Alternate strain based-modal analysis using piezosensors

Modal analysis based structural health monitoring (SHM) is required now more than ever due to many factors such as aging infrastructure, loading incidents likely earthquakes, over loading etc. Although the continuous monitoring of structures is a full-fledged commercial sector, its high cost makes it infeasible for large structures as the number of sensors required is large. Accelerometers, widely used as sensors in SHM, in addition to high cost, possess some other challenges such as damage vulnerability in environmental and operational conditions. In this research, low cost lead-zirconate-zitanate (PZT) sensors are proposed as replacement of costly and fragile accelerometers as sensors for SHM. PZT patches, which cost less than one-tenth of the accelerometers, can also be embedded in the reinforced concrete structures to protect from the harsh operational conditions. In this paper, PZT patches are studied by technique of experimental modal analysis (EMA) on a steel beam specimen and the results are compared with the traditionally used accelerometers. Single input single output (SISO) approach is adopted for EMA of the rectangular steel beam. PZT sensors are able to capture modal data in terms of natural frequencies and mode shapes in good agreement with accelerometer. The fundamental natural frequency of the beam is obtained with the error of less than 1 % as compared to the accelerometer. The signal to noise ratio is of same order as accelerometer. The strain mode shape from the PZT sensors is well correlated to displacement mode shapes from the accelerometer by a modal assurance criteria (MAC) values greater than 0.9 for observed experimentally.