• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.36 no.6
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• pp.451-456
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• 2018

UAVs (Unmanned Aerial Vehicles) are widely used for maintenance and monitoring of facilities. It is necessary to acquire a high-resolution image for evaluating the appearance state of the facility in safety inspection. In addition, it is essential to acquire the video data in order to acquire data over a wide area rapidly. In general, since video data does not include position information, it is difficult to analyze the actual size of the inspection object quantitatively. In this study, we evaluated the utilization of 3D point cloud data of bridges using a matching between video frames and reference photos. The drones were used to acquire video and photographs. And exterior orientations of the video frames were generated through feature point matching with reference photos. Experimental results showed that the accuracy of the video frame data is similar to that of the reference photos. Furthermore, the point cloud data generated by using video frames represented the shape and size of bridges with usable accuracy. If the stability of the product is verified through the matching test of various conditions in the future, it is expected that the video-based facility modeling and inspection will be effectively conducted.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.8
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• pp.841-846
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• 2014

FBG sensors are mainly used to measure deformation of structures such as tunnels, bridges and ships. In this paper, an interrogator of FBG sensors is developed and implemented to measure the status of structures. A developed interrogator includes CAN wired and Zigbee wireless communication for remote monitoring. Strain of structure is measured using shift of wavelength of reflected light from FBG sensor. A digital signal controller is used to process signals of a FBG sensor and transmit data for remote monitoring. As a result of experiment, developed interrogator is effective to measure deformation of structures.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.553-562
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• 2006

본 논문에서는 한국과 일본에 위치한 여러 연구기관들 사이에서 수행된 온라인 네트워크 유사동적 실험 곁과에 대해 나타내었다. 예제 구조물로는 4경간 연속의 면진 교량을 이용하였다. 실험 장비를 보유하고 있는 두 연구기관에서 면진 장치의 비선형 거동에 대한 실험을 수행하고 각 실험 결과를 조합하여 전체 구조의 동적 해석을 수행하였다. 본 논문에서는 먼저 인터넷을 이용한 두 가지 데이터 전송기법을 이용하여 두 기법의 효율성을 비교, 분석하였다. 또한 최근 국내에 위치한 두 연구기관 사이에서 수행된 실험 결과에 대해 논의하였다. 본 연구에서는 상대 연구기관의 실험 상황 및 수행된 실험 결과의 효율적인 모니터링을 위하여 웹 기반의 자바 모니터링 시스템을 개발하였다. 마지막으로 유선과 무선 인터넷을 이용한 온라인 실험 기법에 대하여 나타내었다. 그 결과, 온라인 네트워크 실험에 소요된 실험 시간은 데이터 전송 기법과 실험장비에 따라 매 시간 단계의 데이터 전송에 0.2-l5초, 각 연구기관의 유사동적 실험에 1-10초의 시간이 소요되어 매우 큰 폭으로 변화함을 알 수 있었다. 또한 무선 인터넷을 이용한 온라인 실험의 경우, 뛰어난 이동성과 인터넷 보안성 등과 같은 여러 가지 장점을 가지고 있음을 알 수 있었다.

• Journal of Korean Society of Steel Construction
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• v.14 no.5 s.60
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• pp.641-646
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• 2002

A new damage detection technique using static displacement data was developed, in order to assess the structural integrity of bridge structures. In conventional damage assessment techniques using dynamic response, the variation of natural frequencies is intrinsically insensitive to the damage of the bridge: thus, it is usually difficult to obtain them from the measured data. The proposed detection method enables the estimation of the stiffness reduction of bridges using the static displacement data that are measured periodically, without requiring a specific loading test. Devices such as a laser displacement sensor can be used to measure static displacement data due to the dead load of the bridge structure. In this study, structural damage was represented by the reduction in the elastic modulus of the element. The damage factor of the element was introduced to estimate the stiffness reduction of the bridge under consideration. Likewise, the proposed algorithm was verified using various numerical simulations and compared with other damage detection methods. The effects of noise and number of damaged elements on damage detection were also investigated. Results showed that the proposed algorithm efficiently detects damage on the bridge.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.1
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• pp.341-353
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• 2014

In order to deliver a centimeter-level kinematic positioning solution with GPS carrier-phase measurements, it is prerequisite to use correctly resolved integer ambiguities. Based on the mathematical modeling of GPS network with application of its geometrical constraints, this research has investigated an instantaneous ambiguity resolution procedure for the so-called 'integer constrained least-squares' technique which can be effectively implemented in real-time structure monitoring. In this process, algorithms of quality control for the float solutions and hypothesis tests using the constrained baseline for the ambiguity validation are included to enhance reliability of the solutions. The proposed procedure has been implemented by MATLAB, the language of technical computing, and processed field trial data obtained at a cable-stayed bridge to access its real-world applicability. The results are summarized in terms of ambiguity successful rates, impact of the stochastical models, and computation time to demonstrate performance of the instantaneous ambiguity resolution proposed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.5
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• pp.108-122
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• 2001

