Basic Tutorial 6_2D Open Cut Tunnel

8/9/2019 Basic Tutorial 6_2D Open Cut Tunnel

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BasicTutorial 6

2 Dimensional Analysis of Open-cut Tunnel


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GTS Basic Tutorial 6.

- 2 Dimensional Analysis of Open-cut Tunnel

Contents

Starting GTS 1

Preview 2

Ground Reaction Coefficients 3

Create Analysis Data 4

Attribute 4

Create 2D Geometry 6

Create 2D Element Mesh 8

Alignment of Element Coordinates 10

Analysis 12

Boundary Condition 12

Load 14

Load Combination 18

Analysis Case 20

Solve 22

Post Processing, Result Display and Control 23

Displacement 23

Reaction 25

Axial Force 27

Moment 28


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GTS Basic Tutorial 6

1



In this tutorial, the analysis of two dimensional open-cut tunnel is introduced from modeling

to result display.

The open-cut analysis model is to define the tunnel structure, and its Attribute definition,

ground spring specification, and load combination are very important in this analysis. In this

example, useful load and boundary definition functions such as Line Beam Load, Surface

Spring Supports, and Create Load Set with Combined Load Set are explained. In addition,

compression-only elastic link, we model ground spring and perform the boundary nonlinear

analysis.

Starting GTS

Start the program.

1. Run GTS.

2. Start a new project by clicking F ile > Newbutton.

3. Proj ect Setti ngdialog box will appear.

4. Enter Basic Tutorial 6 inProject Titl e.

5. Select 2D in Model Type.

6. Select X-Y Plane in Analysis Constraint.

7. Make sure that Y option is selectedin Gravity Di rection.

8. Use default value for rest of the inputs.

9. Click button.

10. In the Main Menu, select View > Display Option....

11. In General Tab, change Mesh > Node Displayto True.

12. Click button.

13. Click button to close the Display Option dialog box.


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2

Preview

This tutorial has been simplified for training purpose only, and its detail process may be

different from actual practice. The followings are the basic parameters used in this tutorial.

Tunnel type : Open-cut Tunnel

Soil height : 3 m

Soil parameters : Unit weight, s= 2.0 tonf/m3

Friction angle, = 30

Coefficient of Soil Pressure, K0= 1sin= 0.5

Material property: Characteristic strength of concrete, fck= 270 kgf/cm2

Unit Weight, = 2.5 tonf/m3

Modulus of Elasticity, Ec = 2.77x106tonf/m3

Tunnel shape : 3 Point Tunnel (R1 = 4.665m, R2 = 3.0m, A1 = 60, A2 = 60)

The tunnel section and static soil pressure is shown in the following figure. On the tunnel

structure, self-weight, vertical soil pressure, and horizontal soil pressure are applied.

60

R1=4.665m

R2=3.000m

3.

000

P1=3.0 tonf/

P2=8.3325 tonf/

(0,0,5.3325)

P2=8.3325 tonf/

P1=3.0 tonf/

(-4.040009,0,3)

(-4.040009,0,0) (0,0,0)

120

(4.040009,0,0)

(4.040009,0,3)

0.400m

GTS Basic Tutorial 6 - 1

For open-cut tunnel, the

structure receives static

pressure or active

pressure. However, for

excavating tunnel, the

structure receives

relaxation soil pressure.


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3

Generate the model by assigning Beam Element to the Tunnel Wall and Compression-only

Elastic Link to the Ground Springs.


Ground Reaction Coefficients

Ground reaction coefficient is determined using Korean Road Traffic Safety Authoritys

design code as follows.

1 11 1400 46.6670

30 30k Ev o kgf/cm

3

800 1400 1058.3B Av v cm

0E 28N = 2850 = 1400 kgf/cm2

3 3

1058.3

4 446.667030 30

Bvk kv v

= 3.224 kgf/cm3= 3224 tonf/m3

Tunnel Wall : Beam Element

Ground Springs:

Comp.-only Elastic Link

An open-cut tunnel

required ground spring

only at the bottom.


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4

Create Analysis Data

Attribute

Generate Attributes.

1. Select Model > Property > Attr ibutein the Main Menu.

2. Click to the right of button in the Attributedialog box.

3. Select Line.

4. Make sure that AttributeIDis 1in the Add/Modify Plane Attributedialog box.

5. Enter Liningin Name.

6. Select Beamin Element Type.7. In order to create Material, click button to the right of Material.

Define material and section properties of the Beam Type Attribute.

