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A massive concrete structure has a lot of micro-cracks due to the hydration heat. In general, conventional electric sensors have a certain limit in measuring cracks because of the noise. The durability is also badly influenced by corrosion. Recently, optical fiber sensors have demonstrated their superiority over conventional sensors and are able to solve these problems. Thus, in this work, embedded Fiber Bragg Grating (FBG) sensors for measurement of cracks in massive concrete due to hydration heat are developed and investigated. The developed sensor has the potential to perform strain measurement under harsh conditions in the presence of electrical noise and electromagnetic interference. Particularly, these FBG strain sensors are easily installed and found to be durable for massive concrete structures such as dams, bridges, nuclear structures, etc.

In this study, we have proposed a method of monitoring of bridges under construction in view of the long-term behavior of the prestress concrete bridge of which the Free Cantilever Method is applied. As a method to confirm the ability of the long-term behavior of the concrete box girder, temperature sensors and strain gauges were installed, and the measured data was used to calculate creep coefficient. Moreover, we have measured the stress of the concrete box girder during construction which was applied with creep coefficient and compared with the changes in temperature to analyze the vertical displacement along the segment. In conclusion, monitoring of the FCM bridge during construction in consideration of the long-term behavior can be analyzed efficiently by suing temperature and displacement data without the use of laser displacement meter or laser delfectometer.

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