Effect of Imperfections on Lattice Shells

Abstract

A nonlinear elastic‐plastic method for analyzing three dimensional beam elements is presented. The method uses the average effect of moment‐axial‐force curvature equations in each bending direction to compute the terms in the element stiffness matrix. The method is applied to the imperfection‐sensitivity investigation of lattice domes made up of tubular members; a space frame representation of lattice domes is employed. First, a class of domes is designed using current specifications in conjunction with a linear frame analysis. Nonlinear elastic‐plastic analyses of the designed dome are carried out to determine the relationship between the design load and the actual failure load. Koiter's approach to imperfection sensitivity is carried out in a discrete finite element form with linear mode shapes used as geometric imperfections. It is found that imperfection sensitivity is a function of the dome's rise‐to‐span ratio. Domes with a high ratio may be dominated by inelastic behavior rather than imperfection sensitivity.