Effect of Flexible Joint Modelling Method on Deep Water Catenary Riser Hang-Off Fatigue Response

2019 ◽  
Author(s):  
Guanyu Hu ◽  
Chaojun Huang ◽  
Fengjie Yin ◽  
Mark Cerkovnik ◽  
Guangqiang Yang
Keyword(s):  
Deep Water ◽  
Joint Stiffness ◽  
Fatigue Performance ◽  
Fatigue Load ◽  
Flexible Joint ◽  
Cyclic Bending ◽  
Modelling Method ◽  
The Impact ◽  
Nonlinear Curve ◽  
Modelling Methods

Abstract The Flexible joint is one of the most widely used hang-off systems for deep water catenary riser for its large rotation and load bearing capacity. The fatigue performance of riser hang-off region and fatigue load on the flexible joint highly depend on the rotational stiffness of the flexible joint. Thus, modelling the flexible joint stiffness to accurately simulate the behavior under cyclic bending cycles is critical in global riser fatigue analysis. The load-displacement relationship of a flexible joint typically follows a nonlinear curve, and it shows hysteresis behavior when subject to cyclic bending cycles. However, in current industry practice, the flexible joint stiffness is modelled either as a nonlinear curve or simplified as a fixed value. These simplified methods sometimes can lead to unconservative or over conservative results in riser design. Modelling the flexible joint stiffness in an accurate approach becomes more important especially when the riser fatigue is critical at the hang-off region. In addition, the design of flexible joint will also be impacted by the fatigue load extracted from global fatigue analysis, which is also largely affected by the flexible joint stiffness modelling method. Thus, modelling a flexible joint by accounting for the nonlinear hysteretic stiffness is recommended. This paper compares the different modelling methodologies of the flexible joint for catenary riser hang-off and presents the impact on fatigue performance considering hysteretic behavior. This study considers the effects of wave amplitude and hosting vessel offset. A case study is also presented on the application of all the modelling methods on fatigue performance of an SCR in the Gulf of Mexico. The fatigue behavior is compared for the different modelling methods considering long term wave motion and platform offsets. The impact on the results from different types of hosting platform is also discussed.

Flexible Joint Stiffness Modelling Improving Ultra Deep Water Rigid Risers Fatigue Damage

2019 ◽  
Author(s):  
Germain Venero ◽  
Victor Gomes ◽  
Hugues Corrignan ◽  
Daniel Carneiro
Keyword(s):  
Fatigue Damage ◽  
Deep Water ◽  
Joint Stiffness ◽  
Flexible Joint

Strength and Fatigue Performance of Steel Lazy Wave Risers With Change in Configuration Parameters

2019 ◽  
Author(s):  
Mayank Lal ◽  
Feng Wang ◽  
Xiaohua Lu ◽  
Abhilash Sebastian
Keyword(s):  
Deep Water ◽  
Parametric Study ◽  
Fatigue Performance ◽  
Design Criteria ◽  
Cost Assessment ◽  
Fatigue Design ◽  
Design Variables ◽  
Steel Catenary Risers ◽  
Normative Cost ◽  
The Impact

Abstract Steel Lazy wave risers are being increasingly used for deep water applications due to better strength and fatigue performance in the touchdown zone compared to steel catenary risers. Several parameters govern the design of steel lazy wave risers including the length of the catenary from hang-off to start of buoyancy section and the length of the buoyancy section. In this paper, a parametric study is performed to investigate the trends in strength and fatigue performance of steel lazy wave risers with change in configuration parameters. A normative cost assessment is also performed to show the impact of these design variables on overall cost of the system. Dynamic analysis is performed to check the change in strength and fatigue performance of steel lazy wave risers as the configuration parameters are changed. The results from the parametric study will assist in designing steel lazy wave risers which satisfy the strength and fatigue design criteria.

scholarly journals The impact of modelling method selection on predicted extent and distribution of deep-sea benthic assemblages

