• 비파괴검사학회지
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• 제31권2호
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• pp.165-173
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• 2011

음향방출기법은 대형 구조물의 구조건전성감시(SHM)를 위한 매우 효율적인 방법이지만, 롤러코스터 지지구조물처럼 승용물의 운행으로 인한 매우 큰 잡음이 일상적으로 존재하는 경우에는 균열 진전 신호만을 분류하여 실시간 감시를 수행하기가 쉽지 않다. 이와 같은 문제의 해결을 위해 본 연구에서는 실시간으로 음원의 분류가 가능한 파형 파라미터 필터링 기법을 제안하였다. 파형 파라미터 필터링 기법은 음향방출 신호의 파형 파라미터를 이용하여 음향방출 히트를 사전에 필터링함으로써 실시간으로 감시하고자 하는 대상 음원만을 분류해내는데 매우 유리한 점이 있다. 다양한 음원에 대해 음향방출 파형 파라미터를 측정 및 분석하여 제안한 기법의 타당성을 살펴보았다. 또한 파형 파라미터 필터가 내장된 음향 방출 시스템을 구축하고 이를 실제 롤러코스터 지지구조물에 적용하여 실시간 균열진전 감시를 위한 가능성을 타진하였다.

• Journal of Electrical Engineering and Technology
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• 제1권3호
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• pp.376-380
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• 2006

Temperature distribution measured to estimate the condition of an electrical apparatus is an absolute reference for the apparatus conditions and the difference between the reference temperature and the current temperature. Because of passive thermography, without the external thermal stimulation, the difference in surface temperature between the region of interest and back ground shows that the results can apply only to the estimation or the monitoring for the condition of loose terminal and the overload pertaining to the rise in temperature. However, a thermal diffusion in the active thermography is differently generated by the structure and condition of the surface and subsurface. This paper presents a nondestructive test using this behavior and deals with the results by heat injection and cooling to the apparatus. The buried discontinuity of subsurface could be detected by these techniques.

• 한국자원공학회지
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• 제55권6호
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• pp.576-587
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• 2018

광물찌꺼기적치장 안전 모니터링을 위한 적치장 안전에 영향을 미치는 요소를 분석하고 이러한 요소를 감시할 수 있는 계측장비를 검토하였다. 또한, 이러한 결과를 국내 광물찌꺼기 적치장(20개소, 18개 광산)에서 발생되는 결함에 대해 적용 가능한 계측장비를 선정하였다. 요소분석은 표면 침식, 파이핑 및 사면 불안정으로 구분하여 평가하였으며, 이를 다시 세분하여 표면 침식은 식생, 복토층 및 광물찌꺼기, 파이핑은 차수층, 우수배제시설 및 침출수, 사면불안정은 사면, 콘크리트 옹벽 및 석축으로 구분하여 결함의 지표 및 계측항목을 설정하였다. 계측은 주로 상시 및 변위계측이 가능한 CCTV의 활용이 높게 평가되었으며, 전기비저항탐사, 음향계측기, 다점온도모니터링, 구조물경사계, 강우량계 및 유량계 등의 활용도가 높은 것으로 평가되었다. 또한, 국내 적치장에서 발생되는 결함에 적용한 결과, 주로 파이핑과 관련된 차수층, 우수배제시설 및 침출수에서 결함이 주로 발견되어 이와 관련된 계측장비의 활용이 높은 것으로 평가되었다.

