Degradation Process And Seismic Response Analysis Of Concrete Structure Seismic Performance In Marine Environment

In the marine environment,reinforced concrete structures often undergo complex physical and chemical reactions with sulphates,chlorine salts,and other substances in seawater,resulting in damage to the mechanical properties of concrete and steel bars,resulting in a reduction in the bearing capacity and durability of the structures and the life of buildings.Therefore,it is of great significance to evaluate the durability and reliability of the concrete structure by studying the response of the damaged reinforced concrete structure under earthquake.In this paper,the constitutive model of concrete and steel bars under corrosion conditions is studied.Through the re-development of finite element software OpenSEES,the corrosion constitutive relations are reprogramed into OpenSEES software,and seismic response under the corrosion conditions are obtained through Pushover analysis and dynamic time history analysis,and analyzes the change law of the seismic performance of reinforced concrete structure with corrosion time.The details are as follows:(1)Firstly,according to the basic principle of Pushover analysis method,the calculation process of capacity spectrum method and the method of target displacement are given in detail.The corresponding MATLAB calculation program is written and the GUI visualization operation interface is developed.(2)Secondly,according to the diffusion law of sulfate in concrete,the distribution of sulfate ion concentration and the damage coefficient of concrete strength in the concrete cross section are obtained through numerical analysis.Based on the Kent-Park constitutive model,a concrete constitutive model considering the erosion damage of sulfate ions was established.According to the rule of corrosion of steel by chloride ions,the constitutive relation of reinforcement and the formula for the remaining section area of steel bar under the joint action of uniform corrosion and point corrosion are deduced.(3)Then,through the re-development of the constitutive relations of concrete in OpenSEES,the concrete constitutive model with the change of corrosion time is obtained.At the same time,by modifying the cross-sectional area of rebar at different corrosion ages,the reinforced concrete portal frame under corrosion conditions is established.The analysis model and the one-way Pushover analysis and the cyclic reciprocating pushover analysis of the model show that the mechanical properties of the concrete portal frame under the corrosion condition decrease with the increase of corrosion time.(4)Finally,based on the constitutive relationship of reinforced concrete considering corrosion,using OpenSEES as a finite element modeling platform,Pushover analysis and time history analysis of the high-rise reinforced concrete frame structure in the marine environment were conducted.The Variation of maximum story drift,displacements of structurally weak layers and Structural Performance Point with corrosion time under rare earthquakes were studied.The results show that the seismic performance of high-rise frame structures decreases with the increase of corrosion time.