Shape Optimization and Stability Analysis for Kiewitt Spherical Reticulated Shell of Triangular Pyramid System

Abstract

The Kiewitt spherical reticulated shell of triangular pyramid system is taken as the object of this study; a macroprogram of parametric modeling is developed by using the ANSYS Parametric Design Language. The minimum structural total weight is taken as the objective function, and a shape optimization program is proposed and compiled by adopting the sequence two-stage algorithm in FORTRAN environment. Then, the eigenvalue buckling analysis for Kiewitt spherical reticulated shell of triangular pyramid system is carried out with the span of 90 m and rise-span ratio of 1/7~1/3. On this basis, the whole nonlinear buckling process of the structure is researched by considering initial geometrical imperfection. The load-displacement curves are drawn, and the nonlinear behaviors of special nodes are analyzed. The structural nonlinear behaviors affected by rise-span ratio are discussed. Finally, the stability of reticulated shell before and after optimization is compared. The research results show that (1) users can easily get the required models only by inputting five parameters, i.e., the shell span (S), rise (F), latitudinal portions (Kn), radial loops (Nx), and thickness (T). (2) Under the conditions of different span and rise-span ratio, the optimal grid number and bar section for the Kiewitt spherical reticulated shell of triangular pyramid system existed after optimization; i.e., the structural total weight is the lightest. (3) The whole rigidity and stability of the Kiewitt spherical reticulated shell of triangular pyramid system are very nice, and the reticulated shell after optimization can still meet the stability requirement. (4) When conducting the reticulated shell design, the structural stability and carrying capacity can be improved by increasing the rise-span ratio or the rise. (5) From the perspective of stability, the rise-span ratio of the Kiewitt spherical reticulated shell of triangular pyramid system should not choose 1/7.