• Smart Structures and Systems
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• 제14권5호
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• pp.917-942
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• 2014

Multivariate statistics based damage detection algorithms employed in conjunction with novel sensing technologies are attracting more attention for long term Structural Health Monitoring of civil infrastructure. In this study, two practical data driven methods are investigated utilizing strain data captured from a 4-span bridge model by Fiber Bragg Grating (FBG) sensors as part of a bridge health monitoring study. The most common and critical bridge damage scenarios were simulated on the representative bridge model equipped with FBG sensors. A high speed FBG interrogator system is developed by the authors to collect the strain responses under moving vehicle loads using FBG sensors. Two data driven methods, Moving Principal Component Analysis (MPCA) and Moving Cross Correlation Analysis (MCCA), are coded and implemented to handle and process the large amount of data. The efficiency of the SHM system with FBG sensors, MPCA and MCCA methods for detecting and localizing damage is explored with several experiments. Based on the findings presented in this paper, the MPCA and MCCA coupled with FBG sensors can be deemed to deliver promising results to detect both local and global damage implemented on the bridge structure.

• 대한인간공학회지
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• 제29권1호
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• pp.17-24
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• 2010

There has been recent interest in intelligent vehicle technologies, such as advanced driver assistance systems (ADASs) or in-vehicle information systems (IVISs) that offer a significant enhancement of safety and convenience to drivers and passengers. However, unsuitable design of HMI (Human Machine Interface) must increase driver distraction and workload, which in turn increase the chance of traffic accidents. Distraction in particular often occurs under a heavy driving workload due to multitasking with various electronic devices like a cell phone or a navigation system while driving. According to the 2005 road traffic accidents in Korea report published by the ROad Traffic Authority (ROTA), more than 60% of the traffic accidents are related to driver error caused by distraction. This paper suggests the structure of vehicle environment for real-time driving behavior monitoring system while driving which is can be used the driver workload management systems (DWMS). On-road experiment results showed the feasibility of the suggested vehicle environment for driving behavior monitoring system.

• 한국구조물진단유지관리공학회 논문집
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• 제12권3호
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• pp.175-182
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• 2008

본 논문에서는 최근 유지관리분야에서 중요한 분야로 대두되고 있는 대형구조물의 모니터링에 대한 연구 및 고찰을 바탕으로 대형 구조물의 계측데이터를 이용한 확률적 안전도분석에 대한 평가 모형을 제안하였다. 사장교의 계측 데이터를 이용하여 활하중에 대한 모델을 산정하고, 요소신뢰성 및 체계신뢰성 기법을 통하여 사장교의 실질적인 확률적 안전도를 평가하였다. 사장교의 체계신뢰성은 케이블, 보강형, 주탑의 조합파괴를 포함하는 주파괴경로를 찾아낼 수 있는 부분 ETA(Event Tree Analysis) 모델을 이용하여 산정하였으며 이는 기존 안전도 분석방법과 비교하였을 때 구조물의 여용성을 충분히 반영하는 데 상당히 합리적이며 실제적인 결과를 보여주는 실용적인 방법으로 판단된다.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.3068-3084
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• 2021

Investigations of large commercial aircraft impact effect on nuclear power plant (NPP) buildings have been drawing extensive attentions, particularly after the 9/11 event, and this paper aims to experimentally assess the damage and vibrations of NPP buildings subjected to aircraft crash. In present Part I, two shots of reduce-scaled model test of aircraft impacting on NPP building were carried out. Firstly, the 1:15 aircraft model (weighs 135 kg) and RC NPP model (weighs about 70 t) are designed and prepared. Then, based on the large rocket sled loading test platform, the aircraft models were accelerated to impact perpendicularly on the two sides of NPP model, i.e., containment and auxiliary buildings, with a velocity of about 170 m/s. The strain-time histories of rebars within the impact area and acceleration-time histories of each floor of NPP model are derived from the pre-arranged twenty-one strain gauges and twenty tri-axial accelerometers, and the whole impact processes were recorded by three high-speed cameras. The local penetration and perforation failure modes occurred respectively in the collision scenarios of containment and auxiliary buildings, and some suggestions for the NPP design are given. The maximum acceleration in the 1:15 scaled tests is 1785.73 g, and thus the corresponding maximum resultant acceleration in a prototype impact might be about 119 g, which poses a potential threat to the nuclear equipment. Furthermore, it was found that the nonlinear decrease of vibrations along the height was well reflected by the variations of both the maximum resultant vibrations and Cumulative Absolute Velocity (CAV). The present experimental work on the damage and dynamic responses of NPP structure under aircraft impact is firstly presented, which could provide a benchmark basis for further safety assessments of prototype NPP structure as well as inner systems and components against aircraft crash.

