Study Of Stability Of The Prefabricated Ground-supported Corrugated Steel Silo Under Loading Of Grain

In marine atmosphere environment,chloride ions invade concrete under the action of salt spray for a long time,which lead to the corrosion of steel reinforcement in concrete structures and affect the durability and safety of the structure.Therefore,under the national natural science foundation “mechanism and numerical simulation for temperature-humidity and chloride ion coupling transport in concrete under marine atmosphere environment(project number: 51509084)”,the transport process of chloride ions in concrete was studied as the research object in the marine environment.The transport process of chloride ions in concrete was decomposed into two processes: the diffusion caused by chloride ion concentration and the transport process of chloride ions carried by water transport for capillary pressure.The salt spray test method was used to simulate the chloride ion transport process in concrete under atmospheric atmosphere.The effects of water-to-binder ratio,porosity,temperature and time on chloride ion content and diffusion coefficient of chloride ions in intrusive concrete were studied.The experimental results show that the diffusion coefficient and penetration depth of chloride ions increase with the increase of concrete water-binder ratio,porosity and temperature.With the increase of time,the diffusion coefficient of chloride ions is gradually reduced,and the intrusion depth of chloride ions is gradually deepened;the chloride ion content on concrete surface increases gradually with the rise of temperature.Based on the analysis results,the equation of relationship between diffusion equation of chloride ions and temperature,the equation for surface chloride ion content considered effect of temperature and time was established.The unsaturated transport experiments of chloride ions for 0.7,0.85,and 1 initial saturation concretes at 20 °C were implemented by the closed-state solid salt erosion method.The diffusion coefficient equation of chloride ions in the unsaturated state considering the influence of saturation was obtained.Based on the chloride ion diffusion equation considering the influence of temperature,time and saturation,the capillary pressure transporting chloride ion transport equation considering the influence of temperature was introduced,and the temperature-wet-chloride ion coupled transport mode was derived.A numerical simulation model was established by numerical simulation software for the theoretical transport model of chloride ions.The transport model was verified by chloride ion diffusion test under salt spray and transport test for unsaturated chloride ion.The results show that the simulation results of the theoretical model are in good agreement with the experimental results.Further through numerical analysis,it is found that with the increase of temperature,the content of chloride ions on the surface increases and the diffusion rate of chloride ions increases with the rise of temperature.The numerical simulation of chloride ions transport under the action of temperature and humidity coupling was carried out.For absorption process,the transport speed of chloride ions increases with the increase of temperature and saturation gradient,and the transport speed of chloride ions under coupling action is larger than that of pure diffusion.Under the larger the saturation gradient,the influence of capillary action on the transport speed of chloride ions is greater.When the saturation gradient is the same,firstly the effect of capillary action on chloride ion transmission increases,and then decreases with increasing depth from the concrete surface.For desorption process,the chloride ion transport speed under coupling action is smaller than under pure diffusion.The larger the saturation in concrete,the influence of capillary action on chloride ion transport speed is greater.Under the dry and wet cycle environment,with the increase of time,invasion depth of chloride ions is deeper.The saturation is stable in deeper concrete,the depth of influence is only 6mm.The longer the wetting time,the faster the chloride ion erosion.The length of dry and wet cycle has little effect on saturation and chloride ion transport.