Seismic Analysis for Bridge Foundation using Time History10.1007/s40098-014-0110... · MIDAS IT...

MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step

Seismic Analysis for Bridge Foundation using Time History

midas GTS 2D Tutorial



Overview

• Perform ‘Eigenvalu Analysis’ after

generating elastic spring using

‘Create Surface Spring’

• Generate short, long and artificial

waves

• Check the deformation and structure

stability after performing time history

analysis with three seismic waves.

• Starting Files Required

GTS 2D Tutorials 36.gtb

※ When earthquake shakes, ground

vibration spreads from lower

basement rock to upper earth surface.

Ground vibration transmits to upper

structure, and characteristic of

earthquake vibration differs

remarkably according to dynamic

interaction between ground and

foundation structure. Vibration

characteristic of upper structure is

governed by ductility and vibration

characteristic of foundation structure

so that comprehensive examination of

ground, foundation, upper structure is

needed.

00 Seismic Analysis for Bridge Foundation using Time History

1

Embankment 2

Soft Rock

Clay

Weathered Rock

Abutment

Pile

Embankment 1



01 Material Property

Attribute)

2

Attribute Name(ID)

Type Material Name(ID) Property Name(ID) Mesh Set Name

Embankment(1) Plane Embankment(1) Embankment 1, 2

Clay(2) Plane Clay(2) Clay

Weathered Rock(3) Plane Weathered Rock(3) Weathered Rock

Soft Rock(4) Plane Soft Rock(4) Soft Rock

Abutment(5) Plane Abutment(5) Abutment

Steel Pipe Pile(6) Line Steel Pipe Pile(6) Steel Pipe Pile(6) Pile



01 Material)

3

ID 1 2 3 4 5

Name Embankment Clay Weathered

Rock Soft Rock Abutment

Model Type MC MC MC MC Elastic

Modulus of Elasticity(E)[tonf/m2] 4,000 850 15,000 30,000 232,000

Poisson’s Ratio(ν) 0.35 0.3 0.35 0.27 0.19

Unit Weight(Y) [tonf/m3] 1.8 1.7 2 2.4 2.5

Unit Weight(Saturated) [tonf/m3] 1.9 1.8 2.1 2.5 2.5

Cohesion(c)[tonf/m2] 1.5 5 20 45 -

Internal Friction Angle(Φ) 25 20 32.5 35 -

Damping Ratio 0.05 0.05 0.05 0.05 0.05

Ko 1 1 1 1 1

* MC: Mohr-Coulomb

Material Property



01

Structure

4

Material/ Property

Modulus of Elasticity(E)

[tonf/m2]

Poisson’s Ratio(ν)

Unit Weight(Y) [tonf/m3]

D [m]

tw [m]

Steel Pipe Pile 21,000,000 0.3 7.85 0.508 0.012

Material Property



Procedure File > Open

Double click

‘GTS 2D Tutorials 36.gtb’

In this tutorial, the material

properties are already defined.

(Model > Property > Attribute)

02 File > Open

2

1

5

3

1

3

2



Procedure

03 Mesh > Auto Mesh > Planar Area

6

3

2

1

4

5

6

7

From the Main Menu, select

Mesh > Auto Mesh > Planar

Area

Select the edges including pile

edges in abutment as shown

Enter ‘1’ in the Mesh Size

Select ‘Abutment’ from the

Attribute, Enter ‘Abutment’ in the

Mesh Set.

Click [Advanced Option]

Select ‘Triangle’ from the Type

Check off ‘Register Each Area

Independently’ option

Click [OK]

Click [Apply]

1

2

4

5

6

3

7 8

8



Procedure

03 Mesh > Auto Mesh > Planar Area

7

3

2

1

4

Select the edges including

‘Embankment 1’ parts.

Enter ‘1’ in the Mesh Size

Select ‘Embankment’ from the

Attribute and enter ‘Embankment

1’ in the Mesh Set

Click [Apply]

Repeatedly generate mesh of

‘Embankment’, ‘Clay’, ‘Weathered

Rock’, ‘Soft Rock’ layer. For

exacting stake element, select

stake edge to each ground layer to

generate mesh.

2

1

4

3



Procedure From Main Menu, select

Model > Element > Extract

Element

From Shape, select ‘Edge’

Select the 20 edges correlating ‘pile’

as shown

Select ‘Steel Pipe Pile’ from the

Attribute, Enter ‘Pile’ in the Mesh

Set.

