A comparative study of digital image correlation and fiber Bragg grating sensors based on strain measurements

Fiber Bragg grating (FBG) sensors are gaining prominence as contact sensors to find the field of displacement and strain measurements in recent times for structural health monitoring (SHM) applications, whereas digital image correlation (DIC) is a proven and widely used non-contact optical measurement method for finding displacement and strains developed on the surface of an object. For dynamic bridge monitoring, a prototype of a circular accelerated pavement testing track (APT) is constructed and results obtained from both the methods are compared. For DIC measurements, a random speckle pattern on the APT was utilized as a non-contact sensor, while FBGs were connected as contact sensors in the tension portion of the APT, exactly beneath the region of random speckle patterns for measurements and comparison. The experimental results demonstrated that the strain sensitivity of FBG measurements is quite high compared to DIC values. However, there was a very good agreement between the normalized principal strain values obtained from both the methods.