In recent years the residual curvature method (RCM) has been used to provide buckle initiators to control and mitigate the global buckling of pipelines. Through the appropriate planning of these controlled buckles, an acceptable design of the pipeline in-place behaviour is achieved. Implementation of the residual curvature (RC) profile in the context of reel-lay installation is obtained by the modification of the vessel’s straightener settings on the sections of pipe where buckle initiators are required. This leads to a local and controlled increase of the pipeline RC.
The published literature on in-place assessment for a limited number of recent projects has considered that a local increase in curvature is achieved by subjecting the pipeline to pure bending until the target residual plastic strain is reached. This method simplifies the actual reel-lay process where the pipeline is subjected to successive bending cycles before the RC is achieved after the pipeline leaves the installation vessel. Consequently, the approach does not capture the whole complexity of the reeling process.
This paper assesses the effect of the approach used to induce pipe local curvature on the results of the in-place analysis, where the behaviour of the pipeline with RC buckle initiators is examined. From this, it draws conclusions on the complexity required to adequately represent the effect of the RCM on the in-service behaviour and the design life of pipelines.