| A significant amount of the nation's highway bridges are functionally obsolete or structurally deficient. The deficient structures represent significant impediments to safe and economical use of the highway system. This in turn results in safety hazards, higher user costs, and huge outlays for preservation and replacement. The complexities and costs associated with preserving the nation's bridge infrastructure demand innovative approaches to experimental and analytical studies, collection and analysis of data and prediction of current and future bridge preservation actions. These needs, coupled with the availability of modern analytical methods and high-speed computers, are leading to the development of new technologies and an interdisciplinary approach to the problem. Since civil infrastructure system (CIS) problems are related to financial, legal, organizational, political and societal as well as technical issues, the nature of the problem is more complex than it appears. Therefore, global condition assessment by utilizing new technologies is of major importance for decision making in respect to CIS problems.; A major contribution to bridge condition assessment and structural damage identification will be the development of the tools and methods necessary for optimum infrastructure management in the 21{dollar}sp{lcub}rm st{rcub}{dollar} Century. This research was designed to evaluate the success of different concepts, experimental approaches, algorithms, and hardware/software tools for condition assessment, by detecting various types and levels of damage and repair which were induced in a decommissioned bridge. Utilization of experimental modal analysis methods for condition assessment and structural damage identification methods are investigated. The improved parameter estimation methods are established such that the civil infrastructure can be reliably tested and the modal data can be post-processed. A comparative study on the results of the different damage states of the bridge is presented. The bridge was tested before and after the different damage scenarios. Frequency response functions, measured at different spatial locations, are used to post-process the data using the spatial domain algorithm, Complex Mode Indicator Function. This algorithm which is implemented for parameter estimation of the multi-reference impact test data of the bridge, provided very reasonable results. Dynamic properties of the bridge are investigated for the pre- and post-damage cases. Modal flexibility of the bridge is calculated for the measured degrees of freedom. Modal flexibility of the bridge shows good agreement with static instrumentation results under truck loading. Some of the most common damage identification methods are utilized and new methods such as Bridge Girder Condition Indicator, curvature of Bridge Girder Condition Indicator are proposed. |
