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RISS 인기검색어
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- 저자 : 이종섭(Lee Jong-Sub) (검색결과 224 건)
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비파괴 시험기법을 이용한 록볼트의 건전도 평가(I) -수치해석 및 실험적 적용성 평가-
이종섭,이용준,엄태원,한신인,이인모,Lee, Jong-Sub,Lee, Yong-Jun,Eom, Tae-Won,Han, Shin-In,Lee, In-Mo 한국터널지하공간학회 2006 터널기술 Vol.8 No.1
The purpose of this study is to describe the Non-Destructive Testing(NDT) of the rockbolt and investigate the applicability of the NDT methods to estimate the integrity of the rockbolt. To examine the rockbolt integrity including rockbolt itself and grouting material, two methods are adopted: numerical and experimental methods. In the numerical method, the numerical code DISPERSE is used to analyze the dispersion of the rockbolt. The dispersion curve shows the effects of the thickness and stiffness of grouted materials on the embedded rockbolt. Therefore, the optimal frequency for the integrity test of the rockbolt is obtained: 20~120kHz in L(1,0) mode. In the experimental methods, destructive and non-destructive tests are carried out in a laboratory. In the non-destructive test, the low frequency mode generated by an impact and t he high frequency mode generated by an ultrasonic transducer seem to characterize the rockbolt condition readily. The experimental results show that the guided waves attenuate more significantly when the stiffness of the grouted material increases and/or the zone of the defect increases. Meanwhile, the ultimate capacity of rockbolt was evaluated through the pull-out tests and is compared to the NDT results. This study demonstrates that the NDT is a valuable tool for the rockbolt integrity evaluation.
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표면파에 대한 웨이블렛 변환을 이용한 모형 암반의 위상속도 예측
이종섭,엄현석,김동현,이인모,Lee, Jong-Sub,Ohm, Hyon-Sohk,Kim, Dong-Hyun,Lee, In-Mo 한국터널지하공간학회 2008 한국터널지하공간학회논문집 Vol.10 No.1
터널 막장 전방의 암반 물성 변화의 예측은 터널 시공 시 붕괴를 막을 수 있는 중요한 요소이다. 본 연구에서는 표면파에 대한 웨이블렛 변환을 이용한 모형 암반의 위상속도를 예측하는 비파괴 시험법을 제안함으로써 터널 막장 전방의 암반 물성 변화를 예측하고자 한다. 실내 실험에서는 암반을 모사하기 위하여 강도가 각각 틀린 두 층으로 이루어진 석고 모형을 사용하였다. 가진윈은 진동 발생 가능한 주파수 대역이 150 Hz에서 5 kHz인 액츄에이터를 사용하였으며, 감지기는 두 개의 가속도계가 사용되었다. 분산곡선을 계산하기 위하여 웨이블렛 변환 해석을 수행하였다. 실내 실험 결과, 근접장 효과를 없애기 위한 최소 감지기 간격이 탐측 가능 깊이의 3배 이상으로 나타났다. 정규 분포 곡선에 기초한 가중치를 이용한 간단한 역산을 제안하였고, 파장 반영계수가 0.2일 때 예측치와 실측치가 잘 일치하였다. 표면파의 전파 깊이는 파장의 $0.42{\sim}0.63$배로 나타났으며, 분산곡선에서 파장에 따라 위상속도가 변하는 구간이 역산을 통해 계산된 구간과 잘 일치하였다. 표면파에 대한 웨이블렛 변환을 이용한 위상속도의 예측은 기존의 표면파 시험법에 비해 실험 구성 및 실험 방법, 역산과정이 간단하므로 터널 막장 전방의 암반 물성 변화를 예측하는데 효율적인 적용이 가능할 것으로 판단된다. Prediction of ground condition ahead of tunnel face might be the most important factor to prevent collapse during tunnel excavation. In this study, a non-destructive method to evaluate the phase velocity in model rock mass using wavelet transform of surface wave was proposed aiming at ground condition assessment ahead of tunnel face. Model tests using gypsum as a rocklike material composed of two layers were performed. A Piezoelectric actuator with frequencies ranging from 150 Hz to 5 kHz was selected as a harmonic source. The acceleration history was measured with two accelerometers. Wavelet transform analysis was used to obtain the dispersion curves from the measured data. The experimental results showed that the near-field effects can be neglected if the distance between two receivers is chosen to be three times the wavelength. A simple inversion method using weighted factor based on the normal distribution was proposed. The inversion results showed that the predicted phase velocity agreed reasonably well with the measured one when the wavelength influence factor was 0.2. The depth of propagation of surface wave was from 0.42 to 0.63 times the wavelength. The range of wavelength varying with phase velocity in dispersion curve matched well with that estimated by inversion technique.
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모바일 클라우드 환경에서 비즈니스 프로세스를 위한 XMDR-DAI를 이용한 소셜 기반의 협업 시스템
이종섭,문석재,Lee, Jong-Sub,Moon, Seok-Jae 한국정보통신학회 2015 한국정보통신학회논문지 Vol.19 No.10
In this paper, we propose a social-based collaboration systems for business process management in the mobile cloud. This XMDR-DAI is to provide services for data sharing and exchange between local systems that operate independently in a cloud environment, take charge of a social-based collaborative business process management. Social-based collaborative business processes are handled in a collision among a structure such as unit conversion, meaning conflict, and the schema mapping data resulting from the inner query. The conflict was resolved by mapping process which takes in each XMDR-DAI.
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현장타설말뚝의 네킹 결함 평가를 위한 전자기파의 적용성 연구
이종섭,송정욱,유정동,Lee, Jong-Sub,Song, Jung Wook,Yu, Jung-Doung 한국지반공학회 2018 한국지반공학회논문집 Vol.34 No.4
The objective of this study is to demonstrate the suitability of electromagnetic waves for evaluating necking defects in bored piles using electromagnetic waves. Experiments are conducted with small-scaled defective model pile with diameter of 150 mm and length of 270 mm. Two necking defects are generated at the upper and lower positions on two different sides of the model pile, respectively. The other two necking defects are generated at the upper and lower positions on the same side of the model pile. Electrical wires are installed alongside the stainless steel wire of a steel cage to configure a two-conductor transmission line. A time-domain reflectometer is used to generate and defect electromagnetic waves. The experimental results show that electromagnetic waves are reflected at the necking defects and the end of the model pile. In addition, calculated defect locations are almost the same as actual defect locations. This study demonstrates that electromagnetic waves can be effective tool for evaluating necking defects in bored piles.
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