Computation of Vehicular-Induced Vibrations and Long-Term Instrumentation Reliability for Structural Health Monitoring of Highway Bridges

Real-time monitoring of fracture critical steel bridges can potentially enhance inspection practices by tracking the behavior of the bridge. Significant advances have occurred in recent years on the development of robust hardware for field monitoring applications. These systems can monitor, process, and store data from a variety of sensors (e.g. strain gages, crack propagation gages etc.) to track the behavior of the bridge. The research outlined in this dissertation is part of a large study focused on the development of a wireless system for use in long-term monitoring of bridges. The wireless monitoring system had a target maintenance-free life of ten years, and independent from the power grid. Thus, the feasibility to harvest energy for the monitoring system is an important step in the development of the system. In addition, the reliability of the sensors in the bridge is very important upon the success of the system. The focus of this dissertation is on two primary aspects of the wireless monitoring system. First, the feasibility to harvest energy from vehicular-induced vibrations is evaluated through analytical models of highway bridges under truck loads. Acceleration results from simple line-element models and detailed finite element models of five steel bridges in Texas and Oregon are compared with actual field data from the same bridges. vii Second, the dissertation also highlights studies on the identification of strain gages and installation procedures that result in long lives. In addition, the effect of temperature fluctuations and other environmental factors on the sensor drift and noise is also considered. In long-term monitoring applications, slight sensor drift and noise can build up over time to produce misleading results. This dissertation presents the results of transient dynamic analyses of bridges under moving truck loading and laboratory tests on gage durability that were conducted as part of a research project sponsored by the National Institute of Standards and Technology (NIST).