Numerical Simulation Of Performance Degradation Law Of Concrete Structures In Marine Environment

Concrete structures serving in the marine environment are often eroded by inorganic salt ions such as chloride ions and sulfate ions.These ions can invade the interior of the concrete and then undergo a series of reactions with the concrete and reinforcing steel materials.After a period of service time,the durability and bearing capacity of these structures will be reduced.Therefore,it is necessary to have a clear understanding of that the structures' performance evolves over time,and the potential risks should be predicted in advance through numerical simulation.In this paper,based on the deterioration law of reinforced concrete materials in the marine environment,the damage model of concrete and rebar is established,and the component model eroded by seawater is established based on Open Sees,and the seismic response of concrete structure is calculated using Pushover and dynamic time history analysis methods.The performance evolution and causes of concrete structures in the marine environment are deeply discussed.The contents are summarized as follows:(1)According to the basic principles of Pushover and seismic fragility based on IDA method,the solution process of calculating the target displacement of the structure and the calculation steps of the structural seismic fragility are given.By compiling the corresponding MATLAB program,the automated post-processing of response data is realized.(2)Based on the diffusion law of sulfate ion and chloride ion in concrete,the time and space distribution law of the two in concrete was obtained by numerical simulation.The relationship between the mechanical properties of concrete and sulfate ion concentration on the section of the member was established by the corrosion strength coefficient;according to the corrosion development characteristics of the steel bar under the chloride ion corrosion,the function of the remaining cross-sectional area of the steel bar with the service time was simulated.(3)An analysis model of eroded concrete columns was established in Open Sees.This model can simulate the characteristics of concrete members' damage and the law of the evolution of the properties of reinforced concrete materials with time.The performance of column members under different working conditions was analyzed,besides,the changes in mechanical properties such as compressive strength,flexural bearing capacity and corresponding stiffness,elastoplastic deformation capacity and hysteretic performance of the members after erosion were investigated.(4)Taking a five-story concrete plane frame with a bottom layer immersed in seawater as an example,the time history analysis method was used to analyze the formation process of the plastic hinges at the end of the members during the earthquake,focusing on the inspection of the partial failure of the structure in this period of time,and combining the above results,Pushover method and time history analysis method,the seimic response of the structure and the evolution of drift were calculated and analyzed.(5)According to the selection rule of earthquake records,10 earthquake records were picked,using the seismic peak acceleration(PGA)as the ground motion intensity index,and the story drift as the structural damage index.The incremental dynamic analysis of the multilayer concrete space frame was conducted to analyze the performance of the structure at different service times and different seismic intensities,based on which,the probability demand model of the structure at each service time was fitted to obtain the structure fragility curves and fragility matrices,so that the seismic performance of structures was evaluated from a probabilistic perspective.