裁断図をもとにした膜構造物の実初期つり合い状態の解析

Abstract

Current analytical methods for determining an initial equilibrium configuration of membrane structures are based on the assumption that the membrane stress distribution is uniform all over the surface. On the other hand, a typical fabrication process of these structures is that a complex curved surface is divided into some plane membrans strips called "cutting patterns", they are assembled each other and finally they are stretched between the fixed boundary structures. Therefore, the actual stress distribution deviates from the assumed uniform stress state and overstessed or nonstressed (wrinkling) regions possibly occur in the actual membrane structures. In this paper, this actual initial equilibrium state is clearly defined in consideration of actual fabrication process and a new analytical method for determinining this equilibrium state is proposed. In the analysis, the geometry and material properties of the cutting patterns are given and the stress distribution and equilibrium confuguration are treated as unknown variables. By adopting the proposed method to simple membrane structural models, the deviation of actual stress state from the assumed uniform stress state was found to be significant and the necessity of the proposed method for evaluating the response and safety of actual structures was confirmed. Furthermore, the applicability and the validity of the proposed method were verified through the simulation analysis of an actual erection process of an actual tensile membrane structure designed by the authers.