Structural vibration response and testing estimation of modal properties amplitude dependent modal properties

Abstract

In this thesis, we are going to look at oscillatory behaviors i.e., vibrations of a structure given by basic structural dynamic theories. Structures in the real world are generally so complicated that it is very hard to come up with a formulated process to get theoretical modal properties by conventional structural analysis methods. The main emphasis of this thesis is to explore various approaches implemented in the modern vibration response testing industry, which estimate the modal properties of a structure via the response data exclusively. This process, applying basic ideas of Operational Modal Analysis (OMA), provides a possibility for determining the modal properties of complicated structures whose properties are difficult to obtain. The methods elaborated in later chapters include Logarithmic Decrement Method, Half-power Bandwidth Method, and Impact Hammer Test. Some basic concepts of mathematical tools (i.e., Fourier analysis) we use are also included. Furthermore, this thesis also involves a scratch of the topic ‘amplitude-dependent modal property’, investigating the matter of how modal properties possibly vary with the change of vibration amplitude. This thesis reflects the effort I have put into my undergraduate Final Year Project (FYP) at NTU.