Seabed Interaction Modeling Effects on the Global Response of Catenary Pipeline: A Case Study

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Hany Elosta ◽  
Shan Huang ◽  
Atilla Incecik
Keyword(s):  
Fatigue Damage ◽  
Interaction Model ◽  
Fatigue Performance ◽  
Random Waves ◽  
Floating Platform ◽  
Geotechnical Parameters ◽  
Steel Catenary Riser ◽  
Considerable Uncertainty ◽  
Interaction Modeling ◽  
Seabed Interaction

A steel catenary riser (SCR) attached to a floating platform at its upper end encounters oscillations in and near its touchdown zone (TDZ), which results in interaction with the seabed. Field observations and design analysis of SCRs show that the highest stress and greatest fatigue damage occurred near the touchdown point where the SCR first touches the seabed soil. The challenges regarding the fatigue damage assessment of an SCR in the TDZ are primarily because of the nonlinear behavior of SCR–seabed interaction and considerable uncertainty in seabed interaction modeling and geotechnical parameters. Analysis techniques have been developed in the two main areas: SCR–seabed interaction modeling and the influence of the uncertainty in the geotechnical parameters on the dynamic response and fatigue performance of SCRs in the TDZ. Initially, this study discusses the significance of SCR–seabed interaction on the response of an SCR for deepwater applications when subjected to random waves on soft clay using the commercial code OrcaFlex for nonlinear time domain simulation. In the next step, this study investigates the sensitivity of fatigue performance to geotechnical parameters through a parametric study. It is proven that employing the improved lateral SCR–seabed interaction model with accurate prediction of soil stiffness and riser penetration with cyclic loading enables us to obtain dynamic global riser performance in the TDZ with better accuracy. The fatigue analyses results prove that the confounding results indicated by the previous research studies on the SCR in the TDZ are due to different geotechnical parameters imposed with the seabed interaction model. The main benefit of employing nonlinear seabed approach is to capture the entity of realistic soil interaction behavior in modeling and analysis and to predict the likelihood of the fatigue damage of the SCR with seabed interaction, thereby minimizing the risk of the loss of the containment with the associated environmental impact.

Seabed Interaction Modelling Effects on the Global Response of Catenary Pipeline: A Case Study

2013 ◽  
Author(s):  
Hany Elosta ◽  
Shan Huang ◽  
Atilla Incecik
Keyword(s):  
Fatigue Damage ◽  
Linear Time ◽  
Interaction Model ◽  
Fatigue Performance ◽  
Random Waves ◽  
Floating Platform ◽  
Geotechnical Parameters ◽  
Non Linear ◽  
Interaction Modelling ◽  
Seabed Interaction

A steel catenary riser (SCR) attached to a floating platform at its upper end encounters oscillations in and near its touchdown zone (TDZ), which results in interaction with the seabed. Field observations and design analysis of SCRs show that the highest stress and greatest fatigue damage occurred near the touchdown point where the SCR first touches the seabed soil. The challenges regarding the fatigue damage assessment of an SCR in the TDZ are primarily because of the non-linear behaviour of SCR–seabed interaction and considerable uncertainty in seabed interaction modelling and geotechnical parameters. Analysis techniques have been developed in the two main areas: SCR–seabed interaction modelling and the influence of the uncertainty in the geotechnical parameters on the dynamic response and fatigue performance of SCRs in the TDZ. Initially, this study discusses the significance of SCR–seabed interaction on the response of an SCR for deepwater applications when subjected to random waves on soft clay using the commercial code OrcaFlex for non-linear time domain simulation. In the next step, this study investigates the sensitivity of fatigue performance to geotechnical parameters through a parametric study. It is proven that employing the improved lateral SCR-seabed interaction model with accurate prediction of soil stiffness and riser penetration with cyclic loading enables us to obtain dynamic global riser performance in the TDZ with better accuracy. The fatigue analyses results prove that the confounding results indicated by the previous research studies on the SCR in the TDZ are due to different geotechnical parameters imposed with the seabed interaction model. The main benefit of employing non-linear seabed approach is to capture the entity of realistic soil interaction behaviour in modelling and analysis and to predict the likelihood of the fatigue damage of the SCR with seabed interaction, thereby minimising the risk of the loss of the containment with the associated environmental impact.

