seismic analysis for bridge foundation using time history10.1007/s40098-014-0110... · midas it...
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MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
midas GTS 2D Tutorial
MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
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
MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
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
MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
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
MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
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
MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
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
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MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
Procedure
03 Mesh > Auto Mesh > Planar Area
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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]
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MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
Procedure
03 Mesh > Auto Mesh > Planar Area
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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.
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1
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MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
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.
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Model > Element > Extract Element
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MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
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.
MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
Procedure From Main Menu, select
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.
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Model >Element > Create Ground Surface Spring
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MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
Procedure From Main Menu, select
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]
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Analysis > Analysis Case
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MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
Procedure From Main Menu, select
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
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MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
Procedure From Main Menu, select
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.
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Result > Vibration Mode Shape 1
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MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
Procedure
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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.
MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
Procedure From Main Menu, select
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.
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Model >Element > Create Surface Spring
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MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
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]
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Model > Load > Time History Data > Time History Load Set
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MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
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.
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Model > Load > Time History Data > Time History Load Set
1 1
MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
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]
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Model > Load > Time History Data > Time Forcing Functions
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MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
Procedure Generate the forcing functions
for ’Ofunato’ and ‘Artificial’
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Model > Load > Time History Data > Time Forcing Functions 1
1
MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
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.
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Model > Load > Time History Data > Ground Acceleration
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MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
Procedure From Main Menu, select
Analysis > Analysis Case
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]]
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Analysis > Analysis Case
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MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
Procedure Generate the 2 analysis cases for
‘Ofunato’ and ‘Artificial’ with
similar procedure.
14 1
Analysis > Analysis Case
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1 1
MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
Procedure From Main Menu, select
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
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2
MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
Procedure
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Result > Time History Result > Time History Graph
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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.
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MIDAS IT Co., Ltd. MIDAS IT Co., Ltd. Step
Seismic Analysis for Bridge Foundation using Time History
Procedure From Main Menu, select
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 .
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Result > Time History Result > Time History Plot
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