Research On Durability Maintenance And Management Methods Of Marine Concrete Structure In Chloride Environment

The application of concrete structures in the chloride salt environment,especially in the marine environment,is more and more extensive,and with it comes the outstanding durability problem.In order to prolong the service life of the concrete structure in the chloride environment and reduce the economic and social costs caused by the failure of the structure in the later period,it is necessary to maintain and manage the concrete structure to delay the negative impact caused by the harsh environment as much as possible.Therefore,the maintenance and management of concrete structures in view of the durability of the chloride salt environment has become a research hotspot in the field of civil engineering.This subject is funded by the National Natural Science Foundation of China's “Research on the Technology and Design Theory of Durability Improvement of Offshore Prestressed Concrete Structures(51778272)”.For the concrete structure in the marine environment,the durability of the concrete structure represented by the chloride salt is established.The main research contents are as follows:1?The degradation mechanism of concrete structure under the chloride salt environment is studied,and the probability analysis of durability life is carried out in combination with actual engineering.The mechanism analysis of the different degradation stages of the concrete structure under the chloride salt environment is carried out,combined with domestic and foreign literature,the different stages of corrosion models are obtained,and the corresponding durability limit state equations are established.Taking the actual project of Lianyungang Wharf as an example,combined with the long-term inspection data of the research team and domestic and foreign documents,the statistical characteristics of the model parameters in accordance with the initial stage of corrosion of the Lianyungang Wharf environment are obtained.Taking the debuffing of the steel protective layer and the cracking of the concrete protective layer as the durability limit states,the probability analysis of the durability life of the concrete structure of Lianyungang Wharf was carried out,and the thickness of the protective layer,chloride ion diffusion coefficient,marine environment,temperature,and corrosion current were studied.The influence of factors such as density on the durability of concrete structures.2?Established a concrete structure maintenance and management framework for the environmental durability of chloride salt erosion.The framework includes durability evaluation,durability index testing,and maintenance strategies.A durability evaluation method combining qualitative fuzzy comprehensive evaluation and reliability-based durability probabilistic analysis is proposed.The overall structure is fuzzy comprehensively evaluated and then the components are subdivided for probability evaluation of durability reliability.A two-layer fuzzy comprehensive evaluation model with durability index as the secondary index is established,and the weight is obtained through the fuzzy analytic hierarchy process.A qualitative durability evaluation was carried out on the Lianyungang Wharf example,which was consistent with the actual appearance of the inspection,and verified the usability of the multi-level fuzzy comprehensive evaluation model.Establish a maintenance event tree to link the deterioration state of the concrete structure under the chloride salt corrosion environment with the maintenance measures.Taking the actual project in Lianyungang as an example,the practicability of the established concrete structure maintenance and management framework is verified.3?The optimization of the maintenance and management of the concrete structure under the chloride environment is studied.A degradation model of a reliable indicator of the durability of concrete structures under chloride salt erosion was established,and the availability of the high-order nonlinear model was verified through actual engineering.Considering the optimization of use-based preventive maintenance and condition-based preventive maintenance,a multi-objective optimization model is established with the goal of maximizing durability reliability indicators and accumulated maintenance costs,and a multi-objective optimization algorithm based on genetic algorithm is used to solve the problem,to get the optimal first maintenance time and maintenance interval.Finally,the actual project was optimized for preventive maintenance management.The maintenance management framework of concrete structures includes the degradation process of concrete structures in the environment of chloride salt erosion,combined with the overall durability of concrete structures based on fuzzy comprehensive comprehensive evaluation(qualitative)and concrete structural components based on durability reliability(quantitative)Evaluation,actual concrete structure inspection based on durability indicators,and selection of maintenance measures based on the maintenance time tree.Finally,the maintenance management plan of the concrete structure under the chloride salt environment is optimized to obtain the optimal maintenance time point,striving to make practical references to actual projects.