Seismic Analysis Of Large Flat-bottom Squat Steel Silos

With the rapid development of Chinese economy, large steel silos have been widely used in numerous industries, such as food processing, brewing, building materials, environmental protection, chemical industry and so on. The advantages of steel silos include, but are not limited to, small weight, high strength, convenient construction, large storage capacity and good air tightness. However, due to the steel silos’ complexity in structure behavior and failure criteria, it is so shallow in the early stage of study on the mechanical performance especially the seismic performance in our nation. In the previous earthquakes, most of the steel silos were subjected to varying degrees of damage, threatening the lives and property safety of people.This paper is based on a project of a flat-bottom squat cement steel silo. Using the finite element analysis software ABAQUS, the 3D silo model is established, in which the friction between the bulk and silo wall is simulated by setting contact. Combined with the relevant steel silo design code, the static analysis, the modal analysis and the time history analysis are made on the model to research the seismic performance of the steel silo.In the static analysis of the steel silo, it is indicated that the most unfavorable position of the silo wall is 0-3m height from the bottom under the static loading, and the change of wall thickness results in the stress mutation. The finite element results are slightly lower than the normative calculation results. Besides, the influence of bulk subsidence and the bending force of thin-walled shell are taken into account in the finite element analysis but not in the code. The structure’s dynamic characteristics of two steel silo models(fulfilled and unfilled silos) are investigated in the modal analysis to lay the foundation for the seismic analysis. The stress and displacement of silo wall for two models(fulfilled and unfilled silos) are mainly discussed in the time history analysis under seismic action(6 degree and 8 degree seismic precautionary intensity). The El-centro earthquake wave is chiefly considered in the time history analysis. The results from the analysis are compared with which according to the standard. And then the Taft wave and Tangshan wave are applied to the structure to briefly verify the finite element results. In the time history analysis, it is demonstrated that the most unfavorable position of the silo wall is 0-6m from the bottom, while the maximum displacement is located in the vicinity of the top 0-3m under seismic force, and the change of wall thickness also results in the stress and displacement mutation. The normative calculation results are obviously higher than those of the finite element calculation, illustrating that the friction between the bulk and silo wall as well as the bulk’s stiffness is the factor that can not be neglected during the process of earthquake. In addition, the factors that the settlement of storage material, bending force of thin-walled shell and the silo wall’s hoop stress resulted from the seismic effect are involved in the finite element analysis while not in the specification.Combined with the relevant content in the steel silo design standard, the static, modal and time history analysis of the large flat-bottom squat steel silo in this paper are aimed to provide reference and basis for the design particularly the earthquake-resistant design of flat-bottom squat steel silo.