ELASTO-PLASTIC STABILITY ANALYSIS OF LATTICED SHEELS WITH INITIALLY CURVED MEMBERS BY WEAK-FORM QUADRATURE ELEMENTS

Initial imperfection is one of the major influential factors for the stability of a latticed shell. The consistent imperfection mode method recommended by current technical specifications consider both nodal deviation and initial curvature of members, but the sole influence of initial curvature cannot be easily identified. In this study, a weak form quadrature beam element model was formulated based on the geometrically exact beam theory. Incorporating the fiber model for material nonlinearity and the arc length algorithm, elasto-plastic large displacement analysis of spatial curved beam structures was conducted. Examples were examined to verify the effectiveness of the proposed model. By the use of the proposed model, displacement shape functions are not necessarily designated and delicate modeling of curved beams in other finite element software can be avoided. In the analysis, ultimate loads of several typical latticed shells consisting of members with random initial curvature were obtained. It is found that the member defect of initial curvature had little effect on the load-carrying capacity of a latticed shell and therefore was not the main factor for stability under the circumstances of current steel-production quality control technique. Results were compared with those from the consistent imperfection mode approach and the technical specification for space frame structures. It is suggested that the yield strength of material and the specific form of a latticed shell should be considered in the formula of the technical codes and standards.