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Finite Element Solutions for Geotechnical Engineering

Lateral Loading of Suction Pile in 3D

Chain

Sea Bed

Suction Pile

Buoy

GTS NX

2

00 Overview

• This tutorial identifies the soil–

structure interaction by analyzing

construction stage of 3D suction pile.

• It is possible to review in detail the

stress distributions on cross-sections,

which is not possible in 2D models.

• Also, interface is added between

ground and pile to simulate the

ground-structure interaction more

realistically.

• The evaluation of the soil-structure

behavior is done by using shell

elements, not by simple rigid

elements.

• Lastly, the tutorial will compare the

results to a plaxis 3D tutorial.

Procedure

GTS NX

3

01 Material & Property

Name Clay

Material Isotropic

Model Type Mohr-Coulomb

General

Elastic Modulus (E) [kN/m2] 1000

Inc. of Elastic Modulus [kN/m3] 1000

Poisson’s Ratio (v) 0.35

Unit Weight (γ) [kN/m3] 20

Ko 0.5

Porous

Unit Weight (Saturated) [kN/m3] 20

Drainage Parameters Undrained B

Non-Linear

Cohesion (c) [kN/m2] 5

Inc. of Cohesion [kN/m3] 4

Frictional Angle (Φ) [deg] 0

[unit : kN, m]Ground

Reference level 0 m

Reference level 0 m

GTS NX

4


Name Steel-Pile

Material Isotropic

Model Type Elastic

Elastic Modulus (E) [kN/m2] 21e+07

Poisson’s Ratio (v) 0.3

Unit Weight (γ) [kN/m3] 78

Name Outer Interface Inner Interface

Type Plane Shell Wizard Plane Shell Wizard

R (Strength Reduction

Factor)0.7 1

tv (Virtual Thickness) 0.1 0.1

Seepage Flow

(m/sec/m)0.003 0.003

[unit : kN, m]Structure

Interface

Name Steel-Pile

Property 2D

Model Type Shell

Thickness 0.05

GTS NX

5

• You can start the tutorial by opening

a new file and setting the analysis

settings to 3D and units to kN / m /

sec

Menu > New1

Procedure1

2


GTS NX

6

• Define materials and properties from

tables in previous slides

Mesh > Material > New >

Isotropic

Define the 2 materials from

table.

• Clay

Select Porous > Drainage

Parameters > Undrained

(Effective Stiffness / Undrained

Strength).

• Steel-Pile

Activate Structure Box for Steel

Pile

1

Procedure1


GTS NX

7

• Define materials and properties from

tables in previous slides

Mesh > Property > Create

Define the 2 the properties

• Clay is 3D

• Shell is 2D with 0.05m

thickness

1

Procedure1


GTS NX

8

1

Geometry > Surface & Solid>

Box

-Origin: (-30, 0, -30)

- Width X = 60

- Width Y = 30

- Height = 30

Change Work Plane to X-Y

Draw Circle Face

• Location (0,0,0)

• Radius (2.5m)

• Check On Make Face

2

2

02 Geometry Modeling

Procedure

1

2

3

GTS NX

9

1

Geometry Protrude> Extrude

- Select: Circle Face

- Direction: Z-axis

- Method: Length

- Distance: -10

- OK

Geometry > Boolean > Solid

- Target : Soil Block

- Tool: Pile Cylinder

- OK

2

2


Procedure

1

GTS NX

10

1

Geometry > Transform > Mirror

-- Select: 2 soilds

- Plane: XZ-Plane (as shown in

the figure)

- Copy

- Ok

2


Procedure

1

GTS NX

11

1

Mesh > Generate > 3D

- Auto-Solid tab

- Select: both cylinders

- Size: 1

- Tetra Mesher

- Property: clay

- >> Higher Order Elemet

- Mesh Set: inner soil

- Apply

- Select: both soil soilds

- Size: 3.75

- Tetra Mesher

- Property: clay

- Mesh Set: Outer soil

- >> Higher Order Elemet

- Apply

03 Mesh Generation

Procedure

1

2

2

GTS NX

12

1

Mesh > Element > Extract

- Geometry tab

- View Toolbar: Top

-Type: Face

- Select: the 6 side and top

faces where the pile will be

modeled

- Property: Pile Wall

- Mesh Set: Pile

- OK

- Measure 7m down the right

side of the pile shell.

