GH.R Jahangiry - M.sc. Student of Civil Engineering, Tabari University of Babol, Iran
S.R Nabavian - Ph.D Student of Civil Engineering, Faculty Member, Tabari University of Babol, Iran
L Kalani Sarokolayi - Assistant Professor of Civil Engineering, Faculty Member, Tabari University of Babol, Iran

System identification of ambient vibration structures using output-only identification techniques has become a key issue in structural health monitoring and assessment of engineering structures. Modal parameters of the ambient vibration structures consist of natural frequencies, mode shapes and modal damping ratios. In this paper, a typical frame with arbitrary loading has been modeled in finite element software, ANSYS, and the responses (accelerations of nodes) have been achieved. By using these data and the codes written in MATLAB software, the modal parameters (natural frequencies, mode shapes) of the Frame are identified with FDD (frequency Domain Decomposition) and PP (Peak Picking) methods and then justified with the results of input-output method which was determined by modal analysis. The results indicate that there is a good agreement between three methods for determining dynamic characteristics of Frame. Then, some location of the frame has been determined that recording the acceleration just in that location (reference accelerometer) lead to identify all the natural frequencies of frame.

output-only analysis, modal identification, Frame, PP, FDD