Theoretical Research On Large-Span Tensile Spatial Structures Composed Of Cables, Bars And Beams

It is to found that C.Oran Beam-Column element converges very difficultly in nonlinear stability analysis of pure bending problem. The classical T.L. or U.L. FEM has low efficiency in the stability analysis of a spatial structure with high axial force in each element. However, when the moment of element increases, the computational efficiency decreases dramatically by using C. Oran Beam-column element.A numerical algorithm is presented in this paper to take account of the slippage of cable segments in continuous cable tension analysis. A simple example proves that this algorithm is right. The equilibrium matrix theory is first extended to cable-beam assembly and proved to be right by a Beam-String structure which has one Self-stress mode. In cable-Beam assembly, beam elements can not be actively tensioned. The distribution of initial internal force of all elements of a spatial structure composed of cable, bar and beam elements can be obtained by equilibrium matrix. It is useful to select the section of every element referring to such self-internal-force distribution, and it is helpful for the design of this kind of structure.In this paper, the dynamic relaxation method and the local arc-length method are integrated to search for the post-buckling path of reticulated spatial structures. This new method is proved to be right by classical examples in stability analysis of spatial reticulated structures. In this paper, a new method which is called local analysis method is presented to solve the distribution of initial internal force of elements of the large-span reticulated tension spatial structure composed of cable, bar and beam elements. Moreover, another method is also presented to solve the same problem which is called as linear combination method of internal force vector caused by unit initial strain of actively-tensioned cable. The problem of the determination of the final geometry of the single-layer reticulated shell with zero element internal force is also successfully solved by using this method. Based on the research on the shape determination theory a conclusion has been obtained: the distribution of the initial self-internal-force vector determines the initial shape of an assembly which has form finding problem. At the same time, the magnitude of the self-internal-force vector affected its zero self-internal-force geometry. Another point is that the selection of element section can also affects its zero self-internal-force geometry. The zero self-internal-force geometry and the initial self-internal-force geometry mentioned here mean the geometry which take no account of the self-weight of element.The determination of the property of element section when the self-internal-force of the element has been assigned is presented in this paper, up to now, to the author's knowledge, this problem has not been discussed by any scholar home and abroad. Its meaning consists in the feasibility of the construction of cable-bar assembly and cable-beam assembly. Namely, whether an assembly with initial self-internal-force which gotten from the equilibrium matrix theory can be constructed ideally or not, whether the design geometry presupposed can be accessed at last or not, whether the internal force of negatively tensioned element for example beam elements can release absolutely when actively tensioned elements are all set free. This problem has close relation with the construction of hybrid structure with first-order infinitesimal mechanism or higher-order ones. The solution of this problem supplements the equilibrium matrix theory. So it is very meaningful in theory and valuable in engineering application. Based on the static analysis of large-span tension spatial structure composed of cable, bar andbeam element, the proper distribution and magnitude of initial self-internal-force of element wasanalyzed in this paper.The dynamic analysis of large-span tension spatial structure composed of cable, bar and beamelement was also obtained in this paper. So a clear concept of the dynamic response of t...