• Computers and Concrete
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• 제22권1호
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• pp.1-10
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• 2018

In this study an implicit algorithm for modeling of propagation of macrocracks in 3D concrete structures suffering from alkali-silica reaction has been developed and implemented. The formulation of the problem prior to the onset of localized deformation is based on a chemo-elasticity approach. The localized deformation mode, involving the formation of macrocracks, is described using a simplified form of the strong discontinuity approach (SDA) that employs a volume averaging technique enhanced by a numerical procedure for tracing the propagation path in 3D space. The latter incorporates a non-local smoothening algorithm. The formulation is illustrated by a number of numerical examples that examine the crack propagation pattern in both plain and reinforced concrete under different loading scenarios.

• Structural Engineering and Mechanics
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• 제5권6호
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• pp.743-754
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• 1997

A three-dimensional constitutive modeling for reinforced concrete is presented for finite element nonlinear analysis of reinforced concrete. The targets of interest to the authors are columns confined by lateral steel hoops, RC thin shells subjected to combined in-plane and out-of-plane actions and massive structures of three-dimensional (3D) extent in shear. The elasto-plastic and continuum fracture law is applied to pre-cracked solid concrete. For post cracking formulation, fixed multi-directional smeared crack model is adopted for RC domains of 3D geometry subjected to monotonic and reversed cyclic actions. The authors propose a new scheme of decomposing stress strain fields into sub-planes on which 2D constitutive laws can be applied. The proposed model for 3D reinforced concrete is experimentally verified in both member and structural levels under cyclic actions.

• 대한기계학회논문집A
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• 제24권3호
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• pp.634-644
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• 2000

Fatigue crack growth and life is estimated by various fracture mechanical parameters but affected by load, material and environment. Fatigue character of component without surface notch cannot be e valuated by above-mentioned parameters due to microstructure of in-service material. Single fracture mechanical parameter or nondestructive parameter cannot predict fatigue damage in arbitrary boundary condition but multiple fracture mechanical parameters or nondestructive parameters can Fatigue crack growth modelling with three point representation scheme uses this merit but has limit on real-time monitoring. Therefore, this study shows fatigue damage model using backpropagatior. neural networks on the basis of X-ray half breadth ratio B/$B_o$ fractal dimension $D_f$ and fracture mechanical parameters can predict fatigue crack growth rate da/dN and cycle ratioN/$N_f$ at the same time within engineering estimated mean error(5%).

• 한국전산구조공학회논문집
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• 제30권1호
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• pp.31-37
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• 2017

본 논문에서는 이종재질로 구성된 세장비가 큰 보의 차원축소와 복원의 효율성과 정확성을 입증하기 위하여 VABS와 3차원 유한요소해석 모델의 결과와 비교하였다. 그리고 3차원 유한요소모델과 차원축소 모델을 가상균열닫힘법을 이용하여 에너지 해방률을 계산하였다. 원형과 사각형의 단면에 초기 크랙을 가진 수치모델을 이용하여 보의 차원축소와 복원기법 및 가상균열닫힘법을 이용하여 복원해석 결과 및 에너지 해방률을 비교하여 효율성과 정확성을 입증하였다. 특히 제시된 에너지 해방률 계산 기법은 고고도 무인기의 날개, 헬리콥터 로터 블레이드, 풍력 블레이드, 틸트로터 등의 정적, 동적 모델링 및 수명평가에 활용될 수 있을 것이다.

• 한국전산구조공학회논문집
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• 제15권4호
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• pp.649-659
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• 2002

다양한 평면변형률 시편들의 균열선단 탄·소성 응력상태들에 대한 경우, 여러 연구들을 동해, J-T접근방법의 유효 타당성이 충분히 검증되어졌다. 그러나 J-T 두 변수에 의한 균열선단 응력장 예측의 타당성을 보편화시키기 위해서는, 평면변형률 시편들과 같이 이상화된 구조가 아닌 실제적인 3차원 구조형상에 대한 연구가 필요하다. 이를 배경으로 본 연구에서는 평판과 직관에 대해 완전 3차원 유한요소해석을 수행하여 얻어진 응력장과 계산된 J-T두 변수로 예측되는 응력장을 비교함으로써, J-T 접근방법의 유효성 내지 한계성을 규명하였다.

