• International Journal of Concrete Structures and Materials
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• 제19권1E호
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• pp.25-32
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• 2007

The fracture energy evaluated from the previous experimental results can be simulated by using the modified singular fracture process zone (S-FPZ) model. The fracture model has two fracture properties of strain energy release rate for crack extension and crack close stress versus crack width relationship $f_{ccs}(w)$ for fracture process zone (FPZ) development. The $f_{ccs}(w)$ relationship is not sensitive to specimen geometry and crack velocity. The fracture energy rate in the FPZ increases linearly with crack extension until the FPZ is fully developed. The fracture criterion of the strain energy release rate depends on specimen geometry and crack velocity as a function of crack extension. The behaviors of micro-cracking, micro-crack localization and full development of the FPZ in concrete can be explained theoretically with the variation of strain energy release rate with crack extension.

• Advances in nano research
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• 제3권3호
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• pp.143-168
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• 2015

Initiation of crack and its growth simulation requires accurate model of traction - separation law. Accurate modeling of traction-separation law remains always a great challenge. Atomistic simulations based prediction has great potential in arriving at accurate traction-separation law. The present paper is aimed at establishing a method to address the above problem. A method for traction-separation law prediction via utilizing atomistic simulations data has been proposed. In this direction, firstly, a simpler approach of common neighbor analysis (CNA) for the prediction of crack growth has been proposed and results have been compared with previously used approach of threshold potential energy. Next, a scheme for prediction of crack speed has been demonstrated based on the stable crack growth criteria. Also, an algorithm has been proposed that utilizes a variable relaxation time period for the computation of crack growth, accurate stress behavior, and traction-separation atomistic law. An understanding has been established for the generation of smoother traction-separation law (including the effect of free surface) from a huge amount of raw atomistic data. A new curve fit has also been proposed for predicting traction-separation data generated from the molecular dynamics simulations. The proposed traction-separation law has also been compared with the polynomial and exponential model used earlier for the prediction of traction-separation law for the bulk materials.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.635-638
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• 1999

The crack of concrete is one of the most important factors to evaluate the safety of the structures. The more important point for the safety-evaluation of the concrete structures is to check the crack development, the conventional window paper (Chang Ho Ji) have been used as a simple method in the past, and nowadays the strain gauge is used for more correct way to check the development of the concrete crack quantitatively. However the window-paper method is too simple and not so scientific, and the strain-gauge method is rather complicated for people in general. This Easy-Check Sensor provides the simple usage for the various concrete structures, but also the more correct results to evaluate the development of the concrete crack.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 봄 학술논문 발표대회
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• pp.162-163
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• 2021

Currently, the depth of cracks is measured using ultrasonic detectors in maintenance practice. This method consists of measuring the depth of cracks by attaching ultrasonic depth measuring equipment to the concrete surface, and there are restrictions on the timing and location of the inspection. These limitations can be addressed through the development of image-based crack depth measurement AI technology. If crack depth measurements are made based on images, restrictions on the timing and location of inspections can be lifted because images acquired with simple filming equipment can be used as input information. To efficiently develop these artificial intelligence technologies, it is essential to identify the interrelationship between crack depth measurements and image characteristic information. Thus, this study is a basic study of the development of image-based crack depth measurement AI technology and aims to identify image characteristic information related to crack depth.

• 한국안전학회지
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• 제20권1호
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• pp.62-67
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• 2005

An eccentrically-loaded single edge crack tension specimen (ESET) is similar to a compact tension(CT) specimen loaded in tension-tension. The standard ESET specimen exhibits advantages over other types of cracked specimen, such as n, single-edge crack, and middle-crack tension specimen. The details of ESET specimen configuration, test procedure, and calculations are described in ASTM E647 standard. However, a difficulty in attaching COD gage to the knife-edge on the front foe of the specimen can be found when the size of ESET specimen is small for rapid cooling and heating in thermal fatigue testing. The finite element analysis is performed for the ESET specimen with projected knife-edge on the front foe and a crack-length-compliance equation is suggested for the new specimen configuration. Calibration test are conducted with 347 stainless steel to compare the measured crack length with the calculated crack length from the suggested compliance expression. The test results showed good agreements with those of analysis.

