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Wireless Sensors for Structural Health Monitoring
With traditional cable-based monitoring systems expensive and labor-intensive to install, wireless sensor networks are emerging as viable substitutes. Using state-of-the-art embedded system technologies, low-cost wireless sensors are designed with hardware and software optimized for structural health monitoring applications. Recent prototypes include powerful microcontrollers for local data processing. To broaden the role of wireless sensors, recent laboratory prototypes integrate actuation interfaces to command PZT active sensors for detection of structural cracks. Currently, wireless active sensing prototypes are being explored for use in decentralized structural control systems.



Field Deployments of Wireless Monitoring Systems
To validate the performance of wireless sensing unit prototypes in realistic civil structures, validation studies are routinely performed on bridges. In collaboration with researchers from Los Alamos National Laboratory, the Alamosa Canyon Bridge was instrumented with MEMS accelerometers and wireless sensors. More recently, the Guemdang Bridge in South Korea was instrumented with a dense network of fourteen wireless sensing units jointly designed by researchers at the University of Michigan and Stanford University. Instrumentation of the Guemdang Bridge was in collaboration with researchers at the Korea Advanced Institute of Science and Technology.



Micro- and Nanoelectromechanical System Sensors
To design novel sensors to monitor the response of structures, the powerful tools of microelectromechanical systems (MEMS) are utilized to minaturize micrometer sized sensing elements in silicon substrates. In particular, MEMS accelerometers are designed, fabricated and validated. Recent research is exploring tools to create novel materials at the nano-scale to achieve desirable mechanical-electrical properties. Applications for such materials includes a variety of structural sensor types such as strain and corrosion sensors.



Self-Sensing Properties of Cementitious Materials
Cementitious materials are natural piezoresistors whose electrical resistance changes in linear proportion with strain. Lab researchers in collaboration with the Advanced Civil Engineering Materials Research Laboratory, are exploring the piezoresistive properties of engineered cementitious composites (ECC), a new high-performance fiber reinfoced cementitious composite, to monitor ECC structural elements.



Decentralized Algorithms for Smart Structures
As smart structure technologies, including structural control and wireless sensing, continues to mature, these advanced devices will continue to reduce in size and cost. With potentially hundreds of sensors and actuators within a single structure, there is a pressing need to advance algorithms that can be deployed in a distributed fashion through out the smart structure system. For structural control, decentralized control algorithms like market-based control are being advanced. In addition, damage detection algorithms historically executed in a centralized data respository, are being modified for autonomous execution within a network of wireless sensor units.



Network for Earthquake Engineering Simulation
Researchers at the Laboratory for Intelligent Structural Technology are integrating wireless sensor networks on large-scale test specimens tested within the Network for Earthquake Engineering Simulation (NEES) collaboratory. To showcase the ability to integrate wireless sensor networks with local data processing within NEES, slab-column connections constructed of high-performance fiber reinforced cementitious composites (HPFRCC) will be instrumented and tested to failure. Punching-shear failure of the slab-column connections under large displacements will be predicted by the wireless sensor network.


Copyright 2005