• Title/Summary/Keyword: MONITORING TECHNIQUE

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Observation and Analysis of Shoreline Changes Using the Remote Unmanned Automatic Camera Monitoring System (원격 무인 자동 영상 관측 시스템을 활용한 해안선 변화 관측 및 분석)

  • 김태림
    • Korean Journal of Remote Sensing
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    • v.19 no.2
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    • pp.99-106
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    • 2003
  • The shoreline changes were observed and analysed using the video image by a remote unmanned automatic camera monitoring system installed at Haeundae beach of Busan City. In order to analyse quantitatively the shoreline changes caused by waves and tides, the image averaging technique and the rectification technique for obliquely acquired image were applied to the video image during the typhoon Bart in September, 1999. The results showed that the camera monitoring system can be used as a very cost effective and efficient tool for monitoring shorelines which change continuously due to waves and tides.

A Study on Application & Evaluation of Riverbed Techniques for the Formation of Hyporheic Zone (하상간극수역의 형성을 위한 하상공법의 적용과 평가)

  • Choi, Jungkwon
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.16 no.6
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    • pp.119-133
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    • 2013
  • The purpose of this study is to develop riverbed techniques to activating ecological function of hyporheic zone. Hyporheic zone maybe simply defined as an active eco-tone between surface water and groundwater, which facilitates to exchange water, nutrients and aquatic habitat occur in response to variation in discharge and bed geomorphology. The aim of this study is to evaluate the effectiveness of an applied riverbed technique for two years since its installation in the hyporheic zone. The experimental riverbed technique has been implemented on Anyang stream penetrating Anyang city in Gyunggi province. The dimension of the installed structure is 5.0 m in width, 46 m in length. Bottom layer is filled with rip-rap covered with gabion. After the implementation of the technique, the study conducts follow-up monitoring in two years of between 2011 and 2012. The results of follow-up monitoring for two years are as follows:1) In Hydro geomorphic process, the riverbed technique maintains hydraulic stability despite of several flood events in 2011, 2012. 2) After transformation to form pool-and-riffle habitat, for aquatic community composed of freshwater fish, macro invertebrate, and attached algae, the species diversity and population gradually increased. 3) The riverbed technique achieved desired effect on enhancement of ecological function in hyporheic zone.

Damage detction and characterization using EMI technique under varying axial load

  • Lim, Yee Yan;Soh, Chee Kiong
    • Smart Structures and Systems
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    • v.11 no.4
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    • pp.349-364
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    • 2013
  • Recently, researchers in the field of structural health monitoring (SHM) have been rigorously striving to replace the conventional NDE techniques with the smart material based SHM techniques, employing smart materials such as piezoelectric materials. For instance, the electromechanical impedance (EMI) technique employing piezo-impedance (lead zirconate titanate, PZT) transducer is known for its sensitivity in detecting local damage. For practical applications, various external factors such as fluctuations of temperature and loading, affecting the effectiveness of the EMI technique ought to be understood and compensated. This paper aims at investigating the damage monitoring capability of EMI technique in the presence of axial stress with fixed boundary condition. A compensation technique using effective frequency shift (EFS) by cross-correlation analysis was incorporated to compensate the effect of loading and boundary stiffening. Experimental tests were conducted by inducing damages on lab-sized aluminium beams in the presence of tensile and compressive forces. Two types of damages, crack propagation and bolts loosening were simulated. With EFS for compensation, both cross-correlation coefficient (CC) index and reduction in peak frequency were found to be efficient in characterizing damages in the presence of varying axial loading.

