Crack Sensor Using Commercial UHF RFID Technology for Metallic Structures

Many in-service steel bridges rely on the successful load transfer between critical members at connections. These connections often have high stress concentrations that make a way for crack propagation, resulting in a reduction in load capacity. Thus, detecting cracks in the connections on a steel girder bridge in a timely manner is of paramount importance. To date, visual inspection has been the principal method for detection of cracks. Recently, monitoring methods using in-house radio frequency identification (RFID)-based crack sensors or other patch-type sensors have been developed to complement visual inspection with quantitative damage information. However, their application in the field is costly. On the other hand, commercial ultra-high frequency (UHF) passive RFID tags offer similar properties at a more viable cost. This paper presents a development of a new crack sensor for metallic structures using commercial passive RFID technology. This sensor uses backscatter power as the main damage identification parameter. A new method for crack propagation testing was designed to evaluate the performance of any backscatter power-based crack sensor to monitor propagating cracks on a metallic surface using plate specimens designed for standard fracture toughness testing. Crack and fracture mode characteristics were determined with high precision using digital image correlation and high-resolution photography. The development and performance evaluation of this commercial RFID-based crack sensor contributes to the advancement of this technology for steel girder bridge monitoring.