Experimental Analysis of a Nondestructive Corrosion Monitoring System for Main Cables of Suspension Bridges

Abstract

Corrosion of high-strength steel wires in a suspension bridge’s main cable has been attributed to the environment within the cable wrapping. A sensor network was developed to monitor and provide information in order to indirectly assess the environmental conditions and the deterioration of the interior of suspension bridge main cables. The overall functionality of both the individual sensors and the monitoring system was tested on a full-scale mock-up cable. The cable mock-up was covered in aluminum wrapping and an environmental chamber was built around it in order to subject the test specimen and sensor network to an aggressive corrosive environment created by cyclic temperature and humidity conditions. The temperature, relative humidity (RH), and corrosion rate levels were recorded by all sensors. The recorded data were analyzed in an attempt to determine general trends and correlations between the environmental variables themselves and their effects on corrosion rates. The recorded temperature fluctuations were highly dependent on the sensor depth within the cable; however, the RH levels were not. During cyclic testing, near-linear temperature increases and RH decreases were recorded close to the cable’s center. The baseline corrosion rate levels were affected by the RH levels, with significant increases in corrosion rates at RH levels greater than 50%. The temperature changes proved to impact the corrosion rates on a cyclic level, with high correlations between the temperature and corrosion rate readings recorded by linear polarization resistance corrosion rate sensors.