• International Journal of Korean Welding Society
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• 제1권2호
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• pp.30-35
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• 2001

Nowadays, repair welding on in-service natural gas pipeline is a matter of primary concern of gas company. The main purpose of this study is to investigate the effects of welding conditions on the allowable heat input for crack-free welds and welds without burn-through onto in-service natural gas pipeline. First of all, single pass weld bead on plates of the various thickness was deposited to evaluate the penetration of weld metal, the depth of heat affected zone and the hardness of repair weld under various welding conditions. Also, finite element analysis has been conducted to validate experimental results of bead-on plate welds and to develop appropriate model for repair welding. The welding experiments of bead-on-plate weld confirmed the influence of plate thickness, heat input and welding process on safety. And, the finite element model was demonstrated by comparing experimental results. The agreement between the computed and measured values was shown to be generally good. Therefore, It is possible to predict the safety of repair welding under various welding conditions with experimental results and finite element analysis model.

• Journal of Construction Engineering and Project Management
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• 제5권2호
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• pp.44-52
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• 2015

Various approaches have been used in crack preparations and each of the approaches has advantages and disadvantages. Although the routing method has been widely used and seems to be the best approach among the approaches, it is not a complete solution for crack preparation. This paper compares and evaluates a pneumatic crack cleaning device (CCD) developed by Robotics and Intelligent Construction Automation group at Georgia Tech, over existing devices. Surveys were conducted to discover factors that affect the performance of crack/joint preparation work. Then, data for such information were collected via field tests for devices such as router, heat lancer, air blower and CCD. Performed field test results and follow-up interviews demonstrated that the utilization of CCD has potential to offer improvements in productivity, safety, and maintenance cost. An analytic hierarchical procedure (AHP) and economic analyses were conducted. The AHP analysis considered three factors including safety, quality and productivity while the economic analyses examined the alternatives in various ways. The results indicated that the CCD was ranked first and second for the AHP analysis and economic analysis, respectively. In conclusion, the field tests and results revealed that the utilization of CCD achieved satisfactorily in performance, quality, safety and control, and showed that it has high potential in crack cleaning practice.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1997년도 가을 학술발표회 논문집
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• pp.50-54
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• 1997

To trace crack propagation process in cracked structure is very important thing in view of maintenance and repair of the structure. But it is a little troublesome work due to the continuous remesh work, because a new crack tip is formed in each propagation step. It is more difficult if it should be studied in the three dimensional region. By the way, lately the CFG(Cornell Fracture Group) makes the crack propagation analysis in three dimensional problems possible by developing a new code for them. The use of the code will be expected to spread widely. So a brief introduction of the contents of the code via the theorems used and numerical examples is the purpose of this paper.

• 한국구조물진단유지관리공학회 논문집
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• 제2권1호
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• pp.98-107
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• 1998

There are many weld defects such as surface crack, lack of fusion, and imcomplete penetration in the butt joint of the existing steel bridges. The crack-like defects may significantly reduce the fatigue life of the structure. This paper presents the procedure and the results of the fatigue assessment of the butt joints with weld defect in the existing steel girder bridge. The butt joints with imcomple penetration were instrumented with strain gages to determine the stress histogram under normal traffic. Based on the measured stress histogram the crack propagation analyses were performed for the fatigue assesment. By using the suggested procedure and methodology, one can decide the time of periodic inspection and the necessity of repair of the butt joints with serious weld defects in the existing steel bridge.

• Journal of Welding and Joining
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• 제18권2호
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• pp.204-204
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• 2000

There are many weld defects such as surface crack, lack of fusion, and incomplete penetration(IP) in the butt joint weld of the existing steel bridges. The crack-like defects may significantly reduce the life of the structure. This paper presents the procedure and the results of the fatigue life assessment of the butt joints with weld defects in the existing steel girder bridge. The butt joint welds with incomplete penetration were instrumented with strain gages to determine the stress histogram under normal traffic. Based on the measured stress histogram the crack propagation analysis were performed for the fatigue life assessment. By using the suggested procedure and methodology, one can decide the time of periodic inspection and the necessity of repair of the butt joint welds with serious weld defects in the existing steel bridge. (Received October 1, 1999)

• Journal of Welding and Joining
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• 제18권2호
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• pp.77-85
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• 2000

There are many weld defects such as surface crack, lack of fusion, and incomplete penetration (IP) in the butt joint weld of existing steel bridges. The crack-like defects may significantly reduce the fatigue life of the structure. This paper presents the procedure and the results of the fatigue life assessment of the butt joints with weld defects in the existing steel girder bridge. The butt joint welds with incomplete penetration were instrumented with strain gages to determine the stress histogram under normal traffic. Based on the measured stress histogram the crack propagation analysis were performed for the fatigue life assessment. By using the suggested procedure and methodology, one can decide the time of periodic inspection and the necessity of repair of the butt joint welds with serious weld defects in the existing steel bridge.

