• 상하수도학회지
• /
• 제31권1호
• /
• pp.21-28
• /
• 2017

This study was performed to propose the sewer defect scoring, and grading protocols for sewer condition assessment. For this, sewer defect scoring methods were comparatively analyzed and reviewed for four international condition assessment protocols, which are established based on WRc manual. As a result, we proposed a new protocol for sewer condition assessment, in which characteristics of sewer pipes are considered by segment. In reference to the PIM-3, the extent of ground subsidence was adopted to be of importance, and renewal scores increased in accordance with weighting of defects causing structural backfill materials. Also, defect grades of 'Hole' were extended to 5 levels of the grading, and 'Surface Damage' was excluded in defect assessment. The addition of 'Buckling' resulted in reduction of weights in 'Surface Damage' and 'Lining Defects'.

• 한국산학기술학회논문지
• /
• 제19권3호
• /
• pp.61-68
• /
• 2018

공동주택 하자는 유지보수에 막대한 비용이 들어가게 되며, 발주자, 시공자 그리고 입주자 등에게 심각한 피해를 입힌다. 이에 따라 하자분쟁을 최소화하고 철저한 품질관리를 통한 체계적이고 효율적인 하자관리를 위한 토대를 마련할 필요가 있다. 본 연구에서는 하자분쟁사례를 활용하여 공동주택의 공종/부위/현상에 따른 하자분류체계를 도출하고, 이를 기반으로 하자유형별 하자위험을 평가할 수 있는 방안을 제시하였다. 이를 위하여 본 논문에서는 경과년수 10년 이상 공동주택 하자분쟁사례 34건, 약 6000여개의 하자항목 자료를 토대로 분석을 실시하였다. 분석 결과를 정리하면, 하자분류체계는 하자 공종, 하자부위 및 하자현상으로 크게 분류한 후 세부적으로 총 157개 항목으로 세분화하였다. 하자분류체계를 토대로 하자 빈도, 하자비용 및 하자위험을 분석한 결과, RC공사 및 마감공사에 하자위험이 상당히 집중되어 있는 것으로 확인되었다. 이에 따라 이러한 하자위험에 대한 하자예방 활동이 우선적으로 고려되어야 할 것으로 판단된다. 본 연구를 토대로 하자위험을 관리할 수 있는 방안에 대한 추가적인 연구가 필요할 것으로 판단된다.

• Journal of Welding and Joining
• /
• 제22권1호
• /
• pp.50-57
• /
• 2004

This paper provides FE and experimental validation of the defect assessment method for strength mismatched welded structures, resulting from the Brite Euram SINTAP (Structural Integrity Assessment Procedures for European Industry) project. This shows that the proposed method is conservative, and that the degree of conservatism is similar to that embedded in the methods for homogeneous structures. It provides confidence in the use of the proposed SINTAP method for assessing defective weld strength mismatched structures.

• 상하수도학회지
• /
• 제30권6호
• /
• pp.623-634
• /
• 2016

Sewer condition assessment involves the determination of defective points and status of aged sewers by a CCTV inspection according to the standard manual. Therefore, it is important to establish a reliable and effective standard manual for identifying the sewer defect. In this study, analytic reviews of the CCTV inspection manuals of the UK, New Zealand, Canada and South Korea were performed in order to compare the defect codes and the protocols of condition assessment. Through this, we also established the standardized method for defect code and revised the calculation method of assigning the condition grade. Analyses of the types and frequencies of sewer defects that obtained by CCTV inspection of 7000 case results, showed that the joint defect and lateral defect were the most frequent defects that occurred in Korea. Some defect codes are found to be modified because those did not occur at all. This study includes a proposed new sewer defect codes based on sewer characteristics.

