Investigation On The Structure's Damping Identification Techniques In Time Domain

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 project domain and it is becoming important shift to solve structure' 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.Structure's Modal Parameters include mass, rigidity, damping, we can identify them by modal analysis extraction techniques. 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. There are many damping identification methods, but each one has different merit and defect. In order to find which one is the most reliable method with respect to certain characteristics, this thesis focus on how to identify structure's damping in time domain.The following works have been done in this thesis:1. Four modal analysis methods------the LSCE Method, the Ibrahim Time Domain Method, the Time Domain Collectivity Modal Parameter Methods and the Rational Fraction Polynomial Method are collected to be investigate in the thesis.2. Using the four methords to identify the modal damping with appropriate dynamics modal and protract relevant plots.3. Compare the results identified by the four methods and investigate 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 a Wooden Structure's damping, which dynamic characteristic experiment had been done by author's tutor, Li shujin Professor, in the Strong Shock Response Laboratory of the Defending Disaster Graduate School in Kyoto University.6. Because of the finite level of author, there are still some problems haven't been solved or done well. Finality, the thesis gives some suggestions about investigation in the future.