Click [OK]

In case of selecting Edge, ’Fail to

get information from shape’ is

shown, because mesh is

generated without selecting inner

edge. In this case, remove ground

mesh then regenerate premises

inner edges are selected.

04

3

2

1

4

8

Model > Element > Extract Element

5

1

2

4

5

3



Procedure

05

9

Modulus of Subgrade Reaction (tonf/m3)

Embankment(Left) 4396.80

Embankment(Right) 11329.76

Clay 1432.90

Weathered Rock 31198.72

Soft Rock(Sides) 33047.24

Soft Rock(Bottom) 18324.93

Area(cm2)

Embankment(Left) 110101.57

Embankment(Right) 8822.06

Clay 35199.65

Weathered Rock 20100.68

Soft Rock(Sides) 109470.01

Soft Rock(Bottom) 527483.86

Modulus of Subgrade Reaction

Modulus of Vertical Subgrade Reaction

Modulus of Horizontal Subgrade Reaction

Where,

α : Estimated factor for Modulus of subgrade reaction (use between 2.0~4.0)

The ‘Create Ground Surface Spring’ feature can generate automatically for dynamic analysis. The modulus of subgade reaction is calculated by right equations in the ‘Create Ground Surface Spring’ feature.




Model > Element > Create

Ground Surface Spring

Select ‘4’ mesh sets including

‘Embankment 2’, ‘Clay’,

‘Weathered Rock’, ‘Soft Rock’

Enter ‘2’ as the α

Check off the ‘Fixed Bottom

Condition’

Click [OK]

By the ‘Create Ground Surface

Spring’, the elastic spring of every

node are generated considering the

effective area and material property

of each node.

06

3

2

1

10

Model >Element > Create Ground Surface Spring

4

5

1

2

3

4

5

2




Analysis > Analysis Case

Click [Add]

Enter ‘Eigenvalue’ in the Name,

select ‘Eigenvalue’ from the

Analysis Type

Click [ ]Analysis Control

Enter ‘30’ in the Number of

Frequencies

Click [OK]

Click [OK]

07

3

2

1

4

5


11

6

7

3

5

2

1

4

7 6




Analysis > Solve

Confirm the checking on the

‘Eigenvalue Analysis’

Click [OK]

Information generated in the

process of analysis is displayed on

Output Warming. Especially in the

case of warming generated,

analysis results may be abnormal.

So it should be noticed.

Analysis results are saved as .TA

format. Information about analysis

is saved to .OUT file in same folder

with save file as Text file format.

08 1

Analysis > Solve

12

3

2

3

1

2




Results > Vibration Mode

Shape

From Active Dialog, check the

‘EIGN : Eigenvalue’ from the

Analyss Case/Combination,

click [OK]

Check period of 2nd mode and 4th

mode which have the biggest mass

participation by mode in X direction.

Check ‘1.7606Cycle/sec’ and

‘2.9780Cycle/sec’ of Frequency.

In 2 dimensional seismic analysis,

shake direction is in X direction. In

this case, mass participation in X

direction should be referred to

reflect mass participation in each

mode. Mode period to the biggest

two mass participation should be

reflected to analysis.

09 1

13

3

2

Result > Vibration Mode Shape 1

2

3

2



Procedure

10

14

cp(tonf·sec/m3) cs(tonf·sec/m3)

Embankment 34.32 16.48

Clay 14.08 7.52

Weathered Rock 70.05 33.65

Soft Rock 95.76 53.75

Damping Constant

For P wave:

For S wave:

Where,

A: Cross-sectional area (㎡) W: Unit weight (kN/㎥) G: Shear modulus (kN/㎡) E: Modulus of elasticity (kN/㎡) λ: Volumetric modulus of elasticity (kN/㎡) ν: Poisson’s ratio

The right equations are for damping

constant calculation.




Model > Element > Create

Surface Spring

Select ‘Element Edge’ from Type of

Object, enter ‘1’ in the ‘Element

Width

Check on the ‘Damping

Constant/Area’

Cx > enter ‘34.32’, Cy > enter

‘16.48’

As Sub-Set > enter ‘Damping’ in

the, Add to > ‘Embankment 2’

Click [Apply]

Generate spring for layer of clay,

weathered rock, soft rock

repeatedly. In case of Soft Rock,

spring is generated to basement

also. Damper for basement is

entered reversely, value of Cs to

Cx, Cp to Cy.

