Tensioned Membrane Structure, Form-finding Analysis

The membrane structure has been a kind of new developed form of construction structure in nearest 20-30 years, which is adored by most of the people in the word for its special, elegant sculpt and the power of tensile force. However, as a new form of structure, the membrane structure is so far deferent from the traditional one in the conception and method of design. The membrane's roof is composed of flexile material of membrane with high strength. The roof and the system of crutch and tension structure combine to be a space structure with some rigidity, which can bear the corresponding loads.Because the membrane with high physical and geometric nonlinear property can not resist bending moment or sustain compressive stress, the design of it is completely deferent from traditional structure. The design of membrane structure includes form-finding, loading analysis and cutting analysis. Compared with the other steps, form-finding is the most important one. In addition, tension membrane structures is better than air supported membrane structures in design and utilization, so this paper make an analysis about the tension structure's form-finding.The paper compares three methods of form-finding, force density method, dynamic relaxation method and nonlinear finite element method, and adopts the last method for the form-finding of tension membrane structure. Considering that the temperature load can provide uniform stress, a method of utilizing temperature load and supporting points' movement is put forward. In order to control the stress in construction and the influence of tension error, a form-finding is utilized to simulate the construction.In general, the boundary is always looked as rigidity or is neglected, which may simple the calculation but can make some mistakes. The cutting and constructing of membrane structure correlated the step of form-finding directly, so the neglect of boundary's distortion will bring a drape phenomena. This means the prestressing of membrane structure does not reach its level anticipated. As a result, local areas of membrane appear compressive stress, which make these areas out of work and even affect the whole structure's situation of utilization. With one project of membrane structure this paper takes the affection of elastic crutch based on the analysis of rigid crutch, and provides the mutual analysis, a new solution to this problem.