Evaluation of long-term extreme response statistics of jack-up platforms

2002 ◽  
Vol 29 (13) ◽  
pp. 1603-1631 ◽  
Author(s):  
M.J. Cassidy ◽  
P.H. Taylor ◽  
R. Eatock Taylor ◽  
G.T. Houlsby
Keyword(s):  
Extreme Response ◽  
Jack Up

Efficient Analysis of a Catenary Riser

2006 ◽  
Author(s):  
Elizabeth Passano ◽  
Carl M. Larsen
Keyword(s):  
Operating Conditions ◽  
Stochastic Simulations ◽  
Worst Case ◽  
Nonlinear Structure ◽  
Tension Response ◽  
Extreme Response ◽  
Analysis Strategies ◽  
Low Tension ◽  
Term Response

The paper deals with the challenge of predicting the extreme response of catenary risers, a topic of both industry and academic interest. Large heave motions introduced at the upper end of a catenary riser can lead to compression and large bending moments in the region immediately above the touch down area. In the worst case, dynamic beam buckling may occur. The focus of the paper will be on understanding the riser behaviour in extreme, low-tension response and in establishing suitable analysis strategies to predict the extreme response. Results from long nonlinear stochastic simulations of many sea states with varying environmental and operating conditions may be combined to describe the long-term response of a nonlinear structure such as a catenary riser. However, this theoretically straight-forward approach is very demanding computationally and ways to limit the extent of nonlinear stochastic simulations are therefore sought. The usefulness of simpler methods such as regular wave analysis to improve understanding of the physical behaviour and to aid in concentrating the nonlinear simulations to where they are most useful, will be demonstrated.

Extreme-response analysis of jack-up platforms

1989 ◽  
Vol 2 (3-5) ◽  
pp. 305-334 ◽  
Author(s):  
H. Kjeøy ◽  
N.G. Bøe ◽  
T. Hysing
Keyword(s):  
Response Analysis ◽  
Extreme Response ◽  
Jack Up

Extreme Response Predictions for Jack-Up Units in Second Order Stochastic Waves by FORM

2007 ◽  
Author(s):  
Jo̸rgen Juncher Jensen
Keyword(s):  
Second Order ◽  
Sea State ◽  
First Order ◽  
Reliability Method ◽  
Extreme Response ◽  
Stochastic Waves ◽  
Short Time ◽  
Wave Induced ◽  
Jack Up ◽  
Operational Time

The aim of the present paper is to advocate for a very effective stochastic procedure, based on the First Order Reliability Method (FORM), for extreme value predictions related to wave induced loads. All kinds of non-linearities can be included, as the procedure makes use of short time-domain simulations of the response in question. The procedure will be illustrated with a jack-up rig where second order stochastic waves are included in the analysis. The result is the probability of overturning as function of sea state and operational time.

Reliability of TLP Tendons Under Storm Sea States

2005 ◽  
Author(s):  
Federico Barranco Cicilia ◽  
Edison Castro Prates de Lima ◽  
Lui´s Volnei Sudati Sagrilo
Keyword(s):  
Reliability Analysis ◽  
Limit State ◽  
Nonlinear Dynamic Analysis ◽  
Analytical Models ◽  
Cumulative Probability ◽  
Wave Forces ◽  
Ultimate Limit State ◽  
Sea State ◽  
Extreme Response

This paper presents a methodology for reliability analysis of Tension Leg Platform (TLP) tendons subjected to extraordinary sea state conditions like hurricanes or winter storms. A coupled approach in time domain is used to carry out TLP random nonlinear dynamic analysis including wind, current and first and second order wave forces. The tendons Ultimate Limit State (ULS) condition is evaluated by an Interaction Ratio (IR) taking into account dynamic combination among tension, bending and hydrostatic pressure. Expected long-term extreme IR is obtained through the integration of cumulative probability functions (CPFs) fitted to response maxima associated to individual short term sea states. The reliability analysis is performed using a time-integrated scheme including uncertainties in loads, tendon strength, and analytical models. Failure probabilities for the most loaded tendon of a TLP in Campeche Bay, Mexico, considering a 100-yr design sea state and the 100-yr extreme response generated by long-term observed storms are compared.

A Monte Carlo Approach to Prediction of Extreme Response Statistics of Drag Dominated Offshore Structures

2007 ◽  
Author(s):  
A. Naess ◽  
O. Gaidai
Keyword(s):  
Monte Carlo ◽  
Weather Conditions ◽  
Offshore Structures ◽  
Drag Forces ◽  
Wave Elevation ◽  
The Monte Carlo Method ◽  
Strong Current ◽  
Highly Nonlinear ◽  
Extreme Response

The focus of the present paper is the extreme response statistics of drag dominated offshore structures subjected to harsh weather conditions. More specifically, severe sea states both with and without strong current are considered. The nature of the hydrodynamic forces acting on the structure becomes highly nonlinear. Additionally to the drag forces, the so called inundation effect due to the wave elevation, corrected to include second order waves, is also taken into account. In the present paper the Monte Carlo method along with a special extrapolation technique is applied. The proposed method opens up the possibility to predict simply and efficiently long-term extreme response statistics, which is an important issue for the offshore structures design.

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