CHARACTERISTICS OF ARCHITECTURAL MEMBRANE MATERIALS UNDER BIAXIAL TENSILE LOADS

Through biaxial tensile tests of architectural membrane materials at seven warp to weft stress ratios , which are 0∶1, 1∶5, 1∶2, 1∶1, 2∶1, 5∶1 and 1∶0 respectively, tensile performances of the samples under biaxial tensile loads are analyzed. The cyclic load pattern with three cycles is applied for the purpose that after cyclic loads, the experimental properties of membrane materials will agree well with actual properties of membrane materials applied in structures. The test results show that the behavior of membrane materials is highly nonlinear and anisotropic under biaxial tensile loads. A model is developed to build relationships between warp strains and weft strains. Combined with the deformation characteristics obtained from the test, the phenomenon that the elastic constant in the warp direction is negative while C 0.5 is studied. With the analysis of biaxial elastic constants of membrane materials, it is obtained that at the condition of C=1, there are the biggest elastic constants in the both warp and weft directions.