ABSTRACT
In this study, the authors investigate the strain caused by the release of residual stress introduced by welding when fatigue cracks initiate and propagate. The change in the strain under the unloading condition due to fatigue crack initiation and propagation is verified via fatigue tests performed on an out-of-plane gusset joint. Subsequently, to measure and transfer the strain under the unloading condition in actual bridges, the authors create a data logger device using a single-board computer equipped with an Internet-of-Things system. The abovementioned fatigue tests are performed using the developed logger device. The measured strains are transferred via a low-power wide-area network and monitored on an Internet platform. Using the proposed system, the strains can be monitored periodically to capture fatigue crack initiation and propagation via the Internet platform.
