Failures of 108‐Inch Steel Pipe Water Main

Abstract

The paper describes the analysis of failures of a 108‐in. (2.74 m) diameter steel pipe water main. Total pipe separations occurred because of large unrelieved thermal stresses and stress amplification caused by the eccentricity of the welded bell‐and‐spigot joints. The pipeline designer ignored these aspects in his design, thus grossly underestimating the stresses in the pipe. This could easily have been recognized by performing an elementary longhand calculation. The failure analysis described in this paper demonstrates that the asdesigned pipeline was incapable of safely withstanding even the incorrectly defined design conditions. The designer attributed the failures to low toughness of the bell steel. Conversions of Charpy impact test data and J‐integral analysis of compact tension test data are used to demonstrate that the steel had normal fracture toughness. Nonlinear finite element stress analysis and elasticplastic fracture mechanics demonstrate that for the measured range of fracture toughness the failures were inevitable.