Finite Element Analysis And Optimization Of The Net Shell Roof On The Large Vertical Storage Tank

With the development of large oil storage tanks,Original rib-patterned fixed roofs on the oil tanks have shown big limitation.Reference to net shell roof on the large venuein the field of building structures has the advantages of big span and excellent force performance.More and more different types of steel and aluminum net shell have been applied to oil tank'sroof.But for net shell roof of selection,design and calculation on the large diameter storage tank,domestic petrochemical industry has not developed a detailed design standards.The existing research is also not systematic and in-depth,causing the roof selection and design is still the focal point and difficult point in large storage tank's design.Based on the related research results,through the comparative analysis of seven kinds of common single-layer spherical reticulated shell structure,Lamella-Kiewitt mixed type shell and geodesic reticulated shell,two kinds of net shell roof suitable for large vertical storage tank,are screened out as the research objects of this paper.The finite element software ANSYS was used to simulate the strength,stiffness and stability of steel form and aluminum form of two kinds of net shells in two kinds of control conditions.Besides,the calculation results are analyzed and compared.Finally,from both safety and lightweight angle,the geometric parameters of steel Lamella-Kiewitt mixed type shell are optimized.The main work of this paper is as follows:(1)Based on the design of the net shell roof on a 50000m~3 large vertical storage tank,the analysis of the two dimensions and the calculation conditions of net shell structure is determined.The entity modeling and finite element analysis of the steel form and aluminum form of two kinds of net shells are carried out.The results show that in the two control conditions,the strength,stiffness and stability of the two kinds of net shell structures,whether in the form of steel or aluminum,are in accordance with the design requirements.(2)The selection of materials(Steel and aluminum)and shell type(Lamella-Kiewitt single layer latticed shell and geodesic domes)influence on the mechanical properties and the stability of roof structure have been discussed.The results show that geodesic domes are superior in strength and stability in both steel or aluminum.No matter what type structure of shell,aluminum reticulated shell is stronger than steel reticulated shell,but steel reticulated shell has more advantages in stability compared to aluminum.(3)For the steel Lamella-Kiewitt single layer latticed shell,the design of cross section geometric parameters of the shell link is optimized by ANSYS software Design Opt module.Not only the relationship between the four parameters(H,B,T1 and T2)and the stress of the shell structure is indicated,both the economy and mechanical properties of the optimized structure are improved for the adjustment of four design variables.The simulation results also verified that the optimized structure is more reasonable than before.