TDR 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. On the connection, relative movement between members causes load redistribution or even failure. Monitoring the integrity of the structural system can assure its performance and safety. TDR monitoring system is proposed here to be a multiple points monitoring system using only one coaxial cable as the sensing and conducting media all the way through the monitored structure. The cable is fixed at both end of each pairs of adjacent members to be the sensing device along itself. Relative movements between each member at the connecting points are monitored simultaneously by sending a fast rise impulse into the cable. When lateral movement applied, the cable will deform and having the effect of adding an equivalent capacitance at that point and causing the signature to jump up. And, the most important ability for TDR system is the location of the relative movement along the cable is very clearly shown in the time domain signature. The pulse of a TDR tester can go a few thousands feet which gives enough monitoring range for most infrastructure.