Reliability Analysis of a Steel Catenary Riser With Environmental, Geometry, and Operational Uncertainties

2014 ◽  
Author(s):  
C. Y. Ma ◽  
U. Alibrandi ◽  
C. G. Koh
Keyword(s):  
Failure Probability ◽  
Bending Moment ◽  
External Pressure ◽  
Engineering Practice ◽  
Floating Structure ◽  
Steel Catenary Riser ◽  
Waves And Currents ◽  
Uncertainty Parameters ◽  
Environmental Geometry ◽  
Scr Model

Steel Catenary Riser (SCR) offers an attractive solution to deepwater floating structure due to its economical effectiveness, large diameters, high resistance to internal and external pressure, simple and robust installation methods. SCR forms a prolongation of a subsea flowline attached to a fixed platform or a floating unit in a catenary shape. Due to the relatively large motion under waves and currents, SCR lines are sensitive to dynamic effects and vulnerable to damage in deep water. They are commonly subjected to high top tension and large bending moment due to platform or FPSO movements which may lead to fatigue damage. There are many uncertainties that can affect the safety and cost-effectiveness of the SCR. Offshore design codes typically adopt empirical safety factors to account for these uncertainties but this approach does not permit the prediction of failure probability of the riser system. To address the above issue, this paper presents the coupling of the stochastic analysis concept to the deterministic computational model for the dynamic analysis of SCR. The finite element solution is developed for hydrodynamic and structural analysis accounting for nonlinear and dynamic coupling effects. Methods for reduction of dimensionality of uncertainties are investigated to help to make the analysis computationally feasible. Uncertainty and numerical realization of specific uncertainty parameters are modeled through riser dynamics software and uncertainty analysis software. Distributions of effective tension, bending moment, and API RP 2RD stress are illustrated for a specified SCR model. The correlation effects between structural responses and random variables are investigated. In addition, the failure probability of SCR API RP 2RD stress is investigated through Monte Carlo simulations. This will help to evaluate the behavior and reliability of SCR realistically, incorporating the environmental, geometry and operational uncertainties in engineering practice.

Tank Test and Numerical Simulation of Spar Type Floating OTEC

2021 ◽  
Author(s):  
Shunka C. Hirao ◽  
Jun Umeda ◽  
Kentaroh Kokubun ◽  
Toshifumi Fujiwara
Keyword(s):  
Numerical Simulations ◽  
Cold Water ◽  
Scaling Law ◽  
Internal Flow ◽  
Bending Moment ◽  
Floating Structure ◽  
Waves And Currents ◽  
Tank Test ◽  
Safety Assessments ◽  
Ocean Thermal Energy

Abstract National Maritime Research Institute, NMRI, had been studying the analytical method on safety assessments of floating power generation facilities for ten years more. As a part of these studies, an Ocean Thermal Energy Conversion (OTEC) was also studied in our institute. The OTEC normally has a very long and thick Cold-Water Pipe (CWP) with an unanchored end to pump up a large amount of cold-water continuously. From the viewpoints of the safety assessments of the OTEC operation, it is noteworthy to confirm the effect of the existing long pipe against a floating unit/body and an effect of internal flowing water. It is necessary, moreover, to consider the Vortex Induced Vibration (VIV) effect for floater motions and structural analysis of the pipe itself and a connecting point of the floating structure. In this paper, the results of model tests and numerical simulations of a spar type floating OTEC with a single CWP in waves and currents are presented. The CWP model was made of material fitting the scaling law for a planned full scale OTEC. The specific and unique phenomena of the floating OTEC were confirmed from the model test results. Based on the results of the tank tests and the numerical simulations, we confirmed the necessary items and arrangements for safety evaluations. In detail, the internal flow increased the bending moment at the connection point.

Failure Mechanism and Limit Load Capacity of Subsea Pipelines With Dent Defects

2021 ◽  
Author(s):  
Yanfei Chen ◽  
You Zong ◽  
Shaohua Dong ◽  
Yufeng Yan ◽  
Guoyan He ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Load Capacity ◽  
Local Buckling ◽  
Bending Moment ◽  
Limit Load ◽  
External Pressure ◽  
Engineering Practice ◽  
Factors Affecting ◽  
Subsea Pipelines ◽  
The Impact

