• Title/Summary/Keyword: 균열저항성

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Deep Learning-based Pixel-level Concrete Wall Crack Detection Method (딥러닝 기반 픽셀 단위 콘크리트 벽체 균열 검출 방법)

  • Kang, Kyung-Su;Ryu, Han-Guk
    • Journal of the Korea Institute of Building Construction
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    • v.23 no.2
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    • pp.197-207
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    • 2023
  • Concrete is a widely used material due to its excellent compressive strength and durability. However, depending on the surrounding environment and the characteristics of the materials used in the construction, various defects may occur, such as cracks on the surface and subsidence of the structure. The detects on the surface of the concrete structure occur after completion or over time. Neglecting these cracks may lead to severe structural damage, necessitating regular safety inspections. Traditional visual inspections of concrete walls are labor-intensive and expensive. This research presents a deep learning-based semantic segmentation model designed to detect cracks in concrete walls. The model addresses surface defects that arise from aging, and an image augmentation technique is employed to enhance feature extraction and generalization performance. A dataset for semantic segmentation was created by combining publicly available and self-generated datasets, and notable semantic segmentation models were evaluated and tested. The model, specifically trained for concrete wall fracture detection, achieved an extraction performance of 81.4%. Moreover, a 3% performance improvement was observed when applying the developed augmentation technique.

Reliability Assessment of Fatigue Crack Propagation using Response Surface Method (응답면기법을 활용한 피로균열진전 신뢰성 평가)

  • Cho, Tae Jun;Kim, Lee Hyeon;Kyung, Kab Soo;Choi, Eun Soo
    • Journal of Korean Society of Steel Construction
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    • v.20 no.6
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    • pp.723-730
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    • 2008
  • Due to the higher ratio of live load to total loads of railway bridges, the accumulated damage by cyclic fatigue is significant. Moreover, it is highly possible that the initiated crack grows faster than that of highway bridges. Therefore, it is strongly needed to assess the safety for the accumulated damage analytically. The initiation and growth of fatigue-crack are related with the stress range, number of cycles, and the stiffness of the structural system. The stiffness of the structural system includes uncertainties of the planning, design, construction and maintenance, which varies as time goes. In this study, the authors developed the design and risk assessment techniques based on the reliability theories considering the uncertainties in load and resistance. For the probabilistic risk assessment of crack growth and the remaining life of the structures by the cyclic load of railway and subway bridges, response surface method (RSM) combined with first order second moment method were used. For composing limit state function, the stress range, stress intensity factor and the remaining life were selected as input important random variables to the RSM program. The probabilities of failure and the reliability indices of fatigue life for the considered specimen under cyclic loads were evaluated and discussed.

A Study on the Strength and Drying Shrinkage Crack Control Characteristics of Polypropylene Fiber Reinforced Concrete (폴리프로필렌 섬유보강 콘크리트의 강도 및 건조수축균열 제어특성 연구)

  • 오병환;이명규;유성원;백상현
    • Magazine of the Korea Concrete Institute
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    • v.8 no.6
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    • pp.151-161
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    • 1996
  • Recently, polypropylene fiber reinforced mortar and concrete as civil and architectural materials have been used in major countries in the world. Polypropylene fiber reinforced concrete has many advantages in terms of economical aspect, chemical stability and durability. It has been reported that polypropylene fiber can control restrained tensile stresses and cracks and increase toughness, resistance to impact, corrosion, fatigue and durability. The purpose of the present study is, therefore, to investigate the strength as well as many mechanical characteristics including toughness and shrinkage control properties. A specially devjsed shrinkage test has been applied to measure the crack control characteristics of polypropylene fiber reinforced concrete. The present study indicates that the polypropylene fiber reinforced concrete curbs greatly the crack occurrence due to shrinkage and enhances toughness resistance. The present study provides a firm base for the efficient use of polypropylene fiber reinforced concrete in actual construction such as pavements and slab structures.