8. Make sure that Material I Dis 1in theAdd/Modify Structural Materialdialog box.

9. Enter C270 in Name.

10. Click Colorbutton to define the Material with an appropriate color.

11. Enter 2.77e6in Modulus of El asticity (E)in Materi al Parameters.

12. Enter 0.18 inPoissons Ratio (

)in Materi al Parameters.

13. Enter 2.5inUnit Weight (

)in Materi al Parameters.

14. Enter 1e-5inThermal Coeff icient(

)in Thermal Parameter.

15. Click button.


16. Make sure that Materialis set to C270in the Add/Modify Line Attributedialog box.

17. In order to create Property, click button to the right of Property.

18. Make sure that Property I Dis 1in theAdd/Modify Propertydialog box.

19. Enter Liningin Name.

20. Click Colorbutton to define the Property with an appropriate color.

21. Select Beamin Type.

Beam or Truss

Elements is a Line-type

Attribute.


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22. Check on Sectional L ibraryto generate a quadrangular section in the mountain.

23. Select Solid Rectangleto define the section.

24. Enter 0.4in H.

25. Enter 1in B.

26. Click button.

27. Click button in the Add/Modify Propertydialog box.

28. Click button Add/Modify Line Attribute dialog box.

29. Make sure that Lining has been generated as Attributein the Attributedialog box.

30. Click button.


5


Sectional Library

provides various types

of sections such as

Solid Rectangle, Solid

Round, and Pipe.


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6

Create 2D Geometry

We will generate the Tunnel shape for analysis, using the Tunnel Sectionin GTS.

1. Select Geometry > Cur ve > Create on WP > Tunnel (Wire)in the Main Menu.

2. Make sure that 3 Center Circleis selectedin Tunnel Type.

3. Make sure that Fullis selectedin Section Type.

4. Input 4.665in R1and press Enter on the keyboard.

5. Similarly, input 60 in A1, 3in R2and 60in A2.

6. Check off Make Wire option.

7. Click button.

8. Select Zoom All in the View Pointtoolbar.



GTS provides various

tunnel section in a

template dialog box.


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9. Make sure that 4 tunnel curves are added as Tunnel Sectionin Geometry > Curvein

the Pre-Works Tree.



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Create 2D Element Mesh

Using Auto-Mesh Edge function, create 2D Beam elements on previously created 2D CurveGeometry.

We will first create the Beam Elements of the tunnel side walls.

1. SelectMesh > Auto-Mesh > Edgein the Main Menu.

2. In button, select the edges defining the tunnel sides,

Edge A andC, as shown in the figure GTS Basic Tutorial 6-10.

3. Select Number of Divisionsin the Seeding Method.

4. Enter 8in Number of Divisions.

5. Select 1:Liningin Attribute I D.

6. Delete Auto-Mesh (Edge)in Mesh Setand enter Wall.

7. Click Previewbutton to confirm that the number of divisions in the Edges have

been correctly generated.

8. Click button.


Similarly, we will create Beam Elements for the tunnel crown and bottom slab.

9. In button, select the edge defining the tunnel crown,

Edge B, as shown in the figure GTS Basic Tutorial 6-10.




13. Delete Wallin Mesh Setand enter Crown

14. Click Preview button to confirm that the number of divisions in the Edge have


15. Click button.

16. In button, select the edge defining the tunnel bottom

slab, Edge D, as shown in the figure GTS Basic Tutorial 6-10.


B

CA

D

Refer to Online Manual

for other seeding

method.

In order to increase

numerical accuracy, it is

recommend to keep

each neighboring

elements within 15

degrees.


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20. Delete Crownin Mesh Setand enter Slab

21. Click Preview button to confirm that the number of divisions in the Edge have


22. Click button.

23. To confirm that the Mesh Elements have been correctly generated, select Properti es >

Property > L inein the Pre-Works Tree, and invoke the Context Menu by right-clicking

the mouse.

24. Select Show All.

25. Select Properti es > Property > Linein the Pre-Works Tree once again, and invoke the

Context Menu by right-clicking the mouse.

26. Select Hide All.


Defined section

property is shown in

three dimensional.


