scholarly journals Solutions for Downslope Pipeline Walking on a Seabed With a Peaky Trilinear Soil Resistance Model

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Adriano Castelo ◽  
David White ◽  
Yinghui Tian
Keyword(s):  
Closed Form Solution ◽  
Form Solution ◽  
Soil Resistance ◽  
Finite Element Analyses ◽  
Soil Behavior ◽  
Rigid Plastic ◽  
Offshore Pipelines ◽  
Soil Response ◽  
Resistance Model ◽  
Analytical Expressions

Abstract Offshore pipelines used for transporting hydrocarbons are cyclically loaded by great variations of pressure and temperature. These variations can induce axial instability in such pipelines. This instability may cause the pipelines to migrate globally along their length; an effect known as pipeline walking. Traditional models of pipeline walking have considered the axial soil response as rigid-plastic (RP); however, such behavior does not match observations from physical soil tests. It leads to inaccurate estimates of walking rate (WR) per cycle and over design. In this paper, a trilinear (3L) soil resistance model is used to represent seabed resistance to investigate the behavior of pipeline walking. Different parameters, i.e., shapes and properties of trilinearity (within the peaky soil model type), have been considered leading to a closed-form solution. This solution improves the understanding of the main properties involved in the peaky trilinear soil behavior by providing a set of analytical expressions for pipe walking, which were benchmarked and validated against a set of finite element analyses.

Negative skin friction and the neutral plane

1994 ◽  
Vol 31 (4) ◽  
pp. 591-597 ◽  
Author(s):  
Elmer L. Matyas ◽  
J. Carlos Santamarina
Keyword(s):  
Closed Form ◽  
Key Words ◽  
Skin Friction ◽  
Closed Form Solution ◽  
Form Solution ◽  
Neutral Plane ◽  
Rigid Plastic ◽  
Negative Skin Friction ◽  
Elastic Plastic ◽  
Drag Forces

Current views indicate that negative skin friction on piles can be mobilized at small relative deformations and should be considered in all designs, primarily for serviceability conditions. An elastic-plastic closed-form solution is presented that permits an estimate of down-drag forces and the location of the neutral plane. It is shown that the conventional rigid-plastic solution may overestimate down-drag forces by as much as 50% and may also overestimate the depth of the neutral plane. Key words : piles, negative skin friction, neutral plane, capacity.

Finite Deformations of a Rigid Perfectly Plastic Arch

1962 ◽  
Vol 29 (3) ◽  
pp. 549-553 ◽  
Author(s):  
E. T. Onat ◽  
L. S. Shu
Keyword(s):  
Closed Form ◽  
Yield Point ◽  
Finite Deformation ◽  
Closed Form Solution ◽  
Form Solution ◽  
Finite Deformations ◽  
Deformation History ◽  
Rigid Plastic ◽  
Perfectly Plastic ◽  
History Of

The quasi-static postyield deformation of a rigid-plastic arch in the presence of geometry changes is considered. The problem is formulated in terms of a series of boundary-value problems concerned with rates of stress and velocities. In the present simple case, the consideration of the rate problem associated with the yield-point state of the structure enables one to construct a closed-form solution which describes the entire deformation history of the arch. However, the principal aim of the present study is to stress the central role played by the rate problem in the investigation of the finite deformation of structures.

An Unexpected Feature of a Class of Damage Evolution Models

2016 ◽  
Vol 713 ◽  
pp. 195-198
Author(s):  
Sergei Alexandrov
Keyword(s):  
Metal Forming ◽  
Damage Evolution ◽  
Plastic Material ◽  
Closed Form Solution ◽  
Material Model ◽  
Form Solution ◽  
Friction Condition ◽  
Rigid Plastic ◽  
Damage Evolution Equation ◽  
Rigid Plastic Material

The main objective of the present paper is to demonstrate, by means of a boundary value problem permitting a closed-form solution, that no solution exists under certain conditions in the case of a rigid/plastic material model including a damage evolution equation. The source of this feature of the solution is the sticking friction condition, which is often adopted in the metal forming literature.

scholarly journals Anisotropic Scattering Characteristics of a Radially Multilayered Gyrotropic Sphere

