Simple Numerical Models for Pipeline Walking Accounting for Mitigation and Complex Soil Response

Loading And Unloading ◽

Internal Pressures ◽

Subsea Pipelines ◽

Pipeline Design

Non-buried subsea pipelines subjected to high internal pressures and high operational temperatures (HP/HT) may experience significant axial expansion. Asymmetries in the loading and unloading in startups and shutdowns (e.g. due to seabed slope, temperature transients or riser tension) may cause the axial displacements to accumulate over operational cycles, in a ratcheting process often called “pipeline walking”. Despite the complexity of the pipe-soil interaction governing this behavior, several analytical and simple numerical models have been used for estimating the total accumulated pipeline axial displacement. These simple models are powerful tools in preliminary phases of a pipeline design, although their use is limited due to the simplifications. This paper presents results of a simple numerical model able to account for additional features in the preliminary walking assessment, such as loads on mitigation systems. The models were originally prepared to assess walking mitigation for some rigid flowlines in a recently installed subsea system, and remarkable agreement with complex three-dimensional finite element models was observed. The effect of different types of mitigation systems on the global behavior of the pipelines is presented and discussed. The influence of the pipe-soil interaction model employed is also investigated.

Analyses of Different FE Models for HP/HT-Pipeline Walking With Sliding End Structures

Volume 3: Pipeline and Riser Technology ◽

10.1115/omae2012-83636 ◽

2012 ◽

Author(s):

Adriano Castelo ◽

Nelson Szilard Galgoul

Keyword(s):

Finite Element ◽

Mechanical Behavior ◽

Three Dimensional ◽

Element Model ◽

Foundation Design ◽

Internal Pressures ◽

Seabed Bathymetry ◽

Pipeline Design

Non-buried subsea pipelines subjected to high internal pressures and high operational temperatures (HP/HT) might experience significant axial expansion. If this movement is restrained by an end structure, considerably high loads can be imposed to the system. Sliding foundations have been used to minimize this effect, allowing free end displacements. Regarding the aforementioned loads, the thermo-mechanical behavior of HP/HT pipelines interacts with the end restraints in a complex manner. Axial displacements can accumulate over the operational cycles, in a phenomenon known as “pipeline walking”. If the sliding foundation design does not account for these accumulated displacements, axial loads (not considered in the pipeline design) might be imposed. As a result, the overall thermo-mechanical behavior in terms of lateral buckling and walking can change significantly. Two recently published papers present the results of different analysis methodologies for the same structure. The corresponding analyses were performed using two different tools: (1) a non-linear three-dimensional finite element model considering pipe-soil interaction with full 3D seabed bathymetry and (2) a simplified one-dimensional model published in OMAE 2011. In both cases, the limited sliding range was imposed to the model ends. Both calculation tools show similar overall results of pipeline global behavior, but the results of the end reaction after a few operational cycles are somewhat different. Stimulated by these recently published papers, which present the results of different performed finite element analyses; this paper was developed to investigate the same problem, but now starting off with a third software, and rerunning the two previous analyses in the same software and adding an intermediate modeling level.

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

Numerical analysis of the dynamic interaction between a non-pneumatic mechanical elastic wheel and soil containing an obstacle

10.1177/0954407016660946 ◽

2016 ◽

Vol 231 (6) ◽

pp. 731-742 ◽

Cited By ~ 9

Author(s):

Xianbin Du ◽

Youqun Zhao ◽

Qiang Wang ◽

Hongxun Fu

Keyword(s):

Finite Element ◽

Three Dimensional ◽

Interaction Model ◽

Dynamic Interaction ◽

Constitutive Law ◽

Elastic Wheel ◽

Non Linear ◽

Mechanical Elastic Wheel ◽

An innovative non-pneumatic tyre called the mechanical elastic wheel is introduced; significant challenges exist in the prediction of the dynamic interaction between this mechanical elastic wheel and soil containing an obstacle owing to its highly non-linear properties. To explore the mechanical properties of the mechanical elastic wheel and the soil, the finite element method is used, and a non-linear three-dimensional finite element wheel–soil interaction model is also established. Hyperelastic incompressible rubber, which is one of the main materials of the mechanical elastic wheel, is analysed using the Mooney–Rivlin model. The modified Drucker–Prager cap plasticity constitutive law is utilized to describe the behaviour of the soil, and the obstacle is represented as an elastic body. Simulations with different rotational speeds of the mechanical elastic wheel were conducted. The stress distribution and the displacement of the mechanical elastic wheel and the soil were obtained, and the effects of different rotational speeds on the displacement, the velocity and the acceleration of the hub centre are presented and discussed in detail. These results can provide useful information for optimization of the mechanical elastic wheel.

