A Consistent Analytical Model to Predict the Structural Behavior of Flexible Risers Subjected to Combined Loads

2004 ◽  
Vol 126 (2) ◽  
pp. 141-146 ◽  
Author(s):  
Roberto Ramos, ◽  
Celso Pupo Pesce
Keyword(s):  
Structural Analysis ◽  
Analytical Model ◽  
Constitutive Equations ◽  
Structural Behavior ◽  
Slip Model ◽  
Flexible Riser ◽  
Equilibrium Conditions ◽  
Combined Loads ◽  
External Pressures ◽  
Flexible Risers

This work presents an analytical model for the structural analysis of flexible risers subjected to combined loads of bending, twisting and tension, as well as internal and external pressures applied to the riser. The proposed formulation, which comprises equilibrium conditions, constitutive equations and geometrical relations, leads to the solution of the problem in terms of the loads supported by the layers and deformation components of a flexible riser subjected to the above mentioned combined loads. All the modeling hypotheses are highlighted in the work. Comparisons between analytical results using the full-slip model and experimental results obtained in literature are shown and discussed. Some proposals leading to improvement of the presented model are drawn in the conclusions.

A Consistent Analytical Model to Predict the Structural Behaviour of Flexible Risers Subjected to Combined Loads

2002 ◽  
Author(s):  
Roberto Ramos ◽  
Celso P. Pesce
Keyword(s):  
Analytical Model ◽  
Elastic Behaviour ◽  
Structural Behaviour ◽  
Element Analysis ◽  
Technical Literature ◽  
Combined Loads ◽  
External Pressures ◽  
Flexible Risers ◽  
Linear Elastic Behaviour ◽  
Ocean Environment

This work presents an analytical model for the structural analysis of flexible risers subjected to combined loads of bending, twisting and tension, as well as internal and external pressures applied to the riser. Flexible risers, either umbilical cables or flexible pipes, are complex structures used in offshore oil exploitation activities. Such structures are composed of several concentric polymeric and steel armour layers, which withstand static and dynamic loads applied by the floating production vessel and by the ocean environment. The complexity imposed mainly by geometry renders a finite element analysis of these structures practically unfeasible, even if we are to consider that all the materials obey a linear elastic behaviour. So, in order to calculate the stress distribution in the layers, as well as axial, torsional and flexural stiffness values of these structures, analytical methods have been proved to be, till now, a better choice. Using sets of equations, which comprise equilibrium conditions, constitutive equations and geometrical relations, it is possible to solve the problem for all the unknowns. This paper presents a consistent and comprehensive formulation leading to the solution in terms of stresses and deformation components in a flexible riser subjected to the above mentioned combined loads. It is based on the assumption of full-slip of the helically armoured layers after bending is imposed to the pipe. Other main modeling hypotheses are also highlighted in this work. The presented analytical model is, therefore, rather comprehensive and recovers, asymptotically, many results previously published in the technical literature. Comparisons between analytical results using the full-slip model and experimental results obtained in literature are shown and discussed. Some proposals leading to improvement of the presented model are drawn in the conclusions.

A Multi-Purpose Finite Element Model for Flexible Risers Studies

2014 ◽  
Author(s):  
Fabien Caleyron ◽  
Martin Guiton ◽  
Jean-Marc Leroy ◽  
Timothee Perdrizet ◽  
David Charliac ◽  
...  
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Element Model ◽  
Fe Model ◽  
Flexible Riser ◽  
Lateral Buckling ◽  
Axial Tension ◽  
External Pressures ◽  
Flexible Risers ◽  
Treatment Packages

The paper focuses on a Finite Element (FE) model developed at IFPEN, denominated 3D-Periodic, which is dedicated to flexible riser studies. It takes full advantage of the geometric and loading periodicities to reduce the model length and the CPU cost. The model is developed in a commercial FE software with dedicated pre- and post-treatment packages. The model can represent standard cyclic bending with internal pressure and axial tension as well as external pressures load cases to investigate the risk of lateral buckling of tensile armors or of pipe collapse.