2014 ◽  
Vol 105 (4) ◽  
pp. 251-261 ◽  
Author(s):  
Nils Piechaud ◽  
Anna Downie ◽  
Heather A. Stewart ◽  
Kerry L. Howell
Keyword(s):  
Deep Sea ◽  
Performance Metrics ◽  
Predictive Modelling ◽  
Lophelia Pertusa ◽  
Benthic Assemblages ◽  
Modelling Method ◽  
Input Variables ◽  
The Impact ◽  
Modelling Methods ◽  
Political Decisions

ABSTRACTPredictive modelling of deep-sea species and assemblages with multibeam acoustic datasets as input variables is now a key tool in the provision of maps upon which spatial planning and management of the marine environment can be based. However, with a multitude of methods available, advice is needed on the best methods for the task at hand. In this study, we predictively modelled the distribution and extent of three vulnerable marine ecosystems (VMEs) at the assemblage level (‘Lophelia pertusa reef frameworks’; ‘Stylasterids and lobose sponges’; and ‘Xenophyophore fields’) on the eastern flank of Rockall Bank, using three modelling methods: MaxEnt; RandomForests classification with multiple assemblages (gRF); and RandomForests classification with the presence/absence of a single VME (saRF). Performance metrics indicated that MaxEnt performed the best, but all models were considered valid. All three methods broadly agreed with regard to broad patterns in distribution. However, predicted extent presented a variation of up to 35 % between the different methods, and clear differences in predicted distribution were observed. We conclude that the choice of method is likely to influence the results of predicted maps, potentially impacting political decisions about deep-sea VME conservation.

Dynamic Modeling and Analysis of Space Manipulator Considering the Flexible of Joint and Link

2013 ◽  
Vol 823 ◽  
pp. 270-275 ◽  
Author(s):  
Pan Dong ◽  
Zhao Yang ◽  
Zhang Yue ◽  
Wei Cheng ◽  
E Wei
Keyword(s):  
Joint Stiffness ◽  
Low Frequency ◽  
Flexible Link ◽  
Large Space ◽  
Flexible Joint ◽  
Modeling And Analysis ◽  
Position Accuracy ◽  
Low Frequency Vibration ◽  
Space Manipulators ◽  
The Impact

The long length, light weight, low frequency, flexible joint and link of large space manipulators impact dynamic stability and position accuracy seriously. In this paper, dynamical model of space flexible manipulators system is build base on Lagrange method. With three DOF manipulators as the research object, the impact of flexible link, joint stiffness and clearance on the system frequency and end position accuracy of manipulator is simulated and analyzed. The results indicate that the flexible joint lead to low frequency vibration and flexible link lead to high frequency vibration. Low frequency vibration is the dominant impact of end position accuracy, Flexible joint have greater impact on the dynamic characteristics of system than that of flexible link.

scholarly journals Fatigue Performance of SFPSC under Hot-Wet Environments and Cyclic Bending Loads

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Shanshan Luo ◽  
Peiyan Huang ◽  
Xinyan Guo ◽  
Xiaohong Zheng
Keyword(s):  
Steel Fiber ◽  
High Strength ◽  
Fatigue Performance ◽  
Cyclic Loads ◽  
Fatigue Load ◽  
Bending Fatigue ◽  
Cyclic Bending ◽  
Bridge Superstructures ◽  
Three Point Bending ◽  
Bending Loads

A new structural material named “steel fiber polymer structural concrete (SFPSC)” with features of both high strength and high toughness was developed by this research group and applied to the bridge superstructures in the hot-wet environments. In order to investigate the fatigue performance and durability of SFPSC under hot-wet environments, the environment and fatigue load uncoupling method and the coupling action of environment and fatigue load were used or developed. Three-point bending fatigue experiments with uncoupling action of environments and cyclic loads were carried out for SFPSC specimens which were pretreated under hot-wet environments, and the experiments with the coupling action of environments and cyclic loads for SFPSC specimens were carried out under hot-wet environments. Then, the effects of hot-wet environments and the experimental methods on the fatigue mechanism of SFPSC material were discussed, and the environmental fatigue equations of SFPSC material under coupling and uncoupling action of hot-wet environments and cyclic bending loads were established. The research results show that the fatigue limits of SFPSC under the coupling action of the environments and cyclic loads were lower about 15%. The proposed fatigue equations could be used to estimate the fatigue lives and fatigue limits of SFPSC material.

