**2. Form of the horn-shaped membrane roof**

The horn-shaped membrane roofs have several kind of planar shape, namely a circle, a square and a hexagon. This paper describes about the square based horn-shaped membrane roof. In general, the membrane structure needs to find appropriate forms to resist external force. 'European Design Guide for Tensile Surface' by TensiNet presents some methods of formfinding for the membrane structures (Forster & Mollaert, 2004). This paper used nonlinear finite element method to find the appropriate form on the square based horn-shaped membrane.

In this paper, the membrane material was defined as low stiffness material (see figure 3). On the other hand, a strut was defined as high stiffness material. A strut was transferred point B from point A in order to get the appropriate form using FEM analysis. A rise-span ratio h/L was defined as the ratio of a span L to a height of the horn-shaped roof H, and an appropriate form of h/L=0.2 was obtained by finite element method with geometrical nonlinear in this paper. Additionally, the top of strut was L/10 and there wasn't a hole on the middle of the horn-shaped roof. The final shape get three-dimensional curved surface.
