When large diameter pipelines are to be laid in deep waters (e.g. a 40" pipe in 350m water depth), dynamic response to laybarge motions induced by encountered seastates is a prime issue for assessing pipe layability. Large inertial forces to submerged weight ratio can be held responsible for unacceptable pipe response to even mild seastates. This could be the case of challenging pipelay scenarios envisaged for the Mid-90's. After a brief introduction of present development needs of offshore pipeline technology, in this paper: 1) currently in use analysis methods for the simulation of laying dynamics and procedures for the definition of limit seastates, will be introduced and discussed; 2) laying criteria for the acceptable state of stress and strain on the overbend and the sagbend, currently in force, will be reviewed and commented; 3) a series of applications, showing main parameters affecting pipelay dynamics, will be presented and recommendations for laying large diameter pipelines in deep waters given.
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