MTDR Monitoring Systems for the Integrity of Infrastructures

Most infrastructures are formed by large amount of parts, like members of truss, decks of bridge, and so on. Relative movement including shearing and extension between members causes load redistribution or even failure. Monitoring the integrity of the structural system can assure its performance and safety. MTDR (Metallic Time Domain Reflectometry) is proposed here to be an intelligent monitoring system using one coaxial cable embedded into members as the sensing and conducting media all the way through the monitored structure. Relative movements between each member at the connecting points are monitored simultaneously by sending a fast rise impulse into the cable. This paper presents laboratory measurements necessary to quantitatively interpret the reflected waveform. The type and magnitude of reflected waveform caused by shearing and extension between members were investigated. The interpretive techniques were defined and verified experimentally. Quantification between reflected waveform change and amount of relative movements are achieved and provided.