Pipe-soil interaction elements

This problem contains basic test cases for one or more Abaqus elements and features.

This page discusses:

ProductsAbaqus/Standard

Elements tested

PSI24

PSI26

PSI34

PSI36

Features tested

The constitutive behavior of the pipe-soil interaction (PSI) elements is tested. The material is defined with different material response in the different directions. The axial and transverse vertical response is symmetric about the origin, while the vertical response uses different behavior for positive and negative relative displacement. An isotropic model, which uses the same material model in all the directions, is also tested.

The local coordinate system procedure is also tested. Temperature and field variable dependence of material properties is tested.

Problem description

The problem consists of a single PSI element subjected to a prescribed displacement history. The far-field edge is fixed, and the displacement history is applied to the pipeline side. The value of the prescribed displacement changes in such a way that the constitutive response corresponding to negative and positive relative displacement is verified.

Each input file contains as many PSI elements as the number of coordinate directions; i.e., two for the two-dimensional elements (PSI24 and PSI26) and three for the three-dimensional elements (PSI34 and PSI36). The prescribed displacement applied to each element is in a different direction. The elements are not connected in any way. Both regular static steps, with small and large displacements, and linear perturbation steps are considered.

Material:

Elastic stiffness in axial direction: 1.0 × 106
Elastic stiffness in vertical direction: 2.0 × 106
Elastic stiffness in horizontal direction: 4.0 × 106
ASCE formulae for sand:
Axial direction:  
γ¯ 19000.0
K0 0.3
δ 30.0°
D 0.6
εa 0.003
Vertical direction:
γ  24000.0
Nvp 0.5
Nv 0.4
Nvn 0.3
ε¯vp 0.15
ε¯vn 0.015
Horizontal direction:
Nh 0.25
ε¯h 0.1
ASCE formulae for clay:
Axial direction:
S 1000
α 1.0
D 0.6
ε¯a 0.005
Vertical direction:
Nvp 0.8
Nvn 0.4
ε¯vp 0.15
ε¯vn 0.1
Horizontal direction:
Nh 0.25
ε¯h 0.1

Results and discussion

The forces applied to the pipeline match the analytical values.

Input files

Linear material behavior:
epsi24ls1.inp

PSI24 element with small displacements.

epsi24ls2.inp

PSI24 element with user-defined orientation, small displacements.

epsi24ls3.inp

PSI24 element with user-defined orientation, unsymmetric stiffness, small displacements.

epsi34ls1.inp

PSI34 element with small displacements, isotropic behavior.

epsi24ln3.inp

PSI24 element with field variable dependence, large displacements, isotropic behavior.

epsi26ln1.inp

PSI26 element with large displacements.

epsi26ln2.inp

PSI26 element with user-defined orientation, unsymmetric stiffness, large displacements.

epsi36lp1.inp

PSI36 element with perturbations.

epsi36ln1.inp

PSI36 element with temperature dependence, large displacements.

Nonlinear material behavior:
epsi24ns1.inp

PSI24 element with small displacements.

epsi26ns1.inp

PSI26 element with isotropic behavior.

epsi26nn2.inp

PSI26 element with temperature dependence, large displacements.

epsi34np1.inp

PSI34 element with perturbation.

epsi34ns1.inp

PSI34 element with temperature dependence, small displacements.

epsi36ns1.inp

PSI36 element with large displacements.

ASCE formulae for sand:
epsi24ss1.inp

PSI24 element with small displacements.

epsi24sn1.inp

PSI24 element with large displacements, user-defined orientation.

epsi34sn1.inp

PSI34 element with temperature dependence, large displacements.

epsi36sn1.inp

PSI36 element with large displacements, temperature dependence.

ASCE formulae for clay:
epsi24cn1.inp

PSI24 element with large displacements, user-defined orientation.

epsi26cn1.inp

PSI26 element with large displacements, user-defined orientation.

epsi34cs1.inp

PSI34 element with small displacements.

epsi34cn3.inp

PSI34 element with field variable dependence, large displacements.

User subroutine:
epsi26un1.inp

PSI26 element with large displacements.

epsi26un1.f

The user subroutine used with epsi26un1.inp.

epsi34us1.inp

PSI34 element with small displacements.

epsi34us1.f

The user subroutine used with epsi34us1.inp.