• Tunnel and Underground Space
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• v.30 no.1
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• pp.1-14
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• 2020

Microseismic monitoring is utilized for the performance verification and safety management of the structure by detecting fine levels of damage. In order to construct a highly reliable microseismic monitoring system, the role of signal conditioner is critical. The signal conditioner helps with accurate data collection and precision control of the device, and performs additional functions such as signal conversion, linearization, and amplification. In this technical report, noise reduction signal conditioner suitable for mining sites was developed and reviewed for the purpose of implementing more precise monitoring by supplementing the previously developed microseismic monitoring system.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.55-55
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• 2023

물 인프라 시설물은 다양한 산업 및 지역 사회에 필요한 물 공급과 이와 관련된 인프라를 제공하는 현대 사회의 중요한 구성 요소 중 하나이다. 이러한 시설이 노후화 되면서 안전과 신뢰성에 대한 우려가 커지면서 과거 건설, 개발 중심에서 유지, 관리 중심으로 패러다임이 변화하고 있다. 이에 물 인프라 시설물의 상태를 정밀하게 조사하고, 정확한 계측하는 기술에 대한 수요가 지속적으로 증가하고 있다. 최근, 드론에 초분광 센서를 탑재하여 초분광 영상을 수집할 수 있는 기술이 개발되고 있으며, 물 인프라 시설물에 대한 원격탐사 및 모니터링이 이러한 수요를 만족시킬 수 있는 유망한 해결책으로 부상하고 있다. 특히, 이러한 초분광 영상 수집 기술을 이용하면 물 인프라 시설물 주변의수심, 수질, 온도 등 환경적 요인 뿐만 아니라 재료에 따른 상태를 파악할 수 있어, 잠재적으로 구조 결함을 감지하는데 필요한 상세한 분광 정보를 수집할 수 있다. 또한, "저수지·댐의 안전관리 및 재해예방에 관한 법률"에서 정기적인 정밀안전진단을 요구하고 있으며, "중대재해처벌법"에 따라 인력중심의 조사, 계측 방식의 어려움이 있는 상황에서 드론 기반의 초분광 원격탐사 기술은 매력적인 선택지이다. 본 연구는 안전과 신뢰성에 대한 우려가 커지고 있는 물 인프라 시설물에서 드론 기반 초분광영상 기술이 제공하는 새로운 해결책에 대한 연구로, "저수지·댐 안전관리 및 재해예방에 관한 법률"에서 제시하는 물 인프라 시설의 정기적인 검사 및 유지보수에 대한 중요성을 더욱 강조하는 것으로, 물 인프라 시설물을 정확하게 모니터링하고 조사, 계측하는 능력의 중요성을 증가시킬 수 있는 기술이다. 따라서 본 연구에서는 드론 기반의 초분광 영상 수집 기술을 활용하여 물 인프라시설물의 원격탐사 및 모니터링에 대한 적용성을 검토하고자 한다. 이를 통해 드론 기반 초분광영상 기술이 물 인프라 시설물의 조사 및 계측, 유지 보수에 대한 새로운 해결책이 될 수 있는지 검토한다. 또한 이 기술의 잠재적인 이점과 한계를 탐구하고, 정확하고 신뢰성 높은 계측, 조사 기술에 대한 증가하는 수요를 충족시키기 위한 능력을 평가 하고자 한다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.2
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• pp.166-171
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• 2010

Wired monitoring systems have been used for damage detection and dynamic analysis of large structures(bridges, dams, plants, etc.). However, the real-world applications still remain limited, mainly due to time and cost issues inherent to wired systems. In recent years, an increasing number of researchers have adopted WSN(wireless sensor network) technologies to the field of SHM(structural health monitoring). Accurate time synchronization is most critical for the wireless approach to be feasible for SHM purpose, along with sufficient wireless bandwidth and highly precise measuring resolution. To satisfy technical criteria stated above, a wireless vibration monitoring system that uses high-precision MEMS(micro-electro-mechanical system) sensors and A/D convertor is discussed in detail. It was found experimentally that the level of time synchronization fell within $200\;{\mu}sec$.

• Journal of the Korean GEO-environmental Society
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• v.19 no.9
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• pp.13-19
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• 2018

Recently, there have been various problems aroused on the domestic infrastructures as the domestic cities become old. Accordingly, the national concerns grow on the urban railway and the related structures, which brings the national interests are brought on the research on the maintenance and rehabilitation of the old infrastructures. The underground structure of urban railway are checked with the strain gages or fiber brag grating (FBG) sensors on the railway. However, these methods are known to have resolution limitations on the investigations of the specified abnormal section. Therefore, the applicability of the Brillouin Optical Correlation Domain Analysis (BOCDA) based distributed fiber optic sensor system on the railway was evaluated in this study. The constructed BOCDA fiber optic sensor system shows high resolution of 10, 20, 50, 100 cm and capability of continuous monitoring on overall or specified section within 2 km range. The applicability evaluation was performed on the 250 m distribution of fiber optic sensors abandoned railway for continuous monitoring. The applicability of the system on the specified area was evaluated with wheel load testing. As a result, data loss tends to increase with the reduction of spatial resolution from 1.0 m to 0.1 m. Even though the measuring speed is reduced with lower spatial resolution, data accuracy increases on the location and deformation. The system can be applicable to various structures if the proper distribution method is invented later.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.67-74
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• 2023

