Modal Analysis Based On ODS And Stochastic Subspace Identification

Model analysis is the procedure of determining a structure's dynamic characteristics recently , is a application of system identification method in vibration domain . Mode is structure's inherence characteristics , each mode has specifically resonant frequencies , damping values , mode shapes, mode stiffness and mode mass. To obtain these modes , we can calculating and experimental analysis , such the course of theory and experimental analysis called Model analysis .Based on the background of practical engineering , modal parameters identification of a steel frame structure in this paper . Fist , the dynamic character of the structure are analyzed by the Finite Element Model (FEM) obtain the low ten model resonant frequencies and model shapes . Then model experimental on the steel frame structure , experiment uses random knock and single knock separately on the steel frame structure through a force hammer . We can gained the data of experiment using transducers and the data acquisition system and post treatment of the data .Modal parameters identification include ODS ,ODS mainly use MATLAB procedure(Response spectrum method , SSI) for dealing with the experiment data .Response spectrum method is using APS , CPS to identify modal parameters including resonant frequencies , damping and model shapes . Stochastic subspace identification(SSI) is a advanced modal parameters identification method , but traditional subspace parameters identification method based on having input data .An improved method of stochastic subspace identification is given in this paper . The problems existing for structural model parameter identification , ODS and SSI in the conclusion of this paper .