Effects of different loading time histories on fatigue design of steel catenary risers using nonlinear riser-soil interaction models

2015 ◽  
pp. 399-404 ◽  
Author(s):  
M Kimiaei ◽  
J Liao
Keyword(s):  
Interaction Models ◽  
Fatigue Design ◽  
Time Histories ◽  
Steel Catenary Risers

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.

Impact of Soil Modeling on Fatigue Design of Lazy Wave Riser Systems

2019 ◽  
Author(s):  
Rupak Ghosh ◽  
Haydar Arslan
Keyword(s):  
Fatigue Life ◽  
Water Injection ◽  
Field Testing ◽  
Vertical Displacement ◽  
Soil Response ◽  
Fatigue Design ◽  
Steel Catenary Risers ◽  
Design Requirements ◽  
Seabed Stiffness

Abstract The Liza risers comprise production risers, water injection risers and gas injection risers, and a lazy wave configuration is selected considering FPSO motion, reservoir fluid and overall project execution requirements. During operation, the risers are expected to move cyclically with small vertical displacement amplitudes (e.g. 0.1% to 1% of the riser diameter), and a key design issue is the fatigue life of these risers at critical locations including the touch-down zone which will be governed by the seabed stiffness. The role of soil response on fatigue life of riser with buoyancy has been investigated through nonlinear finite element and comprehensive lab and field testing program. Published methodologies for determining seabed stiffness values for risers concentrate more on larger amplitude motions based on the design requirements of steel catenary risers. The paper presents the sensitivity of the fatigue life at TDP to various soil model and provides insight in the results. Also included is the importance of site specific soil investigation in the context of design of riser.

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.

Fatigue Design of the Atlantis Export SCRS

2007 ◽  
Author(s):  
Mike Vandenbossche ◽  
Will McDonald ◽  
Dingwu Xia ◽  
Craig Masson ◽  
Jie Fang ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
Wave Climate ◽  
Fatigue Performance ◽  
Mardi Gras ◽  
Fatigue Design ◽  
Fatigue Damage Accumulation ◽  
Steel Catenary Risers ◽  
Sigsbee Escarpment ◽  
Girth Welds ◽  
First Time

The Atlantis semi-submersible platform is located in 7040 feet water depth in southern Green Canyon, in the Gulf of Mexico. It supports the Mardi Gras 24-inch oil and 16-inch gas export steel catenary risers (SCRs), the deepest and largest diameter SCRs in the world. Fatigue performance was one of the critical and challenging aspects of the design due to the severe wave climate coupled with the large vessel motions and strong bottom currents below the Sigsbee Escarpment. Preliminary design showed that the fatigue life at the girth welds in the touch down point (TDP) region did not satisfy the design criteria. This paper presents the fatigue design measures that were adopted to improve the fatigue performance of the Atlantis export SCRs. These include the first-time use of manually relocating the host platform to reduce fatigue damage accumulation in the TDP region, and removing the weld caps over the most critical part of the TDP region and grind flush the caps and roots of the welds in the flexible joint assembly to achieve practical defect acceptance criteria. It is demonstrated that the narrow fatigue damage peak in the TDP region can be decreased significantly by spreading it over a wider region, and all the design requirements are satisfied.

Fatigue Mitigation Design of Deepwater Steel Catenary Risers

2006 ◽  
Author(s):  
Xiongliang Yao ◽  
Liping Sun
Keyword(s):  
Vertical Motion ◽  
Design Criterion ◽  
Steel Catenary Riser ◽  
Fatigue Design ◽  
Induced Motion ◽  
Steel Catenary Risers ◽  
Fatigue Mitigation ◽  
Mitigation Design ◽  
Stress Concentration Factors ◽  
Mitigation Methods

With the development of deepwater offshore industries, Steel Catenary Riser (SCR) concept offers great advantages over others and has been widely deployed worldwide. More than 100 SCRs have been installed in the deepwater fields including West of Africa, Gulf of Mexico, and Offshore Brazil. Fatigue is still the number one governing design criterion of the deepwater SCR regardless the floater types (SPAR, TLP, SEMI, and FPSO). Typical SCR fatigue damages include vortex induced vibration (VIV), host floater motion induced, floater vortex induced motion (VIM) fatigue, floater vertical motion induced VIV, installation, and other kinds of dynamic loading imposed to SCR. The success of the SCR design depends primarily upon the fatigue design and its mitigation methods. This paper summaries the viable fatigue mitigation design for deepwater SCR. Detailed discussion is given to different kind of fatigue damages of SCR. Focus of fatigue design of each type of deepwater floater is pointed out. Detailed discussion is given to the selection of design methods, SN curves, stress concentration factors, influence of sweet and sour service, and post-processing of fatigue sensitive welds. Different potential and practical fatigue design mitigations have been evaluated and discussion. The most viable options have been pointed out. Some examples based on actual projects experience are given to demonstrate the design principles and fatigue mitigation methods.

Weight Optimized SCR: Enabling Technology for Turret Moored FPSO Developments

2007 ◽  
Author(s):  
Elizabeth Foyt ◽  
Cary Griffin ◽  
Mike Campbell ◽  
H. Howard Wang ◽  
Wan C. Kan
Keyword(s):  
Design Criteria ◽  
Critical Area ◽  
Enabling Technology ◽  
Optimum Configuration ◽  
Fatigue Design ◽  
Optimization Study ◽  
Coating Type ◽  
Steel Catenary Risers ◽  
Design Challenges

Steel catenary risers (SCRs) used in conjunction with a turret moored FPSO in deepwater environments present significant design challenges. The large vertical motions at the FPSO turret induce severe riser response. This results in difficulty meeting strength and fatigue design criteria at the Touch Down Point (TDP) and at the riser hang off location. It is typically considered challenging to achieve feasibility for a conventional SCR application on a turret moored FPSO. Previous industry work for an SCR application used with other floating hosts has demonstrated that SCR strength and fatigue response can be improved using heavy and light coatings strategically placed along the riser [1]. An optimization study is performed, based on previous industry work, which demonstrates that a weight optimized configuration can enable the application of an SCR on a turret moored FPSO. The effect of adding different coatings along the length of the SCR is discussed. The position, length, and density of the coating type are varied to determine an optimum configuration for both strength and fatigue response. This paper will also discuss observations which may help explain why weighted sections can improve SCR response at the critical area.

Strength Evaluation and Fatigue Prediction of a Spur Gear Pair by Computer Simulation

2006 ◽  
Author(s):  
Zhong Hu ◽  
Fereidoon Delfanian
Keyword(s):  
Computer Simulation ◽  
Mechanical Design ◽  
Gear Tooth ◽  
Three Dimensional ◽  
Spur Gear ◽  
Operating Conditions ◽  
Gear Pair ◽  
Working Cycle ◽  
Fatigue Design ◽  
Time Histories

Fatigue prediction of a three-dimensional mechanical component under dynamic load is critical for mechanical design. In this paper, computer simulation of three-dimensional dynamic stress followed by fatigue calculation was performed on a spur-gear pair using finite element modeling. Starting from gear pair geometry and operating conditions, the time histories of the dynamic loads and multi-axial stresses for a complete working cycle of a gear tooth were computed, and then post processed to produce fatigue strength information. Along with certain material properties obtained from experiments, this computer simulated fatigue design provides a useful tool for predicting fatigue failure of mechanical components.

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