Event-based Data Acquisition in Wireless Sensor Networks for Structural Health Monitoring

The inspection of civil engineering structures is mainly conducted visually so far. Therefore, the condition of the structure is examined from the surface and the interpretation and assessment is based on the experience of the expert. However, maintenance costs and lifetime prognosis become more and more important. Different exposures have to be considered, e. g. dynamic and static loads, strains as well as temperature and moisture. The main purpose of monitoring civil structures is not to substitute visual inspection. Continuous structural health monitoring should provide data from the inside of a structure to better understand its structural performance and to predict its durability and remaining life time. Monitoring should render objective data and observable alterations in the structure continuously which cannot be done by visual inspection. Easy to install wireless monitoring systems which use intelligent methods for data acquisition and analysis, could be a competitive alternative and a right step forward to a better understanding of deterioration processes and structural performance. In this paper solutions for event-based monitoring are described that are needed due to the hard- and software restrictions of battery powered wireless sensor networks. Two specific solutions for practical applications of event-based monitoring are presented: i) dynamic strain measurements at a railway bridge during train crossing and ii) acoustic emission analysis methods for the analysis of fracture and deterioration processes of brittle materials.