Some Further Studies on the Axial–Torsional Behavior of Flexible Risers

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Roberto Ramos ◽  
Clóvis A. Martins ◽  
Celso P. Pesce ◽  
Francisco E. Roveri
Keyword(s):  
Finite Element ◽  
Analytical Model ◽  
Experimental Tests ◽  
Analytical Models ◽  
Analysis Tool ◽  
Full Data ◽  
Technical Literature ◽  
External Pressures ◽  
Flexible Risers ◽  
Ocean Environment

Flexible risers are complex structures composed of several concentric polymeric and steel armor layers that withstand static and dynamic loads applied by the floating production vessel and by the ocean environment. Determining the response of these structures when subjected to axisymmetric loadings (i.e., any combination of traction, torsion, and internal or external pressures) is an important task for the local structural analysis since it provides probable values for the loading distribution along the layers and, thus, allowing estimating the expected life of a riser using fatigue tools. Although finite element models have been increasingly used to accomplish this task in the last years, the simplicity and the reasonable accuracy provided by analytical models can be seen as reasons that justify their continued use, at least in the initial cycles of the design. However, any analytical model proposed for such a task must be checked with well-conducted experimental results in order to be considered as an acceptable analysis tool. The aims of this article are twofold: (i) to present the main results of experimental tests involving both internal pressure and traction loadings on a 63.5 mm (2.5 in.) flexible riser, carried out at the Institute for Technological Research of São Paulo (IPT), which can be used as a means of checking finite element or analytical models proposed by other researchers, and (ii) to compare some results obtained experimentally with those predicted by an analytical model which can also include any combination of axisymmetric loadings. Besides presenting full data concerning the internal structure of the riser, the experimental procedures used to perform the tests and the main results (e.g., Force × Displacement curves) are also presented. A brief discussion about the validity of some hypotheses that are usually assumed by analytical models found in the technical literature is made.

Limit State Philosophy in Pipeline Design

1987 ◽  
Vol 109 (1) ◽  
pp. 9-22 ◽  
Author(s):  
C. P. Ellinas ◽  
P. W. J. Raven ◽  
A. C. Walker ◽  
P. Davies
Keyword(s):  
Structural Analysis ◽  
Safety Factor ◽  
Current Knowledge ◽  
Limit State ◽  
Structural Behavior ◽  
Major Conclusion ◽  
Safety Factors ◽  
Suitable Framework ◽  
General Aspects ◽  
Pipeline Design

This paper considers the application of the limit state philosophy of structural analysis to pipeline design. General aspects of the philosophy are discussed and the approach to the evaluation of safety factors is reviewed. The paper further considers the various limit and serviceability states which would be relevant to a pipeline and reviews the various factors which may require consideration, before a code embodying the limit state philosophy could be formulated. A review of the state of current knowledge on various aspects of geometry and material characteristics, loading and structural behavior is presented. It is intended that such a review can be used as the basis for a larger study to provide guidance and data for the evaluation of rational levels of safety factor. The major conclusion reached by the authors is that a limit state philosophy would be valuable in providing a suitable framework, which may highlight the significant aspects of pipeline design and which can most easily accommodate new requirements and results obtained from research.

Cathodic Protection Design Consideration for an Offshore Flexible Riser Connected to an Impressed Current System

2021 ◽  
Author(s):  
Thierry Dequin ◽  
Clark Weldon ◽  
Matthew Hense
Keyword(s):  
Cathodic Protection ◽  
Sacrificial Anode ◽  
Flexible Riser ◽  
Flexible Pipe ◽  
Linear Resistance ◽  
Flexible Pipes ◽  
Flexible Risers ◽  
Impressed Current ◽  
Host Structure ◽  
Impressed Current Cathodic Protection

Abstract Flexible risers are regularly used to produce oil and gas in subsea production systems and by nature interconnect the subsea production system to the floating or fixed host facilities. Unbonded flexible pipes are made of a combination of metallic and non-metallic layers, each layer being individually terminated at each extremity by complex end fittings. Mostly submerged in seawater, the metallic parts require careful material selection and cathodic protection (CP) to survive the expected service life. Design engineers must determine whether the flexible pipe risers should be electrically connected to the host in order to receive cathodic protection current or be electrically isolated. If the host structure is equipped with a sacrificial anode system, then electrical continuity between the riser and the host structure is generally preferred. The exception is often when the riser and host structure are operated by separate organizations, in which case electrical isolation may be preferred simply to provide delineation of ownership between the two CP systems. The paper discusses these interface issues between hull and subsea where the hull is equipped with an impressed current cathodic protection (ICCP) system, and provides guidance for addressing them during flexible pipe CP design, operation, and monitoring. Specifically, CP design philosophies for flexible risers will be addressed with respect to manufacturing, installation and interface with the host structure’s Impressed Current Cathodic Protection (ICCP) system. The discussion will emphasize the importance of early coordination between the host structure ICCP system designers and the subsea SACP system designers, and will include recommendations for CP system computer modeling, CP system design operation and CP system monitoring. One of the challenges is to understand what to consider for the exposed surfaces in the flexible pipes and its multiple layers, and also the evaluation of the linear resistance of each riser segment. The linear resistance of the riser is a major determinant with respect to potential attenuation, which in turn largely determines the extent of current drain between the subsea sacrificial anode system and the hull ICCP system. To model the flexible riser CP system behavior for self-protection, linear resistance may be maximized, however the use of a realistic linear resistance is recommended for evaluation of the interaction between the host structure and subsea system. Realistic flexible linear resistance would also reduce conservatism in the CP design, potentially save time during the offshore campaign by reducing anode quantities, and also providing correct evaluation of drain current and stray currents.