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10

Alignment of Element Coordinates

Member force of beam elements is outputted based on the element local axis. Since theelement local axis is given by its generating sequence and direction, it may not aligned

uniformly. Lets check the element local axis of generated elements.

1. Select Wall, Crown, andSlabin Mesh > M esh Set in the Works Tree and invoke

the Context Menu by right-clicking the mouse. All the Mesh Sets can be selected

together by using the Shift key

2. Select Display > El ement CSysin the Context Menu.

3. Select the Wall, Crown, andSlab Mesh Sets, similar to Step 1, and invoke the

Context Menu by right-clicking the mouse.

4. Select Display > Display Element I Din the Context Menu.


As shown in the above figure, some elements (EL. 5, 6, 7, 8, 9, 10, 11, 12) are not aligned

together. Modify those elements.

5. SelectModel > Element > Change Parameterin the Main Menu.

6. Check on Orientation.

7. Select 1D Element (O)in the Selection Filter.

8. In button, select Elements 5, 6, 7, 8, 9, 10, 11, and 12

in Work Window.

9. Check onBeta Angle and select180 Deg.

10. Click button.

11. Select I sometri c in the View Point toolbar to confirm the alignment of the

element coordinates.

In View > Display

Option, user can

specify its size and

color.


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12. Repeat Steps 1~3 to hide all the Element IDs and the Element Coordinate System.

13. Select Front in the View Point toolbar.


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Analysis

Boundary Condition

Surface Spring is applied to the analysis model as its boundary condition. By entering the

ground reaction coefficient on selected nodes, it computes the distance between selected

nodes and applies the spring coefficient automatically. Since the bottom support of tunnel

cannot take any tensile force, the ground spring is modeled with Compression-only

elements. In addition a boundary condition at the crown to restrain any movement along

the X-axis.

1. SelectModel > Element > Create Surface Spring in the Main Menu.

2. Select Frameoption in Typein Object.

3. Enter 1in Element Width in Object.

4. Click button and drag the mouse in the Work Window and

select the 16 Elements defining the bottom slab of the tunnel, as shown in the figure

GTS Basic Tutorial 6 - 14.


5. Select Elastic Link option.

6. Click on button to the right of BC Set to create a Boundary Set.

7. Enter Ground Springin Namein BC Setdialog box, and click button.

8. Click button.

9. Select GCS-z(-)inDirection.

10. Enter 3224in Modulus of Subgrade Reaction.

11. Enter 1in Length of El astic Li nk.

12. Check on Comp.-onlyoption.

13. Enter100inMax. Number of Attri bute.

14. Click button.

15. Select Model > Boundary > Supports.

16. Select one node at the top of the crown.

17. Restrain Ux and Apply. See Figure below.

Elastic Link is used to

consider nonlinear

boundary elements

such as Compression-

only or Tension-only.

Enter the number of

spring coefficient to

calculate. If 1 is

entered, it inputs a

single value for all

nodes although the

distances are varied.

Since it is 2D model,

unit length, 1m, is

entered

Length of Elastic Link

does not affect on

analysis result.


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Load

We will define the loading conditions for the model. 3 loading cases are defined selfweight, horizontal soil pressure, and vertical soil pressure. We will first input the self weight.

1. SelectModel > Load > Self Weight in the Main Menu.

2. Enter Self Weightin Load Set.

3. Enter -1in Yin Self Weight Factor.

4. Click button.

We will next input the horizontal soil pressure. The horizontal pressure diagram and

values are shown in the figure GTS Basic Tutorial 6

1. The Li ne Beam Loadfunction is

used to input the trapezoidal horizontal soil pressure.

5. Select Model > Load > Line Beam Load in the Main Menu.

6. Enter Horizontal Soil Pressurein Load Set.

7. Make sure thatAddoption is selected in Mode.

8. Select Selected Elementoption in Element Selection.

9. In button, select the point defined by Point 1, as

shown in the figure GTS Basic Tutorial 6 - 16.

10. In button, select Point 2.


11. Click button.

12. In button, select the 18 Elements defined in Area A, as

shown in the figure, GTS Basic Tutorial 6 - 16.

13. Make sure that Forceand Distributedoptions are checked on.

14. Select Global Xin Direction.

15. Make sure that Yesoption is checked on in Projection.

2

3

A B


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16. Make sure that Fractionoption is checked on in Value.

