The Research On Static Behaviors And Structural Optimization Of Pretensioned Spherical Reticulated Mega-structure

The prestressed spherical reticulated mega-structure is a new type of space structure; in which pretress is put by laying out cables in the spherical reticulated mega-structure. It has many advantages, such as good mechanical properties, economizing steels, sutting to grow towards long-span and so on. But this structure is relatively lack of in-depth researches at home and abroad. So the tensioning construction of cables, optimization, and the static behaviors of the structure after optimization are deeply study in this paper. The main contents of the thesis are listed as follows:At first, based on the tension of cables always change after distortion taking place in struture, and the latter construction of cable can affect tension of cable which is stretched in the former. A new iterative calculation is put forward to solve the tension of cables in multistage tensioning construction. All cables can be tensioned to their designed tension values or its approximation at once, if each cables is tensioned to its construction control tensile force as calculated by this new method. And the example shows that the method is effective and feasibile.Then, to optimize the static behaviors of the prestressed spherical reticulated mega-structure, a three-grade optimization method is presented, in which the member cross section, height of 3D-trussed beam, and the cable prestress are all considered. Different objects and methods are applied in the process of optimization. The full-stress method is adopted to optimize the member cross section aiming for the minimum structural self-weight. The optimal height of 3D-trussed beam is determined accounting for both the peak value of internal forces and structural deflection. As to the optimization of prestress, the minimum sum of internal forces squared is taken as the objective function, and the influence matrix and complex methods are adopted to solve. For the structure with span of 180m, five arrangement styles of cables are presented, and optimization is carried out based on the above-mentioned method. The best style can be choosed by the analysis results.Finally, the internal force distributions of the majority member bars in the main struture and the bottom substructure are analyzed firstly; afterwards the transformations of some static behaviors (for instance, reaction at support, the maximum node displacement, average steel dosage, decreasing coefficient of displacement and etcetera)which are caused by the changes of parameters (such as rise to span ratio and span of main structure, height of substructure, the size of its big grid, the prestress and so on) are investigated through parameter analysis. At last, the change laws of those static behaviors with parameters varying can be obtained after analysis, and the best ranges of prestress definition which aim for the maximum decreasing coefficients of displacement under the different rise to span ratios of structure can be elicited. Then some advises about values of those parameters are also given in the paper.