Comparison of Extracted Modal Parameters Using FRF and Measured Operational Dynamic Data

For the last few years there is a growing interest in research domain of structural health monitoring as a number of structural failure and casualty took place all over the world due to negligence in structural health monitoring. Although a lots of research has been carried out in the field of structural health monitoring, but the researchers are still in search of an effective, easy, economical and reliable technique to identify and quantify real life structural damage. The natural frequency and mode shape extraction of Civil Engineering structures are very important for dynamic analysis of structures and structural damage identification as well as damage quantification. In this paper, an operational modal analysis of a steel cantilever beam has been carried out and natural frequency has been extracted by FRF. The operational modal analysis has been carried out by Single Response Technique. During testing, several groups of input force and output acceleration are measured simultaneously. This signal is converted into a frequency domain known as the Fast Fourier Transform (FFT), resulting in a spectrum of input force and output acceleration. Thereafter the coherence function is used to evaluate the quality of FRF. The accuracy of the extracted natural frequency has been further validated by operational modal analysis as well as by analytical technique using MATLAB platform.