Flexible Pipe Modeling Using Finite Macro-Elements

2014 ◽  
Author(s):  
Rodrigo Provasi ◽  
Clóvis de Arruda Martins
Keyword(s):  
Numerical Models ◽  
Local Level ◽  
Three Dimensional ◽  
Analytical Models ◽  
Great Effort ◽  
Algebraic Equations ◽  
Flexible Pipe ◽  
Commercial Software ◽  
Macro Elements ◽  
Pipe Model

Modeling flexible pipes in the local level is not a trivial task and many authors have employed a great amount of time in such task. The non-triviality arises from the various layers and their interaction, which are pretty tough to correctly model. The possible approaches to solve the problem are divided in to major categories: analytical models and numerical models. The analytical ones rely on a great number of hypotheses and, after a great effort, result in a system of algebraic equations. The numerical ones can be further differentiated in the ones developed using commercial software and the other ones using proprietary models. The authors choose the second way to approach the problem and presented in previous works a group of elements called macro-elements, including a cylindrical element for orthotropic layers, a three dimensional curved beam for helical elements, a rigid connection and a contact element, both dealing with different node displacement natures. These elements take into account the physical and geometrical characteristics of the components. In this paper a pipe model, with a flexible internal core, two tensile armors and an external sheath, will be simulated and its the results will be checked against commercial software and commented.

scholarly journals Mechanical Characterization of Timber-to-Timber Composite (TTC) Joints with Self-Tapping Screws in a Standard Push-Out Setup

2020 ◽  
Vol 10 (18) ◽  
pp. 6534
Author(s):  
Chiara Bedon ◽  
Martina Sciomenta ◽  
Massimo Fragiacomo
Keyword(s):  
Mechanical Characterization ◽  
Numerical Models ◽  
Three Dimensional ◽  
Analytical Models ◽  
Small Scale ◽  
Load Bearing ◽  
Timber Constructions ◽  
Technical Interest ◽  
Push Out

Self-tapping screws (STSs) can be efficiently used in various fastening solutions for timber constructions and are notoriously able to offer high stiffness and load-carrying capacity, compared to other timber-to-timber composite (TTC) joint typologies. The geometrical and mechanical characterization of TTC joints, however, is often hard and uncertain, due to a combination of various influencing parameters and mechanical aspects. Among others, the effects of friction phenomena between the system components and their reciprocal interaction under the imposed design loads can remarkably influence the final estimates on structural capacity, in the same way of possible variations in the boundary conditions. The use of Finite Element (FE) numerical models is well-known to represent a robust tool and a valid alternative to costly and time consuming experiments and allows one to further explore the selected load-bearing components at a more refined level. Based on previous research efforts, this paper presents an extended FE investigation based on full three-dimensional (3D) brick models and surface-based cohesive zone modelling (CZM) techniques. The attention is focused on the mechanical characterization of small-scale TTC specimens with inclined STSs having variable configurations, under a standard push-out (PO) setup. Based on experimental data and analytical models of literature, an extended parametric investigation is presented and correlation formulae are proposed for the analysis of maximum resistance and stiffness variations. The attention is then focused on the load-bearing role of the steel screws, as an active component of TTC joints, based on the analysis of sustained resultant force contributions. The sensitivity of PO numerical estimates to few key input parameters of technical interest, including boundaries, friction and basic damage parameters, is thus discussed in the paper.

scholarly journals Nonlinear numerical simulation of punching shear behaviour of reinforced concrete flat slabs with shear-heads

2019 ◽  
Author(s):  
D.V. Bompa ◽  
A.Y. Elghazouli
Keyword(s):  
Reinforced Concrete ◽  
Failure Modes ◽  
Numerical Models ◽  
Three Dimensional ◽  
Structural Response ◽  
Analytical Models ◽  
Shear Behaviour ◽  
Flat Slabs ◽  
Modes Of Failure ◽  
Concrete Damage

