A multiscale wireless sensor system is designed for vibration-and impedance-based structural health monitoring. In order to achieve the objective, the following approaches are implemented. Firstly, smart sensor nodes for vibration and impedance monitoring are designed. In the design, Imote2 platform which has high performance microcontroller, large amount of memory, and flexible radio communication is implemented to acceleration and impedance sensor nodes. Acceleration sensor node is modified to measure PZT's dynamic strain along with acceleration. A solar-power harvesting unit is implemented for power supply to the sensor system. Secondly, operation logics of the multi-scale sensor nodes are programmed based on the concept of the decentralized sensor network. Finally, the performance of the multi-scale sensor system is evaluated on a lab-scale beam to examine the long-term monitoring capacities under various weather conditions.

In this paper, a method for identifying the loss of prestressing force (prestress-loss) in the cable-anchorage system of prestressed concrete structures using the impedance responses and artificial neural networks (ANNs) is developed. First, theories of impedance responses and damage detection methods for diagnosing the occurrence and the severity of prestress-loss are presented. In which, the occurrence of prestress-loss is determined by MAPD (Mean Absolute Percentage Deviation) index. Then, the severity of the prestress-loss is determined by ANNs. The feasibility of the developed method is verified by numerical simulations for a real cable-anchorage system with different levels of prestress-loss. The reliability of the numerical simulations for impedance responses is evaluated by comparison to experimental results. Finally, the occurrence and severity of the prestress-loss are exactly identified by the proposed method. The results of this study show that the proposed method is highly effective in determining the prestress-loss in the cable-anchorage system

In this paper, the applicability of a smart sensor system for structural health monitoring (SHM) is evaluated on a full-scale cablestayed bridge. Firstly, vibration responses of pylon-cable-deck system in cable-stayed bridge are described. Secondly, an Imote2-based smart sensor system is designed for the vibration-based SHM. Finally, the practicality of the smart sensor system is evaluated on a real cable-stayed bridge, Hwamyung Bridge in Korea. The field-test bridge is briefly described and the field sensor deployment is outlined. The long-term monitoring performance of the sensor system is examined under various weather conditions. The experimental modal parameters of the target bridge are identified by numerical modal analyses. The accuracy of cable force monitoring by the sensor system is evaluated for the target bridge.