011

As a brittle and heterogeneous material, concrete behaves differently under different stress conditions and its bulk strength is loading rate dependent. To a large extent, the varying behavioural properties of concrete can be explained by the mechanical failure processes at a mesoscopic level. The development of a computational mesoscale model in a general finite element environment, as presented in the preceding companion paper (Part 1), makes it possible to investigate into the underlying mechanisms governing the bulk-scale behaviour of concrete under a variety of loading conditions and to characterise the variation in quantitative terms. In this paper, we first present a series of parametric studies on the behaviour of concrete material under quasi-static compression and tension conditions. The loading-face friction effect, the possible influences of the non-homogeneity within the mortar and ITZ phases, and the effect of randomness of coarse aggregates are examined. The mesoscale model is then applied to analyze the dynamic behaviour of concrete under high rate loading conditions. The potential contribution of the mesoscopic heterogeneity towards the generally recognized rate enhancement of the material compressive strength is discussed.

• Computers and Concrete
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• 제21권4호
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• pp.471-484
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• 2018

Refined analysis depicting mass transportation and physicochemical reaction and reasonable computing load with acceptable DOFs are the two major challenges of numerical simulation for concrete durability. Mesoscopic numerical simulation for chloride diffusion considering binder, aggregate and interfacial transition zone is unable to be expended to the full structure due to huge number of DOFs. In this paper, a multiscale approach of combining both mesoscopic model including full-graded aggregate and equivalent macroscopic model was introduced. An equivalent conversion of chloride content at the Interfacial Transition Layer (ITL) connecting both models was considered. Feasibility and relative error were discussed by analytical deduction and numerical simulation. Case study clearly showed that larger analysis model in multiscale model expanded the diffusion space of chloride ion and decreased chloride content in front of rebar. Difference for single-scale simulation and multiscale approach was observed. Finally, this paper addressed some worth-noting conclusions about the chloride distribution and rebar corrosion regarding the configuration of rebar placement, rebar diameter, concrete cover and exposure period.

• 대한기계학회논문집A
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• 제28권5호
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• pp.563-570
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• 2004

Two-dimensional mesoscopic analysis (meso-analysis) is applied to solids including microdefects such as microcracks or holes. For the problem of effective moduli of microdefrcted solids, various approximate schemes are introduced by using microcrack density and hole density for macro level parameter. Also, microcracks distributed in the parallel direction and random direction are considered. Several numerical studies using meso-analysis are carried out and the results are compared with several approximate schemes in order to show the validity of proposed meso-analysis.

• Computers and Concrete
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• 제23권1호
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• pp.69-80
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• 2019

Modeling approach for mesoscopic model of concrete depicting mass transportation and physicochemical reaction is important since there is growing demand for accuracy and computational efficiency of numerical simulation. Mesoscopic numerical simulation considering binder, aggregate and Interfacial Transition Zone (ITZ) generally produces huge number of DOFs, which is inapplicable for full structure. In this paper, a three-dimensional multiscale approach describing three-phase structure of concrete was discussed numerically. An effective approach generating random aggregate in polygon based on checking centroid distance was introduced. Moreover, ITZ elements were built by parallel expanding the surface of aggregates on inner side. By combining mesoscopic model including full-graded aggregate and macroscopic model, cases related to diffusivity and thickness of ITZ, volume fraction and grade of aggregate were studied regarding the consideration of multiscale compensation. Results clearly showed that larger analysis model in multiscale model expanded the diffusion space of chloride ion and decreased chloride content in front of rebar. Finally, this paper addressed some worth-noting conclusions about the chloride distribution and rebar corrosion regarding the configuration of, rebar diameter, concrete cover and exposure period.

• Structural Engineering and Mechanics
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• 제24권2호
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• pp.181-194
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• 2006

The masonry is a complex heterogeneous material and its shear deformation and fracture is associated with very complicated progressive failures in masonry structure, and is investigated in this paper using a mesoscopic mechanical modelling, Considering the heterogeneity of masonry material, based on the damage mechanics and elastic-brittle theory, the newly developed Material Failure Process Analysis (MFPA) system was brought out to simulate the cracking process of masonry, which was considered as a three-phase composite of the block phase, the mortar phase and the block-mortar interfaces. The crack propagation processes simulated with this model shows good agreement with those of experimental observations by other researchers. This finding indicates that the shear fracture of masonry observed at the macroscopic level is predominantly caused by tensile damage at the mesoscopic level. Some brittle materials are so weak in tension relative to shear that tensile rather than shear fractures are generated in pure shear loading.

• Spatial Information Research
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• 제21권5호
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• pp.33-41
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• 2013

최근, 각종 자연재해와 산업재해로 인한 피해규모의 증가와 이에 따른 대책 수립의 필요성이 증가하고 있으며 재난 규모 역시 대형화, 거대화됨에 따라 피해규모는 점점 더 심각해지고 있다. 이러한 각종 재난 시 재난대피계획의 핵심은 재난대피에 소요되는 시간추정, 병목지점 파악 등을 포함하며 이러한 재난대피계획의 수립과 평가를 위해서는 적절한 재난대피모델이 필요하다. 또한, 기존 연구가 주로 건축물 실내를 대상으로 재난 시 대피경로분석이 주를 이루기 때문에, 자연재해 시 지역을 대상으로 하는 재난대피모델에 관한 연구가 미진하여 도시 내의 재해영향권에 대한 재난대피모델 구축 사례가 없는 실정이다. 이에 본 연구에서는 Cube Avenue를 이용하여 거시통행 수요모형을 설계하고 미국 노스 다코다(North Dakota)주의 파고(Fargo)시의 도로 네트워크를 대상으로 재난 대피 시뮬레이션을 수행하였다. 결과적으로 본 연구에서 제안된 중규모 재난대피모델은 기존 통행수요모형의 네트워크와 입력 변수들을 이용하여서 동적 분석을 할 수 있어 시간과 비용을 절약할 수 있는 재난대피 시뮬레이션 분석에 활용 가능함을 확인할 수 있었다. 본 연구의 결과는 향후, 국내 대도시권에 적용이 가능하며 시나리오를 기반으로 한 다양한 재난모의 실험 및 평가가 가능한 모델 개발에 활용 가능할 것이다.

• Structural Engineering and Mechanics
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• 제19권5호
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• pp.519-533
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• 2005

The numerical simulations on the influence of mesoscopic structures on the macroscopic strength and fracture characteristics are carried out based on that the concrete is assumed to be a three-phase composite composed of matrix (mortar), aggregate and bond between them by using a numerical code named MFPA. The finite element program is employed as the basic stress analysis tool when the elastic damage mechanics is used to describe the constitutive law of meso-level element and the maximum tensile strain criterion and Mohr-Coulomb criterion are utilized as damage threshold. It can be found from the numerical results that the bond between matrix and aggregate has a significant effect on the macroscopic mechanical performance of concrete.