抄録
The biaxial stress-strain curves of PTFE-coated glass fiber (specimen A) and PVC-coated polyester fiber (specimen B) plain-weave fabrics were measured by maintaining the ratio of warp stress/fill stress at 1/1, 2/1 and 1/2. The extension curves, especially that of specimen A, showed peculiar high nonlinearity which was evident in the fill extension curves consisting of the parts of very small slope in the lower stress region and of steep slope in the stress region later. For the precise and practical structural analysis of membrane structure, the author presented a method of multi-step-linear approximation to the extension curves measured on many stress ratio conditions corresponding to a variety of biaxial deformation states in the real structure. The least square method was applied, and the error, which results from the approximation of elastic constants in the constitutive equation for each secant line through the extension curve, was made to be minimum in this method. By applying the method, the three-step-linear approximation was conducted on the specimens and the errors were evaluated. According to the result of the approximation, the accuracy was good for the practical application but was not so sufficient about the fill extension curve of specimen A. However, it can be generally said that the present method can be applied for the elastic structural analysis of membrane structures.
