Wind tunnel tests of an inflated membrane structure. Two study cases: with and without end-walls

Abstract

The use of textile membranes in architecture and civil engineering has increased rapidly in the last decades. Membrane structures are lightweight, economic structures with unique shapes. At the same time, their structural analysis is particular compared to the analysis of conventional structures. The form-finding procedure, the large displacements of the structures, and the special properties of the composite material all require unique tools. The wind analysis of membrane structures is one of the most challenging parts of the design because the design codes do not provide the pressure coefficients of the doubly curved shapes of membrane structures. The main scope of the present research was to determine the mean pressure coefficient fields over an inflated membrane structure by wind tunnel experiments. The structure, composed of six inflated circular arches, was analyzed with and without end-walls for three wind directions. The equilibrium shape of the inflated structure was determined with the Dynamic Relaxation Method. During the numerical form-finding procedure, the orthotropic behavior of the membrane material and the warp and fill directions of the textile fibers were also considered. Based on the numerically determined equilibrium shape of the inflated structure, a model was made using a 3D printer. The flow around the model according to three wind directions was analyzed in an open-circuit wind tunnel. The pressures were measured in 102 external and 102 internal points of the inflated arches and 27 points on each end-wall. In this paper, the experimentally determined pressure coefficient fields for different wind directions are presented and compared for the open (without end-walls) and closed (with endwalls) cases. The thoroughly introduced experimental results can be used during the structural analysis of future inflated structures with similar shapes.