Limit loads for pipe elbows subjected to in-plane opening moments and internal pressure

The purpose of this study is to determine limit loads for pipe elbows subje cted to in-plane bending moments that tend to open the elbow (i.e., increas e its radius of curvature), and the influence of internal pressure on the v alue of the limit fond. Load-deflection curves were obtained, and from thes e curves plastic collapse and instability loads at various values of intern al pressure were determined. This was done for different pipe bend factors (h = Rt/r(2)) using the nonlinear finite element analysis code (ABAQUS) wit h its special elbow element. A set of limit curves was generated from the r esults. These nines show the variation of collapse and instability lends wi th internal pressure for different elbows. Collapse loads were found to inc rease and then decrease with increasing pressure for all the elbow geometri es studied. Instability loads were difficult to reach because of the large stiffening effect of the elbow cross-sectional deformation, and they were g enerally found to decrease with increasing pressure.