A Study On Seismic Performance And Optimal Design Of A Large-scale Steel Silo

As a solution for the long-term storage of various types of energy products and raw materials,steel silo plays a vital role in buffering and regulating the processing and transportation of production material.As a result of the increasing demand for storage from various industries,there is a trend toward large-scale steel silo design.The top of the steel silo mostly adopts a reticulated shell or truss structure,which is calculated separately during the design process.This research studies an 80,000-ton large scale floor type steel silo from an actual project.Considering the combined impact of the cylinder component,internal storage and the top structure on the mechanical properties of the steel silo,an overall finite element model of a steel silo-reticulated shell structure is developed.Static,stability and seismic action analyses,as well as structural design optimization,are carried out on the model.The main research contents and outcomes are as follows:(1)When developing the overall finite element model of the steel silo-reticulated shell structure,the load on the reticulated shell is first derived through calculation performed with MST,a space structure design software,and then applied to it.The stress and displacement distribution patterns of the model under single and combined load conditions are analyzed.The results indicate that the storage load has led to the most significant stress and radial displacement on the silo.Besides,under the most unfavourable load combination,the stress concentration is observed in both the ring rib and vertical rib in the bottom area.(2)The stability analysis is conducted on the steel silo under vertical and wind loads,respectively.The results indicate that under the vertical load,the reticulated shell has more sensitive nonlinearity,compared to the cylinder component of the steel silo.In addition,the existence of storage can enhance the stability of the cylinder component in the steel silo.(3)The finite element model of a fully stocked steel silo is established considering the interaction between the internal storage and the silo wall.The time history analysis of empty silo and full silo is carried out,respectively,under three selected seismic waves applicable to type Ⅱ sites.Then,a parametrical analysis for the Poisson’s ratio,friction coefficient and cohesive force of the storage is conducted.Analysis shows that,under the action of frequently occurred earthquakes,the displacement and stress response of the full silo is significantly larger than those of the empty silo,and an evident drum deformation can be observed at the bottom of the cylinder.Moreover,under the action of rarely occurred earthquakes,simultaneously with the drum deformation at the bottom of the cylinder,the top storage is gradually compressed to one side,the storage on the opposite side is no longer in contact with the wall,and the deformation due to inward depression appears in the middle of the warehouse wall.According to the calculation method of floor type steel silo from Chinese Standard,the vibration mode decomposition response spectrum analysis is carried out for the full silo under frequently occurred earthquakes,and then the bottom shear force and bottom bending moment of the structure are acquired and compared with the results of time history analysis.The results indicate that time history analysis generates smaller values for both bottom shear and bottom bending moment,indicating that the calculation based on the Standard is conservative.(4)Representative combinations of parameters are selected according to the orthogonality for further finite element optimal analysis under multiple load cases.By adjusting several parameters including the wall thickness,the cross-section of the steel column,as well as the cross-section and spacing of stiffeners,the influence of different parameters on the mechanical performance of the structure is investigated.The result shows that the strength of the stiffener has a relatively significant impact on the mechanical properties of the steel silo.In addition,the comparative evaluation indicates that the optimized structure has a more uniformly distributed stress,which takes better advantage of the property of steel,validating the proposed method.