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TRANSCRIPT
Integrated Solver Optimized for the next generation 64-bit platform
Finite Element Solutions for Geotechnical Engineering
3D Excavation and Piled-Raft Foundation
GTS NX
2
00 Overview
• This tutorial identifies the soil–
structure interaction by analyzing
construction stage of 3D retaining wall
excavation.
• 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 retaining wall to simulate
the ground-structure interaction more
realistically.
• The evaluation of the soil-structure
behavior is done by using pile
elements, not by simple beam
elements.
• Also, pile elements are perfect for
evaluating the soil-structure behavior
because it can consider the influence
of interface between pile and adjacent
ground.
Procedure
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01 Material & Property
Name Sand Sandy gravel Clay
Material Isotropic Isotropic Isotropic
Model Type Mohr-Coulomb Mohr-Coulomb Mohr-Coulomb
General
Elastic Modulus (E) [kN/m2] 22,300 74,300 37,150
Poisson’s Ratio (v) 0.3 0.3 0.3
Unit Weight (γ) [kN/m3] 20 20 20
Ko 0.5 0.5 0.5
Porous
Unit Weight (Saturated) [kN/m3] 21 21 21
Drainage Parameters Drained Drained Drained
Non-Linear
Cohesion (c) [kN/m2] 10 10 50
Frictional Angle (Φ) [deg] 33 36 25
[unit : kN, m] Ground
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01 Material & Property
Name Concrete-Raft Concrete-Structure
Material Isotropic Isotropic
Model Type Elastic Elastic
Elastic Modulus (E) [kN/m2] 2e+07 2e+07
Poisson’s Ratio (v) 0.3 0.18
Unit Weight (γ) [kN/m3] 24 24
Name Pile to Soil interface Pile to Raft interface
Model Type Pile Pile
Ultimate Shear Force [kN/m2] 2,000 1e+010
Shear Stiffness Modulus (Kt)
[kN/m3] 1e+06 1e+08
Normal Stiffness Modulus (Kn)
[kN/m3] 1e+07 1e+09
Tip Bearing Capacity [kN] 2,000 -
Tip Spring Stiffness [kN/m] 1e+06 -
[unit : kN, m]
[unit : kN, m]
Structure
Pile
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02 Geometry Modeling
• You can start the tutorial by opening
the start file in which basic materials
and properties have already been
predefined.
Start > Open
- ‘3D Excavation and Piled-Raft
Foundation_start.gts’
- Open
1
Procedure 1
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In GTS NX, 2 types of coordinate system are used: Global coordinate system (GCS) and Work plane coordinate system
(WCS). GCS is a fixed coordinate system indicated in red(X-axis), green(Y-axis), and blue (Z-axis) colors at the right
bottom corner on the screen. WCS is a coordinate system which locates at center of the working window and moves with the
work plane. So if the work plane changes, WCS will also change. 3D absolute coordinates are necessary to locate geometry
in the space, but practically relative coordinates are commonly used, for example to indicate length. You can process
modeling by inputting 2D coordinates (XY plane in WCS) after moving the work plane to proper location.
Keep in mind that in case of inputting direction for extruding geometry or defining load/boundary conditions, it always follows
Global coordinate system.
WCSWorkplane Coodinate System
GCSGlobal Coodinate System
02 Geometry Modeling
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1
Geometry > Point & Curve >
Rectangle
- Location: (0,0) <60,60>
- Location: (18,21) <24,18>
- OK
Geometry > Point & Curve >
Point
- Tabular Input tab
- Read From File…
- ‘Location of Piles.txt’
- OK
( ): ‘ABS x, y’
< >: ‘REL dx, dy’
2
2
02 Geometry Modeling
Procedure
1
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1
Geometry > Transform >
Translate
- Translate tab
- Select: 24 points
- Direction: Z-axis
- Method: Copy(Uniform)
- Distance: -10.3
- OK
Geometry > Point & Curve >
Line
- 3D tab
- Define Snap: Point Snap
- Use mouse to select the
corresponding nodes from top
layer to the bottom layer nodes.
