Spurious mode distinguish by modal response contribution index in eigensystem realization algorithm

摘要

Modal identification process has played an important role for civil engineering structures. Among the identification methods, eigensystem realization algorithm is one of the most popular one. However, the noises in practical environment can influent the effectiveness of eigensystem realization algorithm, which can introduce spurious modes due to the overestimated physical order for the structure. This paper proposes a new index named the modal response contribution index (MRCI) for the eigensystem realization algorithm, which can determine the structural physical order and then distinguish spurious mode more precisely. First, the structural responses are divided into different modal response by the well-known modal superposition theory. Then the square root summation of each modal response is obtained and named as MRCI. A modified stabilization diagram is also presented, which increases the row number of Hankel matrix with the determined order by MRCI. The straight lines formed by the stable points in the modified stabilization diagram designate the structural modal parameters. Finally, one numerical example and the monitoring data of a practical cable-stayed bridge are employed. The results show that the proposed MRCI and modified stabilization diagram can identify the structural physical mode more precisely.