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

Over the last decade, the requirement for moving from a deterministic design to a more rational reliability-based load and resistance factor design (LRFD) guideline has been emphasised in the area of pressure vessel and piping. For reliability-based code calibration of pipe bends, a quantification of the uncertainty in the primary stress indices (for pressure B-1 and for bending B-2) is the first significant task. This paper presents a Monte Carlo simulation-based probabilistic characterisation of B-2 for Class 2 and 3 Type 304 stainless steel thin pipes with a 90 degrees long radius bend, subjected to out-of-plane flexure. The ASME B&PV Code, Section III equations (NC 3673.2 and ND 3673.2) to calculate B-2 are proposed to be revised using a random variable (K), for which detailed statistics (including the cumulative distribution function) are provided. An alternative equation, based on linear regression analysis, is also suggested which provides a better fit for the B-2 statistics. These information can be used suitably to formulate an LRFD equation for pipe bends. (c) 2012 Elsevier Ltd. All rights reserved.