2
2
02 Geometry Modeling
Procedure
1
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1
Geometry > Protrude > Extrude
- Extrude tab
- Selection filter: Basic > Wire (W)
- Select: the highlighted wire
(as shown in the figure)
- Direction: Z-axis
- Reverse Direction: Check on
- Length: 3
- Apply
- Select: the highlighted face
(as shown in the figure)
- Direction: Z-axis
- Reverse Direction: Check on
- Length: 4
- Apply
2
2
02 Geometry Modeling
Procedure
1
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1
- Select: the highlighted face
(as shown in the figure)
- Direction: Z-axis
- Reverse Direction: Check on
- Length: 3
- Apply
- Select: the highlighted face
(as shown in the figure)
- Direction: Z-axis
- Reverse Direction: Check on
- Length: 0.6
- Apply
2
2
02 Geometry Modeling
Procedure
1
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1
- Selection filter: Basic > Wire (W)
- Select: the highlighted wire
(as shown in the figure)
- Direction: Z-axis
- Reverse Direction: Check on
- Length: 3
- Apply
- Select: the highlighted face
(as shown in the figure)
- Direction: Z-axis
- Reverse Direction: Check on
- Length: 15
- Apply
2
02 Geometry Modeling
Procedure
1
2
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1
- Select: the highlighted face
(as shown in the figure)
- Direction: Z-axis
- Reverse Direction: Check on
- Length: 20
- OK
02 Geometry Modeling
Procedure
1
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1
Select the highlighted solid
segments and right click on
mouse and select Transparency.
Display Mode (Geometry) >
Random Color
2
1
2
02 Geometry Modeling
Procedure
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1
02 Geometry Modeling
Procedure
1 Geometry > Divide > Solid
- Select: 2 boundary soil layers
(as shown in the figure)
- Selection filter: Basic > Solid (D)
- Dividing Tools: all the inner
solid segments
- OK
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1
Mesh > Control > Size Ctrl.
- Edge tab
- View Toolbar: Top
- Pick & Rect: Polyline
- Select: all the in-plane
boundary edges (cross the
selecting line through the
edges)
- Method: Number of Divisions
- Division: 10
- Apply
- Show only all the inner solid
segments
- View Toolbar: Front
- Pick & Rect: Polyline
- Select: the side edges
- Method: Number of Divisions
- Division: each value as shown
in the figure
- OK
03 Mesh Generation
Procedure
1
2 2
3
4
3
3
4
3
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1
Mesh > Generate > 3D
- Auto-Solid tab
- Select: the top solid segment
- Size: 1
- Hybrid Mesher
- Property: 1: Top Soil
- Mesh Set: Excav#1
- Apply
- Select: the second solid
segment
- Size: 1
- Hybrid Mesher
- Property: 2: Mid Soil
- Mesh Set: Excav#2
- Apply
03 Mesh Generation
Procedure
1
2
2
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1
- Select: the third solid segment
- Size: 1
- Hybrid Mesher
- Property: 2: Mid Soil
- Mesh Set: Excav#3
- Apply
- Select: the bottom solid
segment
- Size: 1
- Hybrid Mesher
- Property: 2: Mid Soil
- Mesh Set: Excav#4-Raft
- Apply
03 Mesh Generation
Procedure
1
2
2
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1
- Show all the boundary solid
segments
- Select: the top solid segment
- Division: 3
- Hybrid Mesher
- Property: 1: Top Soil
- Mesh Set: Top soil
- Apply
- Select: the second solid
segment
- Division: 5
- Hybrid Mesher
- Property: 2: Mid Soil
- Mesh Set: Mid soil
- Apply
03 Mesh Generation
Procedure
1
2
2
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1
- Select: the bottom solid
segment
- Division: 4
- Hybrid Mesher
- Property: 3: Bot Soil
- Mesh Set: Bot soil
- OK
Hide all mesh sets and show only
the inner solid segments.
