Abstract | Buckling and post-buckling behavior of beams resting on elastic foundation is addressed in the present study, as a first step towards modeling upheaval buckling of buried pipelines. The mathematical model used is that of a simply-supported Winkler beam supported laterally by uniformly distributed transverse springs, which is subjected to constant axial force over its length. Elastic critical buckling loads and corresponding eigenmodes are first obtained analytically, by formulating equilibrium equations in the deformed configuration and deriving and solving the corresponding buckling equation. The results are compared with results from linear buckling analyses of finite element models and indicate buckling mode cross-over with respect to soil stiffness. Then, geometrically nonlinear analyses with imperfections (GNIA) are performed, indicating descending post-buckling paths, thus unstable post-buckling behavior as well as buckling mode interaction for certain ranges of values of soil stiffness.