50. Field Investigation of Fundamental Frequency of Structures Using Frequency Domain Vibration Analysis

The transient nature of forces produced in the system requires vibration analysis to determine their behavior patterns accurately. Modal analysis represents the dynamic response of the bridge structure via modal descriptive terms: natural frequencies, mode shapes, and damping ratios. Accurate measurement of these dynamic characteristics for structures allows for better evaluation of structural stability and structural health monitoring of such systems. It is time-saving as well as useful to use force vibration analysis to approximate modal parameters. Natural frequencies are derived from the observations of force vibration analysis techniques. Modified power spectral analysis and cross-power spectral analysis are carried out to identify the structure’s resonant frequency. From the experimental analysis, the range of resonant frequencies observed is 0.9766–4.8828 Hz in longitudinal direction, 1.9531–4.88828 Hz in transverse direction, and 2.9297–4.8828 Hz in vertical direction. Accurate modal parameters estimation of the structures allows better evaluations of structural stability and structural health monitoring.