Effects of Nonlinear Riser-Soil Interaction Model on Fatigue Design of Steel Catenary Riser Under Random Waves

2017 ◽  
Author(s):  
Mehrdad Kimiaei
Keyword(s):  
Oil And Gas ◽  
Structural Response ◽  
Interaction Model ◽  
Nonlinear Behavior ◽  
Random Waves ◽  
Steel Catenary Riser ◽  
Oil And Gas Fields ◽  
Fatigue Design ◽  
Time Histories ◽  
Main Components

Steel Catenary Risers (SCRs) are one of the main components in development of oil and gas fields in deep waters. Fatigue design of SCRs in touch down zone (TDZ) is one of the main engineering challenges in design of riser systems. Nonlinear riser-soil interaction models have recently been introduced and used widely in advanced structural analysis of SCRs. Due to hysteretic nonlinear behavior of the soil, SCR system will show different structural response under different loading time histories. This paper investigates the effects of nonlinear riser-soil interaction in the TDZ on fatigue performance of an example SCR subjected to randomly generated waves. Sensitivity of fatigue life of the system, location of the critical node and the maximum stress range to different wave realizations and different soil types are discussed in detail.

Study of Seabed Trench Induced by Steel Catenary Riser and Seabed Interaction

2016 ◽  
Author(s):  
Kunpeng Wang ◽  
Ying Min Low
Keyword(s):  
Frequency Response ◽  
Static Analysis ◽  
Fatigue Damage ◽  
Surrogate Model ◽  
Unit Length ◽  
Low Frequency ◽  
Steel Catenary Riser ◽  
Cubic Polynomial ◽  
Seabed Interaction ◽  
Touchdown Point

Seabed trench profile has significant effect on the fatigue damage of steel catenary riser near touchdown point. This study briefly demonstrates an approach in literature to determine the seabed trench induced by wave frequency response based on the cubic polynomial model. In this approach, a criterion for the matching between catenary riser and seabed trench is proposed, which is an optimization problem, and needs iterative static analysis of catenary riser. Based on the criterion, the sensitivity of the trench length and position to three parameters is parametrically studied: riser mass per unit length, ratio of horizontal span to vertical span of catenary part, trench depth. The obtained data are employed to fit the equations of trench length and position, which is taken as surrogate model since the iterative static analysis is very complicated. For completeness, the validation against data obtained from hysteretic seabed model is also illustrated. Based on the surrogate model, this study investigates the effect of trench depth on the fatigue damage near touchdown and the effect of the low frequency response on the seabed trench, and some useful conclusions are obtained.

Review of Steel Lazy Wave Riser Concepts for North Sea

2015 ◽  
Author(s):  
Airindy Felisita ◽  
O. T. Gudmestad ◽  
Daniel Karunakaran ◽  
Lars Olav Martinsen
Keyword(s):  
Fatigue Damage ◽  
Fatigue Performance ◽  
Harsh Environments ◽  
Harsh Environment ◽  
Wave Shape ◽  
Lower Stress ◽  
Steel Catenary Riser ◽  
Wave Heights ◽  
Norwegian Continental Shelf ◽  
Wave Shapes

