Application of Hilbert Huang transform to identify the natural frequencies of steel frame

Identification of dynamic structural characteristics such as natural frequency based on measured vibration responses at site is one of the important steps in the structural investigation work of loading test and structural health monitoring. During the service stage, the dynamic characteristics can be changed due to the stiffness reduction and nonlinear of structure under extrema excitation. Therefore, the identification of instantaneous parameters of structure is very necessary in detecting and monitoring the structural deterioration continuously by the time. This paper presents the data processing method using Hilbert Huang Transform (HHT) algorithm in determining a time-dependent frequencies of steel frame. The vibration experiment for steel frame was conducted in this study. The acceleration responses in time domain were recorded and analyzed by HTT to determine the fundamental natural frequencies of frame. The instantaneous frequencies in the time domain of steel frame are the main finding in this research. The traditional data processing method using a Fast Fourier Transform (FFT) was conducted and compared with the HHT method. Keywords: Hilbert Huang Transform (HHT); steel frame; Fast Fourier Transform (FFT); natural frequency.