A New User Defined Element for Nonlinear Riser-Soil Interaction Analysis of Steel Catenary Riser Systems

2016 ◽  
Author(s):  
Jiayue Liu ◽  
Mehrdad Kimiaei ◽  
Mark Randolph
Keyword(s):  
Interaction Analysis ◽  
Global Analysis ◽  
Cost Effective ◽  
Steel Catenary Riser ◽  
Analysis And Design ◽  
Static And Dynamic Analysis ◽  
Finite Element Software ◽  
Nonlinear Springs ◽  
Fatigue Design ◽  
Software Packages

Steel Catenary Risers (SCRs) provide a technically feasible and commercially efficient solution for the offshore field developments in deep waters. Fatigue design of SCRs in the touchdown zone (TDZ) is among the most complicated engineering challenges in riser design. The cyclic interaction of the riser with seabed leads to a number of complex nonlinear behaviors including soil suction, separation of the riser from the soil, trench formation and degradation of soil resistance during cyclic loading. Accurate simulation of the riser-soil interaction has significant effects on the fatigue performance in the TDZ. Few hysteretic nonlinear riser-soil interaction models have recently been introduced and some of them have been implemented in commercial software packages for analysis and design of riser systems. Due to complexity of the models and also limited access to special software packages with in-built nonlinear soil models, traditional simple linear soil models are still being used widely for riser analysis, in particular for fatigue design. In this paper, one of the existing nonlinear hysteretic seabed model, already been used in a commercial analysis program OrcaFlex [1], has been implemented into general finite element software Abaqus [2], through the coding of a user defined element (UEL) subroutine. The paper documents the implementation of UEL into Abaqus and the establishment of global riser model for both static and dynamic analysis on which the pipe is modelled efficiently as series of unidirectional beam elements from floater to seabed, resting on a bed of nonlinear springs. Longitudinal friction between pipe and seabed has also been considered. A series of simulations are performed to illustrate the capabilities of the model. All these results have good agreement with those from OrcaFlex. Results indicate that the proposed UEL is capable of modelling nonlinear riser-soil interaction phenomena and has been verified to be a cost-effective alternative to OrcaFlex in terms of global analysis of SCRs. In addition, as an open source code, UEL provides the required tool for future development on nonlinear soil models. A new type of nonlinear soil with bilinear soil shear strength is modeled and its effect on structural performances of SCRs is investigated.

Modelling of Flexible Victaulic Couplings Using Basic Finite Element Software

2008 ◽  
Author(s):  
Roman W. Motriuk
Keyword(s):  
Finite Element ◽  
Bending Moment ◽  
Cost Effective ◽  
Transportation Systems ◽  
Finite Element Software ◽  
Software Packages ◽  
Linear Elements ◽  
Stress Models ◽  
Simple Stress ◽  
Made In

In the past decade, Victaulic couplings have gained significant recognition as important piping elements, which are used mainly in water and slurry transportation systems. For example, grooved flexible Victaulic couplings offered significant economical and reliable piping connections when compared to other connecting elements such as flanges. Victaulic couplings are on average three times faster to install than welding piping connections. They are more reliable and cost-effective than flanges or threaded connectors. In addition, the speed and easiness of their assembly or disassembly as well as their flexibility and ability to provide thermal gaps make the couplings desirable as piping elements. Furthermore, the couplings provide stress designers with a rare opportunity to cheaply and reliably compensate for piping loads which are otherwise exerted on equipment attached to piping. For the above reasons Victaulic couplings are frequently used in current piping designs. In spite of their simple design and application they pose a significant challenge for stress designers. The stress software packages based on piping finite element theories which are commonly used in industry do not provide the means to model Victaulic couplings adequately. These packages are based on stress linear theories, and Victaulic couplings with their gaps are definitely non-linear elements. Therefore, the approach to model these elements is very approximate and is usually done by the use of nonlinear restraints built into the software. The stiffness and friction for Victaulic coupling “restraints” are rarely known and assumptions of their values have to be made in order to carry out calculations. Therefore, the prescribed values for the restraints directly influence the stress results. This work discusses assumptions based on several simple stress models. An attempt is made by the author to minimize conservatism as much as practical in the modelling of Victaulic couplings, while waiting for the manufacturers of these elements to test their products and provide meaningful statistical information, which could then be used to carry out stress predictions. The couplings’ stiffness, bending moment and axial force capabilities provided in this work must not be used for design purposes unless verified and accepted by the couplings’ manufacturers.

