Experimental study for damage detection of structures using FBG(Fiber Bragg Grating) sensors is presented. Static and dynamic methods were used. The static method is based on the detection of the strain reductions due to the damages. The dynamic method involves extracting of the strain mode shapes from the dynamic strain measurements and signal processing of the strain mode shapes. The CSD(Cross Spectral Density) functions are used for extracting the strain mode shapes. In the signal processing, the modified Laplacian operator method and the curvature mode shape method were used. The former uses only the strain mode shapes of the damaged case, while the latter requires the strain mode shapes of the undamaged and damaged cases. Experiments are carried out for two different structures. On a four-story steel frame structure, the static method using the conventional strain gauges was mainly used, and comparisons were also made between the strain measurements by the strain gauges and FBG sensors. On a simple beam element, both of the static and dynamic methods were used. The conventional strain gauges and accelrometers are also used to compare the performance of the damage detections using FBG sensors. The curvature mode shape method is found to give better damage estimation than the modified Laplacian operator method. Among three types of sensors, the accelerometers give better performance than the other two sensors. However, as more FBG sensors may be easily employed owing to the multiplexing capability, the performance of the damage detection using the FBG sensor system is expected to be improved rapidly.
