Determining minimum number of required accelerometer for output-only structural identification of frames

Operational modal analysis (OMA) aims at identifying the modal properties of a structure based on response data of the structure excited by ambient sources. 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, the modal parameters (natural frequencies, mode shapes) of the beams 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 the dynamic characteristics of frames. Then, the minimum number of required accelerometer has been determined that recording the acceleration in that location leads to identifying all the natural frequencies of the frame.