As bridge design is advancing toward the performance-based design. it becomes increasingly important to monitor and re-evaluate the long-term structural performance of bridges. Such information is essential in developing performance criteria for design. In this research. sensor systems for long-term structural performance monitoring have been installed on two highway bridges. Pre1iminary vibration measurement and data analysis have been performed on these instrumented bridges. On one bridge, ambient vibration data have been collected. based on which natural frequencies and mode shapes have been extracted using various methods and compared with those obtained by the preliminary finite element analysis. On the other bridge, braking and bumping vibration tests have been carried out using a water truck In addition to ambient vibration tests. Natural frequencies and mode shapes have been derived and the results by the breaking and bumping vibration tests have been compared. For the development of a three dimensional baseline finite element model, the new methodology using a neural network is proposed. The proposed one have been verified and applied to develop the baseline model of the bridge.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.5
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• pp.301-308
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• 2021

It is important to develop a digital SOC (Social Overhead Capital) maintenance system for preemptive maintenance in response to the rapid aging of social infrastructures. Abnormal signals induced from structures can be detected quickly and optimal decisions can be made promptly using IoT sensors deployed on the structures. In this study, a digital SOC monitoring system incorporating a multimetric IoT sensor was developed for long-term monitoring, for use in cloud-computing server for automated and powerful data analysis, and for establishing databases to perform : (1) multimetric sensing, (2) long-term operation, and (3) LTE-based direct communication. The developed sensor had three axes of acceleration, and five axes of strain sensing channels for multimetric sensing, and had an event-driven power management system that activated the sensors only when vibration exceeded a predetermined limit, or the timer was triggered. The power management system could reduce power consumption, and an additional solar panel charging could enable long-term operation. Data from the sensors were transmitted to the server in real-time via low-power LTE-CAT M1 communication, which does not require an additional gateway device. Furthermore, the cloud server was developed to receive multi-variable data from the sensor, and perform a displacement fusion algorithm to obtain reference-free structural displacement for ambient structural assessment. The proposed digital SOC system was experimentally validated on a steel railroad and concrete girder bridge.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.303-310
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• 2021

Cracks in bridges are important factors that indicate the condition of bridges and should be monitored periodically. However, a visual inspection conducted by a human expert has problems in cost, time, and reliability. Therefore, in recent years, researches to apply a deep learning model are started to be conducted. Deep learning requires sufficient data on the situations to be predicted, but bridge crack data is relatively difficult to obtain. In particular, it is difficult to collect a large amount of crack data in a specific situation because the shape of bridge cracks may vary depending on the bridge's design, location, and construction method. This study developed a crack detection model that generates and trains insufficient crack data through a Generative Adversarial Network. GAN successfully generated data statistically similar to the given crack data, and accordingly, crack detection was possible with about 3% higher accuracy when using the generated image than when the generated image was not used. This approach is expected to effectively improve the performance of the detection model as it is applied when crack detection on bridges is required, though there is not enough data, also when there is relatively little or much data f or one class.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.2111-2113
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• 2004

대형 조물은 안전관리 시스템의 법제화로 스트레인 게이지, 가속도 센서 등을 이용하여 상시 관리를 의무화 하고 있다. 상시 계측을 위해 유선 센서의 경우 데이터 전송의 신뢰성은 있지만 선로 결선의 문제점 때문에 무선 센서의 적용이 요구된다. 하지만 무선 센서의 경우, 전원공급의 문제를 갖고 있어 장차이 어려운 실정이다. 본 연구에서는 압전체를 이용하여 무선 센서의 전원 공을 위한 에너지 변환 시스템을 제안하였다. 이 시스템은 구조물 내부의 진동을 전기 에너지로 변환, Capacitor에 저장 후, 데이터 전송을 위해 일시에 방출하는 구조이다. 20m의 무선 데이터 통신을 위해 2.43mJ(5V*49mA*10ms)의 전력량이 필요한데, 모의 교량 모델에 시스템을 적용한 결과 2분 30초 동안의 진동 에너지가 2.8mJ의 전기 에너지로 저장되었다. 이 실험 결과를 토대로 무선 센서를 이용한 상시 모니터링이 가능함을 예상할 수 있다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.105-113
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• 2014

Most operating civil structures measure response data continuously by various types of sensors and evaluate their health conditions. Measurement control criteria for such civil structures are usually defined in the first operating stage by experts working at a construction or engineering company. However, a few studies have been carried to examine the adequacy of these measurement control criteria based on the actual measured data. The paper introduces a systematic way of resetting the measurement control criteria for the measured monitoring data based on the statistical aspects of the measured data. The proposed statistical approach has been examined with actually measured time-history data from a bridge structure.