Investigation On The Structrue's Damping Extraction Techniques

Vibration Modal analysis and parameters identify is one activity embranchment of vibration engineering. It is the foundation of structure's dynamic designing, decrease and eliminates vibration and control vibration. Vibration Modal analysis and parameters identify is an analysis method which is used in "athwart question" in the Structure Dynamics. It is used to solve the structures' problems by associative experiments with theoretic analysis. So far, it is abroad applied in the projects domain and it is becoming important shift to solve structures' problems. The goal of Modal analysis is to identify modal parameters to analyze system of structures' vibration characteristic, fault diagnosis and forecast in order to provide gist to optimum designing.Factual configuration could be considered as multi-degree of freedom with damping. For multi-degree of freedom, it is not only much harder to analysis, but also possessing characteristics that single degree of freedom systems don't have. Structure's Modal Parameters include mass, rigidity, damping, we can identify them by modal analysis extraction techniques.It focus on how to identify structure's damping in this thesis, because it's the most hard to be identified and the problems brought by damping are important on frame design or to optimize structure design. Many researchers have devoted their work to the development of modal analysis extraction techniques in order to obtain more reliable identification of the modal parameters. Also, there are some other works devoted to the evaluation and comparison of these methods in order to find which one is the most reliable method with respect to certain characteristics.The following works have been done in this thesis:1. Four Modal Analysis methods — the Rational Fraction Polynomial Method, the Complex Exponential Method, the Ibrahim Time Domain Method, and Hilbert Envelope Method are collected to investigate in the thesis.2. Using the four methods to identify the modal damping with appropriatedynamics model and protract relevant plots.3. Compare the results identified by the four methods; Investigating how the damping ratio estimation is affected with respect to each method in different conditions.4. According to the results, point out how to choose the best accurate identification method in the actual projects.5. Use the optimum identification method to identify the Websteel Structure's damping, which dynamic characteristic experiment had been done by Civi Engineering and Architectures School, Wuhan University of Technology.6. Because of finite level of author, there are some problems haven't been solved or done well. The thesis gives some suggestions to investigation in the future.