Reinforcement Corrosion Monitoring Of Reinforced Concrete Structures Using Piezoceramic-based Guided Waves

Reinforced concrete(RC)structure is one of the most widely used structural types.However,the durability issue cannot be completely solved,and reinforcement corrosion is one of the important factors leading to premature failure of concrete structures.Before reinforcement corrosions in offshore RC structures happen,the service state of the offshore structure can be understood through regular judgment and evaluation of the cumulative corrosion level and timely adopted repair measures,preventing further development and extension of the damage,enhancing the structural durability,and bringing obvious benefits.In the engineering situation,an effective damage identification(DI)technology and structural health monitoring(SHM)method for offshore engineering are urgently required and become an important field for civil engineering in the future.For the reinforcement corrosion issue in offshore engineering,although the existing DI technology and SHM method can play some functions,they also have some challenges of relatively low accuracy for reinforcement corrosion evaluations,weak practicability,high cost,etc.,being inconvenient for the development of offshore engineering monitoring system.The reason causing the above-mentioned problem may come from the lack of simple and effective DI technology and SHM method which are sensitive to the surface type damages.The ideal reinforcement corrosion DI technology for offshore engineering should meet requirements of cost effective,good detection effect,excellent reconfigurability,wide detection range,no need for a large amount of manpower or mechanical support,etc.The piezoceramic-based guided wave monitoring technology in the dissertation can meet the requirement of the reinforcement corrosion monitoring and evaluate the reinforcement corrosion level with a relatively precise for offshore engineering.Therefore,the dissertation aims at proposing a basic theory and technology for reinforcement corrosion monitoring of RC structures in offshore engineering based on the piezoceramic ultrasonic guided wave(UGW)sensing technology.Through the combination method of theoretical analysis,experiment in laboratory and numerical simulation,the investigation for the reinforcement corrosion monitoring of RC structures in offshore engineering have been done,and the main work are described as following:(1)The advantages and disadvantages of traditional DI and SHM technologies are briefly described,and the main contents and key technologies for the existing issues are proposed.The reinforcement corrosion mechanisms are deeply investigated,the physical and geometrical influencing factors for the corrosion layer are determined,the dispersive property and propagation behavior of UGWs for detection use in layered structures are studied,and key technologies which are applicable to the reinforcement corrosion monitoring such as the optical detection waveforms,actuation frequencies,sensor layout,etc.,are explored.(2)A method for reinforcement corrosion monitoring of offshore RC structures based onpiezoceramic-based UGW sensing technology is proposed.The proposed method can not only reveal the reinforcement corrosion level which is closely associated with the concrete protective layer,but also quantitatively characterize the corrosion layer thickness.(3)Dispersive properties and energy attenuation characteristics of UGWs in the corroded reinforcement are deeply investigated.The finite element method(FEM)is used to study the guided wave propagation mechanism in layered medias and establish a quantitative relationship between reinforcement corrosion levels and sensing signal properties.(4)The electric accelerated corrosion test is applied to monitor the entire corrosion process.Corrosion influencing factors causing changes of UGW propagation performances are extracted.A reinforcement corrosion damage identification index and an evaluation method based on sensing signal energy changes are proposed.A quantitative relationship between the reinforcement corrosion layer thickness considering the influence of different concrete protective layers and sensing signal energy changes is preliminarily established.The results show that the proposed UGW-based reinforcement corrosion monitoring method for RC structures has properties of practical convenience,cost effectiveness,wide detection range,high detection precision,etc.,and meets requirements of reinforcement corrosion monitoring of RC structures.