انجمن هیدرولیک ایران
نشریه هیدرولیک
2345-4237
3
4
2009
01
20
Modeling and Estimation of Fatigue Damage Accumulation in Marine Risers of Fixed Platforms
مدل سازی و تخمین عمر خستگی رایزرهای دریایی در سکوهای ثابت
53
61
85482
10.30482/jhyd.2009.85482
FA
امیر
مقیسه
همایون
ریاحی
عباس
رهی
Journal Article
2008
03
22
Offshore gas and oil fields are being discovered and exploited nowadays in water depths of more than<br />2000 m. The operation in depths increases the external forces so that the equipments should be more<br />advanced and expensive. Fatigue damage accumulation is one of the most important problems about<br />marine structures that are exposed to the alternative loads. Riser is one of these structures. The<br />surrounding environment of riser causes alternative stresses and fatigue in riser. To obtaini these<br />stresses, the analysis of the vortex induced vibration in two direction, in-line and cross flow, is<br />necessary. The risers are long relative to their cross sections so that the Euler-Bernoulli theory is<br />applicable for description of the pipe dynamic bending. The flow and riser motion in x direction forms<br />a vortex shedding in front of riser. These vortices cause the drag force in x direction and the lift force<br />in y direction. These forces are time dependent. The drag force is obtained from Morison’s formula.<br />The lift force excites the vibration in y direction. After obtaining the equation of motion and solving it<br />by using numerical methods such as Galerkin, finite difference and Runga-Kutta fourth order method,<br />the riser deflection in two directions will be obtained and the stress at the outer diameter of riser will<br />be calculated. The fatigue damage accumulation in the riser can be obtained by using Shigley theory<br />and Palmgren-Miner rule.
http://jhyd.iha.ir/article_85482_a510b475cb00f1390b74375bfe33f3c7.pdf