Stress-strain state of a pipeline subject to the influence of a combined load

Theoretical and experimental study of the stress-strain state of a pipeline under the influence of two types of loads was carried out: 1) bending force in vertical plane; 2) combined action of bending force in vertical plane and internal pressure. The experiments were performed on a pipe sample: steel grade Ст3, outside diameter 114 mm, wall thickness 4.5 mm, length 0.94 m. Hoop and longitudinal strains were measured in different areas of the pipe sample wall under the bending force in the vertical plane. To determine other parameters of the pipe stress-strain state the theories of thick-walled and thin-walled cylindrical shell, the Hooke’s law, the Zhuravsky–Vlasov formula for calculating the greatest shear stress in a circular tube, the principle of superposition were used. The distributions of the stress-strain state parameters (hoop, longitudinal, radial strains; hoop, longitudinal, shear stresses; von Mises stress) of the pipe sample wall around the perimeter of different pipe cross sections are found. It is revealed that hoop and shear stresses have a significant effect in the considered cases of loading. The values of hoop and shear stresses should be taken into account when calculating von Mises stress and assessing strength of the main pipeline according to the maximum-distortion-energy theory.