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.

This study presents an experimental investigation on the combined effect of mechanical loads and corrosion using the designed polytetrafluoroethylene tube-packaged fiber Bragg grating (FBG) sensors, as to implement long-gauge FBG (LFBG) sensors in corrosion detection practices for structural health monitoring. A simplified LFBG-based sensing model was proposed for strain measurement in terms of the Bragg wavelength change. Correspondingly, a systematic corrosion assessment strategy was developed to estimate corrosion severity and average corrosion rate. Upon this, the experimental study was performed on epoxy-coated steel specimens embedded with LFBG sensors, where the loading, corrosion, and combined loading–corrosion tests were used to explore the effect of mechanical loads on corrosion behavior. Test results revealed that the specimens subjected to combined conditions exhibited more severe corrosion damage. The maximum mass loss was observed to be 1.82 and 2.43 in percentage under individual corrosion and combined loading–corrosion conditions, respectively. Also, the pit depth under combined conditions was found to develop rapidly in the early stage. The pit depth severity ratio was around 0.2–0.8 during the 67 days of exposure, indicating an evident impact of loading on corrosion severity. Furthermore, the maximum average corrosion rate under combined conditions was found to be 5.66 times that under individual corrosion conditions.

Each year, the global cost that is accounted to corrosion was estimated at $2.5 trillion. Corrosion not only imposes an economic burden, when corroded structures are under various loading conditions, it may also lead to structurally brittle failure, posing a potential threat to structural reliability and service safety. Although considerable studies investigated the combined effect of external loads and structural steel corrosion, many of the current findings on synergetic interaction between stress and corrosion are contrary. In this study, the combined effects of dynamic mechanical loads and corrosion on epoxy coated steel are investigated using the distributed fiber optic sensors based on optical frequency domain reflectometry. Experimental studies were performed using the serpentine-arranged distributed fiber optic strain sensors embedded inside the epoxy with three different scenarios including the impact loading-only, corrosion-only, and combined impact loading-corrosion tests. Test results demonstrated that the distributed fiber optic sensors can locate and detect the corrosion processing paths by measuring the induced strain changes. The combined impact loading-corrosion condition showed significantly accelerated corrosion progression caused by mechanical loads, indicating the significant interaction between dynamic mechanical loading and corrosion on epoxy coated steel.

Extreme weather conditions have shown significant impacts on pipeline safety, especially oil and natural gas pipelines. Floods, lightning, and extreme temperatures have been recognized as the most affected reasons for weather-induced pipeline damage. Among them, the extreme air temperatures, either extremely cold or hot, may not induce immediate damage to pipelines but may cause localized corrosion and fractures on pipeline segments impacted by extreme temperatures. Thus, it is of interest to understand how extreme air temperatures would influence the temperature distribution along the pipeline. As most pipelines are buried under soil, the influences of air temperatures on the pipelines are not direct. The property of the soil, the depth of the soil, and the temperature change rate will significantly impact such a temperature penetration. This study investigates and reviews how to convert the air temperature into the temperature distribution on the surface of the pipeline. Such a study can be used for further pipeline risk assessment and prediction.