2017 ◽  
Vol 2017 ◽  
pp. 1-8
Author(s):  
Lei Cao ◽  
Yongpin Chen ◽  
Kai Kang
Keyword(s):  
Plane Wave ◽  
Spherical Wave ◽  
Fem Simulation ◽  
Closed Form Solution ◽  
Anisotropic Scattering ◽  
Form Solution ◽  
Scattering Coefficients ◽  
Full Wave ◽  
Spherical Scatterer ◽  
Analytical Expressions

We present a new closed-form solution to the scattering of a monochromatic plane wave by a radially multilayered gyrotropic sphere using the T-matrix method. This approach can be utilized to investigate the interactions of a plane wave and a gyrotropic spherical scatterer of multiple layers with each layer characterized by both permittivity and permeability tensors. Based on the completeness and noncoplanar properties of vector spherical wave functions (VSWFs), analytical expressions of the electromagnetic fields in each gyrotropic layer are first derived. The boundary conditions are then applied on each discontinuous interface to obtain the scattering coefficients. Validations are made by first comparing the radar cross section (RCS) values of a 2-layered gyrotropic sphere with that computed from the full-wave finite element method (FEM) simulation and then reducing the general case to uniaxial case to compare the RCS values with the published results computed by Fourier transform combined with VSWFs method; in both cases good agreements are observed. Several specific cases are fully explored to investigate how the RCS are influenced by the parameters of the multilayered spherical structure. The results show that when both electric and magnetic gyrotropy tensors are considered, the RCS of the multilayered spherical scatterer can be suppressed or enhanced, depending on proper configurations of the material parameters.

Plane-Strain Bending With Isotropic Strain Hardening at Large Strains

2010 ◽  
Vol 77 (6) ◽  
Author(s):  
Sergei Alexandrov ◽  
Yeong-Maw Hwang
Keyword(s):  
Strain Hardening ◽  
Plane Strain ◽  
Closed Form Solution ◽  
Bending Moment ◽  
Form Solution ◽  
Isotropic Hardening ◽  
Large Strains ◽  
Rigid Plastic ◽  
Elastic Plastic ◽  
Hardening Law

Finite deformation elastic-plastic analysis of plane-strain pure bending of a strain hardening sheet is presented. The general closed-form solution is proposed for an arbitrary isotropic hardening law assuming that the material is incompressible. Explicit relations are given for most popular conventional laws. The stage of unloading is included in the analysis to investigate the distribution of residual stresses and springback. The paper emphasizes the method of solution and the general qualitative features of elastic-plastic solutions rather than the study of the bending process for a specific material. In particular, it is shown that rigid-plastic solutions can be used to predict the bending moment at sufficiently large strains.

Pure Bending of Curved Beams of Thin-Walled Rectangular Box Section

1991 ◽  
Vol 58 (1) ◽  
pp. 154-156 ◽  
Author(s):  
R. D. Cook
Keyword(s):  
Finite Element ◽  
Analytical Method ◽  
Circumferential Stress ◽  
Closed Form Solution ◽  
Form Solution ◽  
Finite Element Analyses ◽  
Curved Beams ◽  
Pure Bending ◽  
The Subject ◽  
Thin Walled

A closed-form solution of the subject problem is presented. The analytical method resembles that used by Bleich (1933) to study curved beams of I or T section. It is found that the circumferential stress may be smaller than a perpendicular stress that arises from flexing of parts of the box. Accuracy of the solution is verified by comparison with finite element analyses.

scholarly journals Settlement Observations at Kars Bridge

1968 ◽  
Vol 5 (1) ◽  
pp. 28-45 ◽  
Author(s):  
W J Eden ◽  
H B Poorooshasb
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Closed Form Solution ◽  
Form Solution ◽  
Rigid Plastic ◽  
Excess Pore Water Pressure ◽  
Prior Testing ◽  
Preconsolidation Pressure ◽  
Leda Clay

A 26 ft. high approach fill was constructed in November 1959 for a bridge over the Rideau river near Kars, Ontario. The fill was placed over 50 ft. of Leda clay, the lower 30 ft. of which was extremely sensitive and compressible. Prior testing indicated that the preconsolidation pressure of the clay would be exceeded.Settlement gauges and piezometers under the fill have been observed since the start of construction. After 7½ years, 20 in. of settlement has occurred under the centre of the fill. Settlements are continuing at an appreciable rate although the excess pore water pressure has dissipated to a low level and is nearly constant through the clay layer.The field observations of settlement and pore water pressure are compared with values calculated and a closed form solution to the process of consolidation obtained by a heat balance integral technique and by considering the clay layer to be a rigid plastic.

