Fabrication Uncertainty in $B2$ for Nuclear Pipe Bends Subjected to In-Plane Opening Moment

For reliability-based design of pipe bends and elbows, a probabilistic characterization of the primary stress indices (⁠$B1$ and $B2$⁠) is essential. This paper aims at the characterization of the fabrication/geometric uncertainty in $B2$⁠, for thin stainless steel long radius pipe bends, subjected to in-plane opening moment. This characterization is performed in a framework based on Monte Carlo simulation and nonlinear finite element analysis. A revision of the code-based expression for $B2$ is proposed where a random variable K replaces the constant numerator in this expression. The statistics for K are provided for different pipe nominal dimensions, which indicates that the existing provision gives a very conservative estimate of the plastic collapse moment for pipe bends subjected to in-plane opening flexure.