Field developments in remote areas of deep water offshorernrequire the services of long distance pipeline systems. Designrnand installation of pipelines in deep waters are expensive.rnSeabed terrain in deep water is rough and more numbers ofrnunsupported spans of long lengths are expected. Designrnagainst vortex induced vibration (VIV) is of concern for thernreliability and cost of deepwater pipelines.rnThe practice of design against VIV has been to limitrnallowable span lengths such that onset of VIV cannot berninitiated. This is a highly conservative approach resulting inrnexpensive span corrections. Probability of occurrences ofrncurrent velocities at seabed reaching critical is very low,rnhence, it is proposed that the designs be based on actualrnfatigue damage. This is also recognized by DnV Guidelinern14 (June 1998).rnExisting methods of VIV response calculation producernextreme response, which leads to conservative fatiguerndamages. Based on a non-dimensional analysis and fittingrnmodel test results an empirical relation, as a function ofrnReynold’s number, reduced velocity, and reduced damping, isrnproposed. The formula determines equivalent response,rnwhich represents overall fatigue accurately.
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