Multiscale Simulation Of Rust Cracking Behavior Of Coastal Concrete Structure

Rebar corrosion is an important factor that causes damage to concrete components.Rebar corrosion not only affects the mechanical properties of the steel bar,but the rust products produced will also squeeze the concrete around the steel bar due to volume expansion,cracking the concrete protective layer and threatening the safety of the structure.Therefore,it is of great value to study the damage of concrete structures caused by corrosion of steel bars,and to evaluate the durability of concrete structures.The research content of this paper is mainly two aspects,namely the micro-mechanical characteristics of steel corrosion products and the failure law of concrete members under load.Based on this,the design carried out the corrosion test of reinforced steel and the damage experiment of reinforced concrete beams under the action of chloride salt corrosion-fatigue load coupling.Simultaneously,the simulation software was used to verify and realize the combination of experiment and simulation.The specific methods and conclusions are as follows:(1)The composition and arrangement of steel corrosion products are obtainedDesigned and conducted a steel bar corrosion experiment,using X-ray diffractometer,scanning electron microscope and other tools to analyze the sample.It is concluded that the steel corrosion products are composed of four crystal products: Fe3O4,Fe2O3,Fe OOH(iron oxyhydroxide),and Fe O.The arrangement is irregular,and it is unevenly distributed.(2)The failure rule of concrete components under the coupling action of chloride salt corrosion and fatigue load is provedThrough the chloride salt corrosion-fatigue load coupling effect of reinforced concrete beam rust cracking experiment and numerical simulation,it is concluded that the specimen is most severely damaged at the bottom surface and mid-span position.The bottom surface cracks are mainly distributed along the reinforcement,and the cross-sectional cracks are distributed around the reinforcement.The rust expansion load plays a major role in the failure process of the component,and the fatigue load will greatly accelerate and increase the failure of the component.(3)Established a numerical simulation method to obtain the elastic modulus of the corrosion productBased on the molecular dynamics method,using the LAMMPS software to conduct numerical simulation of nano-indentation of steel corrosion products.The elastic modulus of the corrosion product is calculated from the relationship curve between the load applied by the indenter and the depth of indentation.The results agree well with the existing conclusions.It can be used as a means to obtain the elastic modulus of composite materials.(4)The damage law of corroded reinforced concrete structure at meso level is obtained through finite element simulationThe two-dimensional finite element model of reinforced concrete subjected to rust expansion load is established,and it is concluded that the initial crack direction is perpendicular to the maximum load loading direction.And the cracks mainly appear at the mortar and interface layer,indicating that the interface layer is the weakest point of concrete.With continuous loading,a through seam is formed between the steel bars inside the component,and the crack near the end of the protective layer has extended to the surface of the component.This model better simulates the destruction process of rusted concrete components.