This paper examines the structural response of reinforced concrete flat slabs, provided with fully-embedded shear-heads, through detailed three-dimensional nonlinear numerical simulations and parametric assessments using concrete damage plasticity models. Validations of the adopted nonlinear finite element procedures are carried out against experimental results from three test series. After gaining confidence in the ability of the numerical models to predict closely the full inelastic response and failure modes, numerical investigations are carried out in order to examine the influence of key material and geometric parameters. The results of these numerical assessments enable the identification of three modes of failure as a function of the interaction between the shear-head and surrounding concrete. Based on the findings, coupled with results from previous studies, analytical models are proposed for predicting the rotational response as well as the ultimate strength of such slab systems. Practical recommendations are also provided for the design of shear-heads in RC slabs, including the embedment length and section size. The analytical expressions proposed in this paper, based on a wide-ranging parametric assessment, are shown to offer a more reliable design approach in comparison with existing methods for all types of shear-heads, and are suitable for direct practical application.

A Three-Dimensional Curved Beam Element for Helical Components Modeling

2011 ◽  
Author(s):  
Rodrigo Provasi ◽  
Clo´vis de Arruda Martins
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Beam Element ◽  
Analytical Models ◽  
Cylindrical Layer ◽  
Curved Beam ◽  
Macro Elements ◽  
Curved Beam Element ◽  
Flexible Pipes ◽  
Custom Made

The offshore industry is in constant evolution due to the need of reaching new oil fields in increasingly water depths. In this scenario, not only new types of platforms are being designed, but also new types of flexible pipes and new umbilical cable configurations. The greatest difficulty to generate a new concept for a riser is to determine if it is viable or not. Flexible pipes and umbilical cables are complicated to model, due to the interactions between their layers and the large number of possible arrangements. To predict their behavior, adequate models are necessary. One can rely on finite element models, which show a great difficulty in mesh generation and convergence (especially due to the contact pairs). One can also rely on analytical models, which have many limitations due to simplifications (even though necessary ones). Another possible approach is to define macro elements, which represent a component, instead of classical finite elements (such as tetrahedral elements). Related to that approach, a numeric method using macro-elements is proposed. It consists in creating elements which has the desired characteristics of the problem in its formulation, leading to robust custom-made elements and to coarse meshes (since the complexity of the problem is within the element). Some elements are proposed in this model: a concentric one for cylindrical layer modeling; a three-dimensional curved beam for helices; a bridge element for node connection; and a contact element, for gap and friction treatment. The first two of them are already concluded and the later ones are being designed. This paper presents the three-dimensional curved beam element, which takes into account the effects of curvature and tortuosity. This is accomplished by using a strong coupling between displacements and assuming that the twist and shear strains varies linearly within the element. Using such hypothesis, the shear lock phenomenon is also avoided. This formulation is implemented and their results compared to those obtained by a classical finite element modeling tool, with good agreement.

Improvements on the Numerical Analysis of the Coupled Extensional–Torsional Response of a Flexible Pipe

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Héctor E. M. Muñoz ◽  
José R. M. de Sousa ◽  
Carlos Magluta ◽  
Ney Roitman
Keyword(s):  
Cross Sections ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Axial Rotation ◽  
Nonlinear Finite Element ◽  
Analytical Models ◽  
Fe Model ◽  
Flexible Pipe ◽  
Torsional Response ◽  
Axial Twist

In this paper, the coupled extensional–torsional behavior of a 4 in. flexible pipe is studied. The pipe is subjected to pure tension and two different boundary conditions are considered: ends free and prevented from axially rotating. The response of the pipe is predicted with a three-dimensional nonlinear finite element (FE) model. Some aspects of the obtained results are discussed, such as the effect of restraining the axial rotation at the extreme sections of the model; the effect of friction or adhesion between the layers of the pipe on the induced axial rotation (or torque) and elongation; and the reduction to simple plane behavior usually assumed by analytical models. The numerical results are compared to the ones measured in experimental tests. Reasonable agreement is observed between all results pointing out that the analyzed pipe is torque balanced and that friction mainly affects the axial twist induced by the applied tension. Moreover, the cross sections of the pipe remain straight with the imposed load, but different axial rotations are found in each layer.

