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Smart Structures and Systems Volume 20, Number 2, August 2017 , pages 115-126 DOI: https://doi.org/10.12989/sss.2017.20.2.115 |
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Mode identifiability of a cable-stayed bridge using modal contribution index |
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Tian-Li Huang and Hua-Peng Chen
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| Abstract | ||
| The modal identification of large civil structures such as bridges under the ambient vibrational conditions has been widely investigated during the past decade. Many operational modal analysis methods have been proposed and successfully used for identifying the dynamic characteristics of the constructed bridges in service. However, there is very limited research available on reliable criteria for the robustness of these identified modal parameters of the bridge structures. In this study, two time-domain operational modal analysis methods, the data-driven stochastic subspace identification (SSI-DATA) method and the covariance-driven stochastic subspace identification (SSI-COV) method, are employed to identify the modal parameters from field recorded ambient acceleration data. On the basis of the SSI-DATA method, the modal contribution indexes of all identified modes to the measured acceleration data are computed by using the Kalman filter, and their applicability to evaluate the robustness of identified modes is also investigated. Here, the benchmark problem, developed by Hong Kong Polytechnic University with field acceleration measurements under different excitation conditions of a cable-stayed bridge, is adopted to show the effectiveness of the proposed method. The results from the benchmark study show that the robustness of identified modes can be judged by using their modal contributions to the measured vibration data. A critical value of modal contribution index of 2% for a reliable identifiability of modal parameters is roughly suggested for the benchmark problem. | ||
| Key Words | ||
| cable-stayed bridge; operational modal analysis; dynamic characteristics; modal contribution index; ambient vibration response | ||
| Address | ||
| Tian-Li Huang: School of Civil Engineering, Central South University, Changsha, Hunan Province, 410075, China; Department of Engineering Science, University of Greenwich, Chatham Maritime, Kent, ME4 4TB, UK Hua-Peng Chen: Department of Engineering Science, University of Greenwich, Chatham Maritime, Kent, ME4 4TB, UK | ||