Continuous remote monitoring of structural health for life extension of uplift bearing assembly on large cantilever truss bridge

A situation on a large cantilever through-truss bridge, the John F. Kennedy Memorial Bridge, which carries I-65 over the Ohio River at Louisville, Kentucky, provides significant opportunities for applying innovative health monitoring techniques to transportation infrastructure. One of four anchor bolts restraining an uplift bearing at one end of the bridge fractured as a result of corrosion fatigue; the fracture led to concerns about the continuing safety and serviceability of the compromised bearing assembly. Short- and long-term instrument-based monitoring systems were deployed on the bearing assembly to (a) characterize the behavior of the damaged bearing and its intact counterparts, (b) quantify the load transfer due to the retrofit, and (c) monitor the performance of the retrofit continuously for the long term. The monitoring strategy has been successful on all counts; in particular, during Part 3 the system detected a significant shifting of loads that was later confirmed to correspond to fracture of a threaded rod that had been used to replace the failed anchor bolt; this result showed the utility of continuous remote monitoring in detecting failures between inspections. This paper describes the instrumentation plan and strategies for data acquisition, communication, and autonomous operation used on the bridge. The data and implications for management decisions are also discussed.