There is an increasing interest in the vibration data-based detection, localization, and quantification of damage in civil engineering structures exposed to earthquake, wind, and other loads. Early motivation for this was provided by the discovery of hidden damages in steel structures caused by the 1994 Northridge and 1995 Great Hanshin (Kobe) Earthquakes, and also by the fact that structural element are usually inaccessible after construction. Several analytical methods have been proposed in the literature and still more are being developed for this. Currently simulated data are being used to check the effectiveness of these methods; however, their validation and comparison on actual experimentally obtained data is yet to be done. In this exploratory project, it is proposed to experimentally study and validate the effectives of the autoregressive with exogenous input model, wavelet transform, eigensystem realization algorithms (ERA), and subspace identification (SSI) approaches for comprehensive modal and damage identification of civil engineering structures. For damage localization and quantification the flexibility and rotational flexibility matrices with and without and damage locating vectors will be used. Further analytical improvements in these methods will also be made for more reliable damage quantification. The tests will be conducted on a scaled three-story, nine degrees-of-freedom structure model prepared such that its stiffness properties can be changed by planned changes in one or more braces, by sudden removal of one or two braces in real-time using magneto-rheological dampers, and by loosening the connecting hardware at few selected joints. The major cost of preparing this changeable scaled model will be borne by the PIs institution. The scaled model will be excited at its base by the 5' by 5' shaking table at Virginia Tech. The model would also have the capability of being excited by shakers installed at any of the three levels. The dynamic measurements of the acceleration response will be made using ten accelerometers, three placed at each floor level in two orthogonal directions plus one on the table.
The SGER funding is being sought to identify validated damage localization and quantification methods which will be needed in a more comprehensive follow-up study. This follow-up study to be proposed later will develop an integrated system consisting of the validated damage identification techniques with online consequence prognosis followed by online actuation, if necessary, of a control system to maintain the performance of the structure at an acceptable level. The successful outcome of this exploratory work will also be a very useful tool for direct practical implementation in structural diagnostics and health monitoring.
The Intellectual merit of this study is in the development of experimentally verified damage identification (detection, localization, and quantification) schemes for a comprehensive structural health monitoring.
Broader impacts of this research will occur at two levels: the education and training of graduate and undergraduate students and the availability of a much needed tool and data to researchers and practitioners involved in structural health monitoring. A graduate student and an undergraduate student will work on this project. The undergraduate student will be supported through the REU program. She/he will be selected through the Center for the Enhancement of Engineering Diversity (CEED) at Virginia Tech from the pool of available African American, Hispanic, American Indian, and women students. The dissemination of information and data generated in this research to other students, researchers and practitioners will be done through class room teaching, website creation, presentations in conferences, and publications in archival journals and conference proceedings.