The Steel Catenary Riser (SCR) is considered a favorable solution for deepwater development. However, the application of SCRs in harsh environments is challenging, mainly due to fatigue at the touch down zone. One of the solutions to improve SCRs’ fatigue performance is the application of buoyancy modules in order to achieve a Steel Lazy Wave Riser (SLWR) configuration. This paper presents a parametric study of a SLWR system for application in deepwater and harsh environments. The selected harsh environment is the seas within the Norwegian Continental Shelf. The main geometric variations are the length of the buoyancy section and the dimension of the buoyancy modules. These variations result in riser configurations with different riser’s wave heights. The term ‘riser’s wave height’ refers to the vertical distance between the lowest point at sagbend and the highest point at hogbend of a riser. The analysis works are performed using Orcaflex. The results show that the application of buoyancy modules help to improve the performance of a steel catenary riser for application in a harsh environment. The dimension of a riser’s wave shape proves to be an important factor that controls strength and fatigue performance of a riser. Lazy wave riser configurations with larger and better defined wave shapes have lower stress utilizations and lower fatigue damage, while riser configurations with smaller wave shapes have higher stress utilizations and higher fatigue damage. This is due to lazy wave configurations with higher wave shape have better capability to absorb the dynamic loads.

Effect of Interaction Modeling in AFM-Based Nanomanipulation

2008 ◽  
Author(s):  
Fakhreddine Landolsi ◽  
Fathi H. Ghorbel ◽  
James B. Dabney
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Interaction Model ◽  
Collision Process ◽  
Visual Sensing ◽  
Proposed Model ◽  
Interaction Modeling

AFM-based nanomanipulation is very challenging because of the complex mechanics in tip-sample interactions and the limitations in AFM visual sensing capabilities. In the present paper, we investigate the modeling of AFM-based nanomanipulation emphasizing the effects of the relevant interactions at the nanoscale. The major contribution of the present work is the use of a combined DMT-JKR interaction model in order to describe the complete collision process between the AFM tip and the sample. The coupling between the interactions and the friction at the nanoscale is emphasized. The efficacy of the proposed model to reproduce experimental data is demonstrated via numerical simulations.

A Flexible Connector Design for Multi-Modular Floating Structures

2018 ◽  
Author(s):  
Huai Zhao ◽  
Daolin Xu ◽  
Haicheng Zhang ◽  
Qijia Shi
Keyword(s):  
Finite Element Method ◽  
Structural Model ◽  
Random Waves ◽  
The Finite Element Method ◽  
Floating Platform ◽  
Stiffness Analysis ◽  
Floating Structures ◽  
Extreme Loads ◽  
Strength And Stiffness ◽  
Frequency Domain Approach

The paper aims to provide a novel flexible connector model for the connection of a multi-modular floating platform. The structural model of the connector is presented. To evaluate connector loads, the governing equation for a modularized floating platform is established using the Rigid Module Flexible Connector (RMFC) model. The dynamic analysis for a two-module floating platform is carried out by using the frequency domain approach in random waves and the extreme loads of the flexible connector are estimated. The finite element method is applied for strength and stiffness analysis to assess the performance of the connector.

Sensitivity Study of Critical Parameters Influencing the Uncertainty of Fatigue Damage in Steel Catenary Risers

2010 ◽  
Author(s):  
Feng Zi Li ◽  
Ying Min Low
Keyword(s):  
Fatigue Damage ◽  
Cost Effective ◽  
Sensitivity Study ◽  
Structural Safety ◽  
Critical Parameters ◽  
Design Parameters ◽  
Steel Catenary Riser ◽  
Bending Stresses ◽  
Steel Catenary Risers ◽  
Touchdown Point

The most challenging aspect of a deepwater development is the riser system, and a cost-effective choice is the Steel Catenary Riser (SCR). Fatigue is often a governing design consideration, and it is usually most critical at the touchdown point (TDP) where static and dynamic bending stresses are highest. Unfortunately, it is also at this region that uncertainty is the maximum. The increased uncertainty casts doubt on the applicability of generic safety factors recommended by design codes, and the most consistent way of ensuring the structural safety of the SCR is to employ a reliability-based approach, which has so far not received attention in SCR design. As the number of basic random variables affects the complexity of a reliability analysis, these variables should be selected with caution. To this end, the aim of this paper is to draw up a comprehensive list of design parameters that may contribute meaningfully to the uncertainty of the fatigue damage. From this list, several parameters are selected for sensitivity studies using the commercial package Orcaflex. It is found that variations in seabed parameters such as soil stiffness, soil suction and seabed trench can have a pronounced influence on the uncertainty of the fatigue damage at the touchdown point.