Abstract With the development of oil and gas resources extending to the deep sea, more and more submarine pipelines are applied, and the importance of the structural and functional integrity of submarine pipelines is becoming more and more prominent. Dent has long been considered one of the potential factors affecting the integrity of submarine pipelines, which can be formed when pipelines are impacted by fallings objects from the sea surface. Due to the seabed subsidence, pipeline suspension and earthquake, mudslide activity and other factors, submarine pipelines may be under bending moment, seriously affecting the safe operation of submarine pipelines. The study of failure and limit load capacity of submarine pipelines under external pressure and bending moment is of great significance. In this paper, the nonlinear finite element method is used to study the collapse failure and local buckling failure of subsea pipelines under external pressure and bending moment respectively. The process of the pipeline being dented by the impact of objects is simulated, spherical denter and wedge-shaped denter are considered. The influence of D/t and dent depth on collapse capacity and bending capacity are investigated. The results can be referred in engineering practice.

Submarine Pipeline Installation JIP: Strength and Deformation Capacity of Pipes Passing Over the S-Lay Vessel Stinger

2006 ◽  
Author(s):  
Enrico Torselletti ◽  
Luigino Vitali ◽  
Erik Levold ◽  
Kim J. Mo̸rk
Keyword(s):  
Water Depth ◽  
Failure Modes ◽  
Bending Moment ◽  
External Pressure ◽  
Submarine Pipeline ◽  
Design Guideline ◽  
Moment Capacity ◽  
Sea Bottom ◽  
Major Vessel ◽  
Gas Fields

The development of deep water gas fields using trunklines to carry the gas to the markets is sometime limited by the feasibility/economics of the construction phase. In particular there is a market for using S-lay vessels in water depth larger than 1000m. The S-lay feasibility depends on the applicable tension at the tensioner which is a function of water depth, stinger length and stinger curvature (for given stinger length by its curvature). This means that, without major vessel up-grading and to avoid too long stingers that are prone to damages caused by environmental loads, the application of larger stinger curvatures than presently allowed by current regulations/state of the art is needed. The work presented in this paper is a result of the project “Development of a Design Guideline for Submarine Pipeline Installation” sponsored by STATOIL and HYDRO. The technical activities are performed in co-operation by DNV, STATOIL and SNAMPROGETTI. The scope of the project is to produce a LRFD (Load Resistant Factor Design) design guideline to be used in the definition and application of design criteria for the laying phase e.g. to S and J-lay methods/equipment. The guideline covers D/t from 15 to 45 and applied strains over the overbend in excess of 0.5%. This paper addresses the failure modes relevant for combined high curvatures/strains, axial, external pressure and local forces due to roller over the stinger of an S-lay vessel and to sea bottom contacts, particularly: • Residual pipe ovality after laying, • Maximum strain and bending moment capacity. Analytical equations are proposed in accordance with DNV OS F101 philosophy and design format.

Bending and Twisting of Pipes With Strain Hardening

1984 ◽  
Vol 106 (2) ◽  
pp. 188-195 ◽  
Author(s):  
J. H. Lau ◽  
T. T. Lau
Keyword(s):  
Effective Strain ◽  
Closed Form Solution ◽  
Bending Moment ◽  
Small Deformation ◽  
Form Solution ◽  
Simultaneous Action ◽  
Deformation Analysis ◽  
Engineering Practice ◽  
Strain Diagram ◽  
Interaction Curves

A closed-form solution is presented for the small deformation analysis of a straight thin-walled circular cylinder subjected to the simultaneous action of bending and twisting moments. Dimensionless interaction curves and charts which relate the variables, bending moment, curvature, maximum effective strain, twisting moment, and shear strain are also provided for engineering practice convenience. The average stress-strain diagram of the cylinder is described by two straight lines. The result presented herein is not only a good approximation of a wide class of piping materials, but also provides a standard tool for estimating the accuracy of different direct schemes such as numerical integration, finite-difference, and finite-element methods.

Strength Performance of Steel Catenary Riser Using Short Term and Long Term Analysis Methodologies

2016 ◽  
Author(s):  
Feng Wang ◽  
Roger Burke ◽  
Anil Sablok ◽  
Kristoffer H. Aronsen ◽  
Oddgeir Dalane
Keyword(s):  
Bending Moment ◽  
Current Profile ◽  
Short Term ◽  
Sea State ◽  
Strength Performance ◽  
Steel Catenary Riser ◽  
Analysis Methodology ◽  
Riser Design ◽  
Term Analysis