Crack source location by acoustic emission monitoring method in RC strips during in-situ load test

  • Shokri, Tala;Nanni, Antonio
    • Smart Structures and Systems
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    • v.13 no.1
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    • pp.155-171
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    • 2014
  • Various monitoring techniques are now available for structural health monitoring and Acoustic Emission (AE) is one of them. One of the major advantages of the AE technique is its capability to locate active cracks in structural members. AE crack locating approaches are affected by the signal attenuation and dispersion of elastic waves due to inhomogeneity and geometry of reinforced concrete (RC) members. In this paper, a novel technique is described based on signal processing and sensor arrangement to process multisensory AE data generated by the onset and propagation of cracks and is validated with experimental results from an in-situ load test. Considering the sources of uncertainty in the AE crack location process, a methodology is proposed to capture and locate events generated by cracks. In particular, the relationship between AE events and load is analyzed, and the feasibility of using the AE technique to evaluate the cracking behavior of two RC slab strips during loading to failure is studied.

Structural health monitoring of a newly built high-piled wharf in a harbor with fiber Bragg grating sensor technology: design and deployment

  • Liu, Hong-biao;Zhang, Qiang;Zhang, Bao-hua
    • Smart Structures and Systems
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    • v.20 no.2
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    • pp.163-173
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    • 2017
  • Structural health monitoring (SHM) of civil infrastructure using fiber Bragg grating sensor networks (FBGSNs) has received significant public attention in recent years. However, there is currently little research on the health-monitoring technology of high-piled wharfs in coastal ports using the fiber Bragg grating (FBG) sensor technique. The benefits of FBG sensors are their small size, light weight, lack of conductivity, resistance corrosion, multiplexing ability and immunity to electromagnetic interference. Based on the properties of high-piled wharfs in coastal ports and servicing seawater environment and the benefits of FBG sensors, the SHM system for a high-piled wharf in the Tianjin Port of China is devised and deployed partly using the FBG sensor technique. In addition, the health-monitoring parameters are proposed. The system can monitor the structural mechanical properties and durability, which provides a state-of-the-art mean to monitor the health conditions of the wharf and display the monitored data with the BIM technique. In total, 289 FBG stain sensors, 87 FBG temperature sensors, 20 FBG obliquity sensors, 16 FBG pressure sensors, 8 FBG acceleration sensors and 4 anode ladders are installed in the components of the back platform and front platform. After the installation of some components in the wharf construction site, the good signal that each sensor measures demonstrates the suitability of the sensor setup methods, and it is proper for the full-scale, continuous, autonomous SHM deployment for the high-piled wharf in the costal port. The South 27# Wharf SHM system constitutes the largest deployment of FBG sensors for wharf structures in costal ports to date. This deployment demonstrates the strong potential of FBGSNs to monitor the health of large-scale coastal wharf structures. This study can provide a reference to the long-term health-monitoring system deployment for high-piled wharf structures in coastal ports.

A Study on Applicability of Wireless Impedance Sensor Nodes Technique for Tensile Force Monitoring of Structural Cables (구조용 케이블의 인장력 모니터링을 위한 무선 임피던스 센서노드 기술의 적용성에 관한 연구)

  • Park, Jae-Hyung;Hong, Dong-Soo;Kim, Jeong-Tae;Na, Won-Bae;Cho, Hyun-Man
    • Journal of Korean Society of Steel Construction
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    • v.22 no.1
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    • pp.21-31
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    • 2010
  • In this study, a technique that uses wireless impedance sensor nodes is proposed to monitor tensile force of structural cable. To achieve this goal, the following approaches were implemented. First, a wireless impedance sensor node was designed for automated and cost-efficient prestress-loss monitoring. Second, an impedance-based algorithm was embedded in the wireless impedance sensor node for autonomous structural health monitoring of structural cables. Third, a tensile force monitoring technique that uses an interface plate for structural cables was proposed to overcome the limitations of the wireless impedance sensor node such as its narrow-band measurable frequency ranges. Finally, the applicability of the wireless impedance sensor node and the technique that uses the interface washer were evaluated in a lab-scaled prestressed concrete (PSC) girder model with internal and external tendons for which several prestress-loss scenarios were experimentally monitored with the wireless impedance sensor nodes.

