Modal Parameters Identification By Combined Determinisic-Stochastic Subspace Identification Method

The health monitoring of bridge structure is getting more and more attention. Structural modal parameter identification plays an important role in health monitoring. It is not only the foundation of health monitoring, but also an important part of structural dynamic identification. Deterministic-stochastic subspace identification method is a system identification method, which currently has no practical application in bridge structure. Therefore, this thesis mainly discuss about the application of combined determinisic-stochastic subspace in structural model parameter identification. The main work of this thesis are list as fellows:1. Description of stochastic subspace identification of structural modal parameter, determinisic-stochastic subspace identification method and time-varying structure identification.2. Description of the theory of determinisic-stochastic subspace method and proposing a method of determinisic-stochastic subspace sliding window method for structure modal time-varying identification. Programs are built based on MATLAB.3. Structural modal parameters are identified via determinisic-stochastic subspace method and determinisic-stochastic subspace sliding window method in tower injury test and cable-stayed bridge shaking table test.4. Results indicate that determinisic-stochastic subspace method can identify model parameters by structural excitation and structural response. As damage develops, The frequency will gradually decrease and damping ratio increases.5. For non-time-varying linear structure, when vibration frequency remains unchanged, results in both combined determinisic-stochastic subspace method and determinisic-stochastic subspace sliding window method are the same.6. For time-varying nonlinear structure, frequency identification results in determinisic-stochastic subspace method are relatively low. Results by determinisic-stochastic subspace sliding window method indicate that frequency will decrease to a certain value as amplitude increases, and then increase as amplitude decreases and become stable at the end of earthquake.