Strength performance of a steel catenary riser tied back to a Spar is presented based on long term and short term analysis methodologies. The focus of the study is on response in the riser touch down zone, which is found to be the critical region based on short term analysis results. Short term riser response in design storms is computed based on multiple realizations of computed vessel motions with various return periods. Long term riser response is based on vessel motions for a set of 45,000 sea states, each lasting three hours. The metocean criteria for each sea state is computed based on fifty six years of hindcast wind and wave data. A randomly selected current profile is used in the long term riser analysis for each sea state. Weibull fitting is used to compute the extreme riser response from the response of the 45,000 sea states. Long term analysis results in the touch down zone, including maximum bending moment, minimum effective tension, and maximum utilization using DNV-OS-F201, are compared against those from the short term analysis. The comparison indicates that the short term analysis methodology normally followed in riser design is conservative compared to the more accurate, but computationally more expensive, long term analysis methods. The study also investigates the important role that current plays in the strength performance of the riser in the touch down zone.

Feasibility of Using Stress Joint in an Existing Flexible Joint Receptacle for a Deepwater SCR

2009 ◽  
Author(s):  
Basim Mekha ◽  
Alok Kumar ◽  
Mike Stark ◽  
Paul Barnett
Keyword(s):  
Bending Moment ◽  
Flexible Joints ◽  
Floating Structure ◽  
Element Analysis ◽  
Flexible Joint ◽  
Floating Structures ◽  
Operational Problem ◽  
Hull Structure ◽  
Hull Design ◽  
Titanium Material

In recent years, most fluid produced or exported has been transported using steel catenary risers (SCRs) attached to deepwater floating structures. The SCRs are terminated at the floating structures using Top Termination Units (TTUs) such as flexible joints or tapered stress joints. The flexible joints are usually designed to allow the riser to rotate with the floating structure motion and reduce the amount of moments transferred to the hull structure. The flexible joints depend on the flexibility and compressibility of the elastomer layers to allow for the rotation of the SCR. The stress joints, alternatively, provide fixed support at the hull and thus larger bending moment that has to be accounted for in the hull design. The stress joints can be made of steel or titanium material. The SCR TTU’s receptacle, which will be welded to the hull porch and contains the TTU basket, has to be designed to meet the force and reaction requirements associated with the selected TTU type. However, in some cases which could be due to failure of the TTU to meet the expected life or the operational requirements, the operators may have to replace the damaged TTU with another one or with a different TTU type. A few examples are available in the Gulf of Mexico. Recently the Flexible Joint TTU of the Independent Hub 20-inch export SCR had an operational problem. During the course of investigating the related issues and studying possible solutions, one option considered was the feasibility of replacing the Flexible Joint (FJ) with Titanium Tapered Stress Joint (TSJ). This paper highlights the issues that have to be considered in the design of the FJ existing receptacle to accommodate the force reactions of a Titanium TSJ. These issues are addressed and the results of the detailed finite element analysis performed are provided. The analysis conclusions, which are related to the feasibility of the existing receptacle to receive the loads imposed by TSJ and the modifications required to achieve this, are presented.

Numerical Investigation of Vertical Penetration of Steel Catenary Riser Near the Touch Down Zone

2016 ◽  
Author(s):  
Sujan Dutta ◽  
Bipul Hawlader ◽  
Ryan Phillips ◽  
Mike Paulin
Keyword(s):  
Soft Clay ◽  
Sea Waves ◽  
Factors Affecting ◽  
Steel Catenary Riser ◽  
Rate Dependent ◽  
Physical Experiments ◽  
Ansys Cfx ◽  
Waves And Currents ◽  
Steel Catenary Risers ◽  
Uplift Resistance

Steel catenary risers (SCR) are widely used in offshore to transport hydrocarbon from the seabed to floating or fixed platforms. The fatigue life of SCR near the touchdown zone (TDZ) is one of the main design concerns because the risers are often subjected to cyclic loading (vertical penetration/uplift, lateral and axial displacements) from various sources of environmental loadings, such as sea waves and currents. Numerical modeling of the penetration and uplift behaviour of an SCR is a challenging task. Most of the models available in the literature for uplift resistance are empirical, which have been developed mainly from the results of physical experiments. In this study, numerical simulation of vertical resistance is presented. Analysis is performed using ANSYS CFX software. Strain-softening and strain-rate dependent undrained shear strength behavior of soft clay sediment has been reported by many researchers. Unfortunately, these models were not available in CFX. Numerical simulations presented in this paper are performed implementing this behavior in CFX. Numerical results are compared with available empirical models. The present CFX modeling explains some mechanisms involved in trench formation and suction development during uplift. Factors affecting uplift resistance such as the size and shape of the trench are also discussed from a parametric study.