• 한국터널지하공간학회 논문집
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• 제25권5호
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• pp.345-355
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• 2023

본 연구에서는 교통량과 균열 두 변수에 대한 관계성을 분석하기 위하여 공분산 분석 및 피어슨 상관관계 분석을 수행하였다. 이를 위하여 국도터널 216개소에 대한 정밀안전점검, 정밀안전진단 시행결과 및 교통량을 조사/분석하였다. 분석결과 교통량과 콘크리트 라이닝에 발생하는 균열은 높은 상관성을 보이는 것으로 나타났다. 따라서 균열 보수 등 선제적 유지관리는 교통량을 고려한 계획수립을 수행하는 것이 바람직하다.

• 콘크리트학회논문집
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• 제19권6호
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• pp.707-715
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• 2007

다공질성 특성을 갖는 콘크리트는 충분한 다짐과 양생 조건에서 장수명을 갖으며, 유해 물질의 주요 경로는 공극이다. 그러나 균열이 발생한 콘크리트의 경우, 균열은 염소이온과 같은 유해 물질의 우선적인 침투 경로가 된다. 균열이 염소에 미치는 영향은 균열폭과 균열 깊이의 크기에 의존한다. 본 연구는 미세균열이 콘크리트의 염소이온 침투에 미치는 영향을 다룬 실험적 연구로서, 연구 목적은 균열폭과 균열 깊이 등의 균열 크기 효과가 염소이온에 미치는 영향을 고찰하는 것이다. 균열을 통한 염소이온의 침투를 시각화 하기 위하여, 급속 염소이온 침투 실험인 RCM (rapid chloride migration) 실험을 수행하였다. 균열폭과 균열 깊이는 전자 현미경으로 관찰하였고, 평균적인 균열폭을 산정하기 위하여 균열 개구 변위가 측정되었다. 다양한 균열 크기에 따른 염소이온의 침투 깊이 및 염소이온 확산계수의 변화율로부터 염소이온이 침투되지 않는 균열 깊이 및 이에 대응한 균열폭이 도출되었다.

• 콘크리트학회논문집
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• 제16권5호
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• pp.659-666
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• 2004

본 연구에서는 최근 국내에서 신기술 등으로 인증되어 활용되고 있는 보수재료 공법을 적용한 폭로시험체를 제작한 후, 해양환경 및 일반대기환경 하에서 장기폭로실험에 의한 정량적 폭로실험데이터를 확보함으로서 향후 성능 저하된 철근콘크리트 구조물의 보수재료 공법 성능평가 방법 및 품질관리기준 확립을 위한 기초자료를 제시하고자 하였다. 해양 및 일반대기환경 하에서 폭로재령 18개월까지 폭로실험을 실시한 결과 일부 보수공법에 있어서 표면피복재 및 단면복구재의 미세균열 부풀음, 박리현상과 보수경계부위의 균열 및 보수부위와 비보수부위의 전위차가 다소 발생하고 있는 것으로 나타났으며 향후 폭로시험체의 지속적인 평가 및 파괴에 의한 상세평가를 통하여 정량적인 폭로실험 데이터를 확보함으로서 보수재료 공법의 성능평가방법 및 품질관리기준 확립을 위한 기초 자료를 제시할 수 있을 것으로 판단된다.

• 한국압력기기공학회 논문집
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• 제9권1호
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• pp.56-61
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• 2013

This paper presents the results of integrity assessment for the cracks happened in reactor vessel upper head penetration nozzles. The crack morphology for a boat sample from crack area was analyzed through microscope. The stress condition including weld residual stress around crack was analyzed using finite element analysis. From the results of crack morphology and stress condition, the crack was concluded as primary water stress corrosion cracking. The integrity of the cracked nozzle was assessed by the methodology provided in ASME Section XI. According to the assessment results, the remaining life of the cracked nozzle was 1.43 yrs. and the plant decided to repair it.