- Draw 3D point at (2.5, 0, -7)

03 Mesh Generation

Procedure

1

2

2

GTS NX

13

1

Mesh > Element > Interface

- Plane tab

- View Toolbar: Front

- Type: From Shell

- Select: all the wall elements

- Direction: Negative Normal

- Merge Nodes: Check on

- Select: all the bottom nodes of

pile elements (as shown in the

figure)

- Property Parameters: Wizard

- Strength Reduction Factor(R): 1

- Virtual Thickness (tv) 0.1

- OK

- Create Rigid Link Element: Check

on

- Mesh Set:

- Inner Interface

Apply

- REPEAT for Outer Interface

using R = 0.7 (next slide)

03 Mesh Generation

Procedure

1

GTS NX

14

1

Mesh > Element > Interface

- Plane tab


- Type: From Shell

- Select: all the wall elements

- Direction: Normal

- Merge Nodes: Check on

- Select: all the bottom nodes of

pile elements (as shown in the

figure)

- Property Parameters: Wizard

- Strength Reduction Factor(R):

0.7

- Virtual Thickness (tv) 0.1

- OK

- Create Rigid Link Element:

Check on

- Mesh Set: Outer Interface

- OK

03 Mesh Generation

Procedure

1

2

2

GTS NX

15

The interface material can be defined using the following equation. Using the stiffness of adjacent elements and nonlinear

parameters, the virtual thickness (tv) and strength reduction factor (R) is applied. Interface material stiffness and parameters

are applied differently according to the relative stiffness difference between neighboring ground and structural members. The

Wizard can be used to simplify this process.

The general Strength reduction factor for structural members and neighboring ground properties are as follows.

Checking the Element size consideration calculates the interface material properties considering the average length(line),

average area(face) of the neighboring ground element when creating an interface. In other words, the average length(l),

average area(A) are multiplies to the virtual thickness in the equation below to calculate the tangent, normal direction stiffness

of the interface.

If the consideration is not checked, the unit length(area) is applied. The thickness is defined separately for a line interface.

The thickness is an important element when using the interface on a ground material that displays hardening behavior.

Generally, the neighboring ground particle size is input, but if an accurate numerical value is not available, the default value

from the program is used. For a 3D model, like the 1 in the example above, the surface interface does not need a thickness.

When defining the stiffness against seepage for an interface element, the “permeability coefficient” can be defined to be the

same as the permeability coefficient of the ground. If the option is not checked, the layer is considered to be impermeable.

03 Mesh Generation

GTS NX

16

1

Show all mesh sets.

Static/Slope Analysis >

Boundary > Constraint

- Auto tab

- Boundary Set: Ground support

- Apply

04 Analysis Setting

Procedure

1

GTS NX

17

1

Show all mesh sets.

Static/Slope Analysis > Load >

Self Weight

- Gz: -1

- Load Set: Self weight

- OK

04 Analysis Setting

Procedure

1

GTS NX

18

1

Show only the ‘Pile’ mesh set.


Pressure

- Face tab


- Object Type: Node

- Select: the highlighted point

(as shown in the figure 7m

below top on right side)

- Direction Type: Coordinate

X: 1949 kN

Z :1125 kN

- - Load Set: 30 degrees

- OK

04 Analysis Setting

Procedure

1

GTS NX

19

1



Pressure

- Face tab


- Object Type: Node





X: 1724 kN

Z :1447 kN


- OK

04 Analysis Setting

Procedure

1

GTS NX

20

1



Pressure

- Face tab


- Object Type: Node





X: 1447 kN

Z :1724 kN


- OK

04 Analysis Setting

Procedure

1

GTS NX

21

1



Pressure

- Face tab


- Object Type: Node





X: 1125 kN

Z :1949 kN


- OK

04 Analysis Setting

Procedure

1

GTS NX

22

1

Show all mesh sets.

Static/Slope Analysis >

Construction Stage > Stage Set

- Add 4 cases

- Stage Name: Initial

- Select the highlighted mesh,

boundary and load sets. Drag and

drop them into Activated Data

from Set Data.

