This paper theoretically investigates the effect of axial tensile strain on the plastic yield load-carrying capacity of pipelines. The elasticity theory and three plastic yield criteria of Tresca criterion, von Mises criterion, and Average Shear Stress Yield (ASSY) criterion are adopted in the analysis. General solutions of elastic stresses and strains are obtained for a thin-walled, end-caped pipe subjected to internal pressure and an axial strain that is used to represent the outside applied force. Based on the three plastic yield criteria, different nonlinear governing equations are obtained for determining the yield pressure, the yield hoop and axial stresses as well as the yield hoop and radial strains for the pipe. The results showed that the pressure, stresses and strains in the pipe at yield are functions of the axial strain, Poisson’s ratio, Young’s modulus, and yield strength of the pipe steel. The tensile strain limits are then obtained for different pipeline grades. It is concluded that the axial tensile strain can significantly reduce the limit load or the regulation-allowed operating pressure, and the tensile strain limits should be considered in strain-based design to prevent pipeline failure.
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