Budapest University of Technology and EconomicsFaculty of Civil Engineering - Since 1782

Tensile membrane structures are lightweight, economic, environmental friendly structures with unique, exciting shape. Since they are constituted by a very thin membrane (with typically less than 1 mm thickness) that has a negligible bending stiffness, the shape of the tensile membrane has to be determined properly in order to transfer loads to the supporting structural elements only with tension. The first step of the design of tensile membrane structures, the formfinding, always leads to doubly curved shapes. The next step of the design is the determination of the cutting pattern on the basis of the doubly curved equilibrium shape. The cutting pattern gives the 2D coordinates of the material stripes for the manufacturing. The third step of the design is the structural analysis, the determination of the membrane forces, displacements, member forces in the supporting structure and the reaction forces due to wind and snow load.

The wind load analysis of tensile membrane structures is a critical question. Not only the maximum membrane stresses, due to wind load, have to be compared with the tensile strength of the membrane material, but the slack areas and the displacements have to be analysed also, to avoid the undesirable fluttering which in the worst case can lead to the collapse of the structure. The main difficulty of the wind analysis is the determination of the pressure coefficients of the doubly curved membranes. Since the different design codes do not provide the pressure coefficients of complex hyperbolic and elliptic shapes, those can be determined on the basis of more or less rough approximations or by the help of costly and time consuming wind tunnel tests. Conventionally, in wind tunnels the pressure coefficients of tensile membrane structures are determined on rigid models and the effect of the typically large deformations of the membranes on the pressure coefficients is not taken into account. The aim of the research is to determine and compare the pressure coefficient fields of different membrane structures by the help of wind tunnel tests and computational fluid dynamics (CFD) calculations and to analyse the effect of the displacements of membrane structures on the pressure coefficients. Experience in wind tunnel tests is a preference.