• 한국지반환경공학회 논문집
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• 제21권5호
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• pp.5-11
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• 2020

구조물의 이상징후 판단 및 장단기 안정성, 장래 거동 등의 판단에 다양한 계측결과가 효율적으로 이용되기 위해서는 계측 데이터 내에 포함한 각종 이상치의 판정 및 제거가 필요하다. 본 연구에서는 장기 시계열 데이터에 대한 이상치 평가를 수행하기 위한 통합 이상치 분석 시스템을 개발하였다. 이상치 평가는 시계열 분석법에 의한 단일 데이터셋 대상의 1차 이상치 분석과 합성신호 기반의 다중 데이터셋에 대한 2차 이상치 분석으로 구분하여 단계별로 수행되었다. 통합 이상치 분석 시스템은 구조물에 대한 종합 안전관리 플랫폼과 실시간 연동되어 구조물의 각종 안전성 평가 및 거동 예측 등을 위한 기초자료를 제공할 수 있도록 개발되었다. 현장 적용을 통해 일정 경향을 보이는 동종의 다수 센서들의 합성신호와 개별 데이터셋 간의 상관성이 크게 증가함을 확인할 수 있었으며, 상관성에 대한 가중치 적용을 통해 차별 거동을 보이는 다양한 센서 계측치들도 모두 통합 이상치 분석에 활용될 수 있음을 확인 할 수 있었다.

• Smart Structures and Systems
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• 제33권3호
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• pp.189-199
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• 2024

To properly extract the strain components under varying operational conditions is very important in bridge health monitoring. The abnormal sensor readings can be correctly identified and the expected operational performance of the bridge can be better understood if each strain components can be accurately quantified. In this study, strain components under varying load conditions, i.e., temperature variation and live-load variation are evaluated based on field strain measurements collected from a real concrete box-girder bridge. Temperature-induced strain is mainly regarded as the trend variation along with the ambient temperature, thus a smoothing technique based on the wavelet packet decomposition method is proposed to estimate the temperature-induced strain. However, how to effectively extract the vehicle-induced strain is always troublesome because conventional threshold setting-based methods cease to function: if the threshold is set too large, the minor response will be ignored, and if too small, noise will be introduced. Therefore, an autoencoder framework is proposed to evaluate the vehicle-induced strain. After the elimination of temperature and vehicle-induced strain, the left of which, defined as the model error, is used to assess the operational performance of the bridge. As empirical techniques fail to detect the degraded state of the structure, a clustering technique based on Gaussian Mixture Model is employed to identify the damage occurrence and the validity is verified in a simulation study.

• Wind and Structures
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• 제14권3호
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• pp.253-283
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• 2011

This paper presents the field measurement results of wind effects on a super-tall building (CITIC Plaza, 391 m high) located in Guangzhou. The field data such as wind speed, wind direction and acceleration responses were simultaneously and continuously recorded from the tall building by a wind and vibration monitoring system during two typhoons. The typhoon-generated wind characteristics including turbulence intensity, gust factor, peak factor, turbulence integral length scale and power spectral density of fluctuating wind speed were presented and discussed. The dynamic characteristics of the tall building were determined based on the field measurements and compared with those calculated from a 3D finite element model of the building. The measured natural frequencies of the two fundamental sway modes of the building were found to be larger than those calculated. The damping ratios of the building were evaluated by the random decrement technique, which demonstrated amplitude-dependent characteristics. The field measured acceleration responses were compared with wind tunnel test results, which were found to be consistent with the model test data. Finally, the serviceability performance of the super-tall building was assessed based on the field measurement results.