• 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.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.1
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• pp.47-53
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• 2012

As one of the methods for recycling the FRP from the waste ships, separation of roving layer from the mat has some merits in a sense of the eco-friendly and economical recycling process. Similar characteristics, however, between the roving and the mat even with different ratio of the resin and the glass and the thickness of the roving, much thinner than the mat, make the mechanically automatic differentiation difficult. In this study spectrochemical differentiation between the two layers has been made using boiling concentrated sulfuric acid, methanol and isopropanol solution saturated with KOH, or hydrogen fluoride (HF) solution. Furthermore efficiently coloring water-soluble dye following the HF treatment makes the roving layer more distinguishable photophysically. The layer differentiation and the automatic layer distraction move up the date of simple and automatic separation process for the waste FRP.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.1
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• pp.55-59
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• 2009

As one of the methods for recycling the FRP from the small and medium waste ships, separation of roving layer from the mat has some merits in a sense of the recycling energy and the environmental effects. Similar characteristics, however, between the roving and the mat even with different ratio of the resin and the glass and the thickness of the roving, much thinner than the mat, make the mechanically automatic differentiation difficult. In this study spectrochemical differentiation between the two layers has been made using (1) boiling concentrated sulfuric acid which can dissolve the resin in the FRP layer, (2) methanol and isopropanol solution saturated with KOH which can dissolve the glass, or (3) hydrogen fluoride(HF) solution which can reacts with $SiO_2$ fragments of the glass. Furthermore coloring water-soluble dye following the HF treatment makes the roving layer more distinguishable photo-physically.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.1
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• pp.43-46
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• 2010

As one of the methods for recycling the FRP used for the small and medium-sized waste ships, separation of the roving layer from the mat has some merit in a sense of the recycling energy and the environmental effects. Similar characteristics between the roving and the mat make the mechanically automatic differentiation difficult. They, however, contain different ratio of the resin and the glass and the thickness. In this study photo physical differentiation between the two layers has been made using (1) boiling concentrated sulfuric acid which can dissolve the resin in the FRP layer and (2) hydrogen fluoride(HF) solution which can reacts with $SiO_2$ fragments of the glass. Furthermore coloring the FRP sample with water-soluble dye following the HF treatment makes the roving layer more distinguishable photophysically. The implementation of HF treatment has been successfully tested in this study.

• Smart Structures and Systems
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• v.6 no.5_6
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• pp.579-593
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• 2010

Low-power radio frequency (RF) chip transceiver technology and the associated structural health monitoring platforms have matured recently to enable high-rate, lossless transmission of measurement data across large-scale sensor networks. The intrinsic value of these advanced capabilities is the allowance for high-quality, rapid operational modal analysis of in-service structures using distributed accelerometers to experimentally characterize the dynamic response. From the analysis afforded through these dynamic data sets, structural identification techniques can then be utilized to develop a well calibrated finite element (FE) model of the structure for baseline development, extended analytical structural evaluation, and load response assessment. This paper presents a case study in which operational modal analysis is performed on a three-span prestressed reinforced concrete bridge using a wireless sensor network. The low-power wireless platform deployed supported a high-rate, lossless transmission protocol enabling real-time remote acquisition of the vibration response as recorded by twenty-nine accelerometers at a 256 Sps sampling rate. Several instrumentation layouts were utilized to assess the global multi-span response using a stationary sensor array as well as the spatially refined response of a single span using roving sensors and reference-based techniques. Subsequent structural identification using FE modeling and iterative updating through comparison with the experimental analysis is then documented to demonstrate the inherent value in dynamic response measurement across structural systems using high-rate wireless sensor networks.