scholarly journals Performance of asmetric structures reviewed with based plastic design performance (case study of application on building in Pekan Baru)

2020 ◽  
Vol 156 ◽  
pp. 05021
Author(s):  
Jati Sunaryati ◽  
Nidiasari ◽  
Alfadian
Keyword(s):  
Structural Analysis ◽  
Performance Analysis ◽  
Energy Method ◽  
Structural Behavior ◽  
Structural Performance ◽  
Plastic Design ◽  
Prone Area ◽  
Zonation Maps ◽  
Thrust Load

Performance-Based Plastic Design (PBPD) is a structural analysis that can be used to review structural performance. This method is increasingly popular to be used in the earthquake-prone area. This method is based on energy method that can be applied to steel or concrete structures. Meanwhile, Indonesia has already SNI 1726:2102 to be used as a guide in designing the thrust load to review the level of structural performance. Both of these things need to be used as a reference in areas that were initially considered safe from the earthquake but based on the development of earthquake micro zonation maps, it is very possible to become potential areas that also become earthquake regions. For this reason, the case of the structure that was built in the Pekanbaru area was taken. From the analyses of structural behavior, the structure that applied PBPD has greater displacement than the structures that apply the thrust load of SNI 1726: 2012. The percentage of displacement that occurred was 8-37 %. Based on performance analysis, the structures according to PBPD shows a better level of performance to the application of SNI 1726: 2012 thrust load.

Lumped Damage Mechanics

2015 ◽  
pp. 362-411
Keyword(s):  
Structural Analysis ◽  
Fracture Mechanics ◽  
Structural Damage ◽  
Damage Mechanics ◽  
Structural Behavior ◽  
Numerical Implementation ◽  
Plastic Range ◽  
Structural Collapse ◽  
Framed Structures ◽  
Damage And Fracture

As aforementioned, buildings in seismic zones must be designed to behave elastically under service loads or earthquakes of small intensity, and they can enter in the plastic range for events of intermediate intensity. Severe earthquakes are defined as those that are improbable but not impossible to happen during the lifetime of the structure. In these cases, structural damage, even damage that cannot be repaired, is allowed as long as there is no structural collapse. In order to design or certify safe structures, it is necessary to have computational tools that allow for the quantification of structural damage and that are able to describe structural behavior accurately near collapse. The elasto-plastic models present serious limitations in this sense. Damage and fracture mechanics represent a more rational option. The goal of this chapter is to describe how the concepts presented in Chapter 9 can be included in the mathematical models for the analysis of framed structures and its numerical implementation in structural analysis programs.

Flexible riser-bend stiffener top connection analytical model with I-tube

2020 ◽  
Vol 71 ◽  
pp. 102707 ◽  
Author(s):  
Yangye He ◽  
Murilo Augusto Vaz ◽  
Marcelo Caire
Keyword(s):  
Analytical Model ◽  
Flexible Riser

A Study on the Stability of a Mast Structure for Erecting a Large Crane

2011 ◽  
Vol 110-116 ◽  
pp. 1483-1490
Author(s):  
Hoon Hyung Jung ◽  
Chae Sil Kim
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Structural Analysis ◽  
Analytical Model ◽  
Gantry Crane ◽  
The Finite Element Method ◽  
Analysis Model ◽  
The Stability ◽  
The One ◽  
Two Stages

This paper describes a finite element structural analysis model and determines analysis methods appropriate for determining the stability of the mast of a crane. This analysis model allows various analysis approaches to be applied to the conditions affecting the construction of a large gantry crane in order to ensure the stability of the mast of the crane. The finite element method is used as a way to construct an analytical model that can help ensure the stability of the mast in two stages. The model is used in a two-stage analytical process that takes into account the conditions of the model. In this way, the model can be used to judge the stability of the mast. By allowing variation in the analysis approach used for the crane mast, the analysis model may be changed if the conditions of the one-girder gantry crane require. Designers may apply this method for the active analysis of the stability of a crane mast.

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