- Show Data: Activate

- Define Water Level: 50 m

- Clear Displacement: Check on

- Save

04 Analysis Setting

Procedure

1

2

2

GTS NX

23

1

- New

- Stage Name: Pile

- Select the highlighted mesh sets.

Drag and drop them into

Activated & Deactivated Data

from Set Data.

- Save

04 Analysis Setting

Procedure

1

GTS NX

24

1

- New

- Stage Name: 30 degrees

- Select the highlighted mesh

set. Drag and drop it the 30

degrees load

- Activate Analysis Control

-Allow Undrained

Material Behavior

- Set 10 Load Steps

- Every Increment

-- Save

- Repeat 3 times for the other

Construction Stage sets by

making Copies and replacing the

last stage with the corresponding

load.

04 Analysis Setting

Procedure

1

GTS NX

25

1

Analysis > Analysis Case >

General

- Title: 30 Degrees

- Solution Type: Construction

Stage

- Analysis Control

- Initial Stage for Stress Analysis:

Check on

- Initial Stage: 1: Initial

- Apply K0 Condition: Check on

- OK

Automatically consider Water

Pressure: Check on

-- OK

Analysis > Analysis > Perform

- Analysis Case: Check on

- OK

04 Analysis Setting

Procedure

1

2

2

GTS NX

26

1

30 Degrees > Increment 10 >

Displacement > TOTAL

TRANSLATION (V)

Activate only half soil of the mesh

sets

Results > Show/Hide > Min/Max

Result > General > Smooth:

Fringe

Result > General > Deform:

Undeformed

Compare to results from plaxis

tutorial Loading of Suction Pile

for same load stage.

05 Results

Procedure

1

2

2

Plaxis

GTS NX

GTS NX

27



TRANSLATION (V)

Select Iso Value Surface option

Set Capped Style Upper Part

Limit to 2 mm

05 Results

Procedure

1

2

2

1

GTS NX

28

1



TRANSLATION (V)

Results > Advanced > Extract

Select Analysis Set: 30 Degrees

Results: Total Translation

Select All

Nodal Results Extraction:

Maxiumum

Click Table

Select Step Value and

Displacements

Show Graph

05 Results

Procedure

1

2

2

3

3

1

2

3

GTS NX

29

1



TRANSLATION (V)

Rotate Model as shown

Check On Multi Step Animation

Recording

Click Steps and Select All

OK

Click Save to create animation.

You can edit Animation in Properties

drop down window menu

05 Results

Procedure

1

2

2

3

3

GTS NX

30

30 degree load > Shell Element

Forces > Axial Forces XX


Forces > Moment YY

30 degree load > Interface

Stress > Normal X

05 Results

Procedure

1

2

3

Friction force between pile and

ground

1

2

2

GTS NX

31

1

40 Degrees > Displacement >

TOTAL TRANSLATION (V)


sets



Fringe


Undeformed




Forces > Moment YY

05 Results

Procedure

1

2

2

3

3

GTS NX

32

1




sets



Fringe


Undeformed




Forces > Moment YY

05 Results

Procedure

1

2

2

3

3

GTS NX

33

1




sets



Fringe


Undeformed




Forces > Moment YY

05 Results

Procedure

1

2

2

3

3

GTS NX

34

This tutorial was based in part on PLAXIS Tutorial: 3D Loading of Suction Pile

• Plaxis only models half of the shape, not the full pile and ground. GTS NX modeled full 3D geometry.

GTS NX has more CAD import capabilities as well as more geometry CAD based commands for more

accurate modeling.

• Plaxis used a RIGID BODY Object instead of Shell Element for the Pile. It has no structural properties,

therefore it can’t give any structural results like forces or moments like GTS NX does.

• Plaxis used a HELPER Object for local mesh refinement. GTS NX has more options for mesh refinement

during and before meshing including command Mesh Size Control.

• GTS NX has more options in post analysis results inspection including animation of construction process,

on curve diagrams, results extraction/graphing, 3D pdf report, iso value surfaces.

06 Conclusion

GTS NX

35

Thank you!

Lateral Loading of Suction Pile in 3Dnorthamerica.midasuser.com/web/.../Lateral_Loading_of_Suction_Pile... · Lateral Loading of Suction Pile in 3D Chain Sea Bed Suction ... - Apply

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