Mesh > Element > Extract
- Geometry tab
- View Toolbar: Top
-Type: Face
- Select: the four sides where
the wall will be modelled
- Property: 5: Wall
- Mesh Set: Wall
- OK
03 Mesh Generation
Procedure
1
2
2
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1
Mesh > Element > Interface
- Plane tab
- View Toolbar: Front
- Method: From Shell
- Select: all the wall elements
- Merge Nodes: Check on
- Select: all the bottom nodes of
wall elements (as shown in the
figure)
- Property Parameters: Wizard
- Strength Reduction Factor(R):
0.8
- OK
- Create Rigid Link Element:
Check on
- Mesh Set: Wall Interface
- OK
03 Mesh Generation
Procedure
1
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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
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1
Hide all mesh sets and show only
the geometry lines for piles.
Mesh > Generate > 1D
- Select: all the lines
- Division: 1
- Property: 6: Pile
- Mesh Set: Piles
- OK
03 Mesh Generation
Procedure
1
2
2
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1
Mesh > Element > Pile/Pile Tip
- Pile tab
- Select: all the Pile elements
- Property: 7: Pile to Soil
interface
- Mesh Set: Pile interface
- Apply
- Pile Tip tab
- View Toolbar: Front
- Select: all the bottom nodes of
Pile elements (as shown in the
figure)
- Property: 9: Pile to Soil
interface
- Mesh Set: Pile Tip
- OK
03 Mesh Generation
Procedure
1
2
2
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1
- Show the solid segment for Raft
- Select it and right click on
mouse and select ‘Display
Mode > Line Only’
Mesh > Element > Parameters
- 1D tab
- Change Property
- Select: all the Pile interface
elements inside solid (as
shown in the figure)
- Property: 8: Pile to Raft
interface
- OK
03 Mesh Generation
Procedure
1
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The behavior of pile elements can be divided into a normal behavior and a tangential behavior. First, the normal behavior
between the pile and the surrounding ground is considered as fixed and rigid, whereas the tangential behavior is a nonlinear
elastic behavior. The nonlinear elastic behavior is divided into the yield force and the yield function assigned.
The graph bellow represents the relative displacement between the 2 bodies and the friction when yield force is defined. If the
relation is defined by a function, the relation between relative displacement and friction can be defined more precisely.
The Pile tip element works as solid-point interface that presents the relative behavior between the ground elements and pile
node. In the element coordinate system of the pile tip element regard the normal direction behavior toward the element as
rigid behavior just like a pile behavior. And, regard the tangent direction behavior as nonlinear elastic behavior.
To define the behavior, the material and property of a pile element can be entered based on test data, such as Load Test.
For more information about entering parameters of pile element, look up [User Manual] Ch4 (General Material) or Select F1
for [Online Manual].
03 Mesh Generation
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1
Show all mesh sets.
Static/Slope Analysis >
Boundary > Constraint
- Auto tab
- Boundary Set: Ground support
- Apply
- Show only the ‘Piles’ mesh set.
- Advanced tab
- Object Type: Node
- Select: all the nodes of Pile
elements (as shown in the
figure)
- DOF: Rz
- Boundary Set: Piles
- OK
04 Analysis Setting
Procedure
1
2
2
Axial rotation constraints to
prevent the degree of freedom
errors for torsion of beam
elements
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1
Show all mesh sets.
Static/Slope Analysis > Load >
Self Weight
- Gz: -1
- Load Set: Self weight
- OK
04 Analysis Setting
Procedure
1
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1
Show only the ‘Excav#4-Raft’
mesh set.
Static/Slope Analysis > Load >
Pressure
- Face tab
- View Toolbar: Front
- Object Type: 3D Element Face
- Select: the highlighted area
(as shown in the figure)
- Direction Type: Normal
- P or P1: 200 kN/m2
- Load Set: Raft pressure
- OK
Static/Slope Analysis >
Boundary > Change Property
- General tab
- Select: all the Raft elements
(as shown in the figure)
- Property: 4: Raft
- Boundary Set: Change
Property-Raft
- OK
04 Analysis Setting
Procedure
1
2
2
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1
Show all mesh sets.
