Calculation of the ultimate plastic state of thick-walled pipe bend in the circumferential direction

An engineering approach to determine the ultimate state of pipe bend in the circumferential direction is proposed. The essence of the approach is in the realization of several sequential steps. At the first stage, a separate action of certain groups of external loads by means of the semi-inverse method of Saint Venant is considered. Then, a reduction coefficient for internal moments is determined in the case of the simultaneous action of external bending moments and internal pressure. Finally, a general approach is proposed to the calculation of the ultimate state at the prescribed point of the bend section for the resulting system of internal force factors: the bending moment and tensile force in the circumferential direction, longitudinal and tangential forces, The possibility is indicated for the use of the results obtained to take into account cracks and three-dimensional defects available in the pipe bend. (C) 1998 Elsevier Science Limited.