• Smart Structures and Systems
• /
• 제11권3호
• /
• pp.299-314
• /
• 2013

This paper presents a nonlinear time series analysis technique for evaluating machine defect severity, based on the Recurrence Plot (RP) entropy. The RP entropy is calculated from the probability distribution of the diagonal line length in the recurrence plot, which graphically depicts a system's dynamics and provides a global picture of the autocorrelation in a time series over all available time-scales. Results of experimental studies conducted on a spindle-bearing test bed have demonstrated that, as the working condition of the bearing deteriorates due to the initiation and/or progression of structural damages, the frequency information contained in the vibration signal becomes increasingly complex, leading to the increase of the RP entropy. As a result, RP entropy can serve as an effective indicator for defect severity assessment of rolling bearings.

• 상하수도학회지
• /
• 제27권6호
• /
• pp.731-741
• /
• 2013

CCTV inspection method has been used in Korea for more than 20 years, but there is no proper assessment system for sewer failure severity that considers the domestic circumstances. This study classified the defects caused by the overburden load of reinforced concrete sewer pipes depending on severity and developed defect code by analyzing the domestic CCTV inspection videos. The defect score was assigned to each defect code, and it was classified into 5 grades for the decision-making of repair and rehabilitation. The result of this study is expected to be useful for domestic CCTV inspectors to assess the sewer condition and helpful for managers to make a decision of repair and rehabilitation.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.228-233
• /
• 2004

The length of city gas pipeline is increasing with expansion of natural gas transmission rapidly. A lot of the expense was paid for repair and maintenance with increasing of pipeline length and the cost of repair and maintenance by the corrosion was the highest. It is necessary to evaluate integrity in case of thickness reduction by corrosion. There are a lot of assessment criteria for corrosion defect in foreign countries but they are not suitable for application in the country directly. In this work, we performed the burst test and the finite element analysis for city gas pipeline, KS D3507 and KS D3631 for city gas transmission, and developed the assessment method of corrosion defect, which is suitable for domestic condition.

• 상하수도학회지
• /
• 제27권6호
• /
• pp.787-796
• /
• 2013

Sewer joint-related defect is one of the most common domestic sewer defects along with the lateral pipe problem. However, there are currently no criteria that precisely assess the joint-related sewer defects. Therefore, this study examined the joint-related sewer defects found in domestic circumstances, classified them according to the suggested defect code, and presented the examples of defect pictures. Each defect code was organized as the process of out of pipeline alignment (OPA) which shows the progress in deterioration. Each defect was classified into 5 grades depending on appropriate repair and rehabilitation method. The result of this study is expected to be useful for domestic CCTV inspectors to assess the sewer condition and helpful for managers to make a decision of repair and rehabilitation.

• 대한기계학회논문집
• /
• 제19권3호
• /
• pp.731-740
• /
• 1995

The objective of this paper is to develop defect assessment technology for integrity evaluation of CANDU pressure tubes. In fracture mechanics analysis, three-dimensional and two-dimensional (line-spring model) finite element analyses were performed to obtain the stress intensity factor for axial and circumferential surface cracks. In leak before break (LBB) analysis, heat transfer analyses for through-wall cracks were performed by considering the cooling effect and the LBB application time was computed. It was shown that the analytical results obtained in this study provide less-conservative but accurate solution for defect assessment of CANDU pressure tubes.

• 품질경영학회지
• /
• 제48권4호
• /
• pp.597-608
• /
• 2020

Purpose: The purpose of this paper is to present a probability distribution of the burst pressure of API 5L X65 pipes for the reliability assessment of corroded gas pipelines. Methods: Corrosion is a major cause of weakening the residual strength of the pipe. The mean residual strength on the corrosion defect can be obtained using the burst pressure code. However, in order to obtain the pipe reliability, a probability distribution of the burst pressure should be provided. This study is concerned with estimating the burst pressure distribution using Monte Carlo simulation. A response surface method is employed to represent the distribution parameter as a model of the corrosion defect size. Results: The experimental results suggest that the normal or Weibull distribution should be suitable as the probability distribution of the burst pressure. In particular, it was shown that the probability distribution parameters can be well predicted by using the depth and length of the corrosion defect. Conclusion: Given a corrosion defect on the pipe, its corresponding burst pressure distribution can be provided at instant. Subsequently, a reliability assessment of the pipe is conducted as well.