Insufficient information on existing bridge substructures and foundations poses significant challenges for structural condition evaluation and can cause significant uncertainties for the safety and serviceability of bridges. Characterization and condition evaluation of bridges substructure and foundations will not only help to decrease the vulnerability to natural hazards but also provide opportunities for their reuse with considerable benefits. In this paper, the feasibility of leveraging structural identification techniques to characterize bridge substructures and foundations is investigated. A three-span simply supported bridge located in Mossy, West Virginia, USA, is used as a study case. Modal analysis and finite element model updating techniques are used to investigate and estimate the uncertainties and conditions of the substructure. Updated finite element model for this structure provides valuable information for bridge condition assessment and proves how structural identification is a viable tool for the case considered.

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Although the widely acknowledged shortcomings of visual inspection have fueled significant advances in the areas of non-destructive evaluation and structural health monitoring (SHM) over the last several decades, the actual practice of bridge assessment has remained largely unchanged. The authors believe the lack of adoption, especially of SHM technologies, is related to the 'single structure' scenarios that drive most research. To overcome this, the authors have developed a concept for a rapid single-input, multiple-output (SIMO) impact testing device that will be capable of capturing modal parameters and estimating flexibility/deflection basins of common highway bridges during routine inspections. The device is composed of a trailer-mounted impact source (capable of delivering a 50 kip impact) and retractable sensor arms, and will be controlled by an automated data acquisition, processing and modal parameter estimation software. The research presented in this paper covers (a) the theoretical basis for SISO, SIMO and MIMO impact testing to estimate flexibility, (b) proof of concept numerical studies using a finite element model, and (c) a pilot implementation on an operating highway bridge. Results indicate that the proposed approach can estimate modal flexibility within a few percent of static flexibility; however, the estimated modal flexibility matrix is only reliable for the substructures associated with the various SIMO tests. To overcome this shortcoming, a modal 'stitching' approach for substructure integration to estimate the full Eigen vector matrix is developed, and preliminary results of these methods are also presented.

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