scholarly journals Time-to-event analysis in economic evaluations: a comparison of modelling methods to assess the cost-effectiveness of transplanting a marginal quality kidney

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sameera Senanayake ◽  
Nicholas Graves ◽  
Helen Healy ◽  
Keshwar Baboolal ◽  
Adrian Barnett ◽  
...  
Keyword(s):  
Cost Effectiveness ◽  
Time Horizon ◽  
Transition Probabilities ◽  
Discrete Event ◽  
Economic Evaluations ◽  
Event Analysis ◽  
Time To Event ◽  
Modelling Method ◽  
Cycle Lengths ◽  
Modelling Methods

Abstract Background Economic-evaluations using decision analytic models such as Markov-models (MM), and discrete-event-simulations (DES) are high value adds in allocating resources. The choice of modelling method is critical because an inappropriate model yields results that could lead to flawed decision making. The aim of this study was to compare cost-effectiveness when MM and DES were used to model results of transplanting a lower-quality kidney versus remaining waitlisted for a kidney. Methods Cost-effectiveness was assessed using MM and DES. We used parametric survival models to estimate the time-dependent transition probabilities of MM and distribution of time-to-event in DES. MMs were simulated in 12 and 6 monthly cycles, out to five and 20-year time horizon. Results DES model output had a close fit to the actual data. Irrespective of the modelling method, the cycle length of MM or the time horizon, transplanting a low-quality kidney as compared to remaining waitlisted was the dominant strategy. However, there were discrepancies in costs, effectiveness and net monetary benefit (NMB) among different modelling methods. The incremental NMB of the MM in the 6-months cycle lengths was a closer fit to the incremental NMB of the DES. The gap in the fit of the two cycle lengths to DES output reduced as the time horizon increased. Conclusion Different modelling methods were unlikely to influence the decision to accept a lower quality kidney transplant or remain waitlisted on dialysis. Both models produced similar results when time-dependant transition probabilities are used, most notable with shorter cycle lengths and longer time-horizons.

Ratcheting assessment of corroded elbow pipes subjected to internal pressure and cyclic bending moment

2021 ◽  
pp. 030932472198989
Author(s):  
Ali Salehi ◽  
Armin Rahmatfam ◽  
Mohammad Zehsaz
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Internal Pressure ◽  
Bending Moment ◽  
Axial Direction ◽  
Hoop Strain ◽  
Cyclic Bending ◽  
High Fatigue ◽  
The Impact ◽  
Cyclic Bending Moment

The present study aimed to study ratcheting strains of corroded stainless steel 304LN elbow pipes subjected to internal pressure and cyclic bending moment. To this aim, spherical and cubical shapes corrosion are applied at two depths of 1 mm and 2 mm in the critical points of elbow pipe such as symmetry sites at intrados, extrados, and crown positions. Then, a Duplex 2205 stainless steel elbow pipe is considered as an alternative to studying the impact of the pipe materials, due to its high corrosion resistance and strength, toughness, and most importantly, the high fatigue strength and other mechanical properties than stainless steel 304LN. In order to perform numerical analyzes, the hardening coefficients of the materials were calculated. The results highlight a significant relationship between the destructive effects of corrosion and the depth and shape of corrosion, so that as corrosion increases, the resulting destructive effects increases as well, also, the ratcheting strains in cubic corrosions have a higher growth rate than spherical corrosions. In addition, the growth rate of the ratcheting strains in the hoop direction is much higher across the studied sample than the axial direction. The highest growth rate of hoop strain was observed at crown and the highest growth rate of axial strains occurred at intrados position. Altogether, Duplex 2205 material has a better performance than SS 304LN.