A large number of concrete structures are built and used around the world. To ensure their safe and continuous use, these structures require constant inspection and maintenance. While man-powered inspection and maintenance techniques are efficient, they can only provide intermittent status checks at the time of on-site inspection. Therefore, there is a growing need for a system that can continuously monitor the condition of the structure. A study was conducted to detect cracks and damage by installing a conductive coating on the surface of a concrete structure. A parallel resistance pattern that can monitor the occurrence and progression of cracks was developed by reflecting the structural characteristics of concrete structure. An empirical study was conducted to veryfy the application of the proposed method. The crack detection pattern was installed on the reinforced concrete beams, and the crack monitoring method was verified through applying a load on the beams.

• Journal of the Korean Geotechnical Society
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• v.39 no.9
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• pp.51-61
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• 2023

The study aims to select an indicator that can monitor the piping stability of the foundation of a weir structure and suggest a piping stability monitoring method using the selected indicator. Based on the results from previous studies and the results of numerical seepage analysis, the change in pore water pressure in the foundation ground of the weir was selected as an indicator for piping monitoring. Considering the state in which the pore water pressure gauges are installed in operating weirs, seepage analyses were performed according to various upstream water level conditions for each case where one or two gauges were installed at the bottom of the weir. A piping monitoring method was presented based on the analysis results for each of these cases. In addition, the proposed monitoring method was shown to be effective by providing an example of a trial application to an operating weir.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.3
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• pp.42-48
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• 2016

Extensive research effort has been made during the last decade to utilize wireless smart sensors for evaluating and monitoring structural integrity of civil engineering structures. The wireless smart sensor commonly has sensing and embedded computation capabilities as well as wireless communication that provide strong potential to overcome shortcomings of traditional wired sensor systems such as high equipment and installation cost. However, sensor malfunctioning particularly in case of long-term monitoring and unreliable wireless communication in harsh environment are the critical issues that should be properly tackled for a wider adoption of wireless smart sensors in practice. This study presents a wireless smart sensor network(WSSN) that can estimate unmeasured responses for the purpose of data recovery at unresponsive sensor nodes. A software program that runs on WSSN is developed to estimate the unmeasured responses from the measured using the Kalman filter. The performance of the developed network software is experimentally verified by estimating unmeasured acceleration responses using a simply-supported beam.

• The Journal of the Korea Contents Association
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• v.16 no.3
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• pp.11-21
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• 2016

Recently, structure safety management techniques using cutting-edge technology(Displacement senor, sensor of acceleration) has emerged as an important issue owing to the aging of infrastructure such as bridge and building. In general, the structural monitoring system for structure safety management is based on IT technology and it is expensive to install. In this paper developed an image-based structure dynamic characteristic analysis system prototype to assess the damage of structure in a more cost-effective way than traditional structure health monitoring system. The inspector can take a video of buildings or other structures with digital camera or any other devices that is passible to take video, and then using NCC calculation for image processing technique to get natural frequency. This system is analysis of damage of the structure using a compare between the frequency response ratio and functions when problems are occurs send alarm to administrator. This system is easier to install and remove than previous monitoring sensor in economical way.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.3
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• pp.175-181
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• 2020

For the success of a structural integrity management, it is essential to acquire structural response data at some critical locations with limited number of sensors. In this study, the structural response of numerical model was estimated by data fusion approach based on the Kalman filter known as stochastic recursive filter. Firstly, transient direct analysis was conducted to calculate the acceleration and strain of the numerical standing beam model, then the noise signals were mixed to generate the numerical measurement signals. The acceleration measurement signal was provided to the Kalman filter as an information on the external load, and the displacement measurement, which was transformed from the strain measurement by using strain-displacement conversion relationship, was provided into the Kalman filter as an observation information. Finally, the Kalman filter estimated the displacement by combining both displacements calculated from each numerically measured signal, then the estimated results were compared with the results of the transient direct analysis.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.3
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• pp.211-216
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• 2016

In several industrial fields, epoxy resin is widely used as an adhesive for co-curing and manufacturing various structures. Controlling the manufacturing process is required for ensuring robust bonding performance and the stability of the structures. A fiber optic sensor is suitable for the cure monitoring of epoxy resin owing to the thready shape of the sensor. In this paper, a fiber Bragg grating (FBG) sensor was applied for the cure monitoring of epoxy resin. Based on the experimental results, it was demonstrated that the FBG sensor can monitor the status of epoxy resin curing by measuring the strain caused by volume shrinkage and considering the compensation of temperature. In addition, two types of epoxy resin were used for the cure-monitoring; moreover, when compared to each other, it was found that the two types of epoxy had different cure-processes in terms of the change of strain during the curing. Therefore, the study proved that the FBG sensor is very profitable for the cure-monitoring of epoxy resin.