• 한국건설순환자원학회논문집
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• 제9권3호
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• pp.359-366
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• 2021

본 연구에서는 자기 치유 콘크리트의 주요 손상인 균열을 측정하고 이를 DB화 하기 위한 이미지 처리 기법 기반의 균열 모니터링 자동화 시스템 개발의 일환으로 균열 촬영 장비를 제작하고 균열 검출 및 분석이 가능한 프로그램을 개발하였다. 본 시스템은 기존의 육안으로 균열을 점검하는 외관조사를 대체하여 객관적이고 정량적인 데이터를 제공한다. 개발 시스템의 검증은 가상균열을 이용한 실내시험을 통해 균열 검출 알고리즘을 검증하였으며 자기치유 보수 모르타르 시공 현장에 적용하여 균열 검출 및 균열폭의 변화량을 모니터링하였다. 이미지 분석을 통해 검출된 균열폭의 경우 실측 균열폭과의 차이가 최대 0.0334mm로 나타났으며, 현장적용 결과 0.1mm 이하의 미세 균열 검출까지 가능하였으며 자기치유 보수 모르타르의 시간 경과에 따른 균열치유 효과를 균열폭 감소를 통해 확인할 수 있었다.

• 한국지반공학회논문집
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• 제23권9호
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• pp.29-37
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• 2007

본 연구에서는 카올린점토에 대한 실내실험을 통하여 수축으로 인한 균열발생을 조사하고 균열 단계를 모사할 수 있는 단순모델을 제안하였다. CPS 기법을 이용하여 디지털 카메라에 의해 얻은 균열 이미지를 분석하였다. 함수비의 감소에 따라 균열의 길이와 면적은 1차 균열단계, 2차 균열단계, 수축단계 균열의 3단계로 나타났다. 균열 면적의 1차 및 2차 균열 최종 단계에서의 정규화된 함수비는 시료 두께에 상관없이 각각 0.92와 0.70에서 발생하였다. 반면 균열 길이는 1차 균열 최종 단계에서의 함수비는 시료 두께와 상관없이 0.92에서 발생하였으나, 2차 균열 최종 단계에서의 함수비는 시료 두께가 0.5, 1.0, 2.0cm로 증가함에 따라 함수비는 0.79, 0.82, 0.85로 증가하였다. 수축 균열을 모사할 수 있는 3개의 직선으로 구성된 단순모델을 제안하였다.

• 한국정밀공학회지
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• 제16권2호통권95호
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• pp.225-233
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• 1999

This paper describes a versatile finite element technique which has been used to investigate of wide range of structural defects of practical importance. The procedure automatically remeshes the three-dimensional finite element model during the stages of crack growth. Problems analyzed to date include the surface cracks in leak-before-break situations, the development of quarter-elliptical corner defects, planar semi-elliptical surface defects and the fatigue growth of defects.

• Structural Engineering and Mechanics
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• 제44권2호
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• pp.257-266
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• 2012

Walls are the most important vertical load-carrying elements of masonry structures. Their bond designs are different from one country to another. This paper presents the shear effects of some structural bond designs commonly used for masonry walls. Six different bond designs are considered and modeled using finite element procedures under lateral loading to examine the shear behavior of masonry walls. To obtain accurate results, finite element models are assumed in the inelastic region. Crack development patterns for each wall are illustrated on deformed meshes, and the numerical results are compared.

• Journal of Advanced Marine Engineering and Technology
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• 제25권5호
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• pp.1058-1064
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• 2001

In this paper, the development of probability distribution estimation program for fatigue crack growth lives was summarize. The probability distribution estimation program of life was developed to increase the reliability of life estimation. In this study, it is considered that the cause of scatter in fatigue crack growth data is due to material inhomogeneity. The material resistance to fatigue crack growth is modelled as a spatial stochastic process, which varies randomly along the crack path. We developed the GUI program to estimate the probability distribution and reliability using the non-Gaussian stochastic process method. This program can be used for the reliability assessment.