• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.639-645
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• 2006

FRP (Fiber Reinforced Polymer) is an excellent new constructional material in resistibility to corrosion, high intensity, resistibility to fatigue, and plasticity. FBG (Fiber Bragg Grating) sensor is widely used at present as a smart sensor due to lots of advantages such as electric resistance, small-sized material, and high durability. However, with insufficiency of measuring displacement, FBG sensor is used only as a sensor measuring physical properties like strain or temperature. In this study, FRP and FBG sensors are to be hybridized, which could lead to the development of a smart FRP rod. Moreover, developing the estimated model for deflection with neural network method, with the data measured through FBG sensor, could make conquest of a disadvantage of FBG sensor - uniquely used for sensing strain. Artificial neural network is MLP (Multi-layer perceptron), trained within error rate of 0.001. Nonlinear object function and back-propagation algorithm is applied to training and this model is verified with the measured axial displacement through UTM and the estimated numerical values.

• Composites Research
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• v.22 no.1
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• pp.32-38
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• 2009

Recently structural monitoring using fiber optic sensors became popular, but the fiber sensors are very difficult to apply to the real structure due to difficulty of handling. In this research, we developed the fiber sensor packages easy to attach or fasten to the structures like ordinary electric sensors. We apply the fiber sensors to the real tunnel structure for measuring the strains and shape changes. The applied fiber optics sensors show the behavior of tile tunnel structures. We summarize the data from tunnel for 2 year construction period and confirm the structural behavior of tunnel.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.2
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• pp.86-91
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• 2010

We constructed a quasi-distributed fiber-optic sensor network for the safety monitoring in power systems. It is possible to construct many of FBG sensors in a line and to be immune from electromagnetic noise. For demodulation analysis of reflected wavelength from FBG sensor, we proposed a simple and fast system using a InGaAs photo-diode array and a holographic diffraction grating. For accuracy improvement of the proposed demodulation system, we applied a Gaussian line-fitting algorithm. We obtained about 4[pm] of wavelength resolution and stability.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.3-9
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• 2006

Among many fabrication methods of composite materials, filament winding is the most effective method for fabricating axis-symmetric structures such as pressure tanks and pipes. Filament wound pressure tanks are under high internal pressure during the operation and it has the complexity in damage mechanisms and failure modes. Fiber optic sensors, especially FBG sensors can be easily embedded into the composite structures contrary to conventional electric strain gages (ESGs). In addition, many FBG sensors can be multiplexed in single optical fiber using wavelength division multiplexing (WDM) techniques. In this paper, we fabricated several filament wound pressure tanks with embedded FBG sensors and conducted some kinds of experiments such as an impact test, a bending test, and a thermal cycling test. From the experimental results, it was successfully demonstrated that FBG sensors are very appropriate to composite structures fabricated by filament winding process even though they are embedded into composites by multiplexing.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.6
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• pp.11-15
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• 2009

Recently, a new PSC (Prestressed Concrete) bridge system, which is supported by Concrete-filled fiber-reinforced polymer (CFFRP) strut, has been introduced. This bridge is able to reduce self-weight and increase the width of traditional PSC bridges. However, no relevant research has been reported on local behavior of CFFRP strut in the bridge system. The purpose of this study is to investigate local behavior of CFFRP struts using fiber Bragg grating (FBG) sensors. Field tests were performed to examine the hoop strains and longitudinal strains of the FRP strut under various lateral positions and velocities of a test truck. It has been observed that CFFRP strut is under compression regardless of vehicle speed and location. However, the CFFRP strut is sensitive to the lateral position of vehicles in terms of strain magnitude. Results also indicated that the FBG sensors can faithfully record the hoop and longitudinal strains of the FRP strut without electro-magnetic interference.

