Development of an early seismic damage detection technology for civil infrastructures

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1. Development of the broadband optical fiber sensor for seismic damage detectionA novel packaged long-gage FBG (Fiber Bragg Grating) sensor for health monitoring of civil structure has been developed and verified to have the ability to obtain effective macro-strain distributions. Moreover, temperature fluctuation poses a great obstacle in damage identification and structural health monitoring (SEM) of civil structures. A new compensation method of temperature effects on strain measurement has been modeled by using Multiple Regression and Neural Networks (NN) analysis based on temperature and strain distribution measured at a bridge model2. Development of the broadband memory sensor for seismic damage detectionExperimental study on application of PVDF (polarized polyvinylindene fluoride) film as a crack detection sensor was conducted to detect occurrence and propagation of cracks in aluminum specimen and RC beams. It is confirmed that the PVDF film sensor is able to catch the generation of micro-crack and provide information of strain distribution better than those of traditional strain gauge sensors. A wireless acceleration sensor system has been developed and was used for a rudimentary vibration experiment. The experimental results showed that the wireless acceleration sensor system is applicable vibration measurement for structural damage monitoring.3. Development of seismic soundness diagnosis and analysis systemIn order to monitor the soundness for real-time, a two-level strategy was proposed far damage detection in flexural structures using modal parameters extracted from dynamic macro-strain responses. And, a neural network system, which consists of multi-inputs and multi-outputs, was proposed as the damage detection technique of long-span cable-stayed bridge. The neural network system which was built based on response information of multiple locations is able to grasp damage location and damage extents.