• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.891-894
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• 2008

This study was performed to investigate how to design, where to construct, why to degrade, what plan to use systematically the underground structures such as underpass, underground passageways. About 50% of the underground structures are located on Seoul, Kyungi-Do. In design of the underground structures such as underpass, underground passageways, the required conditions are defined. And also in construction stage, the conditions of soil, required structure depth, site characteristics, reasonable construction method, are investigated. In the selection of details for underground structure, the items mainly considered, are the wall and column type, the sidewalk type, anchoring-system type, the water-proofing method, entranc shape. The reason and the adequate measures for the degradation of concrete structure are also investigated. The initial cracking properties due to the thermal characteristic are considered. The state of the art report on the new technologies are reviewed. The recent project for the systematically application to the underground structures is reviewed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.93-101
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• 2022

RC Slab bridges in Korea account for more than 70% of the total bridges for more than 20 years of service. As the number of aging structures increases, the importance of safety diagnosis and maintenance of structures increases. For highway bridges, cracks are a main cause of deck deterioration, which is very closely related to the decrease in bridge durability and service life. In addition, the damage rate of expansion joints and bearings accounts for approximately 73% higher than that of major members. Therefore, this study defined damage scenarios combined with devices damages and deck deterioration. The stress distribution and maximum stress on the deck were then evaluated using design vehicle load and daily temperature gradient for single and combined damage scenarios. Furthermore, this study performed damage-spread analysis and predicted condition ratings according to a deck deterioration model generated from the inspection and diagnosis history data of cracks. The heterogeneous damages combined with the member damages of expansion joints and bearings increased the rate of crack area and damage spread, which accelerated the time to reach the condition rating of C. Therefore, damage to bridge members requires proper and prompt repair and replacement, and otherwise it can cause the damage to bridge deck and the spread of the damage.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.220-227
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• 2021

PCT (Power Cable Tunnel) and UT (Utility Tunnel), which are non-transport underground infrastructures, are mostly RC (Reinforced Concrete) structures, and their durability decreases due to the deterioration caused by carbonation over time. In particular, since the rate of carbonation varies by use and region, a predictive model based on actual carbonation data is required for individual maintenance. In this study, a carbonation prediction model was developed for non-transport underground infrastructures, such as PCT and UT. A carbonation prediction model was developed using multiple regression analysis and deep neural network techniques based on the actual data obtained from a safety inspection. The structures, region, measurement location, construction method, measurement member, and concrete strength were selected as independent variables to determine the dependent variable carbonation rate coefficient in multiple regression analysis. The adjusted coefficient of determination (Ra2) of the multiple regression model was found to be 0.67. The coefficient of determination (R2) of the model for predicting the carbonation of non-transport underground infrastructures using a deep neural network was 0.82, which was superior to the comparative prediction model. These results are expected to help determine the optimal timing for repair on carbonation and preventive maintenance methodology for PCT and UT.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.3
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• pp.1-11
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• 2023

After the collapse of the Seongsu Bridge in the 1990s in Korea, attention was focused on the maintenance of facilities. The government has established various policies since the enactment of the Act in 1995 until recently. In general, safety inspections are performed to evaluate the safety grade of facilities, and facilities are maintained and managed by performing repairs and reinforcements for defects. However, since the budget is limited, it is impossible to carry out repair and reinforcement projects for all defects. It is necessary to prioritize repair and reinforcement measures. Then, the priority index (PI) is presented considering the importance of members, the seriousness of defects, and economic feasibility. In this index, the degree of influence can be adjusted within the range of 50 to 100% according to the expert's subjective judgment, and the same weight is set for some specific members. Also, the effect through repair and reinforcement is not taken into account decisively, and most of them have a limit in which priority is determined by economic feasibility. Therefore, in this study, through several case studies, problems with the priority index were reviewed and an equation was presented to improve them.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.80-86
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• 2019

As computer performance improves, research using deep learning are being actively carried out in various fields. Recently, deep learning technology has been applying to the safety evaluation for structures. In particular, the internal blades of a turbine structure requires experienced experts and considerable time to detect surface damages because of the difficulty of separation of the blades from the structure and the dark environmental condition. This study proposes a Faster R-CNN deep learning model that can detect surface damages on the internal blades, which is one of the primary elements of the turbine structure. The deep learning model was trained using image data with dent and punch damages. The image data was also expanded using image filtering and image data generator techniques. As a result, the deep learning model showed 96.1% accuracy, 95.3% recall, and 96% precision. The value of the recall means that the proposed deep learning model could not detect the blade damages for 4.7%. The performance of the proposed damage detection system can be further improved by collecting and extending damage images in various environments, and finally it can be applicable for turbine engine maintenance.

• Journal of the Korean Institute of Gas
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• v.27 no.4
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• pp.19-26
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• 2023

Earthquakes are one of the most important disasters affecting underground structures. Urban gas underground pipes may cause safety problems of structures in the event of an earthquake. Since Korea began digital observation, the number of earthquakes has been steadily increasing. The seismic design standard for urban gas pipes was established in 2008, but it is difficult to estimate the impact of pipes in the event of an earthquake based on the installation of pipes. In this study, structural analysis was performed on PE (polyethylene pipe) pipes and PLP (polyethylene coated steel pipe) pipes, which are mainly used as buried pipes in Korea, according to environmental and pipe variables in the event of an earthquake. This study sought to find the variables of the most vulnerable buried pipe by modeling pipes through Computer Aided Engineering (CAE) and generating displacement on the ground. Through this study, it was confirmed that the larger the elastic modulus of the soil, the deeper the buried depth, the smaller the tube diameter, and the higher the pressure, the more PLP pipes are affected by earthquakes than PE. Based on these results, the vulnerable points of buried urban gas pipes are inferred and used for special inspections of buried pipes in the event of an earthquake.

