Strain measuring sensors have been increasingly employed in strain modal analysis for structural health monitoring. Fiber bragg grafts, piezoelectric sensors, and conventional strain gauges are readily used strain gauges. Conventional strain gauges lack the dynamic strain measuring capability and fiber bragg sensors prove to be uneconomical for large structures. Piezoelectric or piezo sensors, though very efficient for dynamic strain monitoring and cost-effective, needs to be bonded on the structure like other strain gauges. This study investigates a non-bonded configuration of ceramic-based piezo sensors for experimental modal analysis (EMA). Artificial damage was created by cutting out a hole in the center of the plate. Non bonded piezo sensors (NBPS) and an accelerometer (ACC) are used to measure the dynamic response of a steel plate specimen. Single input single output (SISO) technique was adopted for the excitation and measurements from the specimen. Vibration frequencies and mode shape from all three sensors are compared in pristine and damaged state. NBPS was found to be as effective as accelerometers for damage detection and, being strain oriented were more sensitive towards damage than accelerometer. No observable change was observed in the vibrational frequencies after damage. Modal assurance criteria was adopted to quantify the change in the mode shapes due to the damage. Strain based displacement mode shapes from NBPS were more sensitive towards damage than displacement mode shapes from the accelerometer.
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