Static/Slope Analysis >
Construction Stage > Stage Set
- Add
- Stage Name: In-situ
- Select the highlighted mesh,
boundary and load sets. Drag and
drop them into Activated Data
from Set Data.
- Show Data: Activate
- Clear Displacement: Check on
- Save
04 Analysis Setting
Procedure
1
2
2
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1
- New
- Stage Name: Install Wall
- Select the highlighted mesh sets.
Drag and drop them into
Activated & Deactivated Data
from Set Data.
- Show Data: Activate
- Clear Displacement: Check on
- Save
04 Analysis Setting
Procedure
1
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1
- New
- Stage Name: Excav#1
- Select the highlighted mesh set.
Drag and drop it into Deactivated
Data from Set Data.
- Show Data: Activate
- Save
04 Analysis Setting
Procedure
1
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1
- New
- Stage Name: Excav#2
- Select the highlighted mesh set.
Drag and drop it into Deactivated
Data from Set Data.
- Show Data: Activate
- Save
04 Analysis Setting
Procedure
1
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1
- New
- Stage Name: Excav#3
- Select the highlighted mesh set.
Drag and drop it into Deactivated
Data from Set Data.
- Show Data: Activate
- Save
04 Analysis Setting
Procedure
1
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1
- New
- Stage Name: Excav#4
- Select the highlighted mesh set.
Drag and drop it into Deactivated
Data from Set Data.
- Show Data: Activate
- Save
04 Analysis Setting
Procedure
1
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1
- New
- Stage Name: Install Piles &
Raft
- Select the highlighted mesh and
boundary sets. Drag and drop
them into Activated Data from Set
Data.
- Show Data: Activate
- Save
04 Analysis Setting
Procedure
1
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1
- New
- Stage Name: Raft+Load
- Select the highlighted mesh,
boundary and load sets. Drag and
drop them into Activated Data
from Set Data.
- Show Data: Activate
- Save
04 Analysis Setting
Procedure
1
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1
Analysis > Analysis Case >
General
- Title: 3D Excavation and Piled-
Raft Foundation
- Solution Type: Construction
Stage
- Analysis Control
- Initial Stage for Stress Analysis:
Check on
- Initial Stage: 1:In-situ
- Apply K0 Condition: Check on
- OK
- Output Control
- Strain: Check on
- OK
Analysis > Analysis > Perform
- Analysis Case: Check on
- OK
04 Analysis Setting
Procedure
1
2
2
To plot the relative displacement
of element such as pile element
among the ground when
interfacial behavior occurs
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1
Raft Load > Displacement >
TOTAL TRANSLATION (V)
Result > General > Smooth:
Fringe
Result > General > Deform:
Undeformed
- Properties: Deform
Result > Show/Hide > Actual
Deformation
Result > Advanced > Probe
- Max/Min
05 Results
Procedure
1
2
2
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1
Advanced View Control: Clipping
Plane
- Define Plane
- X: 30m
- Add
- Y: 30m (Reverse)
- Close
- Always Show edges: Check off
- Plane Composite: Union
- Close
Raft Load > Displacement > TZ
TRANSLATION (V)
Result > Advanced > Cutting
Diag.
- Type: 2-Points Line
- Point 1: 0,30,0
- Point 2: 60,30,0
- Direction: (+)Z Dir.
- Reverse: Check on
- OK
05 Results
Procedure
1
2
2
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1
Raft Load > Beam Element
Forces > BENDING MOMENT Y
Result > General > No Results:
Exclude
Raft Load > Pile Force >
TANGENTIAL X
05 Results
Procedure
1
2
2
Tangential friction force between
pile and ground
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1
Raft Load > Shell Element
Forces > BENDING MOMENT
YY
Raft Load > Interface Stress >
TANGENTIAL Y
05 Results
Procedure
1
2
2
Friction force between wall and
ground
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Thank you!