Research On Steel Corrosion Monitoring Experiment By Fiber Optic Sensing Technique And Numerical Analysis

Steel corrosion is the main reason for the durability failure of concrete structure.Numerous reinforced concrete structures are repaired,demolished because of steel bar corrosion, which causes enormous losses. Structural health monitoring has become a key factor in the operational security of major engineering structures. Optical fibre presents many advantages, such as anti-interference ability, resistance to corrosion. Optical fiber sensing technology has been widely applied in structural health monitoring over the recent years. This technology is expected to overcome the defect of traditional steel bar corrosion monitoring method and its application urgent needs to be improved in this field.This paper studied monitoring experiment of steel corrosion in concrete based on optical fiber sensing technology and numerical simulation of concrete cover cracking due to steel corrosion. This paper mainly focuses on works as follows:The basic principle of white light optical fiber deformation measuring instrument based on Michelson interferometer, and a kind of steel corrosion sensor was designed using this technology was illustrated. By mean of constant power-accelerated corrosion, two steel corrosion monitoring testing programs were designed respectively, which tested steel corrosion expansion circumferential strain before and after concrete cover cracking respectively. Meanwhile, the development of crack width after cracking was measured during the experiment.The experiment showed that white light optical fiber deformation measuring instrument can be adopted to monitor slight deformation. The experiment verified that the steel corrosion monitoring sensor can be implemented in whole life-circle quantitative monitoring of steel corrosion in reinforced concrete. Moreover, this sensor has characters of high precision and sensitivity. This paper concluded that thicker concrete cover can effectively extend cracking time of concrete cover due to steel corrosion and the development trend of monitoring strain and crack width of concrete are similar.According to concrete plasticity damage model in Abaqus, the micro crack development process of concrete cover due to steel corrosion expansion was simulated and compared with steel corrosion expansion experiment before concrete cover cracking. It can be analyzed that the simulation results is consistent with the experimental results of circumferential strain when concrete cover cracking. In addition,developing position of concrete cover’s micro-cracks during experiment can be determined through simulation.Using radial displacement and circumferential strain as indicators when concrete cover cracks. To discuss main factors affecting uniform and non-uniform steel corrosion,three variables were analyzed which are concrete cover thickness, concrete strength and reinforcement diameter. The paper holds that circumferential strain is better than the radial displacement as an indicator to judge the extent of steel corrosion. It can be concluded by numerical analysis of uniform and non-uniform steel corrosion that the value of circumferential strain,when concrete cover cracks, increases with the increase of tensile strength of concrete, the increase of cover thickness and relative cover thickness and increases with the decrease of bar diameter. Under the non-uniform steel corrosion,as tiie tensile strength of concrete increases, the slope of the relationship between liie circumferential strain and the relative cover thickness is greater.