Effect of Polyester Mooring Stiffness on SCR Design for FPSO Application

2012 ◽  
Author(s):  
Gwo-Ang Chang ◽  
Pao-Lin Tan ◽  
Ken Huang ◽  
Tom Kwan
Keyword(s):  
Global Analysis ◽  
Dynamic Stiffness ◽  
Cost Effective ◽  
Systematic Investigation ◽  
Steel Catenary Riser ◽  
Motion Responses ◽  
Stiffness Model ◽  
Riser Design ◽  
The Impact ◽  
Selection Of

Polyester rope is a visco-elastic material and its stiffness is affected by mean tension, tension amplitude, loading period, and loading history. Qualitatively it may be felt that rope stiffness significantly affects vessel offset, which in turn affects riser performance and cost. However, a systematic investigation of the impact of rope stiffness on riser stress and fatigue life has not been published for a wide variety of design conditions. This paper describes such a study, and provides specific guidance to designers for the prudent selection of a rope stiffness model and values to achieve safe and cost effective riser design. This study investigated the effect of polyester rope stiffness on steel catenary riser (SCR) design for an FPSO sited in a variety of water depths considering environmental conditions representative of West Africa. Static/dynamic stiffness models for polyester rope in the recently issued ABS Guidance Notes on the Application of Fiber Rope for Offshore Mooring [1] were used in a global analysis to provide motion responses for the riser analysis. Time domain riser analysis was performed to obtain maximum riser stress and fatigue damage under various conditions. Based on the results of the investigation of riser and mooring analysis, guidance on the impact of rope stiffness to the riser design has been developed.

Fatigue Damage Study of Helical Wires in Catenary Unbonded Flexible Riser Near Touchdown Point

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Kunpeng Wang ◽  
Chunyan Ji ◽  
Hongxiang Xue ◽  
Wenyong Tang
Keyword(s):  
Analytical Model ◽  
Fatigue Damage ◽  
Global Analysis ◽  
Axial Stress ◽  
Flexible Riser ◽  
Steel Catenary Riser ◽  
Finite Element Software ◽  
Seabed Stiffness ◽  
Touchdown Point ◽  
Unbonded Flexible Riser

This study presents an analytical model of flexible riser and implements it into finite-element software abaqus to investigate the fatigue damage of helical wires near touchdown point (TDP). In the analytical model, the interlayer contact pressure is simulated by setting up springs between adjacent interlayers. The spring stiffness is iteratively updated based on the interlayer penetration and separation conditions in the axisymmetric analysis. During the bending behavior, the axial stress of helical wire along the circumferential direction is traced to determine whether the axial force overcomes the interlayer friction force and thus lead to sliding. Based on the experimental data in the literature, the model is verified. The present study implements this model into abaqus to carry out the global analysis of the catenary flexible riser. In the global analysis, the riser–seabed interaction is simulated by using a hysteretic seabed model in the literature. The effect of the seabed stiffness and interlayer friction on the fatigue damage of helical wire near touchdown point is parametrically studied, and the results indicate that these two aspects significantly affect the helical wire fatigue damage, and the sliding of helical wires should be taken into account in the global analysis for accurate prediction of fatigue damage. Meanwhile, different from the steel catenary riser, high seabed stiffness may not correspond to high fatigue damage of helical wires.

On the Design and Analysis of Acoustic Horns for Ultrasonic Welding Teflon Encapsulated O-Ring

2013 ◽  
Vol 753-755 ◽  
pp. 402-406
Author(s):  
Kuen Ming Shu ◽  
Yu Jen Wang ◽  
Hoa Shen Yen
Keyword(s):  
Finite Element ◽  
Natural Frequencies ◽  
High Energy ◽  
Ultrasonic Welding ◽  
Ultrasonic Machining ◽  
Analysis And Design ◽  
Vital Part ◽  
Finite Element Software ◽  
Acoustic Horns

The acoustic horn plays a very vital part in high energy ultrasonic machining, and its design is critical to the quality and the efficiency of ultrasonic machining. This paper performs the analysis and design of acoustic horns for ultrasonic welding Teflon encapsulated O-ring by employing ANSYS finite element software. Firstly, the theoretical dimensions of the horns are calculated. Moreover, their natural frequencies and amplitudes are obtained through the simulations of ANSYS.

