Critical buckling strains in energy pipelines

The research reported herein investigates the critical buckling strain of segments of energy pipeline subjected to combined loads. Critical buckling strain equations from literary sources, including the current Canadian Standard, were evaluated using previously collected U of A test results. All of the equations investigated did a poor job of modeling the U of A experimental data. This indicates that there is a need to develop new equations with better predictive abilities.; This research is divided into three parts. The first part involves expanding the current experimental database for segments of energy pipeline at the University of Alberta by testing specimens with a diameter-to-thickness (D/t) ratio of 92 under combined axial load, internal pressure and increasing monotonic curvature. The influence of a circumferential girth weld was also investigated. Initial imperfections present in the segments of line pipe were investigated, including the development of a technique for quantify them.; The second part of this research was the development and validation of a finite element analysis (FEA) model to predict the observed global and local experimental behaviour. The FEA model was explicitly developed to predict the behaviour of the experimental specimens with the D/t ratio of 92 tested in part 1 and was capable of incorporating initial imperfection patterns. Further validation of the FEA model was done using previously collected experimental data from the U of A for specimens with D/t ratios of 51 and 64.; The final part of this research was to develop new critical buckling strain equations. Once the FEA model was validated, critical parameters that influence the critical buckling strain for energy pipelines were identified and a typical range for each parameter was selected based on the limits of the experimental database. A parametric study examining the effects of each of these parameters was conducted. The results of the parametric study were used to develop critical buckling strain equations that account for each of the different influencing parameters. The proposed equations were then validated with critical buckling strains from data sources external to the U of A to validate their predictive ability.