Simulation of PZT monitoring of reinforced concrete beams retrofitted with CFRP

  • Providakis, C.P.;Triantafillou, T.C.;Karabalis, D.;Papanicolaou, A.;Stefanaki, K.;Tsantilis, A.;Tzoura, E.
    • Smart Structures and Systems
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    • v.14 no.5
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    • pp.811-830
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    • 2014
  • A numerical study has been carried out to simulate an innovative monitoring procedure to detect and localize damage in reinforced concrete beams retrofitted with carbon fiber reinforced polymer (CFRP) unidirectional laminates. The main novelty of the present simulation is its ability to conduct the electromechanical admittance monitoring technique by considerably compressing the amount of data required for damage detection and localization. A FEM simulation of electromechanical admittance-based sensing technique was employed by applying lead zirconate titanate (PZT) transducers to acquire impedance spectrum signatures. Response surface methodology (RSM) is finally adopted as a tool for solving inverse problems to estimate the location and size of damaged areas from the relationship between damage and electromechanical admittance changes computed at PZT transducer surfaces. This statistical metamodel technique allows polynomial models to be produced without requiring complicated modeling or numerous data sets after the generation of damage, leading to considerably lower cost of creating diagnostic database. Finally, a numerical example is carried out regarding a steel-reinforced concrete (RC) beam model monotonically loaded up to its failure which is also retrofitted by a CFRP laminate to verify the validity of the present metamodeling monitoring technique. The load-carrying capacity of concrete is predicted in the present paper by utilizing an Ottosen-type failure surface in order to better take into account the passive confinement behavior of retrofitted concrete material under the application of FRP laminate.

A Data Mining Technique for Customer Behavior Association Analysis in Cyber Shopping Malls (가상상점에서 고객 행위 연관성 분석을 위한 데이터 마이닝 기법)

  • 김종우;이병헌;이경미;한재룡;강태근;유관종
    • The Journal of Society for e-Business Studies
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    • v.4 no.1
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    • pp.21-36
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    • 1999
  • Using user monitoring techniques on web, marketing decision makers in cyber shopping malls can gather customer behavior data as well as sales transaction data and customer profiles. In this paper, we present a marketing rule extraction technique for customer behavior analysis in cyber shopping malls, The technique is an application of market basket analysis which is a representative data mining technique for extracting association rules. The market basket analysis technique is applied on a customer behavior log table, which provide association rules about web pages in a cyber shopping mall. The extracted association rules can be used for mall layout design, product packaging, web page link design, and product recommendation. A prototype cyber shopping mall with customer monitoring features and a customer behavior analysis algorithm is implemented using Java Web Server, Servlet, JDBC(Java Database Connectivity), and relational database on windows NT.

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Sensor clustering technique for practical structural monitoring and maintenance

  • Celik, Ozan;Terrell, Thomas;Gul, Mustafa;Catbas, F. Necati
    • Structural Monitoring and Maintenance
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    • v.5 no.2
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    • pp.273-295
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    • 2018
  • In this study, an investigation of a damage detection methodology for global condition assessment is presented. A particular emphasis is put on the utilization of wireless sensors for more practical, less time consuming, less expensive and safer monitoring and eventually maintenance purposes. Wireless sensors are deployed with a sensor roving technique to maintain a dense sensor field yet requiring fewer sensors. The time series analysis method called ARX models (Auto-Regressive models with eXogeneous input) for different sensor clusters is implemented for the exploration of artificially induced damage and their locations. The performance of the technique is verified by making use of the data sets acquired from a 4-span bridge-type steel structure in a controlled laboratory environment. In that, the free response vibration data of the structure for a specific sensor cluster is measured by both wired and wireless sensors and the acceleration output of each sensor is used as an input to ARX model to estimate the response of the reference channel of that cluster. Using both data types, the ARX based time series analysis method is shown to be effective for damage detection and localization along with the interpretations and conclusions.