Research On Some Problems In Design And Construction Of Space Structure

Large span space structure is being thriving in recent ten years: increasing number of engineering projects, diversification of space structure styles. Space structure is a type of structure composed of a series of members arranged in a certain order and connected by joints.,which gradually perfecting of relevant theoretical investigation and design technology ,and also having some problems .This paper carries out corresponding analyzing and studying on the designing and construction of space structure.Space structure has an extreme large number of members, and the former designing process is to design the member section by calculating out its stress, which is only a member-oriented section designing method. Factually, failure of several members, stress of which may not be that high among so many members, may cause serious decline in bearing capacity of other parts of or the entire frame. These members should be paid special attention during designing, and should be strengthened if the designer wants to. Consequently, it is necessary to make a classification of the members according to the possibility of failure and effect to the entire structure after failure., which is really a structure-oriented designing method. The paper proposes the concept of robustness coefficient ( )ψxi and its mathematical expression. And this paper adopts numerical examples to make clear illustration on this point.In finite element method, beam element and link element are basic elements when analyzing truss. But, the link has the initial defect more or less because of the manufacture and transport. In order to know the degree of the initial defect to the stiffness and internal force ,this paper deduces the stiffness matrix of link element with initial bending, and illustrates the effect of initial defect by comparing members'stiffness with different initial defects. In addition, this paper analyzes various existent flexural members, deduces the limit max initial bending of flexural member, and discusses the reasonability of taking a 1/1000 initial bending as the initial geometrical defect of compression members in the current code.As to prestresing space structure, controlling of prestressing level could be gained through initial length defect. Based on this theory, this paper analyzes both methods of reversely deriving initial length defect from the giving boundary conditions, effect matrix method and direct iteration method, and demonstrates that the latter one could meet the engineering accuracy requirement, quickly calculating, avoiding from solving linear system of equations and easily mastered by designers. Furthermore, the paper compares the test data and theoretical data, and proves the security of prestressing application of the roof of Wuhan Experimental Hall of Yangzi Anti-Flood Model. Therefore, it is necessary to take a whole course trace of the prestresing application during constructing space structures, and thus if any emergency occurs, it could be solved on the spot. Scaffold, a temporary support system during construction, which directly affects the entire structure's bearing performance, has various kinds of initial defect, second-order effect, base settlement and many other factors that might cause a decrease of axial stiffness while the load increases. And this paper simulates the initial defect of scaffold by uniform defect mode method, includes its geometrical nonlinear by large displacement analysis function in Ansys, takes analysis to the entire structure by"simulative link", and thus accurately simulate its real load condition.