Life-Cycle Design And Optimization Of Concrete Structures With Reinforcement Corrosion

In recent years,concrete structures have been widely used in the engineering field,especially more and more bridges and marine structures.The durability problems of concrete structures in harsh environments has brought a heavy financial burden to many countries in the world.Therefore,the project about how to design the concrete structures in harsh service environment and optimize the life-cycle cost has attracted more and more attention from engineering and academia.This research is funded by the National Natural Science Foundation of "The study of concrete Structure durability of whole life performance and design theory based on Steel Corrosion(51378241)".In this paper,the life-cycle cost analysis and calculation system is discussed.And the mechanism of the life-cycle durability deterioration process of the concrete in the chloride erosion environment is also studied.The main work in this paper includes:1.The corrosion process and the concrete performance degradation process are discussed.In this paper,the process of corrosion reaction in concrete is discussed and several limit states are defined and predicted.From the initial corrosion of steel bars to the formation and development of concrete rust cracks,this paper discussed the process of corrosion of concrete in natural erosion environment.The effect of corrosion on normal performance of concrete structures were also put forward.The mechanical properties of the corroded steel bars were studied by using the corrosion steel bars obtained by the dry and wet cycle erosion test in the long term natural environment.The effect of the corrosion of the steel bars on the bearing capacity of the concrete structure was reflected.It was fully explained that using the whole life cycle theory to optimize the concrete structure design has practical significance and research value.2.Calculation and analysis framework of life-cycle cost of concrete structures are established.The optimization method given by the international standard(ISO 2394,1998)is used as the function to establish the operation model by the reliability theory,and the optimization method of the minimum life-cycle cost is discussed.In this paper,the life-cycle cost analysis model includes the construction cost,the daily maintenance cost,the maintenance and reinforcement cost,the failure cost and the value of surplus are established by using probability analysis theory.On the basis of this study,the optimization method of durability design of concrete structure is discussed,and the idea of parameter selection with minimum life-cycle cost is put forward,so as to guide and optimize the durability design of reinforced concrete structure.3.Life-cycle time-dependent reliability of concrete structures in chloride environment.In order to predict the life cycle degradation process of concrete structures in the environment of chloride salt erosion,this study divided the life cycle into chlorine transport stage and longitudinal fracture development stage.Based on the existing model of chloride transport in concrete and the longitudinal cracking width prediction model,this paper applied Monte-Carlo sampling method to obtain the time-dependent failure probability and reliable index curve under different design conditions.By comparing the results of time-dependent curve of concrete under different design conditions,this paper discussed how to optimize the life cycle design of concrete structure under the corrosion environment of steel bar.4.The life-cycle design method of concrete structure in chloride erosion environment is studied.Based on the time-dependent reliability curve under different design conditions,this study explored the influence of maintenance and reinforcement activities on the reliability index,and established the different operation stage maintenance and reinforcement activities Calculation Method of Cost Calculation in Operation Period.In this paper,the concrete structure in the actual marine environment as an example to calculate the life cycle of the operation phase of the maintenance and reinforcement activities cost.Based on the comparative analysis of the operating cost calculation results,this paper explores the theoretical method of the whole life cycle cost optimization of concrete structures under the condition of steel bar corrosion.Finally,this paper tried to improve the design method of concrete mix with the optimization of green performance.