Fatigue Performance of TBCs on Hastelloy X Substrate During Cyclic Bending

2015 ◽  
Vol 25 (1-2) ◽  
pp. 231-243 ◽  
Author(s):  
Radek Musalek ◽  
Ondrej Kovarik ◽  
Libor Tomek ◽  
Jan Medricky ◽  
Zdenek Pala ◽  
...  
Keyword(s):  
Fatigue Performance ◽  
Hastelloy X ◽  
Cyclic Bending

scholarly journals Architectural Diversity of Submarine Lobate Deposits

2021 ◽  
Vol 9 ◽  
Author(s):  
Tim R. McHargue ◽  
David M. Hodgson ◽  
Eitan Shelef
Keyword(s):  
Turbulent Flows ◽  
Deep Water ◽  
Relative Size ◽  
Transport Pathway ◽  
Branching Points ◽  
Channel Patterns ◽  
The Impact ◽  
Source Materials ◽  
Permeability Structure ◽  
Distributary Channel

Lobate deposits in deep-water settings are diverse in their depositional architecture but this diversity is under-represented in the literature. Diverse architectures result from multiple factors including source material, basin margin physiography, transport pathway, and depositional setting. In this contribution, we emphasize the impact of differing source materials related to differing delivery mechanisms and their influence on architecture, which is an important consideration in source-to-sink studies. Three well imaged subsurface lobate deposits are described that display three markedly different morphologies. All three lobate examples, two from intraslope settings offshore Nigeria and one from a basin-floor setting offshore Indonesia, are buried by less than 150 m of muddy sediment and are imaged with high resolution 3D reflection seismic data of similar quality and resolution. Distinctively different distributary channel patterns are present in two of the examples, and no comparable distributaries are imaged in a third example. Distributary channels are emphasized because they are objectively recognized and because they often represent elements of elevated fluid content within buried lobate deposits and thus influence permeability structure. We speculate that the different distributary channel patterns documented here resulted from different processes linked to source materials: 1) a lobate deposit that is pervasively channelized by many distributaries that have branched at numerous points is interpreted to result from comparatively mud-rich, stratified, turbulent flows; 2) an absence of distributaries in a lobate deposit is interpreted to result from collapse of mud-poor, turbulent flows remobilized from littoral drift; and 3) a lobate deposit with only a few, long, straight distributaries with few branching points is interpreted to be dominated by highly viscous flows (i.e., debris flows). We propose a conceptual model that illustrates the relationship between the proportion of mud in contributing flows and the relative size and runout distance of lobate deposits. We conclude that reconciling 3D seismic morphologies with outcrop observations of channels, scours, and amalgamation zones, and simple application of hierarchical schemes, is problematic. Furthermore, when characterizing unconfined deep-water deposits in the subsurface, multiple models with significant differences in predicted permeability structure should be considered.

scholarly journals Which data for quantitative landslide susceptibility mapping at operational scale? Case study of the Pays d'Auge plateau hillslopes (Normandy, France)

2013 ◽  
Vol 1 (2) ◽  
pp. 957-1000 ◽  
Author(s):  
M. Fressard ◽  
Y. Thiery ◽  
O. Maquaire
Keyword(s):  
Landslide Susceptibility ◽  
Roc Curves ◽  
Statistical Modelling ◽  
Susceptibility Mapping ◽  
Landslide Susceptibility Mapping ◽  
Statistical Accuracy ◽  
Multivariate Statistical ◽  
The Impact ◽  
Modelling Methods

Abstract. The objective of this paper is to assess the impact of the datasets quality for the landslide susceptibility mapping using multivariate statistical modelling methods at detailed scale. This research is conducted in the Pays d'Auge plateau (Normandy, France) with a scale objective of 1/10000, in order to fit the French guidelines on risk assessment. Five sets of data of increasing quality (considering accuracy, scale fitting, geomophological significance) and cost of acquisition are used to map the landslide susceptibility using logistic regression. The best maps obtained with each set of data are compared on the basis of different statistical accuracy indicators (ROC curves and relative error calculation), linear cross correlation and expert opinion. The results highlights that only high quality sets of data supplied with detailed geomorphological variables (i.e. field inventory and surficial formations maps) can predict a satisfying proportion of landslides on the study area.

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