Effects of multiple vein microjoints on the mechanical behaviour of dragonfly wings: numerical modelling

Royal Society Open Science ◽

10.1098/rsos.150610 ◽

2016 ◽

Vol 3 (3) ◽

pp. 150610 ◽

Cited By ~ 21

Author(s):

H. Rajabi ◽

N. Ghoroubi ◽

A. Darvizeh ◽

E. Appel ◽

S. N. Gorb

Keyword(s):

Numerical Models ◽

Complex Structure ◽

Three Dimensional ◽

Micro Air Vehicles ◽

Insect Wings ◽

Computational Data ◽

Biological Composites ◽

Dragonfly Wings

Dragonfly wings are known as biological composites with high morphological complexity. They mainly consist of a network of rigid veins and flexible membranes, and enable insects to perform various flight manoeuvres. Although several studies have been done on the aerodynamic performance of Odonata wings and the mechanisms involved in their deformations, little is known about the influence of vein joints on the passive deformability of the wings in flight. In this article, we present the first three-dimensional finite-element models of five different vein joint combinations observed in Odonata wings. The results from the analysis of the models subjected to uniform pressures on their dorsal and ventral surfaces indicate the influence of spike-associated vein joints on the dorsoventral asymmetry of wing deformation. Our study also supports the idea that a single vein joint may result in different angular deformations when it is surrounded by different joint types. The developed numerical models also enabled us to simulate the camber formation and stress distribution in the models. The computational data further provide deeper insights into the functional role of resilin patches and spikes in vein joint structures. This study might help to more realistically model the complex structure of insect wings in order to design more efficient bioinspired micro-air vehicles in future.

Parametric Analysis of Rib Pillar Stability in a Longitudinal Sublevel Open Stoping Operation in an Underground Copper Mine in Southern Africa

Materials Proceedings ◽

10.3390/materproc2021005011 ◽

2021 ◽

Vol 5 (1) ◽

pp. 11

Author(s):

Kostas Kaklis ◽

Zach Agioutantis ◽

Munyindei Masialeti ◽

Jerome Yendaw ◽

Thierry Bineli Betsi

Keyword(s):

Parametric Analysis ◽

Numerical Models ◽

Three Dimensional ◽

Stability Factor ◽

Finite Element Models ◽

Pillar Stability ◽

The Third ◽

Mining Project ◽

The pillar stability factor (PSF) is calculated in three different mining stages for a sublevel open stoping mining project located in northern Botswana. Several three-dimensional finite element models were developed by varying the stope span. Pillar strength was estimated using the Lunder and Pakalnis equation and pillar stress was obtained from the numerical models. As mining progresses, both the first and second mining stages meet the rib pillar stability factor requirement for safe extraction. Geometrical improvements are suggested in the mining layout for the third mining stage to achieve the required PSF, which is based on international practices.

On the limitations of some popular numerical models of flagellated microswimmers: importance of long-range forces and flagellum waveform

Royal Society Open Science ◽

10.1098/rsos.180745 ◽

2019 ◽

Vol 6 (1) ◽

pp. 180745 ◽

Cited By ~ 3

Author(s):

C. Rorai ◽

M. Zaitsev ◽

S. Karabasov

Keyword(s):

Stokes Flow ◽

Numerical Models ◽

Shape Change ◽

Three Dimensional ◽

Head Shape ◽

Flow Approximation ◽

Resistive Force Theory ◽

Benchmark Solutions

For a sperm-cell-like flagellated swimmer in an unbounded domain, several numerical models of different fidelity are considered based on the Stokes flow approximation. The models include a regularized Stokeslet method and a three-dimensional finite-element method, which serve as the benchmark solutions for several approximate models considered. The latter include the resistive force theory versions of Lighthill, and Gray and Hancock, as well as a simplified approximation based on computing the hydrodynamic forces exerted on the head and the flagellum separately. It is shown how none of the simplified models is robust enough with regards to predicting the effect of the swimmer head shape change on the swimmer dynamics. For a range of swimmer motions considered, the resulting solutions for the swimmer force and velocities are analysed and the applicability of the Stokes model for the swimmers in question is probed.

Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation and Control of Adaptive Systems; Structural Health Monitoring ◽

Modeling of a Shape Memory Alloy Circular Bar Under Combined Axial-Torsional Loading

10.1115/smasis2012-8017 ◽

2012 ◽

Author(s):

Masood Taheri Andani ◽

Amin Alipour ◽

Ahmadreza Eshghinejad ◽

Mohammad Elahinia

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Constitutive Relations ◽

Three Dimensional ◽

Torsional Loading ◽

Equilibrium Equations ◽

Loading And Unloading ◽

Circular Bar ◽

In this paper, a semi-analytical analysis of the pseudoelastic response of shape memory alloy rods and tubes subjected to combined axial and torsional loading is proposed. A three-dimensional phenomenological SMA constitutive model is simplified to obtain the corresponding two-dimensional constitutive relations. The rod is partitioned into a finite number of narrow annular regions and the equilibrium equations are found in each annular region for both loading and unloading paths. Several numerical examples are presented to demonstrate the efficiency of the proposed method, and the results are compared with three-dimensional finite element simulations.

Effects of pile shape in improving the performance of monopiles embedded in onshore clays

Canadian Geotechnical Journal ◽

10.1139/cgj-2014-0397 ◽

2015 ◽

Vol 52 (8) ◽

pp. 1144-1158 ◽

Cited By ~ 6

Author(s):

B. Pedram

Keyword(s):

Numerical Models ◽

Three Dimensional ◽

Elastoplastic Material ◽

Lateral Capacity ◽

Pile Diameter ◽

Overconsolidated Clays ◽

Clay Layers ◽

Pile Length

This paper presents the results from a series of three-dimensional finite element analyses, which examine the benefits of adopting square pile–tower structures instead of circular monopiles. The advantages of square monopiles are brought out in this paper through a parametric study with a Tresca soil model, where the shear strength and modulus of elasticity varied with depth and the pile–tower structures were modelled as an elastoplastic material. The effects of pile diameter, pile thickness, eccentricity, and pile length for free-head pile–towers embedded in lightly overconsolidated and heavily overconsolidated clays were investigated. From the results of the numerical models, it is clear that the ultimate lateral capacity and stiffness of square pile–tower structures are substantially higher than of circular structures embedded in clay layers. Moreover, the amount of rotation and displacement of square structures are not significantly affected compared to circular monopiles.

Numerical Modeling of Seismic-induced Soil Response Around Submarine Pipeline

The Open Civil Engineering Journal ◽

10.2174/1874149501206010098 ◽

2012 ◽

Vol 6 (1) ◽

pp. 98-106

Author(s):

X. L. Zhang ◽

D. S. Jeng

Keyword(s):

Pore Pressure ◽

Three Dimensional ◽

Seismic Loading ◽

Element Model ◽

Internal Stresses ◽

Submarine Pipeline ◽

Soil Response ◽

Overall Stability ◽

Seismic-induced pore pressure and effective stresses in the saturated porous seabed under seismic loading are the main factors that govern the overall stability of submarine pipelines. In most of the previous investigations for the seismic-induced dynamic response around a submarine pipeline have been limited to two-dimension cases. In this paper, a three-dimensional finite element model including buried pipeline is established by extending DYNE3WAC. Based on the numerical model presented, the effects of pipeline geometry and soil characteristics on the seismic-induced pore pressure of the seabed and internal stresses of submarine pipeline will be discussed in detail.

An Investigation of the Bisymmetric Hydrostatic Collapse of Flexible Pipes Based on Equivalent Layer Approaches

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4046170 ◽

2020 ◽

Vol 142 (4) ◽

Author(s):

José Renato M. de Sousa ◽

Marcelo K. Protasio ◽

Luís Volnei S. Sagrilo ◽

Djalene Maria Rocha

Keyword(s):

Numerical Models ◽

Three Dimensional ◽

Experimental Tests ◽

Collapse Mechanism ◽

Fe Model ◽

Flexible Pipe ◽

Flexible Pipes ◽

Equivalent Ring ◽

Abstract The hydrostatic collapse strength of a flexible pipe is largely dependent on the ability of its carcass and/or pressure armor to resist radial loading and, therefore, its prediction involves an adequate modeling of these layers. Hence, initially, this work proposes a set of equations to estimate equivalent mechanical properties for these layers, which allows their modeling as equivalent orthotropic cylinders. Particularly, equations to predict the equivalent ring bend stiffness are obtained by simulating several two-point static ring tests with a three-dimensional finite element (FE) model based on beam elements and using these results to form datasets that are analyzed with a symbolic regression (SR) tool. The results of these analyses are the closed-form equations that best fit the provided datasets. After that, these equations are used in conjunction with a three-dimensional shell FE model (FEM) and a previously presented analytical model to study the bisymmetric hydrostatic collapse mechanism of flexible pipes. The predictions of these models agreed well with the collapse pressures obtained with numerical models and in experimental tests thus indicating the potential use of this approach in the design of flexible pipes.