17. Enter0, 8.3325, 1, and3inx1, w1, x2, and w2, respectively.

18. Click Preview button to confirm that the horizontal soil pressure has been

correctly generated.

19. Click button.


Similarly, we will apply the horizontal soil pressure on the right side of the tunnel walls.


shown in the figure GTS Basic Tutorial 6 - 16.21. In button, select Point 2.

22. Click button.

23. In button, select the 18 Elements defined in Area B, as


24. Enter0,-8.3325, 1, and-3inx1, w1, x2, and w2, respectively.

25. Click Preview button to confirm that the horizontal soil pressure has been

correctly generated.

26. Click button.

w1 is the load value at

the first node, and w2

is the load value at the

second node. Length

between two nodes is

applied using linear

interpolation.


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We will input the vertical soil pressure using Line Beam Load.

It changes its value by height.

Soil cover height = 3m

Depth to the far end = 6.8325 m

Unit weight = 2.0 tonf/m3

Applying Load = 13.665 tonf/ m3to 6.0 tonf/ m3.


27. SelectModel > Load > Line Beam Loadin the Main Menu.

28. Enter Vertical Soil Pressurein Load Set.29. Select Selected Elementoption in Element Selection.




32. Click button.

33. In button, select the 14 Elements defined in Area A, as


34. Make sure that Forceand Distributedoptions are checked on.

35. Select Global Yin Direction.

36. Make sure that Yesoption is checked on in Projection.

37. Make sure that Fractionoption is checked on in Value.

38. Enter0, -13.665, 1, and-6inx1, w1, x2, and w2, respectively.

39. Click Previewbutton to confirm that the vertical soil pressure has been correctly

generated.

40. Click button.

2

; Node 5

3 ; Node 4

A B


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Similarly, we will apply the vertical soil pressure on the right side of the tunnel walls.




43. Click button.

44. In button, select the 14 Elements defined in Area B, as


45. Enter0, -13.665, 1, and-6inx1, w1, x2, and w2, respectively.

46. Click Previewbutton to confirm that the vertical soil pressure has been correctly

generated.

47. Click button.


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Load Combination

Linear static load combination cannot yield correct result in a model which is solved for theboundary nonlinear analysis using elastic Links with compression-only function. Therefore,

each load set must be combined before analysis to obtain correct combination result. Create

Load Set with Combined Load Set function treats the combination of load sets as a static

load set. Note:

The following combinations will be used to design sections.

LCB 1 : 1.54 Self Weight + 1.8 Horizontal Soil Pressure + 1.4 Vertical Soil Pressure

LCB 2 : 1.54 Self Weight + 0.9 Horizontal Soil Pressure + 1.4 Vertical Soil Pressure

We will create the first load combination.

1. Select Model > Load > Create Load Set with CombinedLoad Setin the Main Menu.

2. Enter LCB 1in Name.

3. Select Self Weightin Load Set in Combined Load Set.

4. Enter 1.54in Factorin Combined Load Set.

5. Select Horizontal Soil Pressurein Load Set in Combined Load Set.


7. Select Vertical Soil Pressurein Load Set in Combined Load Set.

8. Enter 1.4in Factorin Combined Load Set.9. Click button.

10. Confirm that Load Set [ LCB 1 ]is generated in Load in the Pre-Works Tree.



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We will create the second load combination.

11. SelectModel > Load > Create Load Set with Combined Load Setin the Main Menu.

12. Enter LCB 2in Name.

13. Select Self Weightin Load Set in Combined Load Set.


15. Select Horizontal Soil Pressurein Load Set in Combined Load Set.


17. Select Vertical Soil Pressurein Load Set in Combined Load Set.


19. Click button.

20. Confirm that Load Set [ LCB 2 ]is generated in Load in the Pre-Works Tree.

21. Select Load Set [ LCB 1 ]and Load Set [ LCB 2 ]in Load in the Pre-Works Tree,by right-clicking the mouse.

22. Select Hide All.



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Analysis Case

We will generate an Analysis Casefor performing analysis.

