Innovative technology for continuous fatigue crack condition monitoring of bridges: long-term electrochemical fatigue sensor (LTEFS)

摘要

A 2001 study by the US Federal Highway Administration (FHWA) determined that over 90% of fatigue cracks on bridges are missed using conventional methods. Moreover, of those indications that are identified by inspectors as fatigue cracks, 80% are false positives. Fatigue cracks are commonly found at the fatigue-susceptible locations on bridges, such as wrap-around welds, coping angles with sharp radii and welded connections that are subjected to out-of- plane bending. Understanding the growth of these fatigue cracks is critical to the safety and reliability of transport infrastructure. However, modelling fatigue in bridges is difficult due to the nature of the loading and variations in the connection integrity. When fatigue cracks reach critical lengths, failures occur, causing partial or full closures, emergency repairs and even full structural failure, particularly in fracture-critical bridges. These types of failure occur every 10 days in the USA, according to the Texas Transportation Institute. Given the notoriously ageing USA highway bridge system and the insufficiency of relying on modelling, the need for reliable, cost-effective sensors and monitoring technologies to alert bridge owners when fatigue cracks are growing is higher than ever. The electrochemical fatigue sensor (EFS™) method, developed in the early 1990s, has proven itself to be valuable and quite practical for the timely detection of growing fatigue cracks and in the verification of retrofits through dynamic testing and inspection. Further development of EFS-based systems over the last two decades has resulted in a robust non-destructive testing method, which has recently been adapted to accommodate long-term condition monitoring and structural health monitoring. This paper will detail the science behind the EFS method, case studies utilising the inspection and dynamic testing system and the field testing recently completed utilising the long-term electrochemical fatigue sensor (LTEFS)-based system.