Theoretical Study On Thermal Effects Of Steel Silo And Structural Behaviors With Temperature Difference

As an efficient storage structure,the steel silos have been widely adopted in industry and agriculture.With the urgent demand for storage capacity,the steel silos is becoming more and more large,which makes the conventional design method of the shell structure questionable.As the steel silos usually located at the open field,the thermal loads induced from solar radiation,suddenly drop in ambient air temperature,and long-term temperature change directly affect the shell structure significantly.Additionally,the characters of the stored granular material are also complicated,for instance,some granular material’s temperature is high when filled into the silo and some grain’s temperature will increase by self-heating.All these thermal factors influence the behavior of silo greatly and lead to the failure of steel silos around the world over past few decades.Thus,it is of great significance to study on thermal actions and structure response of the silo.The theoretical analyses and numerical calculations are adopted in this dissertation to investigate the thermal effects and the structure response of the ground-supported flat bottomed cylindrical steel silos.The reseach aims to provide theoretical basis and advices for reasonable thermal-resistant design of steel silos.The layout is organized as follows:(1)Based on the bending theory of cylindrical shell,the analytical solutions to measure the thermal displacement and the stress resultants of silos are deducted under different boundary conditions.It is feasible for designer to measure the thermal effects in practice.And the analytical solutions to measure the thermal effects of vertical temperature difference caused by high temperature granular material are also proposed.(2)Based on the theory of transient heat transfer and ASHRAE clear sky model,the temperature field of steel silos under solar radiation are programed with the ANSYS APDL language.The temperature filed of steel silo with uniform and stepped wall thickness are analyzed to summarized the temperature distribution of the silo wall under solar radiation.Then the finite element model which accounts the heat transfer between silo wall and storage material are developed for analyzing the storage material effects on the temperature filed.Finally,the simplified method for calculating the temperature field of the steel silo under solar radiation are proposed based on the heat transfer theory,ASHRAE clear sky model,and results of the numerical analyses.(3)The stiffness of the stored granular materials effect on the thermal lateral pressure are conducted theoretically when the silo subjected to uniform drop in temperature,and the formulations to measure silo wall’s displacement and stress resultants are also derived based on shell bending theory.(4)The finite element model accounting for the interaction between silo walls and stored granular materials is established for evaluating temperature influences on silo lateral pressures.To consider the deformation interaction between silo wall and granular materials under temperature variations,the flexible-flexible contact model and the surface-surface contact method was used for simulating.Three thermal loads and five type steel silos are chosen to explore thermally induced pressures on shallow and deep silos respectively,and the results are compared to classical and experimental pressures.Finally,an improved method for calculating thermally induced pressures in steel silos is proposed.(5)The solar radiation and thermal pressure effect on the large flat bottom steel silos in practice are conducted.The results of the analyses show that the solar radiation temperature field will lead a non-uniform stress distribution of the wall,and thermal lateral pressure have a significant influence on the structural behavior by contrast to those ignore the stiffness of stored granular materials.(6)The buckling behavior of the steel silos subjected to the vertical temperature difference produced by high temperature stored granular materials is investigated.The effects of temperature variations,geometric non-linearity,material non-linearity and,the forms and amplitude of the imperfections are considered.Finally,the buckling failure mechanism of silo is examined.The research provides some references for designers and researchers,and can be adopted in the practical design of steel silo.