Using the Three-Stage Weibull Equation and Tree-Based Model to Characterize the Mix Fatigue Damage Process

2005 ◽  
Vol 1929 (1) ◽  
pp. 227-237 ◽  
Author(s):  
Bor-Wen Tsai ◽  
John T. Harvey ◽  
Carl L. Monismith
Keyword(s):  
Crack Initiation ◽  
Fatigue Damage ◽  
Fatigue Tests ◽  
Fatigue Performance ◽  
Data Set ◽  
Warm Up ◽  
Weibull Parameters ◽  
Damage Process ◽  
Initiation Stage ◽  
Weibull Equation

The primary purpose of this paper is to demonstrate the applicability of the three-stage Weibull equation to describe the fatigue damage process using flexural controlled deformation fatigue tests. A data set of 179 beam fatigue tests originally designed for exploring the fatigue performance of conventional dense graded asphalt concrete (DGAC) and asphalt–rubber hot-mix gap-graded (ARHM-GG) mixes was used to inspect the three-stage Weibull parameters that were estimated using a genetic algorithm. The tree-based regression–category models were then used to uncover the data structure of the estimated parameters as a function of material properties, conditioning methods, temperatures, compaction methods, and strain levels. In general, the three-stage Weibull equation provides satisfactory fitting results for the three-stage fatigue damage process occurring in a beam test. It was found that the tree-based models of three-stage Weibull parameters associated with the crack initiation stage were statistically adequate and reliable compared with the models of parameters related to the warm-up stage and the crack propagation stage. It might suggest that these crack initiation parameters are better indexes to assess the fatigue performance.

Vortex Induced Motion of TLP With Consideration of Appurtenances

2014 ◽  
Author(s):  
Jaime Hui Choo Tan ◽  
Yih Jeng Teng ◽  
Allan Magee ◽  
Benedict Toong Heng Ly ◽  
Shankar Bhat Aramanadka
Keyword(s):  
Cfd Simulation ◽  
Scale Effects ◽  
Floating Platform ◽  
Steel Catenary Riser ◽  
Aspect Ratios ◽  
Significant Difference ◽  
Helical Strakes ◽  
Induced Motion ◽  
Set Up ◽  
Comparison Of The Results

Offshore floating platform configurations often consist of geometrically simple and symmetrical shapes which are made complicated by the presence of appurtenances such as helical strakes, tendon porches, steel catenary riser (SCR) porches, pipes, chains, fairleads and anodes on the surface of the hull. Previous studies mainly on spars show that these hull external features affect the Vortex Induced Motion (VIM) performance of the platform significantly. This is to be expected since VIM is controlled by the flow separation on the hull surface and the resulting vortex shedding patterns. Scale effects may also play a role in model tests for bare cylinders or hulls with bare cylindrical columns, whereas previous studies have shown less Reynolds dependence when appurtenances are modelled. This study investigates the effect of hull appurtenances on VIM of a multi-column floating platform, i.e. a Tension Leg Platform (TLP) designed for Southeast Asian environment. Significant difference in VIM behaviors is expected between spars and TLPs since the column aspect ratios are very different and TLPs do not have helical strakes that are commonly fitted on spars. Model testing and Computational Fluid Dynamics (CFD) simulation are used in this VIM study, with the former being the emphasis of this paper. Descriptions of the respective experimental and numerical methodologies are presented and the comparison of the results is made. Further work required to improve the model test set-up and the CFD simulation are suggested. From this study, it is shown that the effect of appurtenances on TLP VIM simulation is important and must be taken into account to obtain realistic results.

Sign in / Sign up

Export Citation Format

Share Document