In recent years, there has been an increasing interest in the adoption of emerging sensing technologies for instrumentation within a variety of structural systems. Wireless sensors and sensor networks are emerging as sensing paradigms that the structural engineering field has begun to consider as substitutes for traditional tethered monitoring systems. A benefit of wireless structural monitoring systems is that they are inexpensive to install because extensive wiring is no longer required between sensors and the data acquisition system. Researchers are discovering that wireless sensors are an exciting technology that should not be viewed as simply a substitute for traditional tethered monitoring systems. Rather, wireless sensors can play greater roles in the processing of structural response data; this feature can be utilized to screen data for signs of structural damage. Also, wireless sensors have limitations that require novel system architectures and modes of operation. This paper is intended to serve as a summary review of the collective experience the structural engineering community has gained from the use of wireless sensors and sensor networks for monitoring structural performance and health.

http://www-personal.umich.edu/~jerlynch/papers/SVDReview.pdf

A summary review of wireless sensors and sensor networks for structural health monitoring

Staff members at Los Alamos National Laboratory (LANL) produced a summary of the structural health monitoring literature in 1995. This presentation will summarize the outcome of an updated review covering the years 1996 2001. The updated review follows the LANL statistical pattern recognition paradigm for SHM, which addresses four topics: 1. Operational Evaluation; 2. Data Acquisition and Cleansing; 3. Feature Extraction; and 4. Statistical Modeling for Feature Discrimination. The literature has been reviewed based on how a particular study addresses these four topics. A significant observation from this review is that although there are many more SHM studies being reported, the investigators, in general, have not yet fully embraced the well-developed tools from statistical pattern recognition. As such, the discrimination procedures employed are often lacking the appropriate rigor necessary for this technology to evolve beyond demonstration problems carried out in laboratory setting.

A review of structural health monitoring literature 1996-2001

Technology developments in structural health monitoring of large-scale bridges

Metal hydride hydrogen compressors: A review

A review of chemical heat pump technology and applications

Compressor-driven metal-hydride heat pumps

Development of LaNi5/Cu/Sn metal hydride powder composites

Performance of high power metal hydride reactors

The magnetic characteristics of ferromagnetic steels, such as hysteresis loops, total permeability and differential permeability, are dependent on mechanical stress and temperature. This dependency can be the basis for a sensitive and non invasive sensing method for measuring the active stress in steel tendons and cables. This paper describes the current status of a stress sensor which can reliably monitor stress in tendons and cables. A transient magnetic field generated by a solenoid is utilized to bring the material to technical saturation. The induced voltage, which is affected by the presence of the ferromagnetic material, is measured and related to material characteristics. In order to obtain a stable and linear calibration curve between permeability and monitoring stress for a given material, an optimal applied field H0 must be determined. Initially, this field is estimated from the measured relationship between permeability and input voltage. The optimal working point is determined by searching for a linear relationship between permeability and applied stress at different temperatures. Temperatures from -20 C to 40 C were used. Experimental results for two common tendons, at two sizes (0.5' and 0.6'), were investigated using this technique. The results were demonstrated to match the accuracy and repeatability of a reference load cell for loading up to 70% of the yield stress. Additional tests were conducted on multi-strand cable assemblies. The experimental results indicate that the calibration procedure can be extended without significant error to accommodate such assemblies.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

George M. Lloyd

Papers

Compressor-driven metal-hydride heat pumps

Development of LaNi5/Cu/Sn metal hydride powder composites

Performance of high power metal hydride reactors

Magnetoelastic permeability measurement for stress monitoring in steel tendons and cables

Thermal analysis of the Ca0.4Mm0.6Ni5 metal–hydride reactor