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USF / FDOT Remote Monitoring of Bridges

Cathodic Protection Systems for Alligator Alley Bridges


Project Details

This project entails a 24-month study in which the performance of cathodic protection systems of steel piles in two bridges have been remotely monitored. The main objectives were to design, implement, and demonstrate: (1) a reliable set of sensors to monitor the anode environment (most critically the water resistivity) and operation as needed, (2) an adequate self-powered remote monitoring system/scheme integrated with the CP monitoring system already in place at FDOT, (3) criteria for changing anode connectivity, circuitry, or material type, and (4) a device capable of implementing the logic (from criteria above) for automatic or manual anode or circuitry switching.

Two bridges, 860050 and 860054, located on the “Alligator Alley” toll portion of I-75 in Broward County, Florida were slated for monitoring. Each bridge had two piers inside a drainage canal. The resistivity of the water in the canals was known to vary seasonally. The piers had seven steel H-piles each that were jacketed in concrete to a level just below the surface of the water. Cathodic protection was provided by three magnesium anodes spaced uniformly over the length of each pile.

A remote monitoring system was developed that used solar power and remote communication. The system was designed to evaluate both pier to pier (RF) and long distance data transmission (cellular). Commercially available sensors monitored temperature, humidity, water resistivity, anodic current and steel potential. A Campbell Scientific data acquisition system was installed to record data that was periodically transmitted to the USF campus via cellular network. A website mimicking the FDOT web layout was updated regularly with the remotely collected data and provided information to interested parties.

A relay system was developed to remotely disconnect anodes and conduct remote de-polarization tests. Various configurations of the relay-based switching system were developed to regulate anodic current and polarization. This system will be handed over to FDOT following completion of the study.

Water quality measurements confirmed that 9 months of the year magnesium anodes were appropriate whereas from January through March more than adequate cathodic protection was applied. It is in these months that increases in the shunt resistance (controlled by remote relay switching) are proposed to regulate current and minimize needless anode consumption.


Alligator Alley Bridge Data

  • Bridge 860050 Graphs


  • Bridge 860054 Graphs


  • Bridge 860050 Monthly Data


  • Bridge 860054 Monthly Data


  • Bridge 860050 Video Files


  • Bridge 860054 Video Files