• Smart Structures and Systems
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• v.9 no.5
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• pp.393-410
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• 2012

Conventional geotechnical instrumentation techniques available for monitoring of slopes, especially soil-nailed slopes have limitations such as electromagnetic interference, low accuracy, poor longterm reliability and difficulty in mounting a series of strain sensors on a soil nail bar with a small-diameter. This paper presents a slope monitoring system based on fibre Bragg grating (FBG) sensing technology. This monitoring system is designed to perform long-term monitoring of slope movements, strains along soil nails, and other slope reinforcement elements. All these FBG sensors are fabricated and calibrated in laboratory and a trial of this monitoring system has been successfully conducted on a roadside slope in Hong Kong. As part of the slope stability improvement works, soil nails and a toe support soldier-pile wall were constructed. During the slope works, more than 100 FBG sensors were installed on a soil nail, a soldier pile, and an in- place inclinometer. The paper presents the layout and arrangement of the instruments as well as the installation procedures adopted. Monitoring data have been collected since March 2008. This trial has demonstrated the great potential of the optical fibre monitoring system for long-term monitoring of slope performance. The advantages of the slope monitoring system and experience gained in the field implementation are also discussed in the paper.

• Journal of the Korean Solar Energy Society
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• v.32 no.4
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• pp.1-8
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• 2012

A Fiber Bragg Grating (FBG) sensor imbedded small wind turbine blade was manufactured to experimentally investigate the feasibility to embed FBG sensors between layers of glass fiber to monitor dynamic strains of the wind turbine blade. The blade which is similar to a commercial 300 W wind turbine blade was manufactured with glass fiber as a reinforcement and epoxy resin as base material. A total of five FBG sensors including one temperature sensor were imbedded in the blade to sense mechanical strain and temperature. While manufacturing the blade, residual strain and temperature that occurred in the small wind turbine blade were monitored using the imbedded FBG sensor array. To examine the sensor performance, an impact test was carried out. The experimental results from the FBG sensors were close to those from electrical strain gages mounted on the blade root surface. The mode shapes of the blade were analyzed also using a commercial Ansys simulation with a model obtained from a three dimensional laser scanning of the blade.

• Smart Structures and Systems
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• v.14 no.2
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• pp.145-158
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• 2014

The objective of this study is to improve the survivability and reliability of the FBG sensor network in the structural health monitoring (SHM) system. Therefore, a model reconstruction soft computing recognition algorithm based on support vector regression (SVR) is proposed to achieve the high reliability of the FBG sensor network, and the grid search algorithm is used to optimize the parameters of SVR model. Furthermore, in order to demonstrate the effectiveness of the proposed model reconstruction algorithm, a SHM system based on an eight-point fiber Bragg grating (FBG) sensor network is designed to monitor the foreign-object low velocity impact of a CFRP composite plate. Simultaneously, some sensors data are neglected to simulate different kinds of FBG sensor network failure modes, the predicting results are compared with non-reconstruction for the same failure mode. The comparative results indicate that the performance of the model reconstruction recognition algorithm based on SVR has more excellence than that of non-reconstruction, and the model reconstruction algorithm almost keeps the consistent predicting accuracy when no sensor, one sensor and two sensors are invalid in the FBG sensor network, thus the reliability is improved when there are FBG sensors are invalid in the structural health monitoring system.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.4
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• pp.160-166
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• 2006

Optical Fiber Bragg Grating sensor has a good performance to measure microscopic displacement which can measure strain of lining concrete and cylindrical structure like high intensity containment building and it can present many advantages like a corrosion resistance from the durability point of view. Then it can measure plane geometrical displacement of cylindrical structures with two-way displacement FBG sensor module. According to the test result, measurement of FBG sensor is better performance than other electric sensor system and 2D-level measurement. As a test result, Resolution of the two-way displacement sensor module with FBG sensors are more 10 times than other LVDT or 2D surveying.

• Proceeding of KASS Symposium
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• 2008.05a
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• pp.189-194
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• 2008

The main object of this paper is that it's possible to monitoring the deformation of cable in the tensegrity structure. always monitoring system of Fiber Bragg Grating(FBG)Sensor is described. The measurement of parts on the cable is very important. We make an experiment with measuring deformation of cable in the tensegrity structure to the pressure conditions. In the result of experiment, the fiber sensors showed good response to the pressure conditions. Therefore, We could calculate the deformation of cable structure and be possible health monitoring of the tensegrity structure.