scholarly journals Interactions of Jets with Interstellar and Intergalactic Media

1989 ◽  
Vol 134 ◽  
pp. 467-468
Author(s):  
Paul J. Wiita ◽  
Alexander Rosen
Keyword(s):  
Power Law ◽  
Galactic Halo ◽  
Numerical Models ◽  
Three Dimensional ◽  
Analytical Models ◽  
Beam Power ◽  
Two Phase ◽  
Cosmological Redshift ◽  
Dimensional Boundary ◽  
Fixed Power

Jets emanating from AGN propagate first through an isothermal, but roughly power-law in density, galactic halo and then into a hotter, less dense, and uniform intergalactic medium (IGM) or intracluster medium (ICM). We use a three-dimensional boundary-following code (Mitteldorf & Wiita 1988), altered to allow for a two-phase external medium. We vary the beam power, P, the redshift, z, the radius of the galactic halo/IGM interface, Rh, the steepness of the power-law fall-off within the halo, n, and the temperature ratio of the IGM (or ICM) to the halo, Tr to estimate the average linear sizes of extragalactic radio galaxies (RGs). Good agreement is obtained with regard to the relationships between the overall linear size of such radio sources and both the total radio power (at fixed redshift) and the cosmological redshift (at fixed power). These numerical models tend to support recent analytical models (Gopal–Krishna & Wiita [GW] 1987, 1988).

On the Coupled Extensional–Torsional Response of Flexible Pipes

2009 ◽  
Author(s):  
He´ctor E. M. Merino ◽  
Jose´ R. M. de Sousa ◽  
Carlos Magluta ◽  
Ney Roitman
Keyword(s):  
Cross Sections ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Axial Rotation ◽  
Analytical Models ◽  
Fe Model ◽  
Flexible Pipe ◽  
Torsional Response ◽  
Flexible Pipes ◽  
Axial Twist

In this paper, the coupled extensional-torsional behavior of a 4″ flexible pipe is studied. The pipe was subjected to pure tension and two different boundary conditions were considered: ends free and prevented from axially rotating. The response of the pipe is predicted with a three-dimensional nonlinear finite element (FE) model. Some aspects of the obtained results are discussed, such as: the effect of restraining the axial rotation at the extreme sections of the model; the effect of friction or adhesion between the layers of the pipe on the induced axial rotation (or torque) and elongation; and the reduction to simple plane behavior usually assumed by analytical models. The numerical results are compared to the ones measured in experimental tests performed at COPPE/UFRJ. Reasonable agreement is observed between all results pointing out that the analyzed pipe is torque balanced and that friction mainly affects the axial twist or torque led by the applied tension. Moreover, the cross-sections of the pipe remain straight with the imposed load, but different axial rotations are found in each layer.

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

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 ◽  
Dimensional Finite Element ◽  
Equivalent Ring ◽  
Three Dimensional Finite Element

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.

Numerical and Experimental Study of a Flexible Pipe Under Torsion

2010 ◽  
Author(s):  
He´ctor E. M. Merino ◽  
Jose´ Renato M. de Sousa ◽  
Carlos Magluta ◽  
Ney Roitman
Keyword(s):  
Experimental Study ◽  
Finite Element ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Nonlinear Finite Element ◽  
Analytical Models ◽  
Fe Model ◽  
Pure Torsion ◽  
Flexible Pipe ◽  
Torsional Loads

The torsional behavior of a 4″ flexible pipe is here studied. The pipe was subjected to clockwise and anticlockwise torsion and also to torsion combined with tension. For pure torsion, two different boundary conditions were considered: ends free to elongate and prevented from elongating. When tensional and torsional loads are imposed to the pipe, only analyses with ends prevented from elongating are carried out. In all cases, the response of the pipe is predicted with a three-dimensional nonlinear finite element (FE) model and with a classical analytical model. Experimental tests performed at COPPE/UFRJ are also employed to validate the theoretical estimations. The obtained results point out that the pipe is torque balanced for clockwise torsion, but it is not balanced for anti-clockwise torsion. Moreover, analytical models for axissymetric analyses assume that the layers of a flexible pipe are subjected to the same twist and elongation, but the FE results state that this hypothesis holds only for anti-clockwise torsion. Therefore, some differences were found between the FE and analytical models mainly when clockwise torsion is considered. Finally, due to its ability to deal with friction and adhesion between layers, the FE estimations agreed quite well with the experimental measures.

