Fiber Bragg grating (FBG) sensors have been applied to assess strains, stresses, loads, corrosion, and temperature for structural health monitoring (SHM) of steel infrastructure, such as buildings, bridges, and pipelines. Since a single FBG sensor measures a particular parameter at a local spot, it is challenging to detect different types of anomalies and interactions of anomalies. This paper presents an approach to assess interactive anomalies caused by mechanical loading and corrosion on epoxy coated steel substrates using FBG sensors in real time. Experiments were performed by comparing the monitored center wavelength changes in the conditions with loading only, corrosion only, and simultaneous loading and corrosion. The theoretical and experimental results indicated that there were significant interactive influences between loading and corrosion for steel substrates. Loading accelerated the progress of corrosion for the epoxy coated steel substrate, especially when delamination in the epoxy coating was noticed. Through the real-time monitoring from the FBG sensors, the interactions between the anomalies induced by the loading and corrosion can be quantitatively evaluated through the corrosion depth and the loading contact length. These fundamental understandings of the interactions of different anomalies on steel structures can provide valuable information to engineers for better management of steel structures.

Cracking in overlay-strengthened RC structures significantly influences their structural performance; however, the effect of elevated temperatures on cracking behavior remains unclear. This work summarizes the experimental and analytical investigations of flexural crack spacing and crack widths of overlaid reinforced concrete (RC) beams at elevated temperatures. Flexural crack spacing was observed experimentally by conducting four-point bending tests on control RC beams and beams overlaid by polymer cement mortar (PCM) together with steel reinforcements at 20, 40, and 60°C during both exposure and loading. The flexural crack width was measured during testing at 20 and 40°C. The flexural crack spacing and crack width increased with increasing temperature for the same reinforcement ratio in the overlay, whereas the flexural crack spacing and crack width decreased with increasing total area of steel reinforcements in the overlay at the same temperature. Based on the existing models for predicting the average crack spacing of overlaid beams, the bond deterioration of concrete/steel and PCM/steel bonds was incorporated to predict the flexural crack spacing of overlaid beams at elevated temperatures. The flexural crack width at an elevated temperature was predicted by incorporating the flexural crack spacing and the tensile stress of tension reinforcements in both the substrate beam and overlay at the cracked section. Close agreement was obtained between the experimental and predicted values of the flexural crack spacing and width.