Nonlinear Analyses using Spline Functions

Cubic spline functions are utilized for functional representation of nonlinear stress-strain curves, and are found to provide satisfactory approximations to stress, strain, and moduli required for nonlinear stress-deformation analyses of geologic media. Stresses, strains and moduli from spline and hyperbolic representations are compared. The spline approximation is used in finite element analyses to predict load-displacement behavior of a model test footing resting on a cohesive soil. Comparisons are also obtained between load-displacement curves computed from the spline and the hyperbolic representations, and the experimental curve. Spline approximation provides good correlation over complete range of deformation history. Effects of the magnitude of initial tangent stiffness on the load-deformation behavior are briefly studied.