Triggering instrumentation for autonomous monitoring of load-induced strain is described for economical, fast bridge
inspection. The development addresses one aspect for the management of transportation infrastructure - bridge
monitoring and inspection. The objectives are to provide quantitative performance information from a load test, to
minimize the setup time at the bridge, and to minimize the closure time to traffic. Multiple or networked measurements
can be made for a prescribed loading sequence. The proposed smart system consists of in-situ strain sensors, an
embedded data acquisition module, and a measurement triggering system. A companion control unit is mounted on the
truck serving as the load. As the truck moves to the proper position, the desired measurement is automatically relayed
back to the control unit. In this work, the testing protocol is developed and the performance parameters for the triggering
and data acquisition are measured. The test system uses a dedicated wireless sensor mote and an infrared positioning
system. The electronic procedure offers improvements in available information and economics.
Field instrumentation is investigated on an in-service highway bridge over a 2-year period. Extrinsic Fabry-Pérot interferometric (EFPI) strain sensors provide a permanent health-monitoring capability. The bridge is a reinforced-concrete (RC) structure that was repaired and strengthened using fiber-reinforced-polymer (FRP) wraps. A sensor network monitors the load-induced strain in the FRP reinforcement and the steel rebar. Colocated electrical resistance strain gauges and a finite element analysis are used for comparison. Both dynamic and static load characteristics are analyzed for a near-capacity truck. The fiber optic measurements are generally consistent with the comparison measurements and the analytical results; and they show no failure or degradation as opposed to the electrical resistance gauges. We demonstrate the implementation and the performance of in situ EFPI sensors in a long-term field environment. Embedded fiber optic sensors can provide the required information for the intelligent management of a transportation infrastructure.
KEYWORDS: Device simulation, Analog electronics, Sensors, Control systems design, Control systems, Simulink, Vibration isolation, Actuators, Smart structures, Amplifiers
This paper provides an account of a student research project conducted under the sponsoring of the National Science Foundation (NSF) program on Research Experience for Undergraduates (REU) in Mechatronics and Smart Strictures in the summer of 2000. The objective of the research is to design and test a stand-alone controller for a vibration isolation/suppression system. The design specification for the control system is to suppress the vibrations induced by the external disturbances by at least fiver times and hence to achieve vibration isolation. Piezo-electric sensors and actuators are utilized for suppression of unwanted vibrations. Various steps such as modeling of the system, controller design, simulation, closed-loop testing using d- Space rapid prototyping system, and analog control implementation are discussed in the paper. Procedures for data collection, the trade-offs carried out in the design, and analog controller implementation issues are also presented in the paper. The performances of various controllers are compared. The experiences of an undergraduate student are summarized in the conclusion of the paper.
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