Evaluation of R-curve Behavior Analysis and Machinability of $Si_3N_4-hBN$ Machinable Ceramics ($Si_3N_4-hBN$ 머시너블 세라믹의 R-curve 거동분석과 가공성 평가)

  • 장성민;조명우;조원승;이재형
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.1
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    • pp.61-70
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    • 2004
  • Generally, ceramics are very difficult-to-cut materials because of its high strength and hardness. The machining process of ceramics can be characterized by cracking and brittle fracture. In the machining of ceramics, edge chipping and crack propagation are the principal reasons to cause surface integrity deterioration. Such phenomenon can cause not only poor dimensional and geometric accuracy, but also possible failure of the ceramic parts. Ceramics can be machined with traditional method such as grinding and polishing. However, such processes are generally cost-expensive and have low material removal rate. Thus, in this paper, to overcome these problems. BN powder, which gives good cutting property, is added for the fabrication of machinable ceramics by volume of 5,10,15,20,25 and 30%. And, mechanical properties, R-curve behavior and machining tests are carried out to evaluate the machining properties of the manufactured machinable ceramics.

Development of Fracture Toughness Evaluation Method for Composite Materials by Non-Destructive Testing Method (비파괴검사법을 이용한 복합재료의 파괴인성 평가법 개발)

  • Lee, Y.T.;Kim, K.S.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.18 no.4
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    • pp.278-291
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    • 1998
  • Fracture process of continuous fiber reinforced composites is very complex because various fracture mechanisms such as matrix cracking, debonding, delamination and fiber breaking occur simultaneously during crack growth. If fibers cause crack bridging during crack growth, the stable crack growth and unstable crack growth appear repeatedly. Therefore, it is very difficult to exactly determine tile starting point of crack growth and the fracture toughness at the critical crack length in composites. In this research, fracture toughness test for CFRP was accomplished by using acoustic emission(AE) and recording of tile fracture process in real time by video-microscope. The starting point of crack growth, pop-in point and the point of unstable crack growth can be exactly determined. Each fracture mechanism can be classified by analyzing the fracture process through AE and video-microscope. The more reliable method ior the fracture toughness measurement of composite materials was proposed by using the combination of R-curve method, AE and video microscope.

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Evaluation of Sealing Effect on Performance of Overlaid Asphalt Pavement using Accelerated Reflection Cracking Test in Shear Mode (덧씌우기 아스팔트 포장체의 전단반사균옅 모사시험을 이용한 줄눈 실링재의 반사균열 지연효과 비교분석)

  • Choi, Dong-Chon;Li, Xiang-Fan;Lee, Young-Gwan;Kim, Kwang-Woo
    • International Journal of Highway Engineering
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    • v.5 no.3 s.17
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    • pp.1-9
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    • 2003
  • This study was performed to evaluate the effect of various joint sealant on reducing the reflection cracking of asphalt concrete overlay on cement concrete pavement. The test method used was an accelerated reflection cracking test in shear mode, which was developed for evaluation of reflection cracking resistance of overlaid asphalt concrete in laboratory. The test results showed that use of joint sealants resulted in a significant reduction of reflection cracking. When sealant E was used, the fatigue life was the highest, with relatively larger horizontal deformation. When Sealant B was used, the dynamic stability was the highest with the smallest horizontal deformation. In general, the greater the tensile strength of sealant, the better the crack resistance of the mixture.

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Reliability Analysis of Steel Fiber Reinforced Concrete Continuous Beams (강섬유 보강 철근콘크리트 연속보의 신뢰성 해석)

  • Yoo Han-Shin;Jang Hwa-Sup;Kwak Kae-Hwan
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.17 no.4
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    • pp.443-449
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    • 2004
  • Methods for mixing variable types of steel fibers have been developed recently to suppress outbreak of crack or to control the width of crack and improve the load resistible capacity at the same time. On the other hand, uncertainty by complex nature of destruction dynamics of steel fiber reinforced concrete(SFRC) is included. In this study, analysis of reliance considering uncertainty of SFRC beam is done. For this, intensity limit state model was proposed. Moreover, characteristic values about almost every kinds of probability variables were collected and presented according to home and foreign references. Process of improving uncertainty from the result of experiments by Bayseian updating method is also proposed on the purpose of offering better statistical characteristic values with more data in the new future. Fatigue fracture probability equation is proposed and needed statistical characteristic values were presented to analyze fatigue reliance