Investigation of Curved Polymeric Piezoelectric Active Diaphragms

2003 ◽  
Vol 125 (2) ◽  
pp. 145-154 ◽  
Author(s):  
Kelly C. Bailo ◽  
Diann E. Brei ◽  
Karl Grosh
Keyword(s):  
Polyvinylidene Fluoride ◽  
Acoustic Radiation ◽  
Numerical Models ◽  
Three Dimensional ◽  
Analytical Models ◽  
Acoustic Response ◽  
Structural Dynamic ◽  
Geometric Configurations ◽  
Parametric Studies ◽  
Acoustic Output

Piezoelectric active diaphragms hold promise as an alternative to using passive diaphragms driven by voice coils for sound generation and noise cancellation applications. This paper presents an in-depth investigation of the acoustic response for curved polymeric piezoelectric active diaphragms. Simple analytical models were derived and experimentally validated to predict the structural dynamic and acoustic responses for generic polyvinylidene fluoride (PVdF) constant curvature active diaphragms with variable geometric parameters (width, radius, subtended angle, thickness). These models are useful for design purposes and for capturing the overall behavioral trends. To analyze the acoustic response mechanisms further, three-dimensional numerical models were also developed and experimentally validated. Parametric studies based upon these models reveal the potential of high acoustic outputs (over 100 dB in the far field) from optimized geometric configurations with subtended angles differing from the conventionally utilized flat, semicircular or circular configurations. These studies, corroborated by experiments on a variety of active diaphragm prototypes, conclude that the acoustic output is governed by the structural ring resonance, which can be designed such that the most efficient acoustic radiation is within the particular frequency range of operation.

scholarly journals The Efficiency of a Fence of Tidal Turbines in the Alderney Race: Comparison between Analytical and Numerical Models

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 892
Author(s):  
Jérôme Thiébot ◽  
Nasteho Djama Dirieh ◽  
Sylvain Guillou ◽  
Nicolas Guillou
Keyword(s):  
Numerical Models ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Analytical Models ◽  
Yield Potential ◽  
Hydrodynamic Characteristics ◽  
Energy Yield ◽  
Three Dimensional Model ◽  
Lower Efficiency ◽  
Array Efficiency

Assessing the efficiency of a tidal turbine array is necessary for adequate device positioning and the reliable evaluation of annual energy production. Array efficiency depends on hydrodynamic characteristics, operating conditions, and blockage effects, and is commonly evaluated by relying on analytical models or more complex numerical simulations. By applying the conservations of mass, momentum, and energy in an idealized flow field, analytical models derive formulations of turbines’ thrust and power as a function of the induction factor (change in the current velocity induced by turbines). This simplified approach also gives a preliminary characterization of the influence of blockage on array efficiency. Numerical models with turbines represented as actuator disks also enable the assessment of the efficiency of a tidal array. We compare here these two approaches, considering the numerical model as a reference as it includes more physics than the analytical models. The actuator disk approach is applied to the three-dimensional model Telemac3D in realistic flow conditions and for different operating scenarios. Reference results are compared to those obtained from three analytical models that permit the investigation of the flow within tidal farm integrating or excluding processes such as the deformation of the free surface or the effects of global blockage. The comparison is applied to the deployment of a fence of turbines in the Alderney Race (macro-tidal conditions of the English Channel, northwest European shelf). Efficiency estimates are found to vary significantly from one model to another. The main result is that analytical models predict lower efficiency as they fail to approach realistically the flow structure in the vicinity of turbines, especially because they neglect the three-dimensional effects and turbulent mixing. This finding implies that the tidal energy yield potential could be larger than previously estimated (with analytical models).

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