The Initial Imperfections Of Single-layer Reticulated Shells And The Nonlinear Stability Analysis Of Kiewitt-sunflower Single-layer Reticulated Shells

Single-layer reticulated shells are very sensitive to initial imperfections, slight node deviation may have a great effect on structural stability. The stability of single-layer reticulated shells has been studied a lot by many researchers, fruitful results have been obtained. But it’s short of systematical theoretical study about the key factor of initial imperfections. In recent years, Kiewitt-Sunflower single-layer reticulated shells are applied in practical engineering widely. However, the theoretical research about the new hybrid is relatively less. Therefore it is very valuable in both theoretical and practical meaning to carry out systematical researches in the initial imperfections of single-layer reticulated shells and Kiewitt-Sunflower hybrid reticulated shells.Based on ANSYS and self-compiled pre/post-processing programs, the calculated models, discretization analytical method and nonlinear solution principles are introduced in this paper. Reasonable suggestive values of related coefficients in the calculations are offered. Two instability forms of reticulated shells are summarized. The theoretical foundations are laid for the following large-scale parametrical analysis.More than 12000 double nonlinear stability analysis of common three-way grid, Kiewitt, Sunflower and Kiewitt-Sunflower reticulated shells are carried out. N order eigenvalue imperfection mode method is proposed, comparing the results with the random imperfection mode method and the consistent imperfection mode method. The suggested value of N is offered based on the probability reliability.The investigation of the initial geometrical imperfection calculation maximum value in the stability analysis of single-layer latticed shells is carried out systematically, focusing on the transformation of structural stress state in different imperfection calculation maximum values. The rationality of imperfection calculation maximum value is judged by practical construction acceptance requirements, imperfection influence coefficient and stress state. The initial geometrical imperfection calculation maximum value in the stability analysis of single-layer latticed shells is given.Double nonlinear stability analysis about Kiewitt-Sunflower single-layer reticulated shells is conducted largely, coming up with the four main instability modes. The profit growth rate is defined to reflect the structural economic performance, evaluating the rationality of the structure from safety and economy two sides. In addition, the effects of various parameters, namely rise-to-span ratio, sections of elements, frequency ratio, initial imperfections and unsymmetrical distribution of loads are summarized. The stability ultimate bearing capacity is fitted finally, and the common formula about the stability ultimate bearing capacity of Kiewitt-Sunflower single-layer reticulated shells is proposed.