Self-Diagnosis Properties of Fracture in Reinforced Concrete Intermixed with Conductive Materials (전도성 재료 혼입 철근콘크리트 구조체의 파괴예측 자기진단 특성)

  • Park, Seok-Kyun;Cho, Sung-Dong
    • Journal of the Korea Concrete Institute
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    • v.20 no.3
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    • pp.369-374
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    • 2008
  • Two types of conductive materials are selected and their applicable properties are investigated so as to give the capability of self-diagnosis of fracture in composite mortar, concrete and reinforced concrete. In this study, for giving selfdiagnosis capability, the powder of cokes and milled carbon fiber as conductive materials are selected and intermixed with mortar, concrete and reinforced concrete. After examining change in the value of electric resistance before and after the occurrence of cracks at each flexural load-stage in composite mortar, concrete or reinforced concrete, the relationships of each factors (electric resistance, crack and flexural load) are analyzed. As the results, it can be recognized that conductive materials with powder of cokes and milled carbon fiber can be applied for self-diagnosis of flexural fracture in composite mortar, concrete and reinforced concrete specimen.

Efficiency of Retarding Reflection Crack in Reinforced-and-Modified Asphalt Pavement Overlay (개질재.보강재를 이용한 덧씌우기 아스팔트 포장의 반사균열 지연 효과)

  • Kim, Kwang-Woo;Doh, Young-Soo;Lim, Sung-Bin;Rhee, Suk-Keun;Eum, Joo-Yong
    • International Journal of Highway Engineering
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    • v.1 no.1
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    • pp.85-96
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    • 1999
  • This study was performed to evaluate performance of polymer-modified asphalt mixtures and specially designed reinforcement techniques against reflection cracking of the asphalt pavement overlay. Selected polymers were used for asphalt modification and polyester fiber, a polypropylene film (vinyl) and a grid were used for mixture reinforcement. Using the asphalt mixture with optimum asphalt content, a slab was made and cut into two pieces of specimen. A layer of grid or vinyl was placed at the bottom of specimen to strengthen the pavement layer against crack. A repeated loading was applied to the asphalt mixture specimen which is Placed on a cement concrete with a pseudo-crack. Crack propagation under repeated loading was monitored and effectiveness of the devised crack retarding techniques was evaluated. From the test results. a significant retardation of mode I crack progress was monitored from some of the modified and reinforced asphalt mixtures.

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Bond, Flexural Properties and Control of Plastic Shrinkage Cracking of Crimped type Synthetic Fiber Reinforced Cement Based Composites (Crimped Type 합성섬유로 보강된 시멘트 복합재료의 부착, 휨 및 소성수축균열제어 특성)

  • Won, Jong Pil;Park, Chan Gi;Lim, Dong Hee;Back, Chul Woo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.6A
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    • pp.1033-1039
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    • 2006
  • The purpose of this study are to evaluated bond, flexural properties and control of plastic shrinkage cracking of crimped type synthetic fiber with amplitude 6 mm and height 1.8 mm reinforced cement based composites. Bond and flexural test were conducted in accordance with the JCI-SF 8 and JCI SF-4 standard, respectively. The plastic shrinkage cracking test was conducted for evaluating the effect of fiber in reducing shrinkage cracking in cement based composites. Test results indicated that the crimped typel synthetic fibers performed significantly better than the straight type fiber in terms of interface toughness and pullout load and the crimped type synthetic fibers improved the flexural toughness of concrete. Also, the increasing the crimped type synthetic fiber volume fraction from 0.00% to 1.00% improved the plastic shrinkage cracking resistance. Specially, the effect of control of plastic shrinkage cracking is excellent at the more than 0.5% fibre volume fraction.