7 - Buckling and Collapse Under Combined External Pressure and Tension

Abstract

This chapter discusses buckling and collapse under combined external pressure and tension. In several important offshore and onshore oil exploration and production applications, long and tubular structures are held suspended in either vertical or catenary-shaped positions in water head that often extend up to several thousand feet. In such configurations, the submerged weight of the pipe must be supported at the top, resulting in significant build-up of axial tension in a structure. Although the tensile force decreases as the depth increases, there can be sections that simultaneously experience significant external pressure and axial tension. Buckling and collapse of long tubes under combined axial tension and external pressure are influenced by the same problem parameters as the pure external pressure problem. They mainly depend on the material elastic modulus and yield stress, on the tube D/t, and on initial ovality. The main effect of tension is that it interacts with the circumferential stress and lowers the pressure at which the pipe yields.