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굴패각을 해안/해양 구조물 콘크리트용 굵은 골재로 활용을 위한 기초 연구
강충현,홍성남,서승철,이우동 (사)한국연안방재학회 2023 한국연안방재학회지 Vol.10 No.2
This study uses oyster shells as an aggregate substitute for marine concrete structures. The initial strength of concrete according to the proper particle size composition of the crushed oyster shell was experimentally analyzed. The particle size of the crushed oyster shell obtained through the shredder is out of the range of general aggregates' standard particle size curve because the ratio of 5 mm or less exceeds 50%. It was confirmed that if less than 5 mm was left abroad, it was within the range of the standard particle size curve, and only these were applied as thick aggregate substitutes. The crushed oyster shells impair workability due to their relatively high absorption rate. This study attempted to overcome poor workability by using two methods: using the crushed oyster shells in a saturated-surface-dry (SSD) state and adding an air entraining agent (AE). The SSD case showed that the slump increased, but the strength decreased by about 40%. The AE added case showed a slight decrease in strength while the slump more than doubled.
강충현,허정원,박인준,황경민,장정범 한국구조물진단유지관리공학회 2018 한국구조물진단유지관리공학회 논문집 Vol.22 No.5
최근 발생한 지진들로 인해 한국도 지진 안전지대가 아니라는 인식이 확산되고 있다. 이에 사회 기반시설물에 대한 다각도의 내진 안전성 검토가 수행되고 있다. 전력구는 대표적인 송전시설물의 하나로 땅 속에 묻혀있는 지중 구조물이 갖는 특성으로 인해 구조물 자체의 관성, 내하력 뿐만 아니라 주변부의 지반특성을 함께 고려해야만 한다. 이를 위해서는 지반과의 상호작용을 고려할 수 있는 엄밀한 수치해석이 요구되나, 많은 비용과 시간이 요구되는 구조물-지반 상호작용해석을 모든 전력구에 적용하기엔 무리가 따른다. 본 연구에서는 지반특성과 관련된 변수를 포함하는 주요 설계변수를 독립변수로 하고 내진성능에 대한 안전율을 종속변수로 하는 직접적인 상관관계 분석을 통하여 비용이 큰 수치해석을 배제하면서도 내진안전율이 낮은 취약 전력구를 선별할 수 있는 방안을 제시하였다. 높은 상관성을 보이는 토피고와 철근량을 주요 독립변수로 설정하고 종속변수인 내진안전율과의 분포를 바탕으로 경계방정식을 도출하였다. 이를 이용하여 지진취약 전력구를 수치 해석과정 없이 선별하는 방안을 제시하였다. 대상으로 한 108개의 전력구 중 30%가 지진취약 전력구로 선별되었으며, 선별된 전력구의 내진 안전율 확인을 통해 타당한 선별 방안임을 확인하였다. 제안 기법은 상대적으로 매우 단순하며 추가적인 데이터에 적용하기 쉽고 확장이 용이하다. Due to recent earthquakes, there is a growing awareness that Korea is not a safe zone for earthquakes any more. Therefore, the review of various aspects of the seismic safety of the infrastructures are being carried out. Because of the characteristics of the underground structure buried in the ground, the electric power utility tunnels must be considered not only for the inertia and load capacity of the structure itself but also the characteristics of the surrounding soils. An extensive and accurate numerical analysis is inevitably required in order to consider the interaction with the ground, but it is difficult to apply the soil-structure interaction analyses, which generally requires high cost and extensive time, to all electric power utility tunnel structures. In this study, the major design variables including soil characteristics are considered as independent variables, and the seismic safety factor, which is the result of the numerical analysis, is considered as a dependent variable. Thus, a method is proposed to select vulnerable electric power utility tunnels with low seismic safety factor while excluding costly and time-consuming numerical analyses through the direct correlation analysis between independent and dependent variables. Equations of boundary limits were derived based on the distribution of the seismic safety factor and the cover depth and rebar amounts with high correlation relationship. Consequently, a very efficient and simple approach is proposed to select vulnerable electric power utility tunnels without intensive numerical analyses. Among the 108 electric power utility tunnels that were investigated in this paper, 30% were screened as fragile structures, and it is confirmed that the screening method is valid by checking the safety factors of the fragile structure. The approach is relatively very simple to use and easy to expand, and can be conveniently applied to additional data to be obtained in the future.
콘크리트 구조물의 균열 탐지를 위한 최적의 AE센서 위치 결정
강충현 ( Kang Choong Hyun ),허정원 ( Huh Jung Won ),김태완 ( Kim Tae Wan ) 한국구조물진단유지관리공학회 2018 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.22 No.2
Acoustic Emission (AE) technique applied to detect the crack occurrence of the actual beam element. An optimum position for a limited number of AE transducer was considered to accurately detect the location of the cracks in the three-dimensional space. Six AE transducer was used to detect cracks in the L400mm×H200mm×T100mm region, and several position combinations were applied. Considerable six position combinations were selected, and the weak or incorrect position detection was investigated. The optimum position applied to the experiment for actual beam element and the detected crack position was compared with the visual inspection location. A reliable crack position detecting was confirmed for loadings.