Model Test of a Steel Catenary Riser in a Towing Tank

2009 ◽  
Author(s):  
Celso K. Morooka ◽  
Raphael I. Tsukada ◽  
Sergio da Silva ◽  
Ricardo Franciss ◽  
Cyntia G. C. Matt
Keyword(s):  
Model Test ◽  
Forced Oscillation ◽  
Cross Flow ◽  
Towing Tank ◽  
Steel Catenary Riser ◽  
Flow Response ◽  
Numerical Predictions ◽  
Steel Catenary Risers ◽  
Numerical Tools ◽  
Scr Model

The objective of the present work is the study of the dynamic behavior of steel catenary risers (SCRs), focusing on the contribution of vortex-induced vibration (VIV), through model test in a towing tank. Nowadays, a great deal of effort is being spent in order to better understand VIV’s contribution in the dynamics of riser structures through experiments, analytical analysis and numerical predictions. In the present work, the design of a SCR model test, along with its setup in a towing tank, will be described in detail and discussions of main results from the experiments will be presented. The experiment has been conducted under several simulated environmental condition combinations, varying the towing speed, riser top forced oscillation amplitudes, waves amplitudes and periods. Very promising results have been observed from the experiment. Riser oscillations due to high harmonics of vortex shedding were observed. Analysis of the experimental results, coupled with the support of numerical tools, showed the influence of the phenomena of traveling waves in the cross-flow response as is reported from the literature.

Reliability Estimation of Solder Joint by Using the Failure Probability Models

2006 ◽  
Vol 326-328 ◽  
pp. 621-624 ◽  
Author(s):  
Ouk Sub Lee ◽  
Man Jae Hur ◽  
Jai Sug Hawong ◽  
No Hoon Myoung ◽  
Dong Hyeok Kim
Keyword(s):  
Solder Joint ◽  
Boundary Conditions ◽  
Failure Probability ◽  
Coefficient Of Thermal Expansion ◽  
Bending Moment ◽  
Fatigue Loading ◽  
Reliability Estimation ◽  
Probability Models ◽  
Reliability Method ◽  
The Difference

The differences in the coefficient of thermal expansion (CTE) between the chip and the FR-4 board generate the shear strains and the bending moment in the solder joint. It seems to be a main cause of failure in the solder joint when the chip and the FR-4 board are heated repeatedly. Thus, the fatigue loading induced by thermal cycling is a major concern in the reliability of the solder joint. The magnitude of shear strain and the final failure are known to be influenced by varying boundary conditions such as the difference of CTE, the height of solder, the distance of the solder joint from the neutral point (DNP) and the temperature variation. In this paper, the effects of boundary conditions on the failure probability of the solder joint are studied by using the failure probability models such as the First Order Reliability Method (FORM) and the Monte Carlo Simulation (MCS). Furthermore, the stiffness of the solder joint is considered to investigate the influence at the failure probability.

Strength and Deformation Capacity of Corroded Pipes: The Joint Industry Project

2013 ◽  
Author(s):  
Erik Levold ◽  
Andrea Restelli ◽  
Lorenzo Marchionni ◽  
Caterina Molinari ◽  
Luigino Vitali
Keyword(s):  
Failure Modes ◽  
State Of The Art ◽  
Local Buckling ◽  
Bending Moment ◽  
External Pressure ◽  
Fe Model ◽  
Deformation Capacity ◽  
Offshore Pipelines ◽  
Strength And Deformation ◽  
Bending Loading

Considering the future development for offshore pipelines, moving towards difficult operating condition and deep/ultra-deep water applications, there is the need to understand the failure mechanisms and better quantify the strength and deformation capacity of corroded pipelines considering the relevant failure modes (collapse, local buckling under internal and external pressure, fracture / plastic collapse etc.). A Joint Industry Project sponsored by ENI E&P and Statoil has been launched with the objective to quantify and assess the strength and deformation capacity of corroded pipes in presence of internal overpressure and axial/bending loading. In this paper: • The State-of-the-Art on strength and deformation capacity of corroded pipes is presented; • The full-scale laboratory tests on corroded pipes under bending moment dominated load conditions, performed at C-FER facilities, are shown together with the calibrated ABAQUS FE Model; • The results of the ABAQUS FEM parametric study are presented.

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