A Process Control System for the John F. Kennedy Memorial Bridge

During a routine inspection in 2006 of the John F. Kennedy Memorial Bridge (a cantilever through-truss bridge which carries I-65 across the Ohio River at Louisville, KY), a failed anchor bolt was identified in an uplift bearing assembly. A retrofit consisting of a replacement anchor bolt and clamp-down anchors ("keepers") was installed in the fall of 2007. Since this installation, the Infrastructure Technology Institute at Northwestern University has monitored the following quantities in the retrofit system: 1. Axial strain in replacement anchor bolt 2. Bending strain in replacement anchor bolt (two orthogonal directions) 3. Torsional strain in replacement anchor bolt 4. Axial strain in existing intact anchor bolts 5. Force on keepers (four total) 6. Displacement and acceleration of bearing assembly relative to pier (three directions) 7. Ambient temperature and relative humidity This system has continuously monitored the condition of the repaired bearing assembly, and was able to detect an abrupt failure in one of the components of the retrofit in the fall of 2008. This failure resulted in immediate and obvious changes to the stream of data collected by the system. However, there is a need for techniques to monitor long-term trends in condition, which may be subtle and not immediately obvious upon reviewing the raw data. The work proposed herein is, therefore, to develop and implement an automatic system to process and analyze the data that are collected. The objectives are to: (1) Allow engineers to make inferences about the structural integrity, i.e., the condition, of the elements, and how they evolve over time in response to normal operating factors such as weather, traffic loading, etc. (2) Detect external events that may have either a transitory or permanent effect on the structural integrity of the bridge elements and how the evolve over time. In both cases the goal is to support decisions to inspect the components when structural deficiencies are either anticipated due to regular deterioration, or directly related to external events. In terms of connections to the USDOT's research goals, the proposed work involves development and implementation of cutting-edge, transformative research tools to support information management, and decisions related to the management/renewal of surface transportation infrastructure. The project also points out that the work is complementary to ITI's work/expertise in developing advanced remote monitoring systems.