• Journal of Korean Society of Steel Construction
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• v.24 no.5
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• pp.595-603
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• 2012

This study applied elastic supports in order to evaluate load carrying capacity using measurement data obtained from load tests actively and utilizing various evaluation methods. In order to confirm the adequacy of structural analysis based on elastic supports and to improve the reliability of experiment results, we conducted a deflection test with flexural beams prepared as overhanging beams and, based on the results, performed precision safety diagnosis for real bridges under public service for improving the load carrying capacity evaluation method for bridges under public service. In the results of the bending test, compared to deflection calculated by the existing method, deflection obtained by applying elastic supports was closer to the actually measured deflection. In the results of evaluating load carrying capacity for a 3 span continuous steel box girder bridge just after its completion, load carrying capacity by elastic supports was smaller by up to 39% than that by the existing method. When the load carrying capacity of bridges is evaluated by the existing method the results vary among engineers due to lack of guidelines for evaluation such as the application of stress modification factor. This study was conducted as an effort to solve this problem through active research.

• Korean Journal of Construction Engineering and Management
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• v.21 no.1
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• pp.87-98
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• 2020

As the construction industry accounts for 28.5% of industrial accidents in Korea and 29.6% of industrial accident deaths in 2017, it is necessary to search for a priority disaster reduction scheme for the construction industry in order to reduce the industrial accident rate. Therefore, this research suggested improvement direction for construction accidents reduction based on factors affecting construction accidents occurring in the construction site by DEMATEL analysis. As a result of the analysis, the 4M factors with the highest Prominence and Relation is 'Management', and the detailed analysis of the 4M factors were Personal characteristics of workers, Defects such as machinery and equipment, Inadequate inspection of machinery and equipment, Insufficient safety management plan, Inappropriate work orders from supervisors and field managers. The analysis results of this research can be used as a basic data for establishing direction of reduction and improvement of construction accidents.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.3
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• pp.687-704
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• 2017

As Korea's industrial competitiveness and technological prowess increase, collaboration and technical exchanges with contracting companies are increasing. In an environment where cooperation with the contracting company is unavoidable ordering companies are also striving to prevent leakage of technologies through various security systems, policy-making and security checks. However, although the contracting companies were assessed to have a high level of security management the leakage of technical datas are steadily increasing. Issues are being raised about the effectiveness of the security management assessment and the actual security management levels. Therefore, this study suggested a security management system model to improve security management efficiency in the general contract structure. To prove this, analyze the efficiency of 36 contractor companies for the technical datas security management system using the DEA model. The results of the analysis are reflected in the assessment results. Lastly, suggestions for improving the effectiveness of the technical datas security system are proposed.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.443-443
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• 2012

최근 지구 온난화 및 기후변화로 인하여 국지적 집중호우에 의한 농지 침수 및 유실 피해가 점차 증가 추세에 있으며 가뭄에 의한 물 부족 현상도 심화되고 있다. 이와 같은 홍수 및 가뭄 피해에 대비하기 위하여 농업용 저수지와 수문 그리고 농수로와 같은 농업수리시설물이 신축 운영되고 있으나 이들 시설물은 비교적 규모가 작은 대신에 그 수가 매우 많고 또한 지역적으로 널리 산재해 있기 때문에 관리자가 이들을 효율적으로 운영하고 관리하는데 한계가 있다는 특징이 있다. 더욱이 이들 시설물은 물과 항상 접하는 철근 콘크리트 구조물로 이루어져 있어서 시간이 경과함에 따라 균열발생과 철근부식과 같은 노후화 현상이 뚜렷하게 진전되어 정기적 안전점검이 필요한 실정이다. 이에 따라 농업수리시설을 보다 체계적으로 관리하고 농업용수를 보다 효율적으로 확보 운영하기 위하여 물관리 자동화 사업이 추진되어 많은 개선이 이루어졌으나 아직까지 현장업무가 관리자의 수작업에 의존하고 있으며 농촌 용수의 정확한 정보가 제때에 제공되지 못하는 등 농업수리시설에 대한 다양한 요구를 충족시키지 못하고 있다. 따라서, 농촌수자원의 효율적 관리를 위하여 농업수리시설 가운데 하나인 농수로의 수위 및 유량 정보를 자동으로 측정하며 농업수리시설물의 상태 정보를 입력하고 관리할 수 있는 모바일 App을 개발하였다. 안드로이드 OS 기반의 스마트폰을 활용하였으며 여기에는 시설물 고유정보가 포함된 QR코드 및 Active 태그를 통하여 시설물의 상태정보를 원격에 있는 서버 컴퓨터로 전송할 수 있는 원거리 무선통신 모듈이 구비되어 있다. 특히, 농업수리시설물 관리 어플리케이션은 현장관리자가 기존에 수기방식으로 시설물을 관리해 오던 것을 휴대단말 상에서 보다 효율적으로 관리를 함으로써 시설물 유지관리 업무의 효율성을 향상시키는 특징이 있다.