Frictional Flexible Pipe Model Using Macroelements

2020 ◽  
Author(s):  
Rodrigo Provasi ◽  
Fernando Geremias Toni ◽  
Clovis de Arruda Martins
Keyword(s):  
Structural Behavior ◽  
Computational Time ◽  
Memory Usage ◽  
Relative Movement ◽  
Flexible Pipe ◽  
Finite Element Software ◽  
Geometrical Characteristics ◽  
Pipe Model ◽  
Contact Formulation ◽  
Flexible Pipes

Abstract Flexible pipes are structures composed by many layers varying in composition and shapes, in which the structural behavior is defined by the role it must play. Flexible pipes construction is such that layers are unbounded, allowing relative movement between them and modifying its behavior. Many approaches are used to model such cables, both analytical and numerical, such as the macroelements model. This sort of model consists in finite elements where geometrical characteristics are taken into account by the formulation and is under development by the authors. Previous works have shown in detail the modeled cylindrical and helical elements, as well node-to-node connection elements (bounded, frictionless and frictional), which have allowed simplified flexible pipe with bonded elements simulations. This article will focus on modeling a simplified cable consisting in an external sheath, two armor layers and a polymeric core, since recent advances in the contact formulation opens the possibility to incorporate friction between the layers. Taking into consideration accuracy, computational time and memory usage, results from macroelements are compared to commercial finite element software.

Bonded Flexible Pipe Model Using Macroelements

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Rodrigo Provasi ◽  
Fernando Geremais Toni ◽  
Clóvis de Arruda Martins
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Structural Behavior ◽  
Small Displacement ◽  
Relative Movement ◽  
Memory Consumption ◽  
Flexible Pipe ◽  
Pipe Model ◽  
Flexible Pipes ◽  
Compliant Behavior

Flexible pipes are structures composed by many layers that vary in composition and shapes. The structural behavior of each layer is defined by the role it must play. The construction of flexible pipes is such that the layers are unbounded, with relative movement between them. Even though this characteristic is what enables its high bending compliant behavior, if the displacements involved are small, a bonded analysis is interesting to grasp the general characteristics of the problem. The bonded hypothesis means that there is no movement relative between layers, which is fine for a small displacement analysis. It also creates a lower bound for the movement, since when considering increasingly friction coefficient values, it tends to the bonded situation. The main advantage of such hypothesis is that the system becomes linear, leading to fast solving problems (when compared to full frictional analysis) and giving insights to the pipe behavior. The authors have previously developed a finite element based one called macroelements. This model enables a fast-solving problem with less memory consumption when compared to multipurpose software. The reason behind it is the inclusion of physical characteristics of the problem, enabling the reduction in both number of elements and memory used and, since there are less elements and degrees-of-freedom, faster solved problems. In this paper, the advantages of such model are shown by using examples that are representative of a simplified, although realistic, flexible pipe. Comparisons between the macroelement model and commercial software are made to show its capabilities.

Efficient Analysis of a Deep-Seabed Integrated Mining System Using a Subsystem Synthesis Method

2015 ◽  
Author(s):  
Sung-Soo Kim ◽  
Hong-seon Yun ◽  
Chang-Ho Lee ◽  
Hyung-Woo Kim ◽  
Sup Hong
Keyword(s):  
Dynamic Analysis ◽  
Equations Of Motion ◽  
Synthesis Method ◽  
Computational Time ◽  
Manganese Nodules ◽  
Flexible Pipe ◽  
Mining System ◽  
Pipe System ◽  
Multibody Model ◽  
Pipe Model

A deep-seabed integrated mining system for collecting manganese nodules consists of a mining vessel, a vertical lifting pipe, a lifting pump, an intermediate buffer station, a flexible pipe, and a self-propelled mining robot. Manganese nodules collected by the mining robot are transferred to the buffer and then lifted up to the vessel. Dynamic analysis of such a system is a challenging task, since large displacements due to deformation must be considered in the very long lifting pipe and the flexible pipe system. Because non-linear effects must be considered in the modeling of the lifting pipe and the flexible pipe model, nodal coordinates must be used in the flexible multibody model. This requires a large amount of computational time for the dynamic analysis. Moreover, the concept of multiple mining robots was introduced recently, increasing the complexity. An efficient method for the dynamic analysis of the integrated mining system is necessary. In this study, to improve the efficiency of analysis, a subsystem synthesis method was developed for the deep-seabed integrated mining system which can also be extended to efficiently analyze multiple mining robots. Subsystem equations of motion were separately generated for the vessel-lifting pipe subsystem and the flexible pipe-mining robot subsystem. The efficiency of the subsystem synthesis method was verified theoretically by comparing arithmetic operational counts of the developed subsystem synthesis method with those of the conventional method.

