Research On Static Properties And Stability Of 800 Meters Super-large Span Kiewitt Type Mega-latticed Structure

With the development of the society and construction level, more attention has been drawn to super-large span structures for it has more and more promising applications in city protection against extreme climates, residential area establishment and energy conservation and emission reduction. With increases in span, the number of members and their size will be increased, thus bringing more challenges to the analysis of static behavior and stability performance, as well as for member section optimization.In this paper, reasonable 800 meters super-large span structure was mainly studied. A comparison was made of four super-large span structures and Kiewitt type mega-latticed structure was chosen as the best one. The command-flow was firstly developed which can create Kiewitt type mega-latticed structure automatically and static analysis, stability analysis and parameter analysis were completed in the same time. The studies in this paper is the basis of further research and guidance for actual engineering design. The major research contents are listed as follows:1. A comparison was made of internal force peak, maximum displacement and steel consumption of the double-layer reticulated shell, the local triple-layered reticulated shell, ribbed type mega-latticed structure and Kiewitt type mega-latticed structure with the same loads. Selected the most reasonable structure form——Kiewitt type mega-latticed structure. And the reasons were analyzed from structure characteristics and mechanical principle.2. A complex structural configuration of this structure was analyzed in detail through CAD 3D modeling and a command-flow was developed to create the new structure automatically using APDL as an innovative structural-programming method based on the structural form parameters. This lays a good foundation for further study of Kiewitt type mega-latticed structure.3. A command-flow for impose of load and a command-flow for optimization of member sections were developed and the mechanical performance of the structure was studied. The load that acts as a controlling role was studied and the rules for the internal forces distribution have been summarized.4. The ultimate bearing capacity was accurately obtained by considering the geometrical nonlinear of joint initial deviations, the material nonlinear and the geometrical nonlinear of members initial curvature. Then the double-judgment method to determine the overall buckling mode was put forward and reasonable values of the parameters were summarized in overall buckling mode. The nonlinear equilibrium paths were traced using the Arc-length method. The change rules of the ultimate bearing capacity were summarized. The reasons were analyzed by comparing with other structure forms and the characteristics of this super-large span structure form were considered in the same time.5. In order to research how the mechanical performance changes with the changes of structural form parameters. A great number of parametric evaluations including 153 models were studied for seven parameters, including circumferential/radial divisions, rise-span ratio and height-span ratio of truss. The mechanical property with the variation of the parameters was summarized and some suggestions were given based on the reasonable value range of every parameter. Then useful suggestions were given for further study and actual engineering design of this structure.