View Factors in Radiation Between Two Parallel Oriented Cylinders of Finite Lengths

1982 ◽  
Vol 104 (2) ◽  
pp. 384-388 ◽  
Author(s):  
N. H. Juul
Keyword(s):  
Line Source ◽  
Closed Form Solution ◽  
Diffuse Radiation ◽  
Form Solution ◽  
View Factor ◽  
Double Integral ◽  
Integral Expression ◽  
View Factors ◽  
Limiting Case ◽  
Analytical Expressions

A simple double-integral expression for the diffuse radiation view factor, F12, between two parallel cylinders of finite lengths is derived. No closed-form solution appears possible except for the limiting case of infinite long cylinders for which an analytical expression for the view factor F12∞ is derived by applying the crossed string method. The accuracies of the line source approximations are evaluated, and the regions for which they are accurate to one percentage or better are identified. The view factor F12 between two opposing cylinders of equal length is computed by numerical integration and normalized by F12∞. The results are presented. Analytical expressions, which approximate the view factors between two opposite cylinders of finite length, are derived and their accuracy is evaluated over a useful parameter range. The range of their applications corresponds approximately to that for the line source approximation. This result is expected, because the errors are caused in part by blockage of radiation which is similar.

Master curves for Hertzian indentation on coating/substrate systems

2004 ◽  
Vol 19 (1) ◽  
pp. 94-100 ◽  
Author(s):  
Chun-Hway Hsueh ◽  
Pedro Miranda
Keyword(s):  
Finite Element ◽  
Analytical Solution ◽  
Coating Thickness ◽  
Closed Form Solution ◽  
Form Solution ◽  
Contact Radius ◽  
Finite Element Analyses ◽  
Master Curves ◽  
Modulus Ratio ◽  
Hertzian Indentation

An analytical model was developed to derive an approximate closed-form solution for indenter displacement when a rigid spherical indenter is pressed onto a coating/substrate system. Finite element analyses were also performed to verify the analytical solution. The results showed that the solution could be obtained from the analytical expression for Hertzian indentation on a homogeneous semi-infinite elastic medium multiplied by a modification term. This modification term is a function of two ratios: (i) Young’s modulus ratio between the coating and the substrate and (ii) the ratio between the coating thickness and the contact radius. Based on this modification term, master curves for Hertzian indentation on coating/substrate systems were plotted.

Semi-Closed-Form Displacement Equations for Calculating J-R Curves From Pipe Fracture Experiments

2015 ◽  
Author(s):  
Richard Olson ◽  
Ben Thornton
Keyword(s):  
Finite Element ◽  
Closed Form ◽  
Closed Form Solution ◽  
Strain Curve ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Form Solution ◽  
Finite Element Analyses ◽  
Pipe Bend ◽  
Point Bend

The equations to generate a J-R curve from a four-point bend test on circumferentially cracked pipe have been known for many years. Given the experimental pipe load-displacement record and crack growth, the only impediment to routinely calculating pipe J-R curves is the requirement to know the non-cracked pipe elastic and plastic displacements. Traditionally, finite element analyses are used to find these displacements. This paper presents a semi-closed-form solution for the total (elastic plus plastic) non-cracked pipe displacements that eliminates the need to perform finite element analyses to calculate a pipe J-R curve. Using a Ramberg-Osgood nonlinear representation of the stress-strain curve and the assumption that plane sections remain plane, beam bending equations can be written to find nonlinear beam displacements for pipe bend geometries with a base metal crack. Building on this result, the solution is extended to the dissimilar metal weld (DMW) case with five nonlinear materials. The non-cracked pipe displacement solutions are presented as well as comparisons using these equations between compact tension specimen J-R toughness curves and J-R curves from pipe experiments.

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