• International Journal of Internet, Broadcasting and Communication
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• 제16권1호
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• pp.140-147
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• 2024

In Current artificial structures, we must periodically make their safety inspections. In this process, we should consider the safety of workers and the accuracy of safety checks and also consider time and cost savings for safety inspections. Additionally, in the fields of architecture and civil engineering, we are unavoidable the use of foreign commercialized BIM model tools. To address these challenges, we propose mapping crack areas and BIM 3D design drawings based on augmented reality (AR) for the safety inspection of Huge Bridges. For this purpose, we define indexing of 2D/3D drawing models, create the tabulation of all 2D/3D drawings into a database, analyze QR codes, and finally integrate with augmented reality devices. we may expect our method to improve the efficiency of safety inspections on bridge sites. Moreover, we will enable the domestics of our pure technology.

• 비파괴검사학회지
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• 제23권3호
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• pp.189-197
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• 2003

Nucleation of a crack is readily defected by acoustic emission (AE) method. One powerful technique for AE waveform analysis has been developed as SiGMh (Simplified Greens functions for Moment tensor Analysis), as crack kinematics of locations, types and orientations are quantitatively determined. Because these kinematical outcomes are obtained as three-dimensional (3-D) locations and vectors, 3-D visualization is definitely desirable. To this end, the visualization system has been developed by using VRML (Virtual Reality Modeling Language). As an application, failure protest of a reinforced concrete beam is discussed.

• 한국안전학회지
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• 제36권1호
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• pp.18-25
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• 2021

In many developed countries, such as South Korea, efficiently maintaining the aging infrastructures is an important issue. Currently, inspectors visually inspect the infrastructure for maintenance needs, but this method is inefficient due to its high costs, long logistic times, and hazards to the inspectors. Thus, in this paper, a novel crack inspection approach for concrete bridges is proposed using integrated image processing techniques. The proposed approach consists of four steps: (1) training a deep learning model to automatically detect cracks on concrete bridges, (2) acquiring in-situ images using a drone, (3) generating orthomosaic images based on 3D modeling, and (4) detecting cracks on the orthmosaic image using the trained deep learning model. Cascade Mask R-CNN, a state-of-the-art instance segmentation deep learning model, was trained with 3235 crack images that included 2415 hard negative images. We selected the Tancheon overpass, located in Seoul, South Korea, as a testbed for the proposed approach, and we captured images of pier 34-37 and slab 34-36 using a commercial drone. Agisoft Metashape was utilized as a 3D model generation program to generate an orthomosaic of the captured images. We applied the proposed approach to four orthomosaic images that displayed the front, back, left, and right sides of pier 37. Using pixel-level precision referencing visual inspection of the captured images, we evaluated the trained Cascade Mask R-CNN's crack detection performance. At the coping of the front side of pier 37, the model obtained its best precision: 94.34%. It achieved an average precision of 72.93% for the orthomosaics of the four sides of the pier. The test results show that this proposed approach for crack detection can be a suitable alternative to the conventional visual inspection method.

• Interaction and multiscale mechanics
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• 제4권1호
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• pp.35-47
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• 2011

A global-local finite element modeling technique is employed in this paper to predict the fatigue life of radial truck tires. This paper assumes that a flaw exists inside the tire, in the local model. The local model uses an FEM fracture analysis in conjunction with a global-local technique in ABAQUS. A 3D finite element local model calculates the energy release rate at the belt edge. Using the analysis of the local model, a study of the energy release rate is performed in the crack region and used to determine the crack growth rate analysis. The result considers how different driving conditions contribute to the detrimental effects of belt separation in truck tire failure. The calculation of the total mileage on four sizes of radial truck tires has performed on the belt edge separation. The effect of the change of belt width design on the fatigue lifetime of tire belt separation is discussed.

• Coupled systems mechanics
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• 제9권2호
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• pp.125-145
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• 2020

In this paper, we present a 3D thermo-hydro-mechanical coupled discrete beam lattice model of structure built of the nonisothermal saturated poro-plastic medium subjected to mechanical loads and nonstationary heat transfer conditions. The proposed model is based on Voronoi cell representation of the domain with cohesive links represented as inelastic Timoshenko beam finite elements enhanced with additional kinematics in terms of embedded strong discontinuities in axial and both transverse directions. The enhanced Timoshenko beam finite element is capable of modeling crack formation in mode I, mode II and mode III. Mode I relates to crack opening, mode II relates to in-plane crack sliding, and mode III relates to the out-of-plane shear sliding. The pore fluid flow and heat flow in the proposed model are governed by Darcy's law and Fourier's law for heat conduction, respectively. The pore pressure field and temperature field are approximated with linear tetrahedral finite elements. By exploiting nodal point quadrature rule for numerical integration on tetrahedral finite elements and duality property between Voronoi diagram and Delaunay tetrahedralization, the numerical implementation of the coupling results with additional pore pressure and temperature degrees of freedom placed at each node of a Timoshenko beam finite element. The results of several numerical simulations are presented and discussed.