ECA Methodology for Fatigue Design of Risers and Flowlines

2007 ◽  
Author(s):  
C. H. Luk ◽  
T. J. Wang
Keyword(s):  
Fracture Mechanics ◽  
Design Method ◽  
Steel Catenary Riser ◽  
Fatigue Design ◽  
Wide Range ◽  
Fatigue And Fracture ◽  
Level 3 ◽  
Fatigue Loads ◽  
Vessel Motion ◽  
Level 2

Engineering Criticality Assessment (ECA) is a procedure based on fracture mechanics that may be used to supplement the traditional S-N approach and determine the flaw acceptance and inspection criteria in fatigue and fracture design of risers and flowlines. A number of design codes provide guidance for this procedure, e.g. BS-7910:2005 [1]. However, more investigations and example studies are still needed to address the design implications for riser and flowline applications. This paper provides a review of the existing ECA methodology, presents a fracture mechanics design method for a wide range of riser and flowline fatigue problems, and shows flaw size results from steel catenary riser (SCR) and flowline (FL) examples. The first example is a deepwater SCR subjected to fatigue loads due to vessel motion and riser VIV. The second example is a subsea flowline subjected to thermal fatigue loads. The effects of crack re-characterization and material plasticity on the Level-2 and Level-3 ECA results of the SCR and flowline examples are illustrated.

Creative Design-by-Analysis Solutions Applied to High-Temperature Components

1993 ◽  
Vol 115 (3) ◽  
pp. 221-227
Author(s):  
A. K. Dhalla
Keyword(s):  
Finite Element ◽  
High Temperature ◽  
Detailed Analysis ◽  
Structural Response ◽  
Cost Effective ◽  
Element Analysis ◽  
Finite Element Software ◽  
Division 1 ◽  
High Temperature Components ◽  
Elevated Temperature Design

Elevated temperature design has evolved over the last two decades from design-by-formula philosophy of the ASME Boiler and Pressure Vessel Code, Sections I and VIII (Division 1), to the design-by-analysis philosophy of Section III, Code Case N-47. The benefits of design-by-analysis procedures, which were developed under a US-DOE-sponsored high-temperature structural design (HTSD) program, are illustrated in the paper through five design examples taken from two U.S. liquid metal reactor (LMR) plants. Emphasis in the paper is placed upon the use of a detailed, nonlinear finite element analysis method to understand the structural response and to suggest design optimization so as to comply with Code Case N-47 criteria. A detailed analysis is cost-effective, if selectively used, to qualify an LMR component for service when long-lead-time structural forgings, procured based upon simplified preliminary analysis, do not meet the design criteria, or the operational loads are increased after the components have been fabricated. In the future, the overall costs of a detailed analysis will be reduced even further with the availability of finite element software used on workstations or PCs.

Static and Dynamic Analysis of Aluminium Composite in Wing Section Using ANSYS

2014 ◽  
Vol 984-985 ◽  
pp. 367-371
Author(s):  
E.S. Esakkiraj ◽  
S. Anish ◽  
V. Anish
Keyword(s):  
Static Analysis ◽  
Minimum Weight ◽  
Equivalent Stress ◽  
Model Analysis ◽  
Aluminium Composite ◽  
Aircraft Wing ◽  
Lower Stress ◽  
Static And Dynamic Analysis ◽  
Finite Element Software ◽  
Composite Wing

The cold of this cardboard is to abstraction and analyze the amount accustomed accommodation and weight accumulation of blended aircraft (Aluminium Silicon Carbide) addition with that of Aluminium wing and appropriately access the acceptable aircraft addition of minimum weight accomplished of address a accustomed changeless amount after failure. And also this paper presents a model and a static analysis of the aircraft wing, using the finite element software ANSYS. The geometry was created in CATIA V5 R18 and imported. The static and model analysis are carried out in analysis software ANSYS. The result of from the static analysis refers to the total deformation, equivalent stress, shear stress and shear intensity on the skin of the aircraft wing. The model analysis will be carried out to find out the first six modes of vibrations and the different mode shape in which wing can deform without the application of load. Compared to the conventional Aluminium wing, the hybridized composite wing experience far lower stresses and the aircraft wing weight nearly 40% and 50% lower stress.

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.

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.

Development of Assessment Criteria for Various Open Sources GIS Software Packages

2021 ◽  
pp. 398-412
Author(s):  
Shahriar Shams
Keyword(s):  
Open Source ◽  
Open Source Software ◽  
Assessment Criteria ◽  
Significant Development ◽  
Analysis And Design ◽  
Advantages And Disadvantages ◽  
Software Packages ◽  
Open Source Gis ◽  
Gis Software

There has been a significant development in the area of free and open source geospatial software. Research has flourished over the decades from vendor-dependent software to open source software where researchers are paying increasing attention to maximize the value of their data. It is often a difficult task to choose particular open source GIS (OGIS) software among a number of emerging OGIS software. It is important to characterise the projects according to some unified criteria. Each software has certain advantages and disadvantages and it is always time consuming to identify exactly which software to select for a specific purpose. This chapter focuses on the assessment criteria enabling developers, researchers, and GIS users to select suitable OGIS software to meet their requirements for analysis and design of geospatial application in multidisciplinary fields. This chapter highlights the importance of assessment criteria, followed by an explanation of each criteria and their significance with examples from existing OGIS software.

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