OUTPUT-ONLY MODAL PARAMETER IDENTIFICATION OF BRIDGE STRUCTURE USING SOBI TECHNIQUE

Blind source separation (BSS) techniques attempt to recover special source components that are mixed together in the measured data. Independent Component Analysis (ICA) is a popular method used to solve the BSS problem by recovering components that are statistically independent. In this paper, a methodology based on second order blind identification (SOBI) is presented for the modal parameter identification of ambient vibration response of bridge structure. The random decrement signal (RDS) of the measured vibration response of the bridge under ambient excitation, rather than the actual measured response, is treated as the outputs of the system. The concept of virtual source is exploited and the vibration system modals are regarded as the source. The SOBI is then employed to extract the frequency, damping and mode of the system from the RDS. The capabilities of SOBI and the other identification methods such as stochastic subspace identification (SSI) and frequency domain decomposition (FDD) are compared and assessed by an ambient vibration test on a continuous box girder bridge. The results demonstrate that the performance of SOBI in modal parameter identification is determined by the quality of the RD data.