System identification based on experimental responses of a frame structure with unknown inputs

System identification of a frame was performed based on experimental acceleration responses with unknown inputs. The ambient vibration was simulated in the lab, and the block Hankel matrix and the cross-correlation were calculated according to the eigensystem realization algorithm. The singular values were obtained by singular value decomposition. The frequencies and damping ratios were identified according to the values of indices MAC, EMAC, MPC, CMI, and the pseudo parameters were eliminated. The results were verified by the experiment and the FEM calculation, and their difference was inspected. The investigation indicates that the dynamic parameters are able to be identified by use of eigensystem realization algorithm with unknown inputs.