11

3

2

1

15

Model >Element > Create Surface Spring

4

5

6

1

2

4

5

6

3



Procedure From Main Menu, select Model > Load > Time History Data > Time History Load Set

Click [Add]

Load Set Name >’Hachinohe’, Analysis Method > select ‘Direct Integration

End Time > enter ’25’, Time Increment > enter ’0.01’,

Step Number Increment for

Output > enter ‘1’

Damping > select ‘Calculate from Modal Damping’

Frequency > enter the 1st, 2nd order calculated by eigenvalue analysis

Damping Ratio > enter ’0.05’ respectively

Click [Apply]

12

3

2

1

4

Model > Load > Time History Data > Time History Load Set

16

5

6

7

8

1

2

4

5

6

3

8

7

3



Procedure Generate the load sets

for ’Ofunato’and ’Artificial’.

End Time is finish time of analysis.

Time Increment means analysis

time interval. Results produced at

the interval of Number of Output

Steps multiplied by Time Increment.

For example, if Time Increment is

0.01sec and Step Number

Increment for Output is 10, analysis

results are produced at every

0.1sec.

12 1

17

Model > Load > Time History Data > Time History Load Set

1 1



Procedure Select Model > Load > Time

History Data > Time Forcing

Function

Click [Add Time Function]

Function Name > ’Hachinohe’

Time Function Data Type > check

‘Normalized Accel.’

In Excel file, copy and paste the 1st

wave data into dialog window.

Click [OK]

13

3

2

1

4

Model > Load > Time History Data > Time Forcing Functions

18

5

6

1

2

4

5

6

3



Procedure Generate the forcing functions

for ’Ofunato’ and ‘Artificial’

13 1

19

Model > Load > Time History Data > Time Forcing Functions 1

1



Procedure Select Model > Load > Time

History Data > Ground

Acceleration

Time History Load Set > select

‘Hachinohe’

Time Forcing Function > check on

the ‘X Direction’, Function

Name > select ‘Hachinohe’

Click [Add]

Generate Ground Acceleration to

Ofunato and Artificial repeatedly.

13

2

Model > Load > Time History Data > Ground Acceleration

20

4

3

2

1

3

1

1





Click [Add]

Name > enter ‘Hachinohe’,

Analysis Type > select ‘Time

History(Linear)’

Analysis Model > select ‘Empty’ on both Initial Element and Initial

Boundary

From Set Tree, Drag & Drop

‘Abutment’, ‘Clay’,

‘Embankment 1,2’, ‘Pile’, ‘Soft

Rock’, ‘Weathered Rock’,

‘Damping’ and ‘Hachinohe’ into

the Activated

Click [OK]]

14

3

2

1

4

5


21

6

5

2

1

4

6

3



Procedure Generate the 2 analysis cases for

‘Ofunato’ and ‘Artificial’ with

similar procedure.

14 1


22

1 1




Analysis > Solve

Check off the ‘Eigenvalue’

Click [OK]

Information generated in the

process of analysis is displayed on

Output Warming. Especially in the

case of warming generated,

analysis results may be abnormal.

So it should be noticed.

Information about analysis is saved

to .OUT file in same folder with

save file as Text file format.

15 1

Analysis > Solve

23

3

2

3

1

2



Procedure

16

3

2

1

Result > Time History Result > Time History Graph

24

From Main Menu, select

Result > Time History Result >

Time History Graph

Click [Define/Modify Function]

Function Data > enter ‘X dis’, select the node as shown

Components > select ‘DX’,

Analysis Case > ’Hachinohe’

Click [Add]

Function List > check on ‘X dis’,

click [Add from List]

Y Axis > check on ‘X dis’,

X Axis > check ‘Time’

Click [Apply]

The displacement of X direction and

maximum value with time can be

checked.

4

5

6

7

1

4

5

6

3

7

2

3

6

7

8

8




Result > Time History

Result > Time History Plot

Analysis Set > Check ’Hachinohe’

Result > check ‘Displacement’

and ‘DX’

Click [Apply]

Not only displacement but also

ground stress or member stress,

displacement can be checked

identically by changing Result item .

17 1

25

Result > Time History Result > Time History Plot

2

3

1

2

3

4

4

Seismic Analysis for Bridge Foundation using Time History10.1007/s40098-014-0110... · MIDAS IT...

Documents

Transcript of Seismic Analysis for Bridge Foundation using Time History10.1007/s40098-014-0110... · MIDAS IT...