308 Arno C.D.Pronk and Rogier Houtman pneumatic structures.As a first study a model has been build that consists of bal- loons and a wire-frame that is placed in a nylon stocking (Fig.2).It is possible to make many different forms with this technique.After modeling the shape a polymer resin is applied(Fig.3).This physical model can be analyzed by means of a finite element computer program that looks at the active behavior of the surface of the structure.The input for the program is generated by a 3d scan(Fig.17). 4 Stage Covering for an Open-Air Theatre 4.1 Introduction This semi-permanent membrane structure covers the stage of the open-air theatre in Soest (the Netherlands)Fiber reinforced plastics are used for the production of a structural optimized and therefore lightweight and complex arch shaped struc- ture.By using an inflatable mould the arch could be produced more economically (30%cost reduction).In the production the vacuum injection method is utilized for stiffening flexible fibers. The owner of the Soest open-air theatre asked for a protection against bad weather for the stage.Therefore we suggested covering it with a lightweight mem- brane structure.A suspended membrane floats above the stage,so that visual rela- tions with the natural environment are still preserved(Fig.7).Outside the theatre- season the structure could partially be dismantled in this way the environment that is protected by national government is not visually disrupted.Two guyed columns are part of a dismantling system and could be used for hoisting the temporary membrane.The form of the spatial membrane is,beside the indirect support of the columns,the result of an arch.Because of this arch the protective area of the cov- ering is increased and additional curvature in the membrane is improved (Fig.8). In this way the membrane structure is a combination of two highpoint surfaces and an arched surface,the stage covering works like a tensegrity structure.The columns and arch transmit compressive loads.Both the Tensile loads and the stabilization of the whole structure are transmitted and organized by the prestressed membrane and cable structure. Fig.7.The stage covering for the Fig.8.An arched beam ensures an Soest open-air theatre in the Nether- increase of the protective area and the lands(H.Werkman) curvature of the membrane structure308 Arno C.D. Pronk and Rogier Houtman pneumatic structures. As a first study a model has been build that consists of bal￾loons and a wire-frame that is placed in a nylon stocking (Fig. 2). It is possible to make many different forms with this technique. After modeling the shape a polymer resin is applied (Fig. 3). This physical model can be analyzed by means of a finite element computer program that looks at the active behavior of the surface of the structure. The input for the program is generated by a 3d scan (Fig. 17). 4 Stage Covering for an Open-Air Theatre 4.1 Introduction This semi-permanent membrane structure covers the stage of the open-air theatre in Soest (the Netherlands) Fiber reinforced plastics are used for the production of a structural optimized and therefore lightweight and complex arch shaped struc￾ture. By using an inflatable mould the arch could be produced more economically (30% cost reduction). In the production the vacuum injection method is utilized for stiffening flexible fibers. The owner of the Soest open-air theatre asked for a protection against bad weather for the stage. Therefore we suggested covering it with a lightweight mem￾brane structure. A suspended membrane floats above the stage, so that visual rela￾tions with the natural environment are still preserved (Fig. 7). Outside the theatre￾season the structure could partially be dismantled in this way the environment that is protected by national government is not visually disrupted. Two guyed columns are part of a dismantling system and could be used for hoisting the temporary membrane. The form of the spatial membrane is, beside the indirect support of the columns, the result of an arch. Because of this arch the protective area of the cov￾ering is increased and additional curvature in the membrane is improved (Fig. 8). In this way the membrane structure is a combination of two highpoint surfaces and an arched surface, the stage covering works like a tensegrity structure. The columns and arch transmit compressive loads. Both the Tensile loads and the stabilization of the whole structure are transmitted and organized by the prestressed membrane and cable structure. Fig. 7. The stage covering for the Soest open-air theatre in the Nether￾lands (H. Werkman) Fig. 8. An arched beam ensures an increase of the protective area and the curvature of the membrane structure