Model for Beam-Mode Buckling of Buried Pipelines

An attempt at modeling the so-called "beam mode buckling" exhibited under compression in pipelines is presented. The line is modeled as a long heavy beam on a contacting surface. The reacting surface is modeled first as an elastic and subsequently as a rigid foundation, with the additional constraint that it only reacts to compressive loads. The problem is assumed to possess a localized imperfection. Under compressive axial load, a section of the beam lifts off the foundation. The problem is studied through a large deflection extensional beam nonlinear formulation. The large deflection response of the beam is found to exhibit a limit load which is shown to be imperfection sensitive. A parametric study of the problem as well as a number of examples with actual pipeline parameters are presented.