TESTING PHRAGMITES AUSTRALIS FOR DOUBLE CURVATURE DEPLOYABLE STRUCTURES

Abstract

Felix Escrig’s cover for the San Pablo Swimming Pool in Seville is one of the few examples of an actual application of a biaxial mesh of pantographs in Architecture. A structure that can contain space, easily transforming from a planar surface into a double curvature one, is rarely used as a solution to cover grand areas. In addition, most deployable structures use industrialized components with almost negligible dimensional variations. Analyzing Escrig’s structure with help from both physical and digital models, it is possible to understand its mechanical behavior and the changes in mesh morphology during the deployment process. These models showed how the biaxial mesh suffered some important angular deformations due to the rods and nodes adapting to the double-curvature shape during deployment, resulting in rod and node fatigue, which needed to be addressed before adapting the geometry to a heterogeneous material. This paper describes the geometric implications of using common reed (Phragmites australis) in the construction of double curvature deployable structures, examining the behavior of this heterogeneous material if employed on the manufacture of both rods and nodes. Using a scale model built from an adapted design, the geometry of the reed structure was tested. The heterogeneity of the reed required a redesign of the pivots of the blades and the nodes. This redesign showed that it is possible to use common reed for the construction of deployable double-curvature structures if certain mechanical design considerations, detailed as guidelines in this paper, are observed.