1. Select Analysis > Analysis Casein the Main Menu.

2. Click button.


3. Enter Basic Tutorial 6in Name.

4. Enter 2D Tunnel Analysisin Description.

5. Select Linear Staticin Analysis Type.

6. Select Element > Wall, Crown, Slab, and Surface Spring in the Set Tree inAdd or Modify I nitial M odel.

7. Drag-and drop the selected Mesh Sets into Activated.

8. Select Load >LCB 1&LCB 2and Boundary >Ground Springin the Set Tree

in Add or Modify Ini tial M odel.

9. Drag-and drop the selected Load Sets and Boundary Set into Activated.

10. Check on Solve Each load Set I ndependently.

11. Click button.

12. Click button in the Analysis Casedialog box.

Since single Load Set

may cause convergence

problem in the boundary

nonlinear analysis, we

will activate combined

load sets only


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Solve

We will perform analysis.

1. Select Analysis > Solve in the Main Menu.

2. Click in the Solver Managerdialog box

All the messages during the analysis will be shown in the Output Window. Especially, one

needs to be very cautious about warning messages, because these messages indicate that the

analysis results may not be correct. The model is automatically saved before the analysis.

The result is saved as binary file(*.TA*) in the same folder as the model. The detail analysis

information is also saved in a text file(*.OUT).


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Post Processing, Result Display and Control

Most of the Post-Processing work in GTS can be accomplished by using the varioustoolbars, for instance the Post Data Toolbar as shown below. The Property Window can be

used for selecting and defining the corresponding items required for detailed Post-

Processing.

- Post Data Toolbar -

Displacement

Check the Displacementsfor each load combination.

1. Select the Post-Workstab in the Works Tree.

2. Double-click ST : Basic Tutorial 6 > LCB 1 > Di splacement >DY(V)in the Works

Tree.

3. Select Post Data tab in the Tabbed Toolbar.

4. Make sure that LCB 1is selected in the Output Setin the Post Datatoolbar.

5. Click Sensitivebutton in the Post Datatoolbar.

6. Click Mesh Shapebutton.

7. Select Deformed + Undeformed.

8. Make sure that DY(V)is selected in the DeformationData in the Post Datatoolbar.

9. Confirm the variation in deformation and its direction.

10. Select Deformationin the Property Window.

11. Make sure that Real Displacement is defined as False. In case of selecting True

this option generates a display output that shows the actual variation of displacementvalues.

12. Click button in the Property Window.

13. Check the displacements for load combination LCB 2 by selecting LCB 2 in

Output Set in lieu of LCB 1. Click button to

display the displacement DY(V)for LCB 2.

Sensitive option enables

to display modified

output result data

immediately after Output

data control on the

screen.

Plot TypeMesh ShapeData Filter

Output Set Deformation DataContour Data


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Reaction

We will display the Reactionsfor each load combination.

1. Double-click ST : Basic Tutorial 6 > LCB 1 > Reaction >FYin the Works Tree.

2. Select Post Datatab in the Tabbed Toolbar.

3. Make sure that LCB 1is selected in the Output Setin the Post Datatoolbar.

4. Click Mesh Shapebutton.

5. Select Undeformed.

6. Make sure that FYis selected in the Contour Data.

7. Check the reactions for load combination LCB 2 by selecting LCB 2 in


display the reaction FYfor LCB 2.



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Check the Forcesin the Elastic Linksfor each load combination, by generating the results

in a Table format.

8. SelectResult > Result Tables > Elastic Link Force in the Main Menu.

9. Select LCB 1 andLCB 2inStage/Step.

10. Selectiandjin Part Number.

11. Click button.



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Moment

Check the Bending Momentsfor each load combination.

1. Double-clickST : Basic Tutori al 6 > LCB 1 > 1D Element Forces >LO-Beam My

in the Works Tree.

2. Select Post Data tab in the Tabbed Toolbar.

3. Make sure that LCB 1 is selected in Output Set in the

Post Datatoolbar.

4. Make sure that LO-Beam Myis selectedin the Contour Data.

5. Display the bending moment diagram.

6. Check the bending moments for load combination LCB 2 by selecting LCB 2 in


display the bending moment LO-Beam Myfor LCB 2.



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Check the Forcesin the link elements for each load combination, by generating the results

in a Table format.

12. Selectfrom 1D Element Forces Link Fx and call the context menu by right clicking on

the Link Fx label.

13. Click button.


Documents

Basic Tutorial 6_2D Open Cut Tunnel