Simplified Approaches to Modeling of Lateral Wire Buckling in the Tensile Armour of Flexible Pipes

2012 ◽  
Author(s):  
Niels H. Østergaard ◽  
Anders Lyckegaard ◽  
Jens H. Andreasen
Keyword(s):  
Structural Integrity ◽  
The Other ◽  
Computational Time ◽  
Flexible Pipe ◽  
Deep Waters ◽  
Outer Sheath ◽  
Flexible Pipes ◽  
Load Carrying ◽  
Present Context ◽  
Deformation Patterns

In the present paper, simplifications of methods developed for modeling of lateral wire buckling in the tensile armour layers of flexible pipes are proposed. Lateral wire buckling may occur during pipe laying in ultra-deep waters. In this scenario a flexible pipe is subjected to repeated bending and axial compression due to hydrostatic pressure on the end cap of an empty pipe. If the outer sheath is breached, these loads may cause wire slippage towards states in which the load carrying ability is reduced and wire buckling in the circumferential pipe direction occurs. This leads to characteristic deformation patterns, which may compromise the structural integrity of the entire pipe structure. On the other hand, these loads may cause overstressing of the wires, if the outer sheath is intact. Simplifications of established models for calculation of the load carrying ability are in the present context proposed in a manner, by which the effect of adjacent pipe layers on the postbuckled response can be estimated. The simplifications enables significant reduction of the computational time, which is necessary to calculate the load carrying ability of a given pipe structure.

scholarly journals Burst pressure prediction of fiber-reinforced flexible pipes with arbitrary generatrix

2021 ◽  
Vol 16 ◽  
pp. 155892502199081
Author(s):  
Guo-min Xu ◽  
Chang-geng Shuai
Keyword(s):  
Transfer Matrix ◽  
Linear Equations ◽  
Burst Pressure ◽  
Fiber Reinforced ◽  
Flexible Pipe ◽  
Theoretical Derivation ◽  
Design And Optimization ◽  
Flexible Pipes ◽  
Novel Method ◽  
Winding Angle

Fiber-reinforced flexible pipes are widely used to transport the fluid at locations requiring flexible connection in pipeline systems. It is important to predict the burst pressure to guarantee the reliability of the flexible pipes. Based on the composite shell theory and the transfer-matrix method, the burst pressure of flexible pipes with arbitrary generatrix under internal pressure is investigated. Firstly, a novel method is proposed to simplify the theoretical derivation of the transfer matrix by solving symbolic linear equations. The method is accurate and much faster than the manual derivation of the transfer matrix. The anisotropy dependency on the circumferential radius of the pipe is considered in the theoretical approach, along with the nonlinear stretch of the unidirectional fabric in the reinforced layer. Secondly, the burst pressure is predicted with the Tsai-Hill failure criterion and verified by burst tests of six different prototypes of the flexible pipe. It is found that the burst pressure is increased significantly with an optimal winding angle of the unidirectional fabric. The optimal result is determined by the geometric parameters of the pipe. The investigation method and results presented in this paper will guide the design and optimization of novel fiber-reinforced flexible pipes.

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 Evaluation of p-delta effect in structural seismic response

2018 ◽  
Vol 162 ◽  
pp. 04019 ◽  
Author(s):  
Sardasht Sardar ◽  
Ako Hama
Keyword(s):  
Seismic Response ◽  
Pushover Analysis ◽  
Nonlinear Dynamic Analysis ◽  
Time History ◽  
Steel Structure ◽  
Nonlinear Static Analysis ◽  
Structural Behavior ◽  
Finite Element Software ◽  
History Analysis ◽  
Nonlinear Static

Numerous recent studies have assessed the effect of P-Delta on the structures. This paper investigates the effect of P-Delta in seismic response of structures with different heights. For indicating the effect of P-Delta, nonlinear static analysis (pushover analysis) and nonlinear dynamic analysis (Time history analysis) were conducted by using finite element software. The results showing that the P-Delta has a significant impact on the structural behavior mainly on the peak amplitude of building when the height of the structures increased. In addition, comparison has been made between concrete and steel structure.

