| Summary: | Specialization: Structural Engineering Degree: Doctor of Philosophy Abstract: Pipeline structures can be subjected to excessive tensile strains due to a variety of environmental agents including but not limited to slope instabilities, seismic forces, freezing and thawing cycle of the permafrost in arctic regions. In addition to environmental and geotechnical effects, large strains can also occur during offshore pipe laying operations using reeling. Another occasion where the increase of the tensile strains can cause damage to pipelines and the environment is the accumulation of strains in the vicinity of cold bends. Experimental research showed that tension side fracture of cold bends is a probable mode of failure albeit being mostly overlooked in practice. This mode of failure due to tensile strain is highly dangerous because of the explosion associated with it in case of gas carrying pipelines. Therefore further study of that failure mode is necessary in order to identify the conditions leading to it. In the recent years a strain based design approach is increasingly adopted in the management of pipeline systems in order to guarantee a safe and economical pipeline operation. An integral part of the strain based design methodology is the prediction of the tensile strain capacity of pipeline structures under a combination of external forces, in the presence of defects in the pipe wall which can be caused due to corrosion or imperfections in the manually or automatically manufactured girth welds. The presence of pipe wall flaws due to corrosion is especially critical in case of vintage pipes which constitute a large portion of the Canadian pipeline network. On the other hand the tensile strain capacity prediction equations currently available in the literature are not applicable to vintage pipes with low yield strength. Therefore, there is a dire need for the study of vintage pipes in order to have a better understanding of their structural response under tensile strain. In the scope of this research program the ...
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