Experiences in the Design Analysis and Construction 247 The double membrane layer helps towards the thermal protection of the inner space.A disadvantage,however,is the excessive amount of textile mate- rial,as the surface of the lateral walls of the tubes amounts for the 30%of the total surface of the membrane structure.This disadvantage can be overcome using the tension-rope system described next. Low pressure membrane structures within tension ropes These double membrane inflatable structures are formed by two membrane layers connected by tension ropes.The ropes are placed at strategic points in order to preserve the desired shape of the structure.The amount of membrane material in these structures is considerable less than in the tubular structures with the corre-sponding savings in the weight and the overall cost of the structure.An example of a structure of this type recently built by the company BuildAir (www.buildair.com)is shown in Fig.5. Fig.5.Cylindrical pavilion formed by a double layer membrane with tension ropes 3 Structural Analysis and Pattern Design Traditional methods for analysis of inflatable structure are based on mem- brane and tube theories 9,10.A more detailed analysis of inflatable struc- tures can be performed using membrane finite elements allowing for large displacement analy-sis combined with one-dimensional elements to model theExperiences in the Design Analysis and Construction 247 The double membrane layer helps towards the thermal protection of the inner space. A disadvantage, however, is the excessive amount of textile mate￾rial, as the surface of the lateral walls of the tubes amounts for the 30% of the total surface of the membrane structure. This disadvantage can be overcome using the tension-rope system described next. Low pressure membrane structures within tension ropes These double membrane inflatable structures are formed by two membrane layers connected by tension ropes. The ropes are placed at strategic points in order to preserve the desired shape of the structure. The amount of membrane material in these structures is considerable less than in the tubular structures with the corre-sponding savings in the weight and the overall cost of the structure. An example of a structure of this type recently built by the company BuildAir (www.buildair.com) is shown in Fig. 5. Fig. 5. Cylindrical pavilion formed by a double layer membrane with tension ropes 3 Structural Analysis and Pattern Design Traditional methods for analysis of inflatable structure are based on mem￾brane and tube theories [9,10]. A more detailed analysis of inflatable struc￾tures can be performed using membrane finite elements allowing for large displacement analy-sis combined with one-dimensional elements to model the