Optimization of Flexible Pipes Dynamic Analysis Using Artificial Neural Networks

2016 ◽  
Author(s):  
Victor Chaves ◽  
Luis V. S. Sagrilo ◽  
Vinícius Ribeiro Machado da Silva
Keyword(s):  
Dynamic Analysis ◽  
Fem Simulation ◽  
Training Data ◽  
Local Analysis ◽  
Flexible Pipe ◽  
Nonlinear Fem ◽  
Irregular Wave ◽  
Flexible Pipes ◽  
Artificial Neural ◽  
Hybrid Methodology

Irregular wave dynamic analysis is an extremely computational expensive process on flexible pipes design. One emerging method that aims to reduce these computational costs is the hybrid methodology that combines Finite Element Analyses (FEA) and Artificial Neural Network (ANN). The proposed hybrid methodology aims to predict flexible pipe tension and curvatures in the bend stiffener region. Firstly using short FEA simulations to train the ANN, and then using only the ANN and the prescribed floater motions to get the rest of the response histories. Two approaches are developed with respect to the training data. One uses an ANN for each sea state in the wave scatter diagram and the other develops an ANN for each wave incidence direction. In order to evaluate the accuracy of the proposed approaches, a local analysis is applied, based on the predicted tension and curvatures, to calculate stresses in tension armour wires and the corresponding flexible pipe fatigue lifes. The results are compared to those from full nonlinear FEM simulation.

Investigation on Mechanical Properties of Fibreglass Reinforced Flexible Pipes Under Torsion

2018 ◽  
Author(s):  
Pan Fang ◽  
Yuxin Xu ◽  
Shuai Yuan ◽  
Yong Bai ◽  
Peng Cheng
Keyword(s):  
Mechanical Behavior ◽  
Torsion Angle ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Load Condition ◽  
Element Model ◽  
Flexible Pipe ◽  
Torsional Load ◽  
Flexible Pipes ◽  
The Impact

Fibreglass reinforced flexible pipe (FRFP) is regarded as a great alternative to many bonded flexible pipes in the field of oil or gas transportation in shallow water. This paper describes an analysis of the mechanical behavior of FRFP under torsion. The mechanical behavior of FRFP subjected to pure torsion was investigated by experimental, analytical and numerical methods. Firstly, this paper presents experimental studies of three 10-layer FRFP subjected to torsional load. Torque-torsion angle relations were recorded during this test. Then, a theoretical model based on three-dimensional (3D) anisotropic elasticity theory was proposed to study the mechanical behavior of FRFP. In addition, a finite element model (FEM) including reinforced layers and PE layers was used to simulate the torsional load condition in ABAQUS. Torque-torsion angle relations obtained from these three methods agree well with each other, which illustrates the accuracy and reliability of the analytical model and FEM. The impact of fibreglass winding angle, thickness of reinforced layers and radius-thickness ratio were also studied. Conclusions obtained from this research may be of great practicality to manufacturing engineers.

Mechanical Behaviors of Steel Strip Reinforced Flexible Pipes Under Bending

2018 ◽  
Author(s):  
Shan Jin ◽  
Shuai Yuan ◽  
Ting Liu ◽  
Peihua Han ◽  
Yong Bai
Keyword(s):  
Steel Strip ◽  
Practical Application ◽  
Pure Bending ◽  
Flexible Pipe ◽  
Four Point Bending ◽  
Offshore Engineering ◽  
Flexible Pipes ◽  
Proposed Model ◽  
Composite Pipe ◽  
Good Coincidence

Steel strip reinforced flexible pipe (SSRFP) is a kind of unbonded composite pipe, which has more application foreground in offshore engineering due to its excellent mechanics and the considerable flexibility. In practical application, SSRFP will inevitably experience bending during reeling process and installation. In this paper, the mechanical behavior of SSRFP subjected to pure bending are studied both experimentally and numerically. A four-point bending equipment is utilized to conduct the full-scale laboratorial tests of SSRFP. Furthermore, the commercial software ABAQUS is employed to simulate its ovalization instability. The results acquired from the ABAQUS simulation are compared with the ones from verification bending experiment, which are in good coincidence with each other. The proposed model and the relative results may be of interest to the manufacture factory engineers.

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