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Continuous Monitoring of an Aging PC Bridge by Using Fiber-Optic Strain Sensors Based on Time-Series Analysis in Considering Environmental Effects



This study is aimed to construct a continuous structural health monitoring (SHM) system for an existing prestressed concrete (PC) bridge, in which the fractures of PC cables were found. This is why the structural condition monitoring is required for assuring safety use until the replacement. The fiber-Bragg grating (FBG) sensor network for acquiring multipoint strain data was then installed, and two kinds of data acquisition were carried out. The first one was the static loading tests, which were performed before, after, and one year after the reinforcement of the bridge. The second one was the continuous data acquisition from December 2011 to November 2012. In this paper, we firstly show the comparison of strain data acquired in the loading tests, and indicates that it is difficult to reveal the structural condition and its changes only by the periodic data acquisition. The continuous monitoring data consist of multipoint strain data that were acquired every one hour for eleven months. It was clearly recognized that the time series of strain showed high correlation with the temperature, in addition, the possibilities of correlations with the sunshine duration and the snow accumulation in winter were also indicated. To analyze those environmental effects and extract the structural condition, we then considered applicability of the time-series analysis. It was then shown that the trend and variations of strain data could be reconstructed by applying the seasonal autoregressive integrated moving average (ARIMA) model.

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