Strength Model Uncertainties of Burst, Yielding, and Excessive Bending of Piping

Abstract

Nuclear safety-piping is designed according to the ASME Boiler and Pressure Vessel Code, Sections III, NB-, NC-, and ND-3600 that use the allowable stress design method (ASD). The potential use instead of reliability-based design equations for nuclear piping could benefit the structural design by providing, among others, consistent reliability levels for piping. For the development of such equations, not only the probabilistic characteristics of the design variables are needed, but also the quantification of the uncertainties introduced by the strength models that are used in order to estimate the resistance of pipes subjected to different loadings. This paper evaluates strength models, and therefore provides necessary information for the reliability-based design of pipes for burst or yielding due to internal pressure and for excessive bending.

Quantification of the uncertainty in stress index B2 for pipe bends subjected to out-of-plane bending

“…Note that the dimensions of this pipe bend change for each simulated geometry. The pipe material is 'ductile' stainless steel (Type 304) and, similar to other studies conducted recently [3,7], this material is assumed to follow an elastic-perfectly plastic stress-strain behaviour. However, the straight parts of the pipe are considered to be purely elastic in order to force the plastic collapse to occur within the bend part.…”