Application of transmissibility measurement in estimation of modal parameters of a structure

Applications of modal analysis are closely related to utilizing the derived modal model in design, problem solving and analysis. Dynamic behavior of structures can be studied by modeling the relation between forces acting on the structure and the resulting structural vibration responses. In real conditions, it often becomes hard or impossible to measure the excitation forces. Operational Modal Analysis (OMA) is a practical tool to overcome this problem. In OMA the structure is excited by ambient forces and only the responses are taken into account. Current output-only techniques have limitations when applied to some practical cases. One limiting constraint of the current OMA techniques is that the non-measured excitations to the system in operation must be white-noise sequences. However, structural vibrations observed in operation cannot always be considered as pure white-noise excitation. On the other hand, modal parameters can be identified from output-only transmissibility measurements in which no assumption about the nature of the excitations to the system is made. In this paper, the accuracy of outputonly transmissibility measurements method is investigated. The modal parameters of a cantilever beam are estimated both from transmissibility measurements method and Finite Element Method. Finally, drawing a comparison between resultant parameters through above methods represents the precision and efficiency of the method.

Application of transmissibility measurement in estimation of modal parameters of a structure Keywords:

Transmissibility Measurement , Operational Modal Analysis , Modal Parameters