Structural health monitoring in civil engineering - Applications using wireless sensor networks

Maintenance costs and lifetime prognosis of bridges become more and more important. Due to higher traffic and the increase in axle loads more detailed information is needed. Different exposures have to be considered, e.g. dynamic and static loads, strains as well as temperature and moisture. On the other hand, the inspection of civil structures and especially of bridges is today mainly done visually. The condition of a structure is examined from the surface and the interpretation and assessment is based on the level of experience of inspection engineers. This process can be significantly improved using modern structural health monitoring techniques. Continuously acquired data allows for a better assessment of a structure's performance and, since it is based on more objective data, and for a more detailed prediction of its durability and remaining life time. Structural health monitoring is an important tool for establishing a more reliable inspection and quality management system. Today, wired systems are widely used in structural health monitoring of civil structures. However, they are relatively expensive, vulnerable and time consuming to install. In contrast, wireless monitoring systems are easily installed and operated. In this paper, the basic principles of wireless sensor networks are presented. This monitoring system is equipped with conventional and Micro-Electro-Mechanical-Systems (MEMS), which can be easily installed in different structures. MEMS sensors combine electrical and mechanical components and form the heart of motes (network nodes). Sensor networks equipped with such motes will soon be available for a very low budget. Using this technique, monitoring of large civil engineering structures becomes very cost efficient. Problems that still need to be solved